vvEPA
United States
Environmental Protection
Agency
EPA-600-R-16-236ES
December 2016
www.epa.gov/hfstudy
Hydraulic Fracturing for Oil and Gas:
Impacts from the Hydraulic Fracturing
Water Cycle on Drinking Water
Resources in the United States
Executive Summary
Office of Research and Development
Washington, DC
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Aerial photograph of hydraulic fracturing well sites near Williston, North Dakota.
Image ©J Henry Fair / Flights provided by LightHawk
Executive Summary
People rely on clean and plentiful water re-
sources to meet their basic needs, includ-
ing drinking, bathing and cooking. In the early
2000s, members of the public began to raise con-
cerns about potential impacts on their drinking
water from hydraulic fracturing at nearby oil and
gas production wells. In response to these con-
cerns, Congress urged the U.S. Environmental
Protection Agency (EPA] to study the relation-
ship between hydraulic fracturing for oil and gas
and drinking water in the United States.
The goals of the study were to assess the po-
tential for activities in the hydraulic fracturing
water cycle to impact the quality or quantity of
drinking water resources and to identify factors
that affect the frequency or severity of those im-
pacts. To achieve these goals, the EPA conducted
independent research, engaged stakeholders
through technical workshops and roundtables,
and reviewed approximately 1,200 cited sources
of data and information. The data and informa-
tion gathered through these efforts served as the
basis for this report, which represents the culmi-
nation of the EPA's study of the potential impacts
of hydraulic fracturing for oil and gas on drinking
water resources.
The hydraulic fracturing water cycle de-
scribes the use of water in hydraulic fractur-
ing, from water withdrawals to make hydraulic
fracturing fluids, through the mixing and injec-
tion of hydraulic fracturing fluids in oil and gas
production wells, to the collection and disposal
or reuse of produced water. These activities can
impact drinking water resources under some
circumstances. Impacts can range in frequency
and severity, depending on the combination of
hydraulic fracturing water cycle activities and lo-
cal- or regional-scale factors. The following com-
binations of activities and factors are more likely
than others to result in more frequent or more
severe impacts:
• Water withdrawals for hydraulic fracturing
in times or areas of low water availability,
particularly in areas with limited or declin-
ing groundwater resources;
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• Spills during the management of hydraulic frac-
turing fluids and chemicals or produced water
that result in large volumes or high concentra-
tions of chemicals reaching groundwater re-
sources;
• Injection of hydraulic fracturing fluids into
wells with inadequate mechanical integrity
allowing gases or liquids to move to groundwater
resources;
• Injection of hydraulic fracturing fluids directly
into groundwater resources;
• Discharge of inadequately treated hydraulic frac-
turing wastewater to surface water resources;
and
• Disposal or storage of hydraulic fracturing waste-
water in unlined pits, resulting in contamination
of groundwater resources.
The above conclusions are based on cases of
identified impacts and other data, information, and
analyses presented in this report. Cases of impacts
were identified for all stages of the hydraulic frac-
turing water cycle. Identified impacts generally oc-
curred near hydraulically fractured oil and gas pro-
duction wells and ranged in severity, from temporary
changes in water quality to contamination that made
private drinking water wells unusable.
The available data and information allowed us to
qualitatively describe factors that affect the frequen-
cy or severity of impacts at the local level. However,
significant data gaps and uncertainties in the avail-
able data prevented us from calculating or estimat-
ing the national frequency of impacts on drinking
water resources from activities in the hydraulic frac-
turing water cycle. The data gaps and uncertainties
described in this report also precluded a full charac-
terization of the severity of impacts.
The scientific information in this report can help
inform decisions by federal, state, tribal, and local
officials; industry; and communities. In the short-
term, attention could be focused on the combina-
tions of activities and factors outlined above. In the
longer-term, attention could be focused on reducing
the data gaps and uncertainties identified in this re-
port. Through these efforts, current and future drink-
ing water resources can be better protected in areas
where hydraulic fracturing is occurring or being con-
sidered.
Drinking Water Resources
In this report, drinking water resources are defined
as any water that now serves, or in the future
could serve, as a source of drinking water for public
or private use. This includes both surface water
resources and groundwater resources (Text Box ES-
1). In 2010, approximately 58% of the total volume
of water withdrawn for public and non-public
water supplies came from surface water resources
and approximately 42% came from groundwater
resources (Maupin et al., 2014).1 Most people (86%
of the population) in the United States relied on
public water supplies for their drinking water in
in the United States
2010, and approximately 14% of the population
obtained drinking water from non-public water
supplies. Non-public water supplies are often
private water wells that supply drinking water to a
residence.
Future access to high-quality drinking water in
the United States will likely be affected by changes
in climate and water use. Since 2000, about 30%
of the total area of the contiguous United States
has experienced moderate drought conditions
and about 20% has experienced severe drought
conditions. Declines in surface water resources have
1 Public water systems provide water for human consumption from surface or groundwater through pipes or other
infrastructure to at least 15 service connections or serve an average of at least 25 people for at least 60 days a year. Non-
public water systems have fewer than 15 service connections and serve fewer than 25 individuals.
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Text Box ES-1: Drinking Water Resources
In this report, drinking water resources are considered to be any water that now serves, or in the future could serve, as a
source of drinking water for public or private use. This includes both surface water bodies and underground rock formations
that contain water.
could be used as a drinking water resource.
Surface water resources include water bodies located on the surface of the Earth. Rivers, springs, lakes, and reservoirs are
examples of surface water resources. Water quality and quantity are often considered when determining whether a surface
water resource could be used as a drinking water resource. ,4
Groundwater resources are underground rock formations that contain water. Groundwater resources are found at different
depths nearly everywhere in the United States. Resource depth, water quality, and water yield are often considered when
determining whether a groundwater resource could be used as a drinking water resource.
led to increased withdrawals and net depletions of
groundwater in some areas. As a result, non-fresh
water resources (e.g., wastewater from sewage
treatment plants, brackish groundwater and surface
water, and seawater) are increasingly treated and
used to meet drinking water demand.
Natural processes and human activities can
affect the quality and quantity of current and future
drinking water resources. This report focuses on the
potential for activities in the hydraulic fracturing
water cycle to impact drinking water resources;
other processes or activities are not discussed.
Hydraulic Fracturing for
Oil and Gas in the United States
Hydraulic fracturing is frequently used to enhance (Figure ES-1). During hydraulic fracturing, hydraulic
oil and gas production from underground rock fracturing fluid is injected down an oil or gas produc-
formations and is one of many activities that oc- tion well and into the targeted rock formation under
cur during the life of an oil and gas production well pressures great enough to fracture the oil- and gas-
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-yi-
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Text Box ES-2: Hydraulically Fractured Oil and Gas Production Wells
Hydraulically fractured oil and gas production wells come in different shapes and sizes. They can have different depths,
orientations, and construction characteristics. They can include new wells (i.e., wells that are hydraulically fractured soon
after construction) and old wells (i.e., wells that are hydraulically fractured after producing oil and gas for some time).
Well Depth
Wells can be relatively shallow or relatively deep, depending
on the depth of the targeted rock formation.
Production Well
Ground Surface
Targeted Rock Formation
Milam County, Texas
Well depth = 685 feet
San Augustine County, Texas
Well depth = 19,349 feet
Targeted Rock Formation
Well depths and locations from FracFocus. org.
Well Orientation
Wells can be vertical, horizontal, or deviated.
Vertical
Horizontal
Deviated
Well Construction Characteristics
Wells are typically constructed using multiple layers of casing and cement. The subsurface environment, state and federal
regulations, and industry experience and practices influence the number and placement of casing and cement.
Ground Surface
Protected
Groundwater
Casing >
Cement >~
Targeted Rock
Formation
Well diagrams are not to scale.
¦ Conductor-
•Surface •
Drilled Hole ¦
-Production-
V. J}
Conductor-"-^
I
I
-Surface-
- Intermediate-
-Production-
I
Conductor, surface, and production casings
Conductor, surface, intermediate, and
production casings
Oil and Gas Production Well Dictionary
Casing
Cement
Conductor casing
Intermediate casing
Production casing
Surface casing
Targeted rock formation
Steel pipe that extends from the ground surface to the bottom of the drilled hole
A slurry that hardens around the outside of the casing; cement fills the space between casings or
between a casing and the drilled hole and provides support for the casing
Casing that prevents the in-fill of dirt and rock in the uppermost few feet of drilled hole
Casing that seals off intermediate rock formations that may have different pressures than
deeper or shallower rock formations
Casing that transports fluids up and down the well
Casing that seals off groundwater resources that are identified as drinking water or useable
The part of a rock formation that contains the oil and/or gas to be extracted
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Hydraulically Fractured Well Locations
~ 2000-2013 Oil and Gas Wells
375 500 A
Miles
Source data credits: Drillinglnfo, Inc.
Basemap Credits: U.S. Census Bureau, Esri, DeLorme, GEBCO, NOAA
NGDC, and other contributors
Figure ES-2. Locations of approximately 275,000 wells that were drilled and likely hydraulically fractured between 2000 and
2013. Data from Drillinglnfo (2014).
public water supplies in counties with at least one
hydraulically fractured well.1 Underground, hydrau-
lic fracturing can occur in close vertical proximity to
drinking water resources. In some parts of the United
States (e.g., the Powder River Basin in Montana and
Wyoming), there is no vertical distance between the
top of the hydraulically fractured oil- or gas-bearing
rock formation and the bottom of treatable water,
as determined by data from state oil and gas agen-
cies and state geological survey data.2 In other parts
of the country (e.g., the Eagle Ford Shale in Texas),
there can be thousands of feet of rock that separate
treatable water from the hydraulically fractured oil-
or gas-bearing rock formation. When hydraulically
fractured oil and gas production wells are located
near or within drinking water resources, there is a
greater potential for activities in the hydraulic frac-
turing water cycle to impact those resources.
1 This estimate only includes counties in which 30% or more of the population (i.e., two or more times the national aver-
age) relied on non-public water supplies in 2010. See Section 2.5 in Chapter 2.
2 In these cases, water that is naturally found in the oil- and gas-bearing rock formation meets the definition of drinking
water in some parts of the basin. See Section 6.3.2 in Chapter 6.
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Approach: The Hydraulic Fracturing Water Cycle
The EPA studied the relationship between hydrau-
lic fracturing for oil and gas and drinking water
resources using the hydraulic fracturing water cycle
(Figure ES-3). The hydraulic fracturing water cycle
has five stages; each stage is defined by an activity
involving water that supports hydraulic fracturing.
The stages and activities of the hydraulic fracturing
water cycle include:
• Water Acquisition: the withdrawal of ground-
water or surface water to make hydraulic frac-
turing fluids;
• Chemical Mixing: the mixing of a base fluid
(typically water), proppant, and additives at the
well site to create hydraulic fracturing fluids;1
• Well Injection: the injection and movement of
hydraulic fracturing fluids through the oil and
gas production well and in the targeted rock for-
mation;
• Produced Water Handling: the on-site collec-
tion and handling of water that returns to the
surface after hydraulic fracturing and the trans-
portation of that water for disposal or reuse;2
and
• Wastewater Disposal and Reuse: the disposal
and reuse of hydraulic fracturing wastewater.3
Potential impacts on drinking water resources
from the above activities are considered in this re-
port. We do not address other concerns that have
been raised by stakeholders about hydraulic frac-
turing (e.g., potential air quality impacts or induced
seismicity) or other oil and gas exploration and pro-
duction activities (e.g., environmental impacts from
site selection and development), as these were not
included in the scope of the study. Additionally, this
report is not a human health risk assessment; it does
not identify populations exposed to hydraulic frac-
turing-related chemicals, and it does not estimate
the extent of exposure or estimate the incidence of
human health impacts.
Each stage of the hydraulic fracturing water cycle
was assessed to identify (1) the potential for impacts
on drinking water resources and (2) factors that af-
fect the frequency or severity of impacts. Specific
definitions used in this report are provided below:
• An impact is any change in the quality or quan-
tity of drinking water resources, regardless of
severity, that results from an activity in the hy-
draulic fracturing water cycle.
• A factor is a feature of hydraulic fracturing oper-
ations or an environmental condition that affects
the frequency or severity of impacts.
• Frequency is the number of impacts per a given
unit (e.g., geographic area, unit of time, number
of hydraulically fractured wells, or number of
water bodies).
• Severity is the magnitude of change in the qual-
ity or quantity of a drinking water resource as
measured by a given metric (e.g., duration, spa-
tial extent, or contaminant concentration).
1A base fluid is the fluid into which proppants and additives are mixed to make a hydraulic fracturing fluid; water is an
example of a base fluid. Additives are chemicals or mixtures of chemicals that are added to the base fluid to change its
properties.
2 "Produced water" is defined in this report as water that flows from and through oil and gas wells to the surface as a by-
product of oil and gas production.
3 "Hydraulic fracturing wastewater" is defined in this report as produced water from hydraulically fractured oil and gas
wells that is being managed using practices that include, but are not limited to, injection in Class II wells, reuse in other
hydraulic fracturing operations, and various aboveground disposal practices. The term "wastewater" is being used as
a general description of certain waters and is not intended to constitute a term of art for legal or regulatory purposes.
Class II wells are used to inject wastewater associated with oil and gas production underground and are regulated under
the Underground Injection Control Program of the Safe Drinking Water Act.
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\
Wastewater Disposal and Reuse
Water Acquisition
Well Injection
Figure not to scale
Chemical Mixing
Produced Water Handling
Figure ES-3. The five stages of the hydraulic fracturing water cycle. The stages (shown in the insets) identify activities involving water
that support hydraulic fracturing for oil and gas. Activities may take place in the same watershed or different watersheds and close
to or far from drinking water resources. Thin arrows in the insets depict the movement of water and chemicals. Specific activities in
the "Wastewater Disposal and Reuse" inset include (a) disposal of wastewater through underground injection, (b) wastewater
treatment followed by reuse in other hydraulic fracturing operations or discharge to surface waters, and (c) disposal through
evaporation or percolation pits.
Factors affecting the frequency or severity of
impacts were identified because they describe
conditions under which impacts are more or less
likely to occur and because they could inform the
development of future strategies and actions to
prevent or reduce impacts. Although no attempt
was made to identify or evaluate best practices,
ways to reduce the frequency or severity of im-
pacts from activities in the hydraulic fracturing
water cycle are described in this report when
they were reported in the scientific literature.
Laws, regulations, and policies also exist to pro-
tect drinking water resources, but a comprehen-
sive summary and broad evaluation of current or
proposed regulations and policies was beyond the
scope of this report.
Relevant scientific literature and data were
evaluated for each stage of the hydraulic fractur-
ing water cycle. Literature included articles pub-
lished in science and engineering journals, federal
and state government reports, non-governmental
organization reports, and industry publications.
