United States
Environmental Protection
Agency
Office of Solid Waste
and Emergency Response
Washington DC 20460
EPA/530-SW-85-033
December 1985
C.
Solid Waste
Report To Congress
Wastes from the Extraction and Beneficiation
of Metallic Ores, Phosphate Rock, Asbestos,
Overburden from Uranium Mining,
and Oil Shale
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EPA/530-SW-85-033
Report To Congress
Wastes from the Extraction and Beneficiation
of Metallic Ores, Phosphate Rock, Asbestos,
Overburden from Uranium Mining,
and Oil Shale
December 31, 1985
U.S. Environmental Protection Agency
Office of Solid Waste
U.S. Environmental Protection Agency
Region 5.Library (PL-12J)
77 West Jackson Boulevard, 12tn Hoor
Chicago, IL 60504-3590
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UNITED STATES ENVIRONMENTAL PROTECTION AGENCY
WASHINGTON. D.C.' 20460
DEC 3 11985
THE ADMINISTRATOR
Honorable George Bush
President of the Senate
Washington, D.C. 20510
Dear Mr. President:
I am pleased to transmit the Report to Congress on "Wastes
from the Extraction and Beneficiation of Metallic Ores, Phosphate
Rock, Asbestos, Overburden from Uranium Mining, and Oil Shale"
presenting the results of studies carried out pursuant to Sections
8002 (f) and (p) of the Resource Conservation and Recovery Act of
1976, as amended, (42 U.S.C. SS6982 (f) and (p)).
The Report provides a comprehensive assessment of possible
adverse effects on human health and the environment from the
disposal and utilization of solid waste from the extraction and
beneficiation of ores and minerals. All metal, phosphate, and
asbestos mining segments of the United States mining industry
are included in the assessment. Waste categories covered include
mine waste, mill tailings, and waste from heap and dump leaching
operations.
The Report and appendices are transmitted in one volume.
Sincerely yours,
Lee M. Thomas
Enclosures
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UNITED STATES ENVIRONMENTAL PROTECTION AGENCY
.f4t ^. WASHINGTON. D.C. 20460
DEC 3 11985
THE ADMINISTRATOR
Honorable Thomas P. O'Neill
Speaker of the House of Representatives
Washington, D.C. 20515
Dear Mr. Speaker:
I am pleased to transmit the Report to Congress on "Wastes
from the Extraction and Beneficiation of Metallic Ores, Phosphate
Rock, Asbestos, Overburden from Uranium Mining, and Oil Shale"
presenting the results of studies carried out pursuant to Sections
8002 (f) and (p) of the Resource Conservation and Recovery Act of
1976, as amended, (42 U.S.C. SS6982 (f) and (p)).
The Report provides a comprehensive assessment of possible
adverse effects on human health and the environment from the
disposal and utilization of solid waste from the extraction and
beneficiation of ores and minerals. All metal, phosphate, and
asbestos mining segments of the United States mining industry
are included in the assessment. Waste categories covered include
mine waste, mill tailings, and waste from heap and dump leaching
operations.
The Report and appendices are transmitted in one volume.
.^Sincerely yours,
Lee M. Thomas
Enclosures
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TABLE OF CONTENTS
Page
EXECUTIVE SUMMARY ES-1
SECTION!. INTRODUCTION 1-1
1.1 Scope 1-8
1.2 Contents 1-10
SECTION 2. OVERVIEW OF THE N ON FUEL MINING
INDUSTRY 2-1
2.1 Nonfuel Mining Segments 2-1
2.2 Geographic Distribution 2-6
2.3 Mining and Beneflelation Wastes 2-10
2.4 Waste Quantities 2-18
2.5 Summary 2-23
SECTION 3. MANAGEMENT PRACTICES FOR MINING WASTES 3-1
3.1 Overview of the Mining Waste Management Process 3-1
3.2 Waste Management Practices 3-5
3.3 Waste Siting and Disposal Methods 3-13
3.4 Mitigative Measures for Land Disposal Sites 3-20
3.5 Summary 3-52
SECTION 4. POTENTIAL DANGER TO HUMAN HEALTH AND THE
ENVIRONMENT 4-1
4.1 Waste Characteristics Considered 4-2
4.2 Estimated Amounts of Potentially Hazardous Mining Waste 4-42
4.3 Effectiveness of Waste Containment at Mining Waste Sites 4-50
4.4 Structural Instability of Impoundments 4-61
4.5 Damage Cases 4-63
4.6 Risk Analysis 4-68
4.7 Summary 4-71
SECTION 5. THE ECONOMIC COST OF POTENTIAL 5-1
HAZARDOUS WASTE MANAGEMENT
5.1 Cost Methodology 5-2
5.2 Potential Costs of RCRA Subtitle C Waste Management 5-14
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CONTENTS (Continued)
Page
SECTION 6. CONCLUSIONS AND RECOMMENDATIONS 6-1
6.1 Scope 6-1
6.2 Summary of Conclusions 6-1
6.3 Recommendations 6-12
SECTION 7. SELECTED BIBLIOGRAPHY 7-1
APPENDIX A. SUMMARY OF MAJOR WASTES FROM THE MINING A-l
AND PROCESSING OF OIL SHALES
APPENDIX B. METHODOLOGY B-l
APPENDIX C. SELECTED CRITERIA ANALYZED FOR TOXIC EFFECTS C-l
APPENDIX D. GLOSSARY D-l
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EXECUTIVE SUMMARY
This is the executive summary for the Environmental Protection Agency's
Report to Congress on Wastes from the Extraction and Beneficiation of Metallic
Ores, Phosphate Rock, Asbestos, Overburden from Uranium Mining, and Oil
Shale. EPA has prepared this report in response to the requirements of
Sections 8002(f) and (p) of the Resource Conservation and Recovery Act
(RCRA). Section 8002(f), a part of RCRA when it was originally enacted in
1976, directed EPA to perform a
detailed and comprehensive study on the adverse
effects of solid wastes from active and
abandoned surface and underground mines on the
environment, including, but not limited to, the
effects of such wastes on humans, water, air,
health, welfare, and natural resources....
Section 8002(p), which Congress added to RCRA when it amended the Act in 1980,
required EPA to conduct a
detailed and comprehensive study on the adverse
effects on human health and the environment, if
any, of the disposal and utilization of solid
wastes from the extraction, beneficiation, and
processing of ores and minerals....Such study
shall be conducted in conjunction with the study
of mining wastes required by subsection (f)....
Under the 1980 amendments, EPA is prohibited from regulating solid waste
from the "extraction, beneficiation, and processing of ores and minerals"
under Subtitle C of RCRA until at least 6 months after the Agency completes
these studies and submits them to Congress. The purpose of this prohibition
is to exempt these wastes temporarily from the requirements of the RGRA
hazardous waste management system. After submitting the required studies,
holding public hearings, and providing the public with an opportunity to
ES-1
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comment, the Administrator must "determine to promulgate regulations" or
"determine such regulations are unwarranted" for these mining wastes.
If EPA decides to regulate mining wastes as hazardous under RCRA Section
3004(x), which Congress added to the Act as part of the Hazardous and Solid
Waste Amendments of 1984, EPA may modify provisions of these regulations
pertaining to liquids in landfills, land disposal restrictions, and minimum
technology requirements, as they apply to mining wastes. In doing so, EPA may
take into account the special characteristics of
such wastes, the practical difficulties associated
with implementation of such requirements, and
site-specific characteristics, including, but not
limited to, the climate, geology, hydrology and
soil chemistry at the site, so long as such
modified requirements assure protection of human
health and the environment.
This report addresses wastes from the extraction and beneficiation of
metallic ores (with special emphasis on copper, gold, iron, lead, silver, and
zinc), uranium overburden, and the nonmetals asbestos and phosphate rock. The
Environmental Protection Agency's findings on oil shales are summarized in
Appendix A of this report. EPA selected these mining industry segments
because they generate large quantities of wastes that are potentially
hazardous and because the Agency is solely responsible for regulating the
waste from extraction and beneficiation of these ores and minerals. Likewise,
the Agency excluded from the study wastes generated by the clay, sand and
gravel, and stone mining segments, since it judged wastes from these sources
less likely to pose hazards than wastes from the industries included. EPA
also excluded uranium mill tailings wastes, because the Agency has already
submitted a report to Congress on uranium mill tailings. The Agency excluded
wastes from coal mining and beneficiation, because both EPA and the Department
ES-2
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of the Interior play a role in their regulation, and it is not clear whether
Congress intended coal mining to be included within the scope of the studies
conducted in response to Sections 8002(f) and (p) of RCRA. Finally, EPA
excluded large-volume processing wastes. On October 2, 1985, EPA proposed to
reinterpret the scope of the mining waste exclusion as it applies to
processing wastes, leaving only large volume processing wastes excluded (FR
401292). Other wastes from processing ores and minerals that are hazardous
would be brought under full Subtitle C regulation after promulgation of the
reinterpretation, and would therefore not be included in the scope of a
subsequent Report to Congress on processing wastes. The large-volume
processing wastes that remain within the exclusion would be studied and a
Report to Congress prepared to complete EPA's response to the RCRA Section
8002(p) mandate.
The remainder of this Executive Summary consists of five sections. First,
we provide an overview of the industry segments covered in this report. Next,
we describe management practices for mining wastes. Then we discuss the
potential danger to human health and the environment that mining wastes pose.
Following this, we estimate the costs that regulating mining wastes could
impose under several scenarios and briefly outline the effects of these costs
on product prices. Finally, we present the Agency's conclusions and
recommendations.
OVERVIEW OF THE NONFUEL MINING INDUSTRY
The nonfuel mining industry is an integral part of our economy,
providing a wide range of important products. The value of raw nonfuel
1 For the purposes of this report, the nonfuel mining industry is defined to
include uranium, although processed uranium may be used as a fuel.
ES-3
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minerals is about 1 percent of the Gross National Product (GNP), and products
made from these raw materials account for about 9 percent of the GNP.
The number of active mines varies from year to year, depending on economic
factors; in 1980 (the most recent year for which complete data are available
from the U.S. Bureau of Mines), there were about 600 metal mines and about
12,000 nonmetal mines. Most of the nonmetal mines were clay, sand and gravel,
and stone mines, and thus fall outside the scope of this report. In
the industry segments that this report covers, a few large mines generally
produce most of the ore and generate most of the waste.
Ores occur only in certain geologic formations, so much of the mining
within an industry segment is concentrated in a few locations. Because the
raw ore must be extracted from the earth, and only a small percentage of the
mined rock is valuable, vast quantities of material must be handled for each
unit of marketable product. Much of this material is waste.
Mine waste is the soil or rock that is generated during the process of
gaining access to the ore or mineral body. Tailings are the wastes generated
by several physical and chemical beneficiation processes that may be used to
separate the valuable metal or mineral from the interbedded rock; the choice
of process depends on the composition and properties of the ore and of the
gangue, the rock in which the ore occurs. Some low-grade ore, waste rock, and
tailings are used in dump or heap leaching, a process that the mining industry
considers a form of beneficiation and one that involves spraying the material
with acid or cyanide to leach out metals. This process is most widely
practiced in the copper, silver, and gold mining segments, and the associated
wastes are termed dump/heap leaching wastes. The final waste type is mine
ES-4
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water, water that infiltrates the mine during the extraction process. Table
ES-1 lists the types and quantities of mining wastes generated by each mining
segment of concern.
Extraction and beneficiation produce large quantities of waste. The
segments covered in this report generate 1 to 2 billion tons of waste each
year and have so far produced over 50 billion tons of waste. Copper, iron
ore, uranium, and phosphate mining operations are responsible for more than
85 percent of this total volume of waste and continue to account for most of
the waste presently generated. As lower and lower grades of ore are mined,
more waste per unit of product is generated.
Approximately one-half of the waste generated by the segments of concern
is mine waste, and one-third is tailings. Most of the mine waste is from
phosphate, copper, iron ore, and uranium mining; the majority of tailings are
from the copper, phosphate, and iron ore segments. Only the copper, gold, and
silver mining industries presently generate dump or heap leach waste. The
following section discusses how industry currently manages these wastes.
WASTE MANAGEMENT PRACTICES
Mine waste, tailings, heap and dump leach wastes, and mine water can be
managed in a variety of ways. Figure ES-1 provides an overview of waste
management practices. Waste management practices include recovery operations,
volume reduction, treatment, onsite and offsite use, and waste siting and
disposal. For mine waste and tailings, disposal constitutes the major
practice; about 56 percent of mine wastes are currently managed by disposal in
piles, and about 61 percent of tailings are managed in tailings ponds. About
30 percent of mine waste and tailings are used on site in leaching operations,
ES-5
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Table ES-1 Waste Generation
(MmIons of Metric Tons in 1982)
Mining
Industry
segment
Metals:
Copper
Gold
Iron
Lead
Molybdenum
Silver
Uranium
Zinc
Other metals
Subtotal
Nonmetals:
Asbestos
Phosphate
Subtotal
TOTAL
Mine
waste
124
39
102
2
24
20
73
1
23
408
4
294
298
706
Tailings
178
24
75
9
6
6
NA
6
3
307
2
109
111
418
Leaching
wastes
200 (dump)
11 (heap)
_
_
_
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RECYCLE
NPDES
PERMITTED
DISCHARGE
V
CRUDE ORE
MILL
(BENEFICATION)
OTHER
ONSITE
UTILIZATION
MINE
WATER
MINE
WASTE
OFFSITE
UTILIZATION
OFFSITE
UTILIZATION
ONSITE
UTILIZATION
ONSITE
UTILIZATION
SOLID
WASTE
LIQUID
WASTE
TAILINGS
POND
Figure ES-1 The mining waste management process
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construction of tailings impoundments, and road construction. Present
disposal and utilization practices for all metal and nonmetal industry
segments are presented in Table ES-2. A discussion of waste management
practices follows.
Several methods are available to treat, change, or reduce wastes before
disposing of them. In operations using cyanide, it may be possible to oxidize
the cyanide before disposal. It may also be possible to remove pyrites from
tailings, thus reducing, although not eliminating, their potential for forming
acid. Finally, water can be removed from tailings, creating a thickened
discharge.
Extraction and milling wastes can also be used off site; the most common
use of these wastes is in road construction. Researchers are investigating
other uses for both mine wastes and tailings, such as use in soil supplements,
in wallboard and brick/block products, and in ceramic products. However, it
is unlikely that use of mining wastes will increase greatly in the future,
because in most cases their commercial potential is not sufficient to overcome
the economic disadvantages, such as high transportation costs, associated with
their use.
Mine water can also be used on site in the milling process as makeup
water or for dust control, cooling, or drilling fluids. In most cases,
however, the amount of mine water exceeds the quantity that can be used.
The majority of the solid waste generated in mining is not reduced by any
of the methods described above and must be disposed of. Siting disposal
facilities in appropriate locations is fundamental to environmental
protection, and other management methods are available for ameliorating waste
disposal problems.
ES-8
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Table ES-2 Present Mining Waste Disposal
and Utilization Practices
(Millions of Metric Tons/Year)
Practice Waste type and volume
Mine waste Mill tailings
Pile 569
Backfill 86 21
Onsite utilization 313 141
Impoundments - 267
Off site utilization 43 8
TOTAL 1,011 437
ES-9
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During active site life, during closure, and in the post-closure period,
facilities could employ engineering controls to prevent erosion, to keep
leachate out of the ground water, or to remove contaminants introduced into
ground water. However, EPA data on management methods at mining facilities
indicate that only a small percentage of mines currently monitor their ground
water, use run-on/runoff controls or liners, or employ leachate collection,
detection, and removal systems. EPA has not determined the circumstances
under which these waste measures would be appropriate at mine waste and mill
tailing disposal sites.
POTENTIAL DANGER TO HUMAN HEALTH AND THE ENVIRONMENT
The potential dangers posed by wastes from nonfuel mining and beneficia-
tion vary greatly and depend on the industry segment; the beneficiation
process; and site-specific geologic, hydrologic, and climatic factors. Some
rock is naturally high in metals or radionuclides. Some beneficiation
processes use acids and cyanides. Mine waste, tailings, and mine water can
contain these materials and also be acidic or alkaline. Hazardous substances
could leak into the environment, polluting the soil and surface and ground
water and endangering receptor populations.
The Agency has not yet performed a quantitative risk assessment. Risk
analysis can provide a quantitative estimate and allow EPA to distinguish
between the risk posed by current, past, and alternative management practices.
Additionally, it will enable the Agency to evaluate how site-specific factors
such as hydrology, proximity to surface water, climate, distance from human
populations, type and sensitivity of aquatic populations, closeness to
drinking water supplies, and the chemical and physical composition of the
waste itself affect risk.
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EPA evaluated the potential dangers posed by mining wastes by testing for
the RCRA characteristics of corrosivity and EP toxicity and by assessing the
level of several other substances in these wastes. A substance was considered
corrosive if the pH was equal to or less than 2 (acidic) or equal to or
greater than 12.5 (alkaline). A substance was determined to be EP toxic if,
using a specified leaching procedure, it exceeded the National Interim Primary
Drinking Water Standards (NIPDWS) for an EP toxic metal by a factor of 100.
Only samples from copper dump leach met the RCRA characteristic for
corrosivity because of low pH, but pH values were quite low (more than 2 and
less than or equal to 4) for many samples from the copper and other metals
industry segments and for one sample from the molybdenum segment. Only one
sample, from the "other" metals industry segment, met the RCRA characteristic
for corrosivity because of high pH. In addition, one sample each from the
gold and silver industry segments, three from the copper industry segment, and
four from the other metals segment had relatively high (more than 10 and less
than or equal to 12.5) pH values. EP toxic results were obtained for at least
one sample from copper dump/heap leachate, gold tailings and mine waste, lead
mine waste and tailings, silver tailings and mine waste, and zinc tailings.
EPA's water quality criteria for the protection of aquatic life are generally
set at levels at lower concentrations than those established by the NIPDWS.
Another potential threat to organisms and the environment is acid
formation. Wastes with the highest acid formation potential are in the
copper, gold, and silver industry segments, although the degree of potential
harm varies with the mineral content of wastes and soils (some wastes and
soils have neutralizing chemicals), amount of precipitation (more increases
the potential for acid drainage), and other factors not evaluated.
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Of the other potentially hazardous constituents considered, cyanide was
detected in copper and gold tailings ponds and gold heap leachate. Radioactive
material was found in uranium and phosphate mine waste samples and in phosphate
tailings. Although only asbestos mining wastes were tested in this study for
asbestos content, effluent guideline data suggest that asbestos may be present
in wastes generated by some metal mining industry segments. EPA has
insufficient data to evaluate the hazard, if any, posed by asbestos contained
in metal mining wastes.
Based on these sampling results, EPA estimates that the copper mining
segment generates 50 million metric tons of RCRA corrosive waste annually.
The gold, lead, silver, and zinc industry segments generate a total of 11.2
million metric tons of RCRA EP toxic waste annually. EPA estimates that 182
million metric tons of copper dump leach are generated annually, and that the
gold and silver segments generate a total of 9.3 million metric tons of
tailings and 14 million metric tons of heap leach annually. High acid
formation potential waste is estimated at 95 million metric tons a year. The
phosphate and uranium mining industries generate approximately 443 million
metric tons of radioactive waste (with a radioactivity level of more than
5 picocuries/gram, the level established as a "cleanup" standard under the
1983 standards for Protection Against Uranium Mill Tailings). There are also
5 million metric tons of asbestos-containing waste (asbestos content greater
than 1 percent by weight) generated each year. Estimated amounts of
potentially hazardous wastes are reported in Table ES-3.
Of the estimated 1,340 million metric tons of waste generated annually by
metal, asbestos, and phosphate mining, 61 million tons are estimated to be
hazardous under current RCRA Subtitle C characteristics. Adding wastes with
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Table ES-3 Estimated Amounts of Wastes with
RCRA Hazardous Characteristics and Other
Wastes Potentially Subject to Regulation
as Hazardous Wastes Under RCRA
Category
Annual amount
(millions of
metric tons)
Source
Potential danger
RCRA Characteristics
Corrosive
EP toxic
Other Categories
Precious metal
recovery wastes
Heap leaching
wastes
Dump leaching
wastes
Radioactive
wastes ( 5 pCi/g)
Acid
formation
Asbestos
50
11
14a
182a
352
91
95
5
7553
Copper leach
dump liquor
Gold, silver, lead,
zinc wastes
Gold, silver
Gold, silver
Copper dump leach
wastes
Phosphate,
uranium
Copper mill
tailings
Asbestos mines
and mills
Ground-water
acidification
Toxic metal
ground-water
contamination
Cyanide contamination
of surface and
ground water
Cyanide contamination
of surface and
ground water
Massive release of
toxic metals and
low pH liquids
Radon
emissions
Release of low pH
liquids after closure
Cancer
a The total annual amount of waste is not equal to the sum of hazardous waste
in each category because some wastes are in more than one category. For
example, 50 million metric tons of copper dump leach waste are also corrosive,
and 4 million metric tons of gold tailings are both EP toxic and contaminated
with cyanide.
ES-13
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high acid formation potential, those that contain asbestos, those that are
potential candidates for listing because they commonly have high levels of
cyanide (greater than or equal to 10 mg/1), and radioactive wastes (radium-226
greater than or equal to 5 picocuries/gram) would increase this total to 755
million metric tons of potentially hazardous waste generated by these mining
industry segments each year.
EPA conducted a study to determine whether mining waste management
facilities leak and, if they do, whether they release constituents that are of
concern. Surface water and/or ground water was monitored at eight
representative active mine sites. Results indicate that constituents from
impoundments do enter ground water at most sites, but significant increases in
the concentrations of hazardous constituents were rarely demonstrated.
Damage cases, however, show that mine runoff and seepage have adversely
affected surface and ground water in several mining districts. Sudden and
chronic releases of cyanides, acids, and metals have reduced fish populations
and the number of other freshwater organisms. However, some of these
incidents were caused by waste management practices that are no longer in use.
THE ECONOMIC COST OF POTENTIAL RCRA WASTE MANAGEMENT
EPA examined the wide range of potential costs that regulating mining
wastes as hazardous under RCRA could impose on facilities and segments of the
mining industry. To examine this range, EPA estimated the incremental costs,
those over and above the costs the industry already incurs to manage wastes,
for eight regulatory scenarios of varying stringency. EPA constructed these
eight scenarios by taking all combinations of four different sets of manage-
ment standards and two criteria for determining whether wastes are hazardous.
ES-14
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The estimation procedure applied specific information from 47 mines to develop
costs at these mines and then extrapolated these results to the universe
covered in this report.
The management standards that EPA examined ranged from imposing the full
set of RCRA Subtitle C regulations (the most expensive set of management
standards, Scenario 1) to requiring only a limited set of requirements:
permits, a leachate collection system, a ground-water monitoring system, a
run-on/runoff system, and post-closure maintenance (Scenario 4). Under the
first criterion for determining whether wastes were hazardous, waste streams
failing the Subtitle C characteristics tests for EP toxicity and corrosivity
and cyanide wastes from gold metal recovery operations were included as
hazardous (Scenario A). Under the second criterion, all wastes captured under
the first set were included, as well as (1) wastes from gold and silver heap
leach operations, (2) wastes with high acid formation potential, and (3) copper
dump leach wastes (Scenario B). Both hazardous waste criteria captured only
wastes from the copper, gold, silver, lead, and zinc mining segments.
Estimated costs could be very substantial, depending on the management
standards and criteria for defining hazardous waste. Under the most costly
combination (the unlikely scenario imposing the full set of RCRA regulations
and the most restrictive criterion for determining whether waste is hazardous,
Scenario IB), the annualized costs for the mining segments covered by the
assessment were $850 million per year, while for the least costly combination
(maintenance and monitoring), the annualized cost was $7 million per year.
(Annualized costs resemble mortgage payments, in that they spread the present
value of total costs into equal payments over the time period EPA estimates
the affected mines will be productive.)
ES-15
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As the previous paragraph demonstrates, costs vary substantially across
the different cost scenarios. Generally, the highest cost scenarios are
several times more expensive than the intermediate cost scenarios; these, in
turn, are several times more expensive than the least expensive. The
additional waste management costs incurred by adding Scenario B wastes to the
wastes to be regulated are also substantial; the costs of managing all
Scenario B wastes would be two to four times higher than the costs of managing
only the Scenario A wastes, for any given management standard.
The potential costs of regulation also vary widely for the five
individual metal mining segments, both across segments and scenarios. Under
all scenarios, the copper industry would incur the largest cost, while the
gold industry would bear the second highest lifetime cost.
The additional effects of regulation on some segments of the mining
industry could be substantial. For a low-cost scenario, average affected
facilities in the zinc segment (the segment most affected by regulatory costs
as a percent of direct product cost) would incur costs as high as 5 percent of
direct product costs, while under a high-cost scenario a zinc facility could
incur costs of 10 percent. Under a high-cost scenario, RCRA compliance costs
as a percent of direct product cost for the average affected facility were 21
percent in the lead industry and ranged upward of 120 percent in the copper
industry.
CONCLUSIONS
Structure and Location of Mines
EPA focused on segments producing and concentrating metallic ores,
phosphate rock, and asbestos, totalling fewer than 500 active sites during
1985. These sites are predominantly in sparsely populated areas west of the
ES-16
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Mississippi but have great diversity in size, product value, and volumes of
material handled. Several segments are concentrated primarily in one state:
the iron segment is mainly concentrated in Minnesota, lead in Missouri, copper
in Arizona, asbestos in California, and phosphate in Florida.
Waste Quantities
Aggregate waste quantities generated were 1.3 and 2 billion metric tons
per year in 1982 and 1980, respectively. The accumulated waste (for segments
other than coal) is estimated to be approximately 50 billion metric tons.
Waste-to-product ratios are generally higher in mining industry segments than
in other industrial segments. Some individual mines and mills handle more
materials than many entire industries, but 25 percent of the mines studied
handled less than 1,000 metric tons per year.
Potential Hazard Characteristics
Of the 1.3 billion metric tons of wastes that EPA estimates will be
generated by extraction and beneficiation in 1985, about 61 million metric
tons (5 percent) exhibit the characteristics of corrosivity and EP (extraction
procedure) toxicity. Another 23 million metric tons (2 percent) are
beneficiation wastes contaminated with cyanide. Also, there are 182 million
metric tons (14 percent) of copper leach dump material and 95 million metric
tons (7 percent) of copper mill tailings with the potential for release of
acidic and toxic liquids. If waste with radioactivity content greater than 5
picocuries per gram is considered hazardous, the hazardous volume is 443
million metric tons (34 percent) from the phosphate and uranium segments; if
waste with radioactivity greater than 20 picocuries per gram is considered
hazardous, the total is 93 million metric tons (7 percent). Four asbestos
mines generated about 5 million metric tons (less than 1 percent) of waste
with a chrysotile content greater than 5 percent.
