ER
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EPA
United States
Environmental Protection
Agency
EPA/600/D-11/001
February 2011
Draft Plan to Study the Potential
Impacts of Hydraulic Fracturing on
Drinking Water Resources
Office of Research and Development
U.S. Environmental Protection Agency
Washington, D.C.
February?, 2011
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This document is distributed solely for peer review under applicable information quality guidelines.
It has not been formally disseminated by EPA. It does not represent and should not be
construed to represent any Agency determination or policy. Mention of trade names or commercial
products does not constitute endorsement or recommendation for use.
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TABLE OF CONTENTS
List of Figures v
List of Tables v
List of Acronyms and Abbreviations vi
Executive Summary vii
1 Introduction and Purpose of Study 1
2 Process for Study Plan Development 2
2.1 Initial Science Advisory Board Review of the Study Plan Scope 2
2.2 Stakeholder Input 3
2.3 Research Prioritization 4
2.4 Next Steps 5
2.5 Interagency Cooperation 5
2.6 Quality Assurance 6
3 Overview of Unconventional Natural Gas Production 6
3.1 Site Selection and Preparation 10
3.2 Well Construction and Development 11
3.3 Hydraulic Fracturing 12
3.4 Well Production 13
3.5 Regulatory Framework 13
4 The Hydraulic Fracturing Water Lifecycle 13
5 Approach 15
5.1 Case Studies 15
5.2 Scenario Evaluation 16
5.3 Tools 16
6 Proposed Research 17
6.1 Water Acquisition: How might large volume water withdrawals from ground and
surface water impact drinking water resources? 19
6.1.1 Background 19
6.1.2 What are the impacts on water availability? 20
6.1.3 What are the impacts on water quality? 21
6.1.4 Proposed Research Activities—Water Acquisition 21
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6.1.4.1 Water Availability: Analysis of Existing Data, Prospective Case Studies, and
Scenario Evaluation 21
6.1.4.2 Water Quality: Analysis of Existing Data and Prospective Case Studies 22
6.1.5 Potential Research Outcomes 23
6.2 Chemical Mixing: What are the possible impacts of releases of hydraulic fracturing
fluids on drinking water resources? 23
6.2.1 Background 23
6.2.2 What is the composition of hydraulic fracturing fluids and what are the toxic
effects of these constituents? 25
6.2.3 What factors may influence the likelihood of contamination of drinking
water resources? 25
6.2.4 How effective are mitigation approaches in reducing impacts to drinking
water resources? 25
6.2.5 Proposed Research Activities—Chemical Mixing 25
6.2.5.1 Chemical Identity and Toxicity: Analysis of Existing Data 25
6.2.5.2 Hydraulic Fracturing Fluid Release: Analysis of Existing Data and Case Studies 26
6.2.6 Potential Research Outcomes 27
6.3 Well Injection: What are the possible impacts of the injection and fracturing process
on drinking water resources? 27
6.3.1 Background 27
6.3.1.1 Well Design and Construction 27
6.3.1.2 Injection of Hydraulic Fracturing Fluid 29
6.3.1.3 Naturally Occurring Substances 30
6.3.2 How effective are well construction practices at containing gases and fluids
before, during, and after fracturing? 30
6.3.3 What are the potential impacts of pre-existing man-made or natural
pathways/features on contaminant transport? 31
6.3.4 What chemical/physical/biological processes could impact the fate and transport of
substances in the subsurface? 32
6.3.5 What are the toxic effects of naturally occurring substances? 32
6.3.6 Proposed Research Activities—Well Injection 32
6.3.6.1 Well Integrity: Analysis of Existing Data, Case Studies, and Scenario Evaluation 32
6.3.6.2 Impacts of Natural and Man-made Pathways: Case Studies and
Scenario Evaluation 34
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6.3.6.3 Physical/Chemical/Biological Processes Relevant to Hydraulic Fracturing:
Laboratory Studies 35
6.3.7 Potential Research Outcomes 35
6.4 Flowback and Produced Water: What are the possible impacts of releases of flowback
and produced water on drinking water resources? 35
6.4.1 Background 35
6.4.2 What is the composition and variability of flowback and produced water and what
are the toxic effects of these constituents? 37
6.4.3 What factors may influence the likelihood of contamination of drinking
water resources? 37
6.4.4 How effective are mitigation approaches in reducing impacts to drinking
water resources? 38
6.4.5 Proposed Research Activities—Flowback and Produced Water 38
6.4.5.1 Composition and Variability of Flowback and Produced Water: Analysis of Existing
Data and Prospective Case Studies 38
6.4.5.2 Flowback and Produced Water Release: Analysis of Existing Data, Retrospective
Case Studies, and Scenario Evaluations 39
6.4.5.3 Flowback and Produced Water Management: Prospective Case Studies 39
6.4.6 Potential Research Outcomes 39
6.5 Wastewater Treatment and Waste Disposal: What are the possible impacts of
inadequate treatment of hydraulic fracturing wastewaters on drinking water resources? 40
6.5.1 Background 40
6.5.2 How effective are treatment and disposal methods? 41
6.5.3 Proposed Research Activities—Wastewater Treatment and Waste Disposal 42
6.5.3.1 Effectiveness of Current Treatment Methods: Analysis of Existing Data, Laboratory
Studies, and Prospective Case Studies 42
6.5.4 Potential Research Outcomes 42
7 Case Studies 42
7.1 Case Study Selection 42
7.2 Retrospective Case Studies 45
7.3 Prospective Case Studies 46
8 Characterization of Toxicity and Human Health Effects 47
9 Environmental Justice 49
10 Summary 49
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11 Areas of Concern Outside the Scope of This Study 54
11.1 Routine Disposal of Hydraulic Fracturing Wastewaters in Class II Underground
Injection Wells 55
11.2 Air Quality 55
11.3 Terrestrial and Aquatic Ecosystem Impacts 55
11.4 Seismic Risks 56
11.5 Public Safety Concerns 56
11.6 Occupational Risks 56
11.7 Economic Impacts 57
References 58
Appendix A: Proposed Research Summary 70
Appendix B: Stakeholder Comments 77
Appendix C: Information Request 80
Appendix D: Chemicals Identified in Hydraulic Fracturing Fluid and Flowback/Produced Water 83
Appendix E: Assessing Mechanical Integrity 99
Appendix F: Stakeholder-Nominated Case Studies 102
Appendix G: Field Sampling and Analytical Methods Ill
Appendix H: Modeling 119
Glossary 123
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LIST OF FIGURES
Figure 1. Fundamental research questions posed for each stage of the hydraulic fracturing
water lifecycle ix
Figure 2. Natural gas production in the United States 7
Figure 3. Shale gas plays in the contiguous United States 8
Figure 4. Coalbed methane deposits in the contiguous United States 9
Figure 5. Major tight gas plays in the contiguous United States 10
Figure 6a. Illustration of horizontal well showing the water lifecycle in hydraulic fracturing 11
Figure 6b. Illustration of a vertical where hydraulic fracturing occurs near an underground source
of drinking water 12
Figure 7. Water use in hydraulic fracturing 14
Figure 8. Well construction 28
Figure 9a. Summary of research projects proposed for the first three stages of the hydraulic
fracturing water lifecycle 51
Figure 9b. Summary of research projects proposed for the last two stages of the hydraulic
fracturing water lifecycle 52
LIST OF TABLES
Table 1. Relationship between case studies and scenario evaluations 15
Table 2. Hydraulic fracturing research questions 18
Table 3. Comparison of estimated water needs for hydraulic fracturing in different shale plays 19
Table 4. An example of the volumetric composition of hydraulic fracturing fluid 24
Table 5. Naturally occurring substances that may be found in gas-containing formations 30
Table 6. Decision criteria for selecting hydraulic fracturing sites for case studies 43
Table 7. Retrospective case study finalists 44
Table 8. Approach for conducting retrospective case studies 45
Table 9. Approach for conducting prospective case studies 47
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LIST OF ACRONYMS AND ABBREVIATIONS
AOE area of evaluation
API American Petroleum Institute
DBP disinfection byproducts
DOE United States Department of Energy
EIA United States Energy Information Administration
EPA United States Environmental Protection Agency
g/mile gram per mile
GIS geospatial information systems
GWPC Ground Water Protection Council
IOGCC Interstate Oil and Gas Compact Commission
mcf/d thousand cubic feet per day
mmcf/d million cubic feet per day
NETL National Energy Technology Laboratory
NGO non-governmental organization
NIOSH National Institute for Occupational Safety and Health
NPS National Park Service
NYS dSGEIS New York State Draft Supplemental Generic Environmental Impact Statement
ORD Office of Research and Development
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
STAR Science To Achieve Results
TDS total dissolved solids
UIC underground injection control
U.S. United States
USAGE United States Army Corps of Engineers
USDW underground source of drinking water
USGS United States Geological Survey
VOC volatile organic compound
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EXECUTIVE SUMMARY
As natural gas production has increased, so have concerns about the potential environmental and
human health impacts of hydraulic fracturing in the United States. Hydraulic fracturing, which involves
the pressurized injection of water, chemical additives, and proppants into a geologic formation, induces
fractures in the formation that stimulate the flow of natural gas or oil, thus increasing the volume of gas
or oil that can be recovered from coalbeds, shales, and tight sands—the so-called "unconventional"
reservoirs. Many concerns about hydraulic fracturing center on potential risks to drinking water
resources, although other issues have been raised. In response to public concern, Congress directed the
United States Environmental Protection Agency (EPA) to conduct research to examine the relationship
between hydraulic fracturing and drinking water resources. This document presents the plan for the
EPA study.
The overall purpose of this study is to understand the relationship between hydraulic fracturing and
drinking water resources. More specifically, the study is designed to examine the conditions that may
be associated with the potential contamination of drinking water resources, and to identify the factors
that may lead to human exposure and risks. The scope of the proposed research includes the full
lifecycle of water in hydraulic fracturing, from water acquisition through the mixing of chemicals and
actual fracturing to the post-fracturing stage, including the management of flowback and produced
water and its ultimate treatment and/or disposal. Figure 1 illustrates the hydraulic fracturing water
lifecycle and the key research questions EPA will address through this study.
The research identified in this study plan has been designed to answer the questions listed in Figure 1
and will require a broad range of expertise, including petroleum engineering, fate and transport
modeling, ground water hydrology, and toxicology. EPA will use case studies and generalized scenario
evaluations as organizing constructs for the research identified in this plan.
Retrospective case studies will focus on investigating reported instances of drinking water resource
contamination or other impacts in areas where hydraulic fracturing has already occurred. EPA will
conduct retrospective case studies at three to five sites across the United States. The sites will be
illustrative of the types of problems that have been reported to EPA during stakeholder meetings, and
will provide EPA with information regarding key factors that may be associated with drinking water
contamination. These studies will use existing data and possibly field sampling, modeling, and/or
parallel laboratory investigations to determine the potential relationship between reported impacts and
hydraulic fracturing activities.
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 extraction, drilling, hydraulic fracturing fluid injection, flowback, and gas production. EPA will
work with industry and other stakeholders to conduct two to three prospective case studies in different
regions of the United States. 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.
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Generalized scenario evaluations will allow EPA to explore hypothetical scenarios relating to hydraulic
fracturing activities, and to identify scenarios under which hydraulic fracturing may adversely impact
drinking water resources based on current understanding and available data.
To better understand potential human health effects, EPA plans to summarize the available data on the
toxicity of chemicals used in or released by hydraulic fracturing, and to identify and prioritize data gaps
for further investigation. 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.
The research projects identified for this study are organized according to the hydraulic fracturing water
lifecycle shown in Figure 1 and are summarized in Appendix A (p. 70). EPA is working with other federal
agencies to collaborate on some aspects of the research described in this study plan. Additionally, EPA
will announce requests for applications for extramural research projects related to this study as the
study plan is finalized. These projects will be conducted through EPA's Science To Achieve Results
(STAR) program.
All research activities associated with this study will be conducted in accordance with EPA's Quality
Assurance Program for environmental data. EPA will provide periodic updates on the progress of
various projects as the research is being conducted. The results of individual research projects will be
made available after undergoing a quality assurance review. Early results may indicate the need for EPA
to conduct further investigations to identify the key factors that may impact drinking water resources. It
is expected that a report of interim research results will be completed in 2012. This interim report will
contain a synthesis of EPA's research to date and will include results from retrospective case studies and
initial results from scenario evaluations. However, certain portions of the work described here,
including prospective case studies and work performed under STAR grants, are long-term projects that
are not likely to be finished at that time. Additional reports of study findings will be published as these
long-term projects progress, with a follow-up report on the study in 2014.
EPA recognizes that there are important potential research areas related to hydraulic fracturing other
than those involving drinking water resources, including effects on air quality, aquatic and terrestrial
ecosystem impacts, seismic risks, public safety concerns, occupational risks, and economic impacts.
These topics are outside the scope of the current study, but should be examined in the future.
This draft study plan will be submitted to EPA's Science Advisory Board (SAB) for review before being
finalized. Consistent with the operating procedures of the SAB, stakeholders and the public will have an
opportunity to provide comments for the SAB to take into account during the review.
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Water Use in Hydraulic
Fracturing Operations
Water Acquisition
Chemical Mixing
IF
Well Injection
Flowback and
Produced Water
Fundamental Research Question
How might large volume water withdrawals from ground and
surface water impact drinking water resources?
What are the possible impacts of releases 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 releases 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?
FIGURE 1. FUNDAMENTAL RESEARCH QUESTIONS POSED FOR EACH STAGE OF THE HYDRAULIC FRACTURING WATER LIFECYCLE
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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 United States. 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 South and West 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.
In Fiscal Year 2010, the U.S. Congress' Appropriation Conference Committee directed EPA to conduct
research to examine the relationship between hydraulic fracturing and drinking water resources:
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 a draft plan for EPA's research on hydraulic fracturing and drinking water
resources and responds to both the request of 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, produce an appropriate quantity and flow rate of water to serve as a source
of drinking water for public or private water supplies. This includes both underground sources of
drinking water (USDWs) and surface waters.
The overarching goal of this research is to answer the following questions:
• Can hydraulic fracturing impact drinking water resources?
« If so, what are the conditions associated with the potential impacts on drinking water resources
due to hydraulic fracturing activities?
To answer these questions, EPA has identified a set of proposed research activities associated with each
stage of the hydraulic fracturing water lifecycle, from water acquisition through the mixing of chemicals
and actual fracturing to post-fracturing production, including the management of flowback and
produced water and ultimate treatment and disposal. These research activities will identify potential
sources and pathways of exposure and will provide information about the toxicity of contaminants of
concern. This information can then be used to assess the potential risks to drinking water resources
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from hydraulic fracturing activities. Ultimately, the results of this study will 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
proposed research.
• Chapter 3 provides a brief overview of the natural gas production process.
• 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 proposes research specific to each stage.
• Chapter 7 summarizes EPA's case study approach, which is a central component of the research
plan.
• Chapter 8 describes proposed studies to characterize the toxicity and potential human health
effects of substances associated with hydraulic fracturing.
• Chapter 9 presents a brief discussion of hydraulic fracturing in the context of environmental
justice.
• Chapter 10 provides a short summary of how the proposed studies will address the research
questions posed for each stage of the water lifecycle.
• Chapter 11 identifies additional areas of concern relating to hydraulic fracturing that are outside
the scope of this study plan.
2 PROCESS FOR STUDY PLAN DEVELOPMENT
2.1 INITIAL SCIENCE ADVISORY BOARD REVIEW OF THE STUDY PLAN SCOPE
In early Fiscal Year 2010, EPA's Office of Research and Development (ORD) developed a document that
presented a proposed scope and initial design of the study (USEPA, 2010a). The document was
submitted to the EPA Science Advisory Board's (SAB's) Environmental Engineering Committee for review
in March 2010. The SAB is a public advisory committee that provides a balanced, expert assessment of
scientific matters relevant to EPA. In its response to EPA in June 2010 (USEPA, 2010c), the SAB
recommended that (1) initial research be focused on potential impacts to drinking water resources with
later research investigating more general impacts on water resources, (2) engagement with stakeholders
occur throughout the research process, and (3) 5 to 10 in-depth case studies at "locations selected to
represent the full range of regional variability of hydraulic fracturing across the nation" be part of the
research plan.
The SAB 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." This
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research plan, therefore, focuses on features of oil and gas production that are particular to—or closely
associated with—hydraulic fracturing, and their impacts on drinking water resources.
2.2 STAKEHOLDER INPUT
Stakeholder input has played, and will continue to play, an important role in the development of the
hydraulic fracturing study plan and the research it will involve. EPA has implemented a strategy that
engages stakeholders in dialogue and provides opportunities for input on the study scope and case
study locations. The strategy also provides a means for exchanging information with experts on
technical issues. EPA will continue to engage stakeholders as results from the study become available.
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 (IOGCC).
The federal partners included the Bureau of Land Management, the U.S. Geological Survey (USGS), the
U.S. Fish and Wildlife Service, the U.S. Forest Service, the U.S. Department of Energy (DOE), the U.S.
Army Corps of Engineers (USAGE), the National Park Service (NPS), and the Agency for Toxic Substances
and Disease Registry. There were 36 registered participants for the tribal webinar representing 25 tribal
governments; in addition, a meeting with the Haudenosaunee Environmental Task Force was held in
August 2010 and 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 or 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?
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• Where do you recommend EPA conduct case studies?
Total attendance for all of the information public meetings exceeded 3,500 and more than 700 verbal
comments were heard.
Summaries of all of the stakeholder meetings can be found at http://water.epa.gov/type/groundwater/
uic/class2/hydraulicfracturing/wells_hydroout.cfm.
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.
2.3 RESEARCH PRIORITIZATION
In developing this proposed study plan, EPA considered the results of a review of the literature,1
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 initial SAB review of the study plan scope (USEPA, 2010c).
Based on stakeholder input and the expected growth in shale gas development, this study plan
emphasizes hydraulic fracturing in shale formations. Portions of the proposed research, however, may
provide information on hydraulic fracturing in coalbed methane reservoirs and tight sands, and EPA will
pursue these research opportunities when possible.
As requested by Congress, EPA identified fundamental scientific research questions (summarized in
Chapter 4) that will frame the research and help 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 risks at each stage of the hydraulic
fracturing water lifecycle. Other criteria considered in prioritizing proposed research activities include:
• 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.
• Leverage: Relevant work that EPA could leverage with co-investigators received a higher
priority.
Application of the criteria listed above ensures that resources are provided for the areas that potentially
pose the greatest risk to drinking water resources.
1 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.
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2.4 NEXT STEPS
The next steps in the development and implementation of the study plan are:
» The draft study plan will be sent to the SAB for peer review and made available to the public in
February 2011. The SAB will have an opportunity to hear verbal comments and read written
comments from stakeholders and the public during their March 2011 public meeting to review
the draft study plan. EPA will respond to comments from the SAB, and will adjust the study plan
as appropriate.
» EPA will conduct the research described in this plan, and plans to announce requests for
applications for extramural research projects in the early part of 2011 for research that is
related to this study. Additionally, it is likely that other federal agencies will cooperate with EPA
on some aspects of the research.
» The research projects will begin in the early part of 2011 after EPA receives and responds to
comments from the SAB.
» Periodic updates will be provided on the progress of the research projects.
• A study report providing interim research results is expected to be completed in 2012 and will
be made available to the public.
» Additional study results will be published as individual research projects are completed, with an
additional report expected to be published in 2014.
2.5 INTERAGENCY COOPERATION
In a series of meetings, EPA consulted with several key state and federal agencies regarding research
related to hydraulic fracturing. EPA met with representatives from DOE and DOE's National Energy
Technology Laboratory (NETL), USGS, USAGE, and IOGCC to learn about research that those agencies are
involved in and to identify opportunities for collaboration and leverage. EPA also participated in a series
of meetings in which a number of other federal agencies participated. As a result of those meetings,
EPA has identified work underway by others that can inform its own study. EPA continues to discuss
opportunities to collaborate on information gathering and research efforts with other agencies. In
particular, the Agency plans to coordinate with DOE and USGS on existing and future research projects.
Regular meetings between EPA and DOE will be set up to follow each agency's research on hydraulic
fracturing and to exchange information among experts.
Federal agencies have also had an opportunity to provide comments on this draft study plan through an
interagency review. EPA received comments from the Agency for Toxic Substances and Disease
Registry, DOE, the Bureau of Land Management, USGS, the U.S. Fish and Wildlife Service, the Office of
Management and Budget, the U.S. Energy Information Administration (EIA), the Occupational Safety and
Health Administration, and the National Institute of Occupational Health and Safety. These comments
have been reviewed and modifications to the study plan have been made where appropriate.
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2.6 QUALITY ASSURANCE
All EPA-funded research projects, both intramural and extramural, that generate or use environmental
data to make conclusions or recommendations must comply with Agency Quality Assurance (QA)
Program requirements (USEPA, 2002b). EPA recognizes the value of using a graded approach to QA such
that QA requirements are based on the importance of the work to which the QA program applies. Given
the significant national interest in the results of hydraulic fracturing related research, the following
rigorous QA approach will be used:
• Research projects must comply with Agency requirements and guidance for quality assurance
project plans (QAPPs), including the use of data quality objectives.
» Audits will be conducted as described in an audit plan and will include technical systems audits,
audits of data quality, and data quality assessments.
» Performance evaluations of measurement systems will be conducted (if available).
» QA review of products2 will occur.
• Reports must have a readily identifiable QA section.
« Research records will be managed according to EPA's record schedule for Applied and Directed
Scientific Research.
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 proposed research, it is necessary to identify a Program Quality
Assurance Manager who will coordinate the rigorous QA approach described above and oversee its
implementation across all participating organizations. Typically, this person is associated with the
organization that has the technical lead for the research program. 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.