Data sources included federal- and state-collected
data sets, databases maintained by federal and
8
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state government agencies, other publicly avail-
able data, and industry data provided to the EPA.1
The relevant literature and data complement re-
search conducted by the EPA under its Plan to
Study the Potential Impacts of Hydraulic Fracturing
on Drinking Water Resources (Text Box ES-3).
A draft of this report underwent peer review
by the EPA's Science Advisory Board (SAB). The
SAB is an independent federal advisory committee
that often conducts peer reviews of high-profile
scientific matters relevant to the EPA. Members of
the SAB and ad hoc panels formed under the aus-
pices of the SAB are nominated by the public and
selected based on factors such as technical exper-
tise, knowledge, experience, and absence of any
real or perceived conflicts of interest. Peer review
comments provided by the SAB and public com-
ments submitted to the SAB during their peer re-
view, including comments on major conclusions
and technical content, were carefully considered
in the development of this final document.
A summary of the activities in the hydraulic
fracturing water cycle and their potential to im-
pact drinking water resources is provided below,
including what is known about human health haz-
ards associated with chemicals identified across
all stages of the hydraulic fracturing water cycle.
Additional details are available in the full report.
Text Box ES-3: The EPA's Study of the Potential Impacts of Hydraulic Fracturing for Oil and Gas on
Drinking Water Resources
The EPA's study is the first national study of the potential impacts of hydraulic fracturing for oil and gas on drinking water
resources. It included independent research projects conducted by EPA scientists and contractors and a state-of-the-science
assessment of available data and information on the relationship between hydraulic fracturing and drinking water resources
(i.e., this report).
X
Public Comments
Public Meetings
Scientific
Literature
Science
Advisory Board
Existing Data
Science Advisory Board
Technical Workshops
and Roundtables
Existing Data
EPA Research Projects
This Report
Study of the Potential Impacts of Hydraulic Fracturing for Oil and Gas on Drinking Water Resources
Scientific Literature
Throughout the study, the EPA consulted with the Agency's independent Science Advisory Board (SAB) on the scope of the
study and the progress made on the research projects. The SAB also conducted a peer review of both the Plan to Study the
Potential Impacts of Hydraulic Fracturing on Drinking Water Resources (U.S. EPA, 2011; referred to as the Study Plan in this
report) and a draft of this report.
Stakeholder engagement also played an important role in the development and implementation of the study. While
developing the scope of the study, the EPA held public meetings to get input from stakeholders on the study scope and
design. While conducting the study, the EPA requested information from the public and engaged with technical, subject-
matter experts on topics relevant to the study in a series of technical workshops and roundtables. For more information on
the EPA's study, including the role of the SAB and stakeholders, visit www.epa.gov/hfstudy.
1 Industry data was provided to the EPA in response to two separate information requests to oil and gas service compa-
nies and oil and gas production well operators. Some of these data were claimed as confidential business information
under the Toxic Substances Control Act and were treated as such in this report.
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Water Acquisition
The withdrawal of groundwater or surface water to make hydraulic fracturing fluids.
Relationship to Drinking Water Resources
Groundwater and surface water resources that provide water for hydraulic fracturing
fluids can also provide drinking water for public or non-public water supplies.
Water is the major component of nearly all hy-
draulic fracturing fluids, typically making up
90-97% of the total fluid volume injected into a well.
The median volume of water used, per well, for hy-
draulic fracturing was approximately 1.5 million gal-
lons (5.7 million liters) between January 2011 and
February 2013, as reported in FracFocus 1.0 (Text
Box ES-4). There was wide variation in the water vol-
umes reported per well, with 10th and 90th percentiles
of 74,000 gallons (280,000 liters) and 6 million gal-
lons (23 million liters) per well, respectively. There
was also variation in water use per well within and
among states (Table ES-1). This variation likely re-
sults from several factors, including the type of well,
the fracture design, and the type of hydraulic fractur-
ing fluid used. An analysis of hydraulic fracturing flu-
id data from Gallegos et al. (2015) indicates that wa-
ter volumes used per well have increased over time
as more horizontal wells have been drilled.
Water used for hydraulic fracturing is typically
fresh water taken from available groundwater and/
or surface water resources located near hydrauli-
cally fractured oil and gas production wells. Water
sources can vary across the United States, depending
on regional or local water availability; laws, regula-
tions, and policies; and water management practices.
Hydraulic fracturing operations in the humid east-
ern United States generally rely on surface water
Text Box ES-4: FracFocus Chemical Disclosure Registry
The FracFocus Chemical Disclosure Registry is a publicly-accessible website (www.fracfocus.org) managed by the Ground
Water Protection Council (GWPC) and the Interstate Oil and Gas Compact Commission (IOGCC). Oil and gas production
well operators can disclose information at this website about water and chemicals used in hydraulic fracturing fluids at
individual wells. In many states where oil and gas production occurs, well operators are required to disclose to FracFocus
well-specific information on water and chemical use during hydraulic fracturing.
The GWPC and the IOGCC provided the EPA with over 39,000 PDF disclosures submitted by well operators to FracFocus
(version 1.0) before March 1, 2013. Data in the disclosures were extracted and compiled in a project database, which was
used to conduct analyses on water and chemical use for hydraulic fracturing. Analyses were conducted on over 38,000
unique disclosures for wells located in 20 states that were hydraulically fractured between January 1, 2011, and February
28, 2013.
Despite the challenge of adapting a dataset originally created for local use and single-PDF viewing to answer broader
questions, the project database created by the EPA provided substantial insight into water and chemical use for hydraulic
fracturing. The project database represents the data reported to FracFocus 1.0 rather than all hydraulic fracturing
that occurred in the United States during the study time period. The project database is an incomplete picture of all
hydraulic fracturing due to voluntary reporting in some states for certain time periods (in the absence of state reporting
requirements), the omission of information on confidential chemicals from disclosures, and invalid or erroneous
information in the original disclosures or created during the development of the database. The development of FracFocus
2.0, which became the exclusive reporting mechanism in June 2013, was intended to increase the quality, completeness,
and consistency of the data submitted by providing dropdown menus, warning and error messages during submission, and
automatic formatting of certain fields. The GWPC has announced additional changes and upgrades for FracFocus 3.0 to
enhance data searchability, increase system security, provide greater data accuracy, and further increase data transparency.
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Table ES-1. Water use per hydraulically fractured well between January 2011 and February 2013. Medians and percentiles
were calculated from data submitted to FracFocus 1.0 (Appendix B).
State
Number of FracFocus
1.0 Disclosures
Median Volume per
Well (gallons)
10th percentile
(gallons)
90th percentile
(gallons)
Arkansas
1,423
5,259,965
3,234,963
7,121,249
California
711
76,818
21,462
285,306
Colorado
4,898
463,462
147,353
3,092,024
Kansas
121
1,453,788
10,836
2,227,926
Louisiana
966
5,077,863
1,812,099
7,945,630
Montana
207
1,455,757
367,326
2,997,552
New Mexico
1,145
175,241
35,638
1,871,666
North Dakota
2,109
2,022,380
969,380
3,313,482
Ohio
146
3,887,499
2,885,568
5,571,027
Oklahoma
1,783
2,591,778
1,260,906
7,402,230
Pennsylvania
2,445
4,184,936
2,313,649
6,615,981
Texas
16,882
1,420,613
58,709
6,115,195
Utah
1,406
302,075
76,286
769,360
West Virginia
273
5,012,238
3,170,210
7,297,080
Wyoming
1,405
322,793
5,727
1,837,602
resources, whereas operations in the arid and semi-
arid western United States generally rely on ground-
water or surface water. Geographic differences in
water use for hydraulic fracturing are illustrated in
Figure ES-4, which shows that most of the water used
for hydraulic fracturing in the Marcellus Shale region
of the Susquehanna River Basin came from surface
water resources between approximately 2008 and
2013. In comparison, less than half of the water used
for hydraulic fracturing in the Barnett Shale region
of Texas came from surface water resources between
approximately 2011 and 2013.
Hydraulic fracturing wastewater and other low-
er-quality water can also be used in hydraulic fractur-
ing fluids to offset the need for fresh water, although
the proportion of injected fluid that is reused hydrau-
lic fracturing wastewater varies by location (Figure
ES-4).1 Overall, the proportion of water used in hy-
draulic fracturing that comes from reused hydraulic
fracturing wastewater appears to be low. In a survey
of literature values from 10 states, basins, or plays,
the median percentage of the injected fluid volume
that came from reused hydraulic fracturing waste-
water was 5% between approximately 2008 and
2014.2 There was an increase in the reuse of hydrau-
lic fracturing wastewater as a percentage of the in-
jected hydraulic fracturing fluid in both Pennsylvania
and West Virginia between approximately 2008 and
2014. This increase is likely due to the limited avail-
ability of Class II wells, which are commonly used to
dispose of oil and gas wastewater, and the costs of
trucking wastewater to Ohio, where Class II wells are
1 Reused hydraulic fracturing wastewater as a percentage of injected fluid differs from the percentage of produced water
that is managed through reuse in other hydraulic fracturing operations. For example, in the Marcellus Shale region of the
Susquehanna River Basin, approximately 14% of injected fluid was reused hydraulic fracturing wastewater, while ap-
proximately 90% of produced water was managed through reuse in other hydraulic fracturing operations (Figure ES-4a],
2See Section 4.2 in Chapter 4.
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(a) Marcellus Shale,
Susquehanna River Basin
4.1-4.6 million gallons
injected
420,000-1.3 million gallons
produced
¦ Surface Water ¦ Groundwater
Reused hydraulic fracturing wastewater
Reuse in hydraulic fracturing
¦ Class II well
*Less than approximately 1% is treated at facilities that are
either permitted to discharge to surface water or whose
discharge status is uncertain.
Most of the injected fluid stays in the subsurface; produced
water volumes over 10 years are approximately 10-30% of
the injected fluid volume.
(b) Barnett Shale, Texas
3.9-4.5 million gallons
injected
3.9-4.5 million gallons
produced
I Surface Water ¦ Groundwater
Reused hydraulic fracturing wastewater
Reuse in hydraulic fracturing
¦ Class II well
Produced water volumes over three years can be
approximately the same as the injected fluid volume.
Figure ES-4. Water budgets illustrative of hydraulic fracturing water management practices in (a) the
Marcellus Shale in the Susquehanna River Basin between approximately 2008 and 2013 and (b) the Barnett
Shale in Texas between approximately 2011 and 2013. Class II wells are used to inject wastewater associated
with oil and gas production underground and are regulated under the Underground Injection Control Program of
the Safe Drinking Water Act. Data sources are described in Figure 10-1 in Chapter 10.
more prevalent.1 Class II wells are also prevalent in
Texas, and the reuse of wastewater in hydraulic frac-
turing fluids in the Barnett Shale appears to be lower
than in the Marcellus Shale (Figure ES-4).
Because the same water resource can be used to
support hydraulic fracturing and to provide drink-
ing water, withdrawals for hydraulic fracturing can
directly impact drinking water resources by chang-
ing the quantity or quality of the remaining water.
Although every water withdrawal affects water quan-
tity, we focused on water withdrawals that have the
potential to significantly impact drinking water re-
1 See Chapter 8 for additional information on Class II wells.
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sources by limiting the availability of drinking water
or altering its quality. Water withdrawals for a single
hydraulically fractured oil and gas production well
are not expected to significantly impact drinking wa-
ter resources, because the volume of water needed to
hydraulically fracture a single well is unlikely to limit
the availability of drinking water or alter its quality.
If, however, multiple oil and gas production wells
are located within an area, the total volume of water
needed to hydraulically fracture all of the wells has
the potential to be a significant portion of the water
available and impacts on drinking water resources
can occur.
To assess whether hydraulic fracturing opera-
tions are a relatively large or small user of water, we
compared water use for hydraulic fracturing to total
water use at the county level (Text Box ES-5). In most
counties studied, the average annual water volumes
reported in FracFocus 1.0 were generally less than 1%
of total water use. This suggests that hydraulic frac-
turing operations represented a relatively small user
of water in most counties. There were exceptions,
however. Average annual water volumes reported in
FracFocus 1.0 were 10% or more of total water use in
26 of the 401 counties studied, 30% or more in nine
counties, and 50% or more in four counties.1 In these
counties, hydraulic fracturing operations represented
a relatively large user of water.
The above results suggest that hydraulic fractur-
ing operations can significantly increase the volume
of water withdrawn in particular areas. Increased wa-
ter withdrawals can result in significant impacts on
drinking water resources if there is insufficient wa-
ter available in the area to accommodate all users. To
assess the potential for these impacts, we compared
hydraulic fracturing water use to estimates of wa-
ter availability at the county level.2 In most counties
studied, average annual water volumes reported for
hydraulic fracturing were less than 1% of the esti-
mated annual volume of readily-available fresh water.
However, average annual water volumes reported for
hydraulic fracturing were greater than the estimated
annual volume of readily-available fresh water in 17
counties in Texas. This analysis suggests that there
was enough water available annually to support the
level of hydraulic fracturing reported to FracFocus 1.0
in most, but not all, areas of the country. This observa-
tion does not preclude the possibility of local impacts
in other areas of the country, nor does it indicate that
local impacts have occurred or will occur in the 17
counties in Texas. To better understand whether lo-
cal impacts have occurred, and the factors that affect
those impacts, local-level studies, such as the ones de-
scribed below, are needed.
Local impacts on drinking water quantity have
occurred in areas with increased hydraulic fracturing
activity. In 2011, for example, drinking water wells
in an area overlying the Haynesville Shale ran out of
water due to higher than normal groundwater with-
drawals and drought (Louisiana Ground Water Re-
sources Commission, 2012). Water withdrawals for
hydraulic fracturing contributed to these conditions,
along with other water users and the lack of precipi-
tation. Groundwater impacts have also been reported
in Texas. In a detailed case study, Scanlonetal. (2014)
estimated that groundwater levels in approximately
6% of the area studied dropped by 100 feet (31 me-
ters) to 200 feet (61 meters) or more after hydraulic
fracturing activity increased in 2009.
In contrast, studies in the Upper Colorado and
Susquehanna River basins found minimal impacts on
drinking water resources from hydraulic fracturing.
In the Upper Colorado River Basin, the EPA found that
high-quality water produced from oil and gas wells in
the Piceance tight sands provided nearly all of the wa-
ter for hydraulic fracturing in the study area (U.S. EPA,
1 Hydraulic fracturing water consumption estimates followed the same general pattern as the water use estimates pre-
sented here, but with slightly larger percentages in each category (Section 4.4 in Chapter 4).
2 County-level water availability estimates were derived from the Tidwell et al. (2013) estimates of water availability for
siting new thermoelectric power plants (see Text Box 4-2 in Chapter 4 for details). The county-level water availability
estimates used in this report represent the portion of water available to new users within a county.
