Summary of the Technical Workshop on Case Studies to Assess Potential Impacts of Hydraulic Fracturing on Drinking Water Resources


x=,EPA
United States
Environmental Protection	November 2013 1 www.epa.gov/hfstudy
Agency
Summary of the Technical Workshop on
Case Studies to Assess Potential Impacts of
Hydraulic Fracturing on Drinking Water Resources
July 30, 2013

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EPA's Study of the Potential Impacts of Hydraulic Fracturing on Drinking Water Resources:
Summary of July 30, 2013, Technical Workshop on Case Studies to Assess Potential Impacts of Hydraulic Fracturing
on Drinking Water Resources
Disclaimer
This report was prepared by EPA with assistance from Eastern Research Group, Inc., an EPA
contractor, as a general record of discussions during the July 30, 2013, technical workshop on
case studies to assess potential impacts of hydraulic fracturing on drinking water resources. The
workshop was held to inform EPA's Study of the Potential Impacts of Hydraulic Fracturing on
Drinking Water Resources. The report summarizes the presentations and facilitated discussions
on the workshop topics and is not intended to reflect a complete record of all discussions. All
statements and opinions expressed represent individual views of the invited participants; there
was no attempt to reach consensus on any of the technical issues being discussed. Except as
noted, none of the statements in the report represent analyses or positions of EPA.
Mention of trade names or commercial products does not constitute endorsement or
recommendations for use.

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EPA's Study of the Potential Impacts of Hydraulic Fracturing on Drinking Water Resources:
Summary of July 30, 2013, Technical Workshop on Case Studies to Assess Potential Impacts of Hydraulic Fracturing
on Drinking Water Resources
Table of Contents
Final Agenda	1
Attendees List	3
Introduction	5
Summary of Presentations for Session 1: Background Assessment and Characterization... 7
Summary of Discussions Following Session 1: Background Assessment and
Characterization	10
Summary of Presentations for Session 2: Prospective Case Studies	14
Summary of Discussions Following Session 2: Prospective Case Studies	16
Concluding Remarks	18
Appendix A. Extended Abstracts from Session 1: Background Assessment and
Characterization	A-l
Appendix B. Extended Abstracts from Session 2: Prospective Case Studies	B-l

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EPA's Study of the Potential Impacts of Hydraulic Fracturing on Drinking Water Resources:
Summary of July 30, 2013, Technical Workshop on Case Studies to Assess Potential Impacts of Hydraulic Fracturing on
Drinking Water Resources
Technical Workshop on Case Studies to Assess
Potential Impacts of Hydraulic Fracturing on Drinking Water Resources
July 30, 2013
US EPA Research Triangle Park Campus
"C" Building Auditorium
Research Triangle Park, North Carolina
Final Agenda
8:00 am Registration/Check-in
8:30 am Welcome and Introductions	Ramona Trovato, US EPA
Glenn Paulson, Science Advisor, US EPA
8:40 am Opening Remarks	Ramona Trovato, US EPA
8:45 am Brief Overview of EPA's Study of the Potential Impacts of Hydraulic Fracturing
on Drinking Water Resources	Jeanne Briskin, US EPA
8:50 am Purpose of Workshop	Workshop Co-Chairs:
Cynthia Sonich-Mullin,
US EPA Timothy Fields,
MDB, Inc.
Session 1: Background Assessment and Characterization
9:00 am Panel:
Update on EPA's Retrospective Case Studies	Rick Wilkin, US EPA
Baseline Water Quality Characterization At Four US EPA Restrospective Case Study Areas	Tad Fox,
Battelle Memorial Institute
Evaluation of Water Quality Monitoring Programs and Statistical Analysis
Tools to be Utilized in Shale Development	Uni Blake, Hometown Energy Group
Surface Water and Stray Gas Shallow Aquifer Contamination	Avner Vengosh, Duke University
Designing a Retrospective Hydraulic Fracturing Case Study	 George Lukert,
Ecology and Environment, Inc.
Questions of Clarification
Break (10 minutes)
12:45 pm
1:00 pm
Facilitated discussion among workshop participants focusing on key questions:
-	What are the relative strengths of different approaches to assess background conditions?
-	What are practical approaches to overcoming the challenges in developing a representative background
assessment and characterization for a case study?
Summary of Session 1	Workshop Co-Chairs
Lunch
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EPA's Study of the Potential Impacts of Hydraulic Fracturing on Drinking Water Resources:
Summary of July 30, 2013, Technical Workshop on Case Studies to Assess Potential Impacts of Hydraulic Fracturing
on Drinking Water Resources
Session 2: Prospective Case Studies
2:00 pm Panel:
¦ Update on EPA's Prospective Case Studies
Jeanne Briskin, US EPA
¦ Geophysical Characterization and Borehole Geophysical Logging Tools to Aid Monitoring
Questions of Clarification Break (10 minutes)
Facilitated discussion among workshop participants focusing on key questions:
-	What types of conditions, tests, monitoring, sampling, and analysis are needed to assess impacts
from hydraulic fracturing processes on drinking water in a prospective case study, and why?
-	What approaches can be used in situations where historic and/or ongoing industrial practices
(e.g., mining, oil, gas, agriculture, etc.) may confound assessment of impacts of hydraulic
fracturing processes on drinking water resources?
Well Placement and Completion
Ron Sloto, USGS
¦ Groundwater Monitoring for EPA Prospective Study Site
Daniel Soeder, NETL
4:45 pm Summary of Session 2
Workshop Co-Chairs
4:50 pm Closing Remarks
Ramona Trovato, US EPA
5:00 pm Adjourn
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EPA's Study of the Potential Impacts of Hydraulic Fracturing on Drinking Water Resources:
Summary of July 30, 2013, Technical Workshop on Case Studies to Assess Potential Impacts of Hydraulic Fracturing
on Drinking Water Resources
Technical Workshop on Case Studies to Assess
Potential Impacts of Hydraulic Fracturing on Drinking Water Resources
July 30, 2013
Greg Appleton
Devon Energy
Sina Arjmand
University of Pittsburgh
Bruce Baizel
Earthworks
Ronald Bishop
SUNY College at Oneonta
Uni Blake *
Hometown Energy Group
John Bolakas
Stantec Consulting Services, Inc.
Jeanne Briskin *
US EPA Office of Research and Development
Barbara Butler
US EPA ORD/National Risk Management
Research Laboratory
Craig Cipolla
HESS Corporation
Isabelle Cozzarelli US
Geological Survey
Timothy Fields (co-chair)
MDB, Inc.
Robert Ford
US EPA ORD/National Risk Management
Research Laboratory
Tad Fox *
Battelle Memorial Institute
Lloyd Hetrick
Newfield Exploration
Christopher Hill
Chesapeake Energy Corporation
Anthony Ingraffea
Cornell University
George King
Apache Corporation
Holly Kneeshaw
New York State Department of
Environmental Conservation
Thomas Kropatsch
Wyoming Oil and Gas Conservation
Commission
George Lukert *
Ecology and Environment, Inc.
Greg Manuel
Pioneer Natural Resources
Lisa Matthews
US EPA Office of Research and Development
Mike Nickolaus
Ground Water Protection Council
Kathleen Nolan
Catskill Mountainkeeper
* Presenter
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EPA's Study of the Potential Impacts of Hydraulic Fracturing on Drinking Water Resources:
Summary of July 30, 2013, Technical Workshop on Case Studies to Assess Potential Impacts of Hydraulic Fracturing
on Drinking Water Resources
Kris Nygaard
ExxonMobil Production Company
Jennifer Orme-Zavaleta
US EPA National Exposure Research
Laboratory
Michael Overbay
US EPA Region 6
Glenn Paulson
US EPA, Science Advisor
M. Seth Pelepko
Pennsylvania Department of Environmental
Protection
Pete Penoyer
National Park Service
Peter Pope
Railroad Commission of Texas
James Richenderfer
Susquehanna River Basin Commission
John Robinson
Dewberry Engineers, Inc.
David Russell
QEP Resources
Steve Shost
New York State Department of Health
Ron Sloto *
US Geological Survey
Bert Smith
Chesapeake Energy Corporation
Kelly Smith
US EPA ORD/National Risk Management
Research Laboratory
Daniel Soeder *
US Department of Energy National Energy
Technology Laboratory
Cynthia Sonich-Mullin (co-chair)
US EPA ORD/National Risk Management
Research Laboratory
Daniel Stephens
Daniel B. Stephens and Associates, Inc.
Ramona Trovato
US EPA Office of Research and Development
Mindy Vanderford
GSI Environmental, Inc.
Avner Vengosh *
Duke University
Norman Warpinski
Pinnacle - A Halliburton Service
Rick Wilkin *
US EPA/National Risk Management
Research Laboratory
Ming Zhu
US Department of Energy
4
* Presenter

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EPA's Study of the Potential Impacts of Hydraulic Fracturing on Drinking Water Resources:
Summary of July 30, 2013, Technical Workshop on Case Studies to Assess Potential Impacts of Hydraulic Fracturing
on Drinking Water Resources
Introduction
At the request of Congress, the U.S. Environmental Protection Agency (EPA) is conducting a
study to better understand the potential impacts of hydraulic fracturing on drinking water
resources. The scope of the research includes the full cycle of water associated with hydraulic
fracturing activities. In the study, each stage of the water cycle is associated with a primary
research question:
•	Water acquisition: What are the possible impacts of large volume water withdrawals
from ground and surface waters on drinking water resources?
•	Chemical mixing: What are the possible impacts of hydraulic fracturing fluid surface
spills on or near well pads on drinking water resources?
•	Well injection: What are the possible impacts of the injection and fracturing process on
drinking water resources?
•	Flowback and produced water: What are the possible impacts of surface spills on or
near well pads of flowback and produced water on drinking water resources?
•	Wastewater treatment and waste disposal: What are the possible impacts of
inadequate treatment of hydraulic fracturing wastewaters on drinking water resources?
In 2013, EPA hosted a series of five technical workshops related to its Study of the Potential
Impacts of Hydraulic Fracturing on Drinking Water Resources. The workshops included
Analytical Chemical Methods (February 25, 2013), Well Construction/Operation and Subsurface
Modeling (April 16-17, 2013), Wastewater Treatment and Related Modeling (April 18, 2013),
Water Acquisition Modeling (June 4, 2013), and Case Studies (July 30, 2013). The workshops
were intended to inform EPA on subjects integral to enhancing the overall hydraulic fracturing
study, increasing collaborative opportunities and identifying additional possible future research
areas. Each workshop addressed subject matter directly related to the primary research questions.
For each workshop, EPA invited experts with significant relevant and current technical
experience. Each workshop consisted of invited presentations followed by facilitated discussion
among all invited experts. Participants were chosen with the goal of maintaining balanced
viewpoints from a diverse set of stakeholder groups, including industry; nongovernmental
organizations; other federal, state and local governments; tribes; and the academic community.
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EPA's Study of the Potential Impacts of Hydraulic Fracturing on Drinking Water Resources:
Summary of July 30, 2013, Technical Workshop on Case Studies to Assess Potential Impacts of Hydraulic Fracturing
on Drinking Water Resources
The Case Studies workshop was co-chaired by Cynthia Sonich-Mullin (EPA) and Timothy
Fields (MDB, Inc.). A morning session addressed Background Assessment and Characterization,
while the afternoon session focused on Prospective Case Studies.
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EPA's Study of the Potential Impacts of Hydraulic Fracturing on Drinking Water Resources:
Summary of July 30, 2013, Technical Workshop on Case Studies to Assess Potential Impacts of Hydraulic Fracturing
on Drinking Water Resources
Summary of Presentations for Session 1:
Background Assessment and Characterization
Susan Hazen, Hazen Consulting and Support Services, opened the workshop. She noted that
EPA was looking for individual participants' frank input and opinion and was not trying to reach
consensus on the topics; the workshop was not held under the rules of the Federal Advisory
Committee Act (FACA). Dr. Glenn Paulson, Science Advisor to the EPA Administrator, and
Ramona Trovato, Associate Assistant Administrator of EPA's Office of Research and
Development (ORD), welcomed the participants and thanked them for contributing their
knowledge and experience. Ms. Trovato stated that the case studies, which will inform EPA's
Study of the Potential Impacts of Hydraulic Fracturing on Drinking Water Resources, will be
peer reviewed. EPA expects to complete the prospective case studies1 after its draft report is
issued in December 2014. Ms. Trovato noted that EPA did not have conclusions to share at this
workshop; the data are undergoing quality assurance and will be posted on the study website.2
Workshop Co-Chairs Cynthia Sonich-Mullin, Director of EPA's National Risk Management
Research Laboratory, and Timothy Fields (MDB, Inc.) also welcomed the participants and then
described the three goals of the workshop: enhance EPA's study, foster collaboration and inform
future research needs.
Jeanne Briskin, Coordinator of Hydraulic Fracturing Research, EPA Office of Research and
Development, presented an overview of EPA's drinking water study to provide context for
discussion of the case studies. Ms. Briskin noted that the overall goals of EPA's study are to
assess whether hydraulic fracturing may impact drinking water resources, and to identify any
driving factors that may influence the severity and frequency of any potential impacts. She
discussed the primary research questions associated with each stage of the hydraulic fracturing
water cycle, the secondary research questions and the associated research activities, including
case studies. She presented EPA's timeline for the study, noting that the technical roundtables
will reconvene in fall 2013. Ms. Briskin stated that EPA is interested in receiving additional data
to inform the study; the deadline for submitting data and scientific literature has been extended to
November 15, 2013.