3 OVERVIEW OF UNCONVENTIONAL NATURAL GAS PRODUCTION
Hydraulic fracturing is often used to stimulate the production of oil and gas from unconventional oil and
gas deposits, which include shales, coalbeds, and tight sands.3 Unconventional natural gas deposits
generally contain a lower concentration of natural gas over broader areas that have a lower
permeability than conventional gas reservoirs, which are typically porous and permeable and do not
require additional stimulation for production (Vidas and Hugman, 2008). Similarly, hydraulic fracturing
can make oil production from shale cost-effective.
2 Applicable products may include reports, journal articles, symposium/conference papers, extended abstracts,
computer products/software/models/databases, and scientific data.
3 The use of hydraulic fracturing is not limited to natural gas production. It may also be used when drilling for oil
(STRONGER, 2010), and has been used for other purposes, such as removing contaminants from soil and ground
water at waste disposal sites, make geothermal wells more productive, and to complete water wells (Nemat-
Nassar et al., 1983; New Hampshire Department of Environmental Services, 2010).
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Natural Gas Production in the United States
14%
2%
45%
1%
2009
-24 trillion cubic feet per year)
| Net imports
| Shale gas
D Tight sands
Sources of Natural Gas
fj Coalbed methane
• Alaska
D Associated with oil
Projected for 2035
-26 trillion cubic feet per year)
fj Non-associated onshore
L~] Non-associated offshore
FIGURE 2. NATURAL GAS PRODUCTION IN THE UNITED STATES (DATA FROM USEIA, 2010)
Unconventional natural gas development has become an increasingly important source of natural gas in
the United States 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 has risen to 50 percent in 2009 and is
projected to increase to 60 percent in 2035 (USEIA, 2010). This rise in hydraulic fracturing activities is
also reflected in the number of drilling rigs operating in the United States; there were 603 horizontal gas
rigs in June 2010, up 277 from the previous year (Baker Hughes, 2010). Most of these were involved in
gas extraction via hydraulic fracturing.
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Shale Gas Plays, Lower 48 States
Montana
Tfirust
Ben
.Gammoi
\J
o* > ?3ni
o»j/ ,,
Paradj.. :
Woodford/ /_
-^.fi= r^^^F^stviltec-^
•JlJ.-.k '/Vrtl! C
f 1 Shale Ga
Play*
Basins
Source. Energy Information Administrallon eased on data (rom various putAshed studies
Updated March 10.2010
FIGURE 3. SHALE GAS PLAYS IN THE CONTIGUOUS UNITED STATES
Shale gas extraction. Shale rock formations have become an important source of natural gas in the
United States, and can be found in many locations across the country as shown in Figure 3. Depths for
shale gas formations (commonly referring to as "plays") 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 U.S. natural gas supply in 2009, and will
constitute 45 percent of the U.S. 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 concentrated primarily in the Williston Basin in North
Dakota, although oil production is increasing in the Eagle Ford Shale in Texas and the Niobrara Shale in
Colorado, Nebraska, and Wyoming (USEIA, 2010; OilShaleGas.com, 2010).
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Coalbed Methane Fields, Lower 48 States
~
fc
•'' ,
; Black Warnoi
0 100 2« 300 400
N
A
FIGURE 4. COALBED METHANE DEPOSITS IN THE CONTIGUOUS UNITED STATES
Production ofcoalbed 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 ofcoalbed methane can be challenging from a cost-effectiveness perspective
(Rogers et al., 2007). Figure displays coalbed methane reservoirs in the contiguous United States. In
1984, there were very few coalbed methane wells in the United States; 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 U.S. natural gas production; this percentage
would 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.
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Major Tight Gas Plays, Lower 48 States'
J_-»-
GQ-AnafciW
^^js^fc* r«vtoPrtf—
0 100 200 3QQ 400
Source. Energy Informatjon Admmslration based on data frc
Updated June 6, 2010
s pubiisheO siudies
FIGURE 5. MAJOR TIGHT GAS PLAYS IN THE CONTIGUOUS UNITED STATES
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 United States 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 United States. Typical depths of tight sand
formations range from 1,200 to 20,000 feet across the United States (Prouty, 2001). Almost all tight
sand reservoirs require hydraulic fracturing to release gas unless natural fractures are present.
The following sections provide an overview of unconventional natural gas production, including site
selection and preparation, well construction and development, hydraulic fracturing, and 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;
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
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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.
3.2 WELL CONSTRUCTION AND DEVELOPMENT
Current practices in drilling for natural gas include drilling vertical, horizontal, and directional (S-shaped)
wells. Figure 6 depicts two different well completions, one in a typical deep shale gas-bearing formation
like the Marcellus Shale (6a) and one in a shallower environment (6b) 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 shown in Figure 6a typically has several thousand feet of rock formation separating
underground drinking water resources, while Figure 6b shows that gas production can take place at
shallow depths that also contain underground sources of drinking water. The water well in Figure 6b
illustrates the relative depths of a gas well and a water well.
Water
Acquisition
Chemical
Mixing
Well
Injection
Flowback and
Produced Water
n
„ Wastewater
Storage _ .
tanks Treatment and
C Waste Disposal
,
Aquifer
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.
Hydrocarbon-bearing
Formation
i/Vater Use in Hydraulic Fracturing Operations
Water Acquisition - Large volumes of water are
transported for the fracturing process.
hemical Mixing - Equipment mixes water, chemicals,
and sand at the well site.
Well Injection - The hydraulic fracturing fluid is
pumped into the well at high injection rates.
^lowback and Produced Water- Recovered water
(called flowback and produced water) is stored
on-site in open pits or storage tanks.
Wastewater Treatment and Waste Disposal - The
wastewater is then transported for treatment and/or
disposal.
Induced Fractures
FIGURE 6a. ILLUSTRATION OF A HORIZONTAL WELL SHOWING THE WATER LIFECYCLE IN HYDRAULIC
FRACTURING
Figure 6a 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
Energy, 2010) while the "toe" of the horizontal leg can be almost 2 miles from the vertical leg (Zoback et
al., 2010). Horizontal drilling provides more exposure to a formation than a vertical well does;
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FIGURE 6b. ILLUSTRATION OF A VERTICAL WELL WHERE
HYDRAULIC FRAf TURING OCCURS NEAR AN UNDERGROUND
SOURCE OF DRINKING WATER
therefore, it increases recovery of natural
gas and makes drilling 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.
In all wells, casing and cement are
installed to contain the contents of the
well in an effort to prevent
contamination of the surrounding
subsurface formations, especially USDWs. The high injection pressures associated with the hydraulic
fracturing process, and the increased potential for aquifer contamination due to the close proximity of
the aquifer to the well, make cementing and casing activities a crucial step in protecting ground water.
The process of constructing a well is described in greater detail later in the study plan.
3.3 HYDRAULIC FRACTURING
After the well is constructed and perforated, the targeted formation (shale, coalbed, or tight sands) is
hydraulically fractured to stimulate natural gas production. As shown in Figure 6a, the hydraulic
fracturing process requires large volumes of water that must be transported to the well site. Once on-
site, the water is mixed with chemicals and a propping agent (called a proppant) such as sand, bauxite,
or ceramic beads. The resulting hydraulic fracturing fluid is pumped down the well under high
pressures, causing the targeted formation to fracture. As the injection pressure is reduced, the fluid is
returned to the surface, leaving the proppant behind to keep the fractures open. The inset in Figure 6b
illustrates how the resulting fractures create pathways in otherwise impermeable gas-containing
formations, resulting in gas flow to the well for production. A portion of the injected fracturing fluid
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(water, chemical additives, and proppant), as well as naturally occurring substances released from the
targeted formation, is then returned to the surface as flowback and produced water. These
wastewaters are stored on-site in tanks or pits before being transported for treatment, disposal, land
application, and/or discharge.
3.4 WELL PRODUCTION
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 United States
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 Draft Supplemental Generic
Environmental Impact Statement (NYS dSGEIS) 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,
2009). 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 cost-
effectively 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 dSGEIS estimates that wells may be refractured after roughly five years of service
(NYSDEC, 2009).
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. However, 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. However, EPA may assess existing state
regulations in a separate effort.
4 THE HYDRAULIC FRACTURING WATER LIFECYCLE
Figure 7 illustrates the key stages of the hydraulic fracturing water lifecycle—from water acquisition to
wastewater treatment and disposal—and the potential drinking water issues associated with each stage.
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Water Use in Hydraulic
Fracturing Operations
Potential Drinking Water Issues
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 water (e.g., well malfunction)
m Fracturing fluid migration into drinking water aquifers
• Formation fluid displacement into aquifers
Mobilization of subsurface formation materials into aquifers
ftelease to surface and ground water
Leakage from on-site storage into drinking water resources
Irjiproper pit construction, maintenance, and/or closure
Surface and/or subsurface discharge into surface and ground water
Incomplete treatment of wastewater and solid residuals
Waltewater transportation accidents
FIGURE 7. WATER USE IN HYDRAULIC FRACTURING OPERATIONS
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Summarized below are the fundamental research questions EPA has identified for each stage of the
hydraulic fracturing water lifecycle.
• Water acquisition: How might large volume water withdrawals from ground and surface water
impact drinking water resources?
• Chemical mixing: What are the possible impacts of releases 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 releases 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?
The next chapter outlines the research approach and activities needed to answer these questions.
5 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 need to take a transdisciplinary research
approach that integrates various types of expertise from inside and outside the EPA.
Cose studies and generalized scenario evaluations provide organizing constructs for the research that
will be used to address the key questions associated with each of the five water cycle stages of hydraulic
fracturing. Table 1 shows the objectives for the case studies, both retrospective and prospective, and
the scenario evaluations. Each of these approaches is briefly described below.
TABLE 1. RELATIONSHIP BETWEEN CASE STUDIES AND SCENARIO EVALUATIONS
Activity Objectives
Case studies
Retrospective Perform a forensic analysis of sites with reported contamination to understand the
underlying mechanisms and potential impacts on drinking water resources
Prospective Develop understanding of hydraulic fracturing processes and their potential
impacts on drinking water resources
Scenario evaluation Assess the potential for hydraulic fracturing to impact drinking water resources
based on knowledge developed
5.1 CASE STUDIES
Case studies are widely used to conduct in-depth investigations of complex topics and provide a
systematic framework for investigating the relationship among relevant factors. In conjunction with
other elements of the research program, case studies can help to determine whether drinking water
resources are impacted by hydraulic fracturing, the extent and possible causes of any impacts, and what
management practices are, or may be, used to avoid or mitigate such impacts. Additionally, case studies
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may provide data and model inputs to assess the fate and transport of fluids and contaminants in
different regions and geologic settings.
Retrospective case studies are focused on investigating reported instances of drinking water resource
contamination in areas where hydraulic fracturing events have already occurred. The goal is to
determine whether or not the reported impacts are due to hydraulic fracturing activities. These studies
will use existing data and will include environmental field sampling, modeling, and/or parallel laboratory
investigations.
Prospective case studies involve sites where hydraulic fracturing will be implemented after the research
is initiated. 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, data will be collected to characterize both the pre- and post-fracturing conditions at the site.
This progressive data collection will allow EPA to evaluate changes in water availability and quality, as
well as other factors, over time to gain a better understanding of the impacts of hydraulic fracturing on
drinking water resources. Prospective case studies can also provide data with which models of hydraulic
fracturing and associated processes, such as fate and transport of chemical contaminants, can be
evaluated and improved.
Retrospective and prospective case studies are discussed further in Chapter 7.
5.2 SCENARIO EVALUATION
The objective of this approach is to explore realistic, hypothetical scenarios across the hydraulic
fracturing water lifecycle that may result in adverse impacts to drinking water resources based on
current understanding 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. Potential modes of failure, both in terms of
engineering controls and geologic characteristics, will be introduced and modeled to represent various
states of system vulnerability. The scenario evaluations will produce insights into site-specific and
regional vulnerabilities.
The proposed applications of scenario evaluation will be described in detail for each stage of the
hydraulic fracturing water lifecycle in the next chapter.
5.3 TOOLS
Various combinations of the following four general tools or activities will be used to conduct the case
studies and scenario evaluations:
Existing data evaluation. Various existing data support the proposed hydraulic fracturing research
study, including mapped data, surface water discharge data, chemical data, and site data. These data
are available from a variety of sources, such as state regulatory agencies, federal agencies, industry, and
public sources. To support this study, EPA has specifically requested data from nine hydraulic fracturing
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service companies. As detailed in Appendix C, EPA asked for data on the chemical composition of fluids
used in the fracturing process, the health and environmental impacts of the chemicals, standard
operating procedures, and locations where fracturing has been conducted or is planned. The hydraulic
fracturing service companies have claimed this data to be confidential business information.
Field monitoring. EPA will collect field samples during both retrospective and prospective case studies
to look for the migration of chemical and gas contaminants into drinking water resources as a result of
hydraulic fracturing activities. Direct studies of field sites can also assess the behavior of chemicals in
the environment by characterizing the flow and transport of chemicals through heterogeneous media
on a scale that is not represented in the laboratory.
Laboratory-scale experimentation/analysis. Laboratory studies will be necessary to develop and refine
analytical methods needed to analyze samples collected during field monitoring activities. For hydraulic
fracturing-related chemicals without extensive study, laboratory experimentation may be needed to
determine the processes that control the transport and ultimate fate of the chemicals, including
sorption and biodegradation.
Modeling. Modeling is a tool for integrating diverse phenomena to enhance understanding of
environmental exposures. When sufficiently tested, models can also allow alternate hypothesis testing,
which can help to determine the plausibility of contamination of drinking water resources due to
hydraulic fracturing activities. Models may also be able to identify the factors that are the most
important in understanding hydraulic fracturing impacts on drinking water resources.
6 PROPOSED RESEARCH
This chapter is organized by the hydraulic fracturing water lifecycle depicted in Figure 7 and the
associated fundamental research questions outlined in Chapter 4. Each section of this chapter provides
relevant background information on a water cycle stage, as well as identifying a series of more specific
questions that need to be researched in order to answer one of these fundamental questions. These
secondary research questions are listed in Table 2. Proposed research activities and potential research
outcomes are outlined at the end of the discussion of each stage of the water lifecycle.
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TABLE 2. HYDRAULIC FRACTURING RESEARCH QUESTIONS
Water Lifecycle Stage
Water acquisition
Chemical mixing
Well injection
Flowback and produced
water
Wastewater treatment
and waste disposal
Fundamental Research Question
How might large volume water
withdrawals from ground and
surface water impact drinking
water resources?
What are the possible impacts of
accidental releases 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
accidental releases 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?
Secondary Research Questions
» What are the impacts on water availability?
• What are the impacts on water quality?
* What is the composition of hydraulic
fracturing fluids and what are the toxic effects
of these constituents?
• What factors may influence the likelihood of
contamination of drinking water resources?
» How effective are mitigation approaches in
reducing impacts to drinking water
resources?
» How effective are well construction practices
at containing gases and fluids before, during,
and after fracturing?
• What are the potential impacts of pre-existing
artificial or natural pathways/features on
contaminant transport?
• What chemical/physical/biological processes
could impact the fate and transport of
substances in the subsurface?
• What are the toxic effects of naturally
occurring substances?
• What is the composition and variability of
flowback and produced water and what are
the toxic effects of these constituents?
• What factors may influence the likelihood of
contamination of drinking water resources?
• How effective are mitigation approaches in
reducing impacts to drinking water
resources?
• How effective are treatment and disposal
methods?
A summary of the research outlined in this chapter can be found in Appendix A.
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6.1 WATER ACQUISITION: How MIGHT LARGE VOLUME WATER WITHDRAWALS FROM
GROUND AND SURFACE WATER IMPACT 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, 1990 and 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 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 IN DIFFERENT SHALE PLAYS
Shale Play
Barnett
Fayetteville
Haynesville
Marcellus
Formation
Depth (ft)
6,500-8,500
1,000-7,000
10,500-13,500
4,000-8,500
Porosity (%)
4-5
2-8
8-9
10
Organic
Content (%)
4.5
4-10
0.5-4
3-12
Freshwater
Depth (ft)
1,200
500
400
850
Fracturing Water
(gallons/well)
2,300,000
2,900,000
2,700,000
3,800,000
Data are from GWPC and ALL Consulting, 2009.
EPA estimates that approximately 35,000 wells are fractured each year across the United States.
Assuming that the majority of these wells are horizontal wells, the annual water requirement may range
from 70 to 140 billion gallons. This is equivalent to the total amount of water used each year in roughly
40 to 80 cities with a population of 50,000 or about 1 to 2 cities of 2.5 million people. In the Barnett
Shale area, the annual estimates of total water used by gas producers range 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 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, 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. This storage practice is used, for example, in the Barnett and Fayetteville Shale plays, where
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.
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Whether the withdrawal of this much water from local surface or ground water sources has a significant
impact 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). On
the other hand, in less arid parts of the country (e.g., the Barnett Shale area), the impact of water
withdrawals may be less significant. 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) rather than on overall water use.
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 10 to 40 percent of the original fluid injected (Ewing,
2008; Vidic, 2010). 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). Acid mine drainage, which has a lower TDS
concentration, has also been suggested as possible source water for hydraulic fracturing (Vidic, 2010).
API has published general guidance on best practices for water management associated with hydraulic
fracturing (API, 2010a). Such practices include proactive communication with local water agencies and
planning for a potential well drilling program on a basin-wide basis. API also recommends a detailed
evaluation of the amount and quality of water required in addition to the identification and evaluation
of potential water sources. Other literature describes current and proposed practices for on-site water
management at some shale gas plays (Satterfield et al., 2008; Horn, 2009; Veil, 2007 and 2010).
6.1.2 WHAT ARE THE IMPACTS ON WATER AVAILABILITY?
Large volume water withdrawals for hydraulic fracturing are unique 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 and other
uses 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 (personal communication from Gary M.
Hanson, Director, Red River Watershed Management Institute, Louisiana State University in Shreveport,
to EPA's Robert Puls).
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.
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6.1.3 WHAT ARE THE IMPACTS ON WATER QUALITY?
The lowering of water levels in aquifers may also affect water quality by exposing naturally occurring
minerals to an oxygen-rich environment. This may cause chemical changes to the minerals that can
affect solubility and mobility and may cause salination of the water and other chemical contaminations.
Bacterial growth may be stimulated by lowered water tables, causing taste and odor problems.
Depletion of aquifers may also cause an upwelling of lower quality water from deeper within an aquifer.
In some cases, changes in water levels may interact with well construction in such a way as to cause an
increase in siltation or cloudiness of the produced water. Large volume water withdrawals from ground
water can also lead to subsidence and/or destabilization of the geology.
Withdrawals of large quantities of water from surface water resources (e.g., streams) may have
significant impacts on 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 may 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 water and surface water are hydraulically
connected (Winter et al., 1998); any changes in the quantity and quality of the surface water will affect
ground water and vice versa.
6.1.4 PROPOSED RESEARCH ACTIVITIES—WATER ACQUISITION
6.1.4.1 WATER AVAILABILITY: ANALYSIS OF EXISTING DATA, PROSPECTIVE CASE STUDIES, AND SCENARIO
EVALUATION
Analysis of existing data. In cooperation with USAGE, 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 selected study areas. 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
recorded water used during fracturing. EPA has chosen potential study areas that represent both arid
and humid areas of the country, restricting its selection to areas for which sufficient data are available.
Current potential study areas include: (1) the Bakken Shale in North Dakota, (2) the Barnett Shale in
Texas, (3) Garfield County/Piceance Basin in Colorado, and (4) the Susquehanna River Basin/Marcellus
Shale in Pennsylvania.
Simple water balance and geospatial information system (GIS) analysis will be conducted using the
existing data. The collected data will be compiled in conjunction with hydrological trends over the same
period of time. Control areas that have similar baseline water demands and have no oil and gas
development will be compared to areas with intense hydraulic fracturing activity to isolate and identify
the impacts of hydraulic fracturing on water availability. A critical analysis of trends in water flows and
water usage patterns in areas impacted by hydraulic fracturing activities will be conducted to determine
whether water withdrawals for hydraulic fracturing activities alter ground and surface water flows. Data
collection will support the assessment of the 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).
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Prospective case studies. EPA will conduct prospective case studies that will monitor all aspects of the
hydraulic fracturing water lifecycle illustrated in Figure . These prospective case studies will collect data
to evaluate potential impacts on water availability due to large volume water withdrawals, and will
assess management practices related to water acquisition. Additionally, the assessment of site-scale
water use on the hydrologic cycle will allow EPA to test the models used in the scenario evaluations
described below.
Scenario evaluation. Scenario evaluations will assess the environmental futures and impacts of
hydraulic fracturing operations at various spatial and temporal scales in the selected study areas 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 non-conventional natural gas 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 Program
(for 2030) and the EPA ORD Futures Midwest Landscape Program (for 2022). 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 physics-
based watershed and ground water models will be used for representation of the water balance and
hydrologic cycle, as discussed in Appendix H.
6.1.4.2 WATER QUALITY: ANALYSIS OF EXISTING DATA AND PROSPECTIVE CASE STUDIES
Analysis of existing data. EPA will use the data collected in collaboration with USAGE, USGS, and others
to analyze changes in water quality in areas impacted by hydraulic fracturing, and to determine if any
changes are due to water withdrawals for hydraulic fracturing. Water quality trends will also be
evaluated to determine the potential for using routine monitoring data in identifying water resource
vulnerabilities.
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. The resulting data will be analyzed to determine if there are any changes in water
quality, and if these changes are due to the large volume water withdrawals associated with hydraulic
fracturing.
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6.1.5 POTENTIAL RESEARCH OUTCOMES
The research outlined above will allow EPA to:
» Identify possible impacts on water availability and quality associated with large volume water
withdrawals for hydraulic fracturing.
« Determine the cumulative effects of large volume water withdrawals within a watershed and
aquifer.
• Develop metrics that can be used to evaluate the vulnerability of water resources.
• Provide an assessment of current water resource management practices related to hydraulic
fracturing.
6.2 CHEMICAL MIXING: WHAT ARE THE POSSIBLE IMPACTS OF RELEASES OF HYDRAULIC
FRACTURING FLUIDS ON DRINKING WATER RESOURCES?