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Evidence of Environmental Transport
At mine sHes, ground-water monitoring is difficult and expensive, and
generally is not conducted on a large scale. From short-term monitoring
studies at eight sites, EPA detected seepage from tailings impoundments, a
copper leach dump, and a uranium mine water pond. However, EP toxic metals of
concern did not appear to have migrated during the 6- to 9-month monitoring
period. Other ground-water monitoring studies have detected sulfates,
cyanides, and other contaminants from mine runoff, tailings pond seepage, and
leaching operations.
Evidence of Damages
Incidents of damage {contamination of drinking water aquifers,
degradation of aquatic ecosystems, fish kills, and related reductions of
environmental quality) have been documented in the phosphate, gold, silver,
copper, lead, and uranium segments. There are 13 mining sites on the National
Priorities List (Superfund), including five gold/silver, three copper, three
asbestos, and two lead/zinc mines. The asbestos Superfund sites differ from
other sites in that these wastes pose a hazard via airborne exposure. It is
not clear, from the analysis of damage cases and Superfund sites, whether or
not current waste management practices can prevent damage from seepage or
sudden releases. However, it is clear that some of the problems at abandoned
or Superfund sites are attributable to waste disposal practices not currently
used by the mining industry.
Waste Management Practices
Site selection for the mine, as well as its associated beneficiation and
waste disposal facilities, is the single most important aspect of
environmental protection in the mining industry. Most mine waste is disposed
of in piles, and most tailings in impoundments. Mine water is often recycled
ES-18
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through the mill and used for other purposes on site. Offsite utilization of
mine waste and mill tailings is limited (2 to 4 percent). Some management
measures (e.g., source separation, treatment of acids or cyanides, and waste
stabilization) now used at some facilities within a segment of the mining
industry could be more widely used. Other measures applied to hazardous waste
in nonmining industries may not be appropriate. Soil cover borrowed from
surrounding terrain may create additional reclamation problems in arid regions.
Potential Costs of Regulation
For five metal mining segments, total annualized costs range from
$7 million per year (for a scenario that emphasizes primarily basic maintenance
and monitoring, for wastes that are hazardous by RCRA characteristics) to over
$800 million per year (for an unlikely scenario that approximates a full RCRA
Subtitle C regulatory approach, emphasizing cap and liner containment for all
wastes considered hazardous under the current criteria, plus cyanide and acid
formation wastes). About 60 percent of the total projected annualized cost at
active facilities can be attributed to the management of waste accumulated
from past production. Those segments with no hazardous wastes (e.g., iron)
would incur no costs. Within a segment, incremental costs would vary greatly
from facility to facility, depending on current requirements of state laws,
ore grade, geography, past waste accumulation, percentage of waste with
hazardous characteristics, and other factors.
RECOMMENDATIONS
Section 8002(f) of RCRA requires EPA to conduct a study of the adverse
effects of mining waste and to provide "recommendations for Federal...actions
concerning such effects." Based on our findings from this study, we make
ES-19
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several preliminary recommendations for those wastes and industry segments
included in the scope of the study. The recommendations are subject to change
based on continuing consultations with the Department of the Interior (DOI)
and new information submitted through the public hearings and comments on this
report. Pursuant to the process outlined in RCRA §3001(b)(3)(C), we will
announce our specific regulatory determination within 6 months after
submitting this report to Congress.
First, EPA is concerned with those wastes that have the hazardous
characteristics of corrosivity or EP toxicity under current RCRA regulations.
EPA intends to investigate those waste streams. During the course of this
investigation, EPA will assess more rigorously the need for and nature of
regulatory controls. This will require further evaluation of the human health
and environmental exposures mining wastes could present. EPA will assess the
risks posed by mining waste sites and alternative control options. The Agency
will perform additional waste sampling and analysis, additional ground-water
or surface water monitoring and analysis, and additional analysis of the
feasibility and cost-effectiveness of various control technologies.
If the Agency determines through the public comments, consultation with
DOI and other interested parties, and its own analysis, that a regulatory
strategy is necessary, a broad range of management control options consistent
with protecting human health and the environment will be considered and
evaluated. Moreover, in accordance with Section 3004(x), EPA will take into
account "the special characteristics of such waste, the practical difficulties
associated with implementation of such requirements and site specific
characteristics...," and will comply with the requirements of Executive Orders
12291 and 12498 and the Regulatory Flexibility Act.
ES-20
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Second, EPA will continue gathering information on those waste streams
that our study indicates may meet EPA's criteria for listing as hazardous
wastes requiring regulation—dump leach waste, because of its high metal
concentrations and low pH, and wastes containing cyanides. Although these
waste streams are potential candidates for listing as hazardous wastes, we
need to gather additional information similar to the information gathered for
the rulemaking for corrosive and EP toxic wastes. When we have gathered
sufficient information, we will announce our decision as to whether to
initiate a formal rulemaking. If the Agency finds it necessary to list any of
these wastes, we will also develop appropriate management standards in the
same manner as we did those developed for corrosive and EP toxic wastes.
Finally, EPA will continue to study radioactive waste and waste with the
potential to form sulfuric acid. The Agency is concerned that radioactive
wastes and wastes with the potential for forming acid may pose a threat to
human health and the environment, but we do not have enough information to
conclude that they do. We will continue to gather information to determine
whether these wastes should be regulated. If EPA finds that it is necessary
to regulate these wastes, the Agency will develop the appropriate measures of
hazard and the appropriate waste management standards.
ES-21
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SECTION 1
INTRODUCTION
This report is required by Sections 8002(f) and (p) of the Resource
Conservation and Recovery Act (RCRA), which directs the Environmental
Protection Agency (EPA) to perform studies of wastes generated in the mining,
beneficiation, and processing of ores and minerals and to report the results
of these studies to Congress. This report is based on literature reviews and
contractor studies, including numerous analytical testing results on the
wastes. EPA's RCRA Docket contains copies of the source materials that the
Agency used in preparing this report.
Because Congress has amended the Act several times in ways that changed
the requirements for mining wastes, and because EPA regulations continue to
evolve both in response to legislation and as EPA collects additional
information, a brief legislative and regulatory history provides a useful
context for this Report to Congress.
When first enacted in 1976 (P.L. 94-580), RCRA contained a broad
definition of solid waste that included "solid, liquid, semi-solid, or
contained gaseous material resulting from...mining...operations." [emphasis
added] (Section 1004(27)).
Section 8002(f) of the original Act directed EPA to conduct a
detailed and comprehensive study on the adverse effects of
solid wastes from active and abandoned surface and
underground mines on the environment, including, but not
limited to, the effects of such wastes on humans, water,
air, health, welfare, and natural resources, and on the
adequacy of means and measures currently employed by the
mining industry, Government agencies, and others to dispose
of and utilize such solid wastes to prevent or
substantially mitigate such adverse effects.
1-1
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The study was to include an analysis of:
1. The sources and volume of discarded material
generated per year from mining;
2. Present disposal practices;
3. Potential danger to human health and the environment
from surface runoff of leachate and air pollution by
dust;
4. Alternatives to current disposal methods;
5. The cost of those alternatives in terms of the impact
on mine product costs; and
6. Potential for use of discarded material as a
secondary source of the mine product.
The Act did not specify a date for the completion of this study.
On December 18, 1978, EPA proposed regulations to implement Subtitle C of
RCRA, including rules for identifying and listing hazardous wastes and for
managing these wastes. Based on the language in the House Committee Report
accompanying the House Bill, which was the predecessor to the Act, EPA
specifically excluded as a hazardous waste "overburden resulting from mining
operations and intended for return to the mine site" unless the overburden was
specifically listed. The Agency proposed to list waste rock and overburden
from uranium mining and overburden and slimes from phosphate surface mining
because of concern about their radioactivity. The proposal also considered
any other mining wastes that were ignitable, corrosive, reactive, or EP toxic
as hazardous waste.
In addition, the proposal included distinct management standards for
"special wastes," which "occur in very large volumes" and for which "the
potential hazards...are relatively low" (43 FR 58992, December 18, 1978). The
Agency proposed less stringent standards for these wastes than for other
1-2
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hazardous wastes, pending the development of additional information and a
subsequent planned rulemaking. Certain mining wastes were among the special
wastes. They included phosphate mining, beneficiation, and processing wastes;
uranium mining waste; and other mining waste that was ignitable, corrosive,
reactive, or EP toxic.
On May 19, 1980, EPA promulgated interim final regulations implementing
Subtitle C of RCRA. The Agency retained the exclusion for overburden that was
returned to the mine site; however, the Agency dropped the two proposed
listings, because the regulations "eliminated the part of the proposed
exemption that would allow exempted overburden to be brought within RCRA
jurisdiction through specific listing as a hazardous waste" (45 FR 33100, May
19, 1980). EPA also promulgated interim final listings for three specific
mining waste streams: (1) flotation tailings from selective flotation from
mineral metals recovery operations, (2) cyanidation wastewater treatment
tailings pond sediment from mineral metals recovery operations, and (3) spent
cyanide bath solutions from mineral metals recovery operations. Before the
first of these listings became effective, however, EPA withdrew this listing
based on technical comments from the regulated community.
These promulgated standards did not have distinct and less stringent
management standards for mining wastes. Between the time of the proposal and
the promulgation of the interim final rule, EPA modified the EP toxic and
corrosivity criteria for hazardous wastes, and the Agency therefore
anticipated that a smaller quantity of mining wastes would be classified as
hazardous based on results of tests for these two characteristics. However,
EPA judged that wastes so classified would clearly exhibit sufficient toxicity
to be of concern. "Thus the concern over the inapplicability of the proposed
1-3
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regulations to hazardous special wastes, due to the potentially large volume
and low level of hazard of these wastes, is not a valid concern in the final
regulations" (45 FR 33174, May 19, 1980). The preamble also noted that there
was no current provision that would permit deferring the regulation of mining
wastes until the results of the Section 8002(f) study were available. EPA did
point out, however, that Congress was considering legislation that would amend
RCRA to require deferral until the study was complete.
Congress then amended RCRA in the Solid Waste Disposal Act of 1980
(P.L. 96-482), enacted on October 21, 1980. Among other things, the
amendments prohibited EPA from regulating solid waste from the "extraction,
beneficiation, and processing of ores and minerals, including phosphate rock
and overburden from the mining of uranium ore" as hazardous wastes under
Subtitle C of RCRA until at least 6 months after the Agency completed and
submitted to Congress the studies required by Section 8002(f) and by a new
section, 8002(p).
Section 8002(p) requires EPA to perform a comprehensive study on the
disposal, and utilization of solid waste from the extraction, beneficiation,
and processing of ores and minerals, including phosphate rock and overburden
from uranium mining. This new study, to be conducted in conjunction with the
study of mining wastes required by Section 8002(f), mandated an analysis of:
1. The source and volumes of such materials generated
per year;
2. Present disposal and utilization practices;
3. Potential danger, if any, to human health and the
environment from the disposal and reuse of such
materials;
4. Documented cases in which danger to human health or
the environment has been proven;
1-4
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5. Alternatives to current disposal methods;
6. The costs of such alternatives;
7. The impact of these alternatives on the use of
phosphate rock and uranium ore, and other natural
resources; and
8. The current and potential utilization of such
material s.
The amendments also required the Administrator, "after public hearings
and opportunity for comment, either to determine to promulgate regulations"
for mining wastes or "to determine that such regulations are unwarranted."
These determinations must be published in the Federal Register.
Finally, the amendments specified that EPA could control radiation
exposures caused by mining wastes under RCRA. Section 3001(b)(3)(B)(iii)
authorized the Administrator to
prescribe regulations...to prevent radiation exposure which
presents an unreasonable risk to human health from the use
in construction or land reclamation (with or without
revegetation) of (I) solid waste from the extraction,
beneficiation, and processing of phosphate rock or (II)
overburden from the mining of uranium ore.
On November 19, 1980, EPA published an interim final rule to implement
the 1980 RCRA Amendments. Specificially, EPA excluded from regulation under
Subtitle C of the Resource Conservation and Recovery Act "...solid waste from
the extraction, beneficiation and processing of ores and minerals (including
coal), including phosphate rock and overburden from the mining of uranium ore"
(45 Fed. Reg. 76618, codifield at 40 CFR 261.4(b)(7)K The Agency interpreted
the scope of the exclusion very broadly:
Until the Agency takes further rulemaking action on this
matter, it will interpret the language of today's amend-
ments, with respect to the mining and mineral processing
waste exclusion, to include solid waste from the explora-
tion, mining, milling, smelting and refining of ores and
1-5
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minerals. This exclusion does not, however, apply to
solid wastes, such as spent solvents, pesticide wastes,
and discarded commercial chemical products, that are not
uniquely associated with these mining and allied process-
ing operations (45 FR 76619, November 19, 1980).
EPA solicited public comment on its interpretation to assist in determin-
ing the appropriate scope of the statutory exclusions.
In particular, EPA questions whether Congress intended to
exclude (1) wastes generated in the smelting, refining and
other processing of ores and minerals that are further
removed from the mining and beneficiation of such ores and
minerals, (2) wastes generated during exploration for
mineral deposits, and (3) wastewater treatment and air
emission control sludges generated by the mining and
mineral processing industry. EPA specifically seeks
comment on whether such wastes should be part of the
exclusion. EPA also seeks comment on how it might
distinguish between excluded and non-excluded solid wastes
(45 FR 76619, November 19, 1980).
The Hazardous and Solid Waste Amendments of 1984, enacted in November of
that year as P.L. 98-616, represent the culmination of the House and Senate
reauthorization hearings begun in early 1983. Of chief concern to the mining
industry are amendments that provide EPA flexibility in applying bans on land
disposal and certain requirements for obtaining permits under Subtitle C of
RCRA to the mining industry.
The amended statute provides, under Section 3004(x), that if mining
wastes become subject to regulation as hazardous wastes under Subtitle C, the
Administrator of EPA, in promulgating regulations, is authorized to modify the
requirements of subsections (c), (d), (e), (f), (g), (o), and (u) of Section
3004 and subsection 3005(j), which relate to:
1. Liquids in landfills,
2. Prohibitions on land disposal,
3. Solvents and dioxins,
4. Disposal into deep injection wells,
1-6
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5. Additional land disposal prohibition determinations,
6. Minimum technological requirements,
7. Continuing releases at permitted facilities, and
8. Interim status surface impoundments.
The Administrator is authorized to take into account the special
characteristics of mining and beneficiation wastes, "the practical
difficulties associated with implementation of such requirements, and site-
specific characteristics, including, but not limited to, the climate, geology,
hydrology, and soil chemistry at the site, so long as such modified
requirements assure protection of human health and the environment."
The Conference Report accompanying H.R. 2867 (which in its final amended
form was passed by both Houses of Congress as P.L. 98-616) provides
clarification:
This Amendment recognizes that even if some of the special study
wastes [which include mining wastes as specified in Sections 8002
(f) and (p)] are determined to be hazardous it may not be necessary
or appropriate because of their special characteristics and other
factors, to subject such wastes to the same requirements that are
applicable to other hazardous wastes, and that protection of human
health and the environment does not necessarily imply the uniform
application of requirements developed for disposal of other
hazardous wastes. The authority delegated to the Administrator
under this section is both waste-specific and requirement-specific.
The Administrator could also exercise the authority to modify
requirements for different classes of wastes. Should these wastes
become subject to the requirements of Section 3005 (j), relating to
the retrofit of surface impoundments, the Administrator could modify
such requirements so that they are not identical to the requirements
that are applied to new surface impoundments containing such
wastes. It is expected that before any of these wastes become
subject to regulations under subtitle C, the Administrator will
determine whether the requirements of Section 3004 (c), (d), (e),
(f), (g), (o), and (u), and Section 3005(j) should be modified
[H.R. Report 98-1133, pp. 93-94, October 3, 1984].
On October 2, 1985, EPA proposed (50 Fed. Reg. 401292) to reinterpret the
scope of the mining waste exclusion as it applies to processing wastes,
1-7
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leaving within it only large-volume processing wastes, such as slag from
primary metal smelters and elemental phosphorus plants, red and brown muds
from bauxite refineries, and phosphogypsum from phosphoric acid plants. Those
other wastes from processing ores and minerals that are hazardous would be
brought under full Subtitle C regulation after the promulgation of the rein-
terprete ti on, and would therefore not be included in the scope of a subsequent
Report to Congress on processing wastes. The large-volume processing wastes
that remain within the exclusion would be studied and a Report to Congress
prepared to complete EPA's response to the RCRA Section 8002(p) mandate.
Thus, EPA must submit a Report to Congress under RCRA Sections 8002(f) and
(p) and then publish its findings in the Federal Register before any waste
covered by the mining exclusion can be regulated under Subtitle C of RCRA. No
such restrictions, however, apply to wastes not included within the scope of
the exclusion.
1.1 SCOPE
This report addresses waste from the mining and beneficiation of metallic
ores, with special emphasis on copper, gold, iron, lead, molybdenum, silver,
and zinc; uranium overburden; and the nonmetals asbestos, phosphate rock, and
oil shales. (Appendix A to this report addresses wastes from the mining and
beneficiation of oil shales.) EPA selected the mining industry segments to be
covered in this report on the following basis. First, the Agency excluded
wastes that are the primary responsibility of other regulatory agencies.
Thus, this report does not address uranium mill tailings or the mining and
beneficiation of coal. The Uranium Mill Tailings Radiation Control Act of
1978 (UMTRCA) (P.L. 95-604) requires proper disposal of "residual radioactive
1-8
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material," including mill tailings and residual stocks of unprocessed ores or
low-grade materials. UMTRCA directed EPA to prepare a Report to Congress on
uranium mill tailings, and the Agency has done so. Under UMTRCA, EPA
determines "standards of general application," and the Nuclear Regulatory
Commission writes the implementing regulations and enforces them for active
mills. Uranium mill tailings are defined as "byproduct material" by the
Atomic Energy Act and, as such, do not constitute a "solid waste" as defined
by RCRA Section 1004(27). Therefore, they are not subject to RCRA
requirements.
The Surface Mining Control and Reclamation Act of 1977 (SMCRA) (P.L.
95-87) applies to surface coal mining reclamation activities. Under RCRA, the
Administrator of EPA must review any regulations under SMCRA that are
applicable to coal mining wastes and overburden. However, the Secretary of
the Interior, with concurrence from the Administrator of EPA, is responsible
for promulgating regulations that effectuate the purposes of Subtitle C of
RCRA with respect to "coal mining wastes or overburden for which a surface
coal mining and reclamation permit is issued or approved under the Surface
Mining Control and Reclamation Act of 1977."
The Agency also excluded from the scope of this report wastes generated in
the processing of ores or minerals. EPA will address large-volume wastes
(such as slag and phosphogypsum) generated by these processes in a subsequent
report. EPA will also evaluate other nonmetal mining wastes (in addition to
asbestos and phosphate) and wastes from inactive or abandoned mines at a later
time.
1-9
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1.2 CONTENTS
This report consists of seven sections and four appendices. The following
paragraphs briefly discuss each of the remaining sections of the report.
Section 2, OVERVIEW OF THE NONFUEL MINING INDUSTRY,2 presents a summary
of the mining and beneficiation of ores and minerals and provides information
on the number of mines, their geographic distribution, and the quantity of
waste generated in mining and beneficiation.
Section 3, MANAGEMENT PRACTICES FOR MINING WASTES, provides an overview of
the mining waste management process and discusses specific waste management
practices and mitigative measures for the land disposal of mining waste. For
some segments of the industry, the section provides information on the
proportion of mine facilities that currently practice these mitigative
measures.
Section 4, POTENTIAL DANGER TO HUMAN HEALTH AND THE ENVIRONMENT, presents
information on the characteristics of the wastes that pose a potential threat
to human health and the environment. It estimates how much mining industry
waste would fail current RCRA hazardous waste characteristics, and how much
would be hazardous under an augmented set of characteristics. It then
provides the results of EPA's monitoring of ground water at selected sites.
It also discusses the structural stability of impoundments used to manage
mining waste. Next, it presents damage cases. Finally, it describes how risk
analysis could be used to quantify the effects that current and alternative
practices have on human health and the environment.
Section 5, THE ECONOMIC COST OF POTENTIAL RCRA WASTE MANAGEMENT, first
presents the methodology EPA used to determine the potential cost of
regulating mining wastes under RCRA, using four different regulatory scenarios
1-10
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and two different sets of hazard criteria. The section then presents the
results of the analysis in terms of total potential costs, the potential costs
to various mining sectors, and the potential costs to the affected mines.
Section 6, CONCLUSIONS AND RECOMMENDATIONS, summarizes the conclusions
reached in the other sections of the report and presents EPA's recommendations.
Section 7, SELECTED BIBLIOGRAPHY, lists the sources that were used in this
report as well as some references that contain valuable information related to
mining waste.
This report also contains four appendices:
• Appendix A, SUMMARY OF MAJOR WASTES FROM THE MINING AND PROCESSING OF
OIL SHALES, summarizes a report on high-volume wastes generated by
the mining and processing of oil shales. This information was not
included in this Report to Congress because the United States oil
shale industry is not yet operating on a commercial scale. The
entire oil shale report is available in the EPA docket.
t Appendix B, METHODOLOGY, describes the methdology used by EPA to
assess current industry waste management practices and to estimate
the amount of hazardous mining waste generated annually.
• Appendix C, SELECTED CRITERIA ANALYZED FOR TOXIC EFFECTS, contains
tables comparing levels of metals measured by the EP toxicity test
allowed by various EPA standards and criteria; tables on arsenic,
cadmium, chromium, lead, mercury, selenium, and cyanide toxicity to
aquatic biota are also included. In addition, this appendix
summarizes radiation effects and effects of asbestos exposure on
various biological species, and the effects of decreasing pH on fish.
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• Appendix D, GLOSSARY, provides definitions of mining-related and
other technical terms referred to in the text.
1-12
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SECTION 1 FOOTNOTES
1 US EPA 1983a.
For the purposes of this report, the nonfuel mining industry is defined as
including uranium although processed uranium may be used as fuel.
1-13
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SECTION 2
OVERVIEW OF THE NONFUEL MINING INDUSTRY
The nonfuel mining industry is an integral part of our economy. It
provides a diversity of products, including the lead used in storage
batteries, ammunition, and pigments; copper for electrical equipment and
supplies; iron for the construction and transportation industries; zinc for
galvanizing and other uses; silver for photographic materials; gold for
electronic equipment, jewelry, and medicinal use; and the uranium used by
electric utilities. This sector also produces nonmetallic minerals such as
asbestos for use in insulating materials and phosphates used to produce
industrial chemicals and fertilizers. The total metal ore production in
the United States was worth more than $5.8 billion, and the total value of raw
2
nonfuel minerals was more than $21 billion in 1983. This value accounted
for 1 percent of the Gross National Product (GNP), while products made from
3
these raw materials account for approximately 9 percent of the GNP annually.
2.1 NONFUEL MINING SEGMENTS
There were 580 metal mines and 12,117 nonmetal mines active in 1980 (the
most recent year for which complete data are available from the U.S. Bureau of
4
Mines). The number of active mines varies from year to year, depending on
factors such as the level of U.S. economic activity, the costs of production
in the mining industry, the demand for products derived from nonfuel minerals,
and prices in international markets. In general, the number of mines in
operation has decreased over the past several years; however, a reasonable
estimate for 1983 indicates that between 400 and 500 metal mines operated in
2-1
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the segments covered here. Table 2-1 lists the number of active nonfuel mines
in 1980, 1981, and 1982 for the mining industry segments covered in this
report: all metal mines, except gold placer operations, appear in the metals
category, and all asbestos and phosphate mines appear in the nonmetals
category. The metal mining segments include copper, gold, iron ore, lead,
molybdenum, silver, uranium, zinc, and a group of "other" metals. The metals
in the "other" category have been grouped in order to avoid disclosing
confidential business information; they include antimony, bauxite, beryllium,
mercury, nickel, the rare earth metals, titanium, and vanadium. Because
domestic tin and manganiferous ore mines have been minor sources of ore since
1982, these segments are not covered in this report. Platinum also is not
covered in this report because no platinum mines have been active since 1982.
Although mines are classified on the basis of their predominant product,
they may also produce large quantities of other materials as coproducts. For
example, in 1978, U.S. zinc mines produced 72 percent of all zinc; 100 percent
of all cadmium, germanium, indium, and thallium; and 3.1, 4.1, and 6.1 percent
of all gold, silver, and lead mined in the United States, respectively. In
the same year, copper mines produced over 30 percent of the silver, 35 percent
of the gold, and 100 percent of the rhenium, selenium, palladium, tellurium,
and platinum mined in this country. Thus, a copper mine may also produce
gold and silver as coproducts. Table 2-2 summarizes the products and
coproducts for selected metal mining segments.
In most mining segments, a few large mines produce most of the product.
Table 2-3 shows the number of mines in each segment, categorized by volume of
material handled. This volume includes the amount of earth and rock that must
be removed to reach the ore. About half of all U.S. metal mines active in
1982 were small, handling less than 10,000 tons of material each. These 213
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Table 2-1 Number of Active Mines in the Industry Segments
Covered in This Report in 1980, 1981, and 1982*
Mining
industry
segment
Metals:
Bauxite (aluminum)
Copper
Goldb
Iron ore
Lead
Silver
Titanium
Tungsten
Uranium
Zinc
Other metal sc
Number of
mines
1980
10
39
44
35
33
43
5
29
265
20
21
Number of
mines
1981
10
44
107
31
29
75
5
29
195
17
18
Number of
mines
1982
8
32
101
26
17
63
5
23
128
14
21
Subtotal 544 560 438
Nonmetals:
Asbestos
Phosphate rock
Subtotal
TOTAL
4
44
48
592
4
43
47
607
3
33
36
474
<* Excludes wells, ponds, and pumping operations.
b Excludes placer operations.
c Includes antimony, beryllium, mercury, molybdenum, nickel, platinum,
rare-earth metals, and vanadium.
Source: Adapted from BOM 1981 a, BOM 1982, and BOM 1983.
2-3
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Table 2-2 Product As a Percentage of Total Output
for Selected U.S. Metal Mines in 1978
Primary
mine
product
Copper
Gold
Lead
Silver
Zinc
Total9
Copper
98.8
._ b
0.8
0.3
0.1
100.0
Gold
36.7
55.6
0.1
4.1
3.1
99.6
Product or
Coproduct
Lead Silver
—
—
90.
3.
6.
99.
b 31.7
b 1.7
3 8.7
4 53.7
1 _iil
8 99.9
Zinc
1.3
..b
25
0.9
72
99.2
a Totals may not equal 100 percent due to rounding.
b Indicates less than 0.5 percent.
Source: Adapted from BOM 1981 a.
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Table 2-3 Mines in the Industry Segments Covered in this Report in 1982,
by Volume of Material Handled*.15
ro
i
en
Mining
industry
segment
Metals:
Bauxite (aluminum)
Copper
GoldC
Iron ore
Lead
Si 1 ver
Titanium
Tungsten
Uranium
Zinc
Other metalsd
Subtotal
Nonmetal s:
Asbestos
Phosphate rock
Subtotal
TOTAL
a Includes product
Total
number
of
mines
8
32
101
26
17
63
5
23
128
14
21
438
3
33
36
474
and waste,
Less
than
1,000
tons
._
3
41
__
7
32
—
18
16
*.«
5
122
^____
--
122
but excl
1,000
to
10,000
tons
1
1
28
2
1
14
--
2
34
1
7
91
—
1
92
udes wells,
10,000
to
100,000 1
tons
5
5
11
4
--
6
--
2
52
2
2
89
3
—
3
92
ponds, and
b These data are reported in short tons; one short ton equals
C FyrluHpc nl arpr nnpratinnc.