Dr. Richard Wilkin, EPA National Risk Management Research Laboratory, presented an
update on EPA's retrospective case studies. The purpose of the case studies is to determine if
1 Prospective case studies involve sites where hydraulic fracturing will be implemented after the research begins,
which allows sampling and characterization of the site before, during, and after drilling, injection of the fracturing
fluid, flowback, and production. Retrospective case studies focus on investigating reported instances of drinking
water resource contamination in areas where hydraulic fracturing events have already occurred.
2 http://www.epa. gov/hfstudv
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EPA's Study of the Potential Impacts of Hydraulic Fracturing on Drinking Water Resources:
Summary of July 30, 2013, Technical Workshop on Case Studies to Assess Potential Impacts of Hydraulic Fracturing
on Drinking Water Resources
drinking water contamination has occurred at the study location, and, if so, identify possible
sources of contamination. He described the process for identifying and selecting case study
locations. EPA considered more than 40 sites and chose five based on a set of criteria outlined in
the Study Plan (proximity of population and drinking water supplies, evidence of impaired water
quality, health and environmental concerns, and knowledge gaps that the case study could fill).
Dr. Wilkin described the characteristics, research focus and progress to date for each of the case
studies: Las Animas/Huerfano Counties (Raton Basin), Colorado; Bradford County,
Pennsylvania; Washington County, Pennsylvania; Wise County, Texas; and Dunn County
(Killdeer), North Dakota. The most recent samples were collected in spring 2013; the next major
activities are data analysis, comparison of new data with historical data, temporal and spatial
evaluation, geochemical modeling and evaluation, and environmental record searches.
Tad Fox, Battelle Memorial Institute, discussed Battelle's work to characterize baseline water
quality at EPA retrospective case study areas—specifically, to characterize historical water
quality of springs, ground water wells and surface water sources, and to identify the potential for
adverse impacts from land use activities before the beginning of unconventional oil and gas
development. Battelle offered this work to help EPA evaluate the site-specific data collected for
the retrospective case studies, by helping determine whether those data fall within the observed
baseline range and what other potential sources should be considered if a water quality impact is
detected. Battelle used readily available water quality data and land use information for this
effort. The data characterize water resource quality characteristics at a regional level; data were
not available on a smaller scale. Mr. Fox presented summary findings for four case study
locations (data for the fifth, Raton Basin, were not available within Battelle's study time frame).
He stated that the data show extensive prior industrial and agricultural use within the EPA study
areas, and historical background water quality data are absent or limited for some parameters
(particularly organic chemicals). For these reasons, Battelle believes that rigorous, site-specific
analysis and multiple lines of evidence would be needed to differentiate impacts from pre-
existing conditions and impacts from other potential sources of contamination, including
hydraulic fracturing.
Uni Blake, Hometown Energy Group, discussed the evaluation of water quality monitoring
programs and statistical analysis tools to be used in shale development. She stated that natural
spatial variations in the hydrogeology of domestic wells present difficulties when creating a
pooled background database for inter-well analysis. She said that current monitoring programs
with one pre-sampling data point per well cannot determine prior contamination, provide
insufficient data for statistical analysis, and do not take into account variability in parameters or
long-term changes that may occur. She provided recommendations for trend monitoring
sampling to augment the baseline monitoring program. Recommendations include sampling at
ground water wells and surface water locations downgradient from the well pad, monthly data
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EPA's Study of the Potential Impacts of Hydraulic Fracturing on Drinking Water Resources:
Summary of July 30, 2013, Technical Workshop on Case Studies to Assess Potential Impacts of Hydraulic Fracturing
on Drinking Water Resources
collection two years before and two years after shale activities commence, and the use of
statistical methods that can identify non-parametric trends.
Dr. Avner Vengosh, Duke University, discussed surface water and stray gas shallow aquifer
contamination. The approach of his study was to define the major geochemical features that
characterize ground water and surface water before shale gas development, and link possible
water contamination to changes in water chemistry using multiple, novel geochemical and
isotopic tracers as proxies for sources and mechanisms of contamination. He stated that looking
at exceedances of drinking water parameters as evidence, or lack thereof, of contamination is
insufficient. He described two parallel investigations: 1) sampling of surface waters and river
sediments downstream from wastewater disposal sites, and evaluation of aquatic geochemistry,
isotopes and radionuclides; and 2) for ground water, sampling of shallow private wells and
analysis of hydrocarbon, aqueous and noble gas geochemistry. He presented the following
conclusions: 1) evidence exists for stray gas contamination in a subset of shallow wells near
shale gas wells in northeastern Pennsylvania; 2) in contrast, no evidence exists for methane
contamination of shallow ground water in north central Arkansas, indicating a possible role of
local geology and/or drilling practices in stray gas contamination; 3) evidence exists for
hydraulic connectivity between the Marcellus and shallow aquifers in Pennsylvania, but no
evidence has shown direct ground water contamination from produced/flowback water; and 4) in
Pennsylvania, evidence exists for surface water contamination from wastewater disposal sites
and accumulation of radium in river sediments. Dr. Vengosh recommended a zero-discharge
policy for wastewater.
George Lukert, Ecology and Environment, Inc., discussed an approach for evaluating case
study data for causal assessment. He presented a decision support system using a tiered approach
for analyzing retrospective sites. Tier 1 involves identification of candidate causes of
contamination, evaluating these potential causes using a conceptual site model, and analyzing
existing data to eliminate candidate causes not related to the potential sources. Tier 2 includes a
preliminary screening to determine if candidate causes can be linked to an effect, initial
sampling, data evaluation, initial causal analysis and identification of data gaps. Tier 3 includes
site-specific studies to fill data gaps and produce valid evidence. Finally, in Tier 4, probable
candidate causes are determined and designated as principal or secondary causes, and the data
undergo quality assurance evaluation. Mr. Lukert noted that multiple causes may be responsible
for the environmental impairment, and studies to determine a unique principal cause may be
technically or financially impractical.
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EPA's Study of the Potential Impacts of Hydraulic Fracturing on Drinking Water Resources:
Summary of July 30, 2013, Technical Workshop on Case Studies to Assess Potential Impacts of Hydraulic Fracturing
on Drinking Water Resources
Summary of Discussions Following Session 1:
Background Assessment and Characterization
Following some clarifying questions, participants were asked to consider the following questions
during the discussion:
•	What are the relative strengths of different approaches to assess background conditions?
•	What are practical approaches to overcoming the challenges in developing a
representative background assessment and characterization for a case study?
Key themes from Session 1 discussion:
What data to collect/use in the assessment and characterization
Several participants discussed the importance of understanding site-specific geochemistry as well
as gathering background data, and noted that many issues complicate a retrospective analysis
(e.g., past hydrocarbon production). Several participants noted the importance of optimizing a
conceptual site model to help guide an initial causal analysis at a site. A participant
recommended an introductory paragraph in the case studies describing the site-specific geology.
A participant noted that there are many things that we do not understand about the shales being
studied, such as the origin of brines, or where injected water goes, and the help of industry is key
to better understanding these issues.
A participant noted that site characterization is key to identifying appropriate tracers and
indicators. Another participant suggested using studies led by researcher Brian Fontenot3 to
identify unique parameters that may be present, but not in high concentrations, and then looking
at data for quantitative "cut points," rather than absolute values. She also noted that the presence
of parameters not present in the background could be helpful in identifying pathways (e.g.,
surface release).
A participant said that monitoring should focus on methane, rather than rarely detected fracturing
fluid components, and that the borehole, rather than induced fractures, is the main pathway of
migration. The participant suggested a focused approach to differentiate surface release and
gravity flow.
3 Fontenot, B.E., Hunt, L.R., Hildenbrand, Z.L., Carlton, D.D., Jr., Oka, H., Walton, J.L., Hopkins, D., Osorio, A., Bjorndal, B.,
Hu, Q.H., & Schug, K.A. (2013). An evaluation of water quality in private drinking water wells near natural gas extraction sites
in the Barnett Shale formation. Environmental Science & Technology 47(11), 10032-10040.
http://pubs.acs.org/doi/abs/10.1021/es4011724?prevSearch=Fontenot&searchHistorvKev
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EPA's Study of the Potential Impacts of Hydraulic Fracturing on Drinking Water Resources:
Summary of July 30, 2013, Technical Workshop on Case Studies to Assess Potential Impacts of Hydraulic Fracturing
on Drinking Water Resources
Several participants stated that it is important to have a monitoring plan with defined objectives,
specifying representative locations within an aquifer, sampling frequency and parameters. A
participant noted that the industry is growing and needs a long-term monitoring plan.
A participant said that industry does not try to study every detail of every well. He said that oil
and gas wells contribute a very small percentage of ground water pollution incidents, and that it
is more productive to focus on proven causes of ground water contamination (e.g., gasoline,
sewage, animal feedlots). Another participant said that it was important not to minimize the
possibility of ground water contamination, citing a May 2013 Science article4 concluding that 1
to 3 percent of new wells show casing failure, which can lead to problems with shallow ground
water quality.
Issues regarding background data
Several participants raised potential problems with using background information from
databases: sampling may have been targeted at sites with anthropogenic, not background,
contamination (industrial site, landfills, salt storage); there may be geology-specific issues (such
as elevated radium in the Chickies formation); and sample collection methods and quality may
be unknown. A participant stated that anthropogenic sources of contamination should be
considered as part of the background. Several participants questioned the value of a retrospective
study if the data are not adequate, and stated that more might be learned from the prospective
studies. Another participant expressed the view that starting from a known incident is very
valuable, and that the challenges in defining background are not unique to hydraulic fracturing,
but apply to any environmental investigation.
Several participants noted that guidance for RCRA and CERCLA sites has been available for
many years, and asked how collecting data for a hydraulic fracturing retrospective study is
different. A participant noted that the guidance documents typically address a specific site (such
as a landfill or underground storage tank), while the investigation area for hydraulic fracturing
may be much larger. The participant stated that the temporal scale was also different, noting
potential temporal variability when studying potential effects of hydraulic fracturing (seasonal
variation, use of road salt, etc.).
Several participants noted that, in addition to areal distribution evaluations (i.e., county-wide
evaluations), an important approach for background evaluations is to examine aquifer-specific
(depth-related) background and water quality trends.
4 Vidic, R.D., Brantley, S.L., Vandenbossche, J.M., Yoxtheimer, D., & Abad, J.D. (2013). Impact of shale gas development on
regional water quality. Science 340(6134): 1235009. http://www.sciencemag.org/content/340/6134/1235009.abstract
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EPA's Study of the Potential Impacts of Hydraulic Fracturing on Drinking Water Resources:
Summary of July 30, 2013, Technical Workshop on Case Studies to Assess Potential Impacts of Hydraulic Fracturing
on Drinking Water Resources
A participant noted that county- or state-wide background data would not be used for a RCRA or
CERCLA study. The participant stated that some of the wells sampled to study potential effects
of hydraulic fracturing may be too far away to see impacts; instead, wells without alleged
impacts in the same area should be sampled. Another participant expressed the view that
background levels can best be established at a regional scale, and that regional data are useful for
identifying trends.
A participant clarified that EPA's retrospective case studies do not present background levels for
a case study area (i.e., levels present at the sampling locations prior to gas development); rather,
they use available historical data to identify a range of levels present in the region around the
area, to help determine whether there may be an impact and whether further study is warranted.
Statistical approaches
A participant stated that when data are averaged and pooled, there is a risk of diluting the signal.
The participant said that the key is aquifer-based analysis, and that the focus should be on
individual cases using a match case-control design (rather than comparing to background).
A participant noted that there are many opportunities to improve statistical analyses, including
analyzing geochemistry using principal component analysis and cluster analysis. The participant
noted that Stiff diagrams and Piper diagrams could be useful for graphical presentation of data.
Ground water contamination occurrence and exposure
A participant said that public health data could be important for the case studies. She stated that
health impacts could be early indicators of water contamination; if these impacts resolve over
time after water quality has improved or alternate water provided, that could provide helpful
information.
A participant noted that it is not enough to detect a contaminant in ground water: exposure also
has to occur, at sufficient quantities, for there to be toxic effects. The participant also stated that
exposure to a single chemical is unlikely, so cumulative exposure and exposure to mixtures of
multiple contaminants should be considered.
A participant stated that it is important to clearly define "impact" and how it relates to risk.
Another participant emphasized the importance of tracing contamination to its source and
continuing to provide context to the public (e.g., comparing the risks from hydraulic fracturing to
familiar risks).
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EPA's Study of the Potential Impacts of Hydraulic Fracturing on Drinking Water Resources:
Summary of July 30, 2013, Technical Workshop on Case Studies to Assess Potential Impacts of Hydraulic Fracturing
on Drinking Water Resources
Practical approaches for overcoming challenges
Individual participants offered a wide range of suggestions for overcoming challenges:
•	Involve high-level scientists from the nation's world-class academic institutions to
overcome limitations of these studies.
•	Work with preliminary results from the U.S. Department of Energy (DOE) National
Energy Technology Laboratory studies with tracers identifying some quantitative
benchmarks (e.g., levels of ethane or propane).
•	Use statistical techniques and other appropriate techniques to analyze geochemistry (e.g.,
Stiff diagrams, stable isotope evaluation).
•	Ensure that both industry and universities make their data available, to the extent
possible.
•	Instead of relying on information from agency databases, collect distributed samples
using approved methods.
•	Use a case control design (comparing to uncontaminated wells rather than to
background).
•	Look at case studies individually to consider how useful the background data might be.
•	Use a probability density function with very large, regional data sets collected over a
significant period to identify anomalies; then focus on a site if something stands out.
•	Because drilling often takes place in sites that are already contaminated, making it
difficult to identify causal mechanisms, consider requiring cleanup to a certain level
before any hydraulic fracturing activities begin. (Such a policy choice would also have
environmental justice implications.)
•	Consider modifying the goals of the retrospective studies so they are in line with what the
available data can answer.