6.2.1 BACKGROUND
Most hydraulic fracturing fluids are water-based fluids that serve two purposes: to create pressure to
propagate the fracture and to carry the proppant into the fracture. 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).
In addition to proppants and water, hydraulic fracturing fluids contain chemical additives. The types and
concentrations of proppants and chemical additives vary depending on the conditions of the specific
well being fractured, and are selected to create a fracturing fluid tailored to the properties of the
formation and the needs of the project. In many cases, reservoir properties are entered into modeling
programs that simulate fractures (see Castle et al., 2005, and Hossain and Rahman, 2008, for
commercial software available for fracture design). The fracturing models are then used to reverse
engineer the requirements for fluid composition, pump rates, and proppant concentrations. In shale gas
plays, for example, the fracturing fluid is predominantly water and sand, with added chemicals
depending upon the characteristics of the source water and the shale play formation being fractured
(GWPC and ALL Consulting, 2009).
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 D.
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TABLE 4. AN EXAMPLE OF THE VOLUMETRIC COMPOSITION OF HYDRAULIC FRACTURING FLUID
Component/
Additive Type
Water
Proppant
Acid
Friction reducer
Surfactant
Potassium
chloride
Gelling agent
Scale inhibitor
pH adjusting agent
Breaker
Crosslinker
Iron control
Corrosion inhibitor
Biocide
Example
Compound(s)
Silica, quartz sand
Hydrochloric acid
Polyacrylamide,
mineral oil
Isopropanol
Guargum,
hydroxyethyl cellulose
Ethylene glycol
Sodium or potassium
carbonate
Ammonium persulfate
Borate salts
Citric acid
N,n-dimethyl
formamide
Glutaraldehyde
Purpose
Deliver proppant
Keep fractures open to allow
gas flow out
Dissolve minerals, initiate
cracks in the rock
Minimize friction between fluid
and the pipe
Increase the viscosity of the
fluid
Create a brine carrier fluid
Thickens the fluid to suspend
the proppant
Prevent scale deposits in the
pipe
Maintain the effectiveness of
other components
Allow delayed breakdown of
the gel
Maintain fluid viscosity as
temperature increases
Prevent precipitation of metal
oxides
Prevent pipe corrosion
Eliminate bacteria
Percent
Composition
(by Volume)
90
9.51
0.123
0.088
0.085
0.06
0.056
0.043
0.011
0.01
0.007
0.004
0.002
0.001
Volume of
Chemical
(Gallons)3
2,700,000
285,300
3,690
2,640
2,550
1,800
1,680
1,290
330
300
210
120
60
30
Data are from GWPC and ALL Consulting, 2009, and API, 2010b. Note that the example compounds are not
necessarily the compounds used in this fracturing operation in the Fayetteville Shale. a Based on 3 million gallons
of fluid used.
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, however, 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 comprising 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).
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6.2.2 WHAT is THE COMPOSITION OF HYDRAULIC FRACTURING FLUIDS AND WHAT ARE THE TOXIC EFFECTS OF
THESE CONSTITUENTS?
In 2010, EPA compiled a list of chemicals that were publicly known to be used in hydraulic fracturing
(Table Dl in Appendix D). The chemicals identified in Table Dl, however, do 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. In January 2011, Congressmen Waxman and Markey and
Congresswoman DeGette notified EPA that they found that "between 2005 and 2009, oil and gas service
companies injected 32.2 million gallons of diesel fuel or hydraulic fracturing fluids containing diesel fuel
in wells in 19 states" (Waxman et. al, 2011). Stakeholder meetings and media reports have emphasized
the public's concern regarding the identity and toxicity of chemicals used in hydraulic fracturing.
Much of the information regarding the identity and concentration of chemicals used in hydraulic
fracturing fluids is considered by the industry to be proprietary and, therefore, confidential. This makes
identifying the toxicity and human health effects associated with these chemicals difficult. Table 4
illustrates that the chemicals used in hydraulic fracturing fluids can have a range of toxicities. For
example, sand, polyacrylamide, guar gum, and hydroxyethyl cellulose are relatively benign materials.
Acids and bases present an irritant response upon dermal or inhalation exposure, but more acute
responses are possible. On the other hand, chronic toxicity has been associated with some identified
chemicals, such as ethylene glycol, glutaraldehyde, and n,n-dimethyl formamide (TOXNET, 2011). An
approach for assessing the toxicity and human health effects of fracturing fluid additives is outlined in
Chapter 8.
6.2.3 WHAT FACTORS MAY INFLUENCE THE LIKELIHOOD OF CONTAMINATION OF DRINKING WATER
RESOURCES?
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, 2009).
6.2.4 HOW EFFECTIVE ARE MITIGATION APPROACHES IN REDUCING IMPACTS TO DRINKING WATER
RESOURCES?
API provides a description of general practices relating to the transportation, storage, and handling of
source water and other fluids prior to fracturing (API, 2010a). However, the extent to which these
practices are followed in the industry or what other practices may be used is unclear.
6.2.5 PROPOSED RESEARCH ACTIVITIES—CHEMICAL MIXING
6.2.5.1 CHEMICAL IDENTITY AND TOXICITY: 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
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past five years (Appendix C). This information will provide EPA with a better understanding of the
common compositions of hydraulic fracturing fluids (e.g., 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 are currently used as well as those that
are no longer used in hydraulic fracturing operations, but could be present in areas where retrospective
case studies will be conducted. The data collected from this request will also 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 Dl.
The chemical list from the nine companies will be combined with the list of publicly known chemical
additives to provide EPA with a comprehensive list of chemicals used in hydraulic fracturing operations.
The resulting list of chemical additives will be used in two ways: First, EPA will work to determine the
toxicity and estimated human health effects associated with hydraulic fracturing fluid chemical additives
using methods described later in Chapter 8. Secondly, this list of chemicals will allow EPA to identify
existing analytical methods—or develop new methods—to detect fracturing fluids and their degradation
products in drinking water resources. EPA expects 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 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 fate and transport of the chemical (e.g., mobility
in the environment), and (4) the availability of detection methods.
6.2.5.2 HYDRAULIC FRACTURING FLUID RELEASE: ANALYSIS OF EXISTING DATA AND CASE STUDIES
Analysis of existing data. The tanks, valves, and pipes used to store and mix hydraulic fracturing fluid
(i.e., water, proppant, and chemical additives) are subject to spills, releases, or leaks (subsequently, the
term "release" will refer to a leak, spill, or release). Releases, in general, are not restricted to hydraulic
fracturing operations, and can occur under a variety of conditions. Because these are common types of
problems, 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 hydraulic fracturing fluid chemical additives generated through the research proposed in
Section 6.2.5.1 to identify individual chemicals and classes of chemicals for review in the existing
scientific literature. EPA will then identify relevant existing research on the fate and transport of
hydraulic fracturing fluid additives. The relevant research will be summarized to determine the known
impacts of spills of fracturing fluid on drinking water resources and to identify existing knowledge gaps
related to surface spills of hydraulic fracturing fluid chemical additives.
Retrospective case studies. Some of the candidate case study sites (listed in Appendix F) have reported
accidental releases from chemical tanks, supply lines, or leaking valves. It is expected that at least one
of the case studies chosen will allow EPA to investigate the impacts of accidental releases on drinking
water resources.
Prospective case studies. Prospective case studies will monitor and assess current chemical
management practices, and will identify potential areas of concern related to on-site chemical mixing of
hydraulic fracturing fluid. EPA will also collect information on the effectiveness of current management
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practices used to contain or mitigate the impacts of spills and/or leaks of fracturing fluid on drinking
water resources.
6.2.6 POTENTIAL RESEARCH OUTCOMES
Through the above research activities, EPA will:
« Summarize available data on the identity and frequency of use of various hydraulic fracturing
chemicals, the concentrations at which the chemicals are typically injected, and the total
amounts used.
* Identify the toxicity of chemical additives, and apply tools to prioritize data gaps and identify
chemicals for further assessment.
• Identify a set of chemical indicators associated with hydraulic fracturing fluids and associated
analytical methods.
» Determine the likelihood that surface spills will result in the contamination of drinking water
resources.
• Assess current management practices related to on-site chemical storage and mixing.
6.3 WELL INJECTION: WHAT ARE THE POSSIBLE IMPACTS OF THE INJECTION AND FRACTURING
PROCESS ON DRINKING WATER RESOURCES?
6.3.1 BACKGROUND
Ideally, the successful injection of hydraulic fracturing fluid results in natural gas production without
contamination of USDWs, and is necessarily dependent upon the mechanical integrity of the well and
the fluid design. The fluid design is determined by the subsurface properties and the oil/gas service field
operator. Mechanical integrity is determined by well design and construction, which is regulated by the
states. Requirements for well construction vary from state to state, but many states incorporate
standards such as those published by API (2009). It is useful, therefore, to provide a brief summary of
well construction, which is adapted from the well construction and integrity guidelines published by API
(2009).
6.3.1.1 WELL DESIGN AND CONSTRUCTION
According to API (2009), 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." Thus, proper well construction is essential for isolating the
production zone from USDWs, and includes drilling a hole, installing a steel pipe (casing), and cementing
the pipe in place. These activities are repeated multiple times throughout the drilling event until the
well is complete.
Drilling. Various techniques can be used to drill wells. For example, air or water can be used to drill
wells in coalbed methane formations and other fragile formations (Rogers et al., 2007). In most cases,
however, 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")
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is circulated down the drilling string. Water-based liquids
typically contain a mixture of water, barite, clay, and chemical
additives (OilGasGlossary.com, 2010). This fluid serves multiple
purposes, including cooling the drill bit, lubricating the drilling
assembly, removing the formation cuttings, 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 of.
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. Because fluid is confined within the casing, the
possibility of contamination of zones adjacent to the well is
greatly diminished.
FIGURES. WELL CONSTRUCTION
Figure 8 illustrates the different types of casings that may be used
in well construction: conductor, surface, intermediate (if necessary), and production. Each casing serves
ique purposp. Ideally, the surface casing should extend below the base of the deepest USDW and
be cemented to the surface. This casing isolates the USDWs 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.
..
._i _.
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.
Cementing. Once the casing is inserted in the borehole, it is cemented into place by pumping a cement
slurry down the casing and up the annular space between the formation and the outside of the casing.
The principal functions of the cement (for vertical wells or the vertical portion of a horizontal well) are to
be of suitable quality (during and after setting) 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.
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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. Even a correctly constructed well can fail over time due to downhole stresses and
corrosion (Bellabarba et al., 2008). Therefore, ongoing mechanical integrity testing of the well is
recommended; many states require that wells be tested periodically (GWPC, 2009).
6.3.1.2 INJECTION OF HYDRAULIC FRACTURING FLUID
Before the injection of hydraulic fracturing fluid, the production casing is perforated using explosive
charges. The perforations allow the injected fluid to enter, and thus fracture, the target formation.
Wells may be fractured either in a single stage or in multiple stages as determined by the total length of
the injection zone. Vertical wells can be fractured in a single stage or multiple stages while horizontal
wells typically require multiple stages due to the overall length of the horizontal leg (GWPC and ALL
Consulting, 2009). In a multi-stage fracture of a horizontal well, the fracturing operation typically begins
with the stage furthest from the wellhead until the entire length of the horizontal leg 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, 2009). 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, 2009). 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, 2009).
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, 2009). Microseismic monitoring is used in about three percent of fracturing jobs (Zoback et
al., 2010).
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6.3.1.3 NATURALLY OCCURRING SUBSTANCES
Hydraulic fracturing may 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.
TABLE 5. NATURALLY OCCURRING SUBSTANCES THAT MAY BE FOUND IN HYDROCARBON-CONTAINING
FORMATIONS
Type of Contaminant
Formation fluid
Gases
Trace elements
Naturally occurring
radioactive material
Organic material
Example(s)
Brine3
Natural gasb (e.g., methane, ethane), carbon dioxide,
hydrogen sulfide, nitrogen, helium
Mercury, lead, arsenic0
Radium, thorium, uranium0
Organic acids, polycyclic aromatic hydrocarbons,
volatile and semi-volatile organic compounds
Piggot and Elsworth, 1996.
b Zoback et al., 2010.
0 Harper, 2008; Leventhal and Hosterman, 1982; Tuttle et al., 2009;
Vejahati et al., 2010.
Some or all of these substances may find a pathway to USDWs as a result of hydraulic fracturing
activities. 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, these
potential contaminants could migrate into drinking water supplies. 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). These reactions are discussed in
more detail in Section 6.3.4.
6.3.2 HOW EFFECTIVE ARE WELL CONSTRUCTION PRACTICES AT CONTAINING GASES AND FLUIDS BEFORE,
DURING, AND AFTER FRACTURING?
In researching information sources for this study plan, EPA found evidence showing that improper well
construction or improperly sealed wells may 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).
Based on these findings, EPA believes that well mechanical integrity will likely be an important factor 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
are concerns about the repeated fracturing of a well over its lifetime. Hydraulic fracturing can be
repeated as necessary to maintain the flow of gas or hydrocarbons to the well. The near- and long-term
effects of repeated pressure treatments on well components (e.g., casing, cement) are not well
understood. While EPA recognizes that fracturing or refracturing existing wells may pose a risk to
drinking water resources, EPA has not been able to identify potential partners for a case study,
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therefore, this practice is not considered in the current study. The issues of well age and maintenance,
however, are important and warrant more study.
6.3.3 WHAT ARE THE POTENTIAL IMPACTS OF PRE-EXISTING MAN-MADE OR NATURAL PATHWAYS/FEATURES
ON CONTAMINANT TRANSPORT?
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. If hydraulic fractures combine with
pre-existing faults or fractures that lead to aquifers or directly extend into aquifers, injection could lead
to the contamination of drinking water supplies by fracturing fluid, natural gas, and/or naturally
occurring substances (see Table 5).
During the fracturing process, some fracturing fluid may flow from the created fractures to other areas
within the gas-containing formation in a phenomenon known as "fluid leakoff." In the case of leakoff,
the fluid may flow into the micropore or pore spaces within the formation, existing natural factures in
the formation, or small fractures opened into the formation by the pressure in the induced fracture (API,
2009; Economides et al., 2007). Fluid leakoff during hydraulic fracturing can exceed 70 percent of the
injected volume if not controlled properly (Glenn et al., 1985), and may result in fluid migrating into
drinking water aquifers (Hess, 2010; Subra, 2010; Bielo, 2010; URS Corporation, 2009). Additionally, the
fracturing process may change the fine scale structure of the rock and alter the fluid flow properties of
the formation (Yang et al., 2004).
The risk posed by fluid leakoff to drinking water resources will depend on the distance to those
resources and the geochemical and transport processes that are occurring 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). In contrast to shale gas, coalbed methane reservoirs are mostly
shallow and may also be underground resources of drinking water. In this instance, hydraulic fracturing
may be occurring in or near an USDW, raising concerns about the contamination of shallow water
supplies with hydraulic fracturing fluids (Pashin, 2007). Some states have regulations addressing
hydraulic fracturing of this type of reservoir (GWPC and ALL Consulting, 2009).
In addition to natural faults or fractures, it is important to consider the proximity of artificial
penetrations such as drinking water wells, exploratory wells, production wells, abandoned wells
(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 USDWs. 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).
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6.3.4 WHAT CHEMICAL/PHYSICAL/BIOLOGICAL PROCESSES COULD IMPACT THE FATE AND TRANSPORT OF
SUBSTANCES IN THE SUBSURFACE?
There are numerous chemical/physical/biological processes that may alter the fate and transport of
substances in the subsurface as the result of hydraulic fracturing. These processes could increase or
decrease the mobility of these substances, depending on their properties and the complex interactions
of all 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).
Physical processes can also increase the mobility of naturally occurring substances. For example,
hydraulic fracturing itself is a physical process that may increase the mobility of methane into the
surrounding media (GWPC and ALL Consulting, 2009). In the formation, methane is trapped inside the
matrix and is not mobile because the pores within the formation are too small or are unconnected.
When the rock is fractured, the connection between the pores increases, allowing methane to flow into
the fracture and wellbore.
6.3.5 WHAT ARE THE TOXIC EFFECTS OF NATURALLY OCCURRING SUBSTANCES?
As discussed above, multiple pathways may exist that allow contaminants to reach drinking water
resources. The toxic effects of chemical additives in hydraulic fracturing fluid were briefly discussed in
Section 6.2.2. Table 5 and Table D3 in Appendix D provide examples of naturally occurring substances
that may contaminate drinking water resources. The toxicity of these substances varies considerably.
For example, naturally occurring metals, though they are 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). Research to
summarize and explore these effects is described in Chapter 8.
6.3.6 PROPOSED RESEARCH ACTIVITIES—WELL INJECTION
6.3.6.1 WELL INTEGRITY: ANALYSIS OF EXISTING DATA, CASE STUDIES, AND SCENARIO EVALUATION
Analysis of existing data: well files. As part of the voluntary request for information sent by EPA to nine
hydraulic fracturing service companies (see Appendix C), EPA asked for the locations of sites where
hydraulic fracturing operations have occurred within the past year. From this potential list of thousands
of hydraulic fracturing sites, EPA will select a representative sample of sites and request the complete
well files for these sites. Well files generally contain information regarding all activities conducted at the
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site, including any instances of well failure. EPA will analyze the well files to assess the typical causes,
frequency, and severity of well failures.
Retrospective case studies. While conducting retrospective case studies, EPA will assess the mechanical
integrity of relevant wells (e.g., 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 E. 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.
Prospective case studies. EPA will assess well construction and mechanical integrity at prospective case
study sites by:
* Assessing the integrity of wells with respect to casing and cement placement using available
logging tools and pressure tests conducted before hydraulic fracturing.
• Repeating mechanical integrity assessments on wells following hydraulic fracturing treatments
to evaluate changes related to the high pressures used in the fracturing.
• Sampling the pressure within, and the fluid from, well components (e.g., annular spaces behind
the production casing) before and after hydraulic fracturing operations.
During prospective case studies, EPA will also identify what, if any, mechanisms are used to monitor
mechanical integrity after the hydraulic fracturing event has taken place.
Scenario evaluation. Computer modeling provides a scientific approach to test potential impacts of
hydraulic fracturing well injection scenarios on drinking water resources. The models will include
engineering and geological aspects, which will be informed by existing data and laboratory experiments.
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 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 the influence of pressure response and contaminant
transport under conceptual models representing expected fracturing conditions as well as potential
modes of failure. For example, 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. In this case, it will be informative to compare typical well
construction and testing practices to unexpected situations that might affect drinking water resources.
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6.3.6.2 IMPACTS OF NATURAL AND MAN-MADE PATHWAYS: CASE STUDIES AND SCENARIO EVALUATION
Retrospective case studies. In cases of suspected drinking water contamination, EPA will investigate the
role of natural and/or artificial pathways in leading to the possible contamination through geophysical
testing, field sample analysis, and modeling. This investigation will determine the role of existing natural
or artificial pathways in providing conduits for the migration of fracturing fluid, natural gas and/or
naturally occurring substances to drinking water resources.
EPA will also review the data collected on the hydraulic fracturing process itself, including data gathered
to calculate the fracture pressure gradients in the injection zone and confining layers; data resulting
from fracture modeling, microseismic fracture mapping and tiltmeter analysis; and any other data used
to determine fracture location, length, and height. A critical assessment of these data will allow EPA to
determine if fractures created during hydraulic fracturing were localized to the injection zone or possibly
intersected existing faults or fractures, leading to the reported contamination.
Prospective case studies. The prospective case studies will give EPA a better understanding of the
processes and tools used to determine fracture location, length, and height. Additionally, EPA will
assess the impacts of natural and man-made pathways on the fate and transport of chemical
contaminants to drinking water resources by measuring water quality before, during, and after injection.
EPA is currently 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 a USDW via existing natural or man-made pathways.
Scenario evaluation. The physics-based computer modeling tools described above allow for the
exploration of scenarios in which, for example, the fracturing of the target formation unintentionally
extends outside of the target zone and potentially creates new pathways for pressure and fluid leakage.
It is also suspected that abandoned wells and natural fractures and fault zones may provide pathways
for any fluids that leave the target injection zone. 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 variances in geology and well construction, and will help to inform the
retrospective and prospective case studies.
Data and information 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 is
potentially 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
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.
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6.3.6.3 PHYSICAL/CHEMICAL/BIOLOGICAL PROCESSES RELEVANT TO HYDRAULIC FRACTURING: LABORATORY
STUDIES
Laboratory studies will be conducted to evaluate which characteristics of gas-bearing formations and
fracturing conditions (e.g., temperature and pressure) are most important in determining the potential
impact of hydraulic fracturing on drinking water resources. Chemical degradation, biogeochemical
reactions, and weathering reactions will be studied by pressurizing subsamples of cores, cuttings, or
aquifer material in temperature-controlled reaction vessels. The subsamples will then be exposed to
hydraulic fracturing fluids using either a batch or continuous flow system to simulate subsurface
reactions. After specific exposure conditions, samples will be drawn for chemical, mineralogical, and
microbiological characterization. This approach will enable the evaluation of degradation products as
well as constituents that may be mobilized from the solid phase due to biogeochemical reactions.
The laboratory studies will also help to identify possible components in flowback and produced water.
Once identified, the list of possible components can be used to identify or develop analytical methods
needed for detecting these components. Additionally, the list of possible flowback and produced water
components can be used to determine the toxicity and human health effects of naturally occurring
substances that may be released during hydraulic fracturing operations using the methods outlined in
Chapter 8.
6.3.7 POTENTIAL RESEARCH OUTCOMES
The research opportunities outlined above will allow EPA to:
• Determine the frequency and severity of well failures, as well as the factors that contribute to
them.
» Identify the key conditions that increase or decrease the likelihood of the interaction of existing
pathways with hydraulic fractures.
* Evaluate water quality before, during, and after injection.
