United States	Region VIII
Environmental Protection 999 18th St., Suite 500	August 1987
Agency	Denver, CO 80202-2405
Office of External Affairs
Mining Wastes
In the West:
Risks and Remedies
Overview

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This overview supplements EPA Region VIII's fact sheet on mining wastes by describing, in greater detail,
the potential risks hard rock mining wastes may pose to human health and the environment. It also notes
the consequences of the special characteristics of mining waste sites for decisions about remedial actions
under the Superfund program.
Mining Wastes

In The West:
Region VIII
Risks and Remedies

Overview

Introduction
A hard rock mine generally produces large
quantities of wastes. In addition to the
overburden or spoil removed during the mining
operation itself, there may be large piles of
tailings, slag heaps, and flue dust from the
beneficiation process. A large portion of these
wastes present little risk to human health. They
will probably have some environmental impacts
(dust, for example), but in many cases, only of
small consequence.
Sometimes, however, mining wastes can present
serious problems. They may pose significant risks
to human health. In addition, they may endanger
plant and animal life, causing environmental
damage over a vast area. Even when health is
not at risk, contaminants from mining wastes may
render ground water unusable.
The U.S. Environmental Protection Agency
(EPA), Region VIII, currently estimates that
between 800 and 1,500 mining waste sites in the
U.S. may need to be assessed to determine
whether they pose threats to public health and the
environment because of hazardous substances.
Overall, between 70 and 100 mining waste sites
may eventually require remedial action to address
public health and environmental hazards. In the
West, however, many of these sites are mostly in
unpopulated mountain areas.
It must be emphasized that what makes some
mining wastes a problem depends on a
combination of factors that vary substantially in
each case, including the type of metal or mineral
being mined, the specific composition of the
waste, and the disposal site. Chemical changes
may cause one waste pile to pose far greater
hazards than another, seemingly identical, waste
pile, which may remain comparatively innocuous
even if it is an eyesore. Each mining waste site
must be evaluated individually to determine
whether there is a problem.
As noted, the purpose of this overview is to
provide detail on the potential risks hard rock
mining wastes may pose to human health, as well
as to the environment and to natural
resource-related industries. In describing risks,
the overview explains why some but not most
mining wastes present problems. There is also a
discussion of techniques for reducing or remedying
problems once they have occurred.
The final section of this overview explains the
consequences of the distinctive features of mining
wastes for decisions about remedying mining waste
problems under the Superfund program. Mining

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wastes are distinguished from the industrial wastes
(e.g., petrochemical wastes) more typically
addressed under Superfund by the generally low
toxicity of the wastes, but the enormous quantities
of wastes that may be present at a site. For
example, approximately 7,000,000 tons of tailings
are thought to be present at the Eagle Mine site
in Colorado; the Anaconda Smelter site stretches
over 6,400 acres. The area damaged by
contamination from mining wastes may also be
extensive. These features are central to
understanding the problems associated with mining
wastes.
The focus of this overview is on hard rock mining
for metals in the West, and the milling, smelting,
and refining operations commonly located at or
near these mines. Even though much of the
discussion applies equally to other types of mines
and to other parts of the country, problems
associated with other types of mining—surface
mining for coal, in particular—are not addressed
directly. An exhibit below lists the types of
mines, including hard rock mines, found in the
West.
Risks to human health
The risks to human health from mining wastes
depend upon four important conditions, as with
other environmental contamination incidents.
First, there must exist a potential for the release
of the waste or its constituents to the
environment. Second, once contaminants are
released, one or more mechanisms for
transporting them through the local environment
must be available. Third, there must be a
potential for human exposure. That is, the
transport mechanism or mechanisms must bring
the waste or its constituents to a location where
human contact will occur. Finally, the risk to
human health depends upon the toxicity of the
waste constituents, or their ability to have a
deleterious effect on the normal biochemical
processes of the body. In the discussion that
follows, each of these factors is addressed in turn.
Chemical Releases
The overburden excavated at hard rock mining
sites often contains sulfur in the form of metallic
sulfide (for example, iron sulfide, known
commonly as pyrite or "fool's gold"). When the
sulfide is exposed to oxygen, moisture, and
certain bacteria, it is oxidized to sulfuric acid and
iron hydroxides (rust). As the acidic solution
contacts other rocks and soil, metals are
dissolved, a phenomenon known as leaching, and
are released in surface runoff that may originate
with heavy rains, spring snowmelt, or seepage
through waste piles. As the acidity of the water
increases, metals are more readily leached and
metal concentrations in the surface or ground
water increase. In this manner, runoff and
seepage containing metals (some of which can be
toxic) and other constituents are released to the
environment from mining overburden and tailings
piles. The rate of release and, in turn, the
degree of hazard or risk, is governed by the
sulfide content of the rock, the availability of
oxygen, the amount of readily oxidized minerals,
the quantity of water moving through the waste,
and the pH of the leachate. Chemicals remaining
from certain milling processes can add to the
chemical reactions that will take place for decades
after a tailings pond or pile is formed. Acid
formation may also occur when inert sediments
come into contact with ground water.
The rates of acid formation and leaching of
metals in a waste pile are functions of- the nature
of both the waste pile matrix and of the ground
underlying the pile. For example, if the waste
rock or underlying ground strata are alkaline
(such as limestone or sandstone with carbonate
cementation) with adequate buffering capacity, the
leachate could be neutralized. Neutralization will
result in precipitation of the metals, thereby
immobilizing them. The result will be a solution
with an elevated total dissolved solids content. In
addition, the permeability, chemical composition,
and sorbitive qualities of underlying soils might
cause dissolved metals to be attenuated, reducing
their movement. In short, chemical releases will
vary significantly from site to site.