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EPA's Study of the Potential Impacts of Hydraulic Fracturing on Drinking Water Resources:
Summary of July 30, 2013, Technical Workshop on Case Studies to Assess Potential Impacts of Hydraulic Fracturing
on Drinking Water Resources
Summary of Presentations for Session 2:
Prospective Case Studies
Jeanne Briskin, EPA, presented an overview of EPA's prospective case study approach. The
study goals are to understand how site-specific hydraulic fracturing practices prevent impacts to
drinking water resources, and to evaluate any changes in water quality over time. Ms. Briskin
presented examples of environmental management practices by well operators throughout the
life cycle of a production well (site selection, baseline monitoring, pad installation/well drilling
and completion, hydraulic fracturing and flowback management, and oil/gas production) and
case study research goals and implementation tasks at each stage of well development and
operation. She noted that collaboration among partners (e.g., EPA, DOE, U.S. Geological Survey
[USGS], well owners/operators, state agencies, landowners) is important for case study design,
implementation and interpretation. She stated that water quality monitoring for the case studies is
expected to involve both use of pre-existing monitoring points and installation of additional
targeted monitoring wells. At a minimum, one year would be required for baseline sampling and
one year or more for post-fracture sampling. Ms. Briskin described potential technical challenges
in the case studies (such as existing or legacy fossil fuel extraction or other land use, site-specific
aquifer properties) and implementation challenges (e.g., access to the well pad, alignment of
research and commercial timelines).
Ron Sloto, USGS, discussed geophysical characterization and borehole geophysical tools to aid
monitoring well placement and completion. He defined borehole geophysics as the collection of
geologic and hydrologic information in wells by lowering and raising probes on a wire. He said
that much more can be learned by analyzing a suite of geophysical logs as a group than by
analyzing the same logs individually. For new wells, borehole geophysics can be used to
determine where to set the well screen, aquifer characteristics, and hydraulic connections
between monitoring wells. For existing wells, it can be used to obtain information on well
construction characteristics, aquifer hydraulic characteristics, and water quality. Mr. Sloto
described each of the standard borehole geophysics logs: caliper, gamma, single-point resistance,
fluid temperature, fluid resistivity, heat pulse flowmeter, borehole television and acoustic
televiewer. He also described the use of a wire-line sampler to capture borehole fluid from a
discrete depth, and the use of aquifer-isolation tests to define hydraulic and chemical
characteristics of discrete water-bearing fractures in a borehole. Finally, he presented an example
of how analysis of a suite of borehole geophysical logs helped identify the source of
trichloroethylene in two water supply wells in Montgomery County, Pennsylvania.
Daniel Soeder, DOE National Energy Technology Laboratory, discussed ground water
monitoring for an EPA prospective case study site. He stated that ground water monitoring is
needed because drilling through shallow aquifers and hydraulic fracture pressure pulses can
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EPA's Study of the Potential Impacts of Hydraulic Fracturing on Drinking Water Resources:
Summary of July 30, 2013, Technical Workshop on Case Studies to Assess Potential Impacts of Hydraulic Fracturing
on Drinking Water Resources
affect ground water, and data are needed on stray gas mobilization, fluid infiltration and water
quality effects. Surface leaks and spills, he said, are the primary risk to ground water from shale
gas operations. He discussed ground water risks during each phase of production (initial spud-in
through long-term gas production), noting that the risks are highly phase- and time-dependent.
He then described plans for ground water monitoring at a prospective case study site (once a site
is identified). Three monitoring wells would be installed off the pad, one up-gradient and two or
three down-gradient. Mr. Soeder described the well design standards that would be met and the
drilling procedures that would be followed. Sampling would use a multilevel insert in the well to
collect ground water from various depths to characterize the aquifer. Next steps would include
identifying an industry cooperator and landowners who would allow placement of the wells in
the vicinity of the shale gas well site; decision-making by the DOE-EPA-USGS team about well
locations, depth, aquifer zones and water sampling; and contact with other shale gas drillers in
other areas for similar access, for comparison studies.
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Summary of Discussions Following Session 2:
Prospective Case Studies
Following clarifying questions, participants were asked to consider the following questions
during the discussion:
•	What types of conditions, tests, monitoring, sampling and analysis are needed to assess
impacts from hydraulic fracturing processes on drinking water in a prospective case study,
and why?
•	What approaches can be used in situations where historical and/or ongoing industrial
practices (e.g., mining, oil, gas, agriculture, etc.) may confound assessment of impacts of
hydraulic fracturing processes on drinking water resources?
Key themes from Session 2 discussion:
A participant recommended selecting sites for the prospective case studies where the geology is
well characterized. He suggested two sites in the Marcellus formation.
A participant recommended refining the objectives of the case studies to better select and design
the measurement system (e.g., what is the next level after measurement of ground water
contamination—methane migration, fracturing fluid, etc.?). An EPA participant noted that EPA
intends to clarify objectives once the specific sites for the case studies are located.
Another participant noted that most immediate impacts (within one year) are from stray gas
migration; a longer-term study would add value. The participant suggested studying how
hydraulic fracturing might affect the ability of production string cement to maintain zonal
isolation, and also suggested monitoring for more subtle changes in dissolved methane at water
supplies over the longer term.
A participant stated that ground water is important, but he questioned the lack of attention to
impacts to surface water from wastewater disposal. An EPA participant stated that Congress
asked EPA to look at drinking water resources; EPA's National Pollutant Discharge Elimination
System permit program is working on effluent limits for disposal, but the issue of disposal of
wastewaters into surface water is beyond the scope of the drinking water study (Chapter 13 of
the study plan,5 she noted, discusses this and other research needs). Another participant stated
that returning produced water to surface water is a regional, not a national, issue.
A participant stated that much of the discussion about the prospective studies could inform the
retrospective studies, and vice versa. She encouraged EPA to look for rich data about
5 http://www2.epa.gov/sites/production/files/documents/hf study plan 110211 final 508.pdf
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hydrogeology (e.g., understanding how a pressure wave could cause high total dissolved solids in
a homeowner's well).
A participant raised the idea of horizontal monitoring wells. Another participant stated that
horizontal wells are typically used in the shallow subsurface for remediation technology, but
could be used for monitoring. Several participants described the use of tool stabilizers and ways
to pull the logging tool to the end of the well.
A participant stated his view that having an onsite monitor should be a condition for establishing
effective monitoring. Another participant disagreed, stating that operators work with regard for
public safety and the environment, and their license to operate is contingent on following rules
and reporting.
A participant described the Interagency Steering Committee on Multimedia Environmental
Modeling (ISCMEM), which has six working groups: 1) software systems design and
implementation for environmental modeling, 2) uncertainty analysis and parameter estimation, 3)
subsurface reactive solute transport modeling, 4) distributed watershed/water quality modeling,
5) environmental forecasting (ecosystem services), and 6) integrated monitoring and modeling.
He noted that the ISCMEM's work to advance environmental modeling could be useful for the
case study effort.
A participant stated that sampling for microbial indicators could be considered.
Another participant said that conceptual model building for the prospective studies, using lessons
from the retrospective studies, is very important and will increase the chances that the case
studies will yield useful information.
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Concluding Remarks
Ms. Trovato and Dr. Glenn Paulson, EPA, thanked the participants for attending and sharing
their knowledge and experience. Ms. Trovato reminded the participants that once the technical
workshops are completed, the technical roundtables will be reconvened to further inform the
drinking water study. She noted that the cooperation represented in these workshops will help
advance the nation's economy, jobs, the environment, health and drinking water resources. She
stated that other nations are watching to understand how best to conduct hydraulic fracturing, so
this effort will benefit the world.
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Appendix A.
Extended Abstracts from Session 1:
Background Assessment and Characterization
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Update on EPA's Retrospective Case Studies
Richard Wilkin
United States Environmental Protection Agency
Office of Research and Development
Information presented in this abstract is part of the EPA's ongoing study. EPA intends to use
this, combined with other information, to inform its assessment of the potential impacts to
drinking water resources from hydraulic fracturing. Mention of trade names or commercial
products does not constitute endorsement or recommendation for use.
Introduction
As part of the United States Environmental Protection Agency's (EPA) study on the potential
impacts of hydraulic fracturing on drinking water resources, scientists are conducting case
studies at different locations throughout the United States. The purpose of conducting
retrospective case studies is to investigate if drinking water contamination has occurred at the
case study locations and, if so, to investigate possible sources of contamination.
EPA's scientific approach to these case studies leverages over 30 years of experience identifying
potential sources and pathways of contamination at sites with limited background information.
Case studies are widely used to conduct in-depth investigations of complex topics and provide a
systematic framework for investigating relationships among relevant factors. In conjunction with
other elements of the research program, they help determine if hydraulic fracturing can impact
drinking water resources and, if so, the extent and possible causes of any impacts. Case studies
may also provide opportunities to assess the fate and transport of fluids and contaminants in
different regions and geologic settings. Depending on the findings, results from the case studies
may help answer the secondary research questions listed in Table 1.
Table 1. Secondary research questions addressed by conducting case studies.	

Chemical mixing
• If spills occur, how might hydraulic fracturing
chemical additives contaminate drinking water
resources?
Well injection
•	How effective are current well construction practices
at containing gases and fluids before, during, and after
hydraulic fracturing?
•	Can subsurface migration of fluids or gases to
drinking water resources occur, and what local
geologic or man-made features might allow this?
Flowback and produced
water
• If spills occur, how might hydraulic fracturing
wastewaters contaminate drinking water resources?
Two types of case studies are being conducted as part of this study. Retrospective case studies
focus on investigating reported instances of drinking water resource contamination in areas
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where hydraulic fracturing events have already occurred. Prospective case studies involve sites
where hydraulic fracturing would be implemented after the research begins, to allow sampling
and characterization of the site before, during, and after drilling, injection of the fracturing fluid,
flowback, and production. This presentation will focus on the progress of retrospective case
studies only.
Selection of Case Study Locations
To select the retrospective case study sites, the EPA invited stakeholders from across the country
to participate in the identification of locations for potential case studies through informational
public meetings and the submission of electronic or written comments. Following thousands of
comments, over 40 locations were nominated for inclusion in the study. These locations were
prioritized and chosen based on a rigorous set of criteria, including proximity of population and
drinking water supplies, evidence of impaired water quality, health and environmental concerns,
and knowledge gaps that could be filled by a case study at each potential location. Sites were
prioritized based on geographic and geologic diversity, population at risk, geologic and
hydrologic features, characteristics of water resources, and land use (US EPA, 2011).
Five retrospective case study locations were ultimately chosen for inclusion in this study and are
shown in Figure 1.
1. Southwest Pennsylvania: Washington County
2. Wise County, Texas
3. Raton Basin: Las Animas and Huerfano counties, Colorado
4. Northeast Pennsylvania: Bradford County
5. Killdeer: Dunn County, North Dakota
The status of these studies is documented in the EPA's "Study of the Potential Impacts of
Hydraulic Fracturing on Drinking Water Resources Progress Report' (EPA 2012).
General Research Approach
Each retrospective case study differs in geologic and hydrologic characteristics, hydraulic
fracturing techniques, and the oil and gas exploration and production history of the area.
However, the overall study approach used to assess potential drinking water impacts was applied
to all of the study sites. By coordinating the case study approach and chemical analyses, it will
be possible to compare the results of each study.
EPA developed a Quality Assurance Project Plan (QAPP) for each retrospective case that
describes the detailed plan for the research at that location. The QAPP integrates the technical
and quality aspects of the case study in order to provide a guide for obtaining the type and
quality of environmental data required for the research. Before each new tier of sampling
begins, the QAPPs are revised to include any additional work. QAPPs also revised if the
approach needs to be revised within a tier.
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Bakkan
¦
Dunn
N
W-jt-E
S
Bradford
Marcellus
Susquehanna
Washington
Huerfano [_gS Animas
Raton Basin
Wise
¦
Bamett
Legend
¦ Counties with EPA Case Studies
Hydrocarbon Reservoirs
States
County Names in Bold
0	360	720 Mites
1—+—)—I—I—f—t—i—I
0	57S	1,150 Kilometers
Projection: Albers Equal Area Conic
Figure 1. Locations of the five retrospective case studies chosen for inclusion in the EPA's Study of
the Potential Impacts of Hydraulic Fracturing on Drinking Water Resources.
Ground water samples have been collected at all retrospective case study locations. The samples
come from a variety of available sources, such as existing monitoring wells, domestic and
municipal water wells, production wells, and springs. Surface water, if present, has also been
sampled. During sample collection, the following water quality parameters were monitored and
recorded:
•	Temperature
•	pH
•	TDS
•	Specific conductance
•	Alkalinity
Turbidity
Dissolved oxygen
Oxidation/reduction potential
Ferrous iron
Hydrogen sulfide
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Each water sample has been analyzed for a suite of chemicals. Groups of analytes and examples
of specific chemicals of interest are listed in Table 2. These chemicals include major anions,
reported components of hydraulic fracturing fluids (e.g., glycols), and potentially mobilized
naturally occurring substances (e.g., metals); these chemicals are thought to be present frequently
in hydraulic fracturing fluids or wastewater. As indicated in Table 2, stable isotope analyses are
also being conducted. Stable isotope ratios can provide information about biogeochemical
processes that impact the behavior of certain elements in the environment.
Table 2. Analyte groupings and examples of chemicals measured in water samples collected
at the retrospective case study locations.
