Background about fracking - CUSTOM WRITING PROFESSOR

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First of all i need three main things 1- History2- What used to be done before fracking3- modren frackingplease use reliable sources such as academic journals , im gonna attach three sources it may help . `i need APA citation. Please use figures and talk about them . I need almost 1200 words or 4-5 pages . please include the references that you used

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ENVIRONMENTS & HEALTH
By Ruth McDermott-Levy, PhD, RN,
Nina Kaktins, MSN, RN, and
Barbara Sattler, DrPH, RN
Fracking, the Environment, and Health
New energy practices may threaten public health.
M
elissa Owen became concerned when her
10-year-old son developed such severe nosebleeds that she used tampons to stop the
bleeding. Soon after, a blistering rash appeared on
his skin, and his sister began having similar nosebleeds. The Colorado family’s physician attributed
these symptoms to air pollution caused by the use of
hydraulic fracturing—“fracking”—to extract natural gas in their community. He recommended they
move.
In northeastern Pennsylvania, the Micelles family
thought signing a lease to allow fracking operations
on their farm would relieve some of their financial
burden. But within the first week of drilling, Elizabeth
Micelles noticed a sweet odor and a metallic taste in
her mouth; by the second week, she and her husband
and three children were experiencing fatigue, dizziness, vomiting, headaches, and nosebleeds. A visit to
their NP and laboratory tests revealed that each had
measurable levels of benzene, a known human carcinogen, in their blood.
These acute health problems are common among
people living in communities in which “unconventional” oil and natural gas extraction, such as fracking, occurs. (These examples are composites based on
the experiences of families affected by fracking as
compiled by the Damascus Citizens for Sustainability.1) Common symptoms or complications among
people living near fracking sites include2-4
• fatigue.
• burning eyes.
• dermatologic irritation.
• headache.
• upper respiratory (difficulty breathing), gastrointestinal (severe abdominal pain), musculoskeletal
(backache), neurologic (confusion, delirium),
immunologic, sensory (smell and hearing), vascular, bone marrow (nosebleeds), endocrine, and
urologic problems.
• the risk of endocrine disruption.
• changes in quality of life and sense of well-being.
Longitudinal reports from long-term exposure to contaminated air and water from gas extraction don’t
exist, but anecdotal reports make clear that the removal of fossil fuels from the earth directly affects
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human health. It’s well known, for instance, that the
combustion of fossil fuels emits greenhouse gases that
contribute to climate change,5 and increased rates of
asthma, cardiovascular disease, and lung cancer are all
associated with our reliance on and use of fossil fuel
energy, including coal, oil, and natural gas.2, 6-8
Children are at higher risk than adults for developing asthma and suffering complications from asthma
owing to poor air quality, which can be caused by the
burning of fossil fuels.9, 10 As the population ages,
older adults become more vulnerable to climaterelated extremes in temperature and ambient air
pollution from fossil fuels because of comorbidities
and age-related changes, such as decreased respiratory reserve and the slowing of cardiac compensatory mechanisms.11-14 Moreover, there are numerous
occupational hazards for the fossil fuel extraction
workforce, ranging from noise concerns15, 16 to major injuries17 and respiratory irritants that result in
chronic disease.18
Despite these health concerns and efforts to institute a moratorium on fracking until its environmental and health effects are better understood, the United
States continues to rely heavily on fossil fuel energy.
Currently, 36% of annual U.S. energy consumption
is derived from petroleum, 26% from natural gas,
20% from coal, and 8% from nuclear sources, with
only 9% supplied by renewable energy, such as wind
and solar power.19 President Obama’s administration has repeatedly emphasized its plan to continue
development of all energy sources—including a significant expansion of drilling and fracking operations
for natural gas and oil. Although the extraction of
these nonrenewable sources of energy help the United
States to meet its current energy demands and security needs, it’s critical that the human and ecologic
health threats associated with fracking be better understood and addressed.
FRACKING
Extracting natural resources trapped within the pore
spaces of low-permeable rock, such as shale, typically requires drilling deep—up to 8,000 feet.20 Using
a process called high-volume hydraulic fracturing,
or fracking, areas of weakness and small fractures
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ENVIRONMENTS & HEALTH
When Jodie Simons and Jason Lamphere put a lighter to their faucet, the high methane content of the water sets it on fire. Since
gas drilling started in their Pennsylvania neighborhood, they’ve been without clean drinking or bathing water. High levels of methane
in drinking water can create a risk of explosions and asphyxiation hazards for households. Photo by Nina Berman / NOOR / Redux.
that already exist in the rock are further opened. Depending on the characteristics and depth of the rock,
fracking a single well requires the high-pressure injection of anywhere from 2 to 10 million gallons of
water mixed with sand21 and 80 to 300 tons of hazardous and nonhazardous chemicals.22
Colborn and colleagues compiled a list of chemicals known to be used during natural gas extraction.3
Of the more than 350 that were investigated further,
75% were found to potentially affect the respiratory
and gastrointestinal systems, the liver, and various
sensory organs. Moreover, more than half of these
chemicals could affect the brain and nervous system.3
It’s estimated that 15% to 80% of the fluid containing
these chemicals flows back through the well to the
surface,20 where it’s usually stored at the well site in
tanks or open, lined pits, awaiting transport to treatment facilities or to deep-well injection sites for permanent disposal.
Fracking operations have grown exponentially
since the mid-1990s, when technologic advances
and increases in the price of natural gas made this
technique economically viable. Fracking is currently
taking place in Arkansas, California, Colorado,
Louisiana, North Dakota, Oklahoma, Pennsylvania, Texas, Virginia, West Virginia, and Wyoming.
Other states, such as Alabama, Indiana, Maryland,
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Michigan, Mississippi, New Jersey, New York, and
Ohio, are either considering or preparing for drilling using this method. Vermont has permanently
banned fracking, and New York and North Carolina
have instituted temporary bans. New Jersey currently
has a bill before its legislature to extend a 2012 moratorium on fracking that recently expired, whereas
Maryland has decided not to approve fracking permits
until a state panel studying its safety has completed
its final report, which is expected in mid-2014. Although a fracking moratorium was recently lifted in
the United Kingdom, the government is proceeding
cautiously because of concerns about earthquakes
and the environmental impact of drilling. Fracking
is currently banned in France and Bulgaria.
HEALTH RISKS
It’s believed that the potential health consequences of
fracking begin at the onset of drilling and may last
long after the operation has concluded. Researchers
have described an array of environmental factors and
health risks associated with fracking and other extraction processes.6, 23, 24 These include water and air
contamination; increased intensity in diesel-truck traffic volume; constant, elevated noise levels; occupational hazards; and stress within rural communities
from a swelling population made up of drilling crews
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Figure 1. In hydraulic fracturing, or fracking—the method used to extract gas from shale deposits—rock
layers are fractured by fluids (a mixture of sand, chemicals, and water) pumped under high pressure from the
surface (upper left) down through horizontal wells (lower right) to form fissures in the shale. The sand
keeps the fissures open, allowing the gas to flow into the well and be taken to the surface. Image by Gary
Hincks / Science Source Images.
and related businesses, and the subsequent increased
demands on the social and health care infrastructures.23
There are also potential economic and ecologic
issues, including decreased property values owing to
drilling site proximity, drilling malfunctions, and violations of regulations designed to protect the environment, which could lead to long-term environmental
and health damages to the surrounding community. Furthermore, compared with conventional gas
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extraction methods, the fracking process leads to
what’s believed to be a 30% greater amount of methane “escape.”25 Methane can also leak from the well
and during natural gas processing, transport, storage, and distribution.25
Water contamination. People obtain drinking water from either surface water, which includes rivers
and reservoirs, or groundwater aquifers, accessed
by public or private wells. There are already a host of
documented instances in which nearby groundwater
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ENVIRONMENTS & HEALTH
has been contaminated by fracking activities, requiring residents with private wells to obtain outside
sources of water for drinking and everyday use.26, 27
A primary health hazard is methane migration
from active drilling sites to aquifers. In Pennsylvania,
Osborn and colleagues found that the average methane level was 17 times higher in private drinking-water
wells within one kilometer, or about 3,280 feet, of active drilling sites, compared with those in nondrilling
areas.26 High levels of methane in drinking-water
supplies create a risk of explosions and asphyxiation
hazards for households. In one case, the buildup of
methane caused a private drinking-water well to explode.27 Currently, the U.S. Environmental Protection
Agency (EPA) doesn’t regulate methane in drinking
water, and there is a lack of research on the health
effects of chronic exposure to methane in drinking
water.28
Methane is only one of many chemicals of concern. In Pavillion, Wyoming, the EPA detected high
concentrations of benzene, xylenes, purgeable hydrocarbons, and gasoline and diesel by-products in shallow groundwater near fracking-wastewater holding
pits.29 Collectively, these chemicals present risks of
neurotoxicity, reproductive problems, and cancer.30-32
The EPA determined that the most likely cause of the
groundwater contamination was leaky pits used to
store fracking fluid waste.29 Groundwater contamination from toxic drilling wastewater poses a health
risk to humans, as well as to pets and farm animals
that drink or bathe in the contaminated water.
Despite the evidence of health risks related to
fracking, communities and health care providers have
had limited access to information about the chemicals used in the hydraulic fracturing process, as well
as limits placed on their ability to inform and share
information about chemical exposures. For example, Pennsylvania’s Act 13 of 2012 states that drilling
companies are not required to share information
about the components or concentration of chemicals
if these are deemed proprietary trade secrets.33 This
act also requires that health professionals submit a
written request for information on proprietary solutions used in fracking and sign a “confidentiality
agreement” identifying that the information is needed
to diagnose or treat an individual.