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Transport and Human Exposure
Once released to the environment, toxic metals
from mining wastes may be transported to human
receptors by several different mechanisms. Both
water and air serve as transport media. Initially,
metals may be dissolved and carried away from
mining sites by acidic surface runoff. This runoff
may enter streams, lakes, or reservoirs and, when
flooding occurs, may contaminate soil on nearby
fields and pastures. Plants may absorb the toxic
metals in the soil through their roots. The result
can be exposures to grazing livestock, or to
humans when the contaminated acreage is used
for growing human food crops.
Surface water, seepage, or leakage from tailings
ponds containing toxic metals may also percolate
through soil or sediment underlying waste piles,
tailings ponds, or contaminated rivers, lakes, and
ponds, and enter the shallow ground water. The
impact on ground water is often mainly an
increase in constituents not known to be toxic,
such as calcium, magnesium, sulfates, or dissolved
solids. These constituents may be in large enough
quantities to make the ground water unusable for
drinking or other purposes without some
treatment. In some cases, however, there may be
increased levels of toxic substances while the
levels of mainly nuisance constituents (e.g.,
dissolved solids) remains low. This contaminated
ground water may be pumped to the surface for
drinking, resulting in human exposure to toxic
metals via ingestion. As the metal-containing
water moves through the soil toward ground
water, toxic metal concentrations may decrease
because the metals react with and adhere to soil
particles. Nonetheless, potentially hazardous
concentrations of toxic metals have been
measured in ground water consumed by some
communities living near mining sites.
Toxic metals may also be carried away from
mining sites by high winds as particulates or
contaminated dust. Rock and tailings piles can be
eroded by wind; the wind may carry small
particles of dust and toxic metals to populations
living downwind. At some sites, decreased
visibility has been noted downwind from large
tailings piles as metal-containing dust is blown
towards nearby towns. The result is human
exposure to toxic metals via inhalation, or the
breathing of contaminated air. For certain
metals, such as cadmium, this route of exposure
can be particularly dangerous. Metals have also
been deposited in soils surrounding smelter
operations from years of smokestack and fugitive
dust emissions.
Direct contact is another important mechanism by
which toxic metals may be transported from
mining wastes to people. Direct contact exposures
may occur when people come into contact with
soil or water (rivers, lakes, ponds) contaminated
by metals released from mining sites. Exposures
may also occur when people use materials from
tailings piles in gardens or sandboxes. Direct
contact exposures may result in inhalation or
ingestion of contaminated dust (for example,
when children swallow contaminated soil on which
they have been playing). Although these
exposures are periodic (rather than continuous as
when people are exposed to contaminated air or
drinking water for long periods) and involve only
small quantities of toxic metals, after a period of
many years concentrations of lead or cadmium,
for example, may accumulate in the body leading
to increased health risks.
Chemical Toxicity
The toxic effects of metals vary depending upon
the metal and upon the level and duration of the
dose (that is, the quantity of metal ingested or
inhaled and the time period over which the
exposure is experienced). Toxic effects may be
experienced almost immediately following large
doses of short duration. Scientists refer to such
effects as acute effects. Alternatively, the effects
may be subtle in their appearance and noticeable
only after many years of exposure to low doses.
These effects are referred to as chronic effects.
All toxic metals, and in fact all chemicals, are
capable of causing both acute and chronic effects.
The doses and exposure durations that cause
acute and chronic effects vary substantially from
chemical to chemical.
It is important to note that the designation of an
effect as chronic or acute does not give an