BWIBltlB II ¦
Anions
Bromide, chloride, sulfate
Carbon group
Dissolved organic carbon, dissolved inorganic carbonf
Dissolved gases
Methane, ethane, propane
Extractable petroleum hydrocarbons
Gasoline range organics, § diesel range organics J
Glycols
Diethylene glycol, triethylene glycol, tetraethylene glycol
Isotopes
Isotopes of oxygen and hydrogen in water, carbon and
hydrogen in methane, strontium
Low molecular weight acids
Formate, acetate, butyrate
Measures of radioactivity
Radium, gross a, gross P
Metals
Arsenic, manganese, iron
Semivolatile organic compounds
Benzoic acid; 1,2,4-trichlorobenzene; 4-nitrophenol
Surfactants
Octylphenol ethoxylate, nonylphenol
Volatile organic compounds
Benzene, toluene, styrene
f Dissolved inorganic carbon is the sum of the carbonate species (e.g., carbonate, bicarbonate)
dissolved in water.
§
Gasoline range organics include hydrocarbon molecules containing 5-12 carbon atoms.
{ Diesel range organics include hydrocarbon molecules containing 15-18 carbon atoms.
Case Study Summaries
EPA has collected water samples from five retrospective case study locations (Colorado, North
Dakota, Pennsylvania, and Texas) during Tier 2 of the study. Samples were collected during
multiple sampling trips beginning in fall 2010 and ending in spring 2013. Water samples have
been collected from domestic water wells, monitoring wells, and surface water sources, among
others.
Las Animas & Huerfano Counties, Colorado — Raton Basin
Through the stakeholder process, concerns about local drinking water have been reported in
areas located within the Raton Basin. After evaluating the sites, the EPA determined that several
areas within the Raton Basin would be good candidates for the study. In the Raton Basin,
several areas in Las Animas County and Huerfano County were targeted for ground water and
surface water sampling several geographic locations. The hydraulic fracturing in this area is
focused on recovering coal bed methane from the Raton Basin.
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The case study focuses on two areas: "North Fork Ranch" in Las Animas County and "Little
Creek" in Huerfano County. Study sites were selected in response to ongoing complaints about
changes in appearance, odor, and taste associated with drinking water in domestic wells.
Samples were collected from domestic wells, production wells, monitoring wells, and surface
water (streams) from Las Animas and Huerfano counties. The following is a summary of each
event:
• Round 1 (October 2011 sampling event) - Samples were collected from 12 domestic
wells, two production wells, five monitoring wells, and one surface water location.
• Round 2 (May 2012 sampling event) - Samples were collected from 12 domestic wells,
two production wells, three monitoring wells, and three surface water locations.
• Round 3 (November 2012 sampling event) - Similar locations from Round 2 were
sampled and the same analytes were tested.
• Round 4 (May 2013 sampling event) - Similar locations from Round 3 were sampled
and the same analytes were tested.
Bradford County, PA
Northeast PA (NE PA) was selected as a case study site because it is an area of extensive
hydraulic fracturing activity, and has received considerable media attention due to citizen
concerns over the potential impacts to drinking water resources. The locations were selected due
to the large number of homeowner complaints about changes in water appearance (turbidity and
bubbling) and odor; reported surface water contamination; and reported methane contamination
of multiple drinking water wells. Hydraulic fracturing in this area focuses on recovering natural
gas from the Marcellus Shale.
In NE PA, several areas in Bradford County and Susquehanna County were targeted for ground
water/surface water sampling. Initial sampling locations were selected during a reconnaissance
trip to the area conducted in August 2011. Water samples were collected for analysis from
different locations within the two counties, during three rounds of sampling events. The
following is a summary of each event:
• Round 1 (October/November 2011 sampling event) - Only four water samples were
collected in Susquehanna County from three homeowner locations. In Bradford County,
water samples were collected from 30 domestic wells and two springs.
• Round 2 (April/May 2012 sampling event) - In Bradford County, samples were
collected from 22 domestic wells, one spring, one pond (two samples), and one stream
(two samples).
• Round 3 (May 2013 sampling event) - Some of the locations sampled in Round 1 but
excluded in Round 2 were sampled again.
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Washington County, PA
Sampling locations in Washington County, PA were based primarily on homeowner
concerns/complaints regarding potential impacts to their well water following drilling or
hydraulic fracturing activities in the vicinity of their homes. After evaluating the sites, the EPA
determined that several of the homes within the county would be good candidates for the study.
Several areas in Washington County were targeted for ground water/surface water sampling,
including Amwell, Mount Pleasant, and Hopewell townships. These were divided into two
areas: Northern Area and Southern Area. Hydraulic fracturing activities in these areas are
focused on recovering natural gas from the Marcellus Shale.
In the Northern Area, homeowner complaints alleged recent changes in water quality, including
turbidity, stains, and odors, associated with the drinking water in their homes. In the Southern
Area, homeowner complaints included concerns over the collection/storage of flowback and
other water in an impoundment and cuttings in a reserve pit on a nearby well pad.
The domestic well and surface water samples were collected from the Northern and Southern
case study areas. The following is a summary of each event:
• Round 1 (July 2011 sampling event) - Water samples were collected from thirteen
domestic wells/springs and three surface water locations.
• Round 2 (March 2012 sampling event) - Water samples were collected from 13
domestic wells/springs and two surface water locations.
• Round 3 (May 2013 sampling event) - Water samples were collected from 13 domestic
wells/springs and two surface water locations.
Wise County, TX
Through the stakeholder process, concerns about local drinking water have been reported in three
distinct locations within Wise County, TX. After evaluating the sites, the EPA determined that
several of the homes within the county would be good candidates for the study.
The reported drinking water concerns are clustered in three distinct locations within Wise
County: (1) Location A, approximately 10 miles east of Decatur (2) Location B, approximately
4 miles southwest of Decatur, and (3) Location C, approximately 6 miles northeast of Alvord.
Each area was selected in response to homeowner complaints about changes in water quality
following hydraulic fracturing activities in the vicinity of their homes. The hydraulic fracturing
in this area is focused on recovering natural gas from the Barnett Shale.
• In Location A, homeowner complaints included changes in the smell and taste of the
drinking water in their homes.
• In Location B, homeowner complaints included increased saltiness of drinking water.
• In Location C, homeowner complaints included changes in the smell of the drinking
water in their homes.
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The water samples from domestic wells, industrial wells, and surface water were collected for
analysis from the three locations within the Wise County site. The following is a summary of
each event:
• Round 1 (September 2011 sampling event) - Water samples were collected from four
domestic wells and three surface water locations in Location A; five domestic wells and
one industrial well in Location B; and two domestic wells in Location C.
• Round 2 (March 2012 sampling event) - Water samples were collected from three
domestic wells and three surface water locations in Location A; ten domestic wells and
one industrial well were sampled in Location B; and two domestic wells were sampled in
Location C. EPA was not granted access to one domestic well during the March 2012
sampling event in Location A.
• Round 3 (September 2012 sampling event) - This was a limited sampling event in
which two domestic wells were sampled along with the produced water from an adjacent
gas well in Location B.
• Round 4 (December 2012 sampling event) - Water samples were collected from ten
domestic wells in location B, as well as a pond adjacent to a gas production well and its
abandoned impoundment. The industrial well was not be sampled during this sampling
event due to access not being given by the owner.
• Round 5 (May 2013 sampling event) - Water samples were collected from eight
domestic wells, one surface water location, and two production wells.
Dunn County, (Killdeer), ND
The Killdeer site in Dunn County differs from the other retrospective case studies because the
source of potential contamination to drinking water is known. The EPA determined that the
Dunn County was a good candidate for an investigation because of an accidental release of
hydraulic fracturing fluids and flowback water that occurred during the hydraulic fracturing of a
well. The North Dakota Industrial Commission's Oil and Gas Division and the North Dakota
Department of Health's Division of Water Quality invited EPA to use the City of Killdeer as the
case study location. The hydraulic fracturing in this area is focused on recovering oil from the
Bakken Shale.
In September 2010, a blowout occurred in the Franchuk well when Denbury Resources was
hydraulically fracturing a well in Dunn County, North Dakota. This resulted in an accidental
release of hydraulic fracturing fluids, oil and flowback water, prompting a state action which led
to the installation of monitoring wells, removal of contaminated soil, and installation of a liner.
The release occurred when an inner string of casing burst due to the accidental over
pressurization that occurred during hydraulic fracturing. Two possible pathways for
contamination are being investigated: direct release from the wellbore into the aquifer and
indirect contamination from fluid on the surface infiltrating the aquifer.
Water samples from monitoring wells, domestic wells, supply wells, and municipal wells were
collected for analysis from different locations within the Killdeer site. The following is a
summary of each event:
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• Round 1 (July 2011 Sampling Event) - Water samples were collected from nine
monitoring wells located on the well pad, one municipal water supply well, two water
depot wells, one state observation well, and three domestic wells.
• Round 2 (October 2011 Sampling Event) - Water samples were collected from the
same wells that were sampled in Round 1.
• Round 3 (October 2012 Sampling Event) - Water samples were collected from some of
the same wells that were sampled in Rounds 1 and 2: the nine monitoring wells and the
state observation well.
Next Steps
A large quantity of analytical data has been collected from the five retrospective case studies.
The next major activity for the retrospective case studies will be analysis of these data. Data
evaluation will consist of statistics, comparison with existing data (background, land-use, etc.),
temporal and spatial evaluation, geochemical modeling & evaluation, and environmental record
searches.
References
United States Environmental Protection Agency (EPA) (2011) Plan to Study the Potential
Impacts of Hydraulic Fracturing on Drinking Water Resources. Office of Research and
Development. EPA/600/R-11/122.
United States Environmental Protection Agency (EPA) (2012) Study of the Potential Impacts of
Hydraulic Fracturing on Drinking Water Resources. Progress Report. Office of
Research and Development. December 2012.
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Baseline Water Quality Characterization at Four EPA Retrospective Case Study Areas
Tad Fox1, Andrew Barton1, Alan Tilstone1 and Bernhard Metzger1,
1 Battel 1 e Memorial Institute
The statements made during the workshop do not represent the views or opinions of EPA. The
claims made by participants have not been verified or endorsed by EPA
Introduction
The process of injecting fluids into the subsurface under high pressure to fracture oil and gas
bearing formations and enhance the recovery of hydrocarbons has been in use in the US since
1948. Although early application of hydraulic fracturing were typically on vertical wells with a
single "stage", recent advances in drilling techniques have allowed for deeper exploration and
directional drilling, making recovery of oil and gas from unconventional tight formations
possible through horizontal wells and multiple sequential "stage" completion activities within a
single well.
EPA has initiated five retrospective case studies as part of the Agency's evaluation of the
potential relationship between hydraulic fracturing of unconventional oil and gas formations and
drinking water (USEPA, 2011). The EPA retrospective case studies focus on locations with
claims of possible drinking water impact within proximity to hydraulic fracturing operations and
one location where a casing failure occurred during well stimulation. EPA is investigating the
potential presence and extent of drinking water resource contamination and whether hydraulic
fracturing caused or contributed to the alleged contamination. In addition, the Agency intends
these case studies to provide information to determine the extent to which conclusions on the
impact of hydraulic fracturing can be generalized on local, regional and national scales. EPA has
stated the agency selected the retrospective case study sites to be representative of the types of
concerns that have been reported during stakeholder meetings. The five areas EPA selected are:
•	Marcellus Shale, Washington County, Pennsylvania
•	Barnett Shale, Wise-Denton Counties, Texas
•	Bakken Shale, Dunn County, North Dakota
•	Marcellus Shale, Bradford-Susquehanna Counties, Pennsylvania
•	Raton Basin, Colorado
As part of these retrospective studies, EPA is collecting and analyzing water samples for a wide
range (between 188 and 237 different parameters) of water quality parameters in accordance
with a Quality Assurance Project Plan (QAPP) that EPA has prepared for each case study
location.
The American Petroleum Institute (API) and America's Natural Gas Alliance (ANGA) requested
Battelle to perform initial site characterizations for the retrospective case study areas. Battelle
had previously identified the lack of baseline or background water quality prior to
unconventional resource development as a data gap (Battelle 2012). To address this data gap,
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research on baseline regional water resource quality characteristics was conducted using readily
available historical data to serve as a comparison with the results to be generated by EPA and
industry for each retrospective case study area. Background or baseline water quality is defined
in this study as water quality in a defined area prior to development of unconventional oil and
gas resources through directional drilling and hydraulic fracturing. An initial characterization of
regional baseline water quality conditions has been developed for all but the Raton Basin
retrospective case study area (Battelle 2013). The Raton Basin was not included because a large
body of data and information exists that was not readily accessible within the timeframe of the
Battelle study.
Technical Approach
The primary objectives of the work performed by Battelle for each study area were to
characterize historical water quality of springs, groundwater wells and surface water sources, and
to highlight the potential for adverse impacts that resulted from previous land use activities prior
to the onset of unconventional oil and gas development. The resulting characterization is
intended to assist in evaluating the site specific data collected by EPA's retrospective case study
program, help determine whether these water quality data fall within the observed baseline range
and assist in the identification of other potential sources for consideration in the event of a
detected water quality impact. Battelle accomplished these objectives by:
•	Defining the spatial and temporal boundaries and attributes of each study area.
•	Identifying land use, known potential sources of contamination and water quality data
that could be used to provide historical context for characterizing water resources, along
with identifying associated analytical parameters that could be used to evaluate potential
impact on drinking water resources.
•	Developing a list of available analytes and water quality parameters monitored in the
study area and comparing them to EPA QAPP requirements.
•	Developing and applying quality assurance (QA) criteria to assess the quality of the
historical water quality data.
•	Conducting summary statistical analyses on the water quality data and comparing the
results to relevant state and federal water quality screening criteria. (A value above water
quality criteria may simply reflect natural conditions and was not interpreted as indicative
of an impact. In order to assess whether an impact occurred, or corrective action is
suggested, a thorough investigation would have to be performed which is beyond the
scope of this desktop study.)
