United States	Region VIII
Environmental Protection 999 18th St., Suite 500	August 1987
Agency	Denver, CO 80202-2405
Office of External Affairs
&EPA Mining Wastes
In the West
Fact Sheet

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Mining Wastes	v>EPA
In The West	Region VIII
Fact Sheet
A hard rock mine usually leaves behind large
amounts of wastes. In many cases, these wastes
are harmless, whether they come from the mining
operation directly or from the associated
exploration, milling, smelting, or refining.
Sometimes, however, they can harm the
environment, damage industry, and present risks
to human health. For example:
• The California Gulch flows through
Colorado's Leadville Mining District for
about seven and a half miles before joining
the Arkansas River. Located by the gulch
are numerous abandoned mines, mill tailings
piles, and slag piles left over from decades of
silver, zinc, and gold mining, milling,
smelting, and refining. The environment in
the gulch has been seriously affected by
contaminants in drainage from the old mines.
It has also been affected by the erosion of
wastes into surface water, as well as by rain
and snow melt seeping through the wastes
and running over slag piles. The flow of
water from the Yak Tunnel to the gulch, for
example, is acidic and contains dissolved
iron, lead, manganese, and cadmium. These
metals can have impacts on human health.
The water also contains sulfates, calcium, and
dissolved solids, which can damage the
environment and limit downstream water use.
Contamination from the gulch has killed fish
in the Arkansas River. It threatens livestock
and crops grown on land irrigated by river
water.
•	At Smuggler Mountain, near Aspen,
Colorado, there are many old silver and lead
mines that were active mainly between 1879
and 1920. The mining wastes, mill tailings
(400,000 cubic yards, scattered over 75
acres), and smelter by-products left behind
at Smuggler Mountain contain high
concentrations of lead and other metals
potentially hazardous to human health.
Some of these wastes have been used as fill
material for building foundations and road
construction. High concentrations of lead
have been found in vegetables grown in soil
from the site.
•	A lead and zinc smelter has operated in East
Helena, Montana, since 1888. Throughout its

Photograph: Yak Tunnel

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history, the smelter emitted particles of lead,
cadmium, and arsenic to the air. These
particles contaminated the soil on which they
landed over an area of 8.4 square miles.
The contaminants may be swallowed by
children playing on this soil, and they may
also be eaten by livestock and absorbed by
crops.
In many cases, as noted, mining wastes do not
cause these kinds of problems. People living
nearby do not need to be concerned about their
health. The mining wastes probably have some
environmental effects, but not of great
consequence.
The purpose of this fact sheet is to explain what
makes some mining wastes a problem, but not
others. The fact sheet also explains what can be
done to reduce or remedy the problems. There
are many types of mining wastes, but the focus
here is on wastes from mining for metals in the
West, as in the three cases above. Surface
mining for coal, for example, is not addressed
directly here.
Contamination of Streams, Ground water, Air
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People can breathe dust, drink polluted water, eat contaminated crops. They can also come
into direct contact with wastes.
WHY CAN MINING WASTES CAUSE
PROBLEMS?
Mining wastes can cause problems because they
may contain metals such as cadmium, arsenic, or
lead that can be harmful to human health. These
and other contaminants in mining wastes may, in
addition, affect the environment. They can cause
damage over large areas, making streams and
ground water unusable, harming wildlife and
natural resources and, in turn, crippling fishing
and agricultural industries.
There is little risk to health so long as the metal
traces and contaminants remain confined to the
wastes and do not come into contact with people
or the environment. Contaminated dust blown
from a waste pile may, however, be breathed by
people living nearby. Waste materials may be
used in construction or carried to backyards and
used in gardens and sandboxes, where children
may swallow contaminants. Most important, water