100,000
to
,000,000
tons
2
1
14
6
2
10
1
1
24
9
2
72
4
4
76
pumping
1,000,000
to
10,000,000
tons
„
15
6
8
7
1
4
--
2
2
5
50
23
23
73
operations.
More
than
10,000,000
tons
..
7
1
6
--
--
--
--
--
__
--
14
_.
5
5
19
1.1 metric tons.
d Includes antimony, beryllium, mercury, molybdenum, nickel, rare-earth metals, and vanadium.
Source: BOM 1981 a.
-------
small mines handled only 10 percent of the material handled by the 14 largest
mines.
2.2 GEOGRAPHIC DISTRIBUTION OF MINES
Because ores occur only in certain geologic formations, most of the mining
in each industry segment is concentrated in a few locations. Copper mining is
centered in three states: Arizona, Utah, and New Mexico. Other states where
copper is mined as a coproduct of silver, zinc, and lead production are
Montana, Tennessee, and Missouri, respectively. Some copper mines and mills
are close to large cities (Tucson and Salt Lake City), but most active
operations are in sparsely populated (four people per square kilometer,
compared with a national average of 25 people per square kilometer) parts of
Arizona.
Nevada, South Dakota, and Montana were responsible for 85 percent of the
primary gold production in 1983 (excluding gold produced by Alaskan placer
operations). Other primary gold-producing states are California, Colorado,
Idaho, New Mexico, and Utah. Gold is also produced as a coproduct of silver
and copper mining in Utah, Nevada, and Arizona. Placer mines in Alaska and
gold heap leaching operations in Nevada are located in areas far removed from
population centers.
Almost all iron ore is mined in Minnesota and Michigan, although Texas,
Missouri, Utah, Wyoming, and California combined are responsible for
approximately 5 percent of all iron ore production. Primary lead production
in the United States is confined to Missouri, where lead mining is
concentrated in the Mark Twain National Forest (the average population density
in the southeastern part of the state is five people per square kilometer).
Lead is also recovered as a coproduct from some western mining operations.
Colorado is the primary molybdenum-producing state. Although silver is mined
2-6
-------
in many states, its production as a primary metal is concentrated in sparsely
populated areas of Idaho, Montana, Nevada, and Utah. Primary silver
production accounted for 70 percent of U.S. silver output in 1983, an increase
of 54 percent since 1978 (see Table 2-2). The remainder was produced as a
coproduct of copper, gold, lead, and other metals mining activities.
Uranium mining is concentrated in sparsely populated parts of New Mexico,
Wyoming, Colorado, and Utah. Zinc is produced in Tennessee, New York,
Missouri, New Jersey, Idaho, and Colorado; Missouri produces 21 percent of all
U.S. zinc as a coproduct of lead production. Zinc is also a coproduct of
silver production. Zinc mining in Tennessee and New York is located in
moderately populated areas (45 people per square kilometer in Tennessee and 16
people per square kilometer in New York). The largest Tennessee zinc mining
district is 50 kilometers from Knoxville.
The mining of metals in the other metals category is generally restricted
to the metal ore-producing states mentioned above. Additionally, California
produces tungsten and rare earth metals, and Arkansas produces bauxite for
metallurgical uses.
Asbestos mining is restricted to California and Vermont. The asbestos
mine in Vermont and one of the mines in California are in areas of moderate
population density. Phosphate mining is concentrated in Florida, North
Carolina, and Idaho. In Idaho, phosphate mining occurs in a sparsely
populated area; but in Florida, most phosphate operations are about 65
kilometers east of Tampa, in an area with a population density of 68 people
per square kilometer. Table 2-4 summarizes the number of operating mines and
percentage of 1983 production in each state, arranged by EPA region, for the
nonfuel mining segments covered in this report. Note that for some products,
a few mines are responsible for the majority of all primary production. For
2-7
-------
Table 2-4 Active Mines and Percentage of Production by State3 in 1983
ro
oo
States arranged
by EPA region
I
Vermont
II
New Jersey
New York
III
Pennsylvania
IV
Fl ori da
N. Carolina
Tennessee
V
Michigan
Minnesota
VI
N. Mexico
Texas
VII
Missouri
VIII
Colorado
Montana
S. Dakota
Utah
Wyoming
Copper Gold1* Iron ore Lead Molybdenum Silver Uranium Zinc Asbestos Phosphate
1(25)
1(8)
2(27)
1(8)
20(74)
-- -- 1(11)
1(1) - -- - -- - -- 7(51) -- 4(3)
2(25)
9(70)
2(11) 6(3) - — — 5(1) 20(25)
2(1) -- -- - 6(5)
1(2) 7(100)
20(4) -- -- 2(100) 5(6) 28(15) 1(6)
1(3) 16(10) -- -- - 9(17) -- - -- 1(1)
1(19) - - --
1(17) 1(2) 3(1) -- - 3(8) 23(13) - -- 1(1)
2(1) — -- — 22(40)
-------
Table 2-4 (Continued)3
States arranged
by EPA region Copper Gold** Iron ore Lead Molybdenum Silver Uranium
Zinc
Asbestos Phosphate
IX
Ari zona
Cal i form* a
Nevada
X
Alaska
Idaho
Washington
TOTAL NUMBER
OF MINES
20(68)
4(<1)
16(2)
45(56)
8(3)
1(4)
1(1)
10(14)
11(55)
1(3)
2(75)
5(11)
25(100) 117b(100) 20(100) 7(100) 2C(100) 51(100) 100(100) 12(100) 3(100) 32(100)
(£)
a Numbers in parentheses represent the percentage of primary product production. Percentages may not add to 100
because of rounding.
" Excludes placer operations.
c 1982 data.
Source: Charles River Associates 1985, based on data from BOM.
-------
example, two mines produce 75 percent of all U.S. asbestos, nine mines produce
70 percent of all iron ore, and seven mines are responsible for all lead ore
production.
2.3 MINING AND BENEFICIATION WASTES
In the nonfuel mining industry, the valuable portion of the crude ore is a
small fraction of the total volume of material that must be handled to obtain
it (Table 2-5). For example, over 6,900 units of material must be handled to
obtain one marketable unit of uranium. The high ratio of "material handled"
to "marketable product" is due primarily to the low percentage of metal in the
ore and to the mining methods and processes that must be employed. As shown
in Table 2-5, no metal exceeds 5 percent of the crude ore in which it is
embedded, except iron. Aluminum in metallurgical bauxite presents a similar
picture. As high-grade ore reserves continue to dwindle, these percentages
are likely to become even smaller. The fact that the materials handled
consist largely of waste or unusable materials distinguishes these mining
industry segments from many other process industries where waste materials
make up a relatively small portion of the materials processed to produce a
final product.
Several stages in the production of valuable products from minerals and
ores require the handling of large volumes of material, much of which is
waste. Overburden and waste rock must be removed to expose the ore. The ores
are then extracted (mined) and then transported to a nearby mill, where they
are beneficiated (concentrated or dressed). Mining and beneficiation
processes generate four categories of large-volume waste: mine waste,
tailings, dump and heap leach waste, and mine water.
Mining includes a variety of surface and underground procedures. Surface
2-10
-------
Table 2-5 Ratio of Material Handled to Units of
Marketable Metal and Estimated Percentage
of Metals in Ore
Mining
industry
segment
Copper
Gold
Iron ore
Lead
Mercury
Molybdenum
Silver
Tungsten
Uranium
Zinc
Ratio of material
handled to units of
marketable metal a»b
420:1
350,000:1
6:1
19:1
NA
NA
7,500:1
NA
6900:1
27:1
Typical
percentage of
metal in orec
0.6
0.0004
33.0
5.0
0.5
0.2
0.03
0.5
0.15
3.7
NA indicates not available.
a Excludes material from development and exploration activities.
Source: BOM 1983, and ° estimated by Charles River Associates 1985.
2-11
-------
mining methods include quarrying, and open-pit, open-cut, open-cast, dredging,
and strip mining. Underground mining creates adits (horizontal passages) or
shafts by room-and-pillar, block caving, timbered stope, open stope, and other
methods. Hydrometallurgical processes include heap, dump, vat, and in situ
leach mehods. (See Appendix D, Glossary, for a description of mining
methods.) The vast majority of nonfuel ores are mined on the surface. Only
antimony, lead, and zinc mining are solely underground operations. As shown
in Table 2-6, the industry segments that employ both methods handled more ore
in surface mines than in below-ground mines (with the exception of silver) in
1982.
Surface mining generates more waste than underground mining. Table 2-7
compares the waste and crude ore handled by the industry segments that mine
both above and below ground. (Reliable data were not available for iron
ore.) As shown, the volume of waste as a percentage of the total amount of
crude ore ranges from 9 to 27 percent for underground mines. In surface
mining, the amount of waste ranges from 2 to 10 times the total volume of
crude ore. Gold surface mining creates nearly 12 times as much waste per unit
of ore as underground gold mining; silver generates 59 times as much. All
mining methods used by the industry segments covered in this report generate
mine waste. It should be emphasized, though, that the typical percentage of
metal in an ore (excluding overburden and waste rock) is usually very low
(from a few percent to a fraction of a percent).
Mine waste is the soil or rock that mining operations generate during the
process of gaining access to an ore or mineral body, and includes the
overburden (consolidated or unconsolidated material overlying the mined area)
from surface mines, underground mine development rock (rock removed while
sinking shafts, accessing, or exploiting the ore body), and other waste rock,
2-12
-------
Table 2-6 Percentage of Crude Ore Handled at Surface
and Underground Mines in 1982, by Commodity
Mining industry segment Surface mines Underground mines
Metals:
Antimony — 100.0
Bauxite (aluminum) 100.0
Beryllium 100.0
Copper 87.6 12.4
Gold3 92.0 8.0
Iron ore 98.9 1.1
Lead — 100.0
Mercury 100.0
Molybdenum 100.0b W
Nickel 100.0
Rare earth metals 100.0
Silver 36.0 64.0
Titanium 100.0
Tungsten W 100.0C
Uranium 68.8 31.2
Vanadium 100.0
Zinc - 100.0
Average percent mined 69.7 30.4
Nonmetal s:
Asbestos 100.0
Phosphate rock 100.Ob —
Average percent mined 100.0 0
Average percent mined,
metals and nonmetal s 72.8 27.2
W indicates information withheld by Bureau of Mines to protect confidential
business information.
a Excludes placer operations.
b Includes underground operations; the Bureau of Mines does not publish
these data separately.
c Includes surface operations; the Bureau of Mines does not publish these
data separately.
Source: Adapted from BOM 1983.
2-13
-------
Table 2-7 Material Handled at Surface and Underground
Mines in 1982, for Selected Industry Segments
(in thousands of metric tons)
Mining
industry
segment
Copper
Gold
Silver
Uranium
Crude
ore
156,004
21,768
2,186
6,848
Surface
Waste
321,985
48,797
19,319
72,197
Underground
Waste/
crude ore
ratio
2.06
2.24
8.84
10.54
Crude
ore
22,040
1,896
3,891
3,111
Waste
1,968
369
584
848
Waste/
crude ore
ratio
0.09
0.19
0.15
0.27
Source: Adapted from BOM 1983.
2-14
-------
including the rock interbedded with the ore or mineral body. The particle
size of mine waste ranges from small clay particles (0.002 mm diameter) to
boulders (0.3 m diameter). Mine waste piles cover areas ranging from 2 to 240
hectares, with a mean area of 51 hectares (1 hectare equals 2.471 acres),
according to a U.S. Bureau of Mines (BOM) survey of 456 waste piles in the
copper, lead, zinc, gold, silver, and phosphate industry segments.
After the ore is mined, the first step in beneficiation is generally
grinding and crushing. The crushed ores are then concentrated to free the
valuable mineral and metal particles (termed values) from the matrix of less
valuable rock (called gangue). Beneficiation processes include physical/
chemical separation techniques such as gravity concentration, magnetic
separation, electrostatic separation, flotation, ion exchange, solvent
g
extraction, electrowinning, precipitation, and amalgamation. The choice of
beneficiation process depends on properties of the metal or mineral ore and
*
the gangue, the properties of other minerals or metals in the same ore, and
the relative costs of alternative methods. All processes generate tailings,
another type of waste.
Tailings are the waste materials remaining after physical or chemical
beneficiation operations remove the valuable constituents from the ore.
Tailings generally leave the mill as a slurry, consisting of 50 to 70 percent
(by weight) liquid mill effluent and 30 to 50 percent solids (clay, silt, and
sand-sized particles).
More than half of all mine tailings are disposed of in tailings ponds.
Use of tailings ponds is the primary method by which wastewater is treated in
the metals ore mining segment. Also, settling ponds are typically used at
mineral mining and processing operations. Pond size and design vary by
industry segment and mine location. Some copper tailings ponds in the
2-15
-------
southwest cover 240 to 400 hectares (one exceeds 2,000 hectares), while some
small lead/zinc tailings ponds cover less than 1 hectare. Based on a BOM
survey of 145 tailings ponds in the copper, lead, zinc, gold, silver, and
phosphate industries, the average size of these ponds is approximately 200
9
hectares. Many facilities use several ponds in series, which improves
treatment efficiency. Multiple-pond systems offer other advantages as well,
as the tailings themselves are often used to construct dams and dikes.
Technological advances since the turn of the century have made it
economically feasible to beneficiate ore taken from lower-grade ore deposits
(i.e., those with a much lower material-to-waste ratio). For example,
froth flotation beneficiation processes have had a tremendous effect on mine
production and on the amount and type of mine waste generated. Not only have
these advances increased mining production, but the volume of waste generated
also has risen dramatically. The tailings from froth flotation operations are
generally alkaline, because the froth flotation process is most efficient at a
higher pH. The metals in the alkaline tailing solids are therefore often
immobile, unless the conditions in the solids change over time.
Dump leaching, heap leaching and in situ leaching are other processes used
to extract metals from low-grade ore. In dump leaching, the material to be
leached is placed directly on the ground. Acid is applied, generally by
spraying, although many sulfide ores will generate acid during wetting. As
the liquid percolates through the ore, it leaches out metals, a process that
may take years or decades. The leachate, "pregnant" with the valuable metals,
is collected at the base of the pile and subjected to further processing to
recover the metal. Dump leach piles often cover hundreds of hectares, rise to
60 meters or more, and contain tens of millions of metric tons of low-grade
ore (overburden), which becomes waste after leaching. The dump leach site is
2-16
-------
often selected to take advantage of impermeable surfaces and to utilize the
natural slope of ridges and valleys for the collection of pregnant leach
solutions. Loss of leach solution is kept to a minimum in order to maximize
metal recovery.
Heap leaching operations are much smaller than dump leach operations,
generally employ a relatively impermeable pad under the leach material to
maximize recovery of the leachate, and usually take place over a period of
months rather than years. Heap leaching is generally used for ores of higher
grade or value. For gold ore, a cyanide solution is used as a leaching
solution, rather than acid. When leaching no longer produces economically
attractive quantities of valuable metals, and the sites are no longer in use,
the spent ore is often left in place or nearby without further treatment.
In situ leaching is employed in shattered or broken ore bodies on the
surface or in old underground workings. Leach solution is applied either by
piping or by percolation through overburden. Leach solution is then pumped
from collection sumps to a metal recovery or precipitation facility. In situ
leaching is most economical when the ore body is surrounded by an impervious
layer, which minimizes loss of leach solutions. However, when water is
sufficient as a leach solution, in situ leaching is economical even in
pervious strata.
Leaching processes are used most often in gold (cyanide leach), uranium
(water leach in situ), and copper operations (sulfuric acid).
The final waste type, mine water, is water that infiltrates a mine and
must be removed to facilitate mining. The quantity and quality of the mine
water handled varies from mine to mine; quantities may range from zero to
thousands of liters per ton of ore mined. The number of mine water ponds at
mine sites in the industry segments covered in this report is usually between
j . 11
one and six.
2-17
-------
2.4 WASTE QUANTITIES
Table 2-8 presents an estimate of the cumulative amount of tailings and
mine waste generated by the mining and beneficiation of metallic ores,
phosphate rock, and asbestos from 1910 through 1981. As shown, nearly
49 billion metric tons of waste have been generated by the mining and
beneficiation of eight metals and two nonmetals. Copper, iron ore, and
phosphate rock have produced over 85 percent of the total volume of waste.
Mining and beneficiating nonfuel ores and minerals generated approximately
12
2,000 million metric tons of waste in 1980. The waste handled in the U.S.
mining industry declined to 1,300 million metric tons for the industry as a
whole in 1982. The industry segments covered in this report are
responsible for more than 90 percent of this nonfuel mining waste. The 1980
and 1982 estimated waste volumes for each segment are shown in Table 2-9. The
copper mining segment alone generates approximately half of the waste produced
by the metal mining segments, and one-third of the total waste. The phosphate
mining industry is responsible for almost all waste from the nonmetal mining
segments, and more than 25 percent of all mining waste discussed. Iron ore
and uranium mining also generate large volumes of waste.
The waste for each mining segment is broken out by waste type for 1980 and
1982 in Tables 2-10 and 2-11, respectively. (Mine water quantities are
variable and difficult to estimate accurately, and are not shown on these
tables.) The waste tonnages shown in Tables 2-10 and 2-11 are estimates based
on primary production data. Over half of all mining waste generated in these
years was mine waste, and tailings accounted for slightly less than one-third
of the total amount of waste.
The phosphate rock, uranium, copper, and iron ore mining segments were, in
that order, the largest generators of mine waste in 1980, accounting for over
2-18
-------
Table 2-8 Estimated Cumulative Mine Waste
and Tailings Generated by the Mining and Beneficiation
of Metallic Ores, Phosphate Rock and Asbestos,
1910 Through 1981 (millions of metric tons)
Mining
industry
segment
Tailings
Mine waste
Total waste
Metals:
Copper
Gold
Iron ore
Lead
Molybdenum
Silver
Uranium
Zinc
Nonmetals;
Phosphate rock
Asbestos
TOTAL
,900
350
,000
480
500
50
180
730
2,200
40
14,430
17,000
400
8,500
50
370
30
2,000
70
5,500
30
33,950
23,900
750
11,500
530
870
80
2,180
800
7,700
70
48,380
Source: Estimated by Charles River Associates 1985, based on Coppa 1984, BOM
various years, and BOM 1980a.
2-19
-------
Table 2-9 Estimated Volume of Waste Generated by the Mining
and Beneficiation of Metallic Ores, Asbestos,
Phosphate Rock, and Overburden From Uranium Mining3
(millions of metric tons/year)
Mining industry segment 1980 1982
Metals;
Copper
Goldb
Iron ore
Lead
Molybdenum
Si 1ver
Uranium (mine waste only)
Zincc
Other metalsd
Subtotal 1,514 926
Monmetal s:
Asbestos
Phosphate rock
Subtotal
TOTAL
7
500
507
2,021
6
403
409
1,335
a Excludes mine water.
b Excludes placer operations.
c About 4 million metric tons of saleable products are extracted before
tailings disposal.
d Includes antimony, bauxite, beryllium, manganiferous ore, mercury,
platinum, rare earth metals, tin, tungsten, and vanadium.
Source: Estimated by Charles River Associates 1985 based on BOM 1981 a and
1983.
2-20
-------
Table 2-10 Estimated Volume of Waste Generated by the Mining
and Beneficiation of Metallic Ores, Phosphate Rock,
Asbestos, and Overburden from Uranium Mining in 1980a
(millions of metric tons)
Mining
industry
segment
Metals:
Copper
Gold*>
Iron ore
Lead
Molybdenum
Silver
Uranium
Zinc
Other metal sd
Subtotal
Nonmetals:
Asbestos
Phosphate rock
Subtotal
TOTAL
Mine waste
282
25
200
1
15
10
298
1
24
856
5
348
353
1,209
Waste
Tailings
241
10
150
10
31
3
NA
5C
5
455
2
152
154
609
production
Dump and
heap leach
wastes
200 (Dump)
3 (Heap)
--
--
—
-------
Table 2-11 Estimated Volume of Waste Generated by the Mining
and Beneficiation of Metallic Ores, Phosphate Rock,
Asbestos, and Overburden from Uranium Mining in 1982a
(millions of metric tons)
Waste production
Mining
industry
segment
Dump and
heap leach
Mine waste Tailings wastes
Total
Metals:
Copper
Goldb
Iron ore
Lead
Molybdenum
Si 1ver
Urani urn
Zinc
Other metal sd
Subtotal
Nonmetals:
408
178
24
75
9
6
6
NA
307
200 (Dump)
11 (Heap)
-------
93 percent of the total in that category. These four segments were also the
largest generators of mine waste in 1982, generating nearly 84 percent of the
total.
More than 89 percent of tailings wastes were generated by copper, iron
ore, and phosphate rock production in 1980; this percentage was almost 87
percent in 1982. Dump and heap leaching are confined to the copper, silver,
and gold segments. The gold segment generated less than 2 percent of all
leaching waste in 1980, but this increased to more than 5 percent in 1982.
This twofold rise in the volume of gold leaching waste was caused by an
increase in the use of the heap leaching method in this segment, a trend that
is likely to continue because of the increased value of the gold and the
decline in prices of many other metal commodities.
The wastes generated by the nonfuel mining industry are generally disposed
of on site, and thus the geographic distribution of active mining waste
management sites corresponds closely to the distribution of mine sites.
Transportation or treatment of these wastes beyond that practiced in
connection with wastewater treatment and disposal is not commonly practiced in
most segments. Accordingly, the principal mining states, i.e., Arizona
(copper), Minnesota (iron ore), New Mexico and Wyoming (uranium), and Florida
(phosphate rock), are the states that produce the majority of all mining
waste.
2.5 SUMMARY
The major categories of waste are mine waste and mine water from mining
operations, dump and heap leach wastes from leaching operations, and mill
tailings from the beneficiation (concentration) of ores. In situ leaching of
rock or in mines is performed in place. Annual waste generation totaled 2
2-23
-------
billion metric tons in 1980 and 1.0 billion metric tons in 1982 for the metal
mining segments and the phosphate and asbestos mining industries. Several
mining segments are geographically restricted: lead (100 percent in
Missouri); molybdenum (100 percent in Colorado); asbestos (75 percent in
California); phosphate (74 percent in Florida); iron (70 percent in
Minnesota); and copper (68 percent in Arizona). In both 1980 and 1982, the
three segments generating the largest amounts of waste were copper, phosphate,
and iron.
2-24
-------
SECTION 2 FOOTNOTES
1 BOM 1983.
2 BOM 1983.
3 U.S. Department of Commerce 1985.
4 All mines are not censused every year. Other mines in the nonmetals
industry segments include abrasives, asphalt, barite, boron minerals,
diatomite, feldspar, fluorspar, graphite, greensand marl, gypsum, kyanite,
lime, mica (scrap), perlite, potassium salts, pumice, salt, sodium
carbonate, stone, sulfur, talc, vermiculite, and wollastonite. Clay
and sand and gravel mines accounted for approximately 95 percent of all
nonmetal mines in 1982.
5 BOM 1981 a.
6 See also US EPA 1982a.
7 Mountain States Research and Development, Inc. 1981.
8 Mining and beneficiation methods are discussed in detail in EPA's final
Development Document for Effluent Limitations Guidelines and Standards for
the Ore Mining and Dressing Point Source Category.
9 BOM 1981b.
10 Martin and Mills 1976.
11 PEDCo Environmental, Inc. 1984.
12 Charles River Associates 1984a, based on BOM 1981a.
13 BOM 1984.
14 Charles River Associates 1985a.
2-25
-------
-------
SECTION 3
MANAGEMENT PRACTICES FOR MINING WASTES
3.1 OVERVIEW OF THE MINING WASTE MANAGEMENT PROCESS
Mine waste, tailings, heap and dump leach waste, and mine water can be
managed in a variety of ways. Figure 3-1 provides an overview of the mining
waste management process. As shown in the figure, mine waste may be used on
or off site, disposed of in mine waste piles, or used in leach operations to
recover additional valuable constituents from the ore. Similarly, tailings
may be used on or off site, disposed of in tailings ponds, or used in leach
operations to recover valuable constituents in the tailings that are still
present after milling processes have been completed. Tailings also may
contain residues of the reagents used in flotation processes. These reagents
include forms of cyanide (used in the leaching of gold and silver and in the
separation of sulfide minerals), sulfuric acid used and formed in copper dump
leaching, and various organic and inorganic compounds used in copper, lead and
2
zinc flotation.
Mine water may be discharged to surface streams {often after treatment)
via National Pollutant Discharge Elimination System (NPDES) permitted
outfalls, used as milling process makeup water (recycled), or used on site for
other purposes (e.g., dust control, drilling fluids, sluicing solids back to
the mine as backfill, etc.).
The recovery of valuable constituents from mine water (e.g., Ix treatment
for uranium), from mill process solids, or from extraction from dump leach
liquors could possibly be considered to be waste treatment processes, in that
3-1
-------
RECYCLE
NPDES
PERMITTED
DISCHARGE
OTHER
ONSITE
UTILIZATION
I WATER I
MINE
X
1
1
r
. V
BACKFILL
OFFSITE
UTILIZATION
RECOVERY
(LEACH
OPERATIONS)
Figure 3-1 The mining waste management process
-------
such recovery extracts metals or constituents that would otherwise be
potentially hazardous or constituents of waste prior to disposal. However,
the mining industry considers these processes to be extraction or
beneficiation processes because they recover valuable products from materials
that have metal concentrations below those in ore of a grade suitable or
economical for milling and smelting.
Table 3-1 presents the volumes and percentages of mine waste and tailings
that are currently managed according to the various practices shown in
Figure 3-1 and mentioned above. The table shows that more than half of all
mine waste and tailings is disposed of in piles and ponds, respectively.
Most onsite utilization of mine waste and tailings involves the dump leaching
of copper mine waste and the use of sand tailings to build tailings
impoundment dams in all industry segments.
The remainder of this section is divided into three parts. Section 3.2
describes waste management practices other than actual disposal. The section
includes a discussion of recovery operations, process changes for waste volume
reduction, waste treatment methods, onsite utilization of mine water, and
offsite use of mine waste and mill tailings. It shows that although several
alternatives to onsite land disposal of mining industry wastes are available,
their effectiveness in reducing the amount of mining industry wastes is
1 i mi ted.
Section 3.3 describes some general considerations for locating waste
disposal sites and specific aspects of waste disposal for tailings, mine
waste, leached material, and mine water.
Section 3.4 examines the measures that can be used to limit or mitigate
the hazards posed by mining industry wastes that are disposed of on site.