Battelle utilized EPA's data quality objective (DQO) process to help ensure that an appropriate
type and quantity of pre-existing data needed to meet the primary objective were collected (EPA,
2006). For the purpose of this study, a minimum of eight unique sample locations were required
to constitute a representative sample for a specific parameter. Water quality data sources
included the United States Geologic Survey (USGS) (i.e., National Uranium Resource
Evaluation [NURE], National Water Information System [NWIS]), state agencies, and EPA
STOrage and RETrieval Data Warehouse. (STORET)
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The parameters available for incorporation into the Battelle water-quality databases are limited
primarily to general inorganic water quality parameters, major ions, metals and nutrients. For
many of the other parameters on the EPA retrospective case study analytical list (e.g., organic
parameters) there are insufficient available data to adequately characterize baseline water quality
and permit statistical comparisons against site specific data as indicated in Table 1. Methane is
commonly detected in the environment (COGCC, 2003; Molofsky et al., 2011; EPA 2012;
Weston 2012), although pre-oil and gas development data for methane were not available from
the data sources used by Battelle to develop the baseline water quality characteristics.
Table 1. Number of parameters included in EPA study and number of parameters in groundwater,
spring and surface water with results from at least eight locations for each retrospective study area
Location
Date1
No. of EPA
Parameters
Baseline
Groundwater
Parameters
Baseline
Spring
Parameters
Baseline
Surface Water
Parameters
Washington County, PA
2005
196
29
11
21
Bradford/Susquehanna
Counties, PA
2007
192
29
11
23
Wise and Denton Counties, TX
1998
188
712
0
24
Dunn County, ND
2005
237
27
16
28
1 Cut off date for data inclusion (for example, data prior to 2005 were included for Washington County, PA)
includes 28 organic and 2 inorganic constituents where all results were non-detect.
Because water quality data from the EPA STOrage and RETrieval Data Warehouse (STORET)
database is associated with environmental impact monitoring that could potentially skew
baseline water quality results, separate evaluations were performed using the complete water
quality dataset and a dataset excluding the EPA STORET data.
Results
Water quality data were evaluated by Battelle for the timeframe prior to unconventional oil and
gas development via directional drilling and hydraulic fracturing. The water quality data
acquired provide an observed range in parameter concentrations prior to the onset of
unconventional oil and gas development in each study area.
Sampling locations where groundwater and surface water quality parameters in the database
were found to be higher than applicable federal and state water quality standards, criteria and
guidance values are shown in Figures 1 through 4. At many sampling locations, the available
data indicate pre-unconventional oil and gas development water quality does not meet federal
and state water quality standards, criteria or guidance values for several inorganic parameters
including pH, total dissolved solids (TDS), chloride, fluoride, sulfate, aluminum, arsenic,
barium, beryllium, boron, cobalt, copper, nickel, chromium, manganese, mercury, iron, lead,
nitrate, phosphorus, sodium, strontium, turbidity, uranium, vanadium and zinc among others.
Insufficient data are available on organic chemical constituents to allow comparison with federal
and state water-quality standards.
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EPA's Study of the Potential Impacts of Hydraulic Fracturing on Drinking Water Resources:
Summary of July 30, 2013, Technical Workshop on Case Studies to Assess Potential Impacts of Hydraulic Fracturing
on Drinking Water Resources
As reflected in the information acquired by Battelle, natural variability (e.g., spatial and temporal
changes and aquifer composition), land use patterns and other anthropogenic factors can affect
water quality. Historical activities such as agriculture, mining, steel production, manufacturing,
conventional oil and gas extraction, urban runoff, road salts and sewer overflows are known to
have impaired streams, rivers and groundwater in many cases. All know potential sources of
contamination should be considered as part of the evaluation of data from retrospective case
study areas. An array of government programs are in place to regulate oil and gas extraction
industrial activities and protect the environment. No instances of adverse impact to water
resources caused by injecting hydraulic fracturing fluids into the subsurface have been
documented in two recent studies in Pennsylvania and Texas (GWPC, 2011; MSAC, 2011).
Each detailed report characterizes conditions based upon readily available information on land
use, known surface water impairments and water quality data from the USGS, EPA, state and
local sources. The regional characterization can be used to compare EPA or industry-obtained
water quality data at each retrospective case study location.
Conclusions
The initial baseline water quality characterization developed for this study provides a summary
of the range and distribution of results for a number of general water quality and inorganic
parameters at each study area. This information permits comparison of more recent data
collected by EPA and industry within the context of observed water quality prior to
unconventional oil and gas resource development. Conclusively determining whether a
relationship exists between hydraulic fracturing and drinking water resources will be challenging
given the large number of sampling locations in each region where baseline water quality does
not meet federal and state water quality standards, criteria or guidance values for some inorganic
parameters, and the lack of organic chemical data to characterize background water quality
conditions. However, the available area specific historical water-quality data, land use
information, and the application of sound hydrogeochemical principles can and should be used to
inform EPA's research. Observations of impaired water quality would require rigorous scientific,
site-specific analysis to differentiate impacts from pre-existing conditions and impacts due to
other potential sources of contamination, including activities associated with hydraulic fracturing
operations.
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EPA's Study of the Potential Impacts of Hydraulic Fracturing on Drinking Water Resources:
Summary of July 30, 2013, Technical Workshop on Case Studies to Assess Potential Impacts of Hydraulic Fracturing on Drinking Water Resources

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A-14

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-------
EPA's Study of the Potential Impacts of Hydraulic Fracturing on Drinking Water Resources:
Summary of July 30, 2013, Technical Workshop on Case Studies to Assess Potential Impacts of Hydraulic Fracturing on Drinking Water Resources
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-------
EPA's Study of the Potential Impacts of Hydraulic Fracturing on Drinking Water Resources:
Summary of July 30, 2013, Technical Workshop on Case Studies to Assess Potential Impacts of Hydraulic Fracturing on Drinking Water Resources

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A-17
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EPA's Study of the Potential Impacts of Hydraulic Fracturing on Drinking Water Resources:
Summary of July 30, 2013, Technical Workshop on Case Studies to Assess Potential Impacts of Hydraulic Fracturing
on Drinking Water Resources
Acknowledgements
API and ANGA provided funding to conduct the project. Various industry representatives from
each case study area contributed insights on the process of hydraulic fracturing, draft manuscript
reviews, and thoughtful comments and suggestions. Pennsylvania Department of Environmental
Protection, Texas Rail Road Commission and North Dakota Industrial Commission provided
access to pertinent information relative to each case study area. The project was conducted
through the dedicated work of a multidisciplinary team of scientists and engineers at Battelle.
References
Battelle 2012. Review of EPA Hydraulic Fracturing Study Plan. Available at:
http://www.api.org/news-and-media/news/newsitems/2012/iul-
2012/~/media/Files/Policv/Hydraulic Fracturing/Battelle-Studies/Battelle-EPA-studv-plan-
review-071012.ashx
Battelle 2013. Site Characterization Reports for Four Study Areas; Available at:
http://www.api.org/policv-and-issues/policv-items/hf/comments-api-anga-to-epa
Colorado Oil and Gas Conservation Commission (COGCC). 2003. COGCC Raton Basin
Baseline Study Staff Report Rep., Colorado Oil and Gas Conservation Commission.
EPA 2012. Study of the Potential Impacts of Hydraulic Fracturing on Drinking Water Resources:
Progress Report. Available at:
http://www2.epa.gov/hfstudy/study-potential-impacts-hydraulic-fracturing-drinking-water-
resources-progress-report-0
Groundwater Protection Council (GWPC). 2011. State Oil and Gas Agency Groundwater
Investigations and Their Role in Advancing Regulatory Reforms A Two-State Review: Ohio
and Texas. Available at:
http://fracfocus.org/sites/default/files/publications/state_oil gas_agency_groundwater_inves
tigations_optimized.pdf
Marcellus Shale Advisory Commission (MSAC). 2011. Governor's Marcellus Shale Advisory
Commission Report. July 22, 2011.
Molofsky, L.J., J.A. Connor, S.K. Farhat, A.S. Wylie, and T. Wagner, 2011. "Methane In
Pennsylvania Water Wells Unrelated To Marcellus Shale Fracturing", Oil & Gas Journal,
December 5.
United States Environmental Protection Agency (EPA). 2011. "Plan to Study the Potential
Impacts of Hydraulic Fracturing on Drinking Water Resources," EPA/600/R-11/122,
November.
Weston Solutions, Inc. (Weston). 2012. Evaluation of Geology and Water Well Data Associated with the
EPA Hydraulic Fracturing Retrospective Case Study, Bradford County, Pennsylvania. Prepared for
Chesapeake Energy, Oklahoma City, Oklahoma. April.
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EPA's Study of the Potential Impacts of Hydraulic Fracturing on Drinking Water Resources:
Summary of July 30, 2013, Technical Workshop on Case Studies to Assess Potential Impacts of Hydraulic Fracturing
on Drinking Water Resources
Evaluation of Water Quality Monitoring Programs and Statistical Analysis Tools to be
Utilized in Shale Development
Uni Blake
Hometown Energy Group, Oneonta, NY
The statements made during the workshop do not represent the views or opinions of EPA.
The claims made by participants have not been verified or endorsed by EPA.
Groundwater monitoring around natural gas development sites is a complex task. There are
statistically significant natural spatial variations in the hydrogeology of domestic wells. This
presents difficulties when creating a pooled background database for inter well analysis. Current
industry water quality baseline strategies involve collecting one pre-sampling data point per
domestic well before development starts. Post drilling/HVHF sampling for comparison is
routinely optional and is only conducted at the request of a private well owner or if a problem in
water quality is suspected. It is assumed that the baseline sample is representative of the general
water quality. However, there is growing concern that more and more domestic water supplies
are presenting existing contamination. It is anticipated that by modifying the water sampling
protocols to include a trend monitoring program, prior contamination or trends can be identified.
One-sample point baselines;
• Cannot determine prior contamination or distinguish trends associated with prior
contamination.
• Present insufficient data for statistical analysis.
• Do not take into account,
o Variability in parameters (Coleman, 2012)
o Long-term changes that may occur (surface spills, seeps, blowouts)
A literature review of strategies utilized to monitor surface and groundwater resources was
conducted. Also reviewed were various state and federal guidance documents related to
statistical applications for groundwater monitoring. Current natural gas baseline monitoring
practices were examined and the best strategies to analyze and assess data were selected.
Summary of a Shale Water Quality Trends Monitoring Program
The program should contain all the elements of a well-designed Monitoring Program designed to
fit within the goals of the Clean Water Act. The program should include the following elements:
• Data Objectives: Generate water quality monitoring data that can be analyzed to represent
the water quality before, during and after shale gas development. Potential changes
targeted include short term (abrupt changes) and/or long-term changes.
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EPA's Study of the Potential Impacts of Hydraulic Fracturing on Drinking Water Resources:
Summary of July 30, 2013, Technical Workshop on Case Studies to Assess Potential Impacts of Hydraulic Fracturing
on Drinking Water Resources
• Monitoring Plan Design: The time-frame and the number of samples collected should be
adequate to protect human health standards and to also to identify trends if any.
• Data Collection: Utilize consistent methods to minimize assumptions (QAPP/QMP) to
create data that is representative and legally defensible.
• Data Management: Date should be stored properly and easily accessible.
• Data Assessment: Utilize easily understood and commonly used statistical methods.
Conclusion
It is recommended that the trend monitoring sampling should be conducted at one or two
groundwater wells and one surface water location that are hydrogeologically downstream from
the well pad. This trend monitoring program should augment and not replace the regular baseline
monitoring program. Background data from multiple-wells should not be pooled for the trend
analysis; instead, assessments should be focused on targeted intra-well analysis.
The program should include the following considerations:
• Suggested sampling time frame should consist of two years of data collected monthly
prior to shale activities (before) and 2 years after activities commence (after). This four-
year database, if collected consistently, can be utilized in trend analysis (Hirsch, 1982).
• Since most water quality data is non-parametric, it is recommended that the statistical
methods that can be utilized to monitor for trends include Theil-sen slope or the Mann-
Kendall Test, the seasonal Kendall test or the Wilcoxon-Mann-Whitney Step Trend.
• The program should also take into consideration the added cost burden and the attached
inconvenience to the landowner that goes with the multiple sampling events.
References
Hirsch R.M., J.R. Slack and R.A. Smith, 1982. Techniques of Trend Analysis for Monthly Water
Quality Data. Water Resources Research, Vol. 18(1) pp. 107-121 February.
Coleman, Nancy P., and Debby McElreath. "Short-term Intra-Well Variability in Methane
Concentrations from Domestic Well Waters in Northeastern Pennsylvania." (April 2011)
Hirsch R.M., R.B. Alexander, and R.A. Smith 1991. Selection of Methods for the Detection and
Estimation of Trends in Water Quality. Water Resources Research, Vol. 27(5), pp. 803-
813 May.
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EPA's Study of the Potential Impacts of Hydraulic Fracturing on Drinking Water Resources:
Summary of July 30, 2013, Technical Workshop on Case Studies to Assess Potential Impacts of Hydraulic Fracturing
on Drinking Water Resources
Surface Water and Stray Gas Shallow Aquifer Contamination
Avner Vengosh*, Robert B. Jackson, Nathaniel Warner, Thomas H. Darrah
Nicholas School of the Environment, Duke University
(*vengosh@duke.edu)
Exploration of unconventional natural gas reservoirs such as low-permeability organic shale
formations through horizontal drilling and hydraulic fracturing has changed the energy landscape
in the Unites States, providing a vast new energy source. Since the mid-2000s, drilling and
production of natural gas has accelerated, also triggering a public debate over the safety and
environmental impacts of these operations (1). Here we review the potential short- and long-term
risks to the quality water resources associated with shale gas development.
