United States
Environmental Protection
Agency
EPA813-F-94-001
July 1994
Office of Water (4602)
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:ore than 89 percent of U.S. public water
supply systems draw some or all of their
drinking water from sources found under-
ground in rock, sand, and gravel. Ground water
also feeds rivers, lakes, and streams used for
drinking water. Ground water has no respect for
state boundaries. It continually moves, some-
times recharging surface waters hundreds of
miles away from where it started.
Most ground water used for drinking is located
near the earth's surface and is easily contamin-
ated. Of major concern is the potential contamin-
ation of underground sources of drinking water
(USDW) by any of the hundreds of thousands of
injection wells nationwide. Injection wells
dispose of approximately 11 percent of the
nation's fluid waste-.
'" '"
The U.S. Environmental Protection Agency
', (EPA) is working-in partnership with state
and local governments to prevent injection
: wells from contaminating your drinking
i water resources. You can help .by learning
: about EPA's Underground Injection Control
(UIQ program so that you can identify
: injection wells in your community that may
: contaminate your drinking water.
What is An Underground
i infection Well?
' Basically, injection wells are man-made or
: improved "holes" in the ground, which are
deeper than their widest surface dimension .
and are used to discharge or dispose of
i fluids underground. When properly sited,
; constructed, and operated, injection wells
can be an effective and environmentally safe
! means of fluid waste disposal. There are
many different types of injection wells, but
;they are all similar in their basic function.
!The Federal UIC program has grouped
injection wells into five categories:
Class I wells are technologically
sophisticated wells that inject large volumes
of hazardous and non-hazardous wastes into
deep, isolated rock formations that are
separated from the lowermost USDW by
many layers of impermeable clay and rock.
Although most hazardous waste fluids are
treated and released to surface waters,
Class I wells account for 89 percent of the
hazardous waste fluids disposed of on land.
Still, Class I wells inject mostly non-hazard-
ous waste. For example, while all of U.S.
industry together injects approximately nine
billion gallons of hazardous waste each
year, one state alone injects 55 times that
amount in non-hazardous wastes. Class I
wells comprise less than one percent of all
injection wells in the country.
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injection Well Relationship to USDWs
Class I wells
inject hazardous
or non-hazardous
wastes into
geological
formations that
are capable of
confining the
fluids
Class III wells inject fluids
to extract minerals from
underground
Class II wells
inject waste
fluids
associated
with the
production of
oil and natural
gas
Class V wells are
wells that are not
included in the above
classes and inject
non-hazardous fluids
into or above an
underground source
of drinking water
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Class II wells inject fluids associated with
oil and natural gas production. Most of the
injected fluid is brine that is produced when
oil and gas are extracted from the earth
(about 10 barrels of brine for every barrel of
oil). The brine is reinjected to increase pro-
duction, or for disposal. Some Class II wells
are used to store hydrocarbon products.
Class II wells inject 300 billion gallons of fluid
each year. They comprise 41 percent of U.S.
injection wells.
Class III wells inject super-hot steam or
water into mineral formations, which dis-
solves or loosens minerals, which are then
pumped to the surface and extracted. Gen-
erally, the fluid is treated and reinjected into
the same formation. More than 50 percent of
the salt and 80 percent of the uranium extrac-
ted in the U.S. is produced this way. Class III
wells comprise eight percent of injection
wells in the U.S.
Class IV wells inject hazardous or radio-
active wastes into or above USDWs. These
wells are banned under the UIC program
because they directly threaten the quality of
underground sources of drinking water.
Class V wells employ injection practices
which are not included in the other classes.
Some Class V wells are technologically ad-
vanced wastewater disposal systems used by
industry, but most are "low-tech" holes in the
ground. Generally, they are shallow and rely
on gravity to drain or "inject" liquid waste
into the ground. Examples of Class V wells
include dry wells that collect surface water
runoff and industrial, commercial, and utility
disposal wells. In general, Class V waste
disposal wells are located in rural and/or
unsewered areas where people depend on
ground water for their drinking water.' Their
simple construction provides little or no
protection against possible ground water
contamination, so it is important to control
what goes into them. Class V wells comprise
50 percent of the injection wells in the U.S.
How Does the UIC
Program Protect Your
Drinking Water?
Injection wells may threaten ground water
resources if the injection fluids do not stay
within the well and the intended injection
zone. EPA tries to mitigate the risks asso-
ciated with underground injection by estab-
lishing effective regulatory programs. For
Classes I, II, and III wells, the regulatory
program consists of ensuring that the wells
are properly sited, constructed, and opera-
ted to prevent ground water contamination.
Because Class V wells generally are simply
constructed and inject above or directly into
USDWs, EPA must control the types of
wastes operators are allowed to inject. For
example, injection of industrial process
waste into shallow Class V wells can con-
taminate your drinking water.
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Under the UIC Program, EPA and
the states regulate more than
400,000 injection wells.
The UIC program applies to injection well
owners and operators on Federal facilities,
Indian Lands, and on all U.S. land and terri-
tories. Most states, working in partnership
with EPA, administer their own UIC pro-
grams. If a state cannot administer the
program, or chooses not to do so, EPA
administers the program directly. The UIC
program encourages voluntary compliance
through education and technical assistance,
but penalizes owners and operators of
injection wells who violate UIC require-
ments.
How Can You Hellp?
Federal and state UIC programs help
protect drinking water resources, but must
have local support. Local governments and
citizens themselves often are in the best
position (and have the greatest incentive) to
ensure that injection wells do not endanger
USDWs, public health, and the environ-
ment. To find out more about .the UIC
program and what you can do to protect
your drinking water, contact your EPA
Regional Office.
For information contact:
Region 1
Ground Water Management Section
John F. Kennedy Federal Building
One Congress Street
Boston, MA 02203 (617) 565-3615
Region 2
Underground Injection Control Section
26 Federal Plaza, Room 853
New York, NY 10278 (212) 264-1547
Region 3 . .
Underground Injection Control Section
• 841 Chestnut Building (3WM43)
Philadelphia, PA 1910 (215) 597-9928
Region 4
Underground Injection Control Section
(GWP-3)
345 Courtland Street N.E.
Atlanta, GA 30365 (404)347-3379
Region 5
Underground Injection Control Section
(WD-17J)
77 W.Jackson Street
Chicago, IL 60604 (312) 886-1492
Region 6
Underground Injection Control Program
(6W-SE) ,
1445 Ross Avenue
Dallas, TX 75202-2733 (214) 655-7160 or
(214)655-7165
Region 7
Underground Injection Control Section
726 Minnesota Avenue
Kansas City, KS 66101 (913) 551-7369
Region 8
UIC Program/Enforcement Section
(8WM-DW)
999 18th Street - Suite 500
Denver, CO 80202-2466 (303)293-1413
Region 9
Source Water Protection Section (W-6-2)
75 Hawthorne Street
San Francisco, CA 94105 (415) 744-1838
Region 10
Ground Water Section (WD-133)
1200 Sixth Avenue
Seattle, WA 98101 (206)553-1369 •
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