3-3
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Table 3-1 Current Waste Management Practices
Waste type
Mine waste
Tailings
Management
practi ce
Pile
Onsite utilization
Backfill
Off site utilization
Total
Ponds
Onsite utilization
Backfill
Off site utilization
Total
Vol ume
(in millions
of metric tons
per year)
569
313a
86
43
1,011
267
141b
21
8C
437
Percent
of waste
generated
56
31
9
4
100
61
32
5
2
100
alncludes dump leach operations and starter dams for tailings
impoundments.
^Includes the sand fraction used in building tailings
impoundment dams.
clncludes 4 million metric tons of Tennessee zinc tailings
sold as construction materials or soil supplements.
Source: Charles River Associates 1984a, based on U.S. Bureau of Mines data,
3-4
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These measures are particularly important because most of the large volume of
mining industry wastes will ultimately remain on or near the site. The
mitigative measures considered are broadly categorized under inspection and
detection measures, liquid control systems, and corrective action measures.
3.2 WASTE MANAGEMENT PRACTICES
Waste management practices include process modifications for waste or
potential hazard minimization, recovery operations, treatment prior to land
disposal, onsite use of mine water, and offsite use of mine waste and mill
tailings. Each of these practices is discussed below.
3.2.1 Process Modifications for Waste Minimization
Although there are no practical means of reducing the volume of solid
waste produced by mining and beneficiation operations, some changes in
beneficiation processes can lead to changes in the chemical composition of the
tailings released into tailings impoundments. For example, pilot studies have
been conducted in which nontoxic reagents were substituted for cyanide
compounds in the beneficiation of copper ores. Sodium sulfide and sodium
bisulfide may be used as alternatives to sodium cyanide (see 47 FR 25693,
June 14, 1982). Similarly, alkalinity in the beneficiation circuits can be
maintained by reagents less toxic than ammonia. Lime is the reagent of choice
in most instances, although some scaling has been reported.
Two copper mills have circuits separating pyritic material from sulfide
ores to improve subsequent copper recovery. The pyrites are currently
discharged to the tailings impoundments, but they could be segregated. If
pyrites were not codisposed of with other gangue material, there would be a
reduction in the potential for acid formation after closure of the tailings
impoundment. However, the alkaline tailings and pond water may act to reduce
this potential.
3-5
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The thickened discharge method of tailings management involves partially
dewatering the tailings slurry and discharging it from a single point. This
results in a gently sloping, cone-shaped deposit. The water removed from the
tailings can be treated and discharged or returned to the milling circuit.
The dewatering costs associated with this method are offset by reduced
earthwork costs. A disadvantage of the thickened discharge technique in some
circumstances is that no water is stored with the tailings, which may mean
that the dewatered slurry piles become sources of fugitive dust. The particle
size distribution of the waste and the drying characteristics of the disposal
area are important factors in determining the potential for fugitive dust
emissions. Earthquake activity may also affect the stability of the dewatered
slurry piles, depending on the location. The thickened discharge method is
currently used to dispose of sand tailings in the Florida phosphate industry
4 5
segment, and could be applied to other sectors. '
Biological acid leaching, a new process under development in Canada, may
be a feasible substitute for current dump leaching practices. Unlike dump
leaching operations, the new process does not convert the sulfur in the ore to
sulfuric acid; instead, it converts it to elemental sulfur, which is both less
hazardous to the environment and potentially saleable. The process is still
in the pilot development stage; the economic and technical feasibility of
large-scale operations of this type have not yet been demonstrated.
3.2.2 Recovery Operations
Leaching is a process used to recover metal values from low-grade ore or
tailings, and is a common practice in some mining segments (i.e., copper,
gold, silver, and uranium). There are several types of leaching operations
practiced, including in situ, dump, heap, and vat leaching. Acid solutions
are commonly used for leaching in the copper segment of the mining industry.
3-6
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Cyanide solutions are used to leach both gold and silver wastes as well as
ores. The precious metals in cyanide leach solutions are removed in the
process, and the partially spent cyanide solution is recycled back to the
process for reuse. Leaching of phosphate rock and uranium wastes are also
practiced. In situ leaching in the uranium segment is practiced with water
as the leach solution.
The purpose of using leaching techniques is to recover valuable metals
from ores that would otherwise be uneconomical to mine. In situ and dump
leaching techniques may cause environmental problems, in that an impermeable
layer is not always placed or located between the low-grade ore and the
surrounding soil, especially at older operations. However, it is in the
miner's best interest to capture as much of the leachate in order to recover
the metal values. The benefits of leaching are improved natural resource
utilization and increased production of valuable metals such as gold, silver,
and copper. The drawbacks of leaching, especially dump and in situ leaching,
are that potentially corrosive (low-pH) or toxic (cyanide and/or toxic metals)
products may seep into the ground below these operations. In ores that would
naturally form acid drainage, leaching operations allow recovery of metals
from ores that would naturally release these metals over a period of time.
In the copper, gold, and silver industries, technical efficiency and
economic factors have made the recovery of mineral values by leaching
processes economically feasible. Overburden, tailings, and other wastes will
continue to be "remined" in the future, if extraction efficiencies continue to
improve and if product prices exceed extraction costs.
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Techniques other than leaching have been developed to recover valuable
constituents from mine and mill wastes. Flotation can be used with copper
g
mine waste, taconite (iron) tailings, and zinc mine waste.
Pilot-scale research projects have also shown that it is technically
feasible to use a high gradient magnetic separation process to produce an
anorthosite concentrate, assaying at more than 28 percent alumina (Al20.j),
from copper tailings. However, this has not proved economically competitive
g
with alumina produced from bauxite by the Bayer process.
3.2.3 Waste Treatment
Various oxidation systems have been developed to destroy cyanide compounds
prior to discharge; however, most of the cyanide in cyanide leach processes is
recycled back to the process for reuse. One system uses sodium hypochlorite
and sodium hydroxide; another uses chlorine and sodium hydroxide. Other
processes have been used, including hydrogen peroxide oxidation, potassium
permanganate, and chlorine dioxide. Destroying the cyanide used to leach
metals may be feasible, using the new peroxide-thiosulfate process currently
being developed by the Bureau of Mines (BOM). In this method, hydrogen
peroxide and sodium thiosulfate convert free and weakly complexed cyanide to
thiocyanate. After the remaining complexed cyanide is precipitated and
flocculated, the solution is filtered. Copper, iron, and other base metals
associated with the gold and silver ore are removed along with the cyanide.
However, thiocyanates have been shown to have latent toxic effects on fish;
thiocyanate apparently accumulates in fish, only to be released in lethal form
12
when the fish are stressed.
Cyanide levels in froth flotation wastewater are generally low, and are
the result of using cyanide to depress pyrites in the circuit. Ultraviolet
radiation (from the sun) and simple aeration are often adequate to reduce the
cyanide levels to detection levels.
3-8
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Neutralization is a technically feasible method of treating corrosive
acidic wastes. Chemical agents commonly used for this purpose include
quicklime, limestone, hydrated or slaked lime, caustic soda, soda ash, and
13
hydrated ammonia.
The Effluent Limitations Guidelines and New Source Performance Standards
for the ore mining and dressing point source category endorse the use of lime
to maintain discharges within the 6.0 to 9.0 pH range. In fact, the permit
issuer may allow the pH level in the final effluent to exceed 9.0 slightly, if
that is required to meet discharge limitations for copper, lead, zinc,
mercury, and cadmium.
Treatment of acidified mine waste or tailings is often a necessary
prerequisite for revegetation. Hydrated lime or quicklime is used to increase
the pH to 9.0 rapidly. For a slower but longer-lasting response, agricultural
lime (limestone) is used. The lime is added in quantities great enough to
neutralize the sulfuric acid that will be released by the future oxidation of
14
pyritic material in the mine or mill waste.
3.2.4 Onsite Use of Mine Water
Water generated by mine dewatering may be used in the milling process as
makeup water (treatment may or may not be required), or used on site for dust
control, sluicing solids to the mine as backfill or in cooling or drilling
fluids. Depending on the water balance at a facility, managing the mine water
may involve a combination of these uses. A large number of mining and
beneficiation operations use mine water in the mill. In some cases, all of
the water required by the mill operation is obtained from mine drainage, which
eliminates the need for wells and a mine water treatment system, or greatly
reduces the volume of mine water discharged. Using mine water containing
3-9
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relatively high concentrations of soluble metals for beneficiation makeup
water is an effective treatment practice, because flotation circuits, which
are typically alkaline, reduce the solubility of metals and thereby facilitate
their recovery. In most cases, however, not all of the mine water is used in
the beneficiating operations, because operators have little or no control over
the quantity of water that infiltrates the mine. The unused portion of the
mine water is generally stored in impoundments and discharged after treatment,
in accordance with the provisions of an NPDES permit.
3.2.5 Offsite Use of Mine Waste and Mill Tailings
Waste utilization practices include agricultural lime replacement, road
and building construction, and the production of bricks, ceramics, and
wallboard. These methods are discussed below and summarized in Table 3-2.
The most widespread use for these wastes is in the production of concrete
and bituminous aggregates for road construction. Other applications in road
construction include the use of these wastes in road bases, as embankments,
and to make antiskid surfaces. Approximately 50 percent of the zinc tailings
in Tennessee are sold for aggregate production.
Tennessee zinc tailings also may be used as a substitute for mortar or
agricultural limestone; nearly 40 percent of these tailings are sold for these
purposes. Tailings from mills processing zinc ores in New York and the Rocky
Mountain states are not suitable as soil supplements, because these tailings
have lower concentrations of calcium carbonate and higher concentrations of
lead and cadmium. Similar concerns constrain the use of lead tailings in
Missouri.16
Tailings from asbestos and molybdenum mining operations have been used in
asphalt mixes for roads and parking lots. Phosphate, gold, and silver
3-10
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Table 3-2 Uses of Mine Waste and Tailings
Use Asbestos
Material Use
Soil Supplement
Wall Board Production 3
Brick/Block Production 1
Ceramic Products
Anti-Skid Aggregate
Embankments
General Aggregate
Fill or Pavement Base
Asphalt Aggregate 2
Concrete Aggregate
Gold &
Copper silver
1 1
3 3
3
3 3
3
Iron ore/
taconi te
1
3
3
3
3
3
3
Lead Molybdenum
3
3
3
3 3
3
Phosphate
1
1
1
Uranium Zinc
1
1 3
3
•_, Development Stage
1. Bench-scale research project
2. Full-scale demonstration project
3. Full-scale, sporadically practiced
Source: Based on Seitter and Hunt 1982.
-------
tailings of sand and gravel size have been mixed with cement to form concrete
for use in road construction. Lead, zinc, and iron ore tailings have been
used for both concrete and bituminous aggregates. Mixtures of crushed waste
rock, including waste material from copper, iron ore, lead, gold, and silver
mines, have become embankments, fills, or pavement bases for many highways.
Topsoil must be deposited over fills and embankments made with these materials
to control erosion and permit the growth of vegetation. Taconite tailings
have proved valuable as thin (less than 25 mm) road surface overlays, because
they greatly enhance skid resistance.
The use of tailings to produce bricks, blocks, and ceramic products has
not yet passed the bench-scale research stage. Copper mill tailings can be
used in brick production if pyrites are first removed. Lightweight blocks
made from taconite tailings have good structural characteristics but have not
been marketed.
The most important constraints on the use of mining wastes are imposed by
energy, economic, and logistic considerations. Material/metal recovery from
mining wastes is economically attractive only when the price of the material
recovered exceeds the costs of extraction. In recent years, mine product
prices have been generally depressed, and extraction costs, especially
energy-related costs, have risen. Similarly, using mining wastes to produce
bricks or to construct roads is affected by such market constraints as
transportation costs and competition with other sources located nearer to
potential users. Mining wastes, therefore, are competitive only when they
can be marketed or used in the geographical area close to the originating mine.
Uses of mining wastes do not and will not keep pace with the approximately
1 to 2 billion metric tons of these wastes that may be generated each year.
Long-term management of mining waste disposal sites will continue to be
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necessary for the foreseeable future. However, research on the cost-effective
utilization of mining wastes is justified, because any new use that becomes
widely practiced will help reduce the magnitude of the mining waste disposal
problem.
3.3 WASTE SITING AND DISPOSAL METHODS
For technical and economic reasons, most mining waste is finally disposed
of on the land. The primary considerations for locating a waste disposal area
are discussed below. Specific waste disposal methods for mining wastes are
also described.
3.3.1 Location and Siting
The topography, geography, and hydrogeology and, in some cases,
meteorology, as well as population density of the geographical area in which a
mine is located, affect the siting of the waste disposal area, the extent to
which mitigative practices are required, and the types of mitigative systems
that can be selected. The extent of the ore body, the quantity of waste to be
generated, and the method of mining are also considered when siting a disposal
area.
Owners and operators of mines built before 1970 generally located waste
sites at the shortest and most easily traversed distance from the mine or
mill, usually in a ravine or gully. Owners and operators of mines constructed
since 1970 (when Federal and state environmental regulation greatly increased)
have also considered the potential pollution problems associated with
particular sites, such as siltation of surface waters, production of fugitive
dust emissions, and contamination of ground water. Disposal locations chosen
based on these considerations may have small upgradient drainage areas to
3-13
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reduce erosion potential, or may be underlain by impermeable strata to
minimize percolation into ground water.
3.3.2 Waste Disposal Methods for Tailings
18
Waste disposal methods for tailings include: tailings ponds, stope
backfilling, below-grade disposal, and offshore disposal. As was shown in
Table 3-1, more than half of the tailings are disposed of in tailings ponds.
The size and design of the ponds vary widely by industry segment and
location. Tailings disposal methods are discussed below.
(1) Tailings Impoundments. Tailings impoundments have been used at ore
mills in the United States since the early 1900s. In recent years, they have
become increasingly important and may account for as much as 20 percent of the
1 g
construction cost of a mine/mill project. Some ore bodies may not be
exploited, because suitable sites for tailings disposal are not available
within a practical distance.
Tailings impoundments may serve several purposes. They retain water,
making it available for recycling to the mill flotation circuits and other
processes requiring water. They act as equilization basins, which assist in
wastewater treatment process control and reagent addition control. They also
protect the quality of surface waterways by preventing the release of
suspended solids and dissolved chemicals. In fact, tailings impoundments in
arid regions may permit a mill to achieve "zero discharge," eliminating the
need for a point source discharge permit.
The design and construction of a tailings impoundment reflect the
characteristics of the ore, the mine/mill, and the environment, especially the
local topography. Three methods of dam building are commonly used:
downstream, upstream, and centerline. Figure 3-2 depicts these methods.
3-14
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UPSTREAM METHOD
PERIPHERAL TAILINGS
SPIGOT OR CYCLONE
PERIMETER DIKES
(NATURAL SOILS OR TAILINGS)
POND WATER
TAILINGS
STARTER DIKE
(NATURAL SOILS)
DOWNSTREAM METHOD
IMPERVIOUS CORE
(OPTIONAL)
TAILINGS OR
WATER
STARTER DIKE
(NATURAL SOILS)
RAISES (NATURAL SOILS,
TAILINGS, OR MINE WASTE)
DRAIN
(OPTIONAL)
CENTERLINE METHOD
PERIPHERAL TAILINGS
SPIGOT OR CYCLONE
TAILINGS
IMPERVIOUS CARE (OPTIONAL)
RAISES (NATURAL SOILS,
TAILINGS, OR MINE WASTE)
STARTER DIKE
(NATURAL SOILS)
DRAIN
(OPTIONAL)
Source: Vick 1981
Figure 3-2 Tailings dam construction methods
3-15
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A common element in all three types is that they are usually raised
sequentially as the level of tailings and/or effluent in the impoundment
rises, in order to distribute construction costs more evenly over the life of
20
the facility.
With the downstream construction method, the embankment building material
is added successively to the downstream side of the previously placed
embankment, and the crest thus moves downstream. This system is costly but is
compatible with any type of tailings and can be used for water storage. The
upstream method is less costly but is not well suited to large inflows and
water storage. The centerline method involves raising the dam in steps, with
21
the centerline of the crest remaining above the starter dam.
The starter dam or dike is typically built with natural soils, but mine
waste can also be used. Subsequent increments are added from the coarse,
sandy fraction of the tailings. This use of tailings constitutes the largest
component of the 141 million metric tons of onsite utilization of tailings
shown in Table 3-1. Installation of internal filters and drains lowers the
water level within the sand dam and reduces the danger of overtopping,
22
instability, or breaks induced by seismic (earthquake) activity. Other
protective measures include reduction of the catchment area by maintaining
diversion ditches around the impoundment and careful control of water inflow
23
and outflow to allow for seasonal and mill operation variations. In
summary, many tailings ponds and impoundments require some degree of seepage
to maintain their structural integrity.
Upstream embankments are widely used by the copper industry in the
southwest. Earthquake activity and high precipitation along the West Coast
have fostered use of downstream and centerline dams. Downstream dams are also
favored by the lead industry in Missouri and the phosphate industry in Florida.
3-16
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(2) Stope Backfilling. This method, also referred to as sandfilling,
involves converting a portion of the coarse fraction of tailings into a slurry
and then injecting the slurry into the mined-out portions of stopes. Stope
backfilling is currently practiced or is being considered as a method of
disposing of such diverse materials as copper tailings, spent shale from oil
24
shale retorts, and tailings from Wyoming trona (sodium carbonate) mines.
The major disadvantages of stope backfilling are the introduction of
additional water into the mine, which results in occasional spills of
tailings, and the importation of supplemental waste material to make tailings
embankments when too much coarse fraction has been removed from the tailings.
The primary drawback to backfilling with fines (materials with small particle
sizes) is the risk of poor drainage of the backfill material. In addition,
although no supporting monitoring data are available, backfilling of tailings
into underground mines may have an adverse impact on ground-water quality.
For example, metals or other constituents may leach from the coarse tailings
and reach the ground water when seepage from the backfilled stopes
25
occurs. This possibility increases when the coarse tailings contain
pyrites, which generate sulfuric acid that decreases pH and increases the
solubility of most toxic metals.
Stope backfilling as a tailings management alternative is not used on a
national scale, because most of the industry segments covered in this report
excavate their ores using surface mining techniques.
(3) Below-Grade Disposal. This method of tailings disposal consists of
placing tailings in an excavated pit (in lieu of above-grade impoundments) so
that at closure, the entire deposit is below the level of the original land
surface. This method currently is unique to the uranium industry, which uses
3-17
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it to reduce the likelihood of erosion. The embankments of conventional
above-grade surface impoundments are subject to erosion and failure that could
result in the release of tailings to the downgradient area. Below-grade
disposal avoids both of these potential problems. This disposal method is
26 27
costly unless mined-out pits can be used. ' This method could be used
for operations involving open-pit mining if a series of mined-out pits is
available to receive mill tailings (or retorted shale).
(4) Offshore Disposal. In the past, offshore disposal has been a
euphemism for dumping tailings into a large lake or the ocean without regard
for environmental consequences. Recently, more responsible proposals have
shown that if the tailings are chemically innocuous, are sufficiently coarse
to settle rapidly with a minimum amount of turbidity, and are piped to
deep-water areas to avoid the most biologically productive nearshore zones,
offshore disposal may have reasonably small environmental impacts in certain
specific cases. Even so, offshore disposal is not a widely accepted
alternative within regulatory agencies in the United States and Canada, and
few mines have been located near the ocean in the past. Technical arguments
notwithstanding, recent experience indicates that most developed countries
28
will not approve offshore disposal of tailings.
3.3.3 Waste Disposal Methods for Mine Waste
As was shown in Table 3-1, an estimated 56 percent of the mine waste
removed to gain access to an ore body is disposed of in mine waste piles near
or adjacent to the mine. The overburden from open pit mines is usually
discarded on the outside slopes of the pit. Approximately 9 percent of the
mine waste is disposed of as part of the normal mining practice of immediately
backfilling previously excavated areas; the trend in the mining industry is
3-18
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toward increasing this percentage. In surface mining, however, backfilling is
only used when the overburden can be placed into adjacent areas that have been
excavated. With some underground mining methods, waste rock is backfilled
into previously mined sections as it is excavated, which eliminates the time
and expense of hauling the material to the surface for stockpiling. These
mining methods include cut-and-fill stoping and square-set stoping. These
methods provide structural stability to the mined areas, in addition to
29
serving as a means of waste disposal.
3.3.4 Waste Disposal Methods for Dump Leach/Heap Leach Material
Whether or not active dump leach and heap leach operations are considered
to be process operations rather than solid waste disposal practices, solid
waste material remains after the completion of these operations. The current
practice is to transport overburden and low-grade copper ore for dump leach
processes (or waste and low-grade precious metal ore for heap leach
operations) to leaching beds, where the dumped material is spread by
bulldozers. Equipment travel on the leach dump compacts the top layer of the
material; this layer is then scarified to facilitate infiltration of the leach
solution. This process of layering and subsequent scarifying of the leach
dump may continue for 50 years or more. The leached waste material is not
removed from the site of the operation, due to the immense size of these piles.
3.3.5 Waste Disposal Methods for Mine Water
Water produced from mine dewatering may be discharged directly or
indirectly (after treatment such as settling) to a surface stream, used in the
milling process as makeup water (treatment may or may not be required), pumped
to a tailings pond, or used on site for dust control, cooling, or as drilling
fluids, etc. (see Section 3.2.4). Depending on the water balance of the
3-19
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particular mine facility, mine water management may involve one or a
combination of these methods.
Treatment of mine water in onsite impoundments is the management practice
used when discharge or total recycling are not possible. Such treatments
include simple settling, precipitation, the addition of coagulants and
flocculants, or the removal of certain species (e.g., radium-226 removal by
coprecipi tation with barium chloride in mine water ponds in the uranium
industry). Most mine water ponds are relatively small, shallow, excavated,
unlined impoundments. The number of impoundments and their size depends on
the volume of mine water handled and the treatment methods used. Larger
impoundments or several impoundments in series are used to provide sufficient
retention time for effective treatment. Discharge from mine water treatment
31
ponds is usually to a surface stream via an NPDES-permitted outfall.
3.4 MITIGATIVE MEASURES FOR LAND DISPOSAL SITES
Even if greater use is made of waste utilization and alternative waste
disposal methods, the greatest portion of mining wastes will still be disposed
of in land disposal facilities such as waste piles, tailings ponds, and
settling impoundments. However, various measures are available to detect or
mitigate the problems associated with the land disposal of mining wastes.
These measures may be classified into four general types:
1. Detection and inspection measures determine whether problems are
developing. These activities include ground-water monitoring and
visual inspection of other systems, erosion control, dam stability,
and runoff control.
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2. Liquid control measures control the potential for liquid to come into
contact with mining waste, and thus minimize surface water pollution
and the amount of liquid available for leachate formation.
3. Containment systems prevent leachate from entering the ground water
and posing a threat to human health and the environment. Two types
of containment systems are considered here: containment systems
designed to prevent leachate from entering the ground water (such as
liners and systems designed to control plumes of contaminated ground
water) and corrective action measures.
4. Security systems prevent entry to the waste management area by
animals or by unauthorized persons. These systems protect the
general public and prevent activities that might damage onsite
control systems.
The waste management measures that are most relevant to individual waste
management sites depend, in part, on the operational phase of the waste
management site. Three operational phases are distinguished here:
1. Active site life is the period during which waste is being added to
the disposal site. A disposal site may be closed even though the
mine itself remains active.
2. Closure is the period immediately following active site life, in
which various activities are undertaken to ensure adequate protection
of human health and the environment during the post-closure phase,
and to minimize maintenance activities in the post-closure phase.
3. Post-closure is the period following closure during which there are
no further additions of waste to the site. The main post-closure
activities are the monitoring of the site for leaks and the
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maintenance of liquid control, containment, and security systems
established during site life or at the time of closure.
Corrective action occurs after a plume of contaminated ground water or another
environmental hazard is discovered. This may occur during active site life,
at the time of closure, or during the post-closure phase.
The remainder of this section describes various mitigative measures appro-
priate to the management of mining waste during the active life of the site,
the closure period, and the post-closure phase, and discusses appropriate
corrective measures. Some of the measures described can be substituted for
each other. In most cases, the ability of these measures, or combinations of
measures, to limit threats to human health and the environment depends on
specific site conditions; in addition, many of these measures have yet to be
applied in the mining waste context. The discussion below describes the
purposes and limitations of various management techniques, but data are not
available to allow the efficacy of these techniques to be quantified. Table
3-3 shows the various measures discussed in this section, classified by
operational phase of the site.
Where possible, EPA has estimated the percentage of mines in some industry
segments where the following mitigative measures are currently used: ground-
water monitoring, run-on/runoff controls for storm water, liners for tailings
ponds, secondary leachate collection and removal, and closure procedures. EPA
produced these estimates using the methodology described in Appendix B.
3.4.1 Mitigative Measures During Active Site Life
During the active life of a waste disposal facility, waste is continually
being added to the waste material already at the site. The ongoing nature of
the disposal process at active sites makes certain mitigative measures
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Table 3-3 Mitigative Measures by Stage of Site Life
Stage of
site life
Mitigative measure
Purpose
Active
site life
Closure
Hydrogeologic evaluation and
ground-water monitoring
Run-on/runoff control
Liners
Cutoff walls
Leachate collection, removal,
and treatment systems
Security systems
Continue measures initiated
during active site life
Wastewater treatment
Pond sediment removal
Dike stabilization
Waste stabilization
Installation of leachate
collection, removal and
treatment systems at surface
impoundments
Final cover
Detection of contaminants
Liquid control
Containment
Containment
Liquid control
Security of control systems
and protection of public
health
All purposes mentioned
above
Liquid control
Waste removal
Liquid control
Liquid control
Liquid control
Liquid control
Post-closure
Ground-water monitoring
Inspect/maintain all
existing systems
Detection of contaminants
All purposes mentioned
above
Corrective
action
Interceptor wells
Hydraulic barriers
Grouting
Cutoff walls
Collection
Containment
Containment
Containment
Containment
Treatment
Source: Meridian Research, Inc. 1985.
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inappropriate for use at such sites. For example, methods such as caps or
covers that are designed to control the volume of liquids percolating into the
site cannot be used. Similarly, liners and containment systems that underlie
the waste area can most easily be put in place at new facilities. However,
other mitigative measures, such as those discussed below, can be used at
existing active waste disposal sites.
3.4.1.1 Ground-Water Monitoring and Hydrogeological Evaluation
The objectives of hydrogeological evaluation and ground-water monitoring
at a waste disposal or tailings pond facility are (1) to identify potential
pathways of leakage and contaminant transport by ground water; (2) to
determine whether contamination of the ground water has occurred and, if so,
the extent of contamination; and (3) if necessary, to generate the data needed
to select and implement a mitigative strategy. At new facilities, the first
step in this process is to evaluate the pollution potential of effluents from
32
the site. A thorough hydrogeological evaluation and ground-water
monitoring program are then conducted to characterize background or natural
conditions at the site. In some cases, it may be necessary, prior to siting
the monitoring wells, to simulate baseline and potential ground-water pathways
33
by means of hydraulic or solute transport models. Particularly in areas
close to dams or dikes, hydrogeological evaluations are necessary to determine
probable seepage paths and to establish flow rates to be used in the design of
dikes, cutoff walls, and liners. Ground-water monitoring is also an important
means of evaluating the initial and long-term effectiveness of the engineering
and site preparation measures used at a particular site.