We highlight two key issues related to shorter-term risks. The first is stray gas contamination -
the occurrence of elevated levels of methane and other gases in some shallow drinking water
wells, which can pose a potential flammability or explosion hazard to homes near shale gas
drilling sites. Evidence for stray gas contamination has been suggested in northeastern
Pennsylvania overlying the Marcellus Shale (2-4). In these areas, elevated methane levels in
shallow groundwater less than 1 km from shale gas wells were characterized by a thermogenic
carbon isotope fingerprint, distinctive hydrocarbon ratios with presence of ethane, and noble gas
geochemical fingerprints (2-4). Combined, these studies suggest stray gas contamination results
from the leaking of natural gas along the well annulus from the shale production formations or
shallower formations and/or the release of natural gas from the target formation through poorly
constructed or failing well casings. In contrast, shallow groundwater associated with the
Fayetteville Shale in north-central Arkansas showed no evidence for methane contamination
(5,6), indicating that the local geology and/or drilling practices may play a role in stray gas
contamination.
The second short-term risk is the disposal and/or accidental release (spill) of the flowback and
produced waters that are generated during well completion, hydraulic fracturing, and gas
production from unconventional wells (7,8). Shale gas wastewater is often highly saline and
toxic and can contain high levels of naturally occurring radioactivity (8-13). In spite of treatment,
discharge of shale gas wastewater to surface waters causes direct contamination of the river
systems (12-14). The magnitude of contamination depends on the volume of the disposed
wastewater and the local hydrological system (i.e., flow rate and dilution). Disposal of treated
wastewater originated from shale gas can also generate bromide levels above baseline levels (13)
that can trigger formation of brominated trihalomethanes compounds (e.g.,
bromodichloromethane) in downstream drinking waters upon water chlorination (15).
As for long-term risks, we have identified four key issues. The first is potential water shortage in
areas where water scarcity induces competition over limited or diminishing water availability. In
spite of the overall low volume of water that is needed for drilling and hydraulic fracturing
relative to other water utilization (16), large-scale unconventional development in water-scare
areas such as the Eagle Ford play in Texas could require additional groundwater exploitation and
depletion of aquifers that are being utilized for agricultural and domestic uses. Over-exploitation
of these aquifers is often associated with water quality deterioration.
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EPA's Study of the Potential Impacts of Hydraulic Fracturing on Drinking Water Resources:
Summary of July 30, 2013, Technical Workshop on Case Studies to Assess Potential Impacts of Hydraulic Fracturing
on Drinking Water Resources
The second risk is the potential for natural pathways and hydraulic connection between deep
underlying formations and shallow drinking water aquifers, such as faults and/or the natural
fracture network, in which pressurized gas and brine can flow to shallow aquifers (17). In spite
of thick geological barriers between shallow and deep formations, evidence for possible
pathways has been shown in the northeastern Appalachian Basin where shallow groundwater had
high salinity combined with geochemical and isotopic fingerprints similar to waters produced
from the Marcellus formation during drilling and production (18).
The third risk is the accumulation of residual contaminants in areas of oil and gas wastewater
disposal, spills, and leaks. Field evidence shows that long-term disposal of treated wastewater
originating from shale gas production can cause reactive radioactive elements (radium and
daughter isotopes) to accumulate in the river sediments downstream of disposal sites (13).
Likewise, treatment of shale gas wastewater generates solid waste with potentially high levels of
radioactivity (13). Improper disposal of these solid wastes to unregulated landfills could in some
cases contaminate associated water resources.
1. Howarth R.W., Santoro R., Ingraffea A. (2011) Methane and the greenhouse-gas footprint of natural gas from
shale formations. Climatic Change; 106: 679-690.
2. Osborn S.G., Vengosh A., Warner N.R., Jackson R.B. (2011) Methane contamination of drinking water
accompanying gas-well drilling and hydraulic fracturing. PNAS; 108: 8172-8176.
3. Darrah, T, Vengosh A, Jackson RB, Warner N. (2012) Constraining the source and migration of natural gas in
shallow aquifers within active shale gas production zone: insights from integrating noble gas and hydrocarbon
isotope geochemistry. GSA meeting, Charlotte, NC.
4. Jackson, R.B., Vengosh, A., Darrah, T.H., Warner, N.R., Down, A., Poreda, R.J., Osborn, S.G., Zhao, K., and
Karr, J.D. (2013) Increased stray gas abundance in a subset of drinking water wells near Marcellus shale gas
extraction. PNAS (in press, June, 2013).
5. Kresse, T.M., Warner, N.R., Hays, P.D., Down, A., Vengosh, A., and Jackson, R.B., 2012, Shallow groundwater
quality and geochemistry in the Fayetteville Shale gas-production area, north-central Arkansas, 2011: USGS
Scientific Investigations Report 2012-5273, 31 p.
6. Warner N.R., Kresse, T.M., Hays, P.D., Down, A., Karr, J.D., Jackson, R.B., Vengosh, A. (2013) Goechemical
and isotopic variations in shallow groundwater in areas of Fayetteville Shale development, north central Arkansas.
Applied Geochemistry (http://dx.doi.Org/10.1016/i.apgeochem.2013.04.013).
7. Maloney, K.O. and Yoxtheimer, D. A. (2012) Production and Disposal of Waste Materials from Gas and Oil
Extraction from the Marcellus Shale Play in Pennsylvania. Environ. Pract. 14, 278 (2012). doi:
10.1017/S146604661200035X7. Lutz, B.D., Lewis, A.N., Doyle, M. W. (2013) Generation, transport, and disposal
of wastewater associated with Marcellus Shale gas development. Water Resour. Res. 49, 647 (2013). doi:
10.1002/wrcr.20096.
8. Haluszczak L.O., Rose R.W., Kump L.R. (2013) Geochemical evaluation of flowback brine from Marcellus gas
wells in Pennsylvania, USA. App Geoch., 28, 55-61.
9. Rowan, E., Engle, M., Kirby, C., Kraemer, T. (2011) Radium content of oil- and gas-field produced waters in the
northern Appalachian Basin (USA)—Summary and discussion of data. U.S. Geological Survey Scientific
Investigations Report 2011; 513: 31 pp.
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EPA's Study of the Potential Impacts of Hydraulic Fracturing on Drinking Water Resources:
Summary of July 30, 2013, Technical Workshop on Case Studies to Assess Potential Impacts of Hydraulic Fracturing
on Drinking Water Resources
10. Entrekin, S. Evans-White, M., Johnson, B., Hagenbuch, E. (2011) Rapid expansion of natural gas development
poses athreatto surface waters. Front. Ecol. Environ. 9, 503 doi: 10.1890/110053.
11. Barbot, E., Vidic, N.S., Gregory, K.B., Vidic, R. D. (2013) Spatial and temporal correlation of water quality
parameters of produced waters from Devonian-Age shale following Hydraulic Fracturing. ES&T. 47, 2562 (2013).
12.Ferrar, K. J., Michanowicz, D. R., Christen, C. L., Mulcahy, N., Malone, S. L., Sharma, R. K., (2013)
Assessments of effluent contaminants from three wastewater treatment plants discharging Marcellus Shale
wastewater to surface waters in Pennsylvania. ES&T, 47, (7), 3472-3481.
13. Warner, N.R. (2013) Tracing hydraulic fracturing fluids and formation brines using boron, radium, and
strontium isotopes. PhD Thesis, Duke University, Durham, NC.
14. Olmstead, S.M. , Muehlenbachs, L.A. Shih, J.-S., Chu, Z., Krupnick, A. J. (2013) Shale gas development impacts
on surface water quality in Pennsylvania. PNAS, doi: 10.1073/pnas. 1213871110
15. Wilson, J.M., and VanBriesen, J.M. (2012) Oil and gas produced water management
effects on surface drinking water sources in Pennsylvania. Environmental Practice, 14, 1-13.
16. Nicot, J.P. and Scanlon, B.R. (2012). Water Use for Shale-Gas Production in Texas, U.S. ES&T, 46, 3580-3586.
17. Myers, T. (2012) Potential contaminant pathways from hydraulically fractured shale to aquifers. Ground Water
50, 872.
18. Warner, N.R., Jackson, R.B., Darrah, T.H., Osborn, S.G., Down, A., Zhao, K., White, A. Vengosh, A. (2012).
Geochemical evidence for possible natural migration of Marcellus formation brine to shallow aquifers in
Pennsylvania. PNAS., doi: 10.1073/pnas.1121181109.
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EPA's Study of the Potential Impacts of Hydraulic Fracturing on Drinking Water Resources:
Summary of July 30, 2013, Technical Workshop on Case Studies to Assess Potential Impacts of Hydraulic Fracturing
on Drinking Water Resources
Designing a Hydraulic Fracturing Case Study
Gene Florentino
George Lukert
Ecology and Environment, Inc.
The statements made during the workshop do not represent the views or opinions of the EPA.
The claims made by participants have not been verified or endorsed by the EPA.
1. Introduction and Purpose
In an effort to aid in developing a documented, consistent, rigorous approach for evaluating
retrospective case study data for causal assessment, a Decision Support System (DSS) has been
developed. The decision support system is outlined in Figures 1 and 2 and provides a tiered
approach to analyzing retrospective sites. This approach documents the entire retrospective case
study process, including site characterization, data collection, data evaluation, identification of
potential sources, determination of the strength of evidence, determination of additional
information needed for causal assessment, identification/evaluation of probable cause(s),
sufficient confidence, and criteria used for each step in the causal assessment process. The DSS
provides the tools to document the steps taken to evaluate causal links and the level of
confidence in the causal links.
The following is a summary of each step of the process.
Purpose of Study
After defining the purpose of the study by identifying the site conditions; the reported
problem(s)/issues(s) that warrant the study; the series of events that led to the impairment; and
the potential impact(s) on human health and the environment from the site activity, the following
steps can be used as a guide during the evaluation process.
2. DSS Tier 1 Steps
Candidate Causes
A candidate cause can be defined as a hypothesized cause of an environmental impairment that is
sufficiently credible to be analyzed (EPA 2000). For the purpose of this study, candidate causes
include all potential sources that could stress the environment and, therefore, contribute to
surface or groundwater contamination.
Once an exhaustive list of candidate causes is developed, each potential cause is evaluated by
examining the relationship between the cause and the observed effects. This process is facilitated
by developing a preliminary conceptual site model (CSM). The CSM uses a map of the site's
physical features and underlying stratigraphy and hydrologic properties to identify possible loca-
tions of sources and potential pathways between these sources and the observed impacts. For this
study, potential candidate causes include: industrial/commercial use; historical land use; current
drilling processes/practices; historical drilling practices; and naturally occurring sources.
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EPA's Study of the Potential Impacts of Hydraulic Fracturing on Drinking Water Resources:
Summary of July 30, 2013, Technical Workshop on Case Studies to Assess Potential Impacts of Hydraulic Fracturing
on Drinking Water Resources
Existing Data Collection
After a list of candidate causes is completed for potential sources, existing data are compiled in
an effort to infer causality and eliminate candidate causes that are not related to the potential
sources.
Existing data may be found in studies conducted to date, including federal and state studies, and
stakeholder studies. These studies can be found by performing a detailed background assessment
(see Figure 2).
Some data related to the hydraulic fracturing water cycle has already been compiled and
reviewed and may include the following:
• Chemicals and practices used by existing producers in the hydraulic fracturing
process.
• Chemicals and water use for hydraulic fracturing from the FracFocus database.
• Well construction and hydraulic fracturing records provided by well operators to
assess the effectiveness of current well construction practices at containing gases and
liquids before, during, and after hydraulic fracturing.
• Causes and volumes of spills of hydraulic fracturing fluids and wastewater from state
spill databases in Colorado, New Mexico, and Pennsylvania, and from the National
Response Center database.
• Scientific literature relevant to the research questions posed for retrospective studies
of potential impacts of hydraulic fracturing (EPA 2012). A Federal Register notice
was published on November 9, 2012, requesting relevant, peer-reviewed data and
published reports, including information on advances in industry practices and
technologies. This body of literature will be synthesized with results from the other
research projects to create a report of results.
Evaluation of Data
Analyze Evidence
The existing information is analyzed to determine if the data are related to one or more of the
candidate causes. It is expected that most existing information about a site and the candidate
causes may be useful for inferring causality and determining impacts. However, data quality
objectives (DQOs) should be established to evaluate the data usability.
Data Usability
Potentially useful data should be used to prepare the preliminary Conceptual Site Model (CSM)
for each study area and may include information on the hydrology and geology; operator data;
information on the sampling and analysis methods; and information on site history. Actual
measurement data from the site are needed as evidence of association between potential causes
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EPA's Study of the Potential Impacts of Hydraulic Fracturing on Drinking Water Resources:
Summary of July 30, 2013, Technical Workshop on Case Studies to Assess Potential Impacts of Hydraulic Fracturing
on Drinking Water Resources
and known impacts. Data should be organized or analyzed in terms of associations that support
or refute the potential causes by addressing the nature and extent of potential contamination and
contaminant fate and transport.
The DQO process is a component of systematic planning for the project designed to generate
performance acceptance criteria for the collection of new data. The process is a series of steps
from problem statement through the data collection design. The DQO process is discussed as
part of the development of Quality Assurance Project Plans (QAPP). Analysis of existing data
and information is incorporated into the DQO process and can help identify data gaps.
A wide variety of data may be collected about the candidate causes and environmental
impairment. The usability of data collected are assessed against acceptance and performance
criteria often specified in terms of precision, accuracy, representativeness, completeness, and
comparability (PARCC) parameters. Numerical acceptance criteria cannot be assigned to all
PARCC parameters, but general performance goals can be established for most data collection
activities.