13
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Text Box ES-5: County-Level Water Use for Hydraulic Fracturing
To assess whether hydraulic fracturing operations are a relatively large or small user of water, the average annual water use
for hydraulic fracturing in 2011 and 2012 was compared, at the county-level, to total water use in 2010.
For most counties studied, average annual water volumes reported for individual counties in FracFocus 1.0 were less than
1% of total water use in those counties. But in some counties, hydraulic fracturing operations reported in FracFocus 1.0
represented a relatively large user of water.
Examples of Water Use in Two Counties: Wilson County, Texas, and Mountrail County, North Dakota
o
>
Wilson County, Texas
44 wells reported in FracFocus 1.0
7,844
85
Hydraulic
Fracturing*
Total+
2010 Total Water Use+
164
106
4,833
Industrial use was 11 million gallons
Public Supply Irrigation
Domestic ¦ Livestock
Industrial ¦ Mining
Depending on local water availability, hydraulic fracturing
water withdrawals may be less likely to significantly impact
drinking water resources under this kind of scenario.
o
>
Mountrail County, North Dakota
508 wells reported in FracFocus 1.0
1,248
449
2010 Total Water Use+
179
288
135
438
183
Hydraulic
Fracturing*
Total+
Public Supply Irrigation
Domestic I Livestock
Industrial ¦ Mining
Depending on local water availability, hydraulic fracturing
water withdrawals may be more likely to significantly impact
drinking water resources under this kind of scenario.
'Hydraulic fracturing water use is a function of the water use per well and the total number of wells hydraulically fractured within a county. Average annual
water use for hydraulic fracturing was calculated at the county-level using data reported in FracFocus 1.0 in 2011 and 2012 (Appendix B).
+The U.S. Geological Survey compiles national water use estimates every five years in the National Water Census. Total water use at the county-level was
obtained from the most recent census, which was conducted in 2010 (Maupin et al., 2014).
2010 Total Water Use Categories
Public supply Water withdrawn by public and private water suppliers that provide water to at least 25 people or
have a minimum of 15 connections
Domestic Self-supplied water withdrawals for indoor household purposes such as drinking, food preparation,
bathing, washing clothes and dishes, flushing toilets, and outdoor purposes such as watering lawns
and gardens
Industrial Water used for fabrication, processing, washing, and cooling
Irrigation Water that is applied by an irrigation system to assist crop and pasture growth or to maintain
vegetation on recreational lands (e.g., parks and golf courses)
Livestock Water used for livestock watering, feedlots, dairy operations, and other on-farm needs
Mining Water used for the extraction of naturally-occurring minerals, including solids (e.g., coal, sand, gravel,
and other ores), liquids (e.g., crude petroleum), and gases (e.g., natural gas)
14
-------
2015b). Due to this high reuse rate, the EPA did not
identify any locations in the study area where hydrau-
lic fracturing contributed to locally high water use. In
the Susquehanna River Basin, multiple studies and
state reports have identified the potential for hydrau-
lic fracturing water withdrawals in the Marcellus Shale
to impact surface water resources. Evidence suggests,
however, that current water management strategies,
including passby flows and reuse of hydraulic fractur-
ing wastewater, help protect streams from depletion
by hydraulic fracturing water withdrawals. A passby
flow is a prescribed, low-streamflow threshold below
which water withdrawals are not allowed.
The above examples highlight factors that can af-
fect the frequency or severity of impacts on drinking
water resources from hydraulic fracturing water with-
drawals. In particular, areas of the United States that
rely on declining groundwater resources are vulner-
able to more frequent and more severe impacts from
all water withdrawals, including withdrawals for hy-
draulic fracturing. Extensive groundwater withdraw-
als can limit the availability of belowground drink-
ing water resources and can also change the qual-
ity of the water remaining in the resource. Because
groundwater recharge rates can be low, impacts can
last for many years. Seasonal or long-term drought
can also make impacts more frequent and more se-
vere for groundwater and surface water resources.
Hot, dry weather reduces or prevents groundwater
recharge and depletes surface water bodies, while
water demand often increases simultaneously (e.g.,
for irrigation). This combination of factors—high hy-
draulic fracturing water use and relatively low water
availability due to declining groundwater resources
and/or frequent drought—was found to be present in
southern and western Texas.
Water management strategies can also affect the
frequency and severity of impacts on drinking water
resources from hydraulic fracturing water withdraw-
als. These strategies include using hydraulic fractur-
ing wastewater or brackish groundwater for hydrau-
lic fracturing transitioning from limited groundwater
resources to more abundant surface water resources,
and using passby flows to control water withdrawals
from surface water resources. Examples of these wa-
ter management strategies can be found throughout
the United States. In western and southern Texas, for
example, the use of brackish water is currently reduc-
ing impacts on fresh water sources, and could, if in-
creased, reduce future impacts. Louisiana and North
Dakota have encouraged well operators to withdraw
water from surface water resources instead of high-
quality groundwater resources. And, as described
above, the Susquehanna River Basin Commission lim-
its surface water withdrawals during periods of low
stream flow.
Water Acquisition Conclusions
With notable exceptions, hydraulic fracturing
uses a relatively small percentage of water when
compared to total water use and availability at large
geographic scales. Despite this, hydraulic fracturing
water withdrawals can affect the quantity and qual-
ity of drinking water resources by changing the bal-
ance between the demand on local water resources
and the availability of those resources. Changes that
have the potential to limit the availability of drinking
water or alter its quality are more likely to occur in
areas with relatively high hydraulic fracturing water
withdrawals and low water availability, particularly
due to limited or declining groundwater resources.
Water management strategies (e.g., encouragement
of alternative water sources or water withdrawal
restrictions) can reduce the frequency or severity of
impacts on drinking water resources from hydraulic
fracturing water withdrawals.
15
-------
Chemical Mixing
The mixing of a base fluid, proppant, and additives at the well site to create
hydraulic fracturing fluids.
Relationship to Drinking Water Resources
Spills of additives and hydraulic fracturing fluids can reach groundwater and
surface water resources.
47
Hydraulic fracturing fluids are engineered to cre-
ate and grow fractures in the targeted rock for-
mation and to carry proppant through the oil and
gas production well into the newly-created fractures.
Hydraulic fracturing fluids are typically made up
of base fluids, proppant, and additives. Base fluids
make up the largest proportion of hydraulic fractur-
ing fluids by volume. As illustrated in Text Box ES-6,
base fluids can be a single substance (e.g., water in
the slickwater example) or can be a mixture of sub-
stances (e.g., water and nitrogen in the energized
fluid example). The EPA's analysis of hydraulic frac-
turing fluid data reported to FracFocus 1.0 suggests
that water was the most commonly used base fluid
between January 2011 and February 2013 (U.S. EPA,
2015a). Non-water substances, such as gases and hy-
drocarbon liquids, were reported to be used alone or
blended with water to form a base fluid in fewer than
3% of wells in FracFocus 1.0.
Proppant makes up the second largest propor-
tion of hydraulic fracturing fluids (Text Box ES-6).
Sand (i.e., quartz) was the most commonly reported
proppant between January 2011 and February 2013,
with 98% of wells in FracFocus 1.0 reporting sand as
the proppant (U.S. EPA, 2015a). Other proppants can
include man-made or specially engineered particles,
such as high-strength ceramic materials or sintered
bauxite.1
Additives generally make up the smallest pro-
portion of the overall composition of hydraulic frac-
turing fluids (Text Box ES-6), yet have the greatest
potential to impact the quality of drinking water re-
sources compared to proppant and base fluids. Addi-
tives, which can be a single chemical or a mixture of
chemicals, are added to the base fluid to change its
properties (e.g., adjust pH, increase fluid thickness,
or limit bacterial growth). The choice of which ad-
ditives to use depends on the characteristics of the
targeted rock formation (e.g., rock type, tempera-
ture, and pressure), the economics and availability of
desired additives, and well operator or service com-
pany preferences and experience.
The variability of additives, both in their purpose
and chemical composition, suggests that a large num-
ber of different chemicals may be used in hydraulic
fracturing fluids across the United States. The EPA
identified 1,084 chemicals that were reported to
have been used in hydraulic fracturing fluids between
2005 and 2013.23 The EPA's analysis of FracFocus
1.0 data indicates that between 4 and 28 chemicals
were used per well between January 2011 and Febru-
ary 2013 and that no single chemical was used in all
wells (U.S. EPA, 2015a). Three chemicals—methanol,
hydrotreated light petroleum distillates, and hydro-
1 Sintered bauxite is crushed and powdered bauxite that is fused into spherical beads at high temperatures.
2 This list includes 1,084 unique Chemical Abstracts Service Registration Numbers (CASRNs), which can be assigned
to a single chemical (e.g., hydrochloric acid) or a mixture of chemicals (e.g., hydrotreated light petroleum distillates).
Throughout this report, we refer to the substances identified by unique CASRNs as "chemicals."
3 Dayalu and Konschnik (2016) identified 995 unique CASRNs from data submitted to FracFocus between March 9,2011,
and April 13, 2015. Two hundred sixty-three of these CASRNs are not on the list of unique CASRNs identified by the EPA
(Appendix H). Only one of the 263 chemicals was reported at greater than 1% of wells, which suggests that these chemi-
cals were used at only a few sites.
-------
Text Box ES-6: Examples of Hydraulic Fracturing Fluids
Hydraulic fracturing fluids are engineered to create and extend fractures in the targeted rock formation and to carry
proppant through the production well into the newly-created fractures. While there is no universal hydraulic fracturing fluid,
there are general types of hydraulic fracturing fluids. Two types of hydraulic fracturing fluids are described below.
Slickwater
Slickwater hydraulic fracturing fluids are water-based fluids that generally contain a friction reducer. The friction reducer
makes it easier for the fluid to be pumped down the oil and gas production well at high rates. Slickwater is commonly used
to hydraulically fracture shale formations.
0.01% Friction Reducer (1)
Bradford County, Pennsylvania
Well depth = 7,255 feet
Total water volume = 4,763,000 gallons
16%* Reused
Wastewater
13% Sand
0.03% Acid 1
71% Fresh Water
006% Biocide (3)
0.002% Scale Inhibitor (2)
0.0009% Iron
Control (1)
0.0006% Corrosion
Inhibitor (5)
0.05% Additives (13 Chemicals)
Energized Fluid
Energized fluids are mixtures of liquids and gases. They can be used for hydraulic fracturing in under-pressured gas
0.08% Surfactant (3)
formations.
Rio Arriba County, New Mexico
Well depth = 7,640 feet
Total water volume = 105,000 gallons
28%* Nitrogen (gas)
13% Sand
58% Water
0.1% Acid (1)
1.2% Clay
Control (1)
0.05% Foamer (2)
0.03% Corrosion
Inhibitor (11)
0.03% Biocide (4)
0.01% Friction
Reducer (1)
0.008% Breaker (1)
0.006% Scale
Inhibitor (4)
0.004% Iron Control (1)
1.5% Additives (28 Chemicals)
*Maximum percent by mass of the total hydraulic fracturing fluid. Data obtained from FracFocus.org.
Additive Dictionary
Acid
Biocide
Breaker
Clay control
Corrosion inhibitor
Foamer
Friction reducer
Iron control
Scale inhibitor
Surfactant
Dissolves minerals and creates pre-fractures in the rock
Controls or eliminates bacteria in the hydraulic fracturing fluid
Reduces the thickness of the hydraulic fracturing fluid
Prevents swelling and migration of formation clays
Protects iron and steel equipment from rusting
Creates a foam hydraulic fracturing fluid
Reduces friction between the hydraulic fracturing fluid and pipes during pumping
Prevents the precipitation of iron-containing chemicals
Prevents the formation of scale buildup within the well
Reduces the surface tension of the hydraulic fracturing fluid
17
-------
Table ES-2. Chemicals reported in 10% or more of disclosures in FracFocus 1.0. Disclosures provided information on chemicals
used at individual well sites between January 1, 2011, and February 28, 2013.
Percent of
FracFocus 1.0
Chemical Name (CASRN)8
DlSCLOSURESb
Methanol (67-56-1)
72
Hydrotreated light petroleum
distillates (64742-47-8)
65
Hydrochloric acid (7647-01-0)
65
Water (7732-18-5)c
48
Isopropanol (67-63-0)
47
Ethylene glycol (107-21-1)
46
Peroxydisulfuric acid,
diammonium salt (7727-54-0)
44
Sodium hydroxide (1310-73-2)
39
Guar gum (9000-30-0)
37
Quartz (14808-60-7)c
36
Glutaraldehyde (111-30-8)
34
Propargyl alcohol (107-19-7)
33
Potassium hydroxide (1310-58-3)
29
Ethanol (64-17-5)
29
Acetic acid (64-19-7)
24
Citric acid (77-92-9)
24
2-Butoxyethanol (111-76-2)
21
Sodium chloride (7647-14-5)
21
Solvent naphtha, petroleum, heavy
aromatic (64742-94-5)
21
a"Chemical" refers to chemical substances with a single CASRN; these may be
petroleum distillates).
bAnalysis considered 34,675 disclosures that met selected quality assurance c
cQuartz and water were reported as ingredients in additives, in addition to pr<
Chemical Name (CASRN)8
Percent of
FracFocus 1.0
Disclosures'1
Naphthalene (91-20-3)
19
2,2-Dibromo-3-nitrilopropionamide
(10222-01-2)
16
Phenolic resin (9003-35-4)
14
Choline chloride (67-48-1)
14
Methenamine (100-97-0)
14
Carbonic acid, dipotassium salt
(584-08-7)
13
1,2,4-Trimethylbenzene (95-63-6)
13
Quaternary ammonium compounds,
benzyl-C12-16-alkyldimethyl,
chlorides (68424-85-1)
12
Poly(oxy-l,2-ethanediyl)-nonylphenyl-
hydroxy (mixture) (127087-87-0)
12
Formic acid (64-18-6)
12
Sodium chlorite (7758-19-2)
11
Nonyl phenol ethoxylate (9016-45-9)
11
Tetrakis(hydroxymethyl)phosphonium
sulfate (55566-30-8)
11
Polyethylene glycol (25322-68-3)
11
Ammonium chloride (12125-02-9)
10
Sodium persulfate (7775-27-1)
10
ure chemicals (e.g., methanol) or chemical mixtures (e.g., hydrotreated light
teria. See Table 5-2 in Chapter 5.
Dpants and base fluids.
chloric acid—were reported in 65% or more of the
wells in FracFocus 1.0; 35 chemicals were reported in
at least 10% of the wells (Table ES-2).