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from rain or snowmelt can seep through or run
off a waste pile and carry contaminants to lakes,
rivers, ground water, and pasture lands, damaging
the environment and exposing people to
hazardous substances through the water they drink
(and, to a lesser extent, through the food they
eat). Even if human health is not at risk, the
ground water may become polluted by dissolved
solids and chemicals used in processing.
It is important to understand that you cannot tell
just by looking at a waste pile or, in most cases,
even by knowing its source whether water seeping
through the waste is carrying off metals and other
contaminants. An overburden pile, a tailings pile,
a smelter slag heap or a pile of flue dust that is a
problem, in this respect, will look no different
from one that is harmless. The difference lies in
chemical reactions that may or may not take
place in a particular waste pile.
Specifically, mining wastes often contain "pyritic"
or sulfur-containing minerals (sometimes called
"fools gold") that, when exposed to oxygen,
water, and bacteria, can form acidic solutions.
The acidic solution can mobilize metals remaining
in the wastes, causing water flowing through the
wastes to pick up higher concentrations of
potentially hazardous metals. Depending on the
exact chemical nature of a particular waste pile
and the ground beneath the pile, however, acid
may or may not form, and the waste may or may
not present a problem. The way in which the
wastes are handled may also be a factor.
Sometimes acid can form but be neutralized
before the solution presents a problem.
There are two noteworthy consequences. First, a
waste pile that has been harmless all along may,
at some time, undergo changes that cause it to
pose risks to human health or the environment.
HOW CAN YOU PROTECT YOURSELF?
It is easy to protect yourself and safeguard
your health, even if you live close to a
mining site that has been recognized as a
source of contamination.
1	Do not allow your children to play
around overburden piles, mill tailings
piles, tailings ponds, flue dust piles, or
slag heaps.
2	Do not bring tailings or other wastes
back to your home to use in your
garden or sandbox.
3	Do not grow fruits or vegetables in a
garden already containing mining wastes.
4	Do not bring mining wastes back to your
home to use as fill or for other
construction projects.
5	If you have a well near a mining site,
have your well water tested about every
one to three years for contamination. If
your water starts to become discolored
8
or to smell between tests, contact your
local health department.
Use good housekeeping practices: dust
and vacuum often, remove dusty
clothing, wash children's hands often.
Consult your doctor if you have any
suspicions about your or your children's
health. Your doctor can tell you what
symptoms are associated with exposure
to mining wastes.
Follow any additional recommendations
provided for a specific site.
Because it may be very difficult (and take
a great deal of time) to remedy mining
waste problems, the best way to be sure
those problems do not have any effects on
your health is to limit your exposure to the
wastes by following these
recommendations.