Although exceptions are made for emergency
situations, these policies delay nurses’ and other
health care providers’ ability to quickly assess and
treat the public or extraction workforce for potentially hazardous exposures. Furthermore, the Pennsylvania law states that health care professionals
are not permitted to share exposure information.
This hinders the development of effective, evidencebased assessment and treatment practices related to
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the health effects of these chemicals on exposed patients.33
Air pollution. The air is significantly impacted by
fracking operations, including by the release of methane, which is especially likely during the initial period following hydraulic fracturing injection and
during transport of the fuel to customers.25 Public
health threats related to climate change, which is
partly a function of the continued release of greenhouse gases like methane, are forecast to be one of
the greatest global health concerns of this century.5
Moreover, high levels of known carcinogens in the
air, such as benzene, have been attributed to natural
gas drilling operations.6
The large fleets of diesel trucks (typically 1,000
to 2,000 per well) that are required to support the
fracking process significantly increase ground level
ozone and particulate matter15, 34 as well as the risk
of traffic accidents.35 Ground level ozone is a potent
pulmonary irritant responsible for reduced pulmonary function and the exacerbation of asthma and
emphysema.36, 37 Elevations in particulate matter are
responsible for an increased incidence of asthma,38
cardiovascular disease,39 chronic obstructive pulmonary disease, and cancer.40
Occupational hazards. Statistics collected by the
Department of Labor and analyzed by the Centers
for Disease Control and Prevention show a correlation
between drilling activity and the number of occupational injuries related to drilling and motor vehicle
accidents, explosions, falls, and fires.17 Extraction
workers are also at risk for developing pulmonary
diseases, including lung cancer and silicosis (the latter because of exposure to silica dust generated from
rock drilling and the handling of sand).41 At the well
sites, workers can be exposed to dangerously high
levels of silica—as many as 79% of hydraulic fracturing sites exceed the National Institute for Occupational Safety and Health standards for silica dust.18
Additionally, the extraction workforce is at increased risk for radiation exposure. Fracking activities often require drilling into rock that contains
naturally occurring radioactive material (NORM),
such as radon, thorium, and uranium.42-44 Rock cuttings containing NORM may be buried at the drilling site or taken to a landfill. However, NORM is
also brought to the surface intermingled with fracking fluids and subsequently deposited in open lined
pits or holding tanks as waste.21 While awaiting permanent disposal, the radioactive materials become
concentrated, producing “technologically enhanced
NORM” (TENORM).21, 44 Workers may be exposed
to TENORM at the drilling site or through the spilling
of waste material during transport; and while many
TENORM contains low levels of radiation, extraction
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workers and people living near drill sites can potentially be exposed to elevated levels of radiation.44
THE ANA’S STANCE
The “precautionary principle” or approach was developed in recent decades in response to the perceived
risk to health and the environment posed by certain
activities. This concept places the burden of proving
that an activity is safe for human health or the environment, in the absence of scientific consensus, on
the entity initiating the activity. This principle has
been embraced by the American Nurses Association
(ANA), which in 2003 adopted a policy that states
that when there’s an environmental threat to human
health, nurses must advocate for public policies that
reduce risk to people and the natural environment.45
Evidence-Based Resources on
Fracking and Its Health Impacts
Alliance of Nurses for Healthy Environments
A Web forum on fracking and public health.
http://bit.ly/ZYFBaU
American Public Health Association
Policy Statement: The Environmental and
Occupational Health Impacts of High-Volume
Hydraulic Fracturing of Unconventional Gas
Reserves.
http://bit.ly/TYv13W
Natural Resources Defense Council
Information on the health impacts of natural gas
extraction and climate change.
www.nrdc.org/energy/gasdrilling
Physicians, Scientists, and Engineers for
Healthy Energy
Learning models and continuing education
about the health effects of shale gas extraction.
www.psehealthyenergy.org
Southwest Pennsylvania Environmental
Health Project
Information and assessment tools for health care
providers working in gas extraction communities.
www.environmentalhealthproject.org
U.S. Environmental Protection Agency
“Questions and answers about EPA’s hydraulic
fracturing study.”
http://1.usa.gov/ZvvI5x
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The ANA’s policy says: “the Precautionary Principle
implies that there is an ethical imperative to prevent
rather than merely treat disease, even in the face of scientific uncertainty.”
In June 2012, the ANA passed a resolution drafted
by the Pennsylvania State Nurses Association entitled
“Nurses’ Role in Recognizing, Educating and Advocating for Healthy Energy Choices.”45-47 It calls for
a national moratorium on new drilling permits for
unconventional natural gas and oil extraction based
on mounting evidence that fracking leads to human
health threats, disruption in communities, and ecologic degradation. It emphasizes the need for nurses
to be well versed in the health risks associated with
fossil fuel energy and supports their engagement in
patient and community education as well as in policy and advocacy work. The resolution asserts that it’s
critical for nurses to know that safer energy options—
such as wind, hydroelectric, solar, and geothermal
power— exist, and that state and national policies can
help or hinder whether the use of these alternative energy sources is explored.
NURSING IMPLICATIONS
Addressing our national energy needs while assuring
the health of communities and the extraction workforce is a complex and multifaceted issue. Nurses can
best promote the health of their patients, the community, and the public by embracing the precautionary
approach and supporting energy policies that make
human health a priority. The ANA’s resolution calling for a moratorium on drilling permits provides a
framework for nurses looking to influence energy policy, and calls for self-education and active support
of legislation that would require better monitoring
and regulation of the fossil fuel industry, particularly
in regard to its effect on health.
Nursing and other health professional groups,
such as the Alliance of Nurses for Healthy Environments, in addition to federal agencies, have published resources on fracking (see Evidence-Based
Resources on Fracking and Its Health Impacts). Using these, nurses can gain a better understanding of
the issues surrounding fracking and help to educate
their colleagues, patients, and other members of
their communities while also taking the lead in promoting better monitoring and prevention of the potential health effects associated with fracking.48 Two
of us (RM-L and NK), for example, have previously
suggested that community health nurses in Pennsylvania, where there is extensive fracking operations
on the Marcellus shale, incorporate evaluation of
exposure risk (to air or water that may have been
contaminated by drilling operations) into their patient assessments.48
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ENVIRONMENTS & HEALTH
Public and individual health concerns are rarely
raised when energy policies are discussed on the
state or federal level, and health professionals are
typically excluded from these decision-making discussions. As Goldstein and colleagues noted last year,
none of the advisory committees formed to investigate drilling activities on the Marcellus shale included
representatives of state or federal public health agencies or individuals with expertise in the effects of environmental hazards on human health.49
Nurses are being joined in their efforts by a wide
range of stakeholders, ranging from the health professionals in the American Public Health Association
and Physicians for Social Responsibility, to national
organizations such as Breast Cancer Action and Food
and Water Watch, to grassroots organizations such
as Catskill Mountainkeeper and Frack Free Stark
County. Many of the well-known national environmentalist organizations are actively engaged as well,
such as the Sierra Club, the Nature Conservancy, and
the Natural Resources Defense Council. National
Nurses United and the ANA have both called for banning new fracking permits. These two nursing organizations have constituents throughout the country
who are engaged in legislative and other policy initiatives regarding fracking.
Both the Maryland Nurses Association and the
Pennsylvania State Nurses Association have been actively engaged in efforts to address fracking. The national Alliance of Nurses for Healthy Environments
has received several grants to help coordinate nurses’
educational and policy efforts on fracking, to keep
current on scientific studies, and to develop nursing
spokespeople and leadership around this critical
issue.
Increasingly, we are seeing nurses on boards, commissions, and advisory councils for environmental
health. The national Children’s Environmental Health
Network has a nurse on its board of directors, and
the EPA’s Children’s Health Protection Advisory Committee has several nurses. Maryland’s Commission on
Environmental Justice and Sustainable Communities
also includes several nurses. Ensuring that nurses are
involved with these councils and commissions requires that we be proactive, contacting the chairpersons and staff of such bodies, finding out when a seat
will become available, having a state or national
nurses association make a nomination or support a
nomination, and, or course, finding nurses willing
to take on these roles.
Evidence of the negative human and ecologic
health effects of fracking are emerging, and it should
be noted that sufficient evidence has been presented
to the ANA, the American Public Health Association,
and the American Medical Association’s Resident
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and Fellow Section to result in a call for a moratorium on the issuance of new fracking permits nationally. Nurses’ voices in our communities, in state
legislatures, in Congress, and with the EPA can help
to keep health issues front and center as we address
national energy needs and policies. ▼
Ruth McDermott-Levy is an assistant professor at the Villanova
University College of Nursing, Villanova, PA; Nina Kaktins is
an adjunct nursing professor at the Chatham University College
for Continuing and Professional Studies, Pittsburgh, PA; and
Barbara Sattler is a professor at the University of San Francisco
School of Nursing and Health Professions. Contact author: Ruth
McDermott-Levy, ruth.mcdermott.levy@villanova.edu. The authors have disclosed no potential conflicts of interest, financial
or otherwise.
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Agency; 2008 Apr. EPA-402-R-08-005. http://www.epa.
gov/rpdweb00/docs/tenorm/402-r-08-005-volii/402-r-08005-v2.pdf.