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indication of the severity or seriousness of the
effect. For example, both temporary sneezing
and watering of the eyes (a minor, reversible
effect) and death by poisoning (obviously an
irreversible consequence) may be called acute
effects. The most commonly studied chronic
effect, cancer, develops slowly and may not be
observed until many years after the most
important causative exposures have occurred.
Concerns are therefore greatest for exposures that
cause life-threatening irreversible effects. Human
exposures to toxic metals from mining sites
generally involve relatively low doses experienced
over much or all of an individual's lifetime. The
concern is therefore related to the risk of possible
chronic but perhaps life-threatening effects
resulting from exposure through contaminated air
or water.
Of the many metals that appear in wastes from
mining sites, four—lead, arsenic, cadmium and
chromium—are commonly occurring and of
special concern because they are thought to have
serious human health consequences. Several
others, notably copper, zinc, nickel, molybdenum,
and magnesium, are also of some concern.
Chronic, low-level exposures to lead are known
to cause decreased production of hemoglobin (the
substance in the blood that carries oxygen), which
results in anemia. Lead accumulates in the body
over time as exposure continues, and in severe
cases, brain damage and death may occur.
Children are far more susceptible to lead
poisoning than adults because they absorb far
greater quantities of lead than adults once the
lead has been ingested. Lead exposures have
been observed and studied at mining and smelting
sites in the past. Exposures at such sites as the
East Helena site in Montana generally have not
been high enough to cause serious lead poisoning.
Nevertheless, concern for elevated blood lead
levels and the potential for anemia in children
remains an important consideration.
Studies of workers exposed to arsenic show that
this metal can damage the respiratory system and
can cause skin lesions, cardiovascular, and
vascular disorders. Arsenic is considered by
experts to be a human carcinogen and it is this
effect which is of concern relative to mining
wastes. Arsenic is thought to cause skin, liver,
and colon cancer as well as leukemia in humans.
While the carcinogenic effect of arsenic has been
observed as a result of both ingestion (specifically
related to contaminated ground water) and
inhalation (observed in occupational settings), the
carcinogenic potency of arsenic is estimated by
some to be approximately one order of magnitude
greater when the metal is inhaled than when it is
ingested. Dust from tailings piles inhaled by
individuals living nearby is therefore of paramount
concern.
Cadmium, although found in mining wastes less
frequently and usually in lower concentrations
than arsenic and lead, may also pose some serious
health risks. Once in the human body, this metal
is most likely to damage the lungs or kidneys.
Chronic inhalation of cadmium is known to cause
an emphysema-like condition. This effect
generally involves higher exposure concentrations
of cadmium than are found in the ambient
environment near mining sites. Workers exposed
to cadmium in the workplace, however, may
become more susceptible to the disease if
environmental exposures occur as well. The
kidneys are very sensitive to cadmium because the
metal tends to concentrate in kidney tissue.
Damage likely to occur includes kidney
malfunction and renal tubular damage. Such
effects have been observed in communities
exposed to highly contaminated drinking water.
Inhalation of cadmium dust is known to cause
increased occurrence of prostate cancer in
workers. Inhalation exposures are therefore an
important concern at mining sites.
Chromium, in its most oxidized state, is known to
cause lung cancer in humans. Chromium is also
known to be a skin irritant and, when ingested in
high doses, can irritate the gastrointestinal tract
and cause circulatory shock and kidney damage.
To date, no evidence of a carcinogenic effect
from ingestion of chromium has been found.
Like cadmium, chromium occurs less often and in
lower concentrations than lead and arsenic at
mining sites. Its known ability to cause cancer,
however, is cause for concern, especially with
respect to inhalation and direct contact exposures.

