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User Guide for Aquifer Exemption Data
Aquifer Exemption Data
EPA's Aquifer Exemption map allows users to view aquifers that have been approved for exemption by EPA under the
Safe Drinking Water Act Underground Injection Control regulations. This interactive map brings together data
previously available only in paper form or at the Regional and state level. The map and accompanying data can be used
by states, businesses, communities, and others to view exempted aquifers in the United States, see accompanying
aquifer exemption data like depth of injection, local geology, and injected fluid characteristics, and can assist with
Underground Injection Control permit applications and approvals.
Background on Aquifer Exemptions
An aquifer is an underground body of rock that contains or can transmit groundwater. The Underground Injection
Control regulations allow EPA to exempt aquifers that do not currently serve as a source of drinking water and will not
serve as a source of drinking water in the future, based on certain criteria. Aquifer exemptions allow these underground
sources of water to be used by energy and mining companies for oil or mineral extraction or disposal purposes in
compliance with EPA's Underground Injection
Control requirements under the Safe Drinking
Water Act. Figure 1 shows simplified scenarios
where a well owner/operator or a state might
request EPA to approve an aquifer exemption.
The process begins when EPA receives information
about the aquifer proposed for exemption from a
state agency or well owner or operator. EPA
approves the aquifer exemption request if it meets
the necessary criteria. Injection of fluids can begin
only after EPA approves an aquifer exemption and
an underground injection control permit is
granted.
Aquifer Exemption Data Initiative
EPA developed an interactive Aquifer Exemption
Map that allows users to find locations of aquifers
approved for exemption under the Safe Drinking
Water Act. The website also provides geospatial
files and data in a Microsoft Excel spreadsheet
with this accompanying user guide. The map
shows the approved aquifer exemption
boundaries, when available, in two dimensions and
information such as the depth of injection, local
geology, and injected fluid characteristics. The
Excel spreadsheet provides descriptive information
from the geospatial file without geospatial data.
Users may download the datasets, a fact sheet,
and this user guide from the website.
The map and accompanying data can be used by
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Simplified Schematic Showing Scenarios Where
Aquifer Exemptions Might be Requested
An aquifer exemption may be required
to produce oil, natural gas, or minerals
from an aquifer.
Aquifer mixed
with oil, natural
gas, or minerals
The EPA developed the aquifer exemption
process to protect drinking water aquifers and
meet industry needs. An aquifer exemption
allows fluid that might otherwise endanger a
drinking water source to be placed into a specific
portion of an aquifer The EPA evaluates the
boundaries of the aquifer exemption proposed
by the well owner/operator or state so that
nearby drinking water sources remain protected.
The boundaries are shown for illustration
purposes as yellow dashed lines in this figure.
Rock layers that
protect overlying
aquifers from
contamination
An aquifer exemption may be required to
place wastes from industrial processes into
portions of aquifers.
Figure 1. Simplified schematic showing scenarios where aquifer
exemptions might be requested. EPA evaluates proposed aquifer
exemption boundaries where fluids may be injected while continuing
to protect nearby drinking water sources. The boundaries are shown
for illustration purposes as yellow dashed lines.

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User Guide for Aquifer Exemption Data
states, businesses, communities, and others to view exempted aquifers in the United States, see accompanying aquifer
exemption data like depth of injection, local geology, and injected fluid characteristics, and can assist with Underground
Injection Control permit applications and approvals. The map will assist EPA and states in providing transparency and
maintaining consistent exemption data across the nation.
Not all aquifer exemption locations are included in the current data. California is engaged in a process to digitize existing
aquifer exemption locations and is also currently reviewing numerous requests for new or expanded aquifer exemptions
that they expect to submit to EPA for review. As this work progresses, the aquifer exemption data for California will be
added to the national dataset.
How EPA Developed the Aquifer Exemption Data
To develop the dataset of aquifer exemption information, EPA gathered available information about approved aquifer
exemptions from its Regional offices and some state agencies. The Agency collected the aquifer exemption information
from paper files, spreadsheets, and databases generated over the past 35 years. A new, national dataset was created
with the collected information. EPA assessed the quality of the new dataset by comparing it to the original documents to
confirm the accuracy of the new data.
EPA also developed a geospatial dataset that allows users to view or create a map of the aquifer exemption locations.
The location of each exempted aquifer was converted from text descriptions to geospatial data. The text descriptions
were recorded in multiple formats. A table of attributes associated with each aquifer exemption polygon includes
information on the state, county, depth, geologic formation, lithology, approval date, and regulatory criteria met. More
information on each attribute can be found in the data dictionary (Table 1).