* Determine the identity, mobility, and fate of potential contaminants, including fracturing fluid
additives and/or naturally occurring substances (e.g., formation fluid, gases, trace elements,
radionuclides, organic material) and their toxic effects.
» Develop analytical methods for detecting chemicals associated with hydraulic fracturing events.
6.4 FLOWBACK AND PRODUCED WATER: WHAT ARE THE POSSIBLE IMPACTS OF RELEASES 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; this
mixture of fluids is called "flowback." 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).
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Estimates of the amount of fracturing fluid recovered as f lowback 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, however, 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. A recent GWPC report states that none of the 27 oil and natural
gas producing states in the United States requires the volume of flowback to be reported to state
agencies (GWPC, 2009).
The initial 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, and geological formation (Veil et al., 2004). In general, analyses of
flowback from various reports show that concentrations of TDS can range from 5,000 mg/L (Horn, 2009)
to more than 100,000 mg/L (Hayes, 2009a), and may even reach 200,000 mg/L (Gaudlip and Paugh,
2008; Keister, 2009; Vidic, 2010). These high values can be reached in a matter of two weeks.
Along with high TDS values, flowback can have high concentrations of major 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 may also contain radionuclides (Zoback et al., 2010) as well as volatile organic compounds
(VOC), including benzene, toluene, xylenes, and acetone (URS Corporation, 2009). A list of chemicals
identified in flowback and produced water can be found in Table D2 in Appendix D. 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 through time of TDS, chloride, barium, and calcium; water hardness; and levels of
radioactivity (URS Corporation, 2009).
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). In areas of New York overlying the Marcellus Shale, regulators are reviewing double-lined
centralized impoundments ranging in capacity from 1 to 16 million gallons for the storage of flowback
that serve well pads within a 4-square-mile area (ICF International, 2009b; NYSDEC, 2009). The
transportation of flowback and produced water for disposal depends on site-specific conditions. In the
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Marcellus Shale, for example, if the disposal area is not located nearby, flowback and produced water
are trucked to disposal facilities (ICF International, 2009a).
The storage of flowback and produced water in tanks or impoundment pits is regulated in many oil and
gas producing states (GWPC, 2009). According to the GWPC, 81 percent of these states require tanks for
the storage of flowback and produced water to be surrounded by a containment dike. Five states,
however, require that materials used to construct storage tanks be compatible and of sufficient strength
to hold flowback and produced water. If flowback and produced water is contained in pits, 18 of the 27
states studied require a permit for the pit while 23 states require liners in pits and 16 limit the duration
of their use. For example, New York limits the duration fluids can be stored in pits on-site to 45 days
after the fracturing treatment (unless reuse has been approved). When liners are used, some states
require interstitial monitoring for leaks while others do not.
6.4.2 WHAT is THE COMPOSITION AND VARIABILITY OF FLOWBACK AND PRODUCED WATER AND WHAT ARE
THE TOXIC EFFECTS OF THESE CONSTITUENTS?
Much of the existing data on the composition of flowback and produced water focuses on the detection
of major ions in additional to pH and TDS measurements. For example, data provided by the USGS
produced water database indicates 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). However, less is known about the composition and variability of flowback and
produced water with respect to the chemical additives found in hydraulic fracturing fluid or radioactive
materials. A recent report by the Gas Technology Institute offers a fairly extensive analysis of the
constituents found in flowback in several wells in the Marcellus Shale (Hayes, 2009b). Veil (2004) also
provides data for several organic compounds in produced water. It is unclear, however, how the
chemical composition of flowback varies on both the national and local scales.
A thorough understanding of how the composition of flowback and produced water varies at both the
local and national scales could lead to improved predictions of the identity and toxicity of chemical
additives and naturally occurring substances in flowback and produced water. The toxicity of these
substances is discussed above in Sections 6.2.2 and 6.3.5.
6.4.3 WHAT FACTORS MAY INFLUENCE THE LIKELIHOOD OF CONTAMINATION OF DRINKING WATER
RESOURCES?
There may be opportunities for the contamination of drinking water resources both below and above
ground. If the mechanical integrity of the well has been compromised, flowback and produced water
traveling up the wellbore may 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. There are also concerns associated with the design,
construction, operation, and closure of waste impoundment pits.
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6.4.4 HOW EFFECTIVE ARE MITIGATION APPROACHES IN REDUCING IMPACTS TO DRINKING WATER
RESOURCES?
Standard management practices for the industry recommend that spills be cleaned up and disposed of,
or reused, to protect human health and the environment. If applicable, these efforts should be pursued
in compliance with existing federal and state regulations (USEPA, 2002a). As in the case of accidental
releases associated with chemical mixing, it is unclear what practices are used on-site to prevent,
contain, or mitigate accidental releases of flowback and produced water. EPA is interested in gathering
information relating to the current on-site management practices that are used to prevent and/or
contain accidental releases of flowback and produced water to drinking water resources.
6.4.5 PROPOSED RESEARCH ACTIVITIES—FLOWBACK AND PRODUCED WATER
6.4.5.1 COMPOSITION AND VARIABILITY OF FLOWBACK AND PRODUCED WATER: ANALYSIS OF EXISTING
DATA AND PROSPECTIVE CASE STUDIES
Analysis of existing data. EPA requested data on the amounts and management of flowback and
produced water in the information request sent to the nine hydraulic fracturing service companies
(Appendix C). As noted above, a comprehensive chemical analysis of flowback at several wells in the
Marcellus Shale is available (Hayes, 2009b) as well as information on potential constituents in produced
water (Veil et al., 2004). In addition, the New York State Department of Environmental Conservation
reported on the constituents in samples of flowback and produced water (NYSDEC, 2009). These and
other data EPA can locate will be used to enhance our current understanding of the composition and
variability of flowback and produced water, which will allow EPA to identify or develop analytical
methods needed to detect potential chemicals of concern (e.g., fracturing fluid additives, metals, and
radionuclides) in hydraulic fracturing wastewaters. These data will also be used to identify the toxic
effects of hydraulic fracturing wastewaters, as described in Chapter 8.
Prospective case studies. EPA will monitor current management practices associated with flowback and
produced water, and will also draw samples as part of the full water lifecycle monitoring at sites. At the
case study 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.
The analysis of flowback and produced water collected during prospective case studies will be done in
coordination with DOE NETL NETL is currently studying the fate and biogeochemistry of radionuclides
and VOCs that may appear in flowback and produced water during unconventional oil and natural gas
development projects. In addition, DOE NETL has an ongoing project to identify the isotopic signature of
Marcellus flowback and produced water. The objective of this project is to determine if stable isotopes
can be used to identify Marcellus flowback and produced water when commingled with surface waters
or shallow ground water (such as in a surface spill or casing leak scenario); if successful, this is also a
technique that EPA may use in retrospective case studies.
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6.4.5.2 FLOWBACK AND PRODUCED WATER RELEASE: ANALYSIS OF EXISTING DATA, RETROSPECTIVE CASE
STUDIES, AND SCENARIO EVALUATIONS
Analysis of existing data. There is a chance for flowback and produced water to be released once at the
surface, either due to failure at the pipeline or failure of the waste pit or storage tank. Chemical spills
and wastewater leakage from waste pits have been studied extensively for other types of wastes. EPA
will take advantage of the existing scientific literature by reviewing it for situations that may be similar
to hydraulic fracturing operations. To accomplish this, EPA will use the list of constituents identified in
flowback and produced water to determine chemicals and classes of chemicals for review in the existing
literature. The relevant research will be summarized to determine the fate and transport of flowback
and produced water constituents. This literature review will allow EPA to summarize the known impacts
of releases of flowback and produced water on drinking water resources and to identify existing
knowledge gaps related to surface releases of flowback and produced water.
Retrospective case studies. There are several candidate sites where surface releases of flowback and/or
produced water have occurred from spills, blowouts, and leaking pits. Case studies will examine the
extent of the impacts, if any, from these releases on surface and ground water resources.
Scenario evaluation. Computer modeling will provide a scientific approach for testing the potential
impacts of hydraulic fracturing flowback and produced water on drinking water resources. The
conceptual model for representative geology remains the same as in the case of injected fluids, but the
reservoir production and engineering changes from injection to extraction. An important exposure
pathway to consider is the long-term movement of injected chemicals, formation fluids, and/or
transformation products of the mixture up an improperly cemented section of the borehole or casing.
Again, it will be informative to compare the typical management practices to unexpected situations that
may lead to impacts of flowback and produced water on drinking water resources.
6.4.5.3 FLOWBACK AND PRODUCED WATER MANAGEMENT: PROSPECTIVE CASE STUDIES
Prospective case studies. EPA will collect data on the on-site handling of flowback and produced water,
including the monitoring of storage pits and the potential for leakage of flowback and produced water
to the subsurface from lined and unlined pits. When surface pits or storage tanks are used on-site, EPA
will sample their contents. When the pits are closed and abandoned, core samples will be taken
beneath the pits to confirm adequate containment of wastes. Information will also be collected on the
ways in which wastewater is transported for treatment or disposal and on the efficacy of various forms
of on-site treatment (e.g., biocides) in reducing levels of key contaminants.
6.4.6 POTENTIAL RESEARCH OUTCOMES
Through the research activities outlined, EPA will:
» Compile information on the identity, quantity, and toxicity of flowback and produced water
components.
• Develop analytical methods to identify and quantify flowback and produced water components.
• Provide a prioritized list of components requiring future studies relating to toxicity and human
health effects.
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» Determine the likelihood that surface spills will result in the contamination of drinking water
resources.
« Evaluate risks posed to drinking water resources by current methods for on-site management of
wastes produced by hydraulic fracturing.
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
Flowback and produced water can be managed through disposal or treatment, which may then be
followed by discharge to surface water bodies or reuse. Land disposal and discharge to surface waters
without treatment pose environmental and legal problems. Underground injection is the primary
method for disposal in all the major gas shale plays, except the Marcellus Shale (Horn, 2009; Veil, 2007
and 2010). Underground injection, however, can be problematic because of insufficient capacity and
the costs of trucking the wastewaterto an injection site (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 industrial treatment facilities may be an option for
some operations. Many commercial wastewater treatment facilities are designed to treat the known
constituents in flowback or produced water. POTWs, however, are not designed to treat hydraulic
fracturing wastewaters; large quantities of sodium and chloride are detrimental to digesters and can
result in high TDS concentrations in the effluent (Veil, 2010; West Virginia Water Research Institute,
2010). This high TDS water can be corrosive and 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, which have
significant health concerns associated with them. When POTWs are used, there may be strict limits on
the volumes permitted, such as those found in Pennsylvania where 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).
A primary goal of treatment for shale gas flowback is to meet current water quality standards, which
largely focus on TDS levels. Some treatment options include reverse osmosis systems, distillation,
filtration, and precipitation processes (West Virginia Water Research Institute, 2010). Reverse osmosis
systems, which have been adapted for use with oilfield wastewater, are viable for influents with TDS
concentrations of about 40,000 to 50,000 mg/L (e.g., Stepan et al., 2010), making them unsuitable for
some extremely concentrated flowback waters. Thermal distillation systems such as mechanical vapor
recompression evaporation have been developed (e.g., Veil, 2008). Thermal and reverse osmosis
systems are both subject to fouling from organic compounds, necessitating some form of pretreatment.
Horn (2009) describes a treatment train using settling and filtration, followed by an advanced oxidation
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process to remove organics. This sequence prepares the water for salt separation (such as by reverse
osmosis).
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). Water treated on site may also be used for irrigation or livestock (Horn,
2009) in addition to fracturing other wells. Given the logistical and financial benefits to be gained from
treatment of flowback water, continued developments in on-site treatment technologies are expected.
Regulations and practices for management and disposal of hydraulic fracturing wastes vary by region
and state, and are influenced by the stage of infrastructure development as well as geology, climate,
and formation composition.
6.5.2 HOW EFFECTIVE ARE TREATMENT AND DISPOSAL METHODS?
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 health
impacts on populations and ecosystems. While recycling and reuse is also an effective approach for
dealing with these waters, and at the same time conserves fresh water resources, ultimately there will
still be a need to treat and properly dispose of the final concentrated volumes from a given area of
operation. The separation and appropriate disposal of the toxic constituents is the most protective
approach for reducing potential adverse health impacts. However, much is unknown about the efficacy
of current treatment processes for adequately 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 wastewaters—and their subsequent disposal—warrants more study.
In particular, bromide and chloride can have significant impacts to downstream drinking water utilities.
Hydraulic fracturing streams can have very high levels of both, and other waters such as wastewater and
river water may offer only limited ability to dilute these constituents by blending. The presence of
bromide in source waters to drinking water systems that chlorinate will produce a greater amount of
brominated disinfection byproducts (DBPs), which have been shown to have greater health impacts than
chlorinated DBPs. 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), potentially causing a drinking water utility to exceed the current DBP regulatory limits.
Meanwhile, higher levels of chloride in drinking waters can impact lead and copper corrosion, resulting
in higher lead levels in consumer tap water and an increase in pitting incidences in copper premise
plumbing. This project will evaluate management practices for chloride and bromide in hydraulic
fracturing wastewaters, along with evaluating potential impacts to drinking water utilities and their
consumers.
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6.5.3 PROPOSED RESEARCH ACTIVITIES—WASTEWATER TREATMENT AND WASTE DISPOSAL
6.5.3.1 EFFECTIVENESS OF CURRENT TREATMENT METHODS: ANALYSIS OF EXISTING DATA, LABORATORY
STUDIES, AND PROSPECTIVE CASE STUDIES
Analysis of existing data. Important work on the treatment of flowback and produced water has been
completed by DOE NETL To optimize resources, EPA will compile the lessons learned and identify
research gaps for: (1) the impacts of the direct discharge of these waters in community wastewater
systems, (2) the effectiveness of pretreatment of these waters for ultimate discharge into a wastewater
treatment plant or for direct land application, and (3) the effectiveness of treatment of these waters for
reuse in the hydraulic fracturing industry and other industries, including agriculture. Specific emphasis
will be placed on inorganic and organic contaminants, with the latter being an area that has the least
historical information, and hence the greatest opportunity for advancement in treatment.
Laboratory studies. EPA will conduct bench-scale studies to investigate if hydraulic fracturing fluid
additives, constituents from underground formations released, or degradation products of fracturing
fluid additives are precursors to DBPs, such as trihalomethanes, haloacetic acids, or nitrosamines. EPA
will also evaluate at the bench and pilot scale whether other constituents such as elevated chloride
levels result in unintended problems (e.g., increased drinking water distribution system corrosion). The
results from these studies will inform the prospective case studies discussed below.
Prospective case studies. EPA will collect data on the efficacy of the treatment and disposal of hydraulic
fracturing wastewaters in prospective case studies 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. These studies are anticipated to
provide data on the chemical composition and concentrations found in treated hydraulic fracturing
wastewaters and in the resulting solid residuals.
6.5.4 POTENTIAL RESEARCH OUTCOMES
This research will allow EPA to:
» Evaluate current treatment and disposal methods of flowback and produced water resulting
from hydraulic fracturing activities.
• Assess the short- and long-term effects resulting from inadequate treatment of hydraulic
fracturing wastewaters.
7 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.
7.1 CASE STUDY SELECTION
EPA invited stakeholders nationwide to nominate potential case studies through informational public
meetings and the submission of electronic or written comments. Appendix F contains a list of potential
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case study sites that were nominated by stakeholders. Of the 48 nominations, EPA intends to select five
to eight sites for inclusion in the study. This will include three to five retrospective case study sites,
which will focus on cases involving possible drinking water contamination due to hydraulic fracturing
operations. The remaining two to three sites will be prospective case studies where EPA will monitor
key aspects of the hydraulic fracturing process. The final location and number of case studies will be
chosen based on the types of distinct information a given case study would be able to provide.
Table 6 outlines the systematic approach used to identify and prioritize potential retrospective and
prospective case study sites.
TABLE 6. DECISION CRITERIA FOR SELECTING HYDRAULIC FRACTURING SITES FOR CASE STUDIES
Selection Step Inputs Needed
Nomination • Planned, active, or historical
hydraulic fracturing activities
» Local drinking water resources
• Community at risk
• Site location, description,
history
« Site attributes (e.g., physical,
geology, hydrology)
• Operating and monitoring data,
including well construction and
surface management activities
• Rationale for inclusion
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)
Decision Criteria
• 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
* 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)
The criteria shown in Table 6 were used to determine the finalists for both retrospective and
prospective case studies, and represent the highest-priority case study sites that EPA would like to
conduct as part of this study. The finalists for both retrospective and prospective case study sites were
chosen to represent a wide range of conditions that reflect the 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.
Table 7 lists the finalists for retrospective case studies, highlighting the areas to be investigated and the
potential outcomes expected for each site. The potential case study sites listed in Table 7 are illustrative
of the types of situations that may be encountered during hydraulic fracturing activities and represent a
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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, as listed in Appendix F.
TABLE 7. RETROSPECTIVE CASE STUDY FINALISTS
Location
BakkenShale-Killdeer
and Dunn County, ND
Barnett Shale—Wise and
Denton Counties, TX
Marcellus Shale-
Bradford and
Susquehanna Counties,
PA
Marcellus Shale—Wetzel
County, WV; Green/
Washington Counties, PA
Areas to be Investigated
• Production well failure during
hydraulic fracturing
» Suspected drinking water aquifer
contamination
• Possible soil and surface water
contamination
• Possible drinking water well
contamination
• Spills and runoff leading to
suspected drinking water well
contamination
» Ground water and drinking water
well contamination
• Suspected surface water
contamination from a spill of
fracturing fluids
• Methane contamination of multiple
drinking water wells
• Changes in water quality in drinking
water, suspected contamination
• Stray gas in wells, spills
Raton Basin—Los Animas
County, CO
Potential Outcomes
• Identify sources of well failure
• Determine if drinking water resources
are contaminated and to what extent
• Determine if private water wells are
contaminated
« Obtain information about the likelihood
of transport of contaminants via spills,
leaks, and runoff
• Determine if drinking water wells are
contaminated
• Determine source of methane in private
wells
• Transferable results due to common
types of impacts
• Determine if drinking water wells are
contaminated
• Determine if surface spills affect surface
and ground water
• If contamination exists, determine
potential source of contaminants in
drinking water
• Determine source of methane
• Identify presence/source of
contamination in drinking water wells
• Potential drinking water well
contamination (methane and other
contaminants) in an area with
intense concentration of gas wells
in shallow surficial aquifer (coalbed
methane)
Prospective case studies will be made possible by partnering with federal and state agencies,
landowners, and industry, as highlighted in Appendix F. Potential sites for these case studies include:
• The Bakken Shale in Berthold Indian Reservation, North Dakota.
• The Barnett Shale in Flower Mound/Bartonville, Texas.
• The Marcellus Shale in Green County, Pennsylvania, or another location yet to be determined.
• The Niobrara Shale in Laramie County, Wyoming.
For each case study (retrospective and prospective), EPA will write and approve a QAPP before the start
of any new data collection, as described in Section 2.6. As discussed in the following sections, EPA will
use a tiered approach for both retrospective and prospective case studies; after each tiered activity, EPA
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will write a short summary of findings from field investigations before moving to the next activity. Upon
completion of each case study, a report summarizing key findings will be produced, peer-reviewed, and
published. The data will also be presented in a 2012 interim report and a 2014 report of results.
EPA will perform extensive sampling of relevant environmental media as part of both retrospective and
prospective case studies. Appendix G provides details on field sampling, monitoring, and analytical
methods.
7.2 RETROSPECTIVE CASE STUDIES
As described briefly in Section 5.1, retrospective case studies are focused on investigating reported
instances of drinking water contamination in areas where hydraulic fracturing events have already
occurred. Table 7 lists five finalists for the retrospective case studies. EPA will choose three to five of
these for further investigation. Each case study will address one or more of the research questions
proposed in Table 2.
The goal of each retrospective case study is to assess whether or not the reported contamination is due
to hydraulic fracturing activities. These studies will seek to use existing data and may include additional
environmental field sampling, modeling, and/or parallel laboratory investigations. Using in-house
personnel as well as contractors, EPA expects to complete key aspects of these case studies in 2012.
However, it should be noted that field studies are subject to a wide range of complex issues (e.g., site
access and stakeholder support) that must be addressed in order to complete such a study, which may
affect the completion date of these studies.
As shown in Table 8, retrospective case studies will be conducted in a tiered fashion to develop
integrated data on site history and characteristics, water resources, contaminant migration pathways
and exposure routes, and diagnostic tools to evaluate risks.
TABLE 8. APPROACH FOR CONDUCTING RETROSPECTIVE CASE STUDIES
Tier Goal Critical Path
1 Verify potential issue * Evaluate existing data and information
» Conduct site visit
« Survey stakeholders and interested parties
2 Screen to determine * Conduct additional sampling: sample wells, taps, surface water, and other
approach for detailed fluids associated with hydraulic fracturing activities (e.g., chemical tanks,
investigations holding ponds, produced water)
* Develop site conceptual model and alternative exposure hypotheses
3 Evaluate potential * Conduct geophysical testing
sources of * Perform mechanical integrity testing
contamination . install new monitoring wells
« Develop, calibrate, and test flow and transport model(s)
4 Detailed * Conduct comprehensive chemical characterization
investigations * Evaluate alternate hypotheses using the calibrated model(s)
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Retrospective case studies will begin with verifying the potential issue (Tier 1) by evaluating existing
data, conducting site visits, and interviewing stakeholders. EPA will then conduct initial screening
activities to determine what future efforts may be required for a detailed investigation of the reported
drinking water contamination. A major focus of these initial screening activities will be to identify
potential evidence of drinking water contamination and to develop hypotheses describing possible
sources of the reported contamination, including hydraulic fracturing operations as well as non-
fracturing activities. With the exposure hypotheses in mind, additional testing will be conducted to
evaluate the potential sources of contamination (see Appendix G for additional information), which will
lead to an evaluation of the validity of the exposure hypotheses.