3. DSS Tier 2 Steps
Screening of Potential Causes
This step is a preliminary screening (based on the evaluation of existing data) that determines
whether a candidate cause can be linked with the effect. The preliminary CSM will aid in estab-
lishing the link between the candidate causes and the effect. For this step, a candidate cause will
be evaluated and a determination will be made to eliminate the candidate cause or to retain the
candidate cause of a potential contributor to the identified contamination. Factors to be
considered include the following:
• Are the candidate cause and the observed impact consistent temporally and spatially?
• Is the impact observed if the cause is not present or is the cause present if the impact
is not observed?
• Does the intensity of the impact increase or decrease proportional to the evaluation of
individual candidate causes?
If direct measurement data are not available for the site, then data from similar sites could be
used as evidence to retain a potential cause. In addition, intermediate pathways can be examined
to infer an association between a candidate cause and an observed impact based on the known
physical, hydrological, or chemical characteristics.
Conduct Initial Sampling
If no site-specific measurement data are available, a limited initial sampling is performed at ex-
isting wells, taps, surface water bodies, or surrounding surface soils. Some of this measurement
data is needed to develop the CSM and perform the initial causal analysis. Existing data can be
used to determine the measurement parameters. At the initial sampling, simple measurement
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parameters, such as pH, conductivity, and turbidity, can be used as indicators of potential cause
and effect associations. The initial sampling is designed to support planning for more detailed
investigations.
Issues Associated with Designing and Conducting Field Investigations
One of the main factors in designing a monitoring well network is determining the optimal
location of monitoring wells to capture potential methane migration and/or hydraulic fracturing
fluid migration. These challenges include determining the proper distance from the production
well. If the monitoring wells are too far away from the production well, the travel times for
hydraulic fracturing fluid migration may be too great for the wells to be effective. If the
monitoring wells are too close to the production well (e.g., on the well pad), the wells may
become direct conduits for surface contamination (spills) to the underlying aquifers, or they may
be damaged by the drilling process (struck by the production well bit). Production well air rotary
drilling methods may also impact monitoring well water quality. Another challenge is that the
screens could be grout contaminated when the production well surface casing is installed. Other
challenges include design and installation of angled monitoring wells or horizontal monitoring
wells as an alternative to monitoring the freshwater zone immediately adjacent to or beneath the
production well pad without drilling the monitoring well through the pad. Drilling monitoring
wells through the well pad is viewed as unacceptable by some operators. Lastly, there is peer
review and public perception that should be considered in the study design. While it may not
make technical sense to drill monitoring wells along the production well lateral (which could be
over a mile long), it cannot be ignored, since there is a possibility of upward methane migration
or hydraulic fracturing fluid migration along natural fractures. Other issues and concerns include
influence by other nearby oil and gas drilling, whether it be historical or recent, or near future
proposed drilling; site access (reaching agreements with land owners to allow the installation of
monitoring wells that are critical to the study); and insurance requirements (operators see the
installation of nearby monitoring wells as high risk because of the potential for creating
downward migration pathways of contaminants to freshwater aquifers), therefore, liability
insurance requirements may impact the solicitation of consultants and subcontractors to
implement the study.
Data Evaluation
This step is used to evaluate the quality of the initial sampling data, which would include data
validation and other quality assurance/quality control (QA/QC) procedures (e.g., sample collec-
tion methods). Additionally, the strength of the data collected must be evaluated relative to po-
tential causes. For example, a detection of methane does not necessarily indicate methane con-
tamination from a particular source or activity. However, isotopic analysis may provide insight
into the methane signature as to whether it is biogenic or thermogenic, with the latter possibly
being associated with drilling activities or with particular target formations. Sampling data must
also be compared against natural or background conditions as much as possible in order to iden-
tify anomalies possibly associated with suspected source areas.
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Initial Causal Analysis
After available evidence and initial sampling has been compiled and evaluated, the cause(s) of
the impact may be obvious. In other cases, a more detailed analysis is needed to reach a conclu-
sion or determine if sufficient data are available for decision making. The methods listed below
can be used to develop a clear logical association between the candidate causes and the impacts
and to weigh the strength of evidence supporting each candidate cause.
Develop the Conceptual Site Model
The CSM is developed and refined throughout the investigative process to identify sources, re-
ceptors, and pathways associated with the site. The CSM is an important part of the analysis of
evidence from candidate causes because it identifies links between sources and potential impacts
by representing the physical, chemical, and biological processes that control the transport, migra-
tion, and potential impacts of potential sources on receptors. A CSM identifies the potential
sources of contamination; shows how chemicals at the original point of release might move in
the environment; identifies the different types of receptors/human populations; and lists the
potential exposure pathways.
Implement Groundwater Model
An initial groundwater model must be established to assess the potential for source contaminants
to reach potential receptors. Groundwater data, such as depth to aquifer, regional groundwater
flow direction and gradient, aquifer materials and formations, and screened intervals for potential
groundwater receptors are needed. This information can be obtained from agency studies and
existing data collected as part of Tier 1.
Assess the Nature and Extent of Contamination
The nature and extent of contamination can be evaluated using existing data and the CSM to look
for evidence of contamination along potential pathways or at receptors. The data can be used to
evaluate the association between the potential causes and observed effects.
Assess Fate and Transport
In order to establish potential causes of contamination there must be a viable pathway from the
source to receptor. Assessing the fate and transport mechanisms at a site uses scientific evidence
of physical, chemical, and biological processes to evaluate whether contamination can originate
from a potential cause.
Identification of Data Gaps
Once potential causes have been screened and/or eliminated during review of existing data, ac-
quiring and assessing additional data is the next step. Typically, sufficient data or evidence will
not be available to determine a probable causal candidate. As a result, site-specific studies will
likely have to be conducted in order to fill in data gaps. Typical data gaps may include, but are
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not limited to, site-specific geology and hydrogeologic data, groundwater sampling analysis,
historical information, drilling and well completion records, and personal interviews.
4. DSS Tier 3 Steps
Execute Site-Specific Studies
The list of candidate causes can be pared down after screening is completed. Based on the need
for additional data and/or the strength of existing data for the remaining candidate causes, a par-
tial or one or more site-specific studies would be necessary to fill in the data gaps and produce
valid evidence. Types of site-specific studies include geological assessment, hydrological as-
sessment, and surface impact assessment (see Figure 2).
Re-evaluation of Data
After data gaps have been completed through additional database searches and site-specific stud-
ies, the study tools (CSM; groundwater model; nature and extent; and fate and transport) should
be updated. Candidate causes can then be re-evaluated to determine which should be eliminated
from further consideration. If the data is not sufficient, additional site studies should be com-
pleted and along with another re-evaluation step. If there is sufficient data, the probable candi-
date causes are then identified and designated as principle cause(s) or secondary cause(s).
5. DSS Tier 4 Steps
Probable Candidate Causes
Once sufficient data are obtained, probable candidate causes should be determined and designat-
ed as a principle cause(s) or a secondary cause(s). A principle cause is a cause that makes the
largest contribution to the effect. A secondary cause is a cause that makes some contribution to
the effect but on a smaller scale than a principal cause.
QA Evaluation
All research projects that generate or use environmental data to make conclusions or rec-
ommendations must comply with the appropriate QA program requirements. The QA program
requirements include developing a QAPP and peer review. The final QA evaluation should
verify that the study and decisions or recommendations resulting from the study were completed
under an acceptable QA program. Activities include verification that a QAPP was implemented;
data quality audits were conducted; work products were subject to peer review; and that the QA
procedures were documented in the final reports. If the QA process was properly implemented,
conclusions that determine principle and secondary cause(s) are valid and can be released to
policy makers and stakeholders.
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Conclusions
Final identification of probable candidate causes may not identify a single principle cause, thus
multiple principle causes and secondary causes may be responsible for the impairment identified
at each case study area. The magnitude of the studies necessary to determine the principle
cause(s) of the impairment may be technically impracticable, and thus beyond the scope of this
study.
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Figure 1. Decision Support System Flow Chart
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Determine Appropriate Assessments) Based on Data Needs
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References
United States Environmental Protection Agency (EPA). 2012. Study of the Potential Impacts of
Hydraulic Fracturing on Drinking Water Resources. Progress Report. Office of
Research and Development.
2000. Stressor Identification Guidance Document. Office of Water. Office of Research
and Development. National Exposure Research Laboratory.
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on Drinking Water Resources
Appendix B.
Extended Abstracts from Session 2:
Prospective Case Studies
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Overview of EPA's Approach to Developing Prospective Case Studies
Technical Workshop: Case Studies to Assess Potential Impacts of Hydraulic Fracturing on
Drinking Water Resources
Robert Ford and Jeanne Briskin
United States Environmental Protection Agency
Office of Research and Development
July 30, 2013
Information presented in this abstract is part of the EPA's ongoing study. EPA intends to use
this, combined with other information, to inform its assessment of the potential impacts to
drinking water resources from hydraulic fracturing. Mention of trade names or commercial
products does not constitute endorsement or recommendation for use.
Introduction
One component of the United States Environmental Protection Agency's (EPA) study of the
potential impacts of hydraulic fracturing on drinking water resources is prospective case studies,
the purpose of which is to more fully understand and assess if and how site specific hydraulic
fracturing practices may impact drinking water resources.6 The retrospective case studies,
addressed in a separate EPA presentation for this workshop, focus on investigating and assessing
reported instances of drinking water contamination in areas where hydraulic fracturing activities
have already occurred. The prospective case studies are designed to be forward looking and
allow for the collaborative design and development of a research program that will include
sampling and characterization of the site before, during and after drilling, injection of the
fracturing fluid, flowback and production.
Prospective Case Study Goals
Prospective case studies are being designed to contribute to the information base that will allow
stakeholders, including other federal partners, States, Congress, industry and the public to better
understand hydraulic fracturing, its importance to our nation's energy policies, and factors that
may correlate with the conduct of hydraulic fracturing in a manner that protects human health
and the environment. Along with other relevant work, these case studies will allow EPA and
others to evaluate any changes in water quality over time and will focus on understanding how
site specific hydraulic fracturing practices prevent impacts to drinking water resources. Of the
five fundamental questions to be addressed, which are linked to the hydraulic fracturing water
lifecycle, the three most applicable to the prospective case studies are:
1. Chemical Mixing: What are the possible impacts of surface spills on or near well pads of
hydraulic fracturing fluids on drinking water resources?
2. Well Injection: What are the possible impacts of the injection and fracturing process on
drinking water resources?
3. Flowback and Produced Waters: What are the possible impacts of surface spills on or
near well pads of flowback and produced water on drinking water resources?
6 EPA, The Potential Impacts of Hydraulic Fracturing on Drinking Water Resources: Progress Report (December
2012)
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Study Approach
EPA plans to use the study approach described below, which follows the development phases of
a production well (Figure 1).
Figure 1: Development Phases of a Production Well
Site Selection: includes considering such factors as proximity to water resources, current ground
water quality, site topography, willingness of landowners to participate, proximity and age of
existing hydraulic fracturing sites, etc.
Baseline Monitoring: includes selecting locations considering such conditions as depth, direction
and rate of groundwater flow; establishing surface water monitoring locations and scheduling at
least four, quarterly, water quality and flow monitoring events; conducting baseline monitoring
and documenting the baseline water quality.
Pad Installation Well Drilling and Completion: includes documenting well construction details,
well integrity, and assessing any impacts to water quality. Examples of practices that could be
evaluated include well pad liner installation and berm construction, well casing and cement
installation, and the construction of secondary containment for tanks and impoundments,
followed up by observing pad construction, drilling and completion of the production well, and
monitoring for ground and surface water.
Hydraidic Fracturing Flow back Management: includes documenting the hydraulic fracturing
and flowback process; examples of the types of practices to be observed and documented include
site-specific reports of geology, production well drilling records including driller logs (e.g. fluid
volumes, cuttings descriptions) and wire-line geophysical logging records, production well
construction records including casing design and cementing records, mechanical integrity testing
reports (e.g., pre and post fracturing), cement bond logs, pressure monitoring records for the
production well, and microseismic test reports including monitoring of fracture propagation.
Ideally, tracers would be used to assist assessment of the ultimate fate and transport of hydraulic
fracturing fluids; follow up includes sampling flowback at intervals, and also monitoring the
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conditions in ground water and surface water through use of in-situ devices installed within
monitoring wells and surface water monitoring stations and periodic acquisition of water samples
for laboratory analysis.
Oil and/or Gas Production: includes documenting flowback and produced water management
practices, confirming with the operators the volumes of produced water that result from the
process and the treatment and /or disposal methods employed, monitoring surface water and
ground water for at least a year following the start of the production phase, and obtaining water
quality samples at least quarterly.
Water Quality Monitoring
Water quality monitoring can help inform answers to the five fundamental questions related to
the hydraulic fracturing water lifecycle. EPA plans to use pre-existing monitoring points where
possible. Options here would include private, public, industrial and agricultural wells as well as
springs and surface water bodies within the local drainage system. EPA also plans to install
targeted monitoring wells. The locations, depths and numbers of wells will depend on the local
ground water depth, flow rate and flow direction. Monitoring wells would be placed in locations
that would intercept anticipated flow pathways within aquifers. The conceptual framework for
monitoring is displayed in Figure 2:
Figure 2: Conceptual Framework for Monitoring
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Anticipated Timeline
EPA has not yet selected the sites for these prospective case studies. We are working closely
with oil and gas well owners / operators, the hydraulic fracturing industry, other federal partners
and landowners to assure that site selection for these prospective studies will yield scientifically
robust and reliable results. Once the sites have been selected the timeline is expected to proceed
as shown in Figure 3.
