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User Guide for Aquifer Exemption Data
Aquifer Exemption Data Release
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 (UIC) 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 UIC
permit applications and approvals.
Background on Aquifer Exemptions
An aquifer is an underground body of rock that contains or can transmit groundwater. The UIC 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 UIC
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
Simplified Schematic Showing Scenarios Where
Aquifer Exemptions Might be Requested
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
The 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 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 fact sheet, and a
user guide from the website.
The map and accompanying data can be used by
states, businesses, communities, and others to
An aquifer exemption may be required
to produce oil, natural gas, or minerals
from an aquifer.
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.
An aquifer exemption may be required to
place wastes from industrial processes into
portions of aquifers.
Aquifer mixed
with oft natural
gas, or minerals
Rock layers that
protect overlying
aquifers from
contamination
Figure 1. Simplified schematic showing scenarios where aquifer
exemptions might be requested. The 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
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 applications
and approvals. The map consolidates information that was previously only available on paper and/or in databases at the
Regional and state level and will assist EPA and states in maintaining consistent exemption data across the nation.
Aquifer exemption locations in California are not included in the current data. California is engaged in a process to
digitize existing exemption locations and is also currently reviewing numerous requests for new or expanded aquifer
exemptions that they expect to submit to the EPA Region 9 for review. As this work progresses, the aquifer exemptions
in California will be added to the national dataset. The EPA is also working closely with Texas to better understand cases
where Texas should have requested an exemption for Class II wells injecting oil and gas-related fluids.
How the EPA Developed the Aquifer Exemption Data
To develop the dataset of aquifer exemption information, the EPA gathered available information about approved
aquifer exemptions from its Regional offices and some state agencies. The Agency collected the aquifer exemptions
information from paper files, spreadsheets, and databases generated over the past 30 years. A new, national dataset
was created with the collected information. The EPA assessed the quality of the new dataset by comparing it to the
original documents to confirm the accuracy of the new data.
The 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 for each aquifer exemption exist. The EPA continues to gather additional information to
enhance the coverage of aquifer exemptions 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 Exemptions Map on the EPA Geoplatform.
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, which can be viewed 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.
M
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User Guide for Aquifer Exemption Data
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
Underground Injection Control (UIC) Program
txemptions Map
Wall Claw Depth	Qualify further Info, manon
About Aquifer Exemptions
The map and accompanying data can be used by states, businesses,
communities and other* 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 (UK) permit applications and approvals. The map
consolidates information that was previously only avaiiaWc on paper and/or
in databases at the state level and will assist EPA and states in maintaining
consistent exemption data across the nation.
Aquifer exemptions in California are not shown on the maps. California is
engaged in a process to digrtnc existing exemption locations and is also
currently reviewing numerous requests for new or expanded aquifer
exemptions that they expert to submit to f PA Region "3 for revtew. As thft
An aquifer is an underground body of rock that contains and can transmit
groundwater, The EPA exempts aquifers if the aquifer does not currently
.1	serve as a source of drinking water and wtllnw serve as a source of dnnking
Text panels	I & water m the future, twsed on certain criteria. Aquifer exemptions allow
, . I	|l\ these underground sources of water to be used by energy and mining
OP! eSCh tab	^Wcompanies for oil or mineral extraction or disposal purposes in compliance
. . . ,	^th FPA's requirements.
explain the __ /
. r	About the Data
information I w
this website provides an interactive map that allows users to find locations
of aquifers approved for exemption under the Safe Drinking Water Act. Tile
website also provides geospatial files and excel data witn 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 geotogy. and injected fluid characteristics. The Excel
spreadsheet provides descriptive information from the geospatial file
without geospatial daU. Users may download the dataxets, a tact sheet and
a user guide from the 'further infocmaoon* tab.
Figure 2. Tabs at the top of the Aquifer Exemption Map allow users to view different information about
the exemptions. Users may download data, the 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.