Concentrated additives are delivered to the well
site and stored until they are mixed with the base
fluid and proppant and pumped down the oil and gas
production well (Text Box ES-7). While the overall
concentration of additives in hydraulic fracturing flu-
ids is generally small (typically 2% or less of the total
volume of the injected fluid), the total volume of ad-
ditives delivered to the well site can be large. Because
over 1 million gallons (3.8 million liters) of hydraulic
fracturing fluid are generally injected per well, thou-
sands of gallons of additives can be stored on site and
used during hydraulic fracturing.
As illustrated in Text Box ES-7, additives are often
stored in multiple, closed containers [typically 200
gallons (760 liters) to 375 gallons (1,420 liters) per
container] and moved around the site in hoses and
tubing. This equipment is designed to contain addi-
tives and blended hydraulic fracturing fluid, but spills
can occur. Changes in drinking water quality can oc-
cur if spilled fluids reach groundwater or surface wa-
ter resources.
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Chemical Mixing Equipment Dictionary
Blender
Chemical additive unit
Flowback tanks
Frac head
High pressure pumps
Hydration unit
Manifold
Proppant
Water tanks
Blends water, proppant, and additives
Transports additives to the site and stores additives onsite
Stores liquid that returns to the surface after hydraulic fracturing
Connects hydraulic fracturing equipment to the production well
Pressurize mixed fluids before injection into the production well
Creates and stores gels used in some hydraulic fracturing fluids
Transfers fluids from the blender to the frac head
Stores proppant (often sand)
Stores water
Typical Layout of Chemical Mixing Equipment
This illustration shows how the different pieces of
equipment fit together to contain, mix, and inject
hydraulic fracturing fluid into a production well.
Water, proppant, and additives are blended together
and pumped to the manifold, where high pressure
pumps transfer the fluid to the frac head.
Additives and proppant can be blended with
water at different times and in different amounts
during hydraulic fracturing. Thus, the composition
of hydraulic fracturing fluids can vary during the
hydraulic fracturing job.
Source: Schlumberger
low pressure lines > high pressure lines
Source: Adapted from Olson (2011) and BJ Services Company (2009)
Blender
Chemical
Additive Units
Manifold
Frac Head
High Pressure
Pump
Text Box ES-7: Chemical Mixing Equipment
Well Pad During Hydraulic Fracturing
Equipment set up for hydraulic fracturing.
Water Tanks
Water Tanks
Ill II
High Pressure Pumps
Manifold
Flowback
Tanks
/ / / /
/\/ /N>/ / N./
High Pressure Pumps
Frac
Head
19
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Several studies have documented spills of hydrau-
lic fracturing fluids or additives. Nearly all of these
studies identified spills from state-managed spill da-
tabases. Data gathered for these studies suggest that
spills of hydraulic fracturing fluids or additives were
primarily caused by equipment failure or human er-
ror. For example, an EPA analysis of spill reports from
nine state agencies, nine oil and gas well operators,
and nine hydraulic fracturing service companies
characterized 151 spills of hydraulic fracturing fluids
or additives on or near well sites in 11 states between
January 2006 and April 2012 (U.S. EPA, 2015c). These
spills were primarily caused by equipment failure
(34% of the spills) or human error (25%), and more
than 30% of the spills were from fluid storage units
(e.g., tanks, totes, and trailers). Similarly, a study of
spills reported to the Colorado Oil and Gas Conser-
vation Commission identified 125 spills during well
stimulation (i.e., a part of the life of an oil and gas well
that often, but not always, includes hydraulic fractur-
ing) between January 2010 and August2013 (COGCC,
2014). Of these spills, 51% were caused by human er-
ror and 46% were due to equipment failure.
Studies of spills of hydraulic fracturing fluids or
additives provide insights on spill volumes, but little
information on chemical-specific spill composition.
Among the 151 spills characterized by the EPA, the
median volume of fluid spilled was 420 gallons (1,600
liters), although the volumes spilled ranged from 5
gallons (19 liters) to 19,320 gallons (73,130 liters).
Spilled fluids were often described as acids, biocides,
friction reducers, crosslinkers, gels, and blended hy-
draulic fracturing fluid, but few specific chemicals
were mentioned.1 Considine et al. (2012) identified
spills related to oil and gas development in the Mar-
cellus Shale that occurred between January 2008 and
August 2011 from Notices of Violations issued by the
Pennsylvania Department of Environmental Protec-
tion. The authors identified spills greater than 400
gallons (1,500 liters) and spills less than 400 gallons
(1,500 liters).
Spills of hydraulic fracturing fluids or additives
have reached, and therefore impacted, surface water
resources. Thirteen of the 151 spills characterized
by the EPA were reported to have reached a surface
water body (often creeks or streams). Among the 13
spills, reported spill volumes ranged from 28 gallons
(105 liters) to 7,350 gallons (27,800 liters). Addition-
ally, Brantley etal. (2014) and Considine etal. (2012)
identified fewer than 10 total instances of spills of
additives and/or hydraulic fracturing fluids greater
than 400 gallons (1,500 liters) that reached surface
waters in Pennsylvania between January 2008 and
June 2013. Reported spill volumes for these spills
ranged from 3,400 gallons (13,000 liters) to 227,000
gallons (859,000 liters).
Although impacts on surface water resources have
been documented, site-specific studies that could be
used to describe factors that affect the frequency or
severity of impacts were not available. In the absence
of such studies, we relied on fundamental scientific
principles to identify factors that affect how hydrau-
lic fracturing fluids and chemicals can move through
the environment to drinking water resources. Be-
cause these factors influence whether spilled fluids
reach groundwater and surface water resources, they
affect the frequency and severity of impacts on drink-
ing water resources from spills during the chemical
mixing stage of the hydraulic fracturing water cycle.
The potential for spilled fluids to impact ground-
water or surface water resources depends on the
characteristics of the spill, the environmental fate
and transport of the spilled fluid, and spill response
activities (Figure ES-5). Site-specific characteristics
affect how spilled liquids move through soil into the
subsurface or over the land surface. Generally, highly
permeable soils or fractured rock can allow spilled liq-
uids to move quickly into and through the subsurface,
limiting the opportunity for spilled liquids to move
over land to surface water resources. In low perme-
ability soils, spilled liquids are less able to move into
the subsurface and are more likely to move over the
1A crosslinker is an additive that increases the thickness of gelled fluids by connecting polymer molecules in the gelled
fluid.
20
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land surface. In either case, the volume spilled and
the distance between the location of the spill and
nearby water resources affects whether spilled liq-
uids reach drinking water resources. Large-volume
spills are generally more likely to reach drinking wa-
ter resources because they are more likely to be able
to travel the distance between the location of the spill
and nearby water resources.
In general, chemical and physical properties,
which depend on the identity and structure of a
chemical, control whether spilled chemicals evapo-
rate, stick to soil particles, or move with water. The
EPA identified measured or estimated chemical and
physical properties for 455 of the 1,084 chemicals
used in hydraulic fracturing fluids between 2005
and 2013.1 The properties of these chemicals varied
Spill Characteristics
What chemicals were spilled?
How much was spilled?
Spill Response Activities
What actions were taken to remove the
spilled fluid from the environment?
Spilled Hydraulic Fracturing
Fluid or Additive
Environmental Fate and Transport
How would the spilled fluid move
through the surface and
underground environment?
Figure ES-5. Generalized depiction of factors that influence whether spilled hydraulic fracturing fluids or additives reach
drinking water resources, including spill characteristics, environmental fate and transport, and spill response activities.
1 Chemical and physical properties were identified using EPI Suite™. EPI Suite™ is a collection of chemical and physical
property and environmental fate estimation programs developed by the EPA and Syracuse Research Corporation. It can
be used to estimate chemical and physical properties of individual organic compounds. Of the 1,084 hydraulic fractur-
ing fluid chemicals identified by the EPA, 629 were not individual organic compounds, and thus EPI Suite™ could not be
used to estimate their chemical and physical properties.
-------
widely, from chemicals that are more likely to move
quickly through the environment with a spilled liq-
uid to chemicals that are more likely to move slowly
through the environment because they stick to soil
particles.1 Chemicals that move slowly through the
environment may act as longer-term sources of con-
tamination if spilled.
Spill prevention practices and spill response ac-
tivities are designed to prevent spilled fluids from
reaching groundwater or surface water resources
and minimize impacts from spilled fluids. Spill pre-
vention and response activities are influenced by
federal, state, and local regulations and company
practices. Spill prevention practices include second-
ary containment systems (e.g., liners and berms),
which are designed to contain spilled fluids and pre-
vent them from reaching soil, groundwater, or sur-
face water. Spill response activities include activities
taken to stop the spill, contain spilled fluids (e.g., the
deployment of emergency containment systems),
and clean up spilled fluids (e.g., removal of contami-
nated soil). It was beyond the scope of this report
to evaluate the implementation and efficacy of spill
prevention practices and spill response activities.
The severity of impacts on water quality from
spills of hydraulic fracturing fluids or additives de-
pends on the identity and amount of chemicals that
reach groundwater or surface water resources, the
toxicity of the chemicals, and the characteristics of
the receiving water resource.2 Characteristics of the
receiving groundwater or surface water resource
(e.g., water resource size and flow rate) can affect
the magnitude and duration of impacts by reducing
the concentration of spilled chemicals in a drinking
water resource. Impacts on groundwater resources
have the potential to be more severe than impacts
on surface water resources because it takes longer
to naturally reduce the concentration of chemicals
in groundwater and because it is generally difficult
to remove chemicals from groundwater resourc-
es. Due to a lack of data, particularly in terms of
groundwater monitoring after spill events, little is
publicly known about the severity of drinking water
impacts from spills of hydraulic fracturing fluids or
additives.
Chemical Mixing Conclusions
Spills of hydraulic fracturing fluids and additives
during the chemical mixing stage of the hydraulic
fracturing water cycle have reached surface water
resources in some cases and have the potential to
reach groundwater resources. Although the avail-
able data indicate that spills of various volumes
can reach surface water resources, large volume
spills are more likely to travel longer distances to
nearby groundwater or surface water resources.
Consequently, large volume spills likely increase the
frequency of impacts on drinking water resources.
Large volume spills, particularly of concentrated ad-
ditives, are also likely to result in more severe im-
pacts on drinking water resources than small vol-
ume spills because they can deliver a large quantity
of potentially hazardous chemicals to groundwater
or surface water resources. Impacts on groundwater
resources are likely to be more severe than impacts
on surface water resources because of the inherent
characteristics of groundwater. Spill prevention and
response activities are designed to prevent spilled
fluids from reaching groundwater or surface water
resources and minimize impacts from spilled fluids.
1 These results describe how some hydraulic fracturing chemicals behave in infinitely dilute aqueous solutions, which is
a simplified approximation of the real-world mixtures found in hydraulic fracturing fluids. The presence of other chemi-
cals in a mixture can affect the fate and transport of a chemical.
2 Human health hazards associated with hydraulic fracturing fluid chemicals are discussed in Chapter 9 and summarized
in the "Chemicals in the Hydraulic Fracturing Water Cycle" section below.
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Well Injection
The injection and movement of hydraulic fracturing fluids through the oil and
gas production well and in the targeted rock formation.
Relationship to Drinking Water Resources
Belowground pathways, including the production well itself and newly-created
fractures, can allow hydraulic fracturing fluids or other fluids to reach underground
drinking water resources.
Hydraulic fracturing fluids primarily move along
two pathways during the well injection stage: the
oil and gas production well and the newly-created
fracture network. Oil and gas production wells are
designed and constructed to move fluids to and from
the targeted rock formation without leaking and to
prevent fluid movement along the outside of the well.
This is generally accomplished by installing multiple
layers ofcasingandcementwithinthedrilledhole (Text
Box ES-2), particularly where the well intersects oil-,
gas-, and/or water-bearing rock formations. Casing
and cement, in addition to other well components
(e.g., packers), can control hydraulic fracturing fluid
movement by creating a preferred flow pathway (i.e.,
inside the casing) and preventing unintentional fluid
movement (e.g., from the inside of the casing to the
surrounding environment or vertically along the
well from the targeted rock formation to shallower
formations).1 An EPA survey of oil and gas production
wells hydraulically fractured between approximately
September 2009 and September 2010 suggests
that hydraulically fractured wells are often, but
not always, constructed with multiple casings that
have varying amounts of cement surrounding each
casing (U.S. EPA, 2015d). Among the wells surveyed,
the most common number of casings per well was
two: surface casing and production casing (Text Box
ES-2). The presence of multiple cemented casings
that extend from the ground surface to below the
designated drinking water resource is one of the
primary well construction features that protects
underground drinking water resources.
During hydraulic fracturing a well is subjected
to greater pressure and temperature changes than
during any other activity in the life of the well. As
hydraulic fracturing fluid is injected into the well,
the pressure applied to the well increases until the
targeted rock formation fractures; then pressure
decreases. Maximum pressures applied to wells
during hydraulic fracturing have been reported to
range from less than 2,000 pounds per square inch
(psi) [14 megapascals (MPa)] to approximately
12,000 psi (83 MPa).2 A well can also experience
temperature changes as cooler hydraulic fracturing
fluid enters the warmer well. In some cases, casing
temperatures have been observed to drop from
212°F (100°C) to 64°F (18°C). A well can experience
multiple pressure and temperature cycles if
hydraulic fracturing is done in multiple stages or
if a well is re-fractured.3 Casing, cement, and other
well components need to be able to withstand
these changes in pressure and temperature, so that
hydraulic fracturing fluids can flow to the targeted
rock formation without leaking.
The fracture network created during hydraulic
fracturing is the other primary pathway along
1 Packers are mechanical devices installed with casing. Once the casing is set in the drilled hole, packers swell to fill the
space between the outside of the casing and the surrounding rock or casing.
2 For comparison, average atmospheric pressure is approximately 15 psi.
3 In a multi-stage hydraulic fracturing operation, specific parts of the well are isolated and hydraulically fractured until
the total desired length of the well has been hydraulically fractured.
23
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which hydraulic fracturing fluids move. Fracture
growth during hydraulic fracturing is complex and
depends on the characteristics of the targeted rock
formation and the characteristics of the hydraulic
fracturing operation. In general, rock characteristics,
particularly the natural stresses placed on the
targeted rock formation due to the weight of the
rock above, affect how the rock fractures, including
whether newly-created fractures grow vertically (i.e.,
perpendicular to the ground surface) or horizontally
(i.e., parallel to the ground surface) (Text Box ES-8).
Because hydraulic fracturing fluids are used to create
and grow fractures, fracture growth during hydraulic
fracturing can be controlled by limiting the rate and
volume of hydraulic fracturing fluid injected into the
well.
Publicly available data on fracture growth are
currently limited to microseismic and tiltmeter data
collected during hydraulic fracturing operations in
five shale plays in the United States. Analyses of these
data by Fisher and Warpinski (2012) andDaviesetal.