Depending on the specific characteristics and requirements of a given
site, monitoring programs range in complexity from a simple determination of
3-24
-------
the presence or absence of a particular waste constituent in a few wells to an
extensive analysis of many constituents in many wells, using well clusters
34 35
open at different depths, aquifer tests, and geophysical measurements. '
The complexity of an effective ground-water monitoring program is directly
related to the size of the waste management project, the nature of the waste
materials, and the characteristics of the local hydrogeology.
Using ground-water monitoring to assess conditions at a site has some
limitations. Because a monitoring well characterizes only one point in an
aquifer, results obtained at the well may not be representative of site
conditions, especially in geologically complex areas. Another limitation of
ground-water monitoring is that some knowledge of site conditions, such as
ground-water flow rate and direction, is necessary before the monitoring wells
can be placed properly. In addition, because ground-water flow is extremely
slow, long-term monitoring over several months or years may be required to
characterize the situation accurately. In some circumstances, the flow
patterns of ground water through fractures may be sufficiently complex to
36 37
frustrate even the most intensive monitoring effort. '
Waste disposal facilities in the mining industry are so large that
horizontal and vertical distances between hydraulically upgradient, and
therefore unimpacted, areas and areas that are downgradient, and therefore
likely to be impacted, can be very great. The variation in natural conditions
over such large distances (thousands of meters) can greatly complicate
hydrogeological studies. In some cases, the presence of several active,
inactive, or abandoned waste disposal sites or mines in the area also
complicates ground-water quality and flow patterns, making ground-water
38 39
monitoring and hydrogeologic evaluation more difficult. *
3-25
-------
Nevertheless, hydrogeologic evaluation and ground-water monitoring remain
the only methods for determining whether there is a danger of offsite movement
of contamination from mining wastes. Because of the size and complexity of
many mining waste sites, the need for detailed hydrogeologic evaluation and
careful interpretation of ground-water monitoring results may be greater than
for other types of hazardous waste management facilities.
Tables 3-4 and 3-5 show the extent to which ground-water monitoring,
practiced voluntarily or in compliance with State regulations and adequate to
satisfy current RCRA requirements, is performed at heap/dump leach operations
and tailings ponds in the various mining industry segments. (Ground-water
monitoring is not normally performed at mine waste disposal sites.)
Ground-water monitoring of gold and silver heap leach operations adequate to
satsify current RCRA requirements is currently practiced at all of the gold
and silver mine sites studied by EPA where there are heap leach operations.
Ground-water monitoring adequate to satisfy RCRA requirements is currently
practiced at two of the nine copper dump leach operations studied by EPA.
Monitoring of ground water is also practiced at all of the gold and silver
tailings ponds and at 2 of the 12 copper tailings ponds studied by EPA. It is
not performed at any of the lead or zinc tailings ponds studied by EPA.
3.4.1.2 Run-on/Runoff Controls
Run-on/runoff controls can be divided into three categories: diversion
methods, containment systems, and runoff acceleration practices. Diversion
systems prevent offsite water from entering the site and causing erosion and
flooding. Containment involves the collection of onsite stormwater or dike
seepage in holding or evaporation ponds for the treatment necessary for final
disposal or to prepare the waste for recycling.
3-26
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Table 3-4 Extent of Ground-Water Monitoring of Heap/Dump
Leach Waste, by Industry Segment
Number of mine
sites in data base
Mining that generate
industry heap/dump
segment leach waste
Number of mine
sites that monitor
ground water at
heap/dump leach
waste operations9
States requiring
ground-water monitoring
or having mine sites
that monitor ground water
at heap/dump leach waste
operations"'0
Copper
Gold
9
5
2 (22%)
5 (100%)
Arizona, New Mexico
Montana, Nevada, Colorado,
Si 1ver
1 (100%)
New Mexico, South Dakota
Nevada
a Sites are identified as having ground-water monitoring only when such
monitoring is adequate to satisfy current RCRA requirements.
b This column includes only those states where ground-water monitoring
requirements are at least as stringent as required by RCRA.
c This column includes only the states generating large amounts of mining
industry waste in the affected industry sectors.
Source: Charles River Associates 1984 and 1985c.
3-27
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Table 3-5 Extent of Ground-Water Monitoring
of Tailings Ponds, by Industry Segment
Number of
mine sites
Mining in data
industry that generate
segment tailings
Copper 12
Gold 7
Lead 6
Phosphate 8
Si 1 ver 8
Zinc 6
Number of States requiring
mine sites ground-water monitoring
that monitor or having mine sites
ground water at that monitor ground water
tailings ponds3 at taili'-gs pondsb»c
2 (17%) New Mexico, Colorado,
California, Arizona
7 (100%) Arizona, South Dakota,
Nevada
0
1 (13%) Florida, North Carolina
8 (100%) Montana, Idaho,
Colorado, Utah
0
a Sites are identified as having ground-water monitoring only when such
monitoring is adequate to satisfy current RCRA requirements.
b This column includes only those states where ground-water monitoring
requirements are at least as stringent as required by RCRA.
c This column includes only the states generating large amounts of mining
industry waste in the affected industry segments.
Source: Charles River Associates 1984 and 1985c.
3-28
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Surface water diversion ditches consist of canals, channels, or pipes that
totally or partially surround waste piles, tailings embankments, pits, or
ponds to divert the surface water around them and back into the natural stream
channel downgradient to the waste area. The most important functions of ditch
systems are to minimize downstream environmental damage, relieve dike stresses
to reduce the chance of failure, diminish erosion of the waste embankment, and
40 41
reduce the volume of water requiring environmental monitoring. ' Perimeter
ditches also help to recover supernatant for recycling, collect and drain dike
seepage, and collect onsite storm runoff for transport to a containment
treatment system. When wastewater requires treatment before release, a
suitable ditch network is constructed to prevent uncontaminated offsite or
onsite runoff from mixing with onsite wastewater streams.
Table 3-6 shows the extent for which mine waste piles studied by EPA have
run-on/runoff controls for storm water adequate to satisfy current RCRA
requirements. Run-on controls for mine waste that are adequate to satisfy
RCRA exist only at three mines studied by EPA in the gold industry sector.
Runoff controls exist at these same three mines and at one silver mine in
Colorado.
3.4.1.3 Liners
Lining the entire waste area and the upstream slope of the embankment may
prevent seepage. Liners can be formed from natural earthen (clay) materials,
synthetic materials, or a combination of these. Commercial bentonite can be
added to fine-textured soils to reduce their permeability to very low levels.
Synthetic liner materials include soil cements, treated bentonite, petroleum
derivatives, plastics, elastomers, and rubber. These liners are generally
more expensive than liners made of earthen materials, and careful earthwork is
3-29
-------
Table 3-6 Extent of Run-on/Runoff Controls for Stormwater
for Mine Waste, by Industry Segment
States requiring run-on/
Mining
industry
segment
Copper
Gold
Lead
Phosphate
Si 1 ver
Uranium
Zinc
No. mines
in data base
that generate
mine waste
13
11
7
18
9
9
7
No. mine
sites with
run-on
controls3
0
3 (21%}
0
0
0
0
0
No. mine
sites with
runoff
control s°
0
3 (27%)
0
1
1 (11%)
0
0
runoff
having mi
Run-ont
controls
Montana,
Cal i form'
controls or
ne sites with
Runoff*-
controls
Montana,
a California
N. Carolina
Col orado
a Sites are identified as having run-on controls only when these controls are adequate
to satisfy current RCRA requirements.
b Sites are identifed as having runoff controls only when these controls are adequate
to satisfy current RCRA requirements.
c These columns include only the states generating large amounts of mining industry
waste in the affected industry segments.
Source: Charles River Associates 1984 and 1985c.
3-30
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required to prepare the ground surface even when these synthetic materials are
used. If appropriate earthen liner materials are not readily available,
synthetic liners may be more economical. Liner materials must be resistant to
the potential corrosive effects of the waste and to damage from sunlight (if
the liner is not covered immediately after placement).
Although both synthetic and natural liners can be used cost-effectively in
relatively small disposal areas, they have not been used in the very large
waste facilities that are typical of mining industry waste sites (some of
which cover a square kilometer or more); and they may in fact not be feasible
43
at such sites. Experience is inadequate to evaluate the performance of
liners at large-area, large-volume sites. Lining large areas with synthetic
(membrane-type) liners would require many liners to be fastened together to
form a single large liner; each seam represents a point of potential failure.
If a liner underlying such a large waste area failed, it would be impossible
44
to repair.
Installing liners at existing disposal areas in this industry would
require moving billions of tons (approximately 50 billion tons) of material
that has been deposited over the years. Many active disposal sites have been
used for many years, and the areas are continually built up. Movement of
these materials to new lined sites severely affects the cost of operations at
these sites.
Table 3-7 shows the extent of the current use of tailings pond liners
adequate to satisfy current RCRA requirements, for mines studied by EPA. Mine
waste piles are not normally lined. According to Table 3-7, the majority of
tailings ponds at mine sites studied by EPA in the silver and zinc industry
segments are currently lined. Tailings ponds at mines studied by EPA in the
3-31
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Table 3-7 Extent of Tailings Pond Liner Use, by Industry Segment
Mining
industry
segment
Copper
Gold
Lead
Phosphate
Si 1 ver
Zinc
Number of
mines in
data base that
use tailings
pond liners
12
6
6
18
8
6
Number of
mine sites
having lined
tailings ponds3
0
1 (17%)
0
0
6 (75%)
4 (67%)
States requiring liners
or having mine sites with
lined tailings ponds** »c
Nevada
Idaho, Utah
Tennessee
a Sites are identified as having lined tailings ponds only when the liner
is adequate to satisfy current RCRA requirements.
k This column includes only those states where liner requirements are at
least as stringent as those required by RCRA.
c This column includes only the states generating large amounts of mining
industry waste in the affected industry segments.
Source: Charles River Associates 1984 and 1985c.
3-32
-------
copper, lead, and phosphate industry segments are not lined. One of the six
tailings ponds at mines studied by EPA in the gold industry segment is
currently lined.
Regulations promulgated in 40 CFR Part 192 required that new uranium mill
tailings impoundments be lined. Synthetic liners have been installed at three
uranium mill tailings impoundments and natural liners exist at other uranium
tailings impoundments.
Many mines studied by EPA have impermeable pads under heap leach piles.
Figure 3-3 shows an impermeable pad under a gold heap leach pile. These pads
aid in the collection of valuable leachate and reduce the pollution potential
at these sites.
3.4.1.4 Cutoff Walls
Seepage outflow can be minimized by placing impermeable blankets or zones
in the embankment or foundations, as illustrated in Figure 3-4A. A cutoff wall
of the type shown in Figure 3-4B can be used in cases where a relatively
impervious layer underlies a pervious layer at a shallow depth. The impervious
core below the embankment will cut off the flow through the shallow, pervious
portion of tine foundation. A cutoff wall is usually placed toward the upstream
portion of the embankment section to allow drained conditions under as much of
45
the embankment section as practicable. However, if total cutoff of
seepage is desired (illustrated in Figure 3-4C), the cutoff wall can be
installed far downstream, and the seepage can be removed from the drainage
trench, pumped back to the impoundment, and then returned to the mill, or it
can be pumped to a treatment plant and then released into a natural channel.
A small amount of seepage will percolate downward, even through nearly
impervious natural materials, from any unlined portion of the waste disposal
3-33
-------
T
~5m
_L
IMPERMEABLE PAD
(CLAY, ASPHALT, CONCRETE
OR PLASTIC SHEETING)
PREGNANT SOLUTION TANK
*. MAKE UP
t SOLUTION
(NaCN)
BARREN SOLUTION
GOLD RECOVERY
PROCESS
GOLD
Source: PEDCo Environmental, Inc. 1985
Figure 3-3 Impermeable pad under a gold heap leach pile
-------
IMPERMEABLE
ZONE
A. BLANKET AND CORE METHOD
CUTOFF WALL
B. FOUNDATION CUTOFF WALL METHOD
SAND AND GRAVELS
W BEDROCK
TO MILL OR
TREATMENT
PLANT
C. CUTOFF WALL AND OPEN TRENCH METHOD
Source: PEDCo Environmental, Inc. 1984
Figure 3-4 Some methods used to minimize seepage outflow
3-35
-------
area; additional monitoring wells may be required in such cases. When the
foundation consists of a thick pervious layer or several pervious layers
separated by strata or impervious materials, a drainage trench can be used to
remove some of the seepage.
3.4.1.5 Leachate Collection, Removal, and Treatment
During active site life, it is necessary to collect, remove, and treat
leachate from lined waste piles to prevent the leachate from building up above
the liner. Leachate collection prevents high moisture content at the base of
the pile from deforming the structure of the pile. For small lined areas of
facilities, an adequate leachate collection system may consist of a sump with
a pump to collect the waste and pipe it to a lined impoundment for treatment.
In larger facilities, a zone of sand, gravel, or coarse rock may be placed
below the waste and drained. Such a system may be augmented by perforated
pipe to increase capacity, and may also include collector trenches in cases in
which the system emerges onto a broad, level area. Collector trenches may be
useful even when no liners are used. Collected leachate must be treated and
disposed of by such treatment methods as neutralization and precipitation, as
discussed above.
At heap or dump leach operations, secondary leachate collection systems,
consisting of leachate collection sumps and ditches, serve to interrupt
liquids escaping the primary recirculating leaching system. The extent of
adequate secondary leachate collection and removal from heap/dump leach waste
and from tailings ponds is shown in Tables 3-8 and 3-9, respectively. Of the
gold mines studied by EPA, only one had a secondary leachate collection and
removal system in place that was adequate to satisfy current RCRA requirements
for such systems. Secondary collection and removal of leachate from tailings
3-36
-------
Table 3-8 Extent of Secondary Leachate Collection and Removal
from Heap/Dump Leach Waste, by Industry Segment
Mining
industry
segment
Copper
Gold
Si 1 ver
Number
of mines
in data base
that generate
heap/dump
leach waste
9
5
2
Number of
mine sites
that collect and
remove leachate
from heap /dump
leach waste3
0
1 (20%)
0
States requiring
secondary leachate
collection and removal or
having mine sites that
collect and remove leachate
from heap/dump leach waste" >c
New Mexico, Nevada
a Sites are identified as having secondary leachate collection and removal
systems only when the system is adequate to satisfy current RCRA requirements.
b This column includes only those states where leachate collection and
removal requirements are at least as stringent as those required by RCRA.
c This column includes only the states generating large amounts of mining
industry waste in the affected industry segments.
Source: Charles River Associates 1984 and 1985c.
3-37
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Table 3-9 Extent of Secondary Leachate Collection and Removal
from Tailings Ponds, by Industry Segment
Mining
industry
segment
Copper
Gold
Number
of mines in
data base
that generate
tailings
12
7
Number of mine
sites that collect
and remove
leachate from
tailings ponds3
0
2 (29%)
States requiring
secondary leachate
collection and removal or
having mine sites that
collect and remove leachate
from tailings pondsb»c
California, South Dakota,
Lead
Phosphate
Silver
Zinc
6
18
8
Nevada
0
0
2 (25%)
0
Montana, Colorado, Idaho,
Utah
a Sites are identified as having secondary leachate collection and removal
systems only when the system is adequate to satisfy current RCRA requirements.
b This column includes only those states where leachate collection and
removal requirements are at least as stringent as those required by RCRA.
c This column includes only the states generating large amounts of mining
industry waste in the affected industry segments.
Source: Charles River Associates 1984 and 1985c.
3-38
-------
ponds are practiced only at two gold mine sites studied by EPA, as shown in
Table 3-9.
3.4.1.6 Security Measures
During the active site life phase of operations, the mining industry
implements security measures that range from posting "No Trespassing" signs to
installing comprehensive systems of locked gates and fencing and using
security guards. Fencing material ranges from chain link to barbed wire. The
extent of the security measures employed depends on the severity of the
hazards existing at the mine site, the value of the material being mined or
milled, and the proximity of the mine site to populated areas. Posting
security guards has an additional benefit, because these employees can also be
assigned facility inspection duties, such as checking runoff dikes. At active
and inactive asbestos waste disposal sites, existing EPA regulations (40 CFR
Part 61) require security measures.
3.4.2 Mitigative Measures at Closure
The mitigative methods described above for the active site life phase
remain applicable during the closure phase. In addition, other activities may
be necessary or desirable. For example, tailings impoundments may be
dewatered and stabilized; these are essential steps if a cap and cover are to
be added. A cap and cover can be placed over the site to minimize contact of
the waste with the environment and to protect the waste from rainfall, which
increases the volume of leachate formed.
3.4.2.1 Wastewater Treatment
The wastewater that remains onsite after active mining and milling
operations have ceased may be treated and then discharged or be transported to
a licensed disposal site.
3-39
-------
3.4.2.2 Wastewater Pond Sediment Removal
The sediment that is collected in wastewater treatment and retention ponds
often contains settled solids created during the mining or milling processes,
precipitated metals, and process chemicals such as flotation reagents.
Assessment of the potential hazards must be made during the active life of the
mine and at closure, in order to properly dispose of and manage these wastes.
The quality of these sediments varies widely, and some sediments may require
removal at closure to reduce potential hazards, while other sediments may pose
little or no risk to humans or the environment.
3.4.2.3 Dike Stabilization
A major consideration in the closure of a waste disposal site or area is
the structural integrity of the dike(s) constructed to confine the
waste. ' Various methods of slope stabilization, such as slope
modification and/or placement of waste rock (rip-rap), topsoil, vegetation,
and chemical stabilizers, may be used during the active or final closure
phases of the life of the impoundment to minimize erosion and siltation.
Closure of a diked impoundment may require an assessment of the ability of the
dike system to withstand additional loads, which may include the weight of
several layers of a capping system (clay, drainage layer, and topsoil cover)
and of the construction equipment used to place and compact the final
49
cover. The long-term control of water behind the dike is a major factor
in the stability of dikes and prevention of catastrophic failure.
3.4.2.4 Waste Stabilization
Since wastes remain in place after closure of the waste piles and ponds,
proper consolidation and stabilization of the wastes are necessary to ensure
long-term support for the final cover when it is emplaced. The initial step
3-40
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in stabilizing tailings is dewatering the wastes. At some sites (e.g., copper
tailings ponds located in the arid Southwest), passive dewatering using
natural evaporation and drainage mechanisms may be sufficient to remove
free-standing water and to dewater the tailings. At other sites, active
dewatering using pumps to remove liquids within the impoundment or from ponds
on the impoundment surface may also be required in conjunction with passive
dewatering mechanisms. The liquids collected during dewatering operations may
require treatment before they are discharged or disposed of.
The wastes within the impoundment must also be capable of bearing the
loadings imposed by the final cover system and the construction equipment used
to apply this system. Tests can be used to estimate the anticipated amount of
waste settlement and any differential settling across the waste site likely to
50
be caused by increased loads. The results of these tests may indicate the
need for further dewatering, for redistribution of the wastes or compaction of
the material (e.g., mechanical compaction such as with a sheepfoot roller), or
for implementing methods of minimizing differential settlement.
3.4.2.5 Installation of Leachate Collection, Treatment, and Removal Systems
for Lined Surface Impoundments
In order for these systems to be effective in collecting leachate, the
post-closure needs of the system must be integrated into the initial design of
the impoundment.
3.4.2.6 Final Cover System
The proper installation of a final cover system over the exposed surfaces
of the waste impoundment, mine waste pile, leach dumps, etc., helps ensure
control of erosion, fugitive dust, and surface water infiltration; promotes
proper drainage; and creates an area that is aesthetically pleasing and
3-41
-------
amenable to alternative land uses. This cover system typically consists of
the following components:
• A low-permeability clay layer or synthetic membrane overlying the
waste material;
t A middle drainage layer of moderate to high permeability; and
t A top cover of topsoil and vegetation, except in the arid regions of
the Western United States, where a rock cover is more effective for
preventing erosion and breaching.51,52
The function of the low permeability material overlying the waste is to
prevent the infiltration of precipitation, minimize leachate generation, and
prevent the migration of potentially hazardous waste constituents from the
waste into the ground water. To prevent excessive leachate buildup, the
low permeability layer should be at least as impermeable as the liner, if
present.
If the final cover system is to be vegetated, a drainage layer of sand or
gravel having low hydraulic conductivity is laid over the impermeable cap.
This layer is graded (at least 2 percent) to allow the precipitation
infiltrating the vegetative cover to drain rapidly, thus minimizing the
hydraulic head on the clay cap or synthetic liner. Then, depending on the
gradation, this layer is overlaid by a filter to prevent clogging.
Except in arid regions, the top layer of the cover system consists of
topsoil capable of sustaining vegetation. Two feet of soil are considered
adequate to accommodate the root systems of most nonwoody vegetative covers
and to provide a degree of protection from root damage to the underlying
54
clay or synthetic liner. Wide variance in cl imatological factors and soil
conditions, and therefore in subsequent growing conditions, affects the level
of effort required to revegetate mined land successfully. For example, much
3-42
-------
less work is required at a Florida phosphate mine, where conditions are
favorable (fertile soils, adequate water, and long growing seasons) than at a
southwestern copper facility, where a combination of poor soils (e.g., high in
salts and sulfides, low in nutrients) and an arid climate may require managers
to introduce nonnative plant species, install irrigation systems, and provide
constant maintenance to develop and sustain the vegetative cover. Revegeta-
tion also requires extra effort at sites in mountainous terrain where erosion
rates are often high, growing seasons are short, and winters are long and
severe.
Tables 3-10 through 3-12 show the number of mine sites studied by EPA
where some types of closure activity are performed. Mines in many of the
industry segments stabilize their wastes, install some kind of cap, and
revegetate during the closure phase. For example, mine waste piles generated
by the gold industry in California are contoured for stability and
revegetated. For tailings generated by the phosphate industry in North
Carolina, reclamation consists of covering the tailings with sand to increase
stability, adding topsoil, and revegetating. Similarly, closure of tailings
piles at sites in the gold and silver industries in Montana consists of
compacting, grading, capping the tailings with rock and topsoil, and
revegetating. Although waste stabilization, capping, reclamation, and
revegetation appear to be common waste management practices in many industry
segments, installing a final cover, consisting of a low-permeability clay
layer or a synthetic membrane overlying the waste material, is not a
55
mitigative practice used in the mining industry. However, asbestos waste
piles must be covered daily, as required by EPA regulations in 40 CFR Part 61,
if there are visible emissions to the outside air.
3-43
-------
Table 3-10 Closure Activities for Mine Waste, by Industry Segment
Mining
industry
segment
Gold
Phosphate
Si 1 ver
Uranium
Number
of mines in
data base
that generate
mine waste
6
11
5
6
Number of mines
performing
some types of
closure
activity
2 (33%)
11 (100%)
4 (80%)
6 (100%)
States requiring some
types of closure activity
or having mine sites that
perform some types of
closure activity9
California, Colorado
Florida, Idaho
Idaho, Colorado, Utah
Colorado, Wyoming
a This column includes only the states generating large amounts of mining
industry waste in the affected industry segments.
Source: Charles Rivers Associates 1984 and 1985c.
3-44
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Table 3-11 Extent of Closure Activities for Heap/Dump
Leach Waste, by Industry Segment
Mi ni ng
industry
segment
Copper
Gold
Si 1 ver
Number
of mines
in data base
that generate
heap/dump
leach waste
8
5
1
Number
of mines
performing
some types of
closure
activity
1 (13%)
0
0
States requiring some
types of closure activity
or having mine sites that
perform some types of
closure activity*
Utah
a This column includes only the states generating large amounts of mining
industry waste in the affected industry segments.
Source: Charles River Associates 1984 and 1985c.
3-45
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Table 3-12 Closure Activities for Tailings Impoundments,
by Industry Segment
Mining
industry
segment
Copper
Gold
Lead
Phosphate
Si 1 ver
Zinc
Number
of mines
in data base
that generate
tailings
4
7
4
12
4
3
Number of mines
perf ormi ng
some types of
cl osure
activity
1 (25%)
3 (43*)
0
12 (100%)
4 (100%)
1 (33%)
States requiring some
types of closure activity
or having mine sites that
perform some types of
closure activity3
Utah, New Mexico
South Dakota, California,
Arizona, Montana, Nevada
Florida, Idaho,
North Carolina
Idaho, Colorado, Utah
Nevada, Montana
3 This column includes only the states generating large amounts of mining
industry waste in the affected industry sectors.
Source: Charles River Associates 1984 and 1985c.
3-46
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3.4.3 Mitigative Measures During Post-Closure
At certain sites during the post-closure phase, it is necessary to
continue to support the waste management methods applied during the active and
closure phases of site life. Many post-closure activities, such as
inspection, are routine during active site life but require special effort to
maintain once the site has been closed. For example, inspection activities
after site closure should be part of a program of regularly scheduled visits.
Inspection and detection activities during the post-closure period may
consist of the following:
• Assessment of the density, cover, and composition of vegetation
species to evaluate revegetation success;
• Visual or photographic inspection to detect rill and gully erosion;
• Analysis of data on ground-water quality to define contaminant
migration and dilution and to determine the effectiveness of liners,
cutoff walls, or other containment systems;
• Evaluation of data on ground-water level to define ground-water
recovery rates and levels;
• Visual or photographic inspection of stream and drainage channels to
determine migration rates and patterns;
• Monitoring of subsidence; and
• Visual and photographic inspection after severe meteorological
events (severe precipitation or drought) or other natural phenomena
(e.g., earthquakes). 56,57
Maintenance conducted during the post-closure period may consist of the
following:
• Reseeding areas that have not been successfully revegetated;
t Repairing or replacing security fences, gates, locks, and warning
signs;
• Maintaining collection and treatment systems;
• Maintaining monitoring wells and replacing them as necessary;
3-47
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t Replacing rip-rap to control the migration of stream and drainage
channels and the effects of flooding;
• Replacing top soil and rock covers to control rill and gully erosion;
and
• Eliminating trees and other deep-rooted vegetation that may damage
covers and liners.58*59
3.4.4 Corrective Action Measures
The corrective action measures described below may be necessary if a plume
of contaminated ground water above some threshold limits has been detected.
In this phase, the two major activities are additional hydrogeologic
evaluation and controlling the plume. These processes are described below.
Corrective action measures have not normally been performed at mining
facilities in the past.
3.4.4.1 Hydrogeol ogi cal Evaluation
Once ground-water contamination has been detected by the ground-water
monitoring system, an extensive hydrogeol ogi cal evaluation is usually needed
to determine the size, depth, and rate of flow of the contaminated plume. The
methods and limitations of hydrogeol ogi cal evaluations in the corrective
action stage are similar to those that apply to these evaluations during
active site life.