Aquifer Exemption Boundaries
When the user first visits the Aquifer Exemption map, the map scale is set to show the entire United States. Aquifer
exemptions are indicated as points at such a small scale so that all the exemption locations are visible. As the user
increases the map scale to show more detail, the aquifer exemption boundaries will begin to change from points to
polygons. The polygons 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,
Injection Well Classes Associated with Aquifer Exemptions
There are six classes of injection wells under the 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
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User Guide for Aquifer Exemption Data
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.
Operators or states typically describe the injection
activity proposed for an aquifer when requesting an
exemption from the EPA. Aquifer exemptions requested
as of January 2016 are usually associated with three of
the six classes of injection wells regulated by the EPA
Underground Injection Control program. Most aquifer
exemptions (about 95 percent) are associated with Class
II wells. Almost two-thirds of aquifer exemptions
associated with Class II wells are for enhanced oil or gas
recovery (Class MR) and one-third are for disposal of
wastewater (Class IID). A small percentage of the aquifer
exemptions are not associated with specific Class II
activities such as enhanced recovery or disposal; those
aquifer exemptions are designated as Class II rather
than Class IID or Class NR. About two percent are
associated with Class III mining wells. The remainder are
associated with Class I wells used to inject non-
hazardous industrial wastes and others.
Aquifer Exemption Depth Map
The aquifer exemptions 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
one 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 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.
Depth of the aquifer exemptions is measured as feet below ground surface in the majority of exemptions. In some
aquifer exemptions located in Louisiana, Texas, and Oklahoma, depth is measured as feet mean sea level. The two scales
for measuring depth are shown separately in the legend.
Data Quality Map
The 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
the EPA approved exemptions.
(1 of 13)
8 689
Region: 8
Exemption ID: 8_689
State and Tribe: WY
County: Converse
Well Class Type: I
Exemption Area: 4 square miles
Exemption Depth: 9,137 feet BGS
Injection Zone: Teapot
Lithology: sandstone
Tniartata rharartarictirc
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
b
Because the 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. The EPA continues to collect information
about these aquifer exemptions, and new information will be added to the geospatial file as it becomes available.
Precise location: The 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, 863 aquifer exemptions, or 26%, have
a precise location and complete attribute record.
Less precise location and some attributes missing: The 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, 1,981 aquifer exemptions, or 60%, fall into this category.
Imprecise location or several attributes missing: The 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 (311 aquifer exemptions; 9%), are shown on the map.
County locations available only: The current dataset contains 102 aquifer exemptions (3%) that have only
county-level locations. While the EPA is unable to draw polygons for these aquifer exemptions, the counties
containing these exemptions are outlined on the map. The EPA continues to collect information about these
aquifer exemptions.
Locations unavailable at this time: California is engaged in a process to digitize existing exemption locations
and is also currently reviewing numerous requests for new or expanded aquifer exemptions that they expect
to submit to EPA Region 9 for review. As this work progresses, the aquifer exemptions in California will be
added to the national dataset.
A small number of aquifer exemptions are not included in the geospatial data (38 aquifer exemptions; 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
The 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 UIC program, see https://www.epa.gov/uic.
To download the geospatial file and related materials, visit https://www.epa.gov/uic/aquifer-exemptions-map.
Call the Safe Drinking Water Hotline at 1-800-426-4791 for questions on the aquifer exemptions data or map, or search
the FAQ database at https://www.epa.gov/ground-water-and-drinking-water/safe-drinking-water-hotline
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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.
Well Class
The injection well class associated with the aquifer exemption at the time the exemption was
approved.
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 EPA Geoplatform 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 extent/boundary of the exempted aquifer (e.g., radius, acreage, etc.), along with the specific units
(e.g., square feet, miles, acres) describing the exempted area.
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 injection zone/exempted aquifer or its elevation below mean sea
level.
Depth Units
The specific units describing the depth to the top 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).
Lithology
A brief description of the type of rock that comprises the injection zone/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.
Approval 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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