(2012) indicate that the direction of fracture growth
generally varied with depth and that upward vertical
fracture growth was often on the order of tens to
hundreds of feet in the shale formations studied
(Text Box ES-8). One percent of the fractures had a
fracture height greater than 1,148 feet (350 meters),
and the maximum fracture height among all of the
data reported was 1,929 feet (588 meters). These
reported fracture heights suggest that some fractures
can grow out of the targeted rock formation and into
an overlying formation. It is unknown whether these
observations apply to other hydraulically fractured
rock formations because similar data from hydraulic
fracturing operations in other rock formations are
not currently available to the public.
The potential for hydraulic fracturing fluids
to reach, and therefore impact, underground
drinking water resources is related to the pathways
along which hydraulic fracturing fluids primarily
move during hydraulic fracturing: the oil and gas
production well itself and the fracture network
created during hydraulic fracturing. Because the well
can be a pathway for fluid movement, the mechanical
integrity of the well is an important factor that affects
the frequency and severity of impacts from the well
injection stage of the hydraulic fracturing water
cycle.1 A well with insufficient mechanical integrity
can allow unintended fluid movement, either from
the inside to the outside of the well (pathway 1 in
Figure ES-6) or vertically along the outside of the
well (pathways 2-5). The existence of one or more
of these pathways can result in impacts on drinking
water resources if hydraulic fracturing fluids reach
groundwater resources. Impacts on drinking
water resources can also occur if gases or liquids
released from the targeted rock formation or other
formations during hydraulic fracturing travel along
these pathways to groundwater resources.
The pathways shown in Figure ES-6 can exist
because of inadequate well design or construction
(e.g., incomplete cement around the casing where
the well intersects with water-, oil-, or gas-bearing
formations) or can develop over the well's lifetime,
including during hydraulic fracturing. In particular,
casing and cement can degrade over the life of the
well because of exposure to corrosive chemicals,
formation stresses, and operational stresses (e.g.,
pressure and temperature changes during hydraulic
fracturing). As a result, some hydraulically fractured
oil and gas production wells may develop one or more
of the pathways shown in Figure ES-6. Changes in
mechanical integrity over time have implications for
older wells that are hydraulically fractured because
these wells may not be able to withstand the stresses
applied during hydraulic fracturing. Older wells may
also be hydraulically fractured at shallower depths,
where cement around the casing may be inadequate
or missing.
Examples of mechanical integrity problems
have been documented in hydraulically fractured
oil and gas production wells. In one case, hydraulic
1 Mechanical integrity is the absence of significant leakage within or outside of the well components.
24
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Text Box ES-8: Fracture Growth
Fracture growth during hydraulic fracturing is complex and depends on the characteristics of the targeted rock formation
and the characteristics of the hydraulic fracturing operation.
Primary Direction of Fracture Growth
In general, the weight of the rock above the point of hydraulic fracturing affects the primary direction of fracture growth.
Therefore, the depth at which hydraulic fracturing occurs affects whether fractures grow vertically or horizontally.
Ground Surface -
Production Well
When hydraulic fracturing occurs at depths less than
approximately 2,000 feet, the primary direction of fracture
growth is horizontal, or parallel to the ground surface.
When hydraulic fracturing occurs at depths
greater than approximately 2,000 feet, the
primary direction of fracture growth is vertical,
or perpendicular to the ground surface.
Fracture Height
Fisher and Warpinski (2012) and Davies et al. (2012) analyzed microseismic and tiltmeter data collected during thousands of
hydraulic fracturing operations in the Barnett, Eagle Ford, Marcellus, Niobrara, and Woodford shale plays. Their data provide
information on fracture heights in shale. Top fracture heights varied between shale plays and within individual shale plays.
The top fracture height is the vertical distance upward from the
well, between the fracture tip and the well.
ML
Shale Play
Approximate Median
Top Fracture Height
[feet (meters)]
Eagle Ford
130 (40)
Woodford
160 (50)
Barnett
200 (60)
Marcellus
400 (120)
Niobrara
160 (50)
Eagle Ford
Woodford
Barnett
Marcellus
Niobrara
100 200 300 400 500
Top Fracture Height (m)
Source: Davies et ol. (2012)
25
-------
%
w
Figure ES-6. Potential pathways for fluid movement in a cemented well. These pathways (represented by the white arrows)
include: (1) a casing and tubing leak into the surrounding rock, (2) an uncemented annulus (i.e., the space behind the
casing), (3) microannuli between the casing and cement, (4) gaps in cement due to poor cement quality, and (5) microannuli
between the cement and the surrounding rock. This figure is intended to provide a conceptual illustration of pathways that
can be present in a well and is not to scale.
fracturing of an inadequately cemented gas well
in Bainbridge Township, Ohio, contributed to the
movement of methane into local drinking water
resources.1 In another case, an inner string of casing
burst during hydraulic fracturing of an oil well near
Killdeer, North Dakota, resulting in a release of
hydraulic fracturing fluids and formation fluids that
impacted a groundwater resource.
The potential for hydraulic fracturing fluids or
other fluids to reach underground drinking water
resources is also related to the fracture network
created during hydraulic fracturing. Because fluids
1 Although ingestion of methane is not considered to be toxic, methane can pose a physical hazard. Methane can accumu-
late to explosive levels when allowed to exsolve [degas] from groundwater in closed environments.
26
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travel through the newly-created fractures, the
location of these fractures relative to underground
drinking water resources is an important factor
affecting the frequency and severity of potential
impacts on drinking water resources. Data on the
relative location of induced fractures to underground
drinking water resources are generally not available,
because fracture networks are infrequently mapped
and because there can be uncertainty in the depth
of the bottom of the underground drinking water
resource at a specific location.
Without these data, we were often unable
to determine with certainty whether fractures
created during hydraulic fracturing have reached
underground drinking water resources. Instead, we
considered the vertical separation distance between
hydraulically fractured rock formations and the
bottom of underground drinking water resources.
Based on computer modeling studies, Birdsell et al.
(2015) concluded that it is less likely that hydraulic
fracturing fluids would reach an overlying drinking
water resource if (1) the vertical separation distance
between the targeted rock formation and the drinking
water resource is large and (2) there are no open
pathways (e.g., natural faults or fractures, or leaky
wells). As the vertical separation distance between
the targeted rock formation and the underground
drinking water resource decreases, the likelihood of
upward migration of hydraulic fracturing fluids to
the drinking water resource increases (Birdsell et al.,
2015).
Figure ES-7 illustrates how the vertical
separation distance between the targeted rock
formation and underground drinking water
resources can vary across the United States. The two
example environments depicted in panels a and b
represent the range of separation distances shown in
panel c. In Figure ES-7a, there are thousands of feet
between the bottom of the underground drinking
water resource and the hydraulically fractured rock
formation. These conditions are generally reflective
of deep shale formations (e.g., Haynesville Shale),
where oil and gas production wells are first drilled
vertically and then horizontally along the targeted
rock formation. Microseismic data and modeling
studies suggest that, under these conditions,
fractures created during hydraulic fracturing are
unlikely to grow through thousands of feet of rock
into underground drinking water resources.
When drinking water resources are co-located
with oil and gas resources and there is no vertical
separation between the hydraulically fractured
rock formation and the bottom of the underground
drinking water resource (Figure ES-7b), the injection
of hydraulic fracturing fluids impacts the quality
of the drinking water resource. According to the
information examined in this report, the overall
occurrence of hydraulic fracturing within a drinking
water resource appears to be low, with the activity
generally concentrated in some areas in the western
United States (e.g., the Wind River Basin near
Pavillion, Wyoming, and the Powder River Basin
of Montana and Wyoming).1 Hydraulic fracturing
within drinking water resources introduces
hydraulic fracturing fluid into formations that may
currently serve, or in the future could serve, as a
drinking water source for public or private use. This
is of concern in the short-term if people are currently
using these formations as a drinking water supply. It
is also of concern in the long-term, because drought
or other conditions may necessitate the future use of
these formations for drinking water.
Regardless of the vertical separation between
the targeted rock formation and the underground
drinking water resource, the presence of other wells
near hydraulic fracturing operations can increase
the potential for hydraulic fracturing fluids or
other subsurface fluids to move to drinking water
resources. There have been cases in which hydraulic
fracturing atone well has affected a nearby oil and gas
well or its fracture network, resulting in unexpected
pressure increases at the nearby well, damage to the
nearby well, or spills at the surface of the nearby
well. These well communication events, or "frac hits,"
1 Section 6.3.2 in Chapter 6.
27
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(a)
Drinking Water Resource
i k
Separation
Distance in
Measured Depth
Vertical
Separation
Distance
Jsgw Jk
Targeted Rock Formation
(b)
K
^ Drinking Water Resource
Drinking Water Resource
and Targeted Rock Formation
Targeted Rock Formation
. No Vertical
I Separation
E | ™ Distance
15,000
10,000
-Q
£
"g 5,000
+-»
03
E
¦J3
(c)
„ II
nil
I
i 1 _ _
4
<& <& <& c& <£> <& <&
^ d' f ty w ^ op " a"; py Sy
cP cP cP cP cP cP cP cP cP
^cr „cr „cr Ncr , cr , cr Acr „cr ^cr
V V V ^ & A* 9>%
Separation Distance in Measured Depth (feet)
Figure ES-7. Examples of different subsurface environments in which hydraulic fracturing takes place. In panel a, there are
thousands of feet between the base of the underground drinking water resource and the part of the well that is hydraulically
fractured. Panel b illustrates the co-location of ground water and oil and gas resources. In these types of situations, there
is no separation between the shallowest point of hydraulic fracturing within the well and the bottom of the underground
drinking water resource. Panel c shows the estimated distribution of separation distances for approximately 23,000 oil and gas
production wells hydraulically fractured by nine service companies between 2009 and 2019 (U.S. EPA, 2015d), The separation
distance is the distance along the well between the point of shallowest hydraulic fracturing in the well and the base of the
protected groundwater resource (illustrated in panel a). The error bars in panel c display 95% confidence intervals.
have been reported in New Mexico, Oklahoma, and
other locations. Based on the available information,
frac hits most commonly occur when multiple wells
are drilled from the same surface location and when
wells are spaced less than 1,100 feet (335 meters)
apart. Frac hits have also been observed at wells
up to 8,422 feet (2,567 meters) away from a well
undergoing hydraulic fracturing.
Abandoned wells near a well undergoing
hydraulic fracturing can provide a pathway for
vertical fluid movement to drinking water resources
if those wells were not properly plugged or if the plugs
and cement have degraded over time. For example,
an abandoned well in Pennsylvania produced a 30-
foot (9-meter) geyser of brine and gas for more than
a week after hydraulic fracturing of a nearby gas well.
The potential for fluid movement along abandoned
wells may be a significant issue in areas with historic
oil and gas exploration and production. Various
studies estimate the number of abandoned wells
in the United States to be significant. For instance,
the Interstate Oil and Gas Compact Commission
estimates that over 1 million wells were drilled in
the United States prior to the enactment of state
oil and gas regulations (I0GCC, 2008). The location
and condition of many of these wells are unknown.
-------
and some states have programs to find and plug
abandoned wells.
Well Injection Conclusions
Impacts on drinking water resources associated
with the well injection stage of the hydraulic
fracturing water cycle have occurred in some
instances. In particular, mechanical integrity failures
have allowed gases or liquids to move to underground
drinking water resources. Additionally hydraulic
fracturing has occurred within underground
drinking water resources in parts of the United
States. This practice introduces hydraulic fracturing
fluids into underground drinking water resources.
Consequently the mechanical integrity of the well
and the vertical separation distance between the
targeted rock formation and underground drinking
water resources are important factors that affect
the frequency and severity of impacts on drinking
water resources. The presence of multiple layers
of cemented casing and thousands of feet of rock
between hydraulically fractured rock formations
and underground drinking water resources can
reduce the frequency of impacts on drinking water
resources during the well injection stage of the
hydraulic fracturing water cycle.
Produced Water Handling
The on-site collection and handling of water that returns to the surface after
hydraulic fracturing and the transportation of that water for disposal or reuse.
Relationship to Drinking Water Resources
Spills of produced water can reach groundwater and surface water resources.
After hydraulic fracturing the injection pressure
applied to the oil or gas production well is re-
leased, and the direction of fluid flow reverses, caus-
ing fluid to flow out of the well. The fluid that initially
returns to the surface after hydraulic fracturing is
mostly hydraulic fracturing fluid and is sometimes
called "flowback" (Text Box ES-9). As time goes on,
the fluid that returns to the surface contains water
and economic quantities of oil and/or gas that are
separated and collected. Water that returns to the
surface during oil and gas production is similar in
composition to the fluid naturally found in the target-
ed rock formation and is typically called "produced
water." The term "produced water" is also used to re-
fer to any water, including flowback, that returns to
the surface through the production well as a by-prod-
uct of oil and gas production. This latter definition of
"produced water" is used in this report.
Produced water can contain many constituents,
depending on the composition of the injected hydrau-
lic fracturing fluid and the type of rock hydraulically
fractured. Knowledge of the chemical composition of
produced water comes from the collection and analy-
sis of produced water samples, which often requires
advanced laboratory equipment and techniques that
can detect and quantify chemicals in produced water.
In general, produced water has been found to contain:
• Salts, including those composed from chloride,
bromide, sulfate, sodium, magnesium, and cal-
cium;
• Metals, including barium, manganese, iron, and
strontium;
• Naturally-occurring organic compounds, includ-
ing benzene, toluene, ethylbenzene, xylenes
(BTEX), and oil and grease;
• Radioactive materials, including radium; and
• Hydraulic fracturing chemicals and their chemi-
cal transformation products.
The amount of these constituents in produced
water varies across the United States, both within
-------
Text Box ES-9: Produced Water from Hydraulically Fractured Oil and Gas Production Wells
Water of varying quality is a byproduct of oil and gas production. The composition and volume of produced water varies by
well, rock formation, and time after hydraulic fracturing. Produced water can contain hydraulic fracturing fluid, formation
water, and chemical transformation products.
Produced
Water
Hydraulic Fracturing Fluid
Base fluid, proppant, and additives in hydraulic fracturing fluids.
Chemical Transformation Products
New chemicals that are formed when chemicals in
hydraulic fracturing fluids undergo
chemical reactions, degrade, or transform.
Formation Water
Water naturally found in the pore spaces of the targeted rock formation. Formation water is often salty and can have
different amounts and types of metals, radioactive materials, hydrocarbons (e.g., oil and gas), and other chemicals.
Water Produced Immediately After Hydraulic Fracturing
Generally, the fluid that initially returns to the surface is
mostly a mixture of the injected hydraulic fracturing fluid
and its reaction and degradation products.
Water Produced During Oil or Gas Production
The fluid that returns to the surface when oil and/or gas is
produced generally resembles the formation water.