3.4.4.2 Interceptor Wells
Seepage losses through the deep pervious foundation of a waste disposal
facility can be reduced by installing interceptor wells at points that
intersect the plumes of contaminated seepage in the saturated zone.
Comprehensive hydrogeol ogi cal explorations and evaluations are required to
site these wells properly. The intercepted seepage may be pumped directly to
a mill or pond if water balances permit, or it may be treated before being
returned to the mill or discharged.
3-48
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3.4.4.3 Hydraulic Barriers
Interceptor wells may be used in combination with a hydraulic barrier
system established downgradient to the embankment, as shown in Figure 3-5. A
hydraulic barrier system is usually made by installing a line of pumping wells
downgradient to the leaking embankment, and a line of injection wells
downgradient to the pumping wells. The injection wells supply fresh water,
while the pumping wells extract ground water. Pump effluent is typically a
mixture of native ground water, plume water, and injected fresh water. The
use of hydraulic barriers is effective at sites where the subsurface is
generally homogeneous. The use of hydraulic barriers is not a common practice
in these segments, and their effectiveness must be demonstrated.
3.4.4.4 Grouting
If a waste presents a serious pollution hazard to ground water, grouting
the foundation rock may be warranted. The grouting process consists of
pumping a fluid grout mixture (usually a water-cement compound) through drill
holes into crevices and joints in rock to tighten the embankment foundation.
Chemical grout is used to seal porous materials and cracks that are too small
to accept a water-cement grout. Grouting must be thorough, because even a few
ungrouted joints in permeable rock formations can render the grouting effort
ineffective.
Figure 3-6 illustrates a grout curtain being used in conjunction with
extraction wells. This grouting process is often not very reliable, because
it is difficult to ensure a completely impermeable grout curtain. Generally,
grout curtains cannot be used to control deep vertical seepage within the
curtain's boundaries. In some cases, grout curtains can reach depths of
60 meters; however, both the cost and unreliability of these systems increase
fi?
rapidly at depths greater than 30 meters.
3-49
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LINE OF
PUMPING WELLS
LINE OF
INJECTION WELLS
• x
PERVIOUS FOUNDATION
PHREATIC SURFACE
Source: PEDCo Environmental, Inc. 1984
Figure 3-5 Hydraulic barrier for seepage collection
3-50
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EXTRACTION WELL
EXTRACTION WELL
ORIGINAL WATER TABLE
CONTAMINATED
ZONE
IMPERMEABLE LAYER (CLAY OR SHALE)
Source: PEDCo Environmental, Inc. 1984
Figure 3-6 Grout curtains and extraction wells for seepage control
3-51
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3.4.4.5 Cutoff Walls
Cutoff walls are often used as seepage or ground-water pollution control
systems because they are effective and relatively inexpensive. Sheet piling
cutoff walls can extend 24-30 meters in depth, but they have a relatively
short effective life (less than 20 years) and are difficult to construct to
achieve a low permeability barrier. More effective cutoff walls can be
constructed by digging narrow trenches to a depth of 9-15 meters and
backfilling them, either with a soil-ben ton ite or a soil-cement-ben ton ite
mixture that hardens into a homogeneous and very low-permeability barrier.
The effective use of cutoff walls is highly dependent on the site's
hydrogeologic properties, in that a naturally impermeable rock and/or soil
must underlie the waste within the cost-effective trenching depth. If an
impermeable layer does not exist, cutoff walls will be ineffective in stopping
migration of pollutants. This technology is not applicable to all mines, and
is not a common practice in this industry.
3.5 SUMMARY
Of the waste currently generated by the mining industry segments of
concern, 56 percent is disposed of on site, 9 percent is backfilled,
31 percent may be considered to be utilized on site (principally in the
leaching of copper dump wastes and in starter dams for tailings impoundments);
and 4 percent is utilized off site (as fill and aggregate for road
construction). Most tailings are disposed of in impoundments; but 5 percent
are backfilled, and 2 percent are used off site (in construction, as soil
supplements, etc.). Most mine water is recycled through the mill and used on
site for other purposes (e.g., dust control) or treated and discharged. Few
3-52
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methods are available to reduce the amount of solid waste generated by mining
and milling, but process modifications can reduce the water content and
potential toxicity of these wastes. Many methods are available to design,
site, maintain, and close disposal facilities in an environmentally acceptable
manner. Commonly used mitigative measures include ground-water monitoring at
leach operations only; and, for many types of operations, stabilization of
waste, installation of some kind of cap, and revegetation during the closure
phase. Available corrective action methods, not widely used in the mining
industry, include interceptor wells, underground barriers to prevent the
spread of contaminated ground water, and liners to contain the leachate.
3-53
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SECTION 3 FOOTNOTES
1 Tailings are often disposed of in ponds because, as described in
Section 2, they leave the mill as a slurry.
2 Greber et al. 1979.
3
Charles River Associates 1985a.
4 Vick 1981.
5
Goodson and Associates 1982.
6 Curtin 1983.
7 Seitter and Hunt 1982.
8 Seitter and Hunt 1982.
9 Seitter and Hunt 1982.
Charles River Associates 1985b.
11 Schiller 1983.
12 Heming 1984.
PEDCo Environmental, Inc. 1984.
14 USDA Forest Service 1979.
15
PEDCo Environmental, Inc. 1984.
16 Wixson et al. 1983.
17 Seitter and Hunt 1982.
18 A stope is an excavation from which ore has been mined in a series
of steps.
19 Vick 1981.
20 Vick 1981.
21
Goodson and Associates 1982.
22 Klohn 1981.
3-54
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SECTION 3 FOOTNOTES (Continued)
23 Portfors 1981.
24 Vick 1981.
25 US EPA 1982a.
26 Vick 1981.
27 EPA 1982a.
28 Vick 1981.
29
PEDCo Environmental, Inc. 1984.
Goodson and Associates 1982.
PEDCo Environmental, Inc. 1984.
32 TFI 1984.
U.S. Nuclear Regulatory Commission 1983.
34 BOM 1985.
Geological Society of America 1971.
oc
U.S. Nuclear Regulatory Commision 1983.
New Mexico Energy and Mining Department 1979.
38
New Mexico Energy and Mining Department 1979.
39 Pacific Northwest Laboratories 1983.
40 BOM1980b.
41 Lucia 1982.
42 Edwards et al. 1983.
43 DOE 1985.
44 DOE 1985.
45 BOM 1980.
U.S. Nuclear Regulatory Commission 1983.
3-55
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SECTION 3 FOOTNOTES (Continued)
47 Lucia 1982.
48 DOE 1985.
49
^ DOE 1985.
50 DOE 1985.
51 DOE 1985.
52
U.S. Nuclear Regulatory Commission 1983.
53 DOE 1985.
54 DOE 1985.
55
Charles River Associates 1984.
56
° DOE 1985.
57
U.S. Nuclear Regulatory Commission 1983.
CO
D DOE 1985.
59
U.S. Nuclear Regulatory Commission 1983.
60 BOM 1985.
61 BOM 19805.
62 Greber et al. 1979.
3-56
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SECTION 4
POTENTIAL DANGER TO HUMAN HEALTH AND THE ENVIRONMENT
This section assesses the potential danger to human health and the
environment associated with wastes generated by the mining industry. It
identifies the hazardous chemical and physical characteristics of these
wastes, estimates the amount and type of mining waste possessing these
characteristics, describes mining waste damage case studies compiled by
EPA, and discusses the effectiveness of mining waste management systems.
In this section, EPA is responding to the requirements of Sections 8002(f)
and (p) of RCRA for analyses of the "potential dangers to human health and the
environment from surface runoff of leachate," the "potential danger, if any,
to human health and the environment from the disposal and reuse" of mining
waste, and "documented cases in which danger to human health or the environ-
ment has been proved." Over a period of years, EPA has conducted these
analyses with the support of consulting firms and individual experts.
The studies sponsored by EPA involved waste sampling at 86 mines in 22
states; chemical analyses of solid and liquid samples (and leachates from
the solid samples); and monitoring of ground water at seven of eight
representative sites (and surface water of five of the sites).
Reports on mining industry damage cases were obtained from state files and
from information in EPA's files on sites on the National Priorities List for
Superfund cleanup. The damage case analysis focused on the range and severity
of contamination problems associated with mine and mill waste disposal at
active, inactive, abandoned, and Superfund sites.
4-1
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EPA is currently analyzing the amounts and rates of toxic releases from
mine and mill wastes. This is an essential prerequisite to studies on
exposures and effects, and is required for any quantification of risks to
human health and the environment posed by these wastes.
4.1 WASTE CHARACTERISTICS CONSIDERED
Mining wastes may contain constituents, such as heavy metals, other toxic
elements, radionuclides, cyanide compounds, and asbestos, that may be
dangerous to human health and the environment. In addition, some mine wastes
are corrosive (acidic) and others have a high potential for forming acid.
Table 4-1 presents the waste characteristics evaluated for this report,
the criteria used to determine whether or not mining wastes have these
characteristics, and the rationale for choosing these criteria. As the table
indicates, EPA evaluated two general categories of waste characteristics for
this report: RCRA Subtitle C Hazardous Waste Characteristics and Other
Potentially Hazardous Characteristics. The following sections discuss the
waste characteristics evaluated, the sampling methodology, and the sampling
results obtained by EPA at selected mine sites.
To evaluate the hazardous characteristics of mining waste for this report,
EPA's Office of Solid Waste (OSW) subdivided mining industry segments into the
following mining region-commodity categories:
• New Mexico Uranium;
• Wyoming Uranium;
t Other Uranium;
• Florida Phosphate;
• Idaho Phosphate;
t Other Phosphate;
4-2
-------
Table 4-1 Waste Characteristics, Hazard Criteria,
and Bases for Criteria Used to Assess the
Hazard Potential of Mining and Beneficiation Wastes
Waste
characteristic
Hazard
criterion
Basis for
criterion
t RCRA Subtitle C Hazardous Waste Characteristics
- Corrosivlty
- EP Toxicity
pH 42.0 or pH ^12.5
Metals in EP Extract:
Mercury >0
Cadmium >1
Selenium >1
Silver >5
Arseni c >5
Chromium >5
Lead >5
Barium ^100
2 mg/1
,0 mg/1
,0 mg/1
.0 mg/1
,0 mg/1
,0 mg/1
,0 mg/1
,0 mg/1
- IgnitabHity
(See definition used
in 40 CFR 261.21)
(See definition used
in 40 CFR 261.23)
- Reactivity
• Other Potentially Hazardous Characteristics
- Cyanide
Cyanide ^2 mg/1
^10 mg/1
^20 mg/1
Radioactivity
Asbestos
Acid formation
potential
Ra 226 ^5 pCi/gm
Ra 226 ^20 pC1/gm
Asbestos content >1% by wt.
Presence of metal
sulfides and absence
of carbonate minerals
40 CFR 261.22
40 CFR 261.24
(100 times
National Interim
Primary Drinking
Water Standards
for Metals)
40 CFR 261.21
40 CFR 261.23
(10, 50, and 100
times the Ambient
Water Quality
criterion for
protection of
human health,
respectively)
40 CFR Part 192
Derived from
40 CFR Part 192
40 CFR Part 61
Danger posed to
the environment
by acid drainage
Source: Compiled by EPA, OSW staff, 1985.
4-3
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• Southwestern Copper;
• Other Copper;
• Western Lead/Zinc;
• Eastern Lead/Zinc;
• Missouri Lead/Zinc;
• Molybdenum;
• Nevada Gold/Silver;
• Other Gold/Silver;
• Taconite/Iron; and
• Tungsten.
EPA sampled at least one mine and mill in each of these categories for
this study. EPA then augmented this sample set by taking samples from
operations (e.g., heap and dump leach operations) and industries (e.g.,
beryllium and rare earth metals) either not covered at all, or not
2
sufficiently covered in the first sample set. These results were then
supplemented with data from a study performed for EPA's Effluent Guidelines
Division (now the Industrial Technology Division) on the following mining
industry segments: antimony, bauxite (aluminum), mercury, nickel, titanium,
tungsten, and vanadium. EPA's Industrial Environmental Research Laboratory
performed the analyses of waste samples from mines in the asbestos mining
industry. Generally, EPA sampled the full range of waste types (e.g., fresh
tailings, mine water pond liquid and settled solids, tailings liquid and
settled solids, pregnant and spent leach liquor (process liquors that may be
characteristic of seepage from leach operations), and tailings dike material)
produced by mining and beneficiation operations in these segments. The Agency
also took additional samples of those wastes believed to be most likely to
present a hazard to human health and the environment (e.g., heap and dump
4-4
-------
leach wastes). For this reason, the percentage of samples having hazardous or
potentially hazardous characteristics is probably greater than would have been
the case if a completely random sampling strategy had been used. However, the
Agency excluded all results from samples that were believed to be either
invalid or duplicative.
EPA's Office of Solid Waste planned the original sampling and analysis
effort in 1979-1980 and, with the cooperation of the Office of Research and
Development, took samples between 1979 and 1984. To show the scope of EPA's
mining waste sampling and analysis effort, Table 4-2 presents 1980 figures for
the number of active mines, the number of mines sampled, and the percent of
mines sampled. Data are presented for 1980, because this was the year in
which the sampling effort was planned and initiated. This table shows that
EPA sampled 13 percent of all metal mines and 31 percent of all asbestos and
phosphate mines active in 1980. Figure 4-1 is a map showing the locations of
the mines EPA sampled.
4.1.1 RCRA Subtitle C Hazardous Waste Characteristics
Solid wastes are defined as hazardous under regulations implementing
Subtitle C of RCRA if they exhibit any of four general characteristics:
ignitability, corrosivity, reactivity, or EP toxicity. They are also
considered hazardous if they are listed as hazardous in 40 CFR 261.31-261.33.
Wastes may be listed under RCRA if the Administrator of EPA determines that
the wastes meet one of the criteria in 40 CFR 261.11. The Administrator must
indicate whether the wastes are ignitable, corrosive, reactive, EP toxic,
acutely hazardous, or toxic (40 CFR 261.30). Since Congress has, at least
temporarily, excluded mining wastes from regulation under Subtitle C of RCRA,
EPA's current lists of hazardous wastes do not include wastes from mining and
beneficiation processes.
4-5
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Table 4-2 Scope of EPA's Mine Waste Sampling
and Analysis Effort
Number of
Mining active mines
industry in sector,
segment 1 980a
Metals:
Antimony
Bauxite (Aluminum)*5
Beryl 1 i urn
Copper
Goldc
Iron
Lead
Mercury
Molybdenum
Nickel
Rare earth
metal s
Silver
Ti tani urn
Tungsten
1
2
1
39
44
35
33
4
11
1
2
43
5
29
Number of
active mines
sampl ed
1
1
1
13
6
5
4
1
3
1
1
6
2
1
Percent of
active mines
sampled
100
50
100
33
14
14
12
25
27
100
50
14
40
3
4-6
-------
Table 4-2 (continued)
Mining
industry
segment
Uranium
Vanadium
Zinc
Subtotal
Nonmetal s :
Asbestos
Phosphate
Subtotal
TOTAL
Number of
active mines
in sector,
19803
265
1
20
536
4
44
48
584
Number of
active mines
sampl ed
17
1
7
71
2
13
15
86
Percent of
active mines
sampl ed
6
100
35
13
50
30
31
15
a Estimated by Bureau of Mines 1981 (BOM 1982).
b Although the BOM lists 10 active mines, there were ony two
operations supplying bauxite for aluminum reduction. The other
mines are supplying bauxite for other uses.
c Excludes placer mines.
4-7
-------
00
Figure 4-1. Approximate locations of mining/benefication sites active in 1980 sampled by EPA for this report
-------
Mining wastes are far more likely to be corrosive or EP toxic than
ignitable or reactive. Therefore, EPA did not evaluate ignitability, which
measures the ability of wastes to cause or exacerbate fires, or reactivity,
which measures explosivity and the ability of sulfide- or cyanide-containing
wastes to generate toxic gases, vapors, or fumes, although some mining wastes
containing cyanide or sulfide may be reactive. However, the toxic properties
of cyanide-containing mining wastes were examined separately in this report.
The RCRA Subtitle C characteristics of corrosivity and EP toxicity are
discussed below as they relate to mining and beneficiation wastes. In
addition, copper dump leach, which may be a potential candidate for listing
under 40 CFR 261.31 because of its potential EP toxicity and corrosivity, also
is described.
4.1.1.1 Corrosivity
A waste is considered corrosive and therefore hazardous if it is a liquid
and has a pH less than or equal to 2 or greater than or equal to 12.5, as
A
determined by a pH meter. EPA chose pH as a "barometer of corrosivity,
because wastes exhibiting low or high pH can cause harm to human tissue,
promote the migration of toxic contaminants from other wastes, and harm
aquatic life" (45 FR 33109, May 19, 1980). The lower pH limit of 2.0 was
chosen so that "a number of substances generally thought to be innocuous and
many industrial wastewaters prior to neutralization" would not fall within the
corrosive classification. The upper pH limit of 12.5 was chosen to exclude
lime-stabilized wastes and sludges from corrosive classification (45 FR 33109,
May 19, 1980). For this study, EPA also evaluated whether samples had a high
pH (greater than 10 but less than 12.5) or low pH (greater than 2 but less
than 4), to aid in deciding which wastes could be potential candidates
4-9
-------
for listing and which might cause damage to human health and the environment.
These pH levels, and associated contamination by toxic metals, can degrade
aquatic ecosystems.
Table 4-3 shows the results of the corrosivity analyses performed by EPA
for this report. Of the 159 liquid waste samples taken by EPA, only 5 were
corrosive. An additional 28 samples had low (more than 2 and less than 4) or
high (more than 10 and less than 12.5) pH's. Some of the liquid samples, such
as pregnant leach liquors or wastewater prior to treatment and discharge, are
considered by industry to be process streams. The characteristics of some of
these liquids would be likely to alter (improve) after the active life of the
mine.
Table 4-4 identifies all of the industry segments that had at least one
sample with a low or high pH. All copper dump leach operations had at least
one sample with a pH less than or equal to 4 and 11 of the 23 liquid samples
with pH's less than or equal to 4 were from the copper industry segment. Of
the nine waste management operations having samples with pH's greater than 10,
more than half were from tailings processed with caustic solutions. However,
tailings such as these may later be treated to lower their pH, which reduces
their hazard potential.
4.1.1.2 EP Toxicity
A solid waste is defined as EP toxic (and thus hazardous) if, using the
test methods described in 40 CFR Part 261 (Appendix II), an extract from a
5
representative sample of waste contains certain metals at a concentration
greater than or equal to 100 times the maximum contaminant levels for these
metals as established by EPA's National Interim Primary Drinking Water
4-10
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Table 4-3 Results of Corrosivity3 Analyses of Liquid Mining Waste Samples
Number of samples with pH:
Mining
industry
segment
Metals:
Copper
Gold
Iron
Lead
Molybdenum
Silver
Uranium
Zi nc
Other metals5
Subtotal
Nonmetal s :
Asbestos
Phosphate
Subtotal
TOTAL
Number of
sampl es
analyzed
29
5
7
6
9
6
19
15
47
143
2
14
16
159
Less than or
equal to 2a
3 (10%)c
0
0
0
0
0
0
0
1 (2%)
4 (3%)
0
0
0
4 (3%)
Between
2 and 43
8 (29%)
0
0
0
1 (11%)
0
0
0
10 (21%)
19 (13%)
0
0
0
19 (12%)
Between
10 and 12.53
3 (10%)
1 (20%)
0
0
0
1 (17%)
0
0
4 (2%)
9 (6%)
0
0
0
9 (6%)
Greater than or
equal to 12. 5a
0
0
0
0
0
0
0
0
1 (2%)
1 (1%)
0
0
0
1 (1%)
Number of
samples
corrosive3
3 (10%)
0
0
0
0
0
2 (4%)
5 (3%)
0
0
0
5 (3%)
3 A waste is corrosive under current RCRA Subtitle C regulations if the pH is less than or equal to 2 or greater
than or equal to 12.5
D Includes antimony, bauxite, beryllium, mercury, nickel, rare earth metals, titanium, tungsten, and vanadium.
c Numbers in parentheses are percentages of all samples analyzed for that industry segment that have the
hazardous characteristic.
Source: PEDCo Environmental, Inc. 1984, ERCO 1984, and Harty and Terlecky 1982.
-------
Table 4-4 Number of Mines, Wastes, and Operations with Samples Showing Low or High pH Levels
Number of waste management operations with at least one sample:
Mining
industry
segment
Copper
Gold
Molybdenum
Silver
Other metalsd
Type of
waste
management
operation
No. mines involved''
Mine waste0
Dump leach
Tailings
No. mines involved
Mine waste
Heap leach
Tailings
No. mines involved
Mine waste
Tailings
No. mines involved
Mine waste
Heap leach
Tailings
No. mines involved
Mine waste
Dump/heap leach
Tailings
Number
of waste
management
operations
analyzed
13
7
6
12
5
1
2
2
3
2
3
5
0
0
5
10
5
1
7
Having pH
less than
or equal
to 2
3
0
3
0
0
0
0
0
0
0
0
0
0
0
0
1
0
0
1
Having pH
between
2 and 4
5
3
3
1
0
0
0
0
1
1
0
0
0
0
0
4
2
0
2
Having pH
between
10 and 12.5
1
0
0
2
1
0
1
1
0
0
0
1
0
0
1
3
0
1
2
Having pH
greater than
or equal
to 12.5
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
1
0
0
1
Number
of opera-
tions with
corrosive
waste3
3
0
3
0
0
0
0
0
0
0
0
0
0
0
0
2
0
0
2
-------
Table 4-4 (continued)
f1
Number of waste management operations with at least one sample:
Mining
industry
segment
Total
(All segments)
Type of
waste
management
operation
No. mines involved
Mine waste
Dump/Heap leach
Tailings
Number
of waste
management
operations
analyzed
78
43
10
52
Having pH
less than
or equal
to 2
4
0
3
1
Having pH
between
2 and 4
10
6
3
3
Having pH
between
10 and 12.5
8
0
1
7
Having pH
greater than
or equal
to 12.5
1
0
0
1
Number
of opera-
tions with
corrosive
waste3
5
0
3
2
a A waste is corrosive only if its pH is less than or equal to 2 or greater than or equal to 12.5.
b The number of mines involved may be less than the sum of sampled operations if one mine has more than one operation;
for example, the same mine site might have both mine waste and one or more leach operations.
c Mine waste includes mine water.
d Includes antimony, bauxite, beryllium, mercury, nickel, rare earth metals, titanium, tungsten, and vanadium.
Source: PEDCo Environmental, Inc. 1984, ERCO 1984, and Harty and Terlecky 1982.
-------
Standards (NIPDWS) (40 CFR Part 141). EP toxic levels are:
• Mercury (Hg) >0.2 mg/1;
• Cadmium (Cd) or selenium (Se) si.0 mg/1;
• Silver (Ag), arsenic (As), total chromium (Cr),
or lead (Pb) 2=5.0 mg/1; and,
• Barium (Ba) ^100 mg/1.
EPA designed the EP toxicity test to simulate the leaching of hazardous
constituents from a sanitary landfill into ground water. It approximates the
conditions prevalent within a landfill where weak organic acids may come in
contact with toxic metals. In recognition of the fact that contaminant
concentration levels would decrease between the point at which the leachate
migrates from the waste and the point of human or environmental exposure, EPA
set EP toxicity levels for contaminants in leachate at 100 times the levels
acceptable in drinking water. An attenuation factor of 100 was used rather
than a lower level (e.g., 10 times the drinking water limit) because of the
lack of empirical data on which to base an attenuation factor, the absence of
a variance procedure (i.e., delisting) for wastes that fail the EP test, and
because "EPA believes the...[extraction procedure] to be a somewhat less
precise instrument than the listing mechanism for determining hazard, inasmuch
as the EP fails to take into account factors such as the concentration of
toxicants in the waste itself and the quantity of waste generated which would
have a bearing on the hazardousness of the waste" (45 FR 33111, May 19, 1980).
EPA preferred therefore to "entrust determinations of marginal hazard to the
listing mechanism rather than to the EP" (45 FR 33111, May 19, 1980). In
4-14
-------
adopting the 100-fold attenuation factor, the Agency explained that "anything
which fails the EP at this factor has the potential to present a substantial
hazard regardless of the attenuation mechanisms at play" (45 FR 33111, May 19,
1980).
The metals measured by RCRA's EP toxicity test can, however, cause some
types of environmental damage at levels much lower than those that fail RCRA's
EP toxicity test or even EPA's National Interim Primary Drinking Water
Standards, especially if these metals are contained in wastes that contaminate
surface water rather than ground water. Accordingly, the 24-hour average
level of EP metals set by EPA's Ambient Water Quality Criteria for the
Protection of Aquatic Life are, in all cases, lower than those permitted by
EPA's drinking water standards, and therefore are much lower than the levels
allowed by RCRA's EP toxicity test. This does not mean that all mining wastes
meeting the EP toxicity test pose a threat to aquatic life, because the EP
leaching procedure was designed to evaluate the potential of a given waste for
unacceptable degradation of ground water and assumed that the wastes would be
disposed of above an aquifer supplying drinking water (a conservative
assumption). Table C-l in Appendix C of this report provides a comparison of
EP toxicity levels, drinking water levels, and ambient water quality levels
for the metals measured by the EP toxicity test. Research findings on the
levels of metals measured by the EP toxicity test (i.e., arsenic, cadmium,
chromium, lead, mercury, and selenium) that are toxic to aquatic biota are
summarized in Tables C-2 to C-7 of Appendix C.
EPA's sampling results indicate that a small percentage of the mining
waste samples were EP toxic. Of the 332 samples from the metals mining
4-15
-------
industry segments, 21 (6 percent) exhibited the characteristic of EP
toxicity. These 21 samples were from the copper, gold, lead, silver, zinc,
and other metals industry segments. An additional 39 samples had elevated
levels (i.e., between 20 and 100 times the levels permitted by the drinking
water standards) of the metals measured by the EP toxicity test; these
additional samples came from these same industry segments and from the uranium
and phosphate mining segments. These results are summarized in Table 4-5.
Tables 4-6 and 4-7 differentiate EP toxicity test results for solid
samples and liquid samples, respectively. Twenty of the 21 EP toxic samples
were solid samples and 31 of the 39 samples with elevated levels (i.e.,
between 20 and 100 times the levels permitted in the drinking water standards)
of the metals measured by the EP toxicity test were solid samples. One liquid
sample was EP toxic, and it was from the copper industry segment.
Table 4-8 identifies all industry segments that had at least one EP toxic
sample or one sample with an elevated level of one of the metals measured by
the EP toxicity test. Samples from 86 mines were tested for EP toxicity. At
least one sample from 10 of these mines was EP toxic, and 29 mines had at
least one sample with an elevated level (i.e. greater than 20 times the
NIPDWS) of an EP toxic metal. A particularly high percentage of samples from
gold heap leach and tailings, lead mine waste and tailings, zinc tailings, and
copper dump leach operations had EP toxic or elevated levels of one of the
metals measured by the EP toxicity test. Four of the eight copper dump leach
operations, three of the seven zinc tailings operations, four of the six gold
tailings operations, two of the three gold heap leach operations, and five of
the six lead operations had at least one sample with a level of one of the
metals measured by the EP toxicity test greater than or equal to 20 times the
NIPDWS.