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The toxic effects to humans of copper and zinc
occur only at relatively high exposure
concentrations unlikely to result at mining sites.
Zinc, an important nutrient needed in very small
quantities, can cause copper deficiency disease
(copper is also an essential nutrient) in humans,
when ingested in relatively large doses. Other
metals known to occur at mining sites, such as
cadmium, molybdenum, and magnesium, cause
this effect as well. This illness has also been
observed in livestock grazing near mining sites and
is discussed further below. Nickel, which occurs
only rarely at mining sites, is known to be
carcinogenic when inhaled in concentrations much
higher than those likely to be found at most
mining sites.
The actual risks to human health from exposure
to wastes or waste constituents from mining sites
are impossible to express in general. Many
site-specific factors, as well as the health and
other characteristics of the exposed populace are
important in determining risk. Evidence of
human illness related to workplace and
environmental exposures to the same toxic metals
found at mining sites has led to concern over
water and air contamination and the potential
long-term health implications.
Risks to the environment and to industry
Contaminated surface water runoff from mining
waste sites has been known to cause extensive
damage to the environment—damage that has
been much more dramatic and visible than the
impacts to human health. This discussion
addresses damage to freshwater communities (fish
and other organisms living in lakes and streams),
plants, and livestock that has been documented
near mining sites. Some of this damage has been
mitigated in recent years. Water quality in rivers
once seriously polluted has shown noticeable
improvement. It is important to note, however,
that scientists do not now understand the full
range of consequences associated with these
pollution incidents. Subtle and potentially lasting
environmental damage may remain after the
obvious damage has been alleviated. Moreover,
these lasting consequences may pose some small
risks to human health.
Damage to fish and other organisms in lakes and
streams is usually due either to highly acidic
conditions, to dissolved toxic metals, or to
excessive sedimentation that occurs when eroded
soil and silt are carried in large quantities by
surface water runoff to lakes and streams.
Accumulation of some metals in fish tissue is a
potential problem that may contribute to human
health risks through the food chain.
Highly acidic water is corrosive to all living tissue.
Fish and other organisms therefore cannot live in
water that has been so heavily contaminated that
the pH has dropped to levels well below neutral.1
In most cases, fish are able to recognize and
avoid areas where the water has become very
acidic. In such areas, fish populations become
smaller over time until they disappear entirely.
Other organisms also move if they are able or die
off until, in extreme cases, the lake or stream
section supports no life whatsoever. At sites such
as the Eagle Mine in Gilman, Colorado, this type
of damage has destroyed important sport fisheries.
In some cases, the fish population may be
prevented from leaving areas of high acidity by a
physical barrier. Under such circumstances, a
sudden influx of highly acidic drainage
contaminated with metals can cause massive fish
kills. This situation occurred at the White Mill
site near Helena, Montana, where a fish kill
damaged a sport fishery in Silver Creek.
1 pH is measured on a scale of zero to 14. At a pH of seven, water is neutral, that is, neither acidic nor
basic. Below pH seven, water becomes increasingly acidic. At a pH of less than three, water can be
dangerously corrosive. Above pH seven, water becomes increasingly basic. Highly basic water (pH 12 or
more) can also damage living tissue.