Some gaps in information exist for many aquifer exemptions. EPA continues to gather additional information to enhance
the coverage of aquifer exemption information across the nation. The dataset will be periodically updated in the future
with new information on existing exempted aquifers and newly approved exempted aquifers. Users who want specific
local information on aquifer exemption locations or attributes should contact the EPA Regional Office that approved the
aquifer exemption.
Both the geospatial data and the attribute data are shown in the Aquifer Exemption Map. Users can explore the data in
the Aquifer Exemption Map or by downloading the files to create their own maps.
Aquifer Exemption Map
The Aquifer Exemption Map shows the locations and boundaries of aquifer exemptions with various descriptions of the
exempted aquifers. The aquifer exemptions can be described in multiple ways, and users can view the information by
clicking on the tabs at the top of the map, as shown in Figure 2.
Within the maps found on the Well Class, Depth, and Data Quality tabs, zooming in allows users to see individual aquifer
exemptions or several aquifer exemptions within a small geographic area. The pop-up boxes on the Aquifer Exemption
Map, as shown in Figure 3, describe certain attributes about the aquifer exemption. Locational information such as
county, state, and tribe, are also found in the pop-up box.
Aquifer Exemption Boundaries
When the user first visits the Aquifer Exemption map, the map scale is set to show the entire United States. At this level,
the states are color coded to reflect the number of approved aquifer exemptions in each state. A darker gray color
corresponds to a higher density of exemptions while a lighter gray corresponds to a lower density. Aquifer exemptions
are indicated as points at such a small scale so that all the exemption locations are visible. As the user changes the map
scale to show more detail, the aquifer exemption boundaries will begin to change from points to polygons. The polygons
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User Guide for Aquifer Exemption Data
represent the two-dimensional aquifer exemption boundaries. For example, locations described by a radius around a
specific latitude and longitude, as shown in Figure 3, appear as a circle. Some aquifer exemptions are defined by one or
more grids in the Public Land Survey System and have a square or rectangular appearance, shown in Figure 3. The Public
Land Survey System describes an area using a grid system with numbered townships, ranges, and sections. Map scale
may be changed by clicking on the scale adjustment tool represented by the following image on the Aquifer Exemption
Map.
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Underground Injection Control (UIC) Program
injection Well Classes Associated with Aquifer Exemptions
There are six classes of injection wells under EPA's regulations. Class I wells are for the injection of industrial and
municipal waste fluids. Class II wells are for the injection of fluids related to oil and gas operations, such as enhanced
recovery (Class MR) or disposal of production wastes (Class IID). Class III wells inject fluids that assist in extraction of
minerals such as uranium and salts. Class IV wells for certain hazardous or radioactive waste injection are banned except
under limited circumstances as part of an EPA or state-authorized ground water clean-up. Class V wells are for injection
activities not covered by the other well classes. Class VI wells inject carbon dioxide into deep rock formations for the
purpose of long-term storage.
Aciuife exemptions Map
Introduction Well Class Depth Data Quality
further Information
Figure 2. Tabs at the top of the Aquifer Exemption Map allow users to view different information about the
exemptions. Users may download data, this user guide, and the fact sheet on the Further Information tab.
Text panels on each tab give the user context about the data presented on each tab.
Tabs display different
information about
the aquifer
exemptions
The geospatial file, a table of
attributes, user guide for the
data, and fact sheet are available
for download on the Further
Information tab
About Aquifer Exemptions
The map and accompanying data can be used by states,
businesses, communities, and others to view exempted aquifers in
the United States, see accompanying aquifer exemption data like
depth of injection, local geology, and injected fluid characteristics,
and can assist with Underground Injection Control (UIC) permit
Text panels
on each tab
explain the
information
This website provides an interactive map that allows users to find
locations of aquifers approved for exemption under the Safe
Drinking Water Act Underground Injection Control Regulations.
The website also provides geospatial files and Excel data with an
accompanying user guide. The map shows the approved aquifer
exemption boundaries, when available, in two dimensions, and
information such as the depth of injection, local geology, and
injected fluid characteristics. The Excel spreadsheet provides
descriptive information from the geospatial file without geospatial
data. Users may download the datasets, a fart sheet, and a user
guide from the "Further Information" tab.