4-16
-------
Table 4-5 Results of EP Toxicity Analyses for All Samples
Mining
industry
segment
Metals:
Copper
Gold
Iron
Lead
Molybdenum
Si 1 ver
Uranium
Zinc
Other metal sb
Subtotal
Nonmetal s :
Asbestos
Phosphate
Subtotal
TOTAL
Number of
samples
analyzed
83
26
31
15
15
25
67
25
45
332
7
70
77
409
Number of samples
with at least one
EP toxic metal at
level between
20 and 100X
the NIPDWSa
4 (5%)
7 (27%)
0
4 (27%)
0
3 (12%)
5 (7%)
5 (20%)
8 (18%)
36 (11%)
0
3 (4%)
3
39 (10%)
Number of
samples
EP toxic9
1 (1%)
3 (12%)
0
6 (40%)
0
4 (16%)
0
4 (16%)
3 (7%)
21 (6%)
0
0
0
21 (5%)
a Numbers in parentheses are percentages of all samples analyzed for that
industry segment that had the hazardous characteristic.
D Includes antimony, bauxite, beryllium, mercury, nickel, rare earth metals,
titanium, tungsten, and vanadium.
Source: PEDCo Environmental, Inc. 1984, ERCO 1984, and Harty and Terlecky
1982.
4-17
-------
Table 4-6 Results of EP Toxicity Analyses for Solid Samples
Mining
industry
segment
Metals:
Copper
Gold
Iron
Lead
Molybdenum
Si 1 ver
Uranium
Zinc
Other metal sb
Number of
sampl es
analyzed
72
22
30
14
14
22
63
22
39
Number of samples
with at least one
EP toxic metal at
level between
20 and 100X
the NIPDWS3
1 (IX)
4 (18%)
0
4 (29%)
0
3 (14%)
5 (8%)
5 (23%)
6 (15%)
Number of
samples
EP toxic3
0
3 (14%)
0
6 (43%)
0
4 (18%)
0
4 (18%)
3 (8%)
Subtotal
Nonmetal s;
Asbestos
Phosphate
Subtotal
TOTAL
298
5
68
73
371
28 (9%)
0
3 (4%)
3 (4%)
31 (8%)
20 (7%)
0
0
0
20 (5%)
a Numbers in parentheses are percentages of all samples analyzed for that
industry segment that had the hazardous characteristic.
b Includes antimony, bauxite, beryllium, mercury, nickel, rare earth metals,
titanium, tungsten, and vanadium.
Source: PEDCo Environmental, Inc. 1984, ERCO 1984, and Harty and Terlecky
1982.
4-18
-------
Table 4-7 Results of EP Toxlcity Analyses for Liquid Samples
Mining
industry
segment
Number of
sampl es
analyzed
Number of samples
with at least one
EP toxic metal at
level between
20 and 100X
the NIPDWS3
Number of
sampl es
EP toxic3
Metals:
Copper
Gold
Iron
Lead
Molybdenum
Silver
Uranium
Zinc
Other metals3
Subtotal
Nonmetals:
Asbestos
Phosphate
Subtotal
TOTAL
11
4
1
1
1
3
4
3
6
34
2
2
4
38
(27%)
(75%)
(33%)
8 (24%)
0
0
0
8 (21%)
1 (9%)
0
0
0
0
0
0
0
0
1 (3%)
0
0
0
1 (3%)
a Numbers in parentheses are percentages of all samples analyzed for that
industry segment that had the hazardous characteristic.
b Includes antimony, bauxite, beryllium, mercury, nickel, rare earth metals,
titanium, tungsten, and vanadium.
Source: ERCO 1984 and Harty and Terlecky 1982.
4-19
-------
Table 4-8 Number of Mines and Waste Management Operations with EP Toxic Samples or Samples
Having Elevated Levels of Metals, as Measured by the EP Toxicity Test
i
INi
O
Mining
industry
segment
Copper
Gold
Lead
Phosphate
Si 1 ver
Type of
waste
management
operation
No. mines involved
Mine waste
Dump leach
Tailings
No. mines involved
Mine waste
Heap leach
Tailings
No. mines involved
Mine waste
Tai 1 i ngs
No. mines involved
Mine waste
Tailings
No. mines involved
Mine waste
Heap leach
Tailings
Number of
operations
analyzed
13
11
8
13
6
6
3
6
4
2
4
13
13
10
6
4
0
6
Number of
operations
with at least
one EP toxic
sample
(100X NIPDWS)
1
0
1
0
2
1
0
2
3
1
2
0
0
0
1
1
0
1
Number of
operations
with at least
one sample
between 20 and
100X NIPDWS3
3
0
3
0
5
0
2
3
2
1
2
3
1
2
2
1
0
1
Number of
operations
with at least
one sample
greater than 2 OX
the NIPDWS&
4
0
4
0
5
1
2
4
3
2
3
3
1
2
2
1
0
2
-------
Table 4-8 (continued)
Mining
industry
segment
Uranium
Zinc
Other Metalsc
TOTAL
(All segments)
Type of
waste
management
operation
No. mines involved
Mine waste
Tai 1 i ngs
No. mines involved
Mine waste
Tailings
No. mines involved
Mine waste
Tailings
No. mines involved
Mine waste
Dump/Heap leach
Tailings
Number of
operations
analyzed
17
17
NA
7
5
7
10
7
9
86
75
11
65
Number of
operations
with at least
one EP toxic
sample
(100X NIPDWS)
0
0
NA
2
0
2
1
1
1
10
4
1
8
Number of
operations
with at least
one sample
between 20 and
100X NIPDWSa
5
5
NA
3
1
3
5
2
3
28
11
5
14
Number of
operations
with at least
one sample
greater than 20X
the NIPDWSb
5
5
NA
3
1
3
5
2
4
29
13
6
18
NA indicates not applicable to this report.
a Samples were not EP toxic but had elevated levels of EP toxic metals.
b Samples were EP toxic or had elevated levels of EP toxic metals; results in this
column may not equal the sum of results in the previous two columns because samples were often tested for
more than one EP toxic metal.
c Includes antimony, bauxite, beryllium, mercury, nickel, rare earth metals, titanium, tungsten and
vanadium.
Source: PEDCo Environmental, Inc. 1984, ERCO 1984, and Harty and Terlecky 1982.
-------
Table 4-9 shows the number and percentage of EP toxic samples and the
number of samples having elevated levels of the metals measured by the EP
toxicity test, by type of metal. Nineteen of the 21 samples failing the
standard EP toxicity test failed because they had EP toxic levels of lead; in
addition, 15 of the 39 samples with elevated levels of metals measured by the
EP toxicity test had elevated levels of lead.
For purposes of comparison with these EP toxicity test results, most mine
waste samples, most settled solid samples, and some low-grade ore samples were
subjected to a modified EP toxicity test in which deionized water, rather than
acetic acid, was used as the extracting medium. None of the 214 samples
subjected to this test produced leachates containing metal concentrations at
the EP toxic level, including the samples from the lead industry. These
modified EP test results show that in at least some mining waste situations,
lead and other toxic metal constituents may not be mobilized. Actual leachate
samples were usually not obtained, and therefore actual leachate
concentrations are unknown.
Since sulfuric acid simulates the situation in which waste leaches into an
acidic environment more closely than does acetic acid, sulfuric acid might be
an appropriate test leaching medium for modeling such an environment. For
example, when lead combines with sulfuric acid, the lead sulfate that is
formed precipitates out of the solution, which renders the lead less soluble
than it would be if it were combined with acetic acid. The results from EPA's
modified EP toxicity test using deionized water, and information on the fate
of some waste constituents in acidic environments, suggest that additional
toxicity tests may be necessary to simulate the potential hazard posed by some
mining wastes in some environments.
4-22
-------
Table 4-9 Number and Percentage of EP Toxic Samples and Samples Having
Elevated Levels of Metals Measured by the
EP Toxicity Test, by Type of Metal
IN3
GO
EP toxic
metal s
Arsenic
Barium
Cadmium
Chromi urn
Lead
Mercury
Silver
Sel eni urn
Number of
samples
EP toxic
(100X NIPDWS)3
1
0
1
0
19
1
0
0
Percentage of
all EP toxic
sampl esa
5
0
5
0
86
5
0
0
Number of
samples with
elevated levels of
EP toxic metals
(greater than 20
and less than 100X
NIPDWS)b
3
2
6
3
15
8
0
6
Percentage of
al 1 sampl es
with elevated
levels of metals
(greater than 20
and less than 100X
NIPDWS)b
8
5
15
8
38
21
0
15
a Twenty-one samples were EP toxic. However, one of these samples had EP toxic levels of two of the metals
measured by the EP toxicity test.
b Thirty-nine samples contained metals measured by the EP toxicity test at levels between 20 and 100 times
the NIPDWS. Many of these samples contained these levels for more than one of the metals.
Source: PEDCo Environmental Inc. 1984, ERCO 1984, Harty and Terlecky 1982.
-------
4.1.1.3 EP Toxicity and Corrosivity (Copper Disnp Leach Liquor)
In the case of dump leach liquor from copper dump leach operations, EPA
believes that the results of the sampling and analyses performed on these
samples and presented in Table 4-10 indicate that this waste may be a
potential candidate for listing because of its acidity and relatively high
concentrations of toxic metals. Partial results for samples of this waste
were presented in Tables 4-3 and 4-4 (Results of Corrosivity Analyses) and
Tables 4-5, 4-7, and 4-8 (Results of EP Toxicity Tests).
As shown in Table 4-10, the sample from leach operation no. 1 was EP
toxic, with an arsenic level of 7.8 mg/1 (156 times the NIPDWS) and a cadmium
level of 1.8 mg/1 (180 times the NIPDWS). Samples from all three leach
operations had arsenic and cadmium levels at least 50 times their respective
NIPDWS limits. Samples from two of the three operations had levels of
chromium and selenium greater than 20 times the NIPDWS. Two of the three
copper dump leach samples were corrosive, with pH's of less than 2, and the
sample from the third site had a very low pH (2.49).
4.1.2 Other Characteristics
The other criteria used in this report to assess the potential hazard of
mining waste include properties such as radioactivity and acid formation
potential , and the presence at certain levels of hazardous constituents such
as cyanide or asbestos. These constituents and properties are considered to
be potentially hazardous because they are believed to pose a threat to human
health and the environment if they are present in waste, including mining
waste, at the levels specified below.
4.1.2.1 Cyanide
For the purpose of this report, EPA assessed liquid mining waste samples
in relation to various cyanide levels: greater than or equal to 2 mg/1,
4-24
-------
Table 4-10 Results of Corrosivity and EP Toxicity Analyses
of Copper Dump Leach Liquor Samples
Tested
characteristic
Sample from
leach
operation
no. 1 (mg/1 )
Sample from
leach
operation
no. 2 (mg/1 )
Sample from
leach
operation
no. 3 (mg/1 )
PH
Arsenic
mg/1
Bari urn
mg/1
Cadmi urn
mg/1
Chromium
mg/1
Lead
mg/1
Mercury
mg/1
Seleni urn
mg/1
Si 1ver
mg/1
1.82
1.8
(180 X NIPDWS)
3.4
(68 X NIPDWS)
0.57
(57 X NIPDWS)
1.95
7.8 3.5
(156 X NIPDWSa) (70 X NIPDWS)
0.82
(82 X NIPDWS)
1.2
(24 X NIPDWS)
0.35
(35 X NIPDWS)
2.49
2.5
(50 X NIPDWS)
0.55
(55 X NIPDWS)
0.81
(16 X NIPDWS)
0.13
(3 X NIPDWS)
National Interim Primary Drinking Water Standards.
bDash (--) indicates level of this metal was less than the NIPDWS limit.
Source: ERCO 1984.
4-25
-------
greater than or equal to 10 mg/1, and greater than or equal to 20 mg/1. These
levels are 10, 50, and 100 times, respectively, the ambient water quality
(AWQ) criterion for cyanide for the protection of human health (assuming daily
ingestion of 2 liters of contaminated drinking water and 6.5 grams of tissue
from organisms living in the same contaminated water). In the cost analysis
section of this report, EPA used a cyanide level of greater than or equal to
10 mg/1 to define the threshold of hazard. (No samples from the iron,
uranium, other metals, asbestos, or phosphate industry segments were analyzed
for cyanide, because cyanide is not introduced into mining and beneficiation
processes in these industries.)
Because of the difficulty of analyzing waste samples for cyanide, EPA had
several laboratories test several of the cyanide samples. Table 4-11 shows
the results of cyanide analyses of liquid waste samples. Of 27 liquid samples
analyzed for cyanide, 8 samples (30 percent) had at least one test result
showing cyanide concentrations greater than or equal to 2.0 mg/1: seven of
the samples were from the gold industry segment, and one sample was from the
copper segment.
All of the cyanide sample test results for which at least one test showed
a cyanide level greater than or equal to 2.0 mg/1 are presented in
Table 4-12. As shown on this table, the copper tailings pond sample had a
cyanide level between 2 and 10 mg/1, and three of the five gold tailings pond
samples had a cyanide level of at least 10 mg/1 (and one of these three gold
tailings samples had a cyanide level of at least 20 mg/1). Both samples from
gold heap leach operations had cyanide levels greater than 10 mg/1.
EPA believes that wastes from gold and silver metal recovery and heap
leach operations may be potential candidates for listing, because of their
tendency to contain high levels of cyanide. Although EPA did not take any
4-26
-------
Table 4-11 Results of Cyanide Analyses of Liquid Waste Samples
Number of samples
with at least one
test result
Mining Number of showing CN greater
industry samples than 2 mg/la
segment analyzed (10X AWQ)
Metals:
Copper 13 1 (8)
Gold 7 7 (100)
Lead 3 0
Molybdenum 3 0
Zinc l_ 0_
TOTAL 27 8 (30)
a Numbers in parentheses are percentage of samples taken in that
industry segment having the potentially hazardous characteristic.
Source: Personal Communication from PEDCo Environmental, Inc. 1984; ERCO
1984.
4-27
-------
Table 4-12 Summary of Cyanide Sampling Results for Liquid Samples with at
Least One Test Result Greater than 2 mg/1
Type of mine,
operation,
and sample
identification
Number
of tests
Number
of tests
with CN values
less than
2 mg/1
Number
of tests
with CN values
between 2
and 10 mg/1
Number
of tests
with CN values
between 10
and 20 mg/1
Number of tests
with CN values
greater than
or equal to
20 mg/1
ro
c»
Copper mine
Tailings pond
Sample A
Gold mine 1
Tailings pond
Sample A
Sample B
Gold mine 2
Tailings pond
Sample A
Sample B
Gold mine 3
Tailings pond
Sample A
Gold mine 4
Barren leach pond
Sample A
Gold mine 5
Pregnant heap leach
Sample A
3
4
4
5
1
5
Source: Personal communication from PEDCo Environmental, Inc. 1984; ERCO 1984.
-------
samples of silver heap leach operations specifically, the similarity of gold
and silver heap leach operations makes it likely that silver heap leach wastes
also have high levels of cyanide. With few exceptions, gold and silver values
that are leached are extracted from finely crushed ores, concentrates,
tailings, and low-grade mine rock by dilute and weakly alkaline solutions of
potassium cyanide or sodium cyanide.
In analyses performed to support the promulgation of effluent limitations
guidelines and standards for the ore mining and dressing point source category
(i.e., metals mining and beneficiation), EPA's Effluent Guidelines Division
(now the Industrial Technology Division) found that 2 of 68 mill wastewater
samples tested for cyanide from the copper/lead/zinc/gold/silver/platinum/
molybdenum industrial subcategory had cyanide levels greater than 2 mg/1 but
less than 10 mg/1. But these were influent samples (to treatment) and
would be treated prior to discharge. The highest discharge level, even
without adequate treatment, was 0.4 mg of total cyanide per liter. Free
cyanide was not measured.
Cyanide is an environmental hazard at levels significantly lower than
2 mg/1 (EPA's Cyanide Ambient Water Quality Criteria for the protection of
human health). The 24-hour average level of cyanide allowed by EPA's Ambient
Water Quality Criteria for the protection of freshwater aquatic life is 0.0035
mg/1, with the concentration not to exceed 0.052 mg/1 at any time (45 FR
79331; November 20, 1980). Table C-8 in Appendix C summarizes research
findings on the toxicity of cyanide to aquatic biota.
4.1.2.2 Radioactivity
Naturally occurring radionuclides in mining waste and ore may pose a
radiation hazard to human health if the waste is used in construction or land
4-29
-------
reclamation or if concentrations of radionuclides (e.g., radium-226) are high
enough to produce significant concentrations of hazardous decay products
(e.g., radon-222).
Two criteria have been used in this report to assess potentially hazardous
levels of radioactivity in mining waste. These criteria are both based on
EPA's Standards for Protection Against Uranium Mill Tailings (40 CFR Part
192). These regulations contain a "cleanup" standard for uranium mill
tailings that is set at a limit of 5 pCi of radium-226 per gram for the first
15 centimeters of soil below the surface. (The 5 pCi/g radioactivity
criterion was also chosen by EPA in an Advance Notice of Proposed Rulemaking
published in 1978 (43 FR 59022) that solicited comments on expanding the list
of RCRA hazardous waste characteristics to include a "radioactivity
charcteristic".) The second radioactivity criterion used in this report, 20
pCi or more of radium-226, is based on the "disposal design" portion of the
same standard, which requires that the average release rate of radon-222 not
exceed 20 pCi per square meter per second. In this report, EPA made the
conservative assumption that each picocurie of radium-226 per gram of waste
produces an average release rate of 1 pCi of radon-222 per square meter per
second. As a result, a radioactivity criterion of 20 pCi or more of
radium-226 per gram of waste can be assumed to include all wastes that would
fail to meet the radon-222 criterion set forth in 40 CFR Part 192.
EPA analyzed selected mining wastes to determine their radium-226
concentrations. Of 187 solid waste samples, 69 (37 percent) had radium-226
concentrations greater than or equal to 5 pCi/g. These samples were from the
uranium, "other" metals, and phosphate mining segments. Of the same 187
samples, 34 (18 percent) had radium-226 concentrations greater than or equal
4-30
-------
to 20 pCi/g; these samples were also from the uranium, other metals group, and
phosphate mining industry segments. Results of the radium-226 analyses are
presented in Table 4-13. (Asbestos samples were not tested for radioactivity,
because EPA believed that wastes from this industry segment were unlikely to
be radioactive.)
The number of mines and waste management operations having radioactive
samples is presented in Table 4-14. All 17 uranium mines sampled by EPA had
at least one mine waste sample with a level of radium-226 greater than or
equal to 5 pCi/g. Fourteen of the 17 mines had at least one mine waste sample
of radium-226 greater than or equal to 20 pCi/g. Ten of the 13 phosphate
mines sampled by EPA had at least one sample with a level of radium-226
greater than or equal to 5 pCi/g. Only 2 of these mines, however, had samples
with levels of radium-226 greater than or equal to 20 pCi/g. Two of the three
other metals mines sampled had at least one sample with a level of radium-226
greater than or equal to 5 pCi/g. Only one of these mines, however, had a
sample with a radium-226 level greater than or equal to 20 pCi/g.
Much of the available scientific literature concerned with radiation
effects on organisms focuses on human health; information on these radiation
effects is summarized in Table C-9 of Appendix C.
4.1.2.3 Asbestos
EPA chose to evaluate asbestos as a potentially hazardous mining waste
constituent because of the well-documented inhalation danger that asbestos
fibers, even in very small quantities, pose to human health. The health
effects of asbestos exposure and the rationale for the level of asbestos
considered in this report to be potentially hazardous are described below.
4-31
-------
Table 4-13 Results of Radioactivity Analyses of Solid Waste Samples
Mining
industry
segment
Metals:
Copper
Gold
Iron
Lead
Molybdenum
Si 1 ver
Uranium
Zinc
Other metal sa
Subtotal
Nonmetals:
Phosphate
TOTAL
Number of
sampl es
analyzed
17
4
8
4
6
6
58
10
7
120
67
187
Number of samples
with Ra-226 levels
greater than
or equal to 5 pCi/g"5
0
0
0
0
0
0
40 (69%)
0
5 (71%)
45 (38%)
24 (36%)
69 (37%)
Number of samples
with Ra-226 levels
greater than
or equal to 20 pCi/gb
0
0
0
0
0
0
29 (50%)
0
2 (29%)
31 (26%)
3 (4%)
34 (18%)
alncludes antimony, bauxite, beryllium, mercury, nickel, rare earth metals,
titanium, tungsten, and vanadium.
Numbers in parentheses show percentage of samples taken in that industry
segment having the potentially hazardous characteristic.
Sources: PEDCo Environmental, Inc. 1984, ERCO 1984, and Harty and Terlecky 1982.
4-32
-------
Table 4-14 Number of Waste Management Operations
Having Radioactive Samples
Number of
operations
with at least
one sample
with level of
Number of
operations
with at least
one sample
with level of
CO
00
Mining
industry
segment
Uranium
Phosphate
Other metal sa
Total
Type of waste
management
operation
No. mines involved
Mine waste
No. mines involved
Mine waste
Tailings
No. mines involved
Mine waste
Tailings
No. mines involved
Mine waste
Heap/dump leach
Tailings
Number of
operations
sampled
17
17
13
13
10
3
2
3
62
55
2
41
Ra-226 greater
than or equal
to 5 pCi/g
17
17
10
8
6
2
2
2
29
27
0
8
Ra-226 greater
than or equal
to 20 pCi/g
14
14
2
0
2
1
1
1
17
15
0
3
alncludes antimony, bauxite, beryllium, mercury, nickel, rare earth metals,
titanium, tungsten, and vanadium.
Source: PEDCo Environmental, Inc. 1984 and ERCO 1984.
-------
According to the 1982 EPA Support Document for the Final Rule on Friable
Asbestos-Containing Materials in School Buildings, "the hazards of asbestos
exposure identified by epidemiologic research are cancers of the lung, pleura,
peritoneum, larynx, pharynx and oral cavity, esophagus, stomach, colon and
rectum, and kidney. Inhalation of asbestos fibers also produces a non-
cancerous lung disease, asbestosis." Pleural and peritoneal mesotheliomas
(cancers) are considered "signature" diseases for asbestos exposure; that is,
these diseases are almost always caused by asbestos exposure. There are
well-documented cases of mesotheliomas occurring in persons residing within a
g
mile of an asbestos mine who had no other known asbestos exposure.
EPA has promulgated a National Emission Standard for asbestos (40 CFR
Part 61, Subpart M) under Section 112 of the Clean Air Act, establishing
asbestos disposal requirements for active and inactive disposal sites. The
regulation requires owners and operators of demolition and renovation projects
to follow specific procedures to prevent asbestos emissions to the outside
air, and further requires that demolition and renovation material be
controlled if the material contains more than 1 percent asbestos by weight in
a form that "hand pressure can crumble, pulverize, or reduce to powder when
dry." In this report, the Agency used this 1 percent criterion to determine
when mining wastes should be considered potentially hazardous on the basis of
their asbestos content.
Only five waste samples obtained from asbestos mining and milling sites
were analyzed for asbestos. The results of these analyses, shown in
Table 4-15, indicate that the asbestos content of all of these samples greatly
exceeded 1 percent.
4-34
-------
Table 4-15 Results of Asbestos Analyses
Sample
number
1
2
3
4
5
Type of
asbestos
Chrysotile
Chrysotile
Chrysotile
Chrysotile
Chrysotlle
Estimated percentage
asbestos
by weight
20-40
5-20
70-85
30-50
70-90
Source: Based on analyses performed by the Industrial
Environmental Research Laboratory, U.S.
Environmental Protection Agency, Cincinnati, Ohio.
4-35
-------
Regulations in Subpart M of 40 CFR Part 61 also contain standards for
emissions from asbestos mills and active and inactive asbestos waste disposal
sites. According to these regulations, owners and operators of asbestos mills
must ensure that their facilities either discharge no visible emissions to the
outside air, or use air cleaning devices to clean emissions as specified in 40
CFR 61.154. Owners and operators of active asbestos waste disposal sites must
ensure that no visible asbestos emissions are discharged to the outside air,
cover asbestos-containing waste material at least once a day, or receive
approval from the Administrator of EPA to use alternate control measures. The
regulation also requires security measures for active and inactive asbestos
waste disposal sites.
There is evidence that asbestos is present in many of the wastes generated
by the metals mining industry segments covered in this report. Asbestiform
amphibole fibers from taconite mill tailings were detected at high
g
concentrations (14-644 million fibers per liter) in Lake Superior.
Sampling performed by EPA's Effluent Guidelines Division to develop effluent
limitations guidelines and standards for the ore mining and dressing point
source category showed that asbestos fibers were present in mine or mill water
from almost all metals mining industry segments. Based on these results
and on a statistical comparison with the suspended solids data, EPA found that
by controlling the suspended solids in the discharge, the asbestiform fiber
concentrations were effectively controlled in this industry.
Some effects of asbestos exposure, such as toxicity, bioaccumulation,
cytotoxicity, asbestosis, and carcinogenicity on humans, bacteria, aquatic
biota, and rats are summarized in Table C-10 in Appendix C.
4-36
-------
4.1.2.4 Acid Formation Potential
The exposure and subsequent oxidation of naturally occurring metal
sulfides (especially iron pyrite) in ores and mining waste can produce acid,
which may increase the leaching and mobility of toxic waste constituents,
including the heavy metals. Wastes that contain significant amounts of iron
pyrites (FeS^) or other base metal sulfides may release acids and metals for
many decades. The hazard is initiated by the chemical reaction of air, water,
pyrite, and pyrrhotite or other iron-bearing sulfides to produce sulfuric acid:
4FeS2 + 15 02 + 14H20—4Fe(OH)3,+ 8H2$04
For example, the oxidation of the pyrite in 1 ton of waste having a 1 percent
pyritic sulfur content would produce 15 kilograms of sulfuric acid. Unless
the acid is neutralized (by the alkalinity of the water or by reaction with
carbonate material in the waste), the acid will reduce the pH of the water and
increase the concentration of the potentially toxic waste constituents,
especially metals, that are leached and transported.
The potential effect of acid drainage on the concentration of metals in
leachate is illustrated in Figure 4-2. For example, at a pH of 5.5, the free
metal ion concentration in equilibrium with solid oxides or hydroxides of
mercury (Hg) is approximately 0.0002 mg/1. If enough acid is added to the
water to reduce the pH from 5.5 to 4.5, the concentration of mercury increases
to more than 0.02 mg/1, an increase of more than two orders of magnitude.
Although the diagram is an oversimplification and does not reflect the
complexities of the real world, it does demonstrate that acid may greatly
increase the concentration of metals in leachate and exacerbate environmental
hazards.