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The effects of eroded silt and soil carried by
runoff from mining waste sites are somewhat more
complex. As eroded materials are carried into
lakes and streams, the receiving water becomes
laden with particles that block out light. Initially,
this condition reduces the population of algae, the
tiny single-cell plants that live in water and serve
as the principal food source for other small
organisms at the base of the food chain. The
reduced water clarity is an undesirable condition
for some fish (such as trout species that prefer
cold, clear water) and can cause fish populations
to avoid the area.
In time, the suspended soil and sand particles are
deposited on the bottom of the lake or stream
and cover rocky stream beds or other specialized
conditions that serve as a home to important
freshwater insects. Because these insects are an
important food source for young fish, conditions
become even more undesirable and fish
populations are further distressed. In Colorado,
heavy sedimentation has damaged fish populations
and other aquatic life at the Central City Mining
sites, at the Argo Tunnel and Mill in Clear Creek
County, in the California Gulch near the Yak
Tunnel (Leadville), and at the Carbonero Mine
and Red Mountain Creek sites in San Miguel
County. Similar damage has occurred at the
Comet Crystal, Big Chief, Bertha, and Mascot
Mine sites in Jefferson County, Montana; and at
the Boulder Creek site, the Philipsburg site, and
the Moonlight and Wasa Mine sites in Granite
County, Montana. Many other cases have been
documented as well.
Livestock grazing near mining sites can be
exposed to vegetation, soil, and water that may be
contaminated with toxic metals. Reports of cattle
experiencing illness have been noted at several
sites. The most commonly reported mine waste
related illness in cattle is copper deficiency
disease. This disease occurs as a result of
exposure to unusually high levels of zinc,
cadmium, molybdenum, or magnesium in water,
grass, or soil. When cattle are exposed to high
zinc levels, their ability to retain adequate levels
of copper, an essential nutrient, is reduced. The
resulting copper deficiency can be treated if
properly diagnosed.
Soil and water contaminated by mining wastes
have also been linked to dying vegetation at
mining sites. For example, at the Corbin Flats
site, an abandoned hard rock mine in Jefferson
County, Montana, vegetation has been destroyed
on nearly 80 acres of land that might otherwise be
used for grazing. At the Silver Mountain Mine
site near Empire, Colorado, low plant" diversity
and density (indices used by scientists to measure
the quality of plant communities) have been noted
near the mine site. The area is an important
wildlife habitat and serves as a migration corridor
for big game populations.
Ground water in the vicinity of many mining waste
sites has been contaminated by sulfates and
dissolved solids to the point of being unusable,
even though the contaminants do not pose known
toxic threats to humans. Thus, there may be
damage to natural resources (and, in turn, to the
industries, such as agriculture, dependent on
them) independent of the potential for adverse
effects on human health.
Feasible remedies
There is much that can be done to prevent
mining wastes from turning into environmental
problems. For example, among the most effective
preventive techniques is to locate waste sites away
from streams so that the likelihood of surface
water contamination is reduced. Once a problem
has developed, however, it may be very difficult
to remedy. This section sketches some possible
techniques for remedying various types of
problems.
Contaminated water leaking from an overburden
pile or tailings pond is generally addressed in one
of several ways. The wastes and soil underlying
the waste can be excavated and moved to
different and safer locations. This can be a very
expensive course of action because of the
enormous quantities of wastes that may need to
be moved. Under certain circumstances,
however, it can prove to be a feasible remedy.

