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Opportunity for Stakeholder Input on
Criteria for Selecting Case Studies for Consideration in
EPA's Hydraulic Fracturing Research Study
Hydraulic fracturing (HF) is a process used to increase the volume of natural gas that can be recovered from
sources such as coalbeds, tight sands, and shale formations. HF is also used for other applications including oil
recovery. During HF, fracturing fluids are injected into wells under high pressure to generate fractures in geologic
formations. Fracturing fluids consist primarily of water and additives that serve a variety of purposes ~ increasing
fluid viscosity, inhibiting corrosion, and limiting bacterial growth to name a few. In addition, proppants, often
sand, are added to keep the fractures open after the pressure is released. The sources of water used during HF
activities include surface water and ground water. Over the past few years, several key technical, economic, and
energy policy developments have spurred the use of HF for gas extraction over a wide diversity of geographic
regions and geologic formations. Along with the expansion of HF, there have been increasing concerns about its
potential impacts on drinking water resources, public health, and the environment in the vicinity of these activities.
EPA is developing a research study to examine the potential relationships between HF and drinking water. A key
goal of the EPA study is to generate data and information that can be used to assess risks and ultimately to inform
decisions. EPA has proposed four key approaches to obtain data and information to address research questions:
• Compile and analyze background data and information
• Characterize of chemical constituents relevant to hydraulic fracturing
Conduct case studies and computational modeling
Identify and evaluate technological solutions for risk mitigation and decision support
The purpose of this document is to background information on the role of case studies in EPA's HF study and to
introduce a proposed process to identify, nominate, and select case studies. A critical step is to develop an objective
method for selecting and prioritizing sites. EPA is seeking stakeholder input on the proposed criteria for selecting
case study locations and appropriate research questions to be answered using case studies.
Stakeholder Input
In an effort to enlist stakeholder advice for its the study design, EPA requests input on the proposed criteria that
may be used to determine case study locations. EPA asks that stakeholders consider the following questions while
reading the remainder of this document:
• Are the proposed selection and prioritization criteria appropriate?
• Would you suggest revised or additional criteria to better identify, screen, and prioritize sites for field
investigations and case studies?
• Are there other research questions that a case study approach would be uniquely able to address?
• Are you aware of potential candidate sites or case studies that would be useful for this study? If so, what
are the characteristics that would make the candidates appropriate for this study on the relationship between
HF and drinking water resources? Please provide additional supporting information.
Stakeholders may submit comment to EPA on the proposed case study criteria by providing a verbal or written
comment during the public information meetings held during July through August 2010; emailing comments to
hydraulic . fracturing@epa. gov: or mailing written comments to Jill Dean, 1200 Pennsylvania Ave. NW, Mail code
4606M, Washington, DC 20460.
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Role of Case Studies in the HF Research Study
Case studies are widely used to conduct in-depth investigations of complex topics and, therefore, can provide a
systematic framework to investigate the interplay of the various factors that are relevant to HF. The scope of case
studies can range from local or regional data collection and analysis at existing sites to extensive investigations on
new or planned HF sites in collaboration with industry or other partners. Developing a national perspective on HF
is complex due to geographical variations in water resources, geologic formations, and hydrology. In addition, the
stressors on water resources vary over the lifecycle of hydraulic fracturing. Ideally, the types of data and
information that are collected through case studies should provide enough detail to determine the extent to which
conclusions can be generalized at local, regional, and national scales. Case studies, together with other elements of
the research program, can be used to help determine:
• if drinking water resources are impacted by HF,
• the extent and possible causes of any impacts, and
• what can be done to avoid or mitigate impacts.
Conducting case studies can provide a forum for stakeholders to interact and exchange information and data. Case
studies may also provide data and model inputs on the fate and transport of fluids and contaminants that may vary
in different regions and geologic settings. In addition, case studies may inform the development of best
management practices for environmental protection.
The starting point for developing case studies is to define specific research questions that can be addressed by case
studies. An initial set of research questions proposed by EPA includes:
1. What sampling strategies and analytical methods are available and appropriate to identify potential impacts
on sources of drinking water, water supply wells, and receiving streams?
2. Are there vulnerable hydrogeologic settings where HF may impact the quality and availability of water
supplies?