The data collected during retrospective case studies may be used to assess the risks posed to drinking
water resources as a result of hydraulic fracturing activities. Because of this possibility, EPA will collect
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 wells, and (4) how the chemical concentrations vary over time.
7.3 PROSPECTIVE CASE STUDIES
Prospective case studies will be performed at sites where hydraulic fracturing will occur, and are made
possible by partnering with oil and natural gas companies and other stakeholders. These case studies
will be focused on the entire water lifecycle illustrated in Figure and will: (1) provide data that will be
used to inform our current understanding of processes associated with hydraulic fracturing events; and
(2) evaluate current water management practices during each stage of the water lifecycle.
Because of the need to enlist the support and collaboration of a wide array of stakeholders in these
efforts, the prospective case studies will most likely not begin until mid-to late 2011. Some preliminary
results could be available for the 2012 interim reports, but case studies of this type will likely be
completed 12 months from the start dates.
Prospective case studies will be conducted in a tiered fashion, as outlined in Table 9, and will include
field sampling, monitoring, modeling, and parallel laboratory investigations to explore the research
questions summarized in Table 2.
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TABLES. APPROACH FOR
Field Sampling Phases
Baseline
characterization of the
production well site
and areas of concern
Production well
construction
Hydraulic fracturing of
the production well
Gas production
CONDUCTING PROSPECTIVE CASE STUDIES
Critical Path
• Sample all available existing wells, catalogue depth to drinking water aquifers,
gather well logs
• Sample any adjoining surface water bodies
• Sample source water
• Install and sample a minimum of three new monitoring wells
• Sample soil gas
• Perform geophysical characterization
• Review site geology
• Develop site conceptual model
« Develop and calibrate flow system model
• Test mechanical integrity
• Resample all wells (new and existing), surface water, and soil gas
• Survey, record, and evaluate on-site management practices (e.g., pad construction)
• Sample fracturing fluids
• Resample all wells, surface water, and soil gas
• Sample flowback
• Evaluate on-site management practices (e.g., fluids management)
• Calibrate hydraulic fracturing model
• Assess model results through testing of calibrated model
• Resample all wells, surface water, and soil gas
• Survey, record, and evaluate on-site management practices
• Calibrate hydraulic fracturing model
• Assess model results through testing of calibrated model
• Sample produced water
While conducting the prospective case studies, EPA will obtain water quality, geologic, seismic, and
other data before, during, and immediately after fracturing, as discussed in Appendix G. Similarly,
monitoring will be continued during a follow-up period of approximately one year after hydraulic
fracturing has been completed. The sampling includes the opportunity for comprehensive baseline
characterization and opportunities to monitor flowback and produced water, including the storage and
treatment of these wastewaters. The data collected can then be used to test whether hydraulic
fracturing models accurately simulate changes in the formation caused by fracturing activities.
Modeling details for prospective case studies are discussed further in Appendix H.
8 CHARACTERIZATION OF TOXICITY AND HUMAN HEALTH EFFECTS
In almost all stages of the hydraulic fracturing water lifecycle, there is potential for fracturing fluids
and/or naturally occurring substances to be introduced into drinking water resources. As highlighted
throughout Chapter 6, EPA is concerned with assessing the toxicity and potential human health effects
associated with these possible drinking water contaminants. In order to do this, EPA will first obtain an
inventory of the chemicals associated with hydraulic fracturing activities (and their estimated
concentrations of occurrence), including chemicals used in hydraulic fracturing fluid and naturally
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occurring substances that may be released from subsurface formations during the hydraulic fracturing
process. EPA will also need to 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 are several hundred potential drinking water contaminants. Therefore, EPA
expects to develop a prioritized list of chemicals and, where estimates of toxicity are not otherwise
available, to conduct additional testing or quantitative health assessments for certain high-priority
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.4 At this stage, chemicals will be grouped into one of
three categories: high priority for chemicals that are potentially of concern, low priority for chemicals
that are likely to be of little concern, and unknown priority for chemicals with an unknown level of
concern. These groupings will likely be based on known toxicity or human health effects, 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 relationship (QSAR) analysis may be conducted to
obtain comparative toxicity information. A QSAR analysis uses mathematical models to predict
measures of toxicity from physical characteristics of the structure of the chemicals; it will allow EPA to
designate these chemicals as either high- or low-priority.
The second phase of this work will focus on additional testing and/or assessment of high-priority
chemicals. High-priority 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). ToxCast may also be used to establish the level of toxicity or dose-response relationships for
chemicals where some existing information on toxicity or mode of action is available. For chemicals that
QSAR analysis and high-throughput screening identify as having a high priority for assessing risk in a
semi-quantitative or quantitative mode, EPA will initially apply computational modeling (e.g., ToxPi and
computation dose-response analysis) to determine a relative estimate of toxicity. Based on these
assessments, additional testing of the highest-priority chemicals may be conducted using medium-
throughput cellular and alternative animal models (e.g., C. elegans, zebra fish, and stress response
cellular assays) together with targeted laboratory animal assays. The latter will be targeted to the
specific mode of action indicated by high- and medium-throughput assays and computational modeling.
4 These databases include the Aggregated Computational Toxicology Resources (ACToR) database, the Distributed
Structure-Searchable Toxicity (DSSTox) database, the Exposure Forecaster Database (ExpoCastDB), Health and
Environmental Research Online (HERO), the Integrated Risk Information System (IRIS), the High Production Volume
Information System (HPVIS), the Toxicity Forecaster Database (ToxCastDB), and the Toxicity Reference Database
(ToxRefDB).
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EPA may also develop chemical-specific Provisional Peer Reviewed Toxicity Values (PPRTVs) for high-
priority chemicals for which there are no existing toxicity values. PPRTVs summarize the available
scientific information about the adverse effects of a chemical and the quality of the evidence, then
ultimately derive toxicity values, such as reference doses and cancer slope factors, that can be used in
conjunction with exposure and other information to develop a risk assessment.
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. EPA may also assess how changes in source water characteristics
impact treated drinking water and associated disinfection by products.
The overall level of effort for these characterizations will depend on the amount of information
currently available in databases, the number of high-priority chemicals that warrant a more quantitative
risk assessment, and results from other study areas that identify and characterize priority contaminant
sources and exposures. 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 understanding the overall 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.
9 ENVIRONMENTAL JUSTICE
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. There are concerns that
hydraulic fracturing may adversely affect some communities that may be more likely to be exposed to
harmful chemical contaminants as a result of fracturing activities, particularly through contaminated
drinking water resources. Stakeholders have raised concerns about the environmental justice
implications of gas drilling operations, noting that people with a lower socioeconomic status may be
more likely to consent to drilling arrangements because they may not have the resources to engage with
policymakers and agencies to affect alternatives. Additionally, drilling agreements are between
landowners and well operators, implying that tenants and neighbors may have little or no input in the
decision-making process.
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To address these concerns, EPA will combine the data collected on the location of well sites within the
United States with demographic information (e.g., income and race) to screen whether hydraulic
fracturing disproportionately impacts some citizens and to identify areas for further study.
10 SUMMARY
The research outlined in this study plan will address all stages of the hydraulic fracturing water lifecycle
shown in Figure 7 and the research questions posed in Table 2. EPA will conduct the research using case
studies and generalized scenario evaluations, which will rely on data produced by a combination of the
tools listed in Section 5.3. A comprehensive program of quality assurance will be developed for all
aspects of the proposed research. Figure 9 summarizes the research activities for each stage of the
hydraulic fracturing water lifecycle, and also provides anticipated timelines for research results. Brief
summaries of how the research activities proposed in Chapter 6 will answer the fundamental research
questions appear below.
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Water Acquisition
Chemical Mixing
Well Injection
Analyze and map water quality and
quantity data
Assess impacts of cumulative water
withdrawals
I 1 Results expected for 2012
interim report
I 1 Results expected for 2014
' ' report
Results from some retrospective case
studies are expected to be completed
by 2012 with the remaining results
by 2014. Prospective case studies
will not be completed until 2014.
Retrospective Case Studies
Prospective Case Studies
- Analysis of Existing Data
Compile list of chemicals used in HF fluids
Identify possible chemical indicators and
analytical methods
Develop additional analytical methods
Review scientific literature on surface
chemical spills
Scenario Evaluations
Laboratory Studies
Characterization of Toxicity and Human Health Effects
Identify known toxicity of HF chemicals
Analyze well files
Test well failure and existing subsurface
pathway scenarios
Study reactions between HF fluids and
target formations
Identify known toxicity of naturally
occurring substances
Predict toxicity of unknown chemicals
Develop PPRTVs for chemicals of concern
FIGURE 9a. SUMMARY OF RESEARCH PROJECTS PROPOSED FOR THE FIRST THREE STAGES OF THE HYDRAULIC FRACTURING WATER LIFECYCLE
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Flowbackand Produced Water
Wastewater Treatment
and Waste Disposal
Retrospective Case Studies
Prospective Case Studies
Analysis of Existing Data
Compile list of chemicals found in flowback
and produced water
Identify or develop analytical methods
Review scientific literature on surface
chemical spills
Assess existing data on treatment and/or
disposal of HF wastewaters
Scenario Evaluations
Investigate scenarios involving contaminant
migration up the well
Laboratory Studies
Identify HF chemical constituents that
create disinfection byproducts
Evaluate potential impacts of high chloride
concentrations on drinking water utilities
Characterization of Toxicity and Human Health Effects
Identify known toxicity of HF wastewater
constituents
Predict toxicity of unknown chemicals
Develop PPRTVs for chemicals of concern
I 1 Results expected for 2012
interim report
I 1 Results expected for 2014
' ' report
Results from some retrospective case
studies are expected to be completed
by 2012 with the remaining results
by 2014. Prospective case studies
will not be completed until 2014.
FIGURE 9b. SUMMARY OF RESEARCH PROJECTS PROPOSED FOR THE LAST TWO STAGES OF THE HYDRAULIC FRACTURING WATER LIFECYCLE
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Water acquisition: How might large volume water withdrawals from ground and surface water impact
drinking water resources? By analyzing both existing data as well as data from prospective case studies,
EPA expects to be able to identify the potential impacts of large volume water withdrawals from
hydraulic fracturing operations on drinking water resources. The data will also be used in scenario
evaluations, which will simulate the cumulative effects of large volume water withdrawals under a
variety of conditions and locations, allowing EPA to better understand how these withdrawals may
impact different regions.
Chemical mixing: What are the possible impacts of releases on of hydraulic fracturing fluids on drinking
water resources? To address this question, EPA will first compile a list of chemicals used in hydraulic
fracturing fluids from public sources and the data collected from nine hydraulic fracturing service
companies. The resulting list will be used to inform a variety of proposed research projects: (1) the
identification of fracturing fluid chemical indicators and corresponding analytical methods needed for
the detection of these compounds, (2) a review of the scientific literature pertaining to surface chemical
releases, and (3) the identification of toxic and human health effects associated with hydraulic fracturing
fluid chemical additives. Case studies will necessarily rely on the results of one or more of these
research projects. Retrospective case studies will identify what, if any, impacts a reported spill of
fracturing fluid had on nearby drinking water resources. To accomplish this, the case studies may need
to use the analytical methods identified for hydraulic fracturing fluid additives that may be identified
through the information gathered from the hydraulic fracturing service companies and may also use
information provided by the scientific literature review of surface chemical spills as well as the results of
the toxicity assessments. Meanwhile, prospective case studies will monitor current chemical
management practices related to hydraulic fracturing fluids and will mostly likely track the fate and
transport of potential chemical indicators related to fracturing fluids using the identified analytical
methods.
Well injection: What are the possible impacts of the injection and fracturing process on drinking water
resources? Data from case studies and scenario evaluations will be analyzed to determine the impacts
of the injection and fracturing process on drinking water resources. Case studies will be based on a
combination of field monitoring and modeling data to determine the impacts of well construction and
mechanical integrity as well as existing natural and artificial pathways on contaminant transport to
drinking water resources. Scenario evaluations will use data obtained during case studies and will
investigate the roles of various injection and geological conditions on drinking water resource
contamination. The case studies and scenario evaluations will be informed by data on the constituents
of hydraulic fracturing fluids, laboratory studies of chemical/biological/physical processes between
those constituents and the fractured formation, and an analysis of well files. The laboratory studies will
identify degradates and reaction products of hydraulic fracturing fluid chemical additives in addition to
naturally occurring substances released from the fractured formation. Once identified, EPA will assess
the toxicity and human health effects of these potential drinking water contaminants.
Flowback and produced water: What are the possible impacts of releases offlowback and produced
water on drinking water resources? EPA will compile a list of chemical constituents found in flowback
and produced water through three sources: public data, data submitted by nine hydraulic fracturing
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service companies, and data provided through prospective case studies. The list of chemical
constituents will be used to identify and/or develop analytical methods needed for quantifying these
chemicals and to assess the toxicity and human health effects associated with the components of
flowback and produced water. EPA will assess possible impacts to drinking water resources for two
cases: (1) contaminant migration up the well and (2) surface spills of flowback and produced water.
Scenario evaluations will be used to explore contaminant migration up the well, while possible impacts
from accidental surface releases of flowback and produced water will be identified by reviewing the
existing scientific literature related to surface chemical releases or waste pit leakages with respect to the
components found in hydraulic fracturing wastewaters. EPA may address both of these cases during
retrospective case studies, which may use the analytical methods developed for flowback and produced
water constituents as well as the results of the scientific literature review. Prospective case studies will
look at current wastewater management practices to determine what approaches are used to contain or
mitigate releases. The synthesis of these different research projects will allow EPA to assess the
potential impacts of accidental releases of flowback and produced water on drinking water resources.
Wastewater treatment and waste management: What are the possible impacts of inadequate
treatment of hydraulic fracturing wastewaters on drinking water resources? EPA will analyze existing
data and data from prospective case studies to determine the overall effectiveness of current
wastewater treatment methods on removing hydraulic fracturing-related contaminants from
wastewaters as well as the composition and characteristics of solid residuals from wastewater
treatment. More specifically, EPA will use the results from laboratory studies to identify hydraulic
fracturing fluid chemical additives that may create disinfection byproducts during the treatment of
hydraulic fracturing wastewaters and to study to the potential effects of high chloride concentrations on
drinking water utilities. Together, these activities will allow EPA to assess the impacts of inadequate
treatment of hydraulic fracturing wastewaters on drinking water resources.
The results of individual research projects will be made available after undergoing a quality assurance
review. As illustrated in Figure 9, EPA anticipates that some of the research will be completed in time
for a 2012 interim report while the remaining research is expected to be completed for a 2014 report.
Both reports will synthesize the results of the research projects presented in Chapter 6 (and summarized
above) to assess the impacts, if any, of hydraulic fracturing on drinking water resources. Overall, this
study will provide data on the key factors that may be associated with the potential contamination of
drinking water resources as well as information about the toxicity of contaminants of concern. The
results may then be used to assess the potential risks to drinking water resources from hydraulic
fracturing activities.
11 AREAS OF CONCERN OUTSIDE THE SCOPE OF THIS STUDY
Although EPA's current study focuses on impacts of hydraulic fracturing on drinking water resources,
stakeholders identified additional research areas—discussed below—related to hydraulic fracturing
operations. Future work in these areas would benefit from integrating the results from the current
study to provide a holistic view of the impacts of hydraulic fracturing on human health and the
environment.
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11.1 ROUTINE 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
underground injection control (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.
11.2 AIR QUALITY
One of the largest potential sources of air emissions from hydraulic fracturing operations is the off-
gassing of methane from flowback before the well is put into production. The NYS dSGEIS estimated
that 10,200 mcf of methane is off gassed per well (ICF International, 2009a). One study in the Barnett
Shale estimated that between 1,000 and 24,000 mcf of methane is released per well (Armendariz, 2009).
This gas is typically vented or flared, although reduced emissions completion methods can capture up to
90 percent of the gas. High concentrations of methane could also pose an explosion threat. On-site fuel
tanks and impoundment pits containing flowback may also be sources of VOC and hydrogen sulfide
emissions (ICF International, 2009a). The VOCs found in flowback may include acetone, benzene,
ammonia, ethylbenzene, phenol, toluene, and methyl chloride (NYSDEC, 2009).
Truck traffic is also a potential major source of air emissions. No study has examined the specific
emissions associated with truck traffic, but the National Park Service estimated that total truck traffic of
between 300 and 1,300 trucks per well would occur in the Marcellus Shale production areas. The NPS
estimated that this could have a significant effect on regional nitrogen oxides levels (NPS, 2008). An ICF
International report written in support of the NYS dSGEIS estimated truck traffic at 330 trucks per well
(ICF International, 2009a). Emissions factors for heavy duty diesel trucks are 6.49 grams per mile
(g/mile) for nitrogen oxides, 9.52 g/mile for carbon monoxide, and 2.1 g/mile for hydrocarbons for new
trucks (USEPA, 1998). Additionally, the use of dirt roads can create dust that affects air quality.
There have been numerous reports of changes in air quality from natural gas drilling. For example, in
Battlement Mesa, Colorado, residents complained of gases and vapors from a nearby natural gas well
and state officials attributed the problem to flowback of hydraulic fracturing fluids (Webb, 2010).
Reports from Texas have linked pollutant emissions from natural gas drilling in the Barnett Shale to
substantial reductions in air quality (Michaels et al., 2010). Additionally, areas of highly concentrated
natural gas development in southwest Wyoming and eastern Utah have experienced episodes of
degraded air quality (e.g., high levels of winter time ozone concentrations). Diesel engines used to run
compressors, generators, drill rigs, and pumps may also create significant emissions.
11.3 TERRESTRIAL AND AQUATIC ECOSYSTEM IMPACTS
Hydraulic fracturing could have effects on terrestrial ecosystems unrelated to its effects on drinking
water resources. For example, chemicals used in hydraulic fracturing can contaminate soil if insufficient
care is taken during their use, transport, storage, or disposal (Zoback et al., 2010). Additionally,
wastewater impoundment pits can expose livestock and wildlife to flowback and produced water, which
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could have adverse health effects for those animals. An increase in vehicle traffic associated with
hydraulic fracturing activities may inadvertently spread invasive plants. Environmental impacts may also
occur at the drilling site and in the nearby area. During site preparation, an area must be cleared to
accommodate the wellhead(s), trucks, equipment, and other materials; access roads may need to be
built; and both the site and the roads must be prepared to support heavy equipment. All of these steps
can cause substantial disturbance to the local environment. Stakeholders have raised concerns that in
areas where many wells will be drilled, environmental impacts could include loss of green space and
habitat fragmentation.
Hydraulic fracturing could also affect aquatic ecosystems. For example, if untreated wastewater (e.g.,
from spills from well pads) is released into streams during transportation or planned releases from
wastewater treatment plants, the streams may become unsuitable habitats for fish or other aquatic
organisms that cannot tolerate high salt concentrations or the presence of other contaminants. This has
occurred in Pennsylvania, where a fish kill was linked to a spill of hydraulic fracturing fluid that
contaminated a stream (Lustgarten and ProPublica, 2009). Stormwater runoff from the drilling site may
be another water issue of concern. Appropriate management practices need to be used to control
runoff from both the site and the access roads (NYSDEC, 2009; USDOE, 2009).
11.4 SEISMIC RISKS
It has been suggested that drilling and hydraulically fracturing shale gas wells might cause low-
magnitude earthquakes. Public concern about this possibility emerged in 2008 and 2009, when the
town of Cleburne, Texas—where there had been a recent increase in drilling into the Barnett Shale-
experienced several clusters of weak earthquakes (3.3 or less on the Richter scale) for the first time in its
history. A study by University of Texas and Southern Methodist University did not find a conclusive link
between hydraulic fracturing and these earthquakes, but indicated that the injection of wastewater
from gas operations into disposal wells (the preferred means of waste disposal for natural gas
operations in the area) might have been responsible (GWPC and ALL Consulting, 2009).
11.5 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 jeopardize public safety, as well as the safety of workers. 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.
11.6 OCCUPATIONAL RISKS
The oil and gas extraction industry has an annual occupational fatality rate eight times higher than the
rate for all U.S. workers (NIOSH, 2009). The National Institute for Occupational Safety and Health
(NIOSH) reports that fatality rates increase when the level of drilling activity increases, possibly because
of an increase in the proportion of inexperienced workers, longer working hours, and the utilization of
all available equipment, including older equipment with fewer safeguards (NIOSH, 2009). Exposure
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potential and acute and chronic health effects associated with worker exposure to hydraulic fracturing
fluid chemicals should be considered, including transport, mixing, delivery, and potential accidents (e.g.,
high pressure leak, valve, pipe, or tank failure). 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.
Several types of problems can occur in conjunction with hydraulic fracturing: blowouts, chemical spills,
vehicle accidents, and exposure to fumes. These problems are particularly likely to harm workers,
although nearby people may also be affected. For example, there have been reported instances of
illnesses that may be related to hydraulic fracturing operations, including one case in which a nurse who
treated a worker exposed to hydraulic fracturing chemicals became seriously ill (Frankowski, 2008).
11.7 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, are the high-paying jobs associated with oil and gas
extraction available to local people or to those from traditional oil and gas states because specific skills
are needed for the drilling and fracturing process? There may also be an impact on local response
resources because of an increase in truck traffic or accidents at well sites. It is important to better
understand the benefits and costs of hydraulic fracturing operations.
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APPENDIX A: PROPOSED RESEARCH SUMMARY
TABLE Al. PROPOSED RESEARCH FOR WATER ACQUISITION
Water Acquisition: How might large volume water withdrawals from ground and surface water impact drinking
Secondary Question
What are the impacts on
water availability?
What are the impacts on
water quality?