. An aquifer is an underground body of rock that contains and can
^^transmit groundwater. The EPA exempts aquifers if the aquifer
\toes not currently serve as a source of drinking water and will not
JZrvQ as a source of drinking water in the future, based on certain
T^/criteria. Aquifer exemptions allow these underground sources of
^ water to be used by energy and mining companies for oil or
mineral extraction or disposal purposes in compliance with EPA's
requirements.
About the Data

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User Guide for Aquifer Exemption Data
Operators or states typically describe the injection
activity proposed for an aquifer when requesting an
exemption from EPA. Aquifer exemptions requested as
of November 2019 are usually associated with three of
the six classes of injection wells regulated by EPA's
Underground Injection Control program. Most aquifer
exemptions (about 97 percent) are associated with Class
II wells. About one-third of aquifer exemptions
associated with Class II wells are for enhanced oil or gas
recovery (Class MR) and about one-fourth are for
disposal of wastewater (Class I ID). The remainder of
these aquifer exemptions are not associated with
specific Class II activities such as enhanced recovery or
disposal, although they may be used for recovery or
disposal (or both); those aquifer exemptions are
designated as Class II rather than Class I ID or Class MR.
About one percent are associated with Class III mining
wells. The majority of the remaining aquifer exemptions
are associated with Class I wells used to inject
nonhazardous industrial wastes and other fluids.
Aquifer Exemption Depth Map
The aquifer exemption depth map shows the depth, in
feet, to the exempted aquifer from the land surface or
its elevation below mean sea level. Some aquifer
exemptions are shallow, while others are thousands of feet below the surface (far below drinking water aquifers). About
four percent of aquifer exemptions are 500 feet or less below the surface; most are between 1,000 and 9,000 feet deep.
Some are over 10,000 feet deep. In some cases, there is more than one exempted aquifer at the same location, but at
different depths and in different geologic formations. The aquifer exemptions may have overlapping two-dimensional
boundaries but they are separate aquifer exemptions. Information on overlapping aquifer exemption boundaries is
listed in the pop-up boxes by clicking the left and right arrows at the top of the box, as shown in Figure 3. Depths of the
aquifer exemptions are measured as feet below ground surface in the majority of exemptions. In some aquifer
exemptions located in California, Louisiana, Oklahoma, and Texas, depth is measured as feet relative to mean sea level.
Feet mean sea level can either be positive or negative depending on whether the elevation is above mean sea level
(positive) or below mean sea level (negative). The two scales for measuring depth are shown separately in the legend.
Data Quality Map
EPA continues to assess the quality of the aquifer exemption records. Many of the records are relatively complete. Some
aquifer exemption information is incomplete or aquifer locational information is imprecise. The incomplete or imprecise
information is a result of different methods of documenting the data over the more than three decades that EPA
approved exemptions.
Because EPA seeks to make as much information as possible available to the public, the aquifer exemption polygons are
color-coded to reflect the varying levels of certainty in the locational data. EPA continues to collect information about
these aquifer exemptions, and new information will be added to the geospatial file as it becomes available.
•
(1 of 13)
8_689
¦
Region: 8
Exemption ID: 8_&B9

1 State or Tribe:
County: Converse
Bfc Well Class Type: I

Exemption Area: 4 square miles
Exemption Depth: 9,137 feet BGS

Injection Zone: Teapot
Lithology: sandstone
Injectate Characteristics:
Figure 3. Aquifer exemption locations described by a radius
around a specific latitude and longitude appear as a circle.
Aquifer exemption locations described by one or more grids in the
Public Land Survey System appear as square or rectangle shapes.
Pop-up boxes identify attribute information for each aquifer
exemption. Where there are overlapping polygons, the user can
click on the left and right arrows at the top of the pop-up box to
view information about each aquifer exemption.
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User Guide for Aquifer Exemption Data
Precise location: EPA has a high level of confidence in the location of the aquifer exemption and the
attribute table is complete for the exemption. In the current dataset, 5,056 aquifer exemptions, or 83%,
have a precise location and complete attribute record.	
Less precise location and some attributes missing: EPA has a moderate level of confidence in the location
of the aquifer exemption and continues to collect information to improve aquifer exemption boundaries.
In the current dataset, 636 aquifer exemptions, or 10%, fall into this category.	
Imprecise location or several attributes missing: EPA has information that an aquifer exemption exists, but
the location is imprecise or unclear. Locations with accuracy to the township-level, which is a six-square-
mile area as defined by the Public Land Survey System are shown on the map. In the current dataset, 294
aquifer exemptions, or 5%, are described as imprecise.