44. U.S. Environmental Protection Agency. About TENORM.
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45. American Nurses Association. ANA’s principles of environmental health for nursing practice with implementation
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Practice.pd.
46. American Nurses Association, House of Delegates. Resolution: nurses’ role in recognizing, educating and advocating for
healthy energy choices. Silver Spring, MD; 2012. http://www.
nursingworld.org/MainMenuCategories/WorkplaceSafety/
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Issues.
47. Pennsylvania State Nurses Association. Nurses promote healthier energy choices. 2012. http://psna.org/2012/07/nursespromote-healthier-energy-choices.
48. McDermott-Levy R, Kaktins N. Preserving health in the Marcellus region. Pa Nurse 2012;67(3):4-10.
49. Goldstein BD, et al. Missing from the table: role of the environmental public health community in governmental advisory
commissions related to Marcellus Shale drilling. Environ
Health Perspect 2012;120(4):483-6.
AJN ▼ June 2013
▼
Vol. 113, No. 6
51
5/9/13 2:10 AM
In This Issue:
ET&C FOCUS
Focus articles are part of a regular series intended to sharpen understanding of current and
emerging topics of interest to the scientific community.
Hydraulic “Fracking”: Are Surface Water Impacts An
Ecological Concern?
G. Allen Burton Jr.,*y Niladri Basu,z Brian R. Ellis,x Katherine E. Kapo,k Sally Entrekin,# and
Knute Nadelhofferyy
ySchool of Natural Resources and Environment, University of Michigan, Ann Arbor, Michigan, USA
zAgricultural and Environmental Sciences, McGill University, Montreal, Quebec, Canada
xDepartment of Civil and Environmental Engineering, University of Michigan, Ann Arbor, Michigan, USA
kWaterborne Environmental Inc., Leesburg, Virginia, USA
#Department of Biology, University of Central Arkansas, Conway, Arkansas, USA
yyDepartment of Ecology and Evolutionary Biology, University of Michigan Ann Arbor, Michigan, USA
Abstract—Use of high-volume hydraulic fracturing (HVHF) in
unconventional reservoirs to recover previously inaccessible oil and
natural gas is rapidly expanding in North America and elsewhere.
Although hydraulic fracturing has been practiced for decades, the advent
of more technologically advanced horizontal drilling coupled with
improved slickwater chemical formulations has allowed extensive
natural gas and oil deposits to be recovered from shale formations.
Millions of liters of local groundwaters are utilized to generate extensive
fracture networks within these low-permeability reservoirs, allowing
extraction of the trapped hydrocarbons. Although the technology is
relatively standardized, the geographies and related policies and
regulations guiding these operations vary markedly. Some ecosystems
are more at risk from these operations than others because of either their
sensitivities or the manner in which the HVHF operations are conducted.
Generally, the closer geographical proximity of the susceptible ecosystem
to a drilling site or a location of related industrial processes, the higher
the risk of that ecosystem being impacted by the operation. The associated
construction of roads, power grids, pipelines, well pads, and waterextraction systems along with increased truck trafﬁc are common to
virtually all HVHF operations. These operations may result in increased
erosion and sedimentation, increased risk to aquatic ecosystems from
chemical spills or runoff, habitat fragmentation, loss of stream riparian
zones, altered biogeochemical cycling, and reduction of available surface
and hyporheic water volumes because of withdrawal-induced lowering of
local groundwater levels. The potential risks to surface waters from
HVHF operations are similar in many ways to those resulting from
* Address correspondence to burtonal@umich.edu.
Published online in Wiley Online Library
(wileyonlinelibrary.com). DOI: 10.1002/etc.2619
# 2014 SETAC
agriculture, silviculture, mining, and urban development. Indeed,
groundwater extraction associated with agriculture is perhaps a larger
concern in the long term in some regions. Understanding the ecological
impacts of these anthropogenic activities provides useful information for
evaluations of potential HVHF hazards. Geographic information system–
based modeling combined with strategic site monitoring has provided
insights into the relative importance of these and other ecoregion and
land-use factors in discerning potential HVHF impacts. Recent ﬁndings
suggest that proper siting and operational controls along with strategic
monitoring can reduce the potential for risks to aquatic ecosystems.
Nevertheless, inadequate data exist to predict ecological risk at this time.
The authors suggest considering the plausibility of surface water hazards
associated with the various HVHF operations in terms of the ecological
context and in the context of relevant anthropogenic activities. Environ
Toxicol Chem 2014;33:1679–1689. # 2014 SETAC
Keywords—Aquatic toxicity; Fracking; Water-quality stressor; Ecological
risk assessment
Introduction
The world’s energy marketplace is shifting, and natural gas is
becoming more prominent. This shift is driven by globally
abundant natural gas reserves (Figure 1) and newfound
extraction technologies such as high-volume hydraulic
fracturing (HVHF) operations targeting shale gas (and oil)
formations, coupled with mounting health, environmental, and
geopolitical concerns over alternatives such as oil, coal, and
nuclear energy sources. This shift includes, for example, new
jobs, increased economic activity, and a more diverse and
stable energy base. The shift may also reduce emissions of
Environmental Toxicology and Chemistry, Vol. 33, No. 8, August, 2014
1679
FIGURE 1: Areal extent as indicator of potential geographic footprint. Technically recoverable shale oil and shale gas resources from across
41 countries [22].
CO2 and other greenhouse gases, as well as criteria air
pollutants such as mercury. Contentions and challenges do
exist, however, and many of these require better understanding
of the environmental risks that may occur throughout the life
cycles of natural gas extraction or other energy technologies.
The present ET&C Focus article addresses the plausibility of
primary environmental concerns (Figure 2) related to surface
waters (and their groundwater interactions) that may occur if
inadequate precautions are taken for HVHF operations and their
siting. Many of these concerns are similar to those associated
with other anthropogenic activities, such as silviculture,
agriculture, mining, and urban development. In the United
States, approximately 20% (442 million acres) of the land area is
cropland, and 3% (69 million acres) is urban [1]. Environmental
concerns associated with surface water and groundwater are
driven largely by the sensitivity of the ecoregion to perturbations
and the density of the HVHF operations.
Most of the attention on HVHF operations has related to the
potential for groundwater contamination from the hydraulic
fracturing ﬂuid additives and the release of methane into
groundwaters and, more recently, the atmosphere [2]. Activities associated with HVHF that potentially impact surface
waters can be grouped into 3 areas: 1) spills and releases of
produced water and chemicals from hydraulic ﬂuids, 2)
erosion from surface disturbances, and 3) altered surface water
ﬂows resulting from excessive surface water or groundwater
withdrawals. Nevertheless, oil and gas development, whether
from conventional or unconventional reservoirs, may also
contribute to erosion, carrying loads of sediments and/or
1680
chemicals of concern into waters [3–8]. Onsite precautions
during drilling operations are needed to lower the risk of
chemical spills caused by tank ruptures, blowouts, equipment
or impoundment failures, overﬁlls, vandalism, accidents
(including vehicle collisions), ground ﬁres, or operational
errors.
Hydraulic fracturing ﬂuids contain a range of additives,
including proppants, gelling agents, solvents, antiscalants,
surfactants, corrosion inhibitors, and biocides (see Table 1).
Some additives are known to be toxic; but toxicological data
are limited regarding other additives, and not all degradation
pathways and products of reactive additives are known.
Furthermore, there is a potential for trace contaminants to be
leached from the fractured shale and transported to the surface
with the ﬂowback and produced brine. Drill cuttings that
are stored onsite and high-brine produced waters are 2 of the
biggest threats to surface water quality.
Why the Concern?
When are these potential problems a signiﬁcant ecological
concern for surface waters? The nature of hydraulic fracturing
means that ecological impacts will manifest in a variety of
manners (Figure 2). From the construction of new roads and
infrastructure to the use and release of harmful pollutants, the
resulting activities may have profound effects on a region’s
ecosystems and organisms; and these effects may change
from the near term to the longer term. The assessment and
management of such surface water impacts will undoubtedly
beneﬁt from a better understanding of their plausibility for
Environmental Toxicology and Chemistry, Vol. 33, No. 8, August, 2014
FIGURE 2: Ranges indicate a dependence on the ecological context and/or operational controls. Potential for ecological hazards (1 ¼ low potential,
3 ¼ high potential). NORM ¼ naturally occurring radioactive material.
potential adverse effects in the context of ecosystem sensitivities
and impacts of other anthropogenic activities. In this section, we
brieﬂy outline the most pertinent ecological impacts.