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The changes may not be visible and their
occurrence can be very difficult to predict.
Second, the only way to determine whether the
water running off a particular waste pile will be
acidic and contain metallic contaminants is to
examine carefully that waste pile and its runoff.
That makes mining wastes different from typical
industrial wastes. There are other differences as
well. Some petrochemical wastes, for example,
may be very hazardous to human health in small
quantities, which is rarely true for mining wastes.
The quantities of overburden, tailings, and slag
produced in mining and ore processing, however,
can be enormous.
Thus, in short, whether mining wastes do or do
not present problems depends on the type of
waste, how it has been handled, the type of metal
or mineral being mined, and the site of waste
disposal. Mining wastes at each site must be
judged individually to identify problems. Overall,
there are probably no more than 1,500 mining
waste sites in the U.S. that could present
hazardous waste problems and 100 or so that may
require remedial action. In the West, many of
these sites are mostly located in unpopulated
mountain areas.
WHAT ARE THE RISKS TO HUMAN
HEALTH AND THE ENVIRONMENT?
Mining wastes consist mostly of rock, soil, and
other inert materials that are not harmful in
themselves to human health. As noted, however,
they often do contain zinc, iron, cadmium,
arsenic, lead, as well as copper, molybdenum,
selenium, manganese, cadmium, mercury, and
chromium, metals that may be toxic, that is,
poisonous, to humans, animals, or plants. Some,
such as lead, are poisonous to humans when
inhaled or ingested (swallowed). Others, such as
cadmium, arsenic, and some forms of chromium,
are believed to cause or contribute to cancer
when inhaled or ingested in small quantities over
many years. Ground water contaminated by such
metals, even if not a threat to human health, may
be unusable for drinking or irrigation.
The precise effects of exposure to the toxic
contaminants released from mining wastes can
vary greatly, depending on specific circumstances.
By what means was someone exposed to the
contaminants? How much, and for how long?
Metals, for example, may be very toxic when
inhaled and much less toxic when swallowed.
Metals such as zinc are valuable or even
necessary to human health in small quantities. In
what physical condition was the person? Very old
people, the very young, and those in poor health
are likely to face greater health risks. Previous
chemical exposures (or contact at the same time
with hazardous substances from other sources) will
also affect the health risks involved.
Consequently, it is very difficult to predict the
health effects of contact with air or water
contaminated by toxic metals from mining wastes.
There is a great deal of uncertainty in this area,
and studies are still underway. The potential
contribution of contamination from mining wastes
to cancer and other serious human health effects
is, however, cause for concern.
The risks mining wastes pose to the environment
come primarily from the dissolved metals, acid,
and process reagents, as well as sulfates, dissolved
solids, calcium, sodium, and other contaminants
in water running off or draining from wastes.
During the spring snowmelt, for example, large
volumes of acidic, metal-contaminated runoff
from tailings ponds and rock piles have
contaminated pasture lands and streams, causing
illness in cattle and sheep. Fish kills have been
reported. In some cases, the combination of
acidic water and silt carried along by mining waste
runoff has destroyed the food supply for fish,
making the water uninhabitable and driving fish
from mountain streams for many miles. These
effects may occur rapidly, or they may build up
over a period of years.
HOW CAN THE PROBLEMS BE
REMEDIED?
There is much that can be done to prevent
mining wastes from turning into environmental
problems. The mining industry is becoming

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increasingly experienced in the careful handling of
wastes. Once a problem has developed, however,
it may be very difficult to remedy.
There are several ways of stopping the leaking of
contaminated water from an overburden or tailings
pile. One is to haul all the wastes away from the
site, along with any contaminated soil from
underneath the wastes, and dispose of the wastes
in a different, but safer, location. This can be a
very expensive course of action because of the
enormous quantity of wastes that may need to be
removed. For example, there are about
7,000,000 tons of tailings at the Eagle Mine in
Colorado.
Another course of action is to push the wastes
back into the mined-out area from which they
came (when the wastes are located close enough
to the pit), then cover the filled pit with soil,
grade, and revegetate.
An alternative is to use waste pile control
measures. Dikes, dams, berms, or trenches can
prevent surface runoff and run-on. Site drainage
systems, pits, ponds, or lagoons can be used to
collect runoff and run-on for treatment.
Any of these actions may, however, be worse than
simply leaving the wastes in place with controls to
prevent erosion and water runoff. Moving and
hauling wastes can raise dust full of contaminants,
creating greater exposure risks than presented by
the undisturbed wastes.
Contaminated, acidic water leaking from old
mines and mine tunnels may be especially difficult
to address. One possibility is to collect the
drainage and treat it to remove any contaminants.
Sometimes, however, the flow of water from a
mine may be too great to permit cost-effective
treatment. An alternative is to try to plug the
shafts and holes from which the water is escaping.
Doing so, however, may cause the water to
escape somewhere else. There may even be a
blowout, quickly releasing a large amount of
contaminated water. Plugging may also force
some contaminants to flow out with ground water
through the bedrock. Another alternative—but
an expensive one—is to backfill a mine with
alkaline material that can neutralize any acid
formed.
One way to limit the amount of contaminated
water flowing from a mine is to prevent the water
from getting into the mine from the surface. This
approach may not be successful, because generally
water enters a mine by seeping in from
surrounding bedrock.
In general, because each mining waste site is
different, the choice of action depends on the
specific nature of the site and the type and extent
of its contamination. It may take some time to
conduct careful studies of a site to identify the
best course of action.