Produced Water
(Also called "flowback"
Produced
Water
The volume of water produced per day immediately after hydraulic
fracturing is generally greater than the volume of water produced
per day when the well is also producing oil and/or gas.
and among different rock formations. Produced wa-
ter from shale and tight gas formations is typically
very salty compared to produced water from coalbed
methane formations. For example, the salinity of pro-
duced water from the Marcellus Shale has been re-
ported to range from less than 1,500 milligrams per
liter (mg/L) of total dissolved solids to over 300,000
mg/L, while produced water from coalbed methane
formations has been reported to range from 170 mg/L
of total dissolved solids to nearly 43,000 mg/L.1 Shale
and sandstone formations also commonly contain ra-
dioactive materials, including uranium, thorium, and
radium. As a result, radioactive materials have been
detected in produced water from these formations.
Produced water volumes can vary by well, rock
formation, and time after hydraulic fracturing. Vol-
1 For comparison, the average salinity of seawater is approximately 35,000 mg/L of total dissolved solids.
30
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umes are often described in terms of the volume of
hydraulic fracturing fluid used to fracture the well.
For example, Figure ES-4 shows that wells in the
Marcellus Shale typically produce 10-30% of the
volume injected in the first 10 years after hydraulic
fracturing. In comparison, some wells in the Barnett
Shale have produced 100% of the volume injected in
the first three years.
Because of the large volumes used for hydraulic
fracturing [about 4 million gallons (15 million li-
ters) per well in the Marcellus Shale and the Barnett
Shale], hundreds of thousands to millions of gallons
of produced water need to be collected and handled
at the well site. The volume of water produced per
day generally decreases with time, so the volumes
handled on site immediately after hydraulic fractur-
ing can be much larger than the volumes handled
when the well is producing oil and/or gas (Text Box
ES-9).
Produced water flows from the well to on-site
tanks or pits through a series of pipes or flowlines
(Text Box ES-10) before being transported offsite via
trucks or pipelines for disposal or reuse. While pro-
duced water collection, storage, and transportation
systems are designed to contain produced water,
spills can occur. Changes in drinking water quality
can occur if produced water spills reach groundwa-
ter or surface water resources.
Produced water spills have been reported across
the United States. Median spill volumes among the
datasets reviewed for this report ranged from ap-
proximately 340 gallons (1,300 liters) to 1,000 gal-
lons (3,800 liters) per spill.1 There were, however, a
small number of large volume spills. In North Dakota,
for example, there were 12 spills greater than 21,000
gallons (79,500 liters), five spills greater than 42,000
gallons (160,000 liters), and one spill of 2.9 million
gallons (11 million liters) in 2015. Common causes
of produced water spills included human error and
equipment leaks or failures. Common sources of pro-
duced water spills included hoses or lines and stor-
age equipment.
Spills of produced water have reached ground-
water and surface water resources. In U.S. EPA
(2015c), 30 of the 225 (13%) produced water spills
characterized were reported to have reached surface
water (e.g., creeks, ponds, or wetlands), and one was
reported to have reached groundwater. Of the spills
that were reported to have reached surface water, re-
ported spill volumes ranged from less than 170 gal-
lons (640 liters) to almost 74,000 gallons (280,000
liters). A separate assessment of produced water
spills reported to the California Office of Emergency
Services between January 2009 and December 2014
reported that 18% of the spills impacted waterways
(CCST, 2015).
Documented cases of water resource impacts
from produced water spills provide insights into
the types of impacts that can occur. In most of the
cases reviewed for this report, documented impacts
included elevated levels of salinity in groundwa-
ter and/or surface water resources.2 For example,
the largest produced water spill reported in this
report occurred in North Dakota in 2015, when ap-
proximately 2.9 million gallons (11 million liters)
of produced water spilled from a broken pipeline.
The spilled fluid flowed into Blacktail Creek and in-
creased the concentration of chloride and the electri-
cal conductivity of the creek; these observations are
consistent with an increase in water salinity. Elevat-
ed levels of electrical conductivity and chloride were
also found downstream in the Little Muddy River and
the Missouri River. In another example, pits holding
flowback fluids overflowed in Kentucky in 2007. The
spilled fluid reached the Acorn Fork Creek, decreas-
ing the pH of the creek and increasing the electrical
conductivity.
Site-specific studies of historical produced wa-
ter releases highlight the role of local geology in the
movement of produced water through the environ-
1 See Section 7.4 in Chapter 7.
2 Groundwater impacts from produced water management practices are described in Chapter 8 and summarized in the
"Wastewater Disposal and Reuse" section below.
31
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Text Box ES-10: On-Site Storage of Produced Water
Water that returns to the surface after hydraulic fracturing is collected and stored on site in pits or tanks.
Produced Water Storage During Oil or Gas Production
Water is generally produced throughout the life of an oil and gas production well. During oil and gas production, the
equipment on the well pad often includes the wellhead and storage tanks or pits for gas, oil, and produced water.
Produced Water Storage Immediately after
Hydraulic Fracturing
After hydraulic fracturing, water is returned
to the surface. Water initially produced
from the well after hydraulic fracturing is
sometimes called "flowback." This water can
be stored onsite in tanks or pits before being
taken offsite for injection in Class II wells,
reuse in other hydraulic fracturing operations,
or aboveground disposal.
Source: Adapted from Olson (2011) and
BJ Services Company (2009)
Above: Produced water storage pit. (Source: U.S. EPA)
Left: Produced water storage tanks. (Source: U.S. EPA)
¦> low pressure lines E high pressure tines
Above: Flowback pit. (Source: U.S. DOE/NETL)
Right: Flowback tanks. (Source: U.S. EPA)
Water Tanks
c:ws?
High Pressure Pumps
Manifold
*r-
/
/ N./
/\/
High Pressure Pumps
/ / /
/
/ N./
/
Flowback
Tanks
Frac
Head
32
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ment. Whittemore (2007) described a site in Kansas
where low permeability soils and rock caused pro-
duced water to primarily flow over the land surface
to nearby surface water resources, reducing the
amount of produced water that infiltrated soil. In
contrast, Otton et al. (2007) explored the release of
produced water and oil from two pits in Oklahoma.
In this case, produced water from the pits flowed
through thin soil and into the underlying, permeable
rock. Produced water was also identified in deeper,
less permeable rock. The authors suggest that pro-
duced water moved into the deeper, less permeable
rock through natural fractures. Together, these stud-
ies highlight the role of preferential flow paths (i.e.,
paths of least resistance) in the movement of pro-
duced water through the environment.
Spill response activities likely reduce the sever-
ity of impacts on groundwater and surface water
resources from produced water spills. For example,
in the North Dakota example noted above, absor-
bent booms were placed in the affected creek and
contaminated soil and oil-coated ice were removed
from the site. In another example, a pipeline leak in
Pennsylvania spilled approximately 11,000 gallons
(42,000 liters) of produced water, which flowed into
a nearby stream. In response, the pipeline was shut
off, a dam was constructed to contain the spilled pro-
duced water, water was removed from the stream,
and the stream was flushed with fresh water. In both
examples, it was not possible to quantify how spill
response activities reduced the severity of impacts
on groundwater or surface water resources. How-
ever, actions taken after the spills were designed to
stop produced water from entering the environment
(e.g., shutting off a pipeline), remove produced water
from the environment (e.g., using absorbent booms),
and reduce the concentration of produced water
constituents introduced into water resources (e.g.,
flushing a stream with fresh water).
The severity of impacts on water quality from
spills of produced water depends on the identity and
amount of produced water constituents that reach
groundwater or surface water resources, the toxicity
of those constituents, and the characteristics of the
receiving water resource.1 In particular, spills of pro-
duced water can have high levels of total dissolved
solids, which affects how the spilled fluid moves
through the environment. When a spilled fluid has
greater levels of total dissolved solids than ground-
water, the higher-density fluid can move downward
through groundwater resources. Depending on the
flow rate and other properties of the groundwater
resource, impacts from produced water spills can
last for years.
Produced Water Handling Conclusions
Spills of produced water during the produced
water handling stage of the hydraulic fracturing wa-
ter cycle have reached groundwater and surface wa-
ter resources in some cases. Several cases of water
resource impacts from produced water spills sug-
gest that impacts are characterized by increases in
the salinity of the affected groundwater or surface
water resource. In the absence of direct pathways to
groundwater resources (e.g., fractured rock), large
volume spills are more likely to travel further from
the site of the spill, potentially to groundwater or
surface water resources. Additionally, saline pro-
duced water can migrate downward through soil and
into groundwater resources, leading to longer-term
groundwater contamination. Spill prevention and
response activities can prevent spilled fluids from
reaching groundwater or surface water resources
and minimize impacts from spilled fluids.
1 Human health hazards associated with chemicals detected in produced water are discussed in Chapter 9 and summa-
rized in the "Chemicals in the Hydraulic Fracturing Water Cycle" section below.
33
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Wastewater Disposal and Reuse
The disposal and reuse of hydraulic fracturing wastewater.
Relationship to Drinking Water Resources
Disposal practices can release inadequately treated or untreated hydraulic
fracturing wastewater to groundwater and surface water resources.
In general, produced water from hydraulically frac-
tured oil and gas production wells is managed
through injection in Class II wells, reuse in other
hydraulic fracturing operations, or various aboveg-
round disposal practices (Text Box ES-11). In this
report, produced water from hydraulically fractured
oil and gas wells that is being managed through one
of the above management strategies is referred to as
"hydraulic fracturing wastewater." Wastewater man-
agement choices are affected by cost and other fac-
tors, including: the local availability of disposal meth-
ods; the quality of produced water; the volume, dura-
tion, and flow rate of produced water; federal, state,
and local regulations; and well operator preferences.
Available information suggests that hydraulic
fracturing wastewater is mostly managed through
injection in Class II wells. Veil (2015) estimated that
93% of produced water from the oil and gas indus-
try was injected in Class II wells in 2012. Although
this estimate included produced water from oil and
gas wells in general, it is likely indicative of nation-
wide management practices for hydraulic fracturing
wastewater. Disposal of hydraulic fracturing waste-
water in Class II wells is often cost-effective, espe-
cially when a Class II disposal well is located within
a reasonable distance from a hydraulically fractured
oil or gas production well. In particular, large num-
bers of active Class II disposal wells are found in Tex-
as (7,876), Kansas (5,516), Oklahoma (3,837), Loui-
siana (2,448), and Illinois (1,054) (U.S. EPA, 2016).
Disposal of hydraulic fracturing wastewater in Class
II wells has been associated with earthquakes in sev-
eral states, which may reduce the availability of injec-
tion in Class II wells as a wastewater disposal option
in these states.
Nationwide, aboveground disposal and reuse of
hydraulic fracturing wastewater are currently prac-
ticed to a much lesser extent compared to injection in
Class II wells, and these management strategies ap-
pear to be concentrated in certain parts of the United
States. For example, approximately 90% of hydraulic
fracturing wastewater from Marcellus Shale gas wells
in Pennsylvania was reused in other hydraulic frac-
turing operations in 2013 (Figure ES-4a). Reuse in
hydraulic fracturing operations is practiced in some
other areas of the United States as well, but at lower
rates (approximately 5-20%). Evaporation ponds
and percolation pits have historically been used in
the western United States to manage produced wa-
ter from the oil and gas industry and have likely been
used to manage hydraulic fracturing wastewater. Per-
colation pits, in particular, were commonly reported
to have been used to manage produced water from
stimulated wells in Kern County, California, between
2011 and 2014.1 Beneficial uses (e.g., livestock water-
ing and irrigation) are also practiced in the western
United States if the water quality is considered ac-
ceptable, although available data on the use of these
practices are incomplete.
Aboveground disposal practices generally re-
lease treated or, under certain conditions, untreated
wastewater directly to surface water or the land sur-
face (e.g., wastewater treatment facilities, evapora-
tion pits, or irrigation). If released to the land surface,
1 Hydraulic fracturing was the predominant stimulation practice. Other stimulation practices included acid fracturing
and matrix acidizing. California updated its regulations in 2015 to prohibit the use of percolation pits for the disposal of
fluids produced from stimulated wells.
-------
Text Box ES-il: Hydraulic Fracturing Wastewater Management
Produced water from hydraulically fractured oil and gas production wells is often, but not always, considered a waste
product to be managed. Hydraulic fracturing wastewater (i.e., produced water from hydraulically fractured wells) is generally
managed through injection in Class II wells, reuse in other hydraulic fracturing operations, and various aboveground disposal
practices.
Injection in Class II Wells
Most oil and gas wastewater—including hydraulic fracturing
wastewater—is injected in Class II wells, which are regulated
under the Underground Injection Control Program of the
Safe Drinking Water Act.
Class II wells are used to inject wastewater associated with oil and
gas production underground. Fluids can be injected for disposal
or to enhance oil or gas production from nearby oil and gas
production wells.
Reuse in Other Hydraulic Fracturing Operations
Hydraulic fracturing wastewater can be used, in combination
with fresh water, to make up hydraulic fracturing fluids at
nearby hydraulic fracturing operations.
Reuse in other hydraulic fracturing operations depends on
the quality and quantity of the available wastewater, the cost
associated with treatment and transportation of the wastewater,
and local water demand for hydraulic fracturing.
Aboveground Disposal Practices
Aboveground disposal of treated and untreated hydraulic fracturing wastewater can take many forms, including release to
surface water resources and land application.
Reused Hydraulic
Fracturing
Wastewater
Some wastewater treatment
facilities treat hydraulic
fracturing wastewater
and release the treated
wastewater to surface
water. Solid or liquid
by-products of the
treatment process can be
sent to landfills or injected
underground.
Evaporation ponds and
percolation pits can be used
for hydraulic fracturing
wastewater disposal.
Evaporation ponds allow
liquid waste to naturally
evaporate. Percolation pits
allow wastewater to move
into the ground, although
this practice has been
discontinued in most states.
Federal and state regulations affect aboveground disposal management options. For example, existing federal regulations
generally prevent the direct release of wastewater pollutants to waters of the United States from onshore oil and gas
extraction facilities east of the 98th meridian. However, in the arid western portion of the continental United States (west
of the 98th meridian), direct discharges of wastewater from onshore oil and gas extraction facilities to waters of the United
States may be permitted if the produced water has a use in agriculture or wildlife propagation and meets established water
quality criteria when discharged.
35
-------
treated or untreated wastewater can move through
soil to groundwater resources. Because the ultimate
fate of the wastewater can be groundwater or surface
water resources, the aboveground disposal of hy-
draulic fracturing wastewater, in particular, can im-
pact drinking water resources.