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For example, at the Lincoln Park site in Canon
City, Colorado, tailings deposited in unlined ponds
have been transferred to new lined ponds nearby.
This action may end discharge of contaminants
to ground water. Another course of action is to
push the waste back into the mined-out area from
which it came (if the wastes are located close
enough to the pit), cover the filled pit with soil,
grade, and revegetate. This option must be
carefully planned so as to protect against possible
future discharges of contaminants to ground water.
An alternative is to address contaminated surface
runoff and run-on by implementing waste pile
control measures, such as (a) surface diversions
(berms, dikes, dams, trenches) to prevent runoff
and run-on, (b) site drainage systems to collect
contaminated water, or (c) pits, ponds, or lagoons
to contain contaminated runoff and run-on for
treatment by neutralization, precipitation, or other
techniques.
In any case, consideration must be given to the
possibility that the remedy may be more
detrimental to the environment than simply
leaving the wastes in place and adding erosion
and dispersion controls. Moving and hauling
wastes can raise dust contaminated with heavy
metals, creating greater risks of exposure than
presented by the undisturbed wastes.
Contaminated and acidic water leaking from old
mines may be especially difficult to address. One
possibility is to collect the drainage and treat it to
remove any contaminants. Sometimes the flow of
water from a mine may be too great to permit
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, perhaps causing more
harm than before. One way to limit the amount
of contaminated water flowing from a mine is to
prevent the water from getting into the mine.
This approach may not often be successful,
because water generally enters a mine by seeping
in from the surrounding bedrock.
Some remedial measures now under consideration
for mining waste sites emphasize improved
containment or isolation of the wastes. Dams
have been proposed at several sites to contain
tailings ponds. At the Olson/Niehart Reservoir in
Utah, one proposed remedy involves building a
dam and reservoir immediately downstream froiri
the mine to contain the tailings and prevent
surface water quality degradation. A similar
remedy has been considered for the Mayflower
tailing site, also in Utah.
In cases involving the contamination of drinking
water sources, such as the Milltown Reservoir,
alternate drinking water sources have been
provided. Where soil has been contaminated by
emissions from smelters (e.g., the Dallas Lead
Smelters), the soil has been excavated, removed,
and replaced. Erosion, runoff, and run-on
problems at mining sites can also be remedied by
diversions, drainage control, capping, regrading,
and re vegetating.
In summary, there are numerous possible
techniques (and combinations of techniques) to
remedy the problems associated with mining
wastes, but many are rendered technically
infeasible or not cost-effective by the large
quantities of wastes usually involved (a feature
highlighted in the next section). The choice of
remedy, therefore, must be determined on a
site-specific basis; there is no standard or
"textbook" solution to any mining waste problem.
Decisions for Superfund
Mining waste problems may, in certain
circumstances, be remedied under authority of the
Comprehensive Environmental Response,
Compensation, and Liability Act of 1980
(CERCLA). CERCLA, commonly called
"Superfund", provides funding and authority for
the federal government, or state governments
acting in its place, to respond to releases (or
substantial threats of releases) of hazardous
substances, pollutants, or contaminants into the
environment. CERCLA also establishes a liability
scheme under which private parties may be
assigned responsibility for a release and required
to cover the costs of response. Thus, under
Superfund, the government may take legal action
to recover its response costs from the responsible
parties. Or as an alternative to direct government
action, private responsible parties may be

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compelled through administrative orders or
judicial action to conduct a cleanup. EPA has
the lead role in the federal Superfund program.
Superfund remedial actions, which are intended to
yield permanent solutions to hazardous waste
problems, may be conducted only at sites
identified as national priorities, based on
comparison with hazardous substance releases
elsewhere. As of the summer of 1985, 38 mining
waste sites in the U.S. have been included on, or
proposed for, EPA's National Priorities List.
Twenty-four of these sites are associated with
mining and milling; the remining 14 are associated
with smelting and refining. It is estimated that
from 70 to 100 mining waste sites could
eventually be placed on the NPL. Superfund
remedial actions are already underway at several
mining waste sites.
It is important to recognize that the unusual but
distinctive features of mining waste sites
necessitate unusual and complex decisions about
Superfund responses. To a significant degree, the
Superfund program is oriented towards responding
to releases of hazardous petrochemical-based
substances from inactive or illegal landfills,
impoundments, and drum dump sites, the kinds
of releases that predominate in the East, the
Pacific Coast, and other areas where the
petrochemical industry is concentrated. To the
extent that mining waste sites differ from these
more-characteristic sites, they may be difficult to
integrate within a consistent national response
framework, and they may raise issues
policy-makers rarely face with responses in other
parts of the country. The Superfund
Amendments and Reauthorization Act (SARA) of
1986 recognized some of the special problems
associated with mining waste sites and included
provisions to assure consideration of certain
mining site characteristics in listing such sites on
the NPL. Some of the typical features of mining
waste sites important in this regard are the
following.
1 The volumes of wastes involved are enormous
and may extend over a large area.
Consequently, the cost of removing wastes
and contaminated soil for disposal off the site
may be prohibitive, especially for Superfund
financed actions in light of the need to
conserve Superfund monies for responses at
other national priority sites.
2	The toxicity of mining wastes is
characteristically low in comparison to
petrochemical wastes. Decisions on the
appropriate extent of remedy, or "how clean
is clean?", must take this feature into
account, in conjunction with the typically
large volumes of wastes usually present and
the large area over which environmental
damage may have occurred.
3	The hazardous substances of greatest concern
at mining waste sites are usually inorganic
metals, rather than the organics associated
with petrochemical wastes. In addition, deep
aquifer contamination rarely is associated
with mining waste sites because of underlying
bedrock. Thus, different scientific and
engineering expertise is required to
characterize the extent of the environmental
problem, assess risks, and evaluate possible
remedies.
4	Because the problems associated with mining
wastes are usually the result of complex
chemical reactions (i.e., acid formation),
waste sites that present risks to human health
and the environment can be distinguished
from harmless sites only by detailed
individual examination, not by knowing the
general composition or source of the wastes.
Furthermore, in some cases, problems may
develop at any time in the future. It is
difficult to predict the development of
problems, which is to say it is difficult to
identify mining waste sites that are potential
threats to human health and the
environment.
5	The determination of liability under CERCLA
for a mining waste release must take into
account the special laws governing property
rights of mine and mill operators in the West.
The old age of many inactive mining and
milling sites compounds the difficulty of
assigning liability.

