United States
Environmental Protection
Agency
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Washington'DC,2Q46
June 1991
SERA Prot
11'9
Our Ground
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How Ground Water
Becomes Contaminated
Ground water becomes contaminated
when wastes and other pollutants seep
into the earth and into aquifers. Major
sources of ground-water
contamination commonly found
throughout the country include:
Hazardous waste sites
About 30,000 abandoned and
uncontrolled hazardous waste sites
have been identified nationwide, and
the number is expected to rise as
surveys continue. Preliminary studies
of 10,000 sites found some degree of
ground-water contamination at about
4,000 locations.
Other waste disposal facilities
There are approximately 93,000
landfills in the United States used by
municipalities or industries to dispose
of non-hazardous waste products and
household waste. The great majority of
these facilities are existing or potential
sources of ground-water
contamination.
Surface impoundments
This term is used to describe pits,
ponds, lagoons and other holding areas
for liquid wastes. Impoundments are
used by industries or municipalities
for receiving hazardous and
non-hazardous wastes. There are more
than 180,000 surface impoundments in
the United States. Many are located
over aquifers used for drinking water
and pose a serious threat of
ground-water contamination. In the
past, surface impoundments generally
were sited and designed without
safeguards for protecting ground water.
Storage tanks
Gasoline, toxic chemicals, process
chemicals, heating oil, chemical wastes
and other liquids of countless variety
are stored in tanks. Storage tanks are
installed above or below ground. Leaks
from either may contaminate ground
water.
Current estimates indicate there are as
many as 10 million underground
storage tanks in place across the
country. Over time, underground tanks
are subject to corrosion and fractures
that lead to leakage.
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There are approximately 2.3 million
gasoline storage tanks in the United
States. At present, there is no reliable
indication of the number that may be
leaking, but various studies estimate
between 3 percent and 25 percent are
leaking. Gasoline storage tanks, of
course, are located in virtually every
community in the country. Many were
installed in the 1950s and 1960s.
Unless they are repaired or replaced,
the number of leaking tanks can be
expected to increase.
Other major sources
of ground-water contamination
Septic tanks, used by approximately 20
million American households, handle
an estimated 3.5 billion gallons of
liquid waste per day. Septic systems
discharge high volumes of waste into
ground water. Chemical solvents used
to clean septic tanks also can
contribute to contamination of ground
water.
The use of pesticides and fertilizers on
farms and the handling of animal
waste also can result in ground-water
contamination.
Highway de-icing compounds,
accidental spills of fuel and chemicals,
waste oil used to coat roads, and
"midnight dumping" of hazardous
waste all can contribute to the total
load of contaminants reaching
ground-water supplies.
Active or abandoned coal mines and
metal mines may contaminate ground
water. The underground injection of
liquids and activities to increase
output from oil and gas wells, when
inadequately designed or operated,
may contaminate ground water.
A different kind of ground-water
contamination can occur along the sea
coast. When ground water is pumped
out faster than it is being replenished,
salt water advances into fresh water
aquifers, reducing the usefulness of
the water.
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Protecting
Our Ground Water
Lakes of every size, large rivers and
smaller streams abound across our
planet, but the largest supply of fresh
water by far underlies the earth's
surface. Ground water makes up 96
percent of the world's total water
resources. Approximately 118 million
Americans, half of the country, depend
on ground water for their drinking
water.
Once thought to be safe from
contamination, ground water is now a
threatened resource. As more incidents
of ground-water pollution are
discovered across the country, the
public has grown increasingly aware
of the potential problem of
ground-water contamination. And as
public concern has increased, so have
demands for expanded protection of
this vital resource.
Ground-Water
Facts
• Ground water is primarily stored in
aquifers—geologic formations of
permeable saturated zones of rock,
sand or gravel—that contain enough
water to yield usable amounts to wells
and springs. It does not occur as
underground oceans, lakes or streams
(except in some rare cave-type
environments).
• In general, ground water moves very
slowly. In formations containing layers
of consolidated clay with little
fracturing, ground water may move as
slowly as a few inches per year. In
strata containing unconsolidated sand
and gravel, ground water can move
800 feet or more a year. Ground water
also may move comparatively rapidly
through cavernous limestone
formations.
• Aquifers are recharged (replenished)
by precipitation seeping into the
ground or by surface waters with
which they are interconnected. In
many parts of the country, recharge
areas are close to the surface and may
be significantly affected by
agricultural, residential or industrial
activities. The depth of ground water
below the earth's surface, the depth
and type of soils above the aquifer,
and many other factors affect the
potential for contamination.
• Ground water usually discharges
(releases) to surface waters. In some
areas of the country, aquifers
contribute large quantities of water to
the flow of streams. In almost all parts
of the country, ground water is present
in sand and gravel deposits along
streams and rivers.
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• Once contaminated, ground water is
difficult—and sometimes
impossible—to clean. Because ground
water moves slowly, contaminants do
not spread or mix quickly.