Rapid and concentrated HVHF development near small
streams has the potential to degrade surface water quality,
just as many anthropogenic activities do. The US Environmental Protection Agency’s (USEPA’s) evaluations of
State 305b reports suggests that the majority of aquatic life
impairments are the result of nonpoint-source runoff in
human-dominated watersheds [9]. A ranking of the top causes
of stream impairment (from greatest to least) is as follows:
pathogens, sediment, nutrients, and organic enrichment/
oxygen depletion. The USEPA lists the national probable
sources of impaired streams as (from greatest to least)
agriculture, unknown sources, atmospheric deposition, hydromodiﬁcation, urban area–related runoff, municipal discharges,
natural/wildlife, other habitat alterations, resource extractions,
and silviculture. Evaluations of fracturing operations in central
Arkansas found that surface water–quality violations at site
operations were caused by erosion (22%), illegal discharges
(10%), and spills (10%). Impacts to receiving water streams
and their biota were signiﬁcantly linked to well and pad
densities, rates of installation, distance from well pads to
stream channels, pipeline density, and a combination of roads/
pasture and well density proximity. One critical factor is that
gas wells are often located adjacent to small streams. In shale
basins with a high density of HVHF operations, numerous
well pads may be located within the same watershed, thus
compounding the cumulative impacts of industrial activity
within that particular watershed. To date, most federally
funded research on environmental impacts of hydraulic
fracturing has focused on contamination of groundwater and
drinking water sources. However, fewer data are available to
address concerns associated with surface water and terrestrial
ecosystems. The ongoing studies of Entrekin (S. Entrekin,
unpublished data) (see sidebar Assessment of High-Volume
Hydraulic Fracturing Impacts on Streams: A Case Study
Example) highlight the need for comprehensive scientiﬁc
evaluations of the cumulative impacts of fracturing operations
on receiving waters. That study can be considered as
applicable for other basins with similar topographic relief
and climate conditions (e.g., Michigan basin, USA) in regard
to runoff issues associated with site development. Comparisons can be made in the broad similarities of vegetation
percentage, surface cover type, moisture availability, and
amount of runoff to guide future studies in shale plays with
ongoing or impending HVHF development.
Water withdrawals
It is important to consider the connection between water
quantity and quality. Taking water from a small stream
concentrates contaminants in the stream water. If stream ﬂow
is reduced by groundwater withdrawals, the lower dilution rate
of solid loadings or other contaminants from the watershed can
Environmental Toxicology and Chemistry, Vol. 33, No. 8, August, 2014
1681
Table 1. Categories of chemicals used in hydraulic fracturing, their purposes, and example(s) of a commonly used chemicala
Functional category
Diluted acids
Biocide
Purpose
Improve injection and penetration; dissolve minerals and
clays to minimize clogging, open pores, and aid gas flow
Minimizes bacterial contamination of hydrocarbons, reduces
bacterial production of corrosive by-products to maintain
wellbore integrity and prevent breakdown of gellants
Example(s) of chemical
Hydrochloric acid
Glutaraldehyde
Breaker
Added near end of sequence to assist flowback from
wellbore, breaks down gel polymers
Ammonium persulfate
Clay stabilizer
Establishes fluid barrier to prevent clays in formation from
swelling, keeps pores open, creates a brine carrier fluid
Maintains integrity of steel casing of wellbore by preventing
corrosion of pipes and casings
Potassium chloride
Corrosion inhibitor
N,N-Dimethylformamide
Crosslinker
Thickens fluid to hold proppant
Borate salts
Defoamer
Foamer
Lowers surface tension and allows gas escape
Reduces fluid volume and improves proppant carrying
capacity
Polyglycol
Acetic acid (with NH4 and
NaNO2)
Friction reducer
Improves fluid flow efficiency through wellbore by reducing
friction between fluid and pipe, alleviates friction caused
by high-pressure conditions
Polyacrylamide
Gel/gellant
Iron control
Thickens fluid (water) to suspend proppant
Prevents materials from hardening and clogging wellbore,
prevents metal oxide precipitation
Guar gum
Citric acid
Oxygen scavenger
Maintains integrity of steel casing of wellbore, protects pipes
from corrosion by removing oxygen from fluid
Controls pH of solution, protects pH-dependent
effectiveness of other chemicals (e.g., crosslinkers)
Ammonium bisulfate
pH adjusting agent/buffer
Sodium carbonate, potassium
carbonate
Proppant
Holds open (props) fractures to allow gas to escape from
shale
Silica, sometimes glass beads
Scale control
Prevents mineral scale formation which can clog wellbore
and block fluid or gas flow
Ethylene glycol
Solvents
Improve fluid wettability or ability to maintain contact
between the fluid and the pipes
Stoddard solvent
Surfactant
Improves fluid flow through wellbore by reducing surface
tension
Isopropanol
a
Information from references [23–26].
damage ecosystems and harm aquatic life. In some regions of
the country where HVHF is occurring, there are concerns that
excessive extraction of surface water and groundwater will
result in periods of water shortage that impact agricultural
irrigation, drinking water wells, or surface water levels. Of
perhaps equal concern are increasing groundwater withdrawals by agriculture resulting in the depletion of aquifer
reservoirs. Some of these agricultural water demands are cooccurring in areas where HVHF operations are increasing,
presenting cumulative demands on water resources that may
impact surface water ﬂows. In Michigan (USA), large-scale
commercial agricultural water withdrawals are increasing as
climate change leads to longer seasons and the ability to
migrate north. Water withdrawals for irrigation purposes
increased between 2010 and 2012 from 85 541 million gallons
to 159 552 million gallons (Figure 3). During that same period,
HVHF water withdrawals increased from 10 million to 55
million gallons (35 million in 2013; Michigan Department of
Environmental Quality, public data). Although groundwater
reservoirs in Michigan are considered abundant, there are
sensitive ﬁsheries, designated as “cold transitional” and “cold
water” streams whose headwaters are shallow. These streams
are particularly at risk from neighboring HVHF operations
1682
during drought and low-ﬂow periods. Careful water-level
monitoring and assessment are critical to protect streams with
sensitive biota, but this is very context-dependent (geographically and ecologically). The following research questions need
to be addressed: Will local hydrologic cycles be altered? How
long before cycles recover? How do water withdrawals impact
ﬁsh during this sensitive time for their survival? Are stream
base ﬂow estimates accurate? What are critical base ﬂows for
headwater streams?
Construction and transportation
Any disturbance of land, such as the planting of crops and
the construction of buildings, increases the likelihood of soil
erosion and subsequent loadings to receiving waters of solids
and associated chemicals. Such is the case with HVHF
operations, which lead to a number of earth-disturbing
activities, such as clearing, grading, and excavating land to
create a pad to support the drilling equipment or other
necessary industrial process materials. In general, well pads
increase the potential for sediment erosion on and off
location [5,6,10]. These newly constructed well pads also
often require construction of access roads to transport
Environmental Toxicology and Chemistry, Vol. 33, No. 8, August, 2014
Assessment of High-Volume Hydraulic Fracturing Impacts
on Streams: A Case Study Example
A geographic information system–based case study characterizing relative ecological risk based on various land-use
factors, including variables related to gas activity, was conducted for the Fayetteville Shale Play in Arkansas
(Figure 4) for 16 watersheds in 2011. Although this exercise is simplistic and limited by data availability, it provides an
example of how associations between land use and potential biological impact may be delineated and integrated to
communicate relative risk.
Components of geographic information system case study for high-volume hydraulic fracturing watershed assessment
Study area
16 watersheds in the Fayetteville Shale (mean drainage area 29 km2 ; minimum ¼ 2.5,
maximum ¼ 84).
Field sampling data
Replicate benthic macroinvertebrate samples (analyzed as community metrics) and
various associated water chemistry parameters (per watershed).
General land-use variables (percentages of pasture, urban, forest), geology (rock
type), soil erodability, road density (paved and unpaved), mean inverse flowpath
length from roads to streams, gas activity including well density and mean inverse
flowpath length from well pads to streams, and pipeline density (per watershed).
Random forest analysis used to evaluate the relationship (relative variable
importance values) between land-use variables (after removing highly correlated
variables) and associated water chemistry and community metrics.
Land-use characteristics
Variable importance ranking
Watershed ranking
(cumulative risk)
Geographic information system spatial overlay conducted to rank watersheds for
potential cumulative ecological impact (e.g., decreased Plecoptera percentage).
Watersheds were represented as rasters for each land-use variable having high
relative variable importance for Plecoptera percentage and simplified to binary
rasters based on the value thresholds for each variable roughly corresponding to
the spatial pattern of decreased Plecoptera percentage (observations below the
75th centile). Each binary watershed raster was then weighted by its mean variable
importance value, and the rasters were aggregated as an overlay map representing
relative rank of potential cumulative ecological impact.
Case study outcomes:
Watershed well density and pipeline density were highly positively correlated (Spearman rho > 0.7) and had a
significant positive correlation to mean inverse flowpath length to unpaved roads.
Based on this exploratory analysis, land-use variables related to gas well development and activity (well density,
mean inverse flowpath length to well pads, and unpaved roads) had relatively high variable importance for the
prediction of conductivity (positive association), which was also highly positively correlated with metals, chloride,
and total suspended solids.
Among the benthic community metrics, Plecoptera percentage (stoneflies, key indicators of water quality) had a
negative relationship with land-use variables related to gas well development and activity compared with other
community metrics, as well as a negative relationship with conductivity.
Watersheds having multiple land-use conditions predictive of decreased Plecoptera percentage (e.g., high mean
inverse flowpath length to unpaved roads, high well density) were ranked with a higher relative impact potential
compared with other watersheds.
equipment and other materials to the site. If sufﬁcient erosion
controls to contain or divert sediment away from surface water
are not established, then surfaces exposed to precipitation and
runoff could carry sediment and other harmful pollutants into
nearby rivers, lakes, and streams. Sediment clouds water,
decreases photosynthetic activity, and scours organisms and
their habitat. In addition, nutrients and other chemicals tend to
sorb to sediments, where they accumulate and can contaminate
overlying waters and biota [11].
Industrial chemicals
Hydraulic fracturing chemicals are transported to drilling
sites in tank trucks and are stored and mixed onsite. The
USEPA has identiﬁed more than 1000 possible chemicals
that may be used in hydraulic fracturing ﬂuids within the
United States [12]. However, most well completions use
about 10 different chemical additives in their particular
slickwater formulations [13]. Although these chemical
additives generally comprise less than 1% by volume of
the total fracturing ﬂuid, a typical high-volume hydraulic
fracturing completion uses several million gallons of ﬂuid,
meaning that many thousands of liters of chemicals will need
to be transported and secured onsite prior to injection.