Impacts on drinking water resources from the
aboveground disposal of hydraulic fracturing waste-
water have been documented. For example, early
wastewater management practices in the Marcel-
lus Shale region in Pennsylvania included the use of
wastewater treatment facilities that released (i.e.,
discharged) treated wastewater to surface waters
(Figure ES-8). The wastewater treatment facilities
were unable to adequately remove the high levels of
total dissolved solids found in produced water from
Marcellus Shale gas wells, and the discharges con-
tributed to elevated levels of total dissolved solids
(particularly bromide) in the Monongahela River Ba-
sin. In the Allegheny River Basin, elevated bromide
levels were linked to increases in the concentration
of hazardous disinfection byproducts in at least one
downstream drinking water facility and a shift to
more toxic brominated disinfection byproducts.1 In
response, the Pennsylvania Department of Environ-
mental Protection revised existing regulations to
prevent these discharges and also requested that oil
and gas operators voluntarily stop bringing certain
kinds of hydraulic fracturing wastewater to facilities
that discharge inadequately treated wastewater to
surface waters.2
The scientific literature and recent data from the
Pennsylvania Department of Environmental Protec-
tion suggest that other produced water constituents
100%
90%
(U
| 80%
.2
| 70%
° 60%
ro 40%
£
•s 30%
4—'
§ 20%
-------
(e.g., barium, strontium, and radium) may have been
introduced to surface waters through the release of
inadequately treated hydraulic fracturing wastewa-
ter. In particular, radium has been detected in stream
sediments at or near wastewater treatment facili-
ties that discharged inadequately treated hydraulic
fracturing wastewater. Such sediments can migrate if
they are disturbed during dredging or flood events.
Additionally, residuals from the treatment of hydrau-
lic fracturing wastewater (i.e., the solids or liquids
that remain after treatment) are concentrated in the
constituents removed during treatment, and these
residuals can impact groundwater or surface water
resources if they are not managed properly.
Impacts on groundwater and surface water re-
sources from current and historic uses of lined and
unlined pits, including percolation pits, in the oil
and gas industry have been documented. For ex-
ample, Kell (2011) reported 63 incidents of non-
public water supply contamination from unlined or
inadequately constructed pits in Ohio between 1983
and 2007, and 57 incidents of groundwater contami-
nation from unlined produced water disposal pits
in Texas prior to 1984. Other cases of impacts have
been identified in several states, including New Mex-
ico, Oklahoma, Pennsylvania, and Wyoming.1 Impacts
among these cases included the detection of vola-
tile organic compounds in groundwater resources,
wastewater reaching surface water resources from
pit overflows, and wastewater reaching groundwater
resources through liner failures. Based on document-
ed impacts on groundwater resources from unlined
pits, many states have implemented regulations that
prohibit percolation pits or unlined storage pits for
either hydraulic fracturing wastewater or oil and gas
wastewater in general.
The severity of impacts on drinking water re-
sources from the aboveground disposal of hydraulic
fracturing wastewater depends on the volume and
quality of the discharged wastewater and the charac-
teristics of the receiving water resource. In general,
large surface water resources with high flow rates
can reduce the severity of impacts through dilution,
although impacts may not be eliminated. In con-
trast, groundwater is generally slow moving, which
can lead to an accumulation of hydraulic fracturing
wastewater contaminants in groundwater from con-
tinuous or repeated discharges to the land surface;
the resulting contamination can be long-lasting. The
severity of impacts on groundwater resources will
also be influenced by soil and sediment properties
and other factors that control the movement or deg-
radation of wastewater constituents.
Wastewater Disposal and Reuse Conclusions
The aboveground disposal of hydraulic fractur-
ing wastewater has impacted the quality of ground-
water and surface water resources in some instanc-
es. In particular, discharges of inadequately treated
hydraulic fracturing wastewater to surface water
resources have contributed to elevated levels of haz-
ardous disinfection byproducts in at least one down-
stream drinking water system. Additionally, the use
of lined and unlined pits for the storage or disposal
of oil and gas wastewater has impacted surface and
groundwater resources. Unlined pits, in particular,
provide a direct pathway for contaminants to reach
groundwater. Wastewater management is dynamic,
and recent changes in state regulations and practices
have been made to limit impacts on groundwater and
surface water resources from the aboveground dis-
posal of hydraulic fracturing wastewater.
1 See Section 8.4.5 in Chapter 8.
37
-------
Chemicals in the Hydraulic Fracturing Water Cycle
Chemicals are present in the hydraulic fracturing
water cycle. During the chemical mixing stage of
the hydraulic fracturing water cycle, chemicals are in-
tentionally added to water to alter its properties for
hydraulic fracturing (Text Box ES-6). Produced water,
which is collected, handled, and managed in the last
two stages of the hydraulic fracturing water cycle,
contains chemicals added to hydraulic fracturing flu-
ids, naturally occurring chemicals found in hydrau-
lically fractured rock formations, and any chemical
transformation products (Text Box ES-9). By evalu-
ating available data sources, we compiled a list of
1,606 chemicals that are associated with the hydrau-
lic fracturing water cycle, including 1,084 chemicals
reported to have been used in hydraulic fracturing
fluids and 599 chemicals detected in produced water.
This list represents a national analysis; an individual
well would likely have a fraction of the chemicals on
this list and may have other chemicals that were not
included on this list.
In many stages of the hydraulic fracturing water
cycle, the severity of impacts on drinking water re-
sources depends, in part, on the identity and amount
of chemicals that enter the environment. The proper-
ties of a chemical influence how it moves and trans-
forms in the environment and how it interacts with
the human body. Therefore, some chemicals in the
hydraulic fracturing water cycle are of more concern
than others because they are more likely to move
with water (e.g., spilled hydraulic fracturing fluid) to
drinking water resources, persist in the environment
(e.g., chemicals that do not degrade), and/or affect
human health.
Evaluating potential hazards from chemicals in
the hydraulic fracturing water cycle is most useful
at local and/or regional scales because chemical use
for hydraulic fracturing can vary from well to well
and because the characteristics of produced water
are influenced by the geochemistry of hydraulically
fractured rock formations. Additionally, site-specific
characteristics (e.g., the local landscape, and soil and
subsurface permeability) can affect whether and how
chemicals enter drinking water resources, which in-
fluences how long people may be exposed to specific
chemicals and at what concentrations. As a first step
for informing site-specific risk assessments, the EPA
compiled toxicity values for chemicals in the hydrau-
lic fracturing water cycle from federal, state, and in-
ternational sources that met the EPA's criteria for in-
clusion in this report.12
The EPA was able to identify chronic oral toxic-
ity values from the selected data sources for 98 of
the 1,084 chemicals that were reported to have been
used in hydraulic fracturing fluids between 2005 and
2013. Potential human health hazards associated
with chronic oral exposure to these chemicals in-
clude cancer, immune system effects, changes in body
weight, changes in blood chemistry, cardiotoxicity
neurotoxicity, liver and kidney toxicity, and repro-
ductive and developmental toxicity. Of the chemicals
most frequently reported to FracFocus 1.0, nine had
toxicity values from the selected data sources (Table
ES-3). Critical effects for these chemicals include kid-
ney/renal toxicity, hepatotoxicity, developmental tox-
icity (extra cervical ribs), reproductive toxicity, and
decreased terminal body weight.
1 Specifically, the EPA compiled noncancer oral reference values and cancer oral slope factors (Chapter 9). A reference
value describes the dose of a chemical that is likely to be without an appreciable risk of adverse health effects. In the
context of this report, the term "reference value" generally refers to reference values for noncancer effects occurring via
the oral route of exposure and for chronic durations. An oral slope factor is an upper-bound estimate on the increased
cancer risk from a lifetime oral exposure to an agent.
2 The EPA's criteria for inclusion in this report are described in Section 9.4.1 in Chapter 9. Sources of information that
met these criteria are listed in Table 9-1 of Chapter 9.
-------
Table ES-3. Available chronic oral reference values for hydraulic fracturing chemicals reported in 10% or more of disclosures
in FracFocus 1.0.
Chemical Name (CASRN)8
Chronic Oral
Reference Value
(milligrams per
KILOGRAM PER DAY)
Critical Effect
Percent of FracFocus
1.0 DlSCLOSURESb
Propargyl alcohol (107-19-7)
0.002°
Renal and hepatotoxicity
33
1,2,4-Trimethylbenzene (95-63-6)
0.01c
Decreased pain sensitivity
13
Naphthalene (91-20-3)
0.02°
Decreased terminal body
weight
19
Sodium chlorite (7758-19-2)
0.03°
Neuro-developmental effects
11
2-Butoxyethanol (111-76-2)
o.r
Hemosiderin deposition
in the liver
23
Quaternary ammonium compounds,
benzyl-C12-16-alkyldimethyl, chlorides
(68424-85-1)
0.44d
Decreased body weight and
weight gain
12
Formic acid (64-18-6)
0.9e
Reproductive toxicity
11
Ethylene glycol (107-21-1)
2C
Kidney toxicity
47
Methanol (67-56-1)
2C
Extra cervical ribs
73
a"Chemical" refers to chemical substances with a single CASRN; these may be pure chemicals (e.g., methanol) or chemical mixtures (e.g., hydrotreated light
petroleum distillates).
''Analysis considered 35,957 disclosures that met selected quality assurance criteria. See Table 9-2 in Chapter 9.
cFrom the EPA Integrated Risk Information System database.
dFrom the EPA Human Health Benchmarks for Pesticides database.
eFrom the EPA Provisional Peer-Reviewed Toxicity Value database.
Chronic oral toxicity values from the selected data
sources were identified for 120 of the 599 chemicals
detected in produced water. Potential human health
hazards associated with chronic oral exposure to
these chemicals include liver toxicity, kidney toxicity
neurotoxicity reproductive and developmental toxic-
ity and carcinogenesis. Chemical-specific toxicity val-
ues are included in Chapter 9.
Chemicals in the Hydraulic Fracturing Water
Cycle Conclusions
Some of the chemicals in the hydraulic fractur-
ing water cycle are known to be hazardous to human
health. Of the 1,606 chemicals identified by the EPA,
173 had chronic oral toxicity values from federal,
state, and international sources that met the EPA's
criteria for inclusion in this report. These data alone,
however, are insufficient to determine which chemi-
cals have the greatest potential to impact drinking
water resources and human health. To understand
whether specific chemicals can affect human health
through their presence in drinking water, data on
chemical concentrations in drinking water would be
needed. In the absence of these data, relative hazard
potential assessments could be conducted at local
and/or regional scales using the multi-criteria deci-
sion analysis approach outlined in Chapter 9. This ap-
proach combines available chemical occurrence data
with selected chemical, physical, and toxicological
properties to place the severity of potential impacts
(i.e., the toxicity of specific chemicals) into the con-
text of factors that affect the likelihood of impacts (i.e.,
frequency of use, and chemical and physical proper-
ties relevant to environmental fate and transport).
-------
Data Gaps and Uncertainties
The information reviewed for this report included
cases of impacts on drinking water resources
from activities in the hydraulic fracturing water cy-
cle. Using these cases and other data, information,
and analyses, we were able to identify factors that
likely result in more frequent or more severe im-
pacts on drinking water resources. However, there
were instances in which we were unable to form
conclusions about the potential for activities in the
hydraulic fracturing water cycle to impact drinking
water resources and/or the factors that influence
the frequency or severity of impacts. Below, we pro-
vide perspective on the data gaps and uncertainties
that prevented us from drawing additional conclu-
sions about the potential for impacts on drinking
water resources and/or the factors that affect the
frequency and severity of impacts.
In general, comprehensive information on the lo-
cation of activities in the hydraulic fracturing water
cycle is lacking, either because it is not collected, not
publicly available, or prohibitively difficult to aggre-
gate. This includes information on the:
• Above- and belowground locations of water
withdrawals for hydraulic fracturing;
• Surface locations of hydraulically fractured oil
and gas production wells, where the chemical
mixing, well injection, and produced water han-
dling stages of the hydraulic fracturing water
cycle take place;
• Belowground locations of hydraulic fracturing,
including data on fracture growth; and
• Locations of hydraulic fracturing wastewater
management practices, including the disposal of
treatment residuals.
There can also be uncertainty in the location
of drinking water resources. In particular, depths
of groundwater resources that are, or in the future
could be, used for drinking water are not always
known. If comprehensive data about the locations of
both drinking water resources and activities in the
hydraulic fracturing water cycle were available, it
would have been possible to more completely iden-
tify areas in the United States in which hydraulic
fracturing-related activities either directly interact
with drinking water resources or have the potential
to interact with drinking water resources.
In places where we know activities in the hy-
draulic fracturing water cycle have occurred or are
occurring, data that could be used to characterize the
presence, migration, or transformation of hydrau-
lic fracturing-related chemicals in the environment
before, during, and after hydraulic fracturing were
scarce. Specifically, local water quality data needed
to compare pre- and post-hydraulic fracturing con-
ditions are not usually collected or readily available.
The limited amount of data collected before, during
and after activities in the hydraulic fracturing water
cycle reduces the ability to determine whether these
activities affected drinking water resources.
Site-specific cases of alleged impacts on under-
ground drinking water resources during the well
injection stage of the hydraulic fracturing water cy-
cle are particularly challenging to understand (e.g.,
methane migration in Dimock, Pennsylvania; the Ra-
ton Basin of Colorado; and Parker County, Texas1).
This is because the subsurface environment is com-
plex and belowground fluid movement is not directly
observable. In cases of alleged impacts, activities in
the hydraulic fracturing water cycle may be one of
several causes of impacts, including other oil and gas
activities, other industries, and natural processes.
Thorough scientific investigations are often neces-
sary to narrow down the list of potential causes to a
single source at site-specific cases of alleged impacts.
Additionally, information on chemicals in the
hydraulic fracturing water cycle (e.g., chemical iden-
1 See Text Boxes 6-2 (Dimock, Pennsylvania), 6-3 (Raton Basin), and 6-4 (Parker County, Texas) in Chapter 6.
40
-------
tity; frequency of use or occurrence; and physical,
chemical, and toxicological properties) is not com-
plete. Well operators claimed at least one chemical
as confidential at more than 70% of wells reported
to FracFocus 1.0 (U.S. EPA, 2015a).1 The identity and
concentration of these chemicals, their transfor-
mation products, and chemicals in produced water
would be needed to characterize how chemicals as-
sociated with hydraulic fracturing activities move
through the environment and interact with the hu-
man body. Identifying chemicals in the hydraulic
fracturing water cycle also informs decisions about
which chemicals would be appropriate to test for
when establishing pre-hydraulic fracturing baseline
conditions and in the event of a suspected drinking
water impact.
Of the 1,606 chemicals identified by the EPA in
hydraulic fracturing fluid and/or produced water,
173 had toxicity values from sources that met the
EPA's criteria for inclusion in this report. Toxicity
values from these selected data sources were not
available for 1,433 (89%) of the chemicals, although
many of these chemicals have toxicity data available
from other data sources.2 Given the large number of
chemicals identified in the hydraulic fracturing wa-
ter cycle, this missing information represents a sig-
nificant data gap that makes it difficult to fully un-
derstand the severity of potential impacts on drink-
ing water resources.