Contaminants remain concentrated in
slow-moving plumes and are typically
present for many years. If ground
water becomes contaminated, the
contamination may eventually appear
in surface water.
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Ground Water and Land Use in the Water Cycle
Direction of Croundwater Movement
Human induced impacts on groundwater
Natural processes
Transpiration
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Manure spreading
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Sandstone Aquifer
Porous Sandstone Aquifer
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EPA's Ground-Water
Protection Strategy
The U.S. Environmental Protection
Agency initiated a Ground-Water
Protection Strategy in August 1984.
This strategy provides the framework
for an enhanced Federal/State
partnership in protecting this resource,
built on the principle of State control
of ground water, a tradition deeply
ingrained in our legal and institutional
history.
Under this partnership the States have
primary responsibility for protecting
and managing ground water. EPA is
responsible for regulating specific
contaminants and sources of
contamination and providing technical
and financial support to the States.
EPA's Ground-Water Protection
Strategy has four major objectives:
* To build and enhance ground-water
protection programs at the State level.
• To expand controls where
appropriate over currently
uncontrolled sources of contamination.
• To achieve greater consistency in
EPA decisions on ground-water
protection and clean up.
• To strengthen EPA's nationwide
organization for ground-water
protection.
Highlights of
EPA Ground-Water
Activities
EPA has established an Office of
Ground-Water Protection to coordinate
Agency activities under the various
laws that relate to ground water.
Similar offices have been created at the
regional level to work directly with
States.
Here are some highlights of the
Agency's ground-water protection
activities:
• EPA is developing guidelines to
define what ground water should be
protected and the level of that
protection. The guidelines will help
EPA achieve more consistent
decisionrmaking about ground water
across Agency programs.
• EPA is administering a $11 million
grant program to support State
ground-water programs and strategies.
• EPA is developing a cohesive
approach for obtaining scientifically
sound ground-water monitoring data
that EPA, State and local officials can
use in making decisions on ground
water.
• EPA issued a chemical advisory to
alert owners and operators of
underground storage tanks to the
danger of leaks and means of
detection, prevention and repair. EPA
has a nationwide survey under way to
determine the extent and causes of
leaks in underground gasoline storage
tanks. The Agency is developing
regulations for underground tanks
under 1984 amendments to the
Resource Conservation Recovery Act.
• EPA has stepped up efforts to
prevent pesticide contamination of
ground water. Manufacturers are now
required to submit data on the
leaching potential of new pesticide
products. The Agency has underway an
accelerated review of over 120
previously registered pesticides that
may have a potential for contaminating
ground water. If a pesticide is found to
pose a threat to ground water, the
Agency will take steps to ban or
restrict its use in areas at risk.
• EPA will issue technical information
documents describing successful
practices to protect ground-water
quality at the State and local level.
• An EPA-sponsored university
consortium will conduct several
symposia to stimulate and exchange
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new ideas on policies and programs
for ground-water protection.
What
Private Citizens
Can Do
The best protection for ground water is
prevention—stopping contaminants
from entering the system at the source.
Federal and State agencies have
expanded their efforts to prevent
contamination of ground water, but
private citizens also have an active
role to play. Here are some steps you
can take to help protect ground water
in your own area.
• Become familiar with your local
ground-water resources. Do you know
which aquifer supplies your
community's water system and private
wells? How many people use it, and
for what purpose?
• Become familiar with the common
sources of ground-water
contamination. Which of these
activities take place in your
community? How are they controlled?
• Find out how your community
disposes of waste products. What
waste products are used or produced
by large industries in your area? How
are toxic substances used, handled, or
stored? Is there a special program for
the disposal of household products
such as solvents, empty paint cans or
pesticide containers? Are septic tank
ordinances adequate to protect ground
water?
• Find out how extensively pesticides
and fertilizers are used in your area.
Follow label directions when you use
pesticides and fertilizers yourself.
• Learn the procedures for reporting
emergency spills or other kinds of
contamination that may threaten water
supplies. Do local agencies have
contingency plans for responding to
accidental spills or leaks of toxic
substances?
• Find out who is responsible for
managing local ground-water supplies.
Participate in local water planning and
conservation initiatives.
• Become familiar with State programs
and activities to protect ground water.
What chemicals are regulated by the
State? Does the State have a
ground-water classification system?
Has the State developed programs to
control sources of contamination?
Attend and participate in public
meetings and hearings on
ground-water issues.
• Determine if existing ground-water
protection authorities are adequate.
Find out if there are local ordinances
that provide ground-water protection.
Is there an effective enforcement
program to penalize polluters? Who
should you call to report incidents of
illegal waste disposal?
Summary
The nation's health and prosperity are
irrevocably linked to our supply of
clean, safe ground water. The key to
ensuring future availability of this
critical resource is to prevent its
contamination. Private citizens should
become familiar with the common
sources of ground-water
contamination. State and local
governments need support in their
efforts to prevent contamination from
these sources. For more information
about ground-water protection, contact
your State or local department of
natural resources, environmental
protection, or public health.
Information also is available at EPA
regional offices.
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