7/14/10
Opportunity for Stakeholder Input on
| EPA's Hydraulic Fracturing Research Study:
V ^	Study Design
Natural gas plays a key role in our nation's clean energy future, and hydraulic fracturing (HF) is one way
of accessing this vital resource. Over the past few years, the use of HF for gas extraction has increased
and expanded over a wider diversity of geographic regions and geologic formations. While HF was
predominately used in coalbed methane extraction in the 1990s, it has been used in recent years to extract
natural gas from shale formations. Shale gas is expected to comprise over 20% of the total U.S. gas
supply by 2020. At the same time, concern is mounting among the public, media, and Congress over the
potential impacts of HF on drinking water. Due to the increasing use of HF and these growing concerns,
EPA announced in March 2010 that it will study the relationship between HF and drinking water. To help
design this study, EPA is identifying the key interactions between HF and water resources. EPA seeks
input from the public and stakeholders regarding these interactions.
The Hydraulic Fracturing Process
EPA is examining the entire HF process — from obtaining the water necessary for fracturing fluids to
operations to disposal of wastes — to assess potential impacts on water resources. There are several steps
in the HF process.
First, necessary site infrastructure is built, which includes well construction. Production wells may be
drilled in the vertical direction only or paired with horizontal or directional sections. Vertical well sections
may be drilled hundreds to thousands of feet below the land surface and lateral sections may extend
several thousand feet away from the well. Next, fluids made up of water and chemical additives are
pumped through the well into a geologic formation at high pressure. When the pressure exceeds the rock
strength, the fluids open or enlarge fractures that can extend several hundred feet away from the well. A
propping agent (such as sand or ceramic beads) is then pumped into the fractures to keep them from
closing once the pumping pressure is released. After fracturing is completed, the fracturing fluids (water
and chemical additives) return to the surface due to internal pressure of the geologic formation or
pumping done at the surface. Recovered fracturing fluids, referred to as flowback, may be stored in tanks
or pits. There are several management options for the wastewater, including treatment and discharge into
surface water, underground injection, or recycling.
Potential Impacts to Water
Water is involved in many parts of the HF process. There are four main phases of water use in HF
operations:
1.	Acquisition of water for well drilling and fracturing operations;
2.	Mixing water with chemicals and proppant (e.g., sand, ceramic beads) for the fracturing operation
itself, injection of fracking fluids, and return of wastewater to the surface;
3.	Storage of wastewater;
4.	Treatment, disposal, or recycling of wastewater.
1

-------
7/14/10
The HF process may affect both surface and ground water. It may pose risks to drinking water supplies by
reducing the volume of available drinking water and/or introducing contaminants into the drinking water
supply. These risks can be classified as impacts to water quantity and quality.
Potential Impacts on Water Availability (Quantity)
The HF process uses a large volume of water and thus may affect water availability. It is estimated that it
takes two to five million gallons of water to drill and fracture a well. This water can come from either
ground or surface water sources depending on the location of the well. The use of large volumes of water
could stress drinking water supplies, especially in drier regions where aquifer or surface water recharge is
limited. Large withdrawals of waters for HF could potentially lead to lowered water tables or dewatered
drinking water aquifers, decreased stream flows, and reduced volumes of water in surface water reservoirs
(Table 1). This could negatively affect the availability of water for drinking and other uses in areas where
HF is occurring.
Potential Impacts on Water Quality
Underground sources of drinking water (USDWs) are usually accessed at depths of less than 1,000 feet,
while natural gas production wells are typically drilled to depths ranging from 1,000 to 8,000 feet.
However, deeper USDWs are also present in the U.S. and may occur at depths coincident with oil and gas
reservoirs. There are several potential mechanisms by which contaminants could be introduced into
drinking water supplies or USDWs during HF, including:
Transport of contaminants through natural fractures in the rock into adjacent drinking water
aquifers;
Transport of contaminants into underground drinking water zones through the fractures produced
during the hydraulic fracturing process;
Transport of contaminants into drinking water through abandoned or other pre-existing wells;
Leakage of contaminants from production wells (e.g., improperly constructed or damaged wells);
leaching of contaminants from improperly lined storage or drilling pits; and
Spills of the HF fluids into surface water bodies used for drinking water.
When HF fluids or flowback water are introduced into the subsurface, they could potentially alter the
natural conditions that exist in the underground environment. Changes in the geologic formation could
lead to the release of naturally occurring metals, radionuclides, organic contaminants and gases present in
rock and/or cause the migration of contaminants from the natural gas reservoir into adjacent geologic
formations.
The HF process may also impact surface water quality. For example, total dissolved solids (TDS) could
increase significantly in surface water from discharges from wastewater treatment facilities or runoff of
wastewater into nearby surface waters. Wastewater treatment facilities that accept wastewater from HF
sites are sometimes not capable of reducing TDS to concentrations that the receiving water is capable of
diluting to safe levels. High TDS discharges can cause adverse impacts to receiving streams used for
drinking water supplies.
2

-------


7/14/10
Table 1: Potential impacts to surface and ground water resources
from the hydraulic fracturing process.
\Vsilcr in 1 lie
SuiTsiee Wsiler
(¦round \\ silcr
III-' process
Impsicls

WiUcr I sed in Lracluring
Decreased surface water Hows
Lowered wtiler table. dewtilered
I'luids

tiquiler
1l\ drtiulic Lracluring
Potential runoff to streams from Abandoned wells as conduits to
(including injection of
leaks, spills, accidents
adjoining drinking water aquifers
iViicliiiinu lluids and return of


wastewater to the surface)

Well failure or poor construction.


leading to leakage to adjoining


drinking wtiler aquifers


Lraclures or faults leading to


leakage to adjoining drinking


water aquifers
Storage of Wastew tiler
Storage pit water runoff to
Pit water leaching to underground

streams from leaks, spills.
sources of drinking water

accidents

Disposal. Treatment.
Wastewater treatment plant
Well failure or poor construction.
Rec\ cl i ng of Wastew tilers
discharges to surface water
leading to fluid migration into


adjoining drinking water aquifers

Wastew tiler spills

Stakeholder Input
EPA is seeking input from stakeholders and the public to help inform the development of the study
design. In particular, the Agency would appreciate responses to these questions related to the table
presented here:
1.	Can you suggest additional pathways of exposure that could impact drinking water resources from
the hydraulic fracturing process?
2.	In your experience, what are the most important processes and pathway(s) of exposure that would
adversely impact drinking water resources?
3.	What current practices in your region do you think pose the most threat to drinking water
resources from hydraulic fracturing?
4.	Can you provide data, studies, reports, or other information to help us assess the relative
importance of these potential impacts?
3

-------