Because of the significant data gaps and uncer-
tainties in the available data, it was not possible to
fully characterize the severity of impacts, nor was
it possible to calculate or estimate the national fre-
quency of impacts on drinking water resources from
activities in the hydraulic fracturing water cycle. We
were, however, able to estimate impact frequencies
in some, limited cases (i.e., spills of hydraulic frac-
turing fluids or produced water and mechanical
integrity failures).3 The data used to develop these
estimates were often limited in geographic scope or
otherwise incomplete. Consequently, national es-
timates of impact frequencies for any stage of the
hydraulic fracturing water cycle have a high degree
of uncertainty. Our inability to quantitatively deter-
mine a national impact frequency or to characterize
the severity of impacts, however, did not prevent us
from qualitatively describing factors that affect the
frequency or severity of impacts at the local level.
Report Conclusions
This report describes how activities in the hydrau-
lic fracturing water cycle can impact—and have
impacted—drinking water resources and the factors
that influence the frequency and severity of those
impacts. It also describes data gaps and uncertain-
ties that limited our ability to draw additional con-
clusions about impacts on drinking water resources
from activities in the hydraulic fracturing water cycle.
Both types of information—what we know and what
we do not know—provide stakeholders with scien-
tific information to support future efforts.
The uncertainties and data gaps identified
throughout this report can be used to identify future
efforts to further our understanding of the potential
for activities in the hydraulic fracturing water cycle to
impact drinking water resources and the factors that
affect the frequency and severity of those impacts. Fu-
ture efforts could include, for example, groundwater
and surface water monitoring in areas with hydrau-
lically fractured oil and gas production wells or tar-
1 Chemical withholding rates in FracFocus have increased over time. Konschnik and Dayalu (2016) reported that 92% of
wells reported in FracFocus 2.0 between approximately March 2011 and April 2015 used at least one chemical that was
claimed as confidential.
2 Chapter 9 describes the availability of data in other data sources. The quality of these data sources was not evaluated as
part of this report.
3 See Chapter 10.
-------
geted research programs to better characterize the
environmental fate and transport and human health
hazards associated with chemicals in the hydraulic
fracturing water cycle. Future efforts could identify
additional vulnerabilities or other factors that affect
the frequency and/or severity of impacts.
In the near term, decision-makers could focus
their attention on the combinations of hydraulic frac-
turing water cycle activities and local- or regional-
scale factors that are more likely than others to result
in more frequent or more severe impacts. These in-
clude:
• Water withdrawals for hydraulic fracturing in
times or areas of low water availability, particu-
larly in areas with limited or declining groundwa-
ter resources;
• Spills during the management of hydraulic frac-
turing fluids and chemicals or produced water
that result in large volumes or high concentra-
tions of chemicals reaching groundwater re-
sources;
• Injection of hydraulic fracturing fluids into
wells with inadequate mechanical integrity,
allowing gases or liquids to move to groundwater
resources;
• Injection of hydraulic fracturing fluids directly
into groundwater resources;
• Discharge of inadequately treated hydraulic frac-
turing wastewater to surface water resources;
and
• Disposal or storage of hydraulic fracturing waste-
water in unlined pits, resulting in contamination
of groundwater resources.
The above combinations of activities and factors
highlight, in particular, the vulnerability of ground-
water resources to activities in the hydraulic fractur-
ing water cycle. By focusing attention on the situa-
tions described above, impacts on drinking water
resources from activities in the hydraulic fracturing
water cycle could be prevented or reduced.
Overall, hydraulic fracturing for oil and gas is a
practice that continues to evolve. Evaluating the po-
tential for activities in the hydraulic fracturing water
cycle to impact drinking water resources will need to
keep pace with emerging technologies and new sci-
entific studies. This report provides a foundation for
these efforts, while helping to reduce current vulner-
abilities to drinking water resources.
Source: U.S. EPA
42
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References
Birdsell, DT; Rajaram, H; Dempsey, D; Viswanathan, HS. (2015). Hydraulic fracturing fluid migration in the
subsurface: A review and expanded modeling results. Water Resoures Research 51:7159-7188. http://dx.doi.
org/10.1002/2015WR017810.
BJ Services Company. (2009). BJ fracturing manual 2.0 (Revision No. 1). Houston, TX.
Brantley SL; Yoxtheimer, D; Arjmand, S; Grieve, P; Vidic, R; Pollak, J; Llewellyn, GT; Abad, J; Simon, C. (2014). Water
resource impacts during unconventional shale gas development: The Pennsylvania experience. International Journal of
Coal Geology 126:140-156. http://dx.doi.Org/10.1016/j.coal.2013.12.017.
CCST (California Council on Science and Technology). (2 015). An independent scientific assessment of well stimulation
in California Volume II: Potential environmental impacts of hydraulic fracturing and acid stimulations. Sacramento, CA.
https://ccst.us/publications/2015/2015SB4-v2.pdf.
COGCC (Colorado Oil and Gas Conservation Commission). (2014). Risk-based inspections: Strategies to address
environmental risk associated with oil and gas operations. (COGCC-2014-PROJECT #7948). Denver, CO. https://cogcc.
state.co.us/Announcements/RiskBasedlnspection/RiskB asedInspectionStrategy.pdf.
Considine, T; Watson, R; Considine, N; and Martin, J. (2012). Environmental impacts during Marcellus Shale gas drilling:
Causes, impacts, and remedies. (Report 2012-1). Buffalo, NY: Shale Resources and Society Institute. http://cce.cornell.
edu/EnergyClimateChange/NaturalGasDev/Documents/UBSRSI-Environmental%20Impact%20Report%2 02 012.pdf.
Davies, RJ; Mathias, SA; Moss, J; Hustoft, S; Newport, L. (2012). Hydraulic fractures: How far can they go? Marine and
Petroleum Geology 37:1-6. http://dx.doi.Org/10.1016/j.marpetgeo.2012.04.001.
Dayalu, A; Konschnik, K. (2016). FracFocus Chemical Disclosure Registry 1.0 and 2.0: Data conversion and
cleaning methods paper. Cambridge, MA: Harvard Law School, https://dataverse.harvard.edu/dataset.
xhtml?per sistentId=doi: 10.7 910/D VN/EFN V5 J.
Drillinglnfo, Inc. (2014). DI Desktop June 2014 download [Database], Austin, TX. http://info.drillinginfo.com/di-
desktop-downloads/.
EIA (U.S. Energy Information Administration). (2 016a). Hydraulic fracturing accounts for about half of current U.S. crude
oil production. http://www.eia.gov/todayinenergy/detail.cfm?id=25372.
EIA (U.S. Energy Information Administration). (2016b). Hydraulically fractured wells provide two-thirds of U.S. natural
gas production. http://www.eia.gov/todayinenergy/detail.cfm?id=26112.
Fisher, M; Warpinski, N. (2012). Hydraulic fracture height growth: Real data. Society of Petroleum Engineers Production
and Operations 27:8-19. http://dx.doi.org/10.2118/145949-PA.
Gallegos, TJ; Varela, BA. (2015). Trends in hydraulic fracturing distributions and treatment fluids, additives, proppants,
and water volumes applied to wells drilled in the United States from 1947 through 2010: Data analysis and comparison
to the literature. (Scientific Investigations Report 2014-5131). Reston, VA: U.S. Geological Survey, http://dx.doi.
org/10.3133/sir2 0145131.
43
-------
Gallegos, TJ; Varela, BA; Haines, SS; Engle, MA. (2015). Hydraulic fracturing water use variability in the United
States and potential environmental implications. Water Resources Research 51:5839-5845. http://dx.doi.
org/10.1002/2015WR017278.
IOGCC (Interstate Oil and Gas Compact Commission). (2002). States experience with hydraulic fracturing. A survey
ofthe interstate oil and gas compact commission. http://groundwork.iogcc.ok.gov/sites/default/files/09IOG5571_
StatesExperience%20w-HydFrac.pdf.
IOGCC (Interstate Oil and Gas Compact Commission). (2008). Protecting our country's resources: The states' case,
orphaned well plugging initiative, http://iogcc.myshopify.com/products/protecting-our-countrys-resources-the-states-
case-orphaned-well-plugging-initiative-2008.
Kell, S. (2011). State oil and gas agency groundwater investigations and their role in advancing regulatory reforms,
a two-state review: Ohio and Texas. Ground Water Protection Council, http://fracfocus.org/sites/default/files/
publications/state_oil_gas_agency_groundwater _investigations_optimized.pdf.
Konschnik, K; Dayalu, A. (2016). Hydraulic fracturing chemicals reporting: Analysis of available data and
recommendations for policymakers. Energy Policy 88:504-514. http://dx.doi.Org/10.1016/j.enpol.2015.ll.002.
Louisiana Groundwater Resources Commission. (2012). Managing Louisiana's groundwater resources: An interim
report to the Louisiana Legislature. Baton Rouge, LA: Louisiana Department of Natural Resources. http://dnr.louisiana.
gov/index.cfm?md=pagebuilder&tmp=home&pid=907.
Maupin, MA; Kenny, JF; Hutson, SS; Lovelace, JK; Barber, NL; Linsey, KS. (2014). Estimated use of water in the United
States in 2010. (USGS Circular 1405). Reston, VA: U.S. Geological Survey, http://dx.doi.org/10.3133/cirl405.
Olson, JE. (2011). Hydraulic fracturing overview. Presented at Summer Institute B: Energy, Climate and Water in the 21st
Century, TXESS Revolution, Texas Earth and Space Science Revolution Professional Development for Educators, June
2011, Austin, TX. http://www.txessarchive.org/documents/K_hydraulicfracturingoverview_ppt.pdf.
Otton, JK; Zielinski, RA; Smith, BD; Abbott, MM. (2007). Geologic controls on movement of produced-water releases at
U.S. geological survey research Site A, Skiatook Lake, Osage County, Oklahoma. Applied Geochemistry 22:2138-2154.
http://dx.doi.Org/10.1016/j.apgeochem.2007.04.015.
Pennsylvania Department of Environmental Protection. (2015a). Oil and gas reporting website, statewide data
downloads by reporting period. Waste and production files downloaded for Marcellus/unconventional wells, July 2009
through December 2014. Harrisburg, PA. https://www.paoilandgasreporting.state.pa.us/publicreports/Modules/
DataExports/DataExports.aspx.
Scanlon, BR; Reedy, RC; Nicot, JP. (2014). Will water scarcity in semiarid regions limit hydraulic fracturing of shale plays?
Environmental Research Letters 9. http://dx.doi.Org/10.1088/1748-9326/9/12/124011.
Tidwell, VC; Zemlick, K; Klise, G. (2013). Nationwide water availability data for energy-water modeling. Albuquerque,
New Mexico: Sandia National Laboratories, http://prod.sandia.gov/techlib/access-control.cgi/2013/139968.pdf.
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U.S. EPA (U.S. Environmental Protection Agency). (2011). Plan to study the potential impacts of hydraulic fracturing on
drinking water resources [EPAReport], (EPA/600/R-11/122). Washington, DC: Office of Research and Development.
http://www2.epa.gov/hfstudy/plan-study-potential-impacts-hydraulic-fracturing-drinking-water-resources-
epa600r-11122.
U.S. EPA (U.S. Environmental Protection Agency). (2015a). Analysis of hydraulic fracturing fluid data from the FracFocus
Chemical Disclosure Registry 1.0 [EPA Report], (EPA/601/R-14/003). Washington, DC: Office of Research and
Development, http://www2.epa.gov/hfstudy/analysis-hydraulic-fracturing-fluid-data-fracfocus-chemical-disclosure-
registry-l-pdf.
U.S. EPA (U.S. Environmental Protection Agency). (2015b). Case study analysis of the impacts of water acquisition for
hydraulic fracturing on local water availability [EPA Report], (EPA/600/R-14/179). Washington, DC: Office of Research
and Development, https://www.epa.gov/hfstudy/case-study-analysis-impacts-water-acquisition-hydraulic-fracturing-
local-water-availability.
U.S. EPA (U.S. Environmental Protection Agency). (2015c). Review of state and industry spill data: Characterization
of hydraulic fracturing-related spills [EPA Report], (EPA/601/R-14/001). Washington, DC: Office of Research and
Development, http://www2.epa.gov/hfstudy/review-state-and-industry-spill-data-characterization-hydraulic-
fracturing-related-spills-1.
U.S. EPA (U.S. Environmental Protection Agency). (2015d). Review of well operator files for hydraulically fractured oil
and gas production wells: Well design and construction [EPA Report], (EPA/601/R-14/002). Washington, DC: Office of
Research and Development, http://www2.epa.gov/hfstudy/review-well-operator-files-hydraulically-fractured-oil-and-
gas-production-wells-well-design.
U.S. EPA (U.S. Environmental Protection Agency). (2016). Technical development document for the effluent limitations
guidelines and standards for the oil and gas extraction point source category. (EPA-820-R-16-003). Washington, DC:
Office of Water, http://water.epa.gov/scitech/wastetech/guide/oilandgas/unconv.cfm.
Veil, J. (2015). U.S. produced water volumes and management practices in 2012. Oklahoma, City, OK: Ground Water
Protection Council. http://www.gwpc.org/sites/default/files/Produced%20Water%20Report%202014-GWPC_0.pdf.
Whittemore, DO. (2007). Fate and identification of oil-brine contamination in different hydrogeologic settings. Applied
Geochemistry 22:2099-2114. http://dx.doi.Org/10.1016/j.apgeochem.2007.04.002.
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Photo Credits
Front cover (top): Illustrations of activities in the hydraulic fracturing water cycle. From left to right: Water
Acquisition, Chemical Mixing, Well Injection, Produced Water Handling, and Wastewater Disposal and Reuse.
Front cover (bottom): Aerial photographs of hydraulic fracturing activities. Left: Near Williston, North
Dakota. Image ©J Henry Fair / Flights provided by LightHawk. Right: Springville Township, Pennsylvania.
Image ©J Henry Fair / Flights provided by LightHawk.
Front cover (inside): ©Daniel Hart Photography (2013). Used with permission.
Back cover (inside): Daniel Hart, U.S. EPA.
Back cover: Top left image courtesy of U.S. DOE/NETL. All other images courtesy of the U.S. EPA.
Preferred Citation
U.S. EPA (U.S. Environmental Protection Agency). 2016. Hydraulic Fracturing for Oil and Gas: Impacts from
the Hydraulic Fracturing Water Cycle on Drinking Water Resources in the United States. Executive Summary.
Office of Research and Development, Washington, DC. EPA/600/R-16/236ES.
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