County locations available only: The current dataset contains 106 aquifer exemptions (2%) that have only
county-level locations. While EPA is unable to draw polygons for these aquifer exemptions, the counties
containing these exemptions are outlined on the map. EPA continues to collect information about these
aquifer exemptions.
A small number of aquifer exemptions are not included in the geospatial data (23 aquifer exemptions; less than 1%). The
Excel spreadsheet available for download on the "Further Information" tab contains information on the aquifer
exemptions found in the geospatial data as well as the aquifer exemptions without locational information.
Attribute Table
EPA maintains a variety of information about the attributes of aquifer exemptions. Each row in the table describes the
attributes of an individual aquifer exemption. For example, if two aquifers in the same area were exempted, the aquifers
will be described in two separate rows. The polygons that represent the aquifer exemption boundaries on the Aquifer
Exemption Map may overlap in cases where there is more than one aquifer in an area. Users may also download the
attribute table as a Microsoft Excel spreadsheet from the "Further Information" tab.
~
Data Dictionary
The data dictionary shown in Table 1 describes the column headings in the attribute table of the geospatial file and the
Microsoft Excel spreadsheet.
For More Information
For additional information on aquifer exemptions, including the requirements at 40 CFR 146.4, see
https://www.epa.gov/uic/aquifer-exemptions-underground-iniection-control-program.
For additional information on the Underground Injection Control program, see https://www.epa.gov/uic.
To download the geospatial file and related materials, visit https://www.epa.gov/uic/aquifer-exemptions-map.
To contact EPA with questions or comments about aquifer exemptions, please visit
https://www.epa.gov/uic/forms/contact-us-about-underground-iniection-control.
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User Guide for Aquifer Exemption Data
Table 1. Data dictionary for the attribute table of the geospatial file and the Microsoft Excel spreadsheet.
Attribute
Description
Region
EPA Regional Office that approved the aquifer exemption request
Number
A sequential number for each record within the EPA Regional records
ID
A unique identifier for each record that combines the data in the "Region" column and the "Number" attributes
Injection Well ID
The Well ID(s) of individual wells associated with an exemption or the name of a common area, such as a mine
or oil field, associated with the exemption
Well Class
The injection well class associated with the aquifer exemption at the time the exemption was approved
Injection Activity
A narrative description of the activity with which the injection is associated, e.g., brine disposal
State
The state in which the exempted aquifer (or the center point of the delineated exempted area) is located
County
The county in which the exempted aquifer (or the center point of the delineated exempted area) is located
Tribe
The name of the tribe in which the exempted aquifer (or the center point of the delineated exempted area) is
located, if the aquifer is located on Indian country
State or Tribe
A field used specifically for the pop-up boxes in the Aquifer Exemption Map to indicate either the state or tribe
in which the exempted aquifer is located
AE Centroid
(Latitude)
The latitude of the center of the exempted area, in decimal degrees
AE Centroid
(Longitude)
The longitude of the center of the exempted area, in decimal degrees
AE Area
The numerical extent/boundary of the exempted aquifer (e.g., radius, acreage, etc.)
AE Area Units
The specific units describing the exempted area. The units reported to EPA include acres and square miles
Depth
The depth, in feet, to the top of the exempted aquifer or its elevation relative to mean sea level
Depth Units
The specific units describing the shallowest depth of the exempted aquifer. The units reported to EPA include
feet below ground surface (BGS), feet true vertical depth (TVD), feet mean sea level (MSL), and feet measured
depth (MD).
Injection Zone
The name of the formation into which injection is planned or the aquifer identified for exemption
Formation
Thickness
The thickness of the exempted aquifer
Lithology
A brief description of the type of rock that comprises the exempted aquifer
Injectate
Characteristics
A narrative description or salinity of the fluid planned to be injected into the exempted formation. The units
reported to EPA indicate the concentration of total dissolved solids (TDS) in milligrams per liter (mg/L) of fluid.
Decision Date
The date that EPA approved the aquifer exemption request.
Data Quality
Category
A brief description of the data quality for each aquifer exemption. The categories include the following:
•	"Precise location": EPA has a high level of confidence in the location of the aquifer exemption and the
attribute table is complete for the exemption.
•	"Less precise location and some attributes missing": EPA has a moderate level of confidence in the location
of the aquifer exemption and continues to collect information to improve aquifer exemption boundaries.
•	"Imprecise location and several attributes missing": EPA has information that an aquifer exemption exists,
but the location is imprecise/unclear.
•	"County locations available only": EPA is unable to draw actual boundaries for these aquifer exemptions
because only county location information is available. The counties containing the exemptions are outlined
on the map.
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