4-37
-------
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-------
For this report, EPA estimated the quantity of metal mining waste that
poses an acid drainage problem, using information on the mineral content of
metal ores from 115 mines producing more than half of all the tailings
generated by the metals mining industry segments represented in the U.S.
Bureau of Mines Minerals Availability System data base.
To estimate whether the tailings from these mines have high, uncertain, or
no acid formation potential, EPA made the following assumptions:
t If the data base reports that the minerals content of the ore in a
particular mine includes pyrites and/or other metal sulfides but does
not include carbonates, the tailings from that mine have a high
potential for forming acid.
• If the data base reports that the minerals content of the ore in a
particular mine includes pyrites and/or other metal sul fides and
carbonates, the tailings from that mine have an uncertain potential
for forming acid.
• If the data base reports that the minerals content of the ore in a
particular mine does not include pyrites and/or other metal sulfides,
the tailings from that mine have no potential for forming acid.
The number of mines that generate tailings with high, uncertain, and no
acid formation potential are presented, by industry segment, in Table 4-16.
According to Table 4-16, mines having the highest acid formation potential are
found in the copper, gold, and silver industry segments.
The limitations of these data are:
• The data base does not report the mineral composition of the soil or
rock that is removed at mines to gain access to an ore body. It was
assumed that ore constituents were similar to waste (gangue)
4-39
-------
Table 4-16 Estimated Acid Formation Potential of Tailings at Active
Metal Mines by Industry Segment
Mining
industry
segment
Copper
Gold
Iron
Lead
Silver
Zinc
Number
of active
mines for
which minerals
data exists
24
15
25
15
19
18
Number of
mines with high
acid formation
potentiala»d
9 (38)
6 (40)
0
1 (7)
6 (31)
0
Number of mines
with uncertain
acid formation
potential b»d
13 (54)
3 (20)
9 (36)
14 (93)
10 (53)
17 (94)
Number of mines
with no acid
formation
potentiaic.d
2 (8)
6 (40)
16 (64)
0
3 (16)
1 (6)
a High Acid Formation Potential - Tailings derived from ores containing pyrites
and/or other metal sulfides but no carbonate minerals (which would tend to neutralize
produced acids).
b Uncertain Acid Formation Potential - Tailings derived from ores containing pyrites
and/or other metal sulfides and carbonate minerals. (Such wastes may or may not
produce acid, depending on the relative ratio of acid-forming to acid-neutralizing
minerals.)
c No Acid Formation Potential - Tailings from ores containing no pyrites or other metal
sulfides.
d Numbers in parentheses are percentage of all mines in an industry segment.
Source: Derived from ore minerals information in U.S. Bureau of Mines Mineral
Availability System data base. For this analysis, only mines active in 1982 were
considered.
-------
constituents, but it is not clear that this extrapolation could be
extended from tailings to overburden. For example, the overburden
may be completely different from the ore and have no acid formation
potential.
• The reason that EPA categorized the acid formation potential of
tailings from mines having both acid-forming minerals (i.e.,
sulfides) and acid-neutralizing minerals (i.e., carbonates) as
uncertain is that the actual acid formation potential of these
tailings may range from high to none, depending on the relative
concentrations of acid-forming and acid-neutralizing minerals in the
tailings. The concentration processes at some mills require the
addition of alkaline materials, which are mixed with the tailings and
would reduce the acid formation potential of these high-sulfide,
low-carbonate ores.
• The presence or absence of water, which is necessary for pyrite
oxidation products to form acid, was not considered when categorizing
the acid formation potential of these tailings, although many mines
are located in arid regions of the country, where the lack of water
reduces the potential for acid drainage.
a EPA has not considered whether chemical, mineralogical, biological,
cl imatological, or physical factors might also influence the ability
of tailings from particular mines to form acid.
Acid drainage can lower the pH of streams and other surface water.
Table C-ll in Appendix C of this report provides a summary of the effects of
decreased pH levels on fish.
4-41
-------
4.2 ESTIMATED AMOUNTS OF POTENTIALLY HAZARDOUS MINING WASTE
EPA's methodology for estimating the amount of potentially hazardous
mining waste is presented in Appendix B to this document. EPA's estimate of
annual generation of hazardous waste and of the costs of treating and
disposing of hazardous waste are based on projections of the number of mines,
the amount of waste generated annually, and the amount of waste existing on
site during 1985. EPA felt that a projection to 1985 was preferable to using
historical data because of the rapid changes occurring in the mining industry
in recent years (i.e., declining production in many segments).
Table 4-17 shows these estimates for eight mining industry segments:
asbestos, copper, gold, lead, phosphate, silver, uranium, and zinc. Since
there were no data on asbestos mines in EPA's data base, results for asbestos
are based on historical data rather than projections; these data probably
overestimate the number of active asbestos mines and the amount of waste
generated at these mines annually, since EPA is aware that fewer than four
asbestos mines are now in operation. EPA did not project results for the iron
and molybdenum industry segments, because the wastes generated by these
segments do not exhibit any of the hazard characteristics for which EPA
tested. In addition, the other metals industry segments are not included in
this analysis because of the small number of mines in these industry segments
and the small amount of potentially hazardous waste generated at these mines
annually.
As shown in Table 4-17, the copper industry segment generates the largest
amount of waste annually: 632 million tons per year. The phosphate industry
segment, generating 518 million tons of waste per year, has the second highest
rate of annual waste generation. In many industry segments, the amount of
waste existing on site is very large, exceeding the annual amount of waste
generated by a factor of 20 to 40.
4-42
-------
Table 4-17 Estimated Number of Active Mines, Annual Amount of Waste
Generated, and Waste Existing on Site for 1985
Mining
industry
segment
Asbestos**
Copper
Gold
Lead
Phosphate
Si 1 ver
Uranium
Zinc
Estimated
number
of active
mines
4
22
100
7
34
50
50
12
Annual generation
of waste (millions
of metric tons)
5
632
65
9
518
17
91
3
Wastes existing
on site
(millions of
metric tons)9
NA
20,789
218
395
16,599
57
1,564
19
NA indicates data not available.
a Data extrapolated to industry segment based on estimates from Charles River
Associates.
b Asbestos estimates developed by EPA.
Source: Adapted from Charles River Associates 1985c.
4-43
-------
Table 4-18 presents EPA's estimates of the amount of mining wastes
generated annually that exhibit the RCRA hazardous waste characteristics and
mining wastes that may be potential candidates for listing, by industry
segment. The estimated amount of corrosive waste generated annually is 50
million metric tons a year. All of this corrosive waste is generated by the
copper industry segment. The estimated amount of EP toxic wastes generated
annually is 11.2 million metric tons per year, and 63 percent of this EP toxic
waste is generated by the gold industry segment. EP toxic waste is also
generated by the lead, silver, and zinc industry segments.
Table 4-18 also shows the amount of wastes generated annually of the types
that may be potential candidates for listing. The amount of copper dump leach
waste (a potential candidate for listing because of low pH and elevated EP
toxicity) generated annually is 182 million metric tons. Wastes from gold and
silver metal recovery and heap leach operations may be potential candidates
for listing because of their high levels of cyanide. The gold and silver
industry segments generate 9.3 million metric tons of metal recovery wastes
and 14 million metric tons of heap leach wastes annually that may be potential
listing candidates. The gold industry generates larger amounts of these
wastes annually than the silver industry.
Table 4-19 presents estimated annual generation amounts for wastes with
hazardous characteristics that are particularly relevant to mining industry
wastes: acid formation potential, radioactivity, and friable asbestos
content. EPA estimates that 95 million metric tons of waste have a high
potential for forming acid; all of this waste is generated in the copper
industry segment. This estimate of waste having high acid formation potential
is probably low, because EPA could only estimate the acid formation potential
4-44
-------
Table 4-18 Estimated Amount of Waste with RCRA
Characteristics Generated Annually and Mining Wastes
That May be Potential Candidates for Listing
-pa
en
RCRA characteristics
Mining
industry
segment
Asbestos
Copper
Gold
Lead
Phosphate
Silver
Uranium
Zinc
TOTAL
Amount of waste
generated annually
(million metric
tons/year)
5
632
65
9
518
17
91
3
1,340
Corrosive
waste
(million
metric
tons/year)
0
50
0
0
0
0
0
0
50
EP toxic
waste
( mi 1 1 i on
metric
tons/year)
0
0
7
2.9
0
1
0
0.3
11.2
Potential candidates for listing
Copper dump
leach wastes
(million metric
tons/year)
0
182
0
0
0
0
0
0
182
Cyanide-treated
gold and silver
metal recovery
wastes (million
metric tons/year)
0
0
9
0
0
0.3
0
0
9.3
Gold and silver
heap leach
wastes (million
metric tons/year)
0
0
11
0
0
3
0
0
14
Source: Derived by EPA from data in Charles River Associates 1985c, PEDCo Environmental, Inc. 1984, and ERCO 1984.
-------
Table 4-19 Estimated Annual Amount of Waste Generated Exhibiting Other
Potentially Hazardous Characteristics, By Industry Segment
-p>
en
Mining
industry
segment
Asbestos
Copper
Gold
Lead
Phosphate
Silver
Urani urn
Zinc
TOTAL
Annual
production
of waste
(million metric
tons/year)
5
632
65
9
518
17
91
3
1,340
High acid
formation
potential
(million metric
tons /year)
0
95
0
0
0
0
0
0
95
Radi um-226
greater than or
equal to 5 pCi/g
(million metric
tons/year)
0
0
0
0
352
0
91
0
443
Radi um-226
greater than or
equal to 20 pCi/g
(million metric
tons /year)
0
0
0
0
13
0
80
0
93
Friable
asbestos content
greater than
1% by weight
(million metric
tons/year)
5
NA
NA
NA
NA
NA
NA
NA
5
NA indicates data not available.
Source: Derived by EPA from data in Charles River Associates 1985c, PEDCo Environmental, Inc. 1984,
and ERCO 1984.
-------
of tailings (see Section 4.1.2.4). In addition, EPA classified the acid
formation potential of many tailings piles as uncertain because of lack of
data on the relative proportion of acid-forming to acid-neutralizing minerals
in these tailings, even though some of them probably have a high potential for
forming acid.
Table 4-19 presents estimates of radioactive waste at two radioactivity
level s~radium-226 equal to or exceeding 5 pCi/g, and radium-226 equal to or
exceeding 20 pCi/g. At the 5-pCi/g level, there are 443 million metric tons
of radioactive waste generated annually, 352 million metric tons in the
phosphate industry segment, and 91 million metric tons in the uranium industry
segment. If the 5-pCi/g level is used as the hazard criterion, radioactive
waste is the largest single contributor to the total amount of potentially
hazardous waste generated by the industry segments of concern. At the
20-pCi/g level, 93 million metric tons of hazardous radioactive waste are
generated annually: 13 million metric tons in the phosphate industry segment,
and 80 million metric tons in the uranium industry segment.
The total amount of waste generated annually with a friable asbestos
content of more than 1 percent by weight is 5 million metric tons per year.
This amount may be an underestimate, because EPA did not sample wastes from
industry segments other than the asbestos industry for their friable asbestos
content.
Table 4-20 shows the estimated amount of potentially hazardous mining
waste generated annually, by industry segment. If the radioactivity criterion
used is 5 pCi or more of radium-226 per gram, 755.2 million metric tons of
potentially hazardous mining waste are generated by these segments annually.
If the radioactivity criterion chosen is 20 pCi or more of radium-226 per
gram, 405.2 million metric tons of potentially hazardous mining waste are
4-47
-------
J2.
oo
Table 4-20 Total Amount of Potentially Hazardous
Mining Waste Generated Annually
Annual
production
Total amount of
waste with RCRA
Total amount
of potentially
hazardous waste''
(if Ra-226
is greater than
Total amount
of potentially
hazardous waste"3
(if Ra-226
is greater than
Mining
industry
segment
Asbestos
Copper
Gold
Lead
Phosphate
Silver
Uranium
Zinc
TOTAL
of waste
(million metric
tons/year)
5
632
65
9
518
17
91
3
1,340
characteristics
(million metric
tons /year)3
0
50
7
2.9
0
1
0
.3
61.2
or equal to 5 pCi )
(million metric
tons /year)
5
276
24
2.9
352
4
91
.3
755.2
or equal to 20 pCi )
(million metric
tons /year)
5
276
24
2.9
13
4
80
.3
405.2
a RCRA characteristic waste means corrosive or EP toxic waste.
b Total potentially hazardous waste means corrosive and EP toxic waste, waste containing
cyanide at a level greater than 10 mg/1, radioactive waste, wastes containing friable
asbestos content greater than 1 percent by weight, and waste with high acid formation
potential.
Source: Derived by EPA from data in Charles River Associates 1985c, PEDCo Environmental Inc.
1984, and ERCO 1984.
-------
generated annually. These total estimates do not equal the sum of the amounts
of waste considered hazardous based on individual hazard characteristics,
because waste from a single operation may be classified as potentially
hazardous for several different reasons. For example, 50 million metric tons
of copper dump leach are corrosive; however, this waste is also included in
the estimate of 182 million metric tons of copper dump leach waste that may be
a potential candidate for listing.
Sixty-one million metric tons of mining industry waste are hazardous,
according to the RCRA hazardous waste characteristics of corrosivity and EP
toxicity; for comparison, the total amount of hazardous waste generated
annually by all nonmining industry segments combined is 64 million metric
tons. The portion of mining industry waste that is hazardous because it is EP
toxic or corrosive is less than 5 percent of the total amount of waste
generated by these industry segments. Of mining industry wastes that may be
classified as hazardous because they are EP toxic or corrosive, 82 percent are
from copper dump leach operations that generate corrosive wastes, and an
additional 11 percent are EP toxic waste generated by the gold industry
segment.
Wastes that are hazardous according to the RCRA hazardous waste
characteristics of corrosivity and EP toxicity constitute 8 percent of the
total amount of potentially hazardous mining waste generated annually, if the
radioactivity hazard level chosen for radium-226 is equal to or more than 5
pCi/g. If the radioactivity hazard level for radium-226 is equal to or
greater than 20 pCi/g, mining wastes that are hazardous according to the RCRA
characteristics of corrosivity and EP toxicity comprise 15 percent of the
total amount of potentially hazardous waste generated annually.
4-49
-------
4.3 EFFECTIVENESS OF WASTE CONTAINMENT AT MINING WASTE SITES
Because a large amount of mining and beneficiation waste is potentially
hazardous, human health and the environment could be adversely affected if
these wastes escape containment. EPA commissioned a contractor study to
determine whether mining waste management facilities leak and, if they do,
whether they release constituents of concern into surface or ground water.
The Agency also reviewed the results of other monitoring and mining studies to
corroborate its findings.
4.3.1 EPA Study
EPA selected eight mining sites at which to monitor ground and surface
water. The study focused on four types of waste (mine waste, tailings, dump
leach waste, and mine water) and five mining industry segments (copper, gold,
lead, uranium, and phosphate). Seven specific region-commodity categories of
waste were monitored: Arizona copper tailings ponds, New Mexico copper dump
leach wastes, gold tailings ponds from Nevada and South Dakota, Missouri lead
tailings, New Mexico uranium mine water ponds, Idaho phosphate mine waste
piles, and Florida phosphate tailings.
Ground water and surface water were monitored at four sites, ground water
only at three sites, and surface water alone at one site. At each site, four
or five samples were taken over a 6- to 9-month period. Samples were analyzed
for selected indicators, properties, or compounds that might be evidence of
leakage: antimony, arsenic, barium, beryllium, cadmium, calcium, chloride,
chromium, copper, cyanide, fluoride, iron, lead, magnesium, manganese,
mercury, molybdenum, nickel, nitrate, phosphate, potassium, selenium, silver,
sodium, sulfate, thallium, vanadium, zinc, acidity, alkalinity, conductivity,
pH, radionuclides, settleable solids, suspended solids, total dissolved
solids, total organic carbon, and turbidity.
4-50
-------
Table 4-21 shows the Agency's interpretation of the monitoring results.
These results indicate, with a reasonably high degree of confidence, that most
of the facilities sampled do leak. However, the data do not demonstrate
conclusively that constituents reach concentrations of concern at all sites or
that they migrate over long distances.
At the copper mine sites, only ground water was monitored, because
southwestern streams, in general, flow only after storms. The site at which
copper tailings were monitored has surface runoff diversions for such events.
This site also uses thickened discharge, recovers about 50 percent of its pond
water, caps filled tailings ponds with alluvium, and then revegetates.
Monitoring results showed chloride concentration gradients and an increase in
total dissolved solids and sulfate over time in all wells, indicating seepage
from the copper tailings pond. Concentrations of sulfate (four to six times
higher than natural, local unimpacted levels) and total dissolved solids (two
to four times higher than natural but within range for the aquifer) exceeded
national drinking water standards in all wells and were even higher for the
tailings pond. (Drinking water standards include the National Interim Primary
Drinking Water Standards (NIPDWS) and National Secondary Drinking Water
Standards. These standards are used as a basis for comparison.) Although the
well farthest from the water table mound formed from pond seepage had the best
water quality, concentrations of metals were very low (near detection limits)
in all wells.
Copper dump leach liquor at the operation studied was very acidic,
contained high levels of total dissolved solids, and exceeded nearly all
primary and secondary drinking water standards. The pregnant leach liquor is
collected in a leachate collection pond and pumped back to the precipitaion
4-51
-------
Table 4-21 Results of the Monitoring Program
en
ro
Industry
segment and
management
practice
Impact on
Copper tail ings
pond
Copper dump leach
Gold tailings pond
Gold tailings pond
Lead tailings
Uranium mine
water pond
Phosphate
overburden pile
Phosphate sand
and clay tailings
Surface Ground
water water
NMa
NM
no
yes
no
NM
no
no
yes
yes
yes
yes
no
yes
NM
no
Seepage indicators
Comments
a NM indicates not monitored.
Source: PEDCo Environmental, Inc. 1984
Sulfate, IDS, chloride
Sulfate, IDS
Cyanide, chloride, sulfate,
nickel, and ammonia
Cyanide, chloride, IDS,
and pH
Sulfate, IDS, chloride
Sulfate, chloride, IDS,
and radionuclides
IDS, fluoride, chloride,
total phosphorus, and
total organic carbon
Low concentration of metals
Seepage is recharging the aquifer
IDS, sulfate, and zinc concentrations
in downgradient wells equivalent to
concentrations in tailings pond
water
Surface water degradation after storms.
Cyanide not detected in surface water.
Metals did not exceed drinking water
standards, although several other
indicators did
Monitoring continues at this site;
tailings may be having an effect on
shallow ground water
Barium, a precipitating agent, also
found downgradient to pond
No observable impact
Seepage greater in shallower aquifer
-------
plant. At this site, ground-water degradation was evidenced by increased
concentrations of calcium, sulfate, and total dissolved solids. The leach
pile area is in an unlined natural drainage basin, and seepage from it
apparently is recharging the aquifer. (Although a hydrogeologic study was not
conducted to confirm that the mine pit acts as a ground-water sink, the bottom
of the mine pit is 700 feet lower than the water level in the background well.)
Gold tailings ponds receive cyanidation process wastes, have high
concentrations of cyanide, arsenic, cadmium, lead, mercury, and selenium, and
are typically alkaline. Cyanide was not detected in surface water near either
of the gold tailings ponds, although low but detectable cyanide levels in
wells at both sites indicate seepage to ground water. At the first site, an
underground mine, ore is crushed and then leached with a sodium cyanide
solution. Significant downstream increases were found for fluoride, specific
conductance, potassium, magnesium, sodium, and sulfate. These increases were
thought to be caused largely by natural weathering processes, and the
concentrations never exceeded South Dakota cold-water fish propagation stream
standards. Alkalinity decreased downstream, and surface water was not
considered to be impacted by the tailings pond. The strongest indicators of
tailings pond water seepage into ground water are the presence of constituents
added during the beneficiation process: chloride and cyanide. Cyanide was
detected in three (of six) downgradient monitoring wells; chloride in two.
Additionally, sulfate, sodium, nickel, and ammonia concentrations indicated
seepage. Cadmium, manganese, iron, sulfate, and total dissolved solids were
at or exceeded levels permitted by the drinking water standards. An
independent analysis of these data concluded that concentrations of zinc,
total dissolved solids, and sulfate in downgradient wells were essentially the
12
same as concentrations in the tailings pond water, supporting the
conclusion that contaminants had migrated.
4-53
-------
The second mine site in the gold mining industry also employs cyanide
leaching. Spent leach liquors and leached ore are disposed of in tailings
ponds; decant water is recycled to the mill. In surface water, concentrations
of arsenic, manganese, total dissolved solids, and fluoride were significantly
higher downstream than upstream, but cyanide was not detected. Tailings pond
releases during storms and snowmelt were likely to be responsible for
downstream water contamination. Ground-water monitoring revealed
concentrations that exceeded drinking water standards for arsenic, manganese,
pH, chloride, fluoride, nitrate, lead, manganese, and total dissolved solids.
Seepage from abandoned underground mines may have contributed to these
elevated levels, particularly for arsenic and manganese. Cyanide was detected
at low levels in two of four wells, but metal concentrations did not exceed
levels permitted in drinking water standards. The presence of cyanide and the
increasing concentrations of total dissolved solids and chloride indicate
tailings pond leakage.
The underground lead mine selected for the EPA study is in Missouri, where
approximately 80 percent of all lead production occurs. The crushed ore goes
through a froth flotation circuit, and tailings are pumped to a pond. This is
a zero-discharge facility; a seepage and collection system recycles water to
the milling system. Surface water monitoring indicated significant increases
in calcium, magnesium, total dissolved solids, sulfate, nitrate, and chloride
downstream. These increases were attributed to natural weathering processes,
as all levels were within the range reported for streams that do not receive
lead mining waste. Although small amounts of cyanide are used to process
these ores, cyanide was not detected in surface water. The copper level
exceeded the level specified in Missouri standard for the protection of
4-54
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aquatic life both upstream and downstream from the tailings pond. Ground-
water monitoring revealed high concentrations of sodium, fluoride, chloride,
sulfate, and total dissolved solids; the latter three were considered evidence
of seepage. In one sample, total dissolved solids exceeded permissible
drinking water standard levels. Groundwater continues to be monitored at this
site, which has a set of shallow and deep wells. Preliminary analysis
indicates that tailings are having a greater impact on the water quality of
the water in the shallower wells.
Only ground water was monitored near uranium mine water ponds in
New Mexico. Uranium is recovered from surface and underground mining at this
site. Waste management practices include overburden and waste piles, as well
as unlined settling ponds. Permissible levels specified in drinking water
standards were exceeded in several wells for selenium, nitrate, sulfate,
manganese, and total dissolved solids. Elevated concentrations of magnesium,
calcium, and sodium reflected the poor quality of the water in the aquifer.
High levels of nitrate, magnesium, and total organic carbon may have resulted
from leakage from a pond formerly used for sewage disposal. Gross beta and
gross alpha concentrations were elevated, and measurable levels of radium-226
were also found. High concentrations of sulfate, chloride, total dissolved
solids, and radionuclides in downgradient wells are considered indicators of
pond seepage. Elevated downgradient levels of barium are another indication,
because barium chloride is added to precipitate radium before water is
discharged to the pond.
The impact of phosphate mine waste (overburden) was evaluated at a mine in
eastern Idaho. This is an open-pit mining operation in which the overburden
is generally backfilled to inactive mine sites. Waste rock is usually graded
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and revegetated. Surface runoff is collected in basins to remove suspended
solids before the water is discharged. EPA concluded, based on monitoring
results, that current mining operations have little impact on surface water.
Ground water was not monitored, because there were no suitable well sites.
In Florida, surface water and ground water were monitored near phosphate
sand and clay tailings. Several waste management practices are used: the
clay fractions are slurried to settling ponds and overflow is reused; sand
tailings are used as backfill; overburden is piled or used in dike
construction. Although levels of fluoride and sulfate were elevated in
surface water, quality did not appear to be affected by the tailings. No
monitored constituent exceeded its Florida Water Quality Standard. Two
ground-water aquifers were monitored: a shallow water table aquifer and a
deeper Floridian Aquifer. Elevated levels of several constituents in tailings
serve as good indicators of seepage: sodium, sulfate, fluoride, total organic
carbon, total phosphorus, radium-226, gross alpha, and gross beta. Of these,
sodium, total organic carbon, fluoride, and total phosphorus were statistic-
ally higher in one or more wells downgradient to both aquifers than in
respective background wells. Although the fluoride level exceeded that of the
drinking water standards, all levels were within the range of ambient
conditions. Chloride and total dissolved solids, however, were higher than
ambient conditions, indicating that sand tailings constituents enter ground
water. In conclusion, data indicate that neither clay slime ponds nor sand
tailings have seriously affected the quality of shallow ground water. To
date, neither practice has had an impact on the deeper Floridian Aquifer, but
this aquifer may be recharged by the upper aquifer.
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Table 4-22 compares selected concentrations of indicators in ground-water
monitoring wells near the mine site with drinking water standards and water
quality criteria, where these values are available. Ground-water degradation
may be attributable to current and/or past mining practices, although
naturally poor background water quality exists in some areas. Further
degradation may occur if additional waste constituents (notably metals that
have not thus far appeared in high concentrations in the monitoring wells)
migrate in the future. Factors governing leaching rates, fate, and transport
of constituents are complex, highly site specific, and dependent on
physicochemical properties of both the waste and the local subsurface
environment. For example, pH, reduction-oxidation potential, adsorption,
coprecipitation processes, and complex chemical and hydro!ogic interactions
are unique to each site. Seasonal factors that could not be assessed because
of the time constraints of this study are other localized influences on
constituent migration and transport. For these reasons, the results of this
study cannot be directly extrapolated to industry segments employing similar
waste management practices. Other studies may help place this monitoring
study in perspective.
4.3.2 Other Studies
This review is not comprehensive, but provides conclusions from earlier
EPA studies and studies conducted by state and local governments and the
academic community.
Mines can contaminate ground water through waste disposal practices, but
the nature of the contamination is highly variable and site specific.
Copper waste management practices leak constituents into both surface and
ground water. Factors that affect the migration of this leakage include ion
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Table 4-22 Concentrations3 of Seepage Indicators in Ground Water at Selected Monitoring Sites0
-Pi
1
un
00
Constituent
Chi ori de
Cyanide
Fluoride
Nickel
Radium -2 26
Sulfate
Total dissolved
sol i ds
Permissible
level in Water quality
drinking water criteria for
standards0 aquatic life**
250
0.02 - 0.2 0.0035
1.4 - 2.4e
0.056f
5 pCi/1
250
500
Gold
tailings Lead
pond tailings
1.94 - 58.4 22.8 - 44.8
0.02 - 1.76
0.10 - 0.31
800 - 1,200 38 - 108
269 - 556
Uranium
mine water
ponds
26-210
0.25 - 0.33 pCi/1
770 - 1,810
1,650 - 5,800
Phosphate
tail ings
55.3 - 63.2
1.85 - 6.58
169 - 205
a Concentrations are in milligrams per liter except as