Chemical and wastewater transport vehicles can potentially
be involved in trafﬁc accidents, and it is estimated that a 30ton tank truck will have an accident every 333 000 kilometers
[10]. Although this does not necessarily mean that chemical
emissions will occur at every site, the potential for release
into the environment remains. Moreover, truck accidents that
Environmental Toxicology and Chemistry, Vol. 33, No. 8, August, 2014
1683
Flowback and produced water
FIGURE 3: Irrigation wells in Michigan drilled from January 2010 to
December 2012. WWAT ¼ water withdrawal assessment tool.
occur on roads could result in chemicals being spilled
on unpaved areas and draining into surface water and
groundwater [10].
Chemicals are integral to the hydraulic fracturing process and
perform a number of functions, yet they have intrinsic toxic
properties that raise concerns. In the absence of empirical
evidence from toxicity studies, researchers have inferred the
potential for harm by studies that have identiﬁed constituent
chemicals and cross-referenced them with known or
suspected health effects. Although performed for human
health, the outcomes of such studies have applicability to
ecotoxicology. The Endocrine Disruption Exchange identiﬁed and classiﬁed chemicals using Chemical Abstracts
Service numbers and comparing them against databases (e.g.,
MSDS sheets, TOXNET) to increase understanding of
plausible health effects. More than 75% of the chemicals
were shown to possibly affect the respiratory and gastrointestinal systems as well as eyes, skin, and other sensory
organs. Nearly half (40–50%) of the chemicals could affect
the neurological, immune, cardiovascular, and renal systems.
One-fourth of the chemicals were known, probable, or
possible carcinogens. Finally, 37% of the identiﬁed chemicals could have effects on the endocrine system. The
researchers also noted that 44% of the chemicals were not
evaluated because they were not disclosed or they did not
have adequate toxicological data. However, the importance
of these knowledge gaps must be considered in terms of their
ecological and geographic context as well as state regulatory
controls.
1684
Water that is produced from hydraulic fracturing activities will
form a signiﬁcant waste stream. Management of this waste
often requires extensive trucking to offsite injection wells.
Regulations govern the proper handling of this waste stream,
with the most common method of disposal being deep well
injection via brine disposal wells. Alternatives to deep well
injection of ﬂowback and produced water include reuse for
additional hydraulic fracturing completions or treatment at
industrial wastewater treatment facilities. In areas such as
Pennsylvania (USA), where only a few brine injection wells
are available to accept wastewaters, reuse of ﬂowback water is
becoming the dominant management strategy [14]. Prior to
mid-2010 some publically owned treatment works in the
Marcellus region were accepting ﬂowback waters and were
unable to remove the high concentrations of dissolved salts.
This practice led to discharge of high-salinity treated efﬂuent to
receiving waterways. Speciﬁc problems associated with this
practice include elevated bromide in drinking water intake
streams, which can lead to the formation of brominated
disinfection byproducts in treated drinking water [15] and
concentration of radium in river sediments near wastewater
treatment outﬂows [16]. The use of publically owned treatment
works in Pennsylvania to treat ﬂowback waters has since been
all but discontinued because of these environmental concerns
and treatment challenges [14]; in Arkansas (USA), however,
surface discharge is permitted following onsite treatment.
In locations where naturally occurring radioactive material–
bearing produced water and solid wastes are generated,
mismanagement of these wastes can result in radiological
contamination of soils or surface water bodies [12,16–18].
Elevated concentrations of naturally occurring radioactive
materials, most commonly 226Ra and 228Ra, have been observed
in ﬂowback waters [19]. Naturally occurring radioactive
material waste problems are generally associated with longterm operations of oil and gas ﬁelds because of buildup of
mineral scaling, such as BaSO4 in which Ra is coprecipitated,
in production equipment. Proper management of naturally
occurring radioactive material–bearing produced water and
solid wastes is critical to prevent both occupational and public
human health risks as well as environmental contamination.
Wildlife impacts
There are a number of stressors from hydraulic fracturing
operations that may affect wildlife health. For example, a US
Government Accountability Ofﬁce study found that of the 575
National Wildlife Refuges in the United States 105 contain a
total of 4406 oil and gas wells. Though rigorous scientiﬁc
studies are lacking, the information available reveals that
construction-related activities that result in habitat fragmentation, as well as spills, have had detrimental effects on wildlife
and habitats.
Besides the aforementioned stressors, exposure of wildlife to
light and noise is an additional concern; and impacts on
wildlife will likely vary among types of wildlife and species
Environmental Toxicology and Chemistry, Vol. 33, No. 8, August, 2014
FIGURE 4: Results of exploratory analysis of a 16-watershed case study in the Fayetteville Shale relating field data to an array of land-use variables.
Land-use variables highly correlated with one another (Spearman rho 0.7) were limited to 1 representative variable to enhance interpretation of
results. Panels (A) and (B) are random forest analysis results (10 runs with different starting seeds) showing relative variable importance of land-use
variables in the prediction of (A) conductivity (positively correlated with metals, total suspended solids, and chloride concentrations) and (B) %
Plecoptera. the (þ) and (–) signs indicate the direction of Spearman’s correlation (p < 0.05). The map (C) shows results of an overlay analysis using the land-use variables of highest importance in the random forest analysis to predict potential “impact” to % Plecoptera (decrease below 75th centile), with field observation values plotted on the map (points). IFL ¼ inverse flowpath length. (e.g., game species, migratory birds, amphibians). The main sources of noise during the production phase would include compressor and pumping stations, producing wells (including occasional ﬂaring), and vehicle trafﬁc. Compressor stations produce high noise levels. The primary impacts from noise would be localized disturbance to wildlife, livestock, recreationists, and residents. Flooding an ecosystem with excessive light can disrupt feeding, breeding, and rest patterns in micro- and mega-ﬂora and -fauna, providing a potential for ecosystem degradation. Unfortunately, quantifying these effects and their causality linkages is difﬁcult. What Can Be Done to Mitigate and Monitor Environmental Impacts? Given the potential for ecological impacts from the stressors mentioned in the Why the Concern? section, it is imperative that proactive assessment methods be incorporated into the regulatory process. Examples are given below of proven methods. Geographic information systems A useful way to assess the potential impacts of hydraulic fracturing operations is through geographic information system–based models that incorporate ecological, political, and fracturing features [4]. In the Marcellus Shale region, the USEPA undertook a biological assessment of the Allegheny and Monongahela Rivers. To design the study, the USEPA evaluated conditions via probabilistic survey for ﬁsh, ﬁsh habitat, macroinvertebrates (such as mussels), water chemistry, plankton, and sediment. The resultant data assisted in risk assessment from potential stressors and aided in analyzing the potential seasonal and yearly variability (see sidebar Assessment of High-Volume Hydraulic Fracturing Impacts on Streams: A Case Study Example). Environmental Toxicology and Chemistry, Vol. 33, No. 8, August, 2014 1685 Databases Another tool used by the USEPA in its 2008 Marcellus study was the River Alert Information Network (RAIN). This network integrates information from water treatment, source water protection, and distribution system maintenance into a multiple barrier approach. The goal of RAIN is to employ protection measures to form a ﬁrst barrier to a multiple-barrier approach to drinking water protection. This includes providing information and tools to aid water suppliers in making decisions and improving communication between water suppliers about water-quality events. The network implements these goals by installing monitoring equipment at appropriate locations and providing operational training. The USEPA RAIN administrators will develop a secure website to share information about water quality and to improve communication between water suppliers, the US Army Corps of Engineers, and emergency responders. As a tandem effort to RAIN, the USEPA initiated a waste characterization study to measure total dissolved solids, metals, organics, and naturally occurring radioactive materials. The study is dual-phased, with phase 1 focusing on site-speciﬁc characteristics across the region. In Pennsylvania, the rapid pace of Marcellus Shale drilling has outstripped Pennsylvania’s ability to document predrilling water quality, even with some 580 organizations focused on monitoring the state’s watersheds. More than 300 organizations are community-based groups that take part in volunteer stream monitoring. Water quality– monitoring efforts, such as that of the Shale Network (www. shalenetwork.org), are working to overcome this monitoring challenge by leveraging the activity of citizen scientists and providing a public database for collection and dissemination of water-quality data across the Appalachian basin. State-level activities As an example, in Michigan, the state permitting process dictates that all hydraulic fracturing operations reduce their potential impact onsite through a variety of measures. These include construction of the well pad at least 1320 feet from the nearest stream for state leases. For private properties, the Department of Environmental Quality requires optimal location that protects surface water while considering a host of other property and environmental issues. The state’s considerations also include land elevations, avoiding hillsides, and always using silt curtains. All pervious site grounds are covered in plastic to capture any potential spillage. Permitted sites are for a drilling unit (a tract which the Department of Environmental Quality has determined can be efﬁciently drained by 1 well) and typically a minimum of 80 acres in size but often much larger, whereas the working pad area is usually less than 5 acres. Lined berms are put in place to contain tank or pipe spills. The Department of Environmental Quality (and the Department of Natural Resources when state acreage is involved) also evaluates where roads may be