>
Monitor water quality and flow indicators
Figure 3: Anticipated Timeline
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The Role of Borehole Geophysics in Groundwater Investigations
Ronald A Sloto
U.S. Geological Survey
The statements made during the workshop do not represent the view or opinions of EPA.
The comments made by participants have not been verified or endorsed by EPA.
Introduction
Borehole-geophysical logging provides a wealth of information that is critical in gaining an
understanding of subsurface conditions needed for groundwater and environmental studies.
Multiple logs typically are collected to take advantage of their synergistic nature—much more
can be learned by the analysis of a suite of logs as a group than by the analysis of the same logs
individually. Borehole geophysics is used to obtain information on well construction, rock
lithology and fractures, permeability, and water quality. They provide information on the
borehole and aquifer than cannot be obtained in any other way.
Borehole Geophysical Logs
Common geophysical logs include caliper, gamma, single-point resistance, electromagnetic
induction, fluid resistivity, fluid temperature, flowmeter, television, and acoustic televiewer.
Caliper logs provide a continuous record of average borehole diameter, which is related to
fractures, lithology, and drilling technique. Caliper logs are used to identify fractures, water-
bearing openings, and sometimes lithology. Because borehole diameter commonly affects log
response, the caliper log is useful in the analysis of other geophysical logs, including
interpretation of flowmeter logs.
Natural-gam ma logs record the natural-gamma radiation emitted from rocks penetrated by the
borehole. Uranium-238, thorium-232, and the progeny of their decay series and potassium-40
are the most common emitters of natural-gamma radiation. These radioactive elements are
concentrated in clay and shale by adsorption, precipitation, and ion exchange. Fine-grained
sediments, such as mudstone or siltstone, usually emit more gamma radiation than sandstone.
The gamma log often is used to interpret lithology and to correlate geologic units between
boreholes.
Single-point-resistance logs record the electrical resistance between the borehole and an
electrical ground at land surface. In general, resistance increases with grain size and decreases
with borehole diameter, density of water-bearing fractures, and increasing dissolved-solids
concentration of borehole water. Si ngl e-poi nt-resi stance logs are used to correlate lithology
between boreholes and may help identify water-bearing fractures.
El ectromagneti c-i nducti on logs record the electrical conductivity or resistivity of the rocks and
water surrounding the borehole. Electrical conductivity and resistivity are affected by the
porosity, permeability, and clay content of the rocks and by the dissolved-solids concentration
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of the water within the rocks. The electromagnetic-induction log can work through plastic
casing.
Fluid-temperature logs provide a continuous record of the vertical water-temperature variation
in the borehole. They are used to identify water-bearing fractures and to determine intervals of
vertical borehole between zones of differing hydraulic head penetrated by the borehole. Water-
producing and water-receiving zones usually are identified by sharp changes in temperature, and
borehole flow between those zones is indicated by temperature gradients that are less than the
regional geothermal gradient.
Fluid-resistivity logs measure the electrical resistance of the water in the borehole. Changes in
fluid-resistivity reflect changes in the dissolved-solids concentration of the borehole water.
Fluid-resistivity logs are used to identify water-bearing fractures and intervals of vertical
borehole flow. Water-producing and water-receiving fractures usually are identified by sharp
changes in resistivity. Intervals of vertical borehole flow usually are identified by a low-
resistivity gradient between a water-producing and a water-receiving zone.
Flowmeter logs record the direction and rate of vertical flow in the borehole. Flowmeter logs
can be collected under non-pumping (ambient) and/or pumping conditions. The direction and
rate of borehole-fluid movement is generally measured with a high-resolution heatpulse
flowmeter. The range of flow measurement is about 0.01 to 1.5 gallons per minute in a 2- to 10-
inch diameter borehole. Flow from fractures can be induced by pumping the borehole at a low
rate and maintaining a constant drawdown (pumping conditions).
Borehole television surveys are conducted by lowering a waterproof video camera down the
borehole and recording the image on DVD. The optical image can be viewed in real time on a
monitor. Well construction, lithology and fractures, water level, cascading water from above the
water level, and changes in borehole water quality (chemical precipitates, suspended particles,
and gas) can be viewed directly with the camera.
Acoustic-televiewer logs record a magnetically oriented, photographic image of the acoustic
reflectivity of the borehole wall. Televiewer logs indicate the location and strike and dip of each
fracture and lithologic contact. The televiewer tool also includes a borehole dipmeter.
Water quality samples can be collected at a discrete depth using a wire-line sampler. The
sampler is lowered to a desired depth, opened, allowed to fill with water, and closed. Up tp a
liter of water can be collected.
Aquifer-isolation (packer) tests, although not a borehole geophysical technique, are often used
in conjunction with borehole geophysics to define the hydraulic and chemical characteristics of
discrete water-bearing fractures in a borehole. This characterization only can be performed by
isolating each water-bearing fracture with straddle packers so that its properties can be separated
from the other water-bearing fractures in the borehole. Selection of fractures to isolated and
depth of packer placement is determined by analysis of borehole geophysical logs. The packer
assembly is lowered to the selected depth in the borehole, and the packers are inflated against
the borehole wall, isolating the selected interval. The isolated interval is pumped to measure
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hydraulic characteristics and collect a discrete-depth water sample. Hydraulic head response to
pumping can be measured in the isolated interval and in the aquifer above and below the
isolated interval.
Example for how to use geophysics to design a water-monitoring network
The two wells supplying water to the Willow Grove Naval Air Station/Joint Reserve Base in
Horsham Township, Montgomery County, Pennsylvania, were contaminated with
tetrachloroethylene (PCE). Several investigations of nearby suspected sources were
investigated, and numerous monitor wells were drilled. However, the source of the PCE could
not be identified. In support of the Navy investigation, the U.S. Geological Survey conducted
borehole geophysical logging and aquifer-isolation tests in the two supply wells. The ground-
water-flow system for the supply wells was characterized by use of borehole geophysical logs
and heatpulse-flowmeter measurements. The hydraulic and chemical properties of discrete
water-bearing fractures in the supply wells were characterized by isolating each water-bearing
fracture with straddle packers (Sloto and others, 2002).
First, the caliper log was used to determine the location of fractures in the supply wells. The
fluid-temperature and fluid-resistivity logs were used to determine which fractures identified by
the caliper logs potentially provided water to the wells. Heatpulse-flowmeter measurements
made above and below each potential water-producing fracture confirmed the water-bearing
fractures (Figure 1). The natural gamma and electric logs were used to correlate lithology
between the supply wells and each individual bed was labeled. The caliper logs and borehole
television surveys were used to locate smooth sections of borehole to set straddle packers. Each
identified water-producing fracture was isolated with straddle packers, and a sample of water
produced by the fracture was pumped and analyzed for volatile organic compounds.
Lithologic unit H, which was identified using the natural gamma and electric logs, was the
major source of PCE contamination for both supply wells. Using the strike and dip of lithologic
unit H, the outcrop area was projected to be approximately 2,300-2,450 feet southeast of supply
well 1. The projected outcrop is updip and hydraulically upgradient from the supply wells. A
subsequent investigation by the U.S. Environmental Protection Agency showed that an aircraft
plant was formerly located in the outcrop area of lithologic unit H, and the shallow groundwater
and nearby wells contained highly elevated concentrations of PCE.
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SINGLE POINT FLUID
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Circle at depth of flow measurement.
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DIRECTION OF VERTICAL BOREHOLE
FLOW-Upward arrow indicates upward flow;
downward arrow indicates downward flow
FLOW INTO BOR EH OLE-
Arrow pointing away from caliper log
indicates flow into borehole
FLOW OUT OF BOREHOLE—
Arrow pointing toward caliper log
indicates flow out of borehole
Figure 1. Borehole geophysical logs for supply well 1, Willow Grove Naval Air
Station/Joint Reserve Base, Horsham Township, Montgomery County, Pennsylvania.
Reference
Sloto, R.A., Goode, D.J., and Frasch, S.M. (2002) Interpretation of borehole geophysical logs,
aquifer-isolation tests, and water quality, supply wells 1 and 2, Willow Grove Naval Air
Station/Joint Reserve Base, Horsham Township, Montgomery County, Pennsylvania. U.S.
Geological Survey Water-Resources Investigations Report 2001-4264, 64 p.
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EPA's Study of the Potential Impacts of Hydraulic Fracturing on Drinking Water Resources:
Summary of July 30, 2013, Technical Workshop on Case Studies to Assess Potential Impacts of Hydraulic Fracturing
on Drinking Water Resources
Groundwater Monitoring for EPA Prospective Case Study Site
Daniel J. Soeder, U.S. Department of Energy, National Energy Technology Laboratory,
Morgantown, WV
The statements made during the workshop do not represent the view or opinions of EPA.
The comments made by participants have not been verified or endorsed by EPA.
Monitoring of groundwater at shale gas development locations before, during and after
the drilling, hydraulic fracturing and completion process is important for a number of reasons.
Drilling through shallow aquifers can affect groundwater if compressed air infiltrates into the
aquifer, potentially causing a groundwater flow surge. Drilling overbalanced may also allow
drilling mud or chemicals to get into the groundwater. The hydraulic fracture process creates
pressure pulses at depth that reach the surface, and can affect groundwater, potentially changing
the solubility of naturally-occurring methane gas in aquifers and causing it to mobilize. Data on
stray gas mobilization, fluid infiltration, and water quality effects related to wellbore integrity,
the reliability of casing and cement, and surface spills of frac chemicals or produced water can
only be obtained through groundwater monitoring. Ancillary questions, such as soil gas
composition and migration, and the rates at which natural attenuation processes might break
down organic chemicals and produced hydrocarbons can also be addressed by monitoring
groundwater.
Surface spills are the primary risk to groundwater from shale gas operations. Monitoring
shallow groundwater and streams in small watersheds will help with early detection, but
indicators are needed for drilling mud, hydraulic fracture chemicals, and produced fluids. Sr
isotopes appear to be a good indicator for Marcellus shale produced water, but others are also
needed. Longer-term concerns include leachate from sulfide-rich drill cuttings as a possible risk
to groundwater.
Current plans call for at least three and possibly more groundwater monitoring wells to be
installed off the pad at an EPA prospective case study site. One well will be installed up-
gradient, with two or potentially three wells down-gradient. The wells will be drilled to a
nominal depth of 100 meters (300 feet), and completed open hole with surface casing set at least
five feet below the base of the soil.
Installation costs will be funded by DOE-NETL through the site support contractor, and a
commercial monitoring well driller will be used. The driller must possess a well drillers license
for the State of Pennsylvania and the State of West Virginia, have air and mud rotary and/or air
hammer capability, and demonstrate the successful completion of at least 10 monitor or water
wells that are at least 300 feet deep within the last five years in Pennsylvania and/or West
Virginia. The driller must also show documented experience with groundwater sampling during
drilling, and provide resumes for on-site personnel to prove that the crew has the proper training
and sufficient work experience to successfully carry out the operation.
All drilling and earthmoving equipment must be washed and decontaminated prior to
arrival on the site, and all equipment will be inspected for safe operations. Wells are to be drilled
using the hydraulic air-rotary or air-hammer method, unless hole conditions do not allow. Foam
B-10
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EPA's Study of the Potential Impacts of Hydraulic Fracturing on Drinking Water Resources:
Summary of July 30, 2013, Technical Workshop on Case Studies to Assess Potential Impacts of Hydraulic Fracturing
on Drinking Water Resources
or fresh water may be used if wet or saturated zones are encountered that make air drilling
impractical. Lubricants used for drill pipe and casing shall be Teflon-based; no additives are
allowed without authorization. Surface casing and cement shall meet WV or PA DEP monitor
well standards and EPA standards in SESDGUID-101-R1, Design and Installation of Monitoring
Wells.
A nominal 10 ^-inch hole will be drilled at least 20 feet deep to allow surface casing to
be set to a depth of at least 5 feet below the base of alluvium and soils. The surface casing will
be cemented in place and cement run to the surface to seal the annulus. The well will then be
drilled open hole to a depth of 200 feet. The deviation angle of the well will be measured and
corrected back to vertical if greater than half a degree. The total depth of the hole will nominally
be 300 feet.
At each water-bearing zone encountered during drilling, operations will be paused to
measure water levels and collect samples. Inflow rates shall be noted. Drill cuttings will be
sampled at nominal intervals, and containerized for disposal. Core will be cut as directed. The
driller will then develop the completed well, ensuring an inflow of at least ten gallons per minute
through the completion zone. After site cleanup, wireline logs will be run as directed, possibly
including gamma, density, neutron porosity and saturation, resistivity and others. The well will
then be turned over to DOE/EPA/USGS for sampling.
Sampling will use a multilevel insert in the well to collect groundwater from various
depths defined from the inflow tests and a geologic evaluation of the aquifer. These multilevel
samplers typically allow access to several dozen distinct zones isolated by inflatable packers.
Prior to employing these at the prospective case site, an existing USGS monitoring well will be
used to field test one or more of these systems to ensure that pump and purge rates suitable for
EPA groundwater sampling protocols can be achieved.
Current plans call for identifying an industry cooperator and adjacent landowners who
will allow the proposed groundwater monitoring wells to be placed in the vicinity of shale gas
well site. This process is currently underway and in discussions. The DOE-EPA-USGS team
will make joint decisions about well locations, depth, aquifer zones, and water sampling once a
site is positively identified and selected. In addition to periodic, synoptic groundwater sampling,
the wells will be outfitted with real-time monitors for water levels, pH, conductivity (TDS),
turbidity, DO, temperature, and possibly headspace gas.
Future efforts will include making contacts with other shale gas drillers in other areas for
similar access. Comparison studies on other shale plays are needed to more fully understand the
possible effects of shale gas development on underground sources of drinking water.
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