3. How does the proximity of HF to abandoned and/or poorly constructed wells, faults, and fractures affect
impacts on drinking water resources and human health?
4. Is there evidence that pressurized methane or other gases, HF fluids, radionuclides, or other HF-associated
contaminants can migrate into underground sources of drinking water (USDW)? Under what conditions do
these processes occur?
Context for Case Studies
The success of case studies depends on clear definition of specific goals coupled with robust criteria for the
nomination and selection of cases. A summary of field-based activities relevant to key components of the HF
lifecycle is shown in Table 1 along with potential site selection criteria. It is anticipated that the each case study will
have multiple components and the nominated sites are likely to fall into three categories:
• Sites where HF is being planned
• Sites where HF is in progress
• Sites where HF has already been completed
Because of the resource and time constraints associated with EPA's study, it is only feasible to conduct a limited
number of case studies. Therefore, criteria to identify, and select case studies are important, given the inherent
complexities associated with the diverse regional, geological, and community settings under which HF takes place.
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Data and Information Sought to Inform Design of Field Investigations and Case Studies
For candidate sites, efforts will be made to compile and review available data and identify gaps that need to be
addressed during initial site investigations. In addition, EPA may map and classify candidate sites based on
variations in geologic settings and infrastructure components to further prioritize the field investigations. Examples
of useful data include:
• Depths of all existing well(s)
• Well completion details (production and nearby wells)
• Well logs (production well, other nearby wells)
• Cumulative production data
• Cumulative injection data, including for stimulation
• Data on surface infrastructure, such as pits, evaporation ponds, lagoons, etc.
• Local geologic information including shallow ground water information
• Ground water monitoring data
• Cement bond log
• Geologic descriptions, cross sections
• Monitoring data (types of samples collected, parameters monitored, etc.)
Proposed Criteria to Prioritize Sites for Case Studies
EPA seeks advice from stakeholders regarding potential case studies. Stakeholders are invited to provide
suggestions and refinements to the prioritization of criteria and information listed in Table 1. Once candidates for
case studies are evaluated, EPA will select from among the candidates based on the extent to which the selected
case studies are expected to significantly contribute answers to the high priority research questions, geographic and
geologic diversity, potential availability of data and access, potential for effective collaboration, and resources
required.
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Table 1: Overview of field based hydraulic fracturing activities, criteria and information needed for selecting case
studies.
Hydraulic Field activities to Potential criteria for selecting sites Information needed
fracturing determine potential for case studies
stage impacts on water resources
Siting of
production
wells,
construction,
and well
development
and completion
Monitor production well
integrity and surface and
ground water supplies
before, during, and after
construction
HF of targeted
geologic
formation
Monitor on-site, up-gradient,
and down-gradient before,
during, and after HF
Proximity of other well penetrations
including drinking water supplies,
abandoned wells, other injection
activities
Geographic diversity, population
density
Potential to leverage with other
partners (NGOs, industry, states etc.)
Proximity to drinking water
resources
Potential for fluid migration beyond
HF zone and into underground
source of drinking water (USDW)
Potential for biogeochemical
mobilization of metals,
radionuclides, mineral salts, organic
contaminants and gases from gas-
bearing formations
Potential for surface water
withdrawals to affect drinking water
and/or impact flow regimes in
streams
Potential for ground water
withdrawal to affect water levels,
water quality, and the usability of
smaller aquifers for water supplies
Intensity and duration of HF activity
in a particular geographic location
Well logs (geologic
strata descriptions),
cement bond logs,
inventory of abandoned
wells nearby
Existing studies,
investigations
Site access
Identification of local
drinking water supplies
Chemical baseline data
for production well,
nearby drinking water
wells, other wells
Data on geologic
characteristics of HF
zone and overlying zones
Historical data on surface
water flows nearby
Historical data on nearby
water well levels
Identification of HF pads
and/or leases in a
particular area
Management of
wastewater and
residuals
Monitor flowback water,
produced water, residuals,
storm water, receiving water,
wastewater treatment
facilities:
Potential for runoff to surface water
Potential for infiltration of
wastewater to underlying USDW
from pit storage water
Proximity of treatment facilities that
accept fracturing wastes
Characteristics of
wastewater storage
systems
Relative location of
waste water treatment
plants and /or
underground injection
control (UIC) wells
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