Research
Analyze Existing Data
• Survey and map HF sites and water
resources
• Analyze trends in water flow and usage
patterns
« Compare areas with HF activity to areas
without
Prospective Case Studies
• Collect data on water use and the
availability of drinking water resources
near HF sites before and after water
withdrawals
• Monitor current management practices
relating to water acquisition
Scenario Evaluation
• Assess impacts of cumulative water
withdrawals on water availability at
watershed and aquifer levels
Analyze Existing Data
* Survey and map HF sites and water
quality
• Analyze trends in water quality
• Compare areas with HF activity to areas
without
Prospective Case Studies
• Collect data on the quality of drinking
water resources near HF sites before and
after water withdrawals
Potential Product(s) Year
• Maps of HF activity and drinking water 2012
resources
» Identification of impacts of HF on water
availability at various spatial and temporal
scales
Identification of impacts of HF on water 2014
availability
Assessment of current water withdrawal
management practices
Identification of impacts on drinking 2014
water resources due to cumulative water
withdrawals
Estimate of the sustainable number of HF
operations per year for a given region or
formation
Maps of HF activity and drinking water 2012
resources
Identification of impacts of HF on water
quality
Identification of impacts of HF on water 2014
quality
water resources?
Due EPA's Role
Research by ORD
(NRMRL)
Research by ORD
(NRMRL, NERL)
Research by ORD
(NERL)
Research by ORD
(NRMRL)
Research by ORD
(NRMRL, NERL)
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TABLE A2. PROPOSED RESEARCH FOR CHEMICAL MIXING
Chemical Mixing: What are the possible impacts of releases of hydraulic fracturing fluids on drinking water resources?
Secondary Question
What is the composition of
HF fluids and what are the
toxic effects of these
constituents?
What factors may influence
the likelihood of
contamination of drinking
water resources?
Research
Analyze Existing Data
• Compile list of chemicals used in HF
fluids based on publically available data
and data provided by nine HF service
companies
» Compare chemical list with databases of
known toxic chemicals
• Predict hazards in cases where toxicity is
unknown
• Identify or develop analytical methods
for detecting HF chemical additives
Analyze Existing Data
• Review existing scientific literature on
surface chemical spills with respect to HF
chemical additives
Retrospective Case Studies
* Possible investigation of an HF site
where a spill of HF fluid has been
reported
Prospective Case Studies
• Monitor and assess current chemical
management practices
Potential Product(s)
• List of chemicals used in HF (subject
to TSCA CBI rules), including
concentrations used and known
toxicity levels
• Prioritized list of chemicals requiring
further toxicity studies, including
additional screening activities
• Analytical methods for detecting HF
chemical additives, including up to
10-20 possible indicators to track
fate and transport of HF fluids
• Summary of existing research that
describes the fate and transport of
HF chemical additives
• Identify knowledge gaps for future
research, if necessary
• Identification of impacts to drinking
water resources resulting from the
accidental release of HF fluid
Year Due
2012*
EPA's Role
Research by EPA(OSP,
NERL, NCEA, NHEERL,
NCCT, OPPT)
2012
Assessment of current management
practices related to on-site chemical
storage and mixing
2012/2014
2014
Research by ORD
(NERL)
Research by ORD
(NRMRL, NERL)
Research by ORD
(NRMRL, NERL)
How effective are
mitigation approaches in
reducing impacts to
drinking water resources?
* Additional analytical methods will be developed as needed and may be available in 2014. Also available in 2014 would be predictions of the toxicity of
selected chemicals as well as the development of PPRTVs for high-priority chemicals of concern (if needed).
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TABLE A3. PROPOSED RESEARCH FOR WELL INJECTION
Well Injection: What are the possible impacts of the injection and fracturing process on drinking water resources?
Secondary Question
How effective are well
construction and operation
practices at containing
fluids during and after
fracturing?
Research
Analysis of Existing Data
« Analyze a representative selection of
well files
Retrospective Case Studies
« Investigate the cause(s) of reported
drinking water contamination, including
testing well mechanical integrity
Prospective Case Studies
* Conduct tests to assess well mechanical
integrity before and after fracturing
Scenario Evaluation
« Test various scenarios involving well
failure that may result in drinking water
contamination
Potential Product(s)
• Data on the frequency, severity, and
contributing factors leading to well
failures
« Data on the role of mechanical
integrity in suspected cases of
drinking water contamination due to
HF
» Data on changes (if any) in
mechanical integrity due to HF
« Identification of methods being used
(if any) to monitor mechanical
integrity after HF
» Identification and assessment of well
failure scenarios during well injection
that lead to drinking water
contamination
Year Due EPA's Role
2014 Research by ORD
(OSP)
2012/2014 Research by ORD
(NRMRL, NERL)
2014 Research by ORD
(NRMRL, NERL)
2012 Research by ORD
(NERL)
Table continued on next page
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February 7, 2011
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Secondary Question
What are the potential
impacts of pre-existing
man-made or natural
pathways/features on
contaminant transport?
What chemical/physical/
biological processes could
impact the fate and
transport of substances in
the subsurface?
What are the toxic effects
naturally occurring
substances?
Research
Retrospective Case Studies
* Investigate the cause(s) of reported
drinking water contamination
Prospective Case Studies
• Identify the impacts of natural and
artificial pathways on contaminant
transport
Scenario Evaluation
• Test scenarios where faults or fractures
intersect natural and artificial pathways
Laboratory Studies
• Identify relevant reactions between HF
fluid additives and naturally occurring
substances
• Determine degradation products of HF
fluid additives
• Determine important properties of gas-
bearing formations, solid residues, and
fracturing conditions that may lead to
drinking water contamination
Analysis of Data
» Compare list of naturally occurring
substances with databases of known
toxic chemicals
• Predict hazards in cases where toxicity is
unknown
Potential Product(s) Year Due
• Assessment of the role of pre- 2012/2014
existing pathways in the transport of
HF fluids, natural gas, or naturally
occurring substances to drinking
water resources
• Data on the location of hydraulic
fractures and their potential
connection to other pathways
• Identification of processes and tools 2014
used to determine fracture location
and properties
• Data on water quality before, during,
and after injection (possibly using
chemical tracers)
• Assessment of key conditions that 2012
affect the interaction of pre-existing
pathways with HF fractures
• Identification of the area of potential
impact
• Assessment of fate of HF fluid 2014
components and naturally occurring
substances
• Assessment of the identity, physical
and chemical characteristics,
mobility, and concentration of
potential drinking water
contaminants
* Compilation of information on the 2012/2014
toxicity of naturally occurring
substances
• Prioritized list of chemicals requiring
further toxicity study
• PPRTVsfor chemicals of concern
EPA's Role
Research by ORD
(NRMRL, NERL);
collaboration with
USGS
Research by ORD
(NRMRL, NERL);
collaboration with
DOE NETL
Research by ORD
(NERL)
Research by ORD
(NRMRL)
Research by EPA
(NCEA, NCCT, NHEERL,
OPPT)
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TABLE A4. PROPOSED RESEARCH FOR FLOWBACK AND PRODUCED WATER
Flowback and Produced Water: What are the possible impacts of releases offlowback and produced water on drinking water resources?
Secondary Question
What is the composition,
quantity, and variability of
flowback and produced
water and what are the
toxic effects of these
constituents?
What factors may influence
the likelihood of
contamination of drinking
water resources?
How effective are
mitigation approaches in
reducing impacts to
drinking water resources?
Research
Analysis of Existing Data
• Compile list of chemicals found in
flowback and produced water
• Compare chemical list with databases of
known toxic chemicals
• Predict hazards in cases where toxicity is
unknown
• Identify or develop analytical methods
for detecting chemicals in flowback and
produced water
Prospective Case Studies
• Sample flowback and produced water
periodically after injection is completed
Analysis of Existing Data
* Review existing scientific literature on
surface chemical spills and pit leakage
with respect to the constituents of
flowback and produced water
Retrospective Case Studies
« May investigate a case study where a
spill offlowback and produced water has
been reported
Analysis of Existing Data
• Test scenarios involving contaminant
migration up the wellbore
Prospective Case Studies
» Monitor on-site management of
flowback and produced water
Potential Product(s) Year Due
» List of identity, quantity, and known 2014
toxicity offlowback and produced
water components
• Prioritized list of chemicals for which
further toxicity studies are
warranted
• PPRTVs for chemicals of concern
• Analytical methods for quantifying
components of flowback and
produced water
• Data on the composition, quantity, 2014
and variability offlowback and
produced water and how that
composition changes with time
• Summary of existing research that 2012
describes the fate and transport of
flowback and produced water
constituents
• Identify knowledge gaps for future
research, if necessary
• Evaluate risks posed to drinking 2012/2014
water resources by the production
and management of HF wastewaters
• Assessment of key conditions that 2012
affect the migration offlowback and
produced water to aquifers
• Information on the effectiveness of 2014
existing practices for containing or
mitigating accidental releases of HF
wastewaters
EPA's Role
Research by EPA
(NRMRL, NERL, NCCT,
NCEA, NHEERL, OPPT)
Research by ORD
(NRMRL, NERL)
Research by ORD
(NERL)
Research by ORD
(NRMRL, NERL)
Research by ORD
(NERL)
Research by ORD
(NRMRL, NERL)
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TABLE A5. PROPOSED RESEARCH 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
How effective are
treatment and disposal
methods?
Research
Analysis of Existing Data
• Assess data on direct treatment, pre-
treatment, and treatment for reuse of HF
wastewaters
Laboratory Studies
« Investigate the role of HF chemical
additives in creating disinfection
byproducts during wastewater
treatment
« Identify the effects of HF wastewaters on
drinking water utilities
Prospective Case Studies
• Monitor treatment and disposal/reuse of
hydraulic fracturing wastewaters,
including solid residuals from treatment
facilities
Potential Product(s) Year Due
« Identify research gaps, focusing 2012
treatment relating of inorganic and
organic contaminants
« Information on the relative
effectiveness of various approaches
to treatment and disposal of
flowback and produced water
• Identification of HF-related 2012
chemicals that create disinfection
byproducts
• Assessment of the potential impacts
of high chloride levels on drinking
water utilities
« Data on the effectiveness of current 2014
treatment and disposal approaches
for HF wastewaters
• Identify areas for additional study
EPA's Role
Research by ORD
(NRMRL)
Research by ORD
(NRMRL)
Research by ORD
(NRMRL, NERL)
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TABLE A6. PROPOSED RESEARCH FOR ENVIRONMENTAL JUSTICE
Research
Analysis of Existing Data
Combine information on HF locations in the
United States with demographic information
(e.g., income and race)
Potential Product(s)
Ivlap of HF activity, income, and race
information
Year Due EPA's Role
2012 Research by ORD (OSP)
List of Acronyms
CBI confidential business information
HF hydraulic fracturing
NCCT National Center for Computational Toxicology
NCEA National Center for Environmental Assessment
NERL National Exposure Research Laboratory
NETL National Energy Technology Laboratory
NHEERL National Health and Environmental Effects Research Laboratory
NRMRL National Risk Management Research Laboratory
OPPT Office of Pollution Prevention and Toxics
ORD Office of Research and Development
OSP Office of Science Policy
PPRTV Provisional Peer Reviewed Toxicity Value
TSCA Toxic Substances Control Act
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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.org5 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." We
have interpreted this letter to mean that the sender supports hydraulic fracturing and does support the
need for additional study.
Table Bl provides an overall summary of the 5,521 comments received.
TABLE Bl. SUMMARY OF STAKEHOLDER COMMENTS
Stakeholder Comments
Position on Study Plan
For
Opposed
No Position
Expand Study
Limit Study
Position on Hydraulic Fracturing
For
Opposed
No Position
Percentage of
Comments
(w/ Form Letter)
18.2
72.1
9.7
8.8
0.7
75.7
11.6
12.7
Percentage of
Comments
(w/o Form Letter)
63.2
3.0
33.8
30.5
2.5
15.7
40.3
44.1
Table B2 further provides the affiliations (e.g., citizens, government, industry) associated with the
stakeholders, and indicates that the majority of comments EPA received came from citizens.
Energy Citizens is financially sponsored by API, as noted at http://energycitizens.org/ec/advocacy/content-
rail.aspx?ContentPage=About.
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TABLE B2. SUMMARY OF COMMENTS ON HYDRAULIC FRACTURING AND RELATED STUDY PLAN
Category
Association
Business association
Citizen
Citizen (form letter Energycitizens.org)
Environmental
Federal government
Lobbying organization
Local government
Oil and gas association
Oil and gas company
Political group
Politician
Private company
Scientific organization
State government
University
Water utility
Unknown
Percentage of
Comments
(w/ Form Letter)
0.24
0.69
23.47
71.22
1.10
0.07
0.04
0.62
0.09
0.38
0.16
0.18
0.78
0.02
0.13
0.24
0.02
0.56
Percentage of
Comments
(w/o Form Letter)
0.82
2.39
81.56
NA
3.84
0.25
0.13
2.14
0.31
1.32
0.57
0.63
2.71
0.06
0.44
0.82
0.06
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
Ground water
Surface water
Air pollution
Water use (source of frac water)
Flowback treatment/disposal
Public health
Ecosystem effects
Toxicity and chemical identification
Chemical fate and transport
Radioactive issues
Seismic issues
Noise pollution
Number of
Requests*
292
281
220
182
170
165
160
157
107
74
36
26
* Out of 485 total requests to expand the hydraulic fracturing study.
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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 compounds emissions from hydraulic fracturing operations and impoundments
• Wildlife habitat fragmentation
• Worker occupational health
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APPENDIX C: INFORMATION REQUEST
In September 2010, EPA issued information requests 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 whom the House Committee on Energy and Commerce requested
comment. Halliburton, Schlumberger, and BJ Services are the three largest companies operating in the
United States; the others are companies of varying size that operate in the major United States shale
plays. EPA sent a mandatory request to Halliburton on November 9, 2010, to compel Halliburton to
provide the requested information. As of December 6, 2010, all companies have committed to provide
the requested information on a rolling schedule that ended on January 31, 2011.
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
who sold them to the Company, including address and telephone numbers for any such
persons;
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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 K0c, 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
fluid injection process.
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4.
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.
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APPENDIX D: CHEMICALS IDENTIFIED IN HYDRAULIC FRACTURING FLUID AND
FLOWBACK/PRODUCED WATER
TABLE Dl. CHEMICALS FOUND IN HYDRAULIC FRACTURING FLUIDS
Chemical
[[(phosphonomethyl)imino]bis[2,l-
ethanediylnitrilobis(methylene)]]tetrakis phosphonic acid
ammonium salt
l-(phenylmethyl) quinolinium chloride
l-(phenylmethyl)-ethyl pyridinium, methyl derivatives
l,2,4-trimethylbenzene/l,3,5-trimethylbenzene
1,2-diethoxyethane
1,2-dimethoxyethane
1,4-dioxane
l,2-benzisothiazolin-2-one
1-eicosene
1-hexadecene
1-methylnaphthalene
1-octadecene
1-tetradecene
1-undecanol
1,6 hexanediamine
2-(2-butoxyethoxy)ethanol
2-(2-ethoxyethoxy)ethanol
2-(2-methoxyethoxy)ethanol
2,2'-azobis-{2-(imidazlin-2-yl)propane dihydrochloride
2,2-dibromo-3-nitrilopropionamide
2,2-dibromomalonamide
2,2',2"-nitriloethanol
2-acrylamido-2-methylpropansulphonicacid sodium salt
2-acrylethyl(benzyl)dimethylammonium chloride
2-bromo-2-nitro-l,3-propandiol
2-bromo-2-nitro-3-propanol
2-bromo-3-nitrilopropionamide
2-butoxyethanol
2-ethoxyethanol
2-ethoxyethyl acetate
2-ethoxynaphthalene
2-ethyl hexanol
2-methoxyethanol
2-methoxyethyl acetate
2-methylnaphthalene
2-methyl-quinoline hydrochloride
Use
acid corrosion inhibitor
non-ionic surfactant
foaming agent
foaming agent
surfactant
clay control, fracturing
foaming agent
foaming agent
foaming agent
biocide
microbiocide
microbiocide
biocide
foaming agent
foaming agent
foaming agent
foaming agent
foaming agent
Ref.
1
1
2,3
4,5
2
2
1
1
1
1
2
1
1
2
2
2
1
1,2,3,5
1
4
1
1
3,4
2
2,3
2,3,6
2,3
2
1
4,6
2
2
2
1
Table continued on next page
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Table continued from previous page
Chemical
2-monobromo-3-nitrilopropionamide
2-propen-l-aminium,N,N-dimethyl-N-2-propenyl-chloride,
homopolymer
2-propenoic acid, homopolymer, ammonium salt
2-propenoic acid, polymer with sodium phosphinate
2-propenoic acid, telomer with sodium hydrogen sulfite
2-propoxyethanol
2-(thiocyanomethylthio) benzothiazole
2-ethyl-3-propylacrolein
3,5,7-triaza-l-azoniatricyclo(3.3.1.13,7)decane, l-(3-
propenyl)-chloride
3-methyl-l-butyn-3-ol
4-(l,l-dimethylethyl)phenol, methyloxirane formaldehyde
polymer
4-nonylphenol polyethylene glycol ether
5-chloro-2-methyl-4-isothiazolin-3-one
acetic acid
acetic anhydride
acetone
acrolein
acrylamide
acrylamide-sodium acrylate copolymer
acrylamide-sodium-2-acrylamido-2-methylpropane
sulfonate copolymer
adipicacid
aldehyde
aliphatic acids
aliphatic alcohol polyglycol ether
aliphatic hydrocarbon (naphthalenesulfonic acid, sodium
salt, isopropylated)
alkenes
alkyl (C14-C16) olefin sulfonate, sodium salt
alkyl amines
alkyl aryl polyethoxy ethanol
alkylamine salts
alkylaryl sulfonate
alkylphenol ethoxylate surfactants
aluminum
aluminum chloride
aluminum oxide
aluminum silicate
Use
biocide
foaming agent
biocide
defoamer
biocide
acid treatment, buffer
corrosion inhibitor
biocide
gelling agent
linear gel polymer
corrosion inhibitor
surfactant
foaming agent
foaming agent
crosslinker
proppant
proppant
Ref.
5
1
1
1
1
2
1
1
1
1
3,4,5
4
3,4
1
1
1
3
5
1
1
1
1
4
1
3,4
1
1
3
1
Table continued on next page
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Table continued from previous page
Chemical
amine treated hectorite
ammonia
ammonium acetate
ammonium alcohol ether sulfate
ammonium bifluoride
ammonium bisulfite
ammonium chloride
ammonium citrate
ammonium cumene sulfonate
ammonium hydrogen difluoride
ammonium nitrate
ammonium persulfate
ammonium sulfate
ammonium thiocyanate
anionic polyacrylamide copolymer
anionic surfactants
aromatic hydrocarbons
aromatic naphtha
aromatic solvent
aromatics
asphalite
attapulgite
barium sulfate
bauxite
bentonite
benzene
benzyl chloride-quaternized tar bases, quinoline
derivatives
bis(l-methylethyl) naphthalene
bis(2-methoxyethyl)ether
bis(chloroethyl) ether dimethylcocoamine, diquaternary
ammonium salt
blastfurnace slag
borate salts
boric acid
boric oxide
butan-1-ol
butane
C12-C14-tert-alkyl ethoxylated amines
calcium carbonate
calcium chloride
Use
viscosifier
buffer
oxygen scavenger
crosslinker
breaker fluid
breaker fluid
friction reducer
friction reducer
surfactant
viscosifier
gelling agent
proppant
fluid additive
gelling agent
foaming agent
viscosifier
crosslinker
crosslinker
pH control
Ref.
1
4,5
1
7
2,3,5
1
1
1
1
2,3
3,4
1
3,4
3,4
4
2
4
3,4
2
1
1
2
1
7
2,3
1
1
4
1
1
Table continued on next page
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Chemical
calcium hydroxide
calcium magnesium phosphate
calcium oxide
carbohydrates
carbon black
carbon dioxide
carboxymethyl guar
carboxymethylhydroxypropyl guar
cationic polymer
cellulose
chlorine
chlorine dioxide
chloromethylnaphthalene quinoline quaternary amine
chromium
chrome acetate
citric acid
citrus terpenes
cocamidopropyl betaine
cocamidopropylamine oxide
coco-betaine
copper compounds
copper iodide
copper(ll) sulfate
cottonseed flour
crissanol A-55
crystalline silica
cupric chloride dihydrate
dazomet
decyldimethyl amine
diammonium peroxidisulfate
diammonium phosphate
diatomaceous earth
dibromoacetonitrile
didecyl dimethyl ammonium chloride
diesel
diethanolamine
diethylbenzene
diethyleneglycol
diethylenetriamine
diethylenetriamine penta (methylenephonic acid) sodium
salt
Use
pH control
proppant
resin
foaming agent
linear gel polymer
linear gel polymer
friction reducer
lubricant
corrosion inhibitor
crosslinker
iron control
breaker fluid
breaker fluid
proppant
biocide
breaker fluid
corrosion inhibitor
proppant
biocide
linear gel delivery
foaming agent
activator
Ref.
1
4
3,4
3
3
3,4
1
1
5
3
6,7
1
1
1
1
2,3
3,4
1
1
3,4
1
1
2,3
1
2,3
2,3
1
4,6
5
1
Table continued on next page
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Chemical
diisopropyl naphthalenesulfonic acid
dimethyl formamide
dimethyldiallylammonium chloride
dipotassium phosphate
dipropylene glycol
disodium EDTA
ditallowalkyl ethoxylated amines
D-limonene
dodecylbenzene
dodecylbenzene sulfonic acid
dodecylbenzenesulfonate isopropanolamine
D-sorbitol
EDTA copper chelate
eo-C7-C9-iso-,C8 rich-alcohols
eo-C9-ll-iso, ClO-rich alcohols
erucic amidopropyl dimethyl detaine
erythorbic acid, anhydrous
ester salt
ethane
ethanol
ethoxylated 4-tert-octylphenol
ethoxylated alcohols
ethoxylated alcohols, C6-C10
ethoxylated castor oil
ethoxylated hexanol
ethoxylated 4-nonylphenol
ethoxylated octylphenol
ethoxylated sorbitan trioleate
ethoxylated, propoxylated trimethylolpropane
ethyl lactate
ethyl octynol
ethylbenzene
ethylcellulose
ethylene glycol
ethylene glycol monobutyl ether
ethylene oxide
ethyloctynol
exxal 13
fatty acids
Use
breaker fluid, activator
foaming agent
foaming agent, non-ionic
surfactant
acid inhibitor
acid inhibitor
gelling agent
fluid additive
crosslinker/breaker fluid/
scale inhibitor
Ref.