constructed. The service companies are required to have spill pollution prevention plans, but these may not be available to the actual rig operators. Rig operators must have a 1686 spill pollution prevention plan. After site operations cease, the owners are required to reclaim the site using native species of vegetation. The state of Michigan utilizes the novel and useful Water Withdrawal Assessment Tool (http://www.miwwat.org/) to estimate the likely adverse resource impact of a water withdrawal on nearby streams and rivers [20]. Use of the Water Withdrawal Assessment Tool is required of anyone proposing to make a new or increased large-quantity withdrawal (more than 280 L/min) from the waters of the state, including all groundwater and surface water sources, prior to beginning the withdrawal. This system allows for an evaluation of potential impacts to many sensitive ecosystems. It has several limitations, however, including that it does not currently account for shallow stream morphology and that water withdrawal impacts to wetlands and lakes are based on fewer than 150 US Geological Survey stream gauges, which tend to be located on medium-sized and large-sized streams [20]. It is also a concern that the massive quantities being removed from the aquifer are not being replaced but rather deep-well– injected. Given that fracturing operations can be dense and adjacent to one another, this creates the possibility for negative cumulative impacts from high-volume water withdrawals. Indeed, recent operations will be in the tens of millions of liters extracted for each operation. The Water Withdrawal Assessment Tool should be updated to address concerns of cumulative withdrawals from sensitive shallow headwater streams and could serve as a useful model for other regions to adopt. Challenges and Opportunities Of all the scientiﬁc disciplines within the hydraulic fracturing arena, ecotoxicology will feature prominently for 2 main reasons, one philosophical and the other practical. Philosophically, ecotoxicologists are trained to think across scales of time, space, and disciplines. They are trained to coalesce diverse concepts and perspectives into a coherent consonant. Such thinking is highly pertinent to the hydraulic fracturing debate that is greatly polarized and often driven by incomplete information, miscommunication, or misunderstandings on various sides of the issue. Practically, the nature of the hydraulic fracturing industry means that ecotoxicological impacts will manifest in a variety of manners. From the injection of chemicals into subsurface environments to the development of new roads and infrastructure, the resulting activities may have profound effects, from the cellular level all the way to the level of landscapes and ecosystems, in current and future time. Below, we outline some of the challenges associated with understanding plausible hazards or risks associated with HVFV on streams and opportunities for improving the process (see sidebar Moving Forward: Options for Improving the Assessment of Hydraulic Fracturing on Surface Waters). One of the greatest challenges in quantifying the ecological effects of hydraulic fracturing is the enormous potential for variation within and among different ecosystems and the Environmental Toxicology and Chemistry, Vol. 33, No. 8, August, 2014 aquatic communities far downstream, particularly if impacts of downstream wells are additive or synergistic. In addition, other potential stream stressors and their sources present in the watershed must be considered, such as from agricultural and urban land uses, or simply additional HVFV operations. As discussed above, many of the potential stressors resulting from HVHF operations are the same as those associated with other anthropogenic activities, which may also be occurring within the same watershed. In addition, these considerations must be evaluated within the proper ecological context [21]. Impacts to surface water in a pristine watershed will be assessed very differently from those in an arid area with ephemeral streams or in large riverine systems dominated by human disturbances. This suggests that a strategic “anthropogenic and ecological context–based” approach should be used to determine the likelihood for adverse ecological effects to occur [21]. Moving Forward: Options for Improving the Assessment of Hydraulic Fracturing on Surface Waters Develop a decision matrix that guides decision making on establishing hydraulic fracturing operations in sensitive or susceptible ecosystems. Establish baseline (reference condition) ecosystem monitoring in susceptible areas that continues through postoperation periods to determine whether detrimental impacts occur in an ecological context–based approach. Assess the cumulative impacts of multiple hydraulic fracturing operations within a watershed for downstream surface waters and groundwater. Establish to what degree other likely stressors in watershed, unrelated to fracturing operations, impact aquatic communities. Identify areas for improved quality control and best practices in fracturing operations, especially near riparian zones, surface waters, and shallow aquifers. Establish a publically available database for high-volume hydraulic fracturing studies and data. It is important that close attention be paid to the findings published in the peer-reviewed scientific literature in the coming months to years to improve decision making. Any assessment of ecological impact from high volume hydraulic fracturing should in turn evaluate how potential impacts compare to the environmental impacts of other anthropogenic activities in the relevant watershed(s). differing hydraulic fracturing operation sizes, pad densities, and quality-control measures. Additionally, as multiple well sites are established within watersheds, there is potential for the ecological effects of these fracturing operations to interact. Upstream wells, for example, could impact water ﬂows, turbidity, or nutrient and total dissolved solid loadings of Another challenge lies in the examination of the effects of fracturing operations before, during, and after the actual hydraulic fracturing occurs. Typically, wells will be actively fractured during a period of only 1 wk to 2 wk. However, the ecological effects associated with the hydraulic fracturing activity begin as soon as infrastructure construction is initiated and last for an unestablished period of time after fracturing is completed. Related to this is the inability to assess whether an actual ecological impact has occurred. This is a particular challenge because of a lack of baseline data and continued monitoring efforts. Very few sites exist in the United States for which baseline (reference condition) environmental monitoring has occurred prior to hydraulic fracturing operations commencing. From both scientiﬁc and practical perspectives, it is difﬁcult to establish “impacts” if the baseline is unknown, particularly if these operations are occurring in humandominated watersheds. It is essential that at least a subset of hydraulic fracturing operations have pre- and postmonitoring of environmental conditions to establish whether detrimental impacts are occurring. A number of potential hazards clearly exist in hydraulic fracturing operations, but the presence of a hazard does not necessarily indicate a high level of risk. As such, it next needs to be determined whether organisms and ecosystems are exposed and affected. Although hazards have been identiﬁed, few exposure assessments have been conducted in hydraulic fracturing sites, and even fewer have tried to account for their possible cumulative health impacts. Nevertheless, a wealth of relevant ecotoxicological studies exist in relation to predicting and understanding the impacts of land development and resource extraction, which directly relate to HVHF potential impacts. Chemicals intentionally used in hydraulic fracturing serve a number of functions, but few of them have undergone rigorous toxicological or ecotoxicological testing. Although chemical spills are less frequent than chronic habitat disturbance and erosion, it is important to begin to understand the toxicity of the wide range of hydraulic fracturing chemicals and combinations of these chemicals that may be released in produced waters, in addition to any pure chemical products Environmental Toxicology and Chemistry, Vol. 33, No. 8, August, 2014 1687 stored onsite. The most prominent chemicals are proven human health hazards and, thus, are likely to be of concern to ecological health as well. In addition, an outstanding feature in the toxicological sciences, which is of clear relevance to hydraulic fracturing, is the lack of understanding concerning toxicant–toxicant interactions (mixture effects), how these toxicants may change with varying temperatures and other conditions, and how toxicants may interact with nonchemical stressors (e.g., habitat loss, food availability) to inﬂuence health. Many of these challenges will require toxicological evidence that spans multiple organisms and ecosystems. Full assessment of the complex task of determining whether ecological systems are at risk from hydraulic fracturing operations requires a comprehensive, watershed-based research and management approach. To date, inadequate information exists to determine ecological risk to surface waters, but we can determine the plausibility that hazards may occur. An appropriate analogy, and future model, that may be useful is the Total Maximum Daily Loading (TMDL) program, used widely by the USEPA and states, the TMDL offers a watershed-based framework for this task and accounts for the cumulative contributions of multiple sources to receiving waters. Although oil and gas operations are not granted surface water discharges, the idea of considering environmental and groundwater “loadings or use” on a watershed-by-watershed basis is appropriate. The TMDL is a useful tool in establishing particular watersheds, water bodies, or water basins that may be impaired. The TMDL was developed under section 303(d) of the Clean Water Act that requires states or territories to develop lists of waters that are “impaired” or otherwise too degraded to meet water-quality standards. The TMDL actually calculates a maximum amount of pollutant that a body of water can maintain, while still adhering to the approved water-quality standards. The TMDL tool provides curves that aid in calculation of the duration that a particular pollutant or chemical of concern can last in a certain water body. Thus, an industrial operator or monitoring agency could use this approach to evaluate how to assess the potential terrestrial and surface water impacts of multiple HVHF operations within a watershed. Water withdrawal modeling tools, such as Michigan’s Water Withdrawal Assessment Tool, must consider cumulative withdrawal impacts from operations drawing on the same aquifer, at extremely high volumes, during biologically sensitive seasonal periods. Given that this tool will not assess the