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6	Nonetheless, it is generally possible to
identify a financially viable responsible party
for any mining waste site, usually an existing
firm that once operated the mine.
Consequently, responses to mining waste sites
are usually financed and managed by private
parties under an enforcement arrangement
with EPA.
7	Because of the central role of mining in the
West's history and economy, the public is
often disinclined to acknowledge that mining
wastes may endanger human health and the
environment. The fact that many mining
waste sites may not previously have posed
significant risks reinforces this attitude. It is
especially difficult to acknowledge the
existence of a problem that is invisible. In
sharp contrast to brown rivers, tailings slides,
and other problems associated with mining
wastes, however, the health risks presented
by the inhalation or ingestion of metallic
contaminants are often largely invisible. Yet
these are the problems the Superfund
program must address.
This overview is intended as an introduction to
the risks associated with mining waste sites. For
additional information, please contact the Office
of External Affairs, U.S. Environmental .
Protection Agency, Region VIII, One Denver
Place, Suite 500, 999 18th Street, Denver,
Colorado 80202-2405.

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RADIOACTIVE MINING WASTES
Radioactive mining wastes present special •
risks to human health. The most prevalent
form of radioactive mining wastes is the
tailings from uranium milling. Radioactivity
is also associated, however, with wastes
from mining for phosphate and for metals
such as vanadium and copper.
Beginning in the 1940s, large quantities of
tailings were created by milling uranium
needed for defense purposes. Most of the
uranium mills are now inactive, but tailings
piles remain at the sites. The piles have
sometimes been enormous, ranging to 150
acres in extent, 230 feet in height, and 2.7
million tons in quantity. Many were
located in floodplains adjacent to rivers
and sometimes near or within urban areas.
Over the years, tailings have been
dispersed from the piles by wind erosion,
rain, and flooding. In addition, tailings
have been removed for use in construction
and soil conditioning. It was common
practice, in communities near uranium
mills, to use tailings as fill around houses
and other buildings.
Uranium mill tailings contain radium,
which is radioactive. Radium produces
radon, a radioactive gas which, if inhaled,
can cause lung cancer. There are a
variety of additional toxic substances
characteristically present in uranium mill
tailings, including arsenic, molybdenum,
selenium, and uranium. The radioactivity
and toxic substances in uranium mill
tailings may cause a variety of cancers,
harm unborn children, and produce
genetic effects. Nonetheless, lung cancer
from the inhalation of radon decay
products is considered the greatest risk.
Under the authority of the Uranium Mill
Tailings Radiation Control Act, the U.S.
Department of Energy is now addressing
these problems by determining how to
stabilize the tailings piles to prevent
dispersal by erosion and by controlling the
emission of radon gas. In addition, tailings
used in construction are being excavated
from some 8,000 properties, mostly
residential, and mostly in the West, for
safe disposal elsewhere.
MINE TYPES IN THE WEST
Salt
Vanadium
Coal
Antimony
Uranium
Gold and Silver
Potash
Lead and Zinc
Trona
Molybdenum
Cement
Iron
Gypsum
Copper
Bentonite
Oil Shale
Mercury

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