1
4
1
4
1
1
1
1,4
1
1
1
1
3,4,5
6
6
1
1
2
4
2,3,5
1
4,6
4
1
1
1
1
1
1
4
2
2,3,6
4
1
1
1
1
Table continued on next page
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Chemical
fatty alcohol polyglycol ether surfactant
ferric chloride
ferrous sulfate, heptahydrate
fluorene
formaldehyde
formamide
formic acid
fuller's earth
fumaricacid
galactomannan
glutaraldehyde
glycerine
glycol ether
graphite
guar gum
gypsum
heavy aromatic petroleum naphtha
hemicellulase enzyme
heptane
hydrochloric acid
hydrodesulfurized kerosene
hydrofluoric acid
hydrogen peroxide
hydrotreated heavy naphthalene
hydrotreated light petroleum
hydrotreated naphtha
hydroxy acetic acid
hydroxy acetic acid ammonium salt
hydroxycellulose
hydroxyethyl cellulose
hydroxylamine hydrochloride
hydroxypropyl guar
iron
iron oxide
isobutyl alcohol
isomeric aromatic ammonium salt
isooctanol
isoparaffinic petroleum hydrocarbons
isopropanol
Use
acid treatment
gelling agent
water gelling agent
gelling agent
biocide
crosslinker
foaming agent, breaker
fluid
fluid additive
linear gel delivery, water
gelling agent
gellant
non-ionic surfactant
acid treatment, solvent
acid treatment
friction reducer
linear gel polymer
gel
linear gel polymer
emulsifier/surfactant
proppant
fracturing fluid
foaming agent/surfactant
Ref.
1
1
1
2
1
1
2,3
2,3
6,7
1,5
2,3
2,3,5
4,5
4
4
2,3,5,6
1
1
4
4,5,6
1
1
1
3
7
1
3
1
4
1
2,3,6
Table continued on next page
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Chemical
isopropylbenzene
kerosene
kyanite
lactose
light aromatic solvent naphtha
light paraffin oil
lignite
lime
magnesium aluminum silicate
magnesium chloride
magnesium nitrate
mercaptoacetic acid
metallic copper
methane
methanol
methyl isobutyl ketone
methyl tert-butyl ether
methyl-4-isothiazolin
methylene bis(thiocyanate)
methylene phosphonic acid
mica
mineral oil
mineral spirits
monoethanolamine
mullite
muriatic acid
N,N,N-trimethyl-2-[(l-oxo-2-propenyl)oxy]-ethanaminium
chloride homopolymer
N,N-dimethylformamide
N,N-dimethyl-methanamine-n-oxide
N,N-dimethyl-N-[2-[(l-oxo-2-propenyl)oxy]ethyl]-
benzenemethanaminium chloride
naphthalene
N-benzyl-alkyl-pyridinium chloride
N-cocamidopropyl-N,N-dimethyl-N-2-
hydrooxypropylsulfobetaine
n-hexane
nickel sulfate
nitrogen
nitrilotriacetamide
Use
proppant
fluid additive
gellant
biocide
biocide
iron control
acid corrosion inhibitor
gelling agent
biocide
biocide
scale inhibiter
fluid additive
friction reducer
crosslinker
proppant
acid treatment
breaker
gelling agent, non-ionic
surfactant
corrosion inhibitor
foaming agent
scale inhibiter
Ref.
1
1
1
1
1
4
4
4
2,3,5,6
4
2
3,4
7
1
2,3
7
1
7
1
1
2,5,6
1
1
4
3,4
Table continued on next page
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Chemical
nonylphenol polyethoxylate
organophilic clays
oxyalkylated alkylphenol
oxylated alcohol
polyaromatic hydrocarbons
pentane
petroleum distillates
petroleum grease mix
petroleum naphtha
phenolic resin
phenanthrene
pine oil
poly anionic cellulose
poly(oxy-l,2-ethanediyl)-nonylphenyl-hydroxy
polyacrylamide
polycyclic organic matter
polyethene glycol oleate ester
polyethoxylated alkanol
polyethylene glycol
polyglycol ether
polyhexamethylene adipamide
polyoxyethylene sorbitan monooleate
polyoxylated fatty amine salt
polypropylene glycol
polysaccharide
polyvinyl alcohol
potassium acetate
potassium aluminum silicate
potassium borate
potassium carbonate
potassium chloride
potassium formate
potassium hydroxide
potassium metaborate
potassium persulfate
potassium sorbate
propan-2-ol
propane
propanol
propargyl alcohol
Use
gelling agent/bactericide
proppant
biocide
acid corrosion inhibitor,
non-ionic surfactant
friction reducer
gelling agent/bactericide
foaming agent
resin
lubricant
fluid additive
pH control
brine carrier fluid
crosslinker
fluid additive
acid corrosion inhibitor
crosslinker
acid corrosion inhibitor
Ref.
1
1
1
4
2,3
4
4
4
1
2,3
1
4
2,3,5
3,7
2,3
1
1
4,6
2,3
1
1
1
4
1
5,7
2,3
1
2,3
4
1
2,3,5
4
5
2,3,6
Table continued on next page
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Chemical
propylene
propylene glycol monomethyl ether
pyridinium,l-(phenylmethyl)-, Et Me derivs., chlorides
quartz sand
quaternary ammonium compounds
raffinates (petroleum)
salts of alkyl amines
silica
sodium 1-octanesulfonate
sodium acetate
sodium acid polyphosphate
sodium aluminum phosphate
sodium benzoate
sodium bicarbonate
sodium bisulfate
sodium bromate
sodium bromide
sodium carbonate
sodium carboxymethylcellulose
sodium chloride
sodium chlorite
sodium chloroacetate
sodium citrate
sodium dichloro-s-triazinetrione
sodium erythorbate
sodium glycolate
sodium hydroxide
sodium hypochlorite
sodium ligninsulfonate
sodium mercaptobenzothiazole
sodium nitrate
sodium nitrite
sodium metaborate octahydrate
sodium perborate tetrahydrate
sodium persulfate
sodium polyacrylate
sodium sulfate
sodium tetraborate decahydrate
sodium thiosulfate
sodium a-olefin sulfonate
sorbitan monooleate
Use
corrosion inhibitor
proppant
corrosion inhibitor
foaming agent
proppant
fluid additive
breaker
pH control
fluid additive
brine carrier fluid, breaker
breaker
biocide
gelling agent
surfactant
corrosion inhibitor
fluid additive
corrosion inhibitor
concentrate
crosslinker
Ref.
1
7
1
4
2,3
7
1
1
4
1
4
1
1
7
4,5
1,5
1
1
1
1
2
1
1
1,5
4
1
1
2,3
1
1
1
Table continued on next page
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Chemical
starch blends
styrene
sucrose
sulfamicacid
sulfomethylated tannin
talc
tallow fatty acids sodium salt
terpene and terpenoids
terpene hydrocarbons
tetrachloroethylene
tetrahydro-3,5-dimethyl-2H-l,3,5-thiadiazine-2-thione
tetrakis(hydroxymethyl)phosphonium sulfate
tetramethyl ammonium chloride
tetrasodium EDTA
thioglycolicacid
thiourea
titanium
titanium dioxide
toluene
tributyl phosphate
tributyl tetradecyl phosphonium chloride
triethanolamine hydroxyacetate
triethanolamine zirconate
triethylene glycol
trimethylbenzene
trimethyl polyepichlorohydrin
tripropylene glycol methyl ether
trimethylamine hydrochloride
trimethylamine quaternized polyepichlorohydrin
trisodium nitrilotriacetate
trisodium ortho phosphate
urea
vermiculite
vinylidene chloride
water
xanthum gum
xylenes
zinc
zinc carbonate
Use
fluid additive
proppant
fluid additive
acid corrosion inhibitor
crosslinker
proppant
gelling agent
defoamer
crosslinker
fracturing fluid
viscosifier
lubricant
water gelling agent/
foaming agent
corrosion inhibitor
gelling agent
lubricant
corrosion inhibitor
Ref.
3
1
1
4
3,4
1
1
1
1
1
1
1
1
1
2,3
3
2
1
1
5
4
4
4
1
1
1
1
1
2
2
Table continued on next page
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Table continued from previous page
Chemical
zirconium complex
zirconium nitrate
zirconium oxychloride
zirconium sulfate
zirconium, tetrakis[2-[bis(2-hydroxyethyl)amino-
kN]ethanolato-kO]-
a-[3,5-dimethyl-l-(2-methylpropyl)hexyl]-w-hydroxy-
poly(oxy-l,2-ethandiyl)
Use
crosslinker
crosslinker
crosslinker
crosslinker
crosslinker
Ref.
4,5
2,3
2,3
1
References
1. 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.
2. 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.
3. U.S. Environmental Protection Agency. (2004). Evaluation of impacts to underground sources of
drinking water by hydraulic fracturing ofcoalbed methane reservoirs. No. EPA/816/R-04/003.
Washington, DC: U.S. Environmental Protection Agency, Office of Water.
4. Material Safety Data Sheets; EnCana Oil & Gas (USA), Inc.: Denver, CO. Provided by EnCana
upon U.S. EPA Region 8 request as part of the Pavillion, WY, ground water investigation.
5. 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.
6. Personal communication by Angela McFadden, US EPA Region 3, Philadelphia, PA.
7. Ground Water Protection Council & ALL Consulting. (2009). Modern shale gas development in
the United States: A primer. Contract DE-FG26-04NT15455. Washington, DC: United States
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.
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TABLE D2. CHEMICALS IDENTIFIED IN FLOWBACK/PRODUCED WATER
Chemical
1,1,1-trifluorotoluene
1,4-dichlorobutane
2,4,6-tribromophenol
2,4-dimethylphenol
2,5-dibromotoluene
2-butanone
2-fluorobiphenyl
2-fluorophenol
4-nitroquinoline-l-oxide
4-terphenyl-dl4
aluminum
anthracene
antimony
arsenic
barium
benzene
benzo(a)pyrene
bicarbonate
bis(2-ethylhexyl)phthalate
biochemical oxygen demand
boron
bromide
bromoform
cadmium
calcium
carbonate alkalinity
alkalinity
chloride
chlorobenzene
chlorodibromomethane
cobalt
chemical oxygen demand
copper
cyanide
dichlorobromomethane
di-n-butylphthalate
ethylbenzene
fluoride
iron
lead
lithium
magnesium
Ref.
1
1
1
2
1
2
1
1
1
1
2
2
1
2
2
2
2
1
1
1
1,2
1
1
2
2
1
2
2
1
1
1
2
1
1
2
2
1
2
2
1
2
Chemical
manganese
methyl bromide
methyl chloride
molybdenum
n-alkanes, C10-C18
n-alkanes, C18-C70
n-alkanes, C1-C2
n-alkanes, C2-C3
n-alkanes, C3-C4
n-alkanes, C4-C5
n-alkanes, C5-C8
naphthalene
nickel
nitrobenzene-d5
oil and grease
o-terphenyl
p-chloro-m-cresol
petroleum hydrocarbons
phenol
phosphorus
potassium
radium (226)
radium (228)
selenium
silver
sodium
steranes
strontium
strontium (89&90)
sulfate
sulfide
sulfite
TDS
thallium
titanium
total organic carbon
toluene
triterpanes
xylene (total)
zinc
zirconium
Ref.
2
1
1
1
2
2
2
2
2
2
2
2
2
1
2
1
2
1
2
1
1
2
2
1
1
2
2
1
1,2
1
1
1,2
1
2
1
2
2
2
2
1
Tofa/e continued on next page
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Table continued from previous page
Chemical
l,2-bromo-2-nitropropane-l,3-
diol (2-bromo-2-nitro-l,3-
propanediol or bronopol)
1,6-hexanediamine
1-3-dimethyladamantane
l-methoxy-2-propanol
2-(2-methoxyethoxy)ethanol
2-(thiocyanomethylthio)
benzothiazole
2,2,2-nitrilotriethanol
2,2-dibromo-3-
nitrilopropionamide
2,2-dibromoacetonitrile
2,2-dibromopropanediamide
2-butoxyacetic acid
2-butoxyethanol
2-butoxyethanol phosphate
2-ethyl-3-propylacrolein
2-ethylhexanol
3,5-dimethyl-l,3,5-thiadiazinane-
2-thione
5-chloro-2-methyl-4-isothiazolin-
3-one
6-methylquinoline
acetic acid
acetic anhydride
acrolein
acrylamide (2-propenamide)
adamantane
adipicacid
ammonia
ammonium nitrate
ammonium persulfate
atrazine
bentazon
benzyl-dimethyl-(2-prop-2-
enoyloxyethyl)ammonium
chloride
benzylsuccinic acid
beryllium
bis(2-ethylhexyl)phthalate
bisphenol a
Ref.
3
3
3
3
3
3
3
3
3
3
3
3
3
3
3
3
3
3
3
3
3
3
3
3
4
3
3
3
3
3
3
4
4
3
Chemical
boric acid
boric oxide
butanol
cellulose
chloromethane
chrome acetate
chromium
chromium hexavalent
citric acid
cyanide
decyldimethyl amine
decyldimethyl amine oxide
diammonium phosphate
didecyl dimethyl ammonium
chloride
diethyleneglycol
diethyleneglycol monobutyl ether
dimethyl formamide
dimethyldiallylammonium
chloride
dipropyleneglycol monomethyl
ether
dodecylbenzene sulfonic acid
eo-C7-9-iso-,C8 rich-alcohols
eo-C9-ll-iso, ClO-rich alcohols
ethoxylated 4-nonylphenol
ethoxylated nonylphenol
ethoxylated nonylphenol
(branched)
ethoxylated octylphenol
ethyl octynol
ethylbenzene
ethylcellulose
ethylene glycol
ethylene glycol monobutyl ether
ethylene oxide
ferrous sulfate heptahydrate
formamide
formic acid
fumaricacid
glutaraldehyde
glycerol
Ref.
3
3
3
3
4
3
4
3
4
3
3
3
3
3
3
3
3
3
3
3
3
3
3
3
3
3
3
3
3
3
3
3
3
3
3
3
3
Table continued on next page
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Table continued from previous page
Chemical
hydroxyethylcellulose
hydroxypropylcellulose
isobutyl alcohol (2-methyl-l-
propanol)
isopropanol (propan-2-ol)
limonene
mercaptoacidic acid
mercury
methanamine,N,N-dimethyl-,N-
oxide
methanol
methyl-4-isothiazolin
methylene bis(thiocyanate)
methylene phosphonic acid
(diethylenetriaminepenta[methyl
enephosphonic] acid)
modified polysaccharide or
pregelatinized cornstarch or
starch
monoethanolamine
monopentaerythritol
muconicacid
N,N,N-trimethyl-2[l-oxo-2-
propenyl]oxy ethanaminium
chloride
nitrazepam
nitrobenzene
n-methyldiethanolamine
oxiranemethanaminium, N,N,N-
trimethyl-, chloride,
homopolymer
phosphonium,
tetrakis(hydroxymethly)-sulfate
polyacrylamide
polyacrylate
polyethylene glycol
polyhexamethylene adipamide
polypropylene glycol
polyvinyl alcohol [alcotex 17f-h]
propane-l,2-diol
propargyl alcohol
Ref.
3
3
3
3
3
3
4
3
3
3
3
3
3
3
3
3
3
3
3
3
3
3
3
3
3
3
3
3
3
3
Chemical
pryidinium, l-(phenylmethyl)-,
ethyl methyl derivatives, chlorides
quaternary amine
quaternary ammonium compound
quaternary ammonium salts
sodium carboxymethylcellulose
sodium dichloro-s-triazinetrione
sodium mercaptobenzothiazole
squalene
sucrose
tebuthiuron
p-terphenyl
m-terphenyl
o-terphenyl
terpineol
tetrachloroethene
tetramethyl ammonium chloride
tetrasodium
ethylenediaminetetraacetate
thiourea
tributyl phosphate
trichloroisocyanuric acid
trimethylbenzene
tripropylene glycol methyl ether
trisodium nitrilotriacetate
urea
Ref.
3
3
3
3
3
3
3
3
3
3
3
3
3
3
4
3
3
3
3
3
3
3
3
3
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References
1. 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.
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 coalbed methane. Prepared for the U.S.
Department of Energy, National Energy Technology Laboratory, contract W-31-109-ENG-38.
Argonne, IL: Argonne National Laboratory. Retrieved January 20, 2011, from
http://www.netl.doe.gov/technologies/oil-gas/publications/oil_pubs/prodwaterpaper.pdf.
3. URS Operating Services, Inc. (2010, August 20). Expanded site investigation—Analytical results
report. Pavillion area groundwater investigation. Prepared for U.S. Environmental Protection
Agency, contract PO No. EP-W-05-050. 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.
Prepared for the New York State Energy Research and Development Authority, contract nos.
11169, 10666, and 11170. Albany, NY: New York State Energy Research and Development
Authority.
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TABLE D3. NATURALLY OCCURRING SUBSTANCES MOBILIZED BY FRACTURING ACTIVITIES
Chemical
aluminum
antimony
arsenic
barium
beryllium
boron
cadmium
calcium
chromium
cobalt
copper
hydrogen sulfide
iron
lead
magnesium
molybdenum
nickel
radium (226)
radium (228)
selenium
silver
sodium
thallium
thorium
tin
titanium
uranium
vanadium
yttrium
zinc
Common
Valence States
III
V,lll,-lll
V, III, 0, -III
II
II
III
II
II
VI, III
111,11
11,1
N/A
111,11
IV, II
II
VI, III
II
II
II
VI, IV, II, 0, -II
1
1
111,1
IV
IV, II, -IV
IV
VI, IV
V
III
II
Ref.
1
1
1
1
1
1
1
1
1
1
1
2
1
1
1
1
1
2
2
1
1
1
1
2
1
1
2
1
1
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.
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APPENDIX E: 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.
Under certain conditions the tool can be used to conduct a flow survey, locating points of inflow or
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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 El.
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TABLE El. COMPARISON OF TOOLS USED TO EVALUATE WELL INTEGRITY
Type of Tool Description and Application Types of Data
Acoustic devices to evaluate the
presence of cement behind the
casing
Acoustic cement
bond tools
Ultrasonic Transmit ultrasonic pulses and
transducers measure the received ultrasonic
waveforms reflected from the
internal and external casing
interfaces to survey well casing
Temperature Continuous recording of
logging temperature versus depth to
detect changes in and adjacent
to injection/production wells
Noise logging Recording of sound patterns
tool that can be correlated to fluid
movement; sound can be
detected through multiple
casings
Pressure tests Check for leaks in 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
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
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
Fluid movement within channels in cement in the
casing/borehole annulus
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 F: STAKEHOLDER-NOMINATED CASE STUDIES
This appendix lists the stakeholder-nominated case studies. Potential retrospective case study sites can be found in Table Fl, while
potential prospective case study sites are listed in Table F2.