potential impacts of HVHF operations on habitat, wildlife, and nearby waters receiving site runoff, routine site inspections will be required to ensure that site erosion is minimal and spill prevention plans are being followed. Geographic information system–based modeling and site monitoring will allow for these potential impacts to be evaluated, thereby ensuring that proper siting and operational controls are established and followed. There is no completely risk-free energy development scheme, and all activities (renewable and nonrenewable) pose some degree of risk to the environment. Therefore, any assessment of hydraulic fracturing needs to be conducted with careful 1688 consideration of other anthropogenic activities, including energy sources, relative trade-offs, and associated risks and beneﬁts to environmental health. It must also be realized that risks and beneﬁts can vary from the local to regional/state, national, and international levels. Any assessment of ecological health impacts from this energy-driven activity should in turn evaluate how these potential impacts compare to the environmental impacts of other energy-related activities, as well as in the context of other non–energy-related stressors. This comparison must consider both regional and international impacts resulting from energy markets and cross-boundary pollutant transport. Acknowledgment This work was partially supported by the Graham Sustainability Institute, University of Michigan. We gratefully acknowledge the data support from M. Evans-White and B. Haggard (University of Arkansas) and from G. Adams and R. Adams (University of Central Arkansas), as well as project funding for their data by the Arkansas Game & Fish Commission. B. Ellis recognizes funding support from the National Science Foundation (grant no. 1214416) and from the Michigan Society of Fellows. REFERENCES [1] Lubowski RN, Vesterby M, Bucholtz S, Baez A, Roberts M. 2006. Major uses of land in the United States, 2002. US Department of Agriculture, Washington (DC): US Department of Agriculture. [cited 2014 March 27]. Avalailable from: http://www.ers.usda.gov/publications/eib-economic-information-bulletin/eib14.aspx#.U2O_rq1dVbt. [2] Howarth RW, Santoro R, Ingraffea A. 2011. Methane and the greenhouse-gas footprint of natural gas from shale formations. Clim Change 106:679–690. [3] US Government Accountability Ofﬁce. 2012. Oil and gas: Information on shale resources, development, and environmental and public health risks. Report to congressional requesters. Washington, DC. [4] Entrekin S, Evans-White M, Johnson B, Hagenbuch E. 2011. Rapid expansion of natural gas development poses a threat to surface waters. Frontiers in Ecology 9:503–511. [5] Williams HFL, Havens DL, Banks KE, Wachal DJ. 2008. Field-based monitoring of sediment runoff from natural gas well sites in Denton County, Texas, USA. Environ Geol (Berl) 55:1463–1471. [6] Drohan PJ, Brittingham M, Bishop J, Yodeer K. 2012. Early trends in landcover change and forest fragmentation due to shale-gas development in Pennsylvania: A potential outcome for the northcentral Appalachians. Environ Manag 49:1061–1075. [7] Rozel DA, Reaven SJ. 2012. Water pollution risk associated with natural gas extraction from the Marcellus Shale. Risk Analysis 32:1382–1393. [8] Vidic RD, Brantley SL, Vandenbossche JM, Yoxtheimer D, Abad JD. 2013. Impact of shale gas development on regional water quality. Science 340: 1235009. [9] US Environmental Protection Agency. 2014. Watershed assessment, tracking & environmental results: Causes of impairments. [Cited 2014 March 27]. Available from: http://iaspub.epa.gov/waters10/attains_nation_cy.control# causes. [10] Ewen C, Borchardt D, Richter S, Hammerbacker R. 2012. Hydraulic fracturing risk assessment: Study concerning the safety and environmental compatibility of hydraulic fracturing for natural gas production from unconventional reservoirs. ExxonMobil Production, Darmstadt, Germany. [11] Burton GA, Johnston EL. 2010. Assessing contaminated sediments in the context of multiple stressors. Environ Toxicol Chem 29:2625–2643. [12] US Environmental Protection Agency. 2012. Study of the potential impacts of hydraulic fracturing on drinking water resources. Progress report. EPA 601/ R-12/011. Washington, DC. [13] Ground Water Protection Council, Interstate Oil and Gas Compact Commission. 2013. FracFocus. [cited 2013 May 3]. Available from: fracfocus.org. [14] Rahm BG, Bates JT, Bertoia LR, Galford AE, Yoxtheimer DA, Riha SJ. 2013. Wastewater management and Marcellus Shale gas development: Trends, drivers, and planning implications. J Environ Manag 102:105–113. [15] Wilson JM, VanBriesen JM. 2012. Oil and gas produced water management and surface drinking water sources in Pennsylvania. Environmental Practice 14:288–300. [16] Warner NR, Christie CA, Jackson RB, Vengosh A. 2013. Impacts of shale gas wastewater disposal on water quality in western Pennsylvania. Environ Sci Technol 47:11849–11857. Environmental Toxicology and Chemistry, Vol. 33, No. 8, August, 2014 [17] NORM Technology Connection [Internet]. Interstate Oil and Gas Compact Commission [Cited 2013 May 3]. Available from: http://norm.iogcc.state.ok. us/index.cfm. [22] US Energy Information Administration. 2013. Technically recoverable shale oil and shale gas resources: An assessment of 137 shale formations in 41 countries outside the United States. Final Report. Washington, DC. [18] US Geological Survey. 1999. Naturally occurring radioactive materials (NORM) in produced water and oil-ﬁeld equipment—An issue for the energy industry. FS-142-99. Washington, DC. [23] Ground Water Protection Council and ALL Consulting. 2009. Modern shale gas development in the United States: A primer. US Department of Energy, Washington, DC. [19] Haluszczak LO, Rose AW, Kump LR. 2013. Geochemical evaluation of ﬂowback brine from Marcellus gas wells in Pennsylvania, USA. Appl Geochem 28:55–61. [24] Colborn T, Kwiatkowski C, Schultz K, Bachran M. 2011. Natural gas operations from a public health perspective. Human and Ecological Risk Assessment 17:1039–1056. [20] Hamilton DA, Seelbach PW. 2011. Michigan’s water withdrawal assessment process and Internet screening tool. Fisheries Division Special Report 55. Michigan Department of Natural Resources, Lansing, MI, USA. [25] Gosman S, Robinson S, Shutts S, Friedmann 2012. Hydraulic fracturing in the Great Lakes basin: The state of play in Michigan and Ohio. A legal analysis by the National Wildlife Federation. Ann Arbor, MI, USA. [21] Clements WH, Hickey CW, Kidd KA. 2012. How do aquatic communities respond to contaminants? It depends on the ecological context. Environ Toxicol Chem 31:1932–1940. [26] Encana Corporation. 2013. Chemical use. [cited 2013 March 2]. Available from: http://www.encana.com/environment/water/fracturing/chemical-use. html. Environmental Toxicology and Chemistry, Vol. 33, No. 8, August, 2014 1689 EG39CH12-Jackson ARI 7 October 2014 11:47 The Environmental Costs and Beneﬁts of Fracking ANNUAL REVIEWS Further Annu. Rev. Environ. Resourc. 2014.39:327-362. Downloaded from www.annualreviews.org by 99.108.142.3 on 10/18/14. For personal use only. Click here for quick links to Annual Reviews content online, including: • Other articles in this volume • Top cited articles • Top downloaded articles • Our comprehensive search Robert B. Jackson,1,2 Avner Vengosh,2 J. William Carey,3 Richard J. Davies,4 Thomas H. Darrah,5 Francis O’Sullivan,6 and Gabrielle Pétron7 1 School of Earth Sciences, Woods Institute for the Environment, and Precourt Institute for Energy, Stanford University, Stanford, California 94305; email: rob.jackson@stanford.edu 2 Division of Earth and Ocean Sciences, Nicholas School of the Environment, Duke University, Durham, North Carolina 27708; email: jackson@duke.edu, vengosh@duke.edu 3 Earth & Environmental Sciences, Los Alamos National Laboratory, Los Alamos, New Mexico 87545; email: bcarey@lanl.gov 4 School of Civil Engineering and Geosciences, Cassie Building, Newcastle University, Newcastle upon Tyne, NE1 7RU, UK 5 School of Earth Sciences, Ohio State University, Columbus, Ohio 43210; email: darrah.24@osu.edu 6 MIT Energy Initiative, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139; email: frankie@mit.edu 7 National Oceanic and Atmospheric Administration and University of Colorado, Boulder, Colorado 80305; email: gabrielle.petron@noaa.gov Annu. Rev. Environ. Resour. 2014. 39:327–62 Keywords First published online as a Review in Advance on August 11, 2014 horizontal drilling, hydraulic fracturing, induced seismicity, shale gas, water resources, air quality, well integrity The Annual Review of Environment and Resources is online at environ.annualreviews.org This article’s doi: 10.1146/annurev-environ-031113-144051 c 2014 by Annual Reviews. Copyright All rights reserved Abstract Unconventional oil and natural gas extraction enabled by horizontal drilling and hydraulic fracturing (fracking) is driving an economic boom, with consequences described from “revolutionary” to “disastrous.” Reality lies somewhere in between. Unconventional energy generates income and, done well, can reduce air pollution and even water use compared with other fossil fuels. Alternatively, it could slow the adoption of renewables and, done poorly, release toxic chemicals into water and air. Primary threats to water resources include surface spills, wastewater disposal, and drinking-water contamination through poor well integrity. An increase in volatile organic compounds and air toxics locally are potential health threats, but the switch from coal to natural gas for electricity generation will reduce sulfur, nitrogen, mercury, and particulate air pollution. Data gaps are particularly evident for human health studies, for the question of whether natural gas will displace coal compared with renewables, and for decadal-scale legacy issues of well leakage and plugging and abandonment practices. Critical topics for future research 327 EG39CH12-Jackson ARI 7 October 2014 11:47 include data for (a) estimated ultimate recovery (EUR) of unconventional hydrocarbons, (b) the potential for further reductions of water requirements and chemical toxicity, (c) whether unconventional resource development alters the frequency of well integrity failures, (d ) potential contamination of surface and ground waters from drilling and spills, (e) factors that could cause wastewater injection to generate large earthquakes, and ( f ) the consequences of greenhouse gases and air pollution on ecosystems and human health. Contents Annu. Rev. Environ. Resourc. 2014.39:327-362. Downloaded from www.annualreviews.org by 99.108.142.3 on 10/18/14. For personal use only. 1. INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2. RESOURCE PRODUCTIVITY AND UNCONVENTIONAL OIL AND GAS DEVELOPMENT. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.1. The Early-Life Productivity of the Unconventional Oil and Gas Resource . . . . . 2.2. The Challenge of Estimating Ultimate Recovery from the Unconventional Oil and Gas Resource . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.3. Emerging Research Questions Regarding Productivity and Ultimate Recovery 3. WATER REQUIREMENTS FOR UNCONVENTIONAL ENERGY EXTRACTION AND ELECTRICITY GENERATION . . . . . . . . . . . . . . . . . . . . . . . 3.1. Water Requirements for the Extraction of Unconventional Natural Gas and Oil . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.2. Water Intensities for Unconventional Fuels and Other Energy Sources. . . . . . . . 3.3. Emerging Research Questions for Water Use and Intensity . . . . . . . . . . . . . . . . . . . 4. WELL INTEGRITY AND FRACTURING-INDUCED STRESS . . . . . . . . . . . . . . 4.1. The Importance of Well Integrity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.2. Field Observations of Wellbore-Integrity Failure . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.3. Mechanisms of Wellbore-Integrity Failure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.4. Research Questions and Recommendations for Well Integrity . . . . . . . . . . . . . . . . 5. RISKS TO SURFACE-WATER AND GROUDWATER RESOURCES . . . . . . . . . 5.1. The Potential for Drinking-Water Contamination . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.2. Isolating Wastewaters from Surface Water and Groundwater . . . . . . . . . . . . . . . . . 5.3. Research Questions and Recommendations for Potential Water Contamination . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6. INDUCED SEISMICITY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.1. Seismic Concerns: Hydraulic Fracturing Versus Wastewater Injection . . . . . . . . 6.2. Future Research to Reduce Risks Associated with Induced Seismicity . . . . . . . . . . 7. THE AIR IMPACTS OF UNCONVENTIONAL RESOURCES . . . . . . . . . . . . . . . . 7.1. The Stages of Extraction and Processing for Unconventional Energy Extraction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.2. The Composition of Emissions and Their Potential Impacts . . . . . . . . . . . . . . . . . . 7.3. How Large Are VOC and Greenhouse Gas Emissions and What Are Their Main Drivers? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.4. Unconventional Energy Use Can Improve or Impair Air Quality . . . . . . . . . . . . . . 7.5. How Effective Are Mitigation Practices? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.6. Research Needs for Air Quality Impacts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8. CONCLUSIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 328 Jackson et al. 329 331 331 332 334 334 334 335 337 337 337 338 339 340 341 341 342 344 344 344 346 346 346 347 348 351 351 353 353 EG39CH12-Jackson ARI 7 October 2014 11:47 Annu. Rev. Environ. Resourc. 2014.39:327-362. Downloaded from www.annualreviews.org by 99.108.142.3 on 10/18/14. For personal use only. 1. INTRODUCTION The past decade has seen tremendous change in the energy sector. Increased production of oil and natural gas in the United States has been driven largely by the extraction of unconventional resources of natural gas, oil, and other hydrocarbons locked inside tight sandstones, shales, and other low-permeability geological formations. These rocks were long known to contain hydrocarbons and to have served as source rocks for many conventional oil and gas ﬁelds. Because of their low porosity and permeability, however, the gas and oil in them were generally viewed as unrecoverable, at least at prices comparable to those of recent decades. Recent advancements in hydraulic fracturing and horizontal drilling have changed that view (1, 2). Drilling is now done kilometers underground and to horizontal distances of 2 km or more, tracking shale, sandstone, and other formations as narrow as 30 m thick. After horizontal drilling, the well is hydraulically fractured. From ∼8,000 to 80,000 m3 (2–20 million gallons) of water, proppants such as sand, and chemicals are pumped underground at pressures sufﬁcient to crack impermeable rock formations (10,000–20,000 psi). The fractures induced by high-pressure, highvolume hydraulic fracturing provide the conductivity necessary to allow natural gas and oil to ﬂow from the formation to the well and then up through the well to the surface. The impacts that unconventional oil and natural gas have had on estimates of recoverable resources and production have been profound. Numerous countries, including Algeria, Argentina, Australia, Brazil, Canada, China, France, Libya, Mexico, Poland, Russia, South Africa, the United States, and Venezuela, are estimated to possess at least ∼3 × 1012 m3 [∼100 trillion ft3 (Tcf ), or 1 × 1014 ft3 ] of recoverable shale gas (1, 3, 4). Global estimates for recoverable shale gas are ∼206 × 1012 m3 , at least 60 years of current global usage in 2013, and global estimated shale-oil resources are now 345 billion barrels (Bbbl; one barrel = 42 US gallons) (5). In the United States, mean estimates for the technically recoverable shale-gas resource doubled to 600–1000 Tcf (17–28 × 1012 m3 ) in 2013, and the technically recoverable shale-oil resource rose by 40%, or 58 Bbbl (5, 6). These substantial resource estimates remain best guesses because large-scale production of shale and other unconventional resources is still in its infancy. (See Figure 1.) Not only have recoverable resource estimates increased, but so has production of oil and natural gas. In Canada, the production of light oil from shales, sandstones, and other impermeable formations rose from ∼0 to >160,000 barrels per day in Saskatchewan, Alberta, and
Manitoba alone (7). Daily production of natural gas from US shale formations increased from
25 Bcf ) per day in
2012, accounting for 39% of domestic natural gas production that year.
One likely consequence of low-cost natural gas will be many more gas-centric economies
around the world. Natural gas use in power generation is expected to grow by 60% in the United
States over the next quarter century, largely at the expense of coal (8), although coal production
is still projected to increase globally during that time (8). Chemical and other energy-intensive
manufacturing is expected to increase by 20% over the next decade because of lower-priced natural
gas and natural gas liquids (feedstocks such as propane and butane) (9). Approvals for new liquid
natural gas export terminals have already been granted for 190 million m3 /day (6.6 Bcf/day), ∼10%
of 2013 US daily production.
The impacts of increased shale-oil and natural gas production on global energy economies
are extensive. At current prices of ∼US$100/barrel, for instance, the 345 Bbbl increase in global
shale-oil reserves is worth ∼US$35 trillion. Given the economic value of the oil and gas resources
made available by hydraulic fracturing and related technologies around the world, society is
virtually certain to extract more of these unconventional resources. The key issue, then, is how
to produce them in a way that reduces environmental impacts to the greatest extent possible.
www.annualreviews.org • Environmental Costs and Benefits of Fracking
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Assessed basins with resource estimate
Assessed basins without resource estimate
Figure 1
Basins with assessed shale-gas and shale-oil resources as of June 2013 (5). The ﬁgure does not show additional tight sand formations.
Public concerns about the environmental impacts of hydraulic fracturing have accompanied
the rapid growth in energy production. These concerns include the potential for groundwater and
surface-water pollution, local air quality degradation, fugitive greenhouse gas (GHG) emissions,
induced seismicity, ecosystem fragmentation, and various community impacts. Many of these issues are not unique to unconventional oil and gas production. However, the scale of hydraulic
fracturing operations is much larger than for conventional exploration onshore. Moreover, extensive industrial development and high-density drilling are occurring in areas with little or no
previous oil and gas production, often literally in people’s backyards.
The goal of this review is to examine the environmental consequences of unconventional
energy extraction and hydraulic fracturing. We begin by describing production estimates and
decline curves for unconventional natural gas and oil wells, two important criteria for comparing environmental footprints on a unit-energy basis. We also examine water requirements and
water intensity, comparing them to values for other fuels. We next examine issues of well integrity and the potential leakage of chemicals, brines, or gases. We include results from oil and gas
and carbon-capture-and-storage operations, as well as legacy issues associated with drilling millions of new wells globally. We then focus on water quality issues accompanying unconventional
energy extraction, including potential drinking-water contamination and wastewater disposal. We
examine the potential for induced seismicity associated with hydraulic fracturing and, more importantly, wastewater disposal. We conclude by comparing the emissions of hydrocarbons during
fossil-fuel extraction, distribution, and use, including new measurements of GHG emissions, interactions with ozone pollution, and discrepancies between bottom-up and top-down estimates of
hydrocarbon emissions.
330
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Throughout the paper, we provide research recommendations for each topic covered in the
review. We also cover some environmental beneﬁts and positive trends associated with unconventional energy extraction, including the potential for saving cooling water in thermoelectric power
generation, increased water reuse and recycling, and the reduced air pollution and improved health
beneﬁts that can come from replacing coal with natural gas. We do not have the space to cover
numerous important issues, most notably the critical social and community impacts associated
with the unconventional energy boom.
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2. RESOURCE PRODUCTIVITY AND UNCONVENTIONAL OIL
AND GAS DEVELOPMENT
2.1. The Early-Life Productivity of the Unconventional Oil and Gas Resource
Resource productivity is the key to characterizing how much oil and natural gas will be extracted
from an area and for estimating environmental metrics such as the freshwater and GHG intensities of extraction (10–12). When assessing resource productivity, the productive unit differs for
unconventional and conventional plays.1 In conventional ﬁelds, the oil and natural gas typically
reside in high-porosity and high-permeability structural or stratigraphic traps, such as anticlines
or salt domes. Well productivity is often inﬂuenced by the number and proximity of surrounding
wells. Productivity is therefore usually estimated at the ﬁeld level. In contrast, the individual well is
typically the estimated unit of production for unconventional resources (13). The low permeability
of unconventional ﬁelds means that the productivity of a well is rarely inﬂuenced by surrounding
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