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WHO CLEANS UP?
If a mining, milling, or smelting site is old
and long abandoned, but endangers hu-
man health or the environment, who can
clean it up?
Congress has enacted a number of laws
that authorize the federal government to
take action, in certain circumstances, to
remedy environmental problems connected
with mines and mining wastes. States may
have their own programs or can use the
federal laws. One of the most important
of these laws is Superfund. Under Super-
fund, the U.S. Environmental Protection
Agency (EPA) can study the extent of a
mining waste problem and, so long as ac-
tion is clearly necessary and the costs are
not excessive, clean up the site, halt the
spread of contamination, or otherwise
remedy the problem. Alternatively, EPA
can take legal action to compel the com-
panies or individuals responsible to clean
up the site.
Not all mining waste sites may be eligible
for Superfund acuon. Those that are, and
that are relatively serious compared with
hazardous waste sites elsewhere in the na-
tion, are placed on the National Priorities
List (NPL). In the 1986 Superfund
Amendments, Congress directed EPA to
revise its procedures under the Hazard
Ranking System (HRS) for evaluating the
threat to human health and the environ-
ment posed by sites. EPA has 18 months
to amend the HRS to assure that it accu-
rately assesses the relative degree of risk
posed by sites.

While these procedures are being revised,
EPA must consider some additional factors
before facilities containing significant quan-
tities of mining wastes can be listed on the
NPL. The factors to be considered in-
clude: the extent to which the mining
waste affects the HRS score; available in-
formation as to quantity, toxicity, and con-
centration of the hazardous substances;
the extent or poternal for release, expo-
sure or potential exposure; and the degree
of hazard posed by the hazardous con-
stituents at such a facility.
The three sites described at the beginning
of this fact sheet are already on the NPL,
along with other mine, mill, and smelter
sites, and streams and a reservoir in which
mill tailings have accumulated. Consider-
able study may be required before the
government can determine what type of
action, if any, should be taken at a NPL
site.
A Superfund action may be paid for by
private firms that, under the law, are re-
sponsible for the sixe. For example, the
company that owned or operated a mine
in the past may still be liable for that
mine, even if the mine is inactive and
abandoned. Usually, a company can be
linked to each major mining waste site.
The companies mar even take the lead in
cleaning up the site, under negotiated
agreements enforced by EPA. As a re-
sult, most Superfund actions at mining
waste sites are expected to be joint efforts
by the government and industry.

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DEFINITIONS
Mining wastes, in general, include wastes
from the mining, milling, smelting, and
refining of ores and minerals.
Milling is the physical processing of raw ore
by breaking, crushing, grinding, or flotation
to concentrate the ore and make a product of
a certain size for further processing.
Smelting is the heat treatment of an ore to
separate the metal portion from the waste
slag.
Refining is a separation process that
removes waste from ore mixtures to yield a
purified concentrated product. Metal
refining can include physical and chemical
processes.
Overburden or spoil is the waste rock
removed in exploration or mining to reach
metallic ore.
Tailings are waste materials separated from
the mined ore by washing, crushing, and
other processing in mills. Tailings are
usually powdery or fine-grained and may
contain residual process chemicals. They are
discharged from mills, mixed with water, into
large ponds, but when the ponds dry up, the
tailings can be formed into piles.
Slag is the waste removed from the ore in
smelting. Slag piles may also contain dust
and sludge removed from smelter smoke to
reduce air pollution.
Flue dust is the fine-grained airborne solid
particles that come from the stack of a
smelter. The chemical make-up of the dust
is very site-specific and will depend mainly
on the geochemical make-up of the ore body
and the smelting process being used. Flue
dust may contain large amounts of arsenic,
copper, silver, and lead.
Leach piles are piles of ore from which
metals are extracted by dumping a chemical
on the pile and letting it drain through the
pile, leaching metal from the ore. The metal
can then be recovered from the chemical
solution.
Process reagents are chemicals such as
sulfuric acid or sodium cyanide that are used
in processes such as leaching to aid in
extracting metal from ores.
Acid mine drainage is water issuing from a
mine that has mineral acidity from oxidation
of exposed metallic sulfides and dissolved
metals. The source of the water can be
seepage from ground water or surface runoff.
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