TABLE Fl. POTENTIAL RETROSPECTIVE CASE STUDY SITES
Formation
Bakken Shale
Barnett Shale
Barnett Shale
Barnett Shale
Location
Killdeer and
Dunn Co., ND
Alvord, TX
Azle, TX
Decatur, TX
Key Areas to be Addressed
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
Benzene in water well
Skin rash complaints from
contaminated water
Skin rash complaints from
drilling mud applications to
land
Key Activities
Monitoring wells to evaluate
extent of contamination of
aquifer; soil and surface water
monitoring
Potential Outcomes
Determine extent of
contamination of drinking water
resources; identify sources of
well failure
Partners
NDDMR-
Industrial
Commission, EPA
Region 8,
Berthold Indian
Reservation
RRCTX,
landowners,
USGS, EPA
Region 6
RRCTX,
landowners,
USGS, EPA
Region 6
RRCTX,
landowners,
USGS, EPA
Region 6
Table continued on next page
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Formation
Barnett Shale
Barnett Shale
Barnett Shale
Barnett Shale
Clinton
Sandstone
Location
Wise/Denton
Cos. (including
Dish),TX
South Parker
Co. and
Weatherford,
TX
Tarrant Co., TX
Wise Co. and
Decatur, TX
Bainbridge,
OH
Key Areas to be Addressed
Potential drinking water well
contamination; surface spills;
waste pond overflow;
documented air contamination
Hydrocarbon contamination in
multiple drinking water wells;
may be from faults/fractures
from production well beneath
properties
Drinking water well
contamination; report of
leaking pit
Spills; runoff; suspect drinking
water well contamination; air
quality impacts
Methane buildup leading to
home explosion
Key Activities
Monitor other wells in area and
install monitoring wells to
evaluate source(s)
Monitor other wells in area;
install monitoring wells to
evaluate source(s)
Monitoring well
Sample wells, soils
Potential Outcomes
Determine sources of
contamination of private well
Determine source of methane
and other contaminants in
private water well; information
on role of fracture/fault
pathway from HFzone
Determine if pit leak impacted
underlying ground water
Determine sources of
contamination of private well
Partners
RRCTX, TCEQ,
landowners, City
of Dish, USGS,
EPA Region 6,
DFW Regional
Concerned
Citizens Group,
North Central
Community
Alliance, Sierra
Club
RRCTX,
landowners,
USGS, EPA
Region 6
RRCTX,
landowners,
USGS, EPA
Region 6
RRCTX,
landowners,
USGS, EPA
Region 6,
Earthworks Oil &
Gas
Accountability
Project
OHDNR, EPA
Region 5
Table continued on next page
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Formation
Fayetteville
Shale
Fayetteville
Shale
Fayetteville
Shale
Haynesville
Shale
Haynesville
Shale
Haynesville
Shale
Marcellus
Shale
Marcellus
Shale
Location
Arkana Basin,
AR
Conway Co.,
AR
Van Buren or
Logan Cos., AR
Caddo Parish,
LA
DeSoto Parish,
LA
Harrison Co.,
TX
Bradford Co.,
PA
Clearfield Co.,
PA
Key Areas to be Addressed
General water quality concerns
Gray, smelly water
Stray gas (methane) in wells;
other water quality
impairments
Drinking water impacts
(methane in water)
Drinking water reductions
Stray gas in water wells
Drinking water well
contamination; surface spill of
HF fluids
Well blowout
Key Activities
Monitoring wells to evaluate
source(s)
Monitoring wells to evaluate
water availability; evaluate
existing data
Soil, ground water, and surface
water sampling
Potential Outcomes
Evaluate extent of water well
contamination and if source is
from HF operations
Determine source of drinking
water reductions
Determine source of methane in
private wells
Partners
AROGC, ARDEQ,
EPA Region 6
AROGC, ARDEQ,
EPA Region 6
AROGC, ARDEQ,
EPA Region 6
LGS, USGS, EPA
Region 6
LGS, USGS, EPA
Region 6
RRCTX,
landowners,
USGS, EPA
Region 6
PADEP,
landowners, EPA
Region 3,
Damascus
Citizens Group,
Friends of the
Upper Delaware
PADEP, EPA
Region 3
Table continued on next page
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Formation
Marcellus
Shale
Marcellus
Shale
Marcellus
Shale
Marcellus
Shale
Marcellus
Shale
Marcellus
Shale
Location
Dimock,
Susquehanna
Co., PA
GibbsHill, PA
Hamlin
Township and
McKean Co.,
PA
Hickory, PA
Hopewell
Township, PA
Indian Creek
Watershed,
WV
Key Areas to be Addressed
Contamination in multiple
drinking water wells; surface
water quality impairment from
spills
On-site spills; impacts to
drinking water; changes in
water quality
Drinking water contamination
from methane; changes in
water quality
On-site spill; impacts to
drinking water; changes in
water quality; methane in
wells; contaminants in drinking
water (acrylonitrile, VOCs)
Surface spill of HF fluids; waste
pit overflow
Concerns related to wells in
karst formation
Key Activities
Soil, ground water, and surface
water sampling
Evaluate existing data;
determine need for additional
data
Soil, ground water, and surface
water sampling
Sample pit and underlying soils;
sample nearby soil, ground
water, and surface water
Potential Outcomes
Determine source of methane in
private wells
Evaluate extent of large surface
spill's impact on soils, surface
water, and ground water
Determine source of methane in
community and private wells
Evaluate extent of large surface
spill's impact on soils, surface
water, and ground water
Partners
PADEP, EPA
Region 3,
landowners,
Damascus
Citizens Group,
Friends of the
Upper Delaware
PADEP,
landowner, EPA
Region 3
PADEP, EPA
Region 3,
Schreiner Oil &
Gas
PADEP,
landowner, EPA
Region 3
PADEP,
landowners, EPA
Region 3
WVOGCC, EPA
Region 3
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Formation
Marcellus
Shale
Marcellus
Shale
Marcellus
Shale
Marcellus
Shale
Marcellus
Shale
Marcellus
Shale
Piceance
Basin
Location
Lycoming Co.,
PA
Monongahela
River Basin, PA
Susquehanna
River Basin, PA
and NY
Tioga Co., NY
Upshur Co.,
WV
Wetzel Co.,
WV, and
Washington/
Green Cos., PA
Battlement
Mesa, CO
Key Areas to be Addressed
Surface spill of HF fluids
Surface water impairment
(high IDS, water availability)
Water availability; water
quality
General water quality concerns
General water quality concerns
Stray gas; spills; changes in
water quality; several
landowners concerned about
methane in wells
Water quality and quantity
concerns
Key Activities
PADEP sampled soils, nearby
surface water, and two nearby
private wells; evaluate need for
additional data collection to
determine source of impact
Data exists on water quality
over time for Monongahela
River during ramp up of HF
activity; review existing data
Assess water use and water
quality overtime; review
existing data
Soil, ground water, and surface
water sampling
Potential Outcomes
Evaluate extent of large surface
spill's impact on soils, surface
water, and ground water
Assess intensity of HF activity
Determine if water withdrawals
for HF are related to changes in
water quality and availability
Determine extent of impact
from spill of HF fluids associated
with well blowout and other
potential impacts to drinking
water resources
Partners
PADEP, EPA
Region 3
USAGE, USGS,
EPA Region 3
USGS may do a
study here as
well
NYDEP, EPA
Region 2,
Earthworks
WVOGCC, EPA
Region 3
WVDEP,
WVOGCC,
PADEP, EPA
Region 3,
landowners,
Damascus
Citizens Group
COGCC,
landowners, EPA
Region 8
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Formation
Piceance
Basin (tight
gas sand)
Piceance
Basin
Piceance
Basin
Powder River
Basin (CBM)
San Juan
Basin
(shallow CBM
and tight
sand)
Raton Basin
(CBM)
Raton Basin
(CBM)
Location
Garfield Co.,
CO (Mamm
Creek area)
Rifle, CO
Silt, CO
Clark, WY
LaPlata Co.,
CO
Huerfano Co.,
CO
Las Animas
Co., CO
Key Areas to be Addressed
Drinking water well
contamination; changes in
water quality; water levels
Water quality and quantity
concerns
Water quality and quantity
concerns
Drinking water well
contamination
Drinking water well
contamination, primarily with
methane (area along the edge
of the basin has large methane
seepage)
Drinking water well
contamination; methane in
well water; well house
explosion
Concerns about methane in
water wells
Key Activities
Soil, ground water, and surface
water sampling; review existing
data
Monitoring wells to evaluate
source(s)
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
Monitoring wells to evaluate
source of methane and
degradation in water quality
Potential Outcomes
Evaluate source of methane and
degradation in water quality
basin-wide
Evaluate extent of water well
contamination and if source is
from HF operations
Evaluate extent of water well
contamination and determine if
HF operations are the source
Evaluate extent of water well
contamination and determine if
HF operations are the source
Partners
COGCC,
landowners, EPA
Region 8,
Colorado League
of Women
Voters
COGCC,
landowners, EPA
Region 8
COGCC,
landowners, EPA
Region 8
WOOGC, EPA
Region 8,
landowners
COGCC, EPA
Region 8, BLM,
San Juan Citizens
Alliance
COGCC, EPA
Region 8
COGCC,
landowners, EPA
Region 8
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Formation
Raton Basin
(CBM)
Tight gas
sand
Tight gas
sand
Tight gas
sand
Location
North Fork
Ranch, Las
Animas Co.,
CO
Garfield Co.,
CO
Pavillion, WY
Sublette Co.
WY(Pinedale
Anticline)
Key Areas to be Addressed
Drinking water well
contamination; changes in
water quality and quantity
Drinking water and surface
water contamination;
documented benzene
contamination
Drinking water well
contamination
Drinking water well
contamination (benzene)
Key Activities
Monitoring wells to evaluate
source of methane and
degradation in water quality
Monitoring to assess source of
contamination
Monitoring wells to evaluate
source(s) (ongoing studies by
ORDand EPA Region 8)
Monitoring wells to evaluate
source(s)
Potential Outcomes
Evaluate extent of water well
contamination and determine if
HF operations are the source
Determine if contamination is
from HF operations in area
Determine if contamination is
from HF operations in area
Evaluate extent of water well
contamination and determine if
HF operations are the source
Partners
COGCC,
landowners, EPA
Region 8
COGCC, EPA
Region 8,
Battlement
Mesa Citizens
Group
WOGCC, EPA
Region 8,
landowners
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
Bakken Shale
Barnett Shale
Marcellus
Shale
Marcellus
Shale
Marcellus
Shale
Niobrara
Shale
Woodford
Shale or
Barnett Shale
Location
Berthold Indian
Reservation, ND
Flower Mound/
Bartonville, TX
Otsego Co., NY
TBD, PA
Wyoming Co, PA
La ramie Co. ,WY
OKorTX
Potential Outcomes
Baseline water quality data, comprehensive monitoring
and modeling of water resources during all stages of the
HF process
Baseline water quality data, comprehensive monitoring
and modeling of water resources during all stages of the
HF process
Baseline water quality data, comprehensive monitoring
and modeling of water resources during all stages of the
HF process
Baseline water quality data, comprehensive monitoring
and modeling of water resources during all stages of the
HF process in a region of the country experiencing
intensive HF activity
Baseline water quality data, comprehensive monitoring
and modeling of water resources during all stages of the
HF process
Baseline water quality data, comprehensive monitoring
and modeling of water resources during all stages of the
HF process, potential epidemiology study by Wyoming
Health Department
Baseline water quality data, comprehensive monitoring
and modeling of water resources during all stages of the
HF process
Partners
NDDMR-lndustrial Commission, University
of North Dakota, EPA Region 8, Berthold
Indian Reservation
NDDMR-lndustrial Commission, EPA Region
8, Mayor of Flower Mound
NYSDEC; Gastem, USA; others TBD
Chesapeake Energy, PADEP, others TBD
DOE, PADEP, University of Pittsburgh,
Range Resources, USGS, landowners, EPA
Region 3
WOGCC, Wyoming Health Department,
landowners, USGS, EPA Region 8
OKCC, landowners, USGS, EPA Region 6
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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 United States Department of Energy
EPA United States Environmental Protection Agency
HF Hydraulic fracturing
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
USAGE United States Army Corps of Engineers
USGS United States 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: 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
7. 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 Gl 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 Gl. MONITORING AND MEASUREMENT
Sample Type
Surface and ground
water (e.g., existing
wells, new wells)
Soil/sediments, soil
gas
Case Study Site
Prospective and
retrospective (collect as
much historical data as
available)
Flowback and
produced water
Prospective
Drill cuttings, core
samples
Prospective
PARAMETERS AT CASE STUDY SITES
Parameters
• 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)
• 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
• Metals
* Radionuclides
• Mineralogic analyses
Table Gl 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 (see Appendix E). 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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FIGURE Gl. BOMB SAMPLER
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 Gl) with a double-valve configuration that activates a series of stainless steel sampling vessels to
collect pressurized ground water in one sampling pass.
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
analyzed 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
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 G2 briefly discusses the types of analytical instrumentation that can be applied to samples
collected during field investigations (both retrospective and prospective case studies).
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TABLE G2. OVERVIEW OF ANALYTICAL INSTRUMENTS THAT CAN BE USED TO IDENTIFY AND QUANTIFY
CONSTITUENTS ASSOCIATED WITH HYDRAULIC FRACTURING ACTIVITIES
Type of Analyte
Volatile organics
Water-soluble organics
Unknown organic compounds
Metals, minerals
Transition metals, isotopes
Redox-sensitive metal species,
oxyanion speciation, thioarsenic
speciation, etc.
Ions (charged elements or
compounds)
Analytical Instrument(s)
GC/MS: gas chromatograph/mass spectrometer
GC/MS/MS: gas chromatograph/mass spectrometer/
mass spectrometer
LC/MS/MS: liquid chromatograph/mass
spectrometer/mass spectrometer
LC/TOF: liquid chromatograph/time-of-flight mass
spectrometer
ICP: inductively coupled plasma
GFAA: graphite furnace atomic absorption
ICP/MS: inductively coupled plasma/mass spectrometer
LC/ICP/MS: liquid chromatograph/inductively coupled
plasma/mass spectrometer
1C: ion chromatograph
MDL Range*
0.25-10 ug/L
0.01-0.025 ug/L
5 ug/L
1-100 ug/L
0.5-1 ug/L
0.5-10 ug/L
0.5-10 ug/L
0.1-lmg/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 G3.
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TABLE G3. EXAMPLES OF MATRIX INTERFERENCES THAT CAN COMPLICATE ANALYTICAL APPROACHES USED TO
CHARACTERIZE SAMPLES ASSOCIATED WITH HYDRAULIC FRACTURING
Type of Matrix
Example Interferences Potential Impacts on Chemical Analysis
Interference
Chemical • Inorganics: metals, minerals, ions » Complexation or co-precipitation with analyte,
* Organics: coal, shale, impacting extraction efficiency, detection, and
hydrocarbons recovery
• Dissolved gases: methane, » Reaction with analyte changing apparent
hydrogen sulfide, carbon dioxide concentration
* pH • Impact on pH, oxidation potential, microbial growth
* Oxidation potential * 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 • Changes in chemical equilibria, solubility, and
* Dissolved and suspended solids microbial growth
* Geologic matrix « 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 time-
consuming. Therefore, the purpose of each chemical analysis will need to 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
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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,
butane, and pentane, depending on how it is formed. Table G4 illustrates different types of gas, the
constituents, and the formation process of the natural gas.
TABLE G4. TYPES OF NATURAL GASES, CONSTITUENTS, AND PROCESS OF FORMATION
Type of Natural Gas
Thermogenicgas
Biogenicgas
Constituents
Methane, ethane, propane,
butane, and pentane
Methane and ethane
Process of Formation
Geologic formation of fossil fuel
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—613C and 6D—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, 1983), Kaplan et al. (1997), Rowe and Muehlenbachs (1999), and others have summarized values
of 613C and 6D for methane, and their data show that it is often possible to distinguish methane formed
from biogenic and thermogenic processes by plotting 613C versus 6D. 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
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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
He have been observed in soil gas at values up to 430 and 50 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., & Lombard!, 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., Lombard!, 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.
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Klusman, R. W. (1993). Soil gas and related methods for natural resource exploration. New York, NY:
John Wiley & Sons.
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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APPENDIX H: MODELING
It is standard practice to evaluate and model complex environmental systems as separate components,
as can be the case with water operations 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).
For a holistic systems approach, it is important to evaluate how the components interact with each
other, and how the entire system responds. This integration is often achieved by either loosely or
tightly coupling individual system components with fully integrated complete system models available.
Modeling will be important in both case studies and scenario evaluations. The prospective case studies
provide an opportunity to test our level of understanding by comparing model performance to field
observations. This understanding will help justify the use of specific models for hypothesis testing
during the retrospective studies. Finally, demonstrated understanding provides the foundation for
predicting system response under future scenarios.
CASE STUDIES
PROSPECTIVE CASE STUDIES
Application and testing of models will be integrated into the prospective case studies. By collecting
characterization data prior to hydraulic fracturing, baseline conditions can be determined and used to
generate the mathematically required initial conditions for the model. The modeling team will
participate in planning the field effort in order to generate the specific types of data required. From this
starting point, the ability of the models to represent hydraulic fracturing operations can be evaluated by
comparing initial-to-final conditions in the model with those generated from field sampling.
For example, from a ground water modeling perspective, various aspects of the hydraulic fracturing
process can be investigated, including:
» The pressure pulse resulting from fracturing.
« Potential indicators of well construction faults.
• The flow and composition of the flowback and produced water.
« Possible early time impacts to water supply wells.
Ground water modeling for prospective case studies may match a site conceptual model that is
expected to include the following geologic elements:
« Shale beds located at depths of 1,000 feet or greater.
• Aquifers consisting of heterogeneous geologic formations.
• Unconsolidated, consolidated, and fractured consolidated materials.
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» Possible presence of abandoned and improperly sealed wells.
Subsurface transport is expected to include:
• Flow of reactive chemical species.
» Potential importance of temperature and pressure effects.
« Mixtures of inorganic and organic chemicals.
• Two-phase flow of water and gas.
The sites are expected to require:
• Simulation in three dimensions, although some simple questions are expected to be answerable
by one- or two-dimensional analyses.
» Time-dependent simulations in which the time scales include short times for chemical reaction
and long times for transport to drinking water wells.
• Site-, region-, and basin-scale evaluations.
The simulation of a hydraulic fracturing operation shares many characteristics with certain types of
petroleum reservoir simulations. As a consequence, the modeling studies may be computationally
intensive. Specific research questions will be developed for each aspect of the hydraulic fracturing case
study. From these and site data, a conceptual model will be developed for model application. An
appropriately chosen model can then be used in answering the research question. Following this
process ensures that the level of complexity of the model will be appropriate but not excessive.
RETROSPECTIVE CASE STUDIES
Modeling can play an important role in the testing of hypotheses of cause and effect. The forensic
studies will take the step-wise and progressive strategy, starting with simple conceptualizations and
adding complexity as data and understanding supports.
SCENARIO TESTING
While the scenarios will be initially approached through separate evaluations of the different water
operations (e.g., water acquisition, chemical mixing, well injection, flowback and produced water,
wastewater treatment and waste disposal), full systems evaluations will require integrated systems
modeling.
MODELING TOOLS
The types of models to be used in this study may include:
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 been adapted for
problems requiring capabilities that will be also needed for hydraulic fracturing simulation: multiphase
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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 include the finite difference solutions,
such as represented by the USGS Modular Flow (MODFLOW) and its associated transport codes,
including Modular Transport 3D-Multispecies (MT3DMS) or the related Reactive Transport 3D (RT3D),
and the finite element solutions, such as the Finite Element Subsurface Flow Model (FEFLOW), and
others semi-analytical solutions (e.g., GFLOW and TimML). 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 have potential for supporting hydraulic fracturing
assessments.
Watershed models. EPA has experience with the well-established watershed management models
SWAT (semi-empirical, vector-based, continuous in time) and HSPF (semi-physics-based, vector-based,
continuous in time). A number of innovative watershed models are under development, including
GBMM (semi-physics based, gridded, continuous in time) and VELMA (semi-empirical, gridded,
continuous in time). The watershed models will play an important role in modeling water acquisition.
Waterbody models. The well-established EPA model for representing water quality in rivers and
reservoirs is Water Quality Analysis Simulation Program (WASP). EPA has invested in Environmental
Fluid Dynamics Code (EFDC) for a more detailed representation of hydrodynamics in water bodies.
Alternative futures models. Alternative futures analysis involves 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). Fortunately for this project, EPA has conducted
alternative futures analysis for much of the landscape of interest for this project. The EPA Region 3
Chesapeake Bay Program futures scenarios extrapolate to 2030 for a region that covers much of the
Marcellus shale play. The EPA ORD Futures Midwest Landscape study includes a future landscape for
2022 for a region that covers Colorado and North Dakota. We currently do not have an EPA futures
coverage for the Barnett Shale play.
Integrated modeling systems. The EPA has led a multi-agency development of the Framework for Risk
Analysis in Multimedia Environmental Systems (FRAMES) platform for integrated multi-media, multi-
component, multi-receptor risk assessment. FRAMES is currently being applied to the mountaintop
mining issues in West Virginia in cooperation with EPA Region 3. Other platforms available for water
resources evaluations include the DHI Mike SHE. Research continues at the University of Waterloo on
the integrated ground water/surface water three-dimensional simulator HydroGeoSphere. Full,
integrated modeling is beyond the scope of this research plan, but may play an important role in future
hydraulic fracturing investigations.
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CALIBRATION AND UNCERTAINTY IN MODEL APPLICATIONS
Hydraulic fracturing models will be calibrated with data to show that they simulate the changes from the
pre- and post-hydraulic fracturing of the formation; this provides the minimum testing of the model.
Where possible, it is strongly desired to test the calibration of the models using a second data set. For
example, initial gas production data can be used to calibrate the model, while data collected later should
be used to test the calibration.
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). Thus, environmental models do not possess generic validity (Oreskes et al., 1994), but the
application is critically dependent on choices of input parameters which are subject to the uncertainties
described above. Proper application of models requires acknowledgement of uncertainties, which can
lead to best scientific credibility for the results and by extension the Agency (see Oreskes, 2003).
The accomplishment of this task is dependent on the complexity of the simulation model, the time
available, and the computer resources available. At one extreme, where the models are very compute-
time extensive (as expected for the full hydraulic fracturing simulation), it may only be possible to
explore a limited number of plausible alternative parameter sets. For more simple models a variant of
Monte Carlo simulation could be used to generate many alternate results that could be analyzed
statistically to present a formal probability of a result.
Some available tools include the Design Analysis Kit for Optimization and Terascale Applications
(DAKOTA) and Computer Codes for Universal Sensitivity Analysis, Calibration, and Uncertainty
Evaluation (UCODE-2005); Parameter Estimation (PEST) and JTOUGH2 could be used for suitably
conceptualized problems.
References
Baker, J. P., Hulse, D. W., Gregory, S. V., White, D., van Sickle, J., Berger, P. A., Dole, D., & Schumaker, N.
H. (2004). Alternative futures for the Willamette River Basin, Oregon. Ecological Applications, 14(2),
313-324.
Oreskes, N. K., Shrader-Frechette, K., & Belitz, K. (1994, February 4). Verification, validation, and
confirmation of numerical models in the earth sciences. Science, 263(5147), 641-646.
Oreskes, N. K. (2003). The role of quantitative models in science. In C. D. Canham, J. J. Cole, & W. K.
Lauenroth (Eds.), Models in ecosystem science (pp. 13-31). Princeton, NJ: Princeton University Press.
Tonkin, M., & Dougherty, J. (2009). Efficient nonlinear predictive error variance for highly
parameterized models. Water Resources Research, 45.
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GLOSSARY
Abandoned well: A well that is no longer in use, whether dry, inoperable, or no longer productive.1
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.2Aquitard: 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.
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. Both the process and the returned water are 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 sand-laden gelled fluid 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
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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
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 (oxidation-reduction) 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 (or have had) active hydraulic fracturing practices,
with a focus on sites with reported instances of drinking water resource contamination or other impacts
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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 the likelihood
that 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.
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
Turbidity: A cloudy condition in water due to suspended silt or organic matter.2
Underground injection well: 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. U.S. 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.
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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. (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, Division of Mineral Resources, Bureau of Oil
& Gas Regulation. Retrieved January 20, 2011, from ftp://ftp.dec.state.ny.us/dmn/download/
OGdSGEISFull.pdf.
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.htmftltds.
8. Ground Water Protection Council & ALL Consulting. (2009, April). Modern shale gas
development in the United States: A primer. Contract DE-FG26-04NT15455. Prepared for the
U.S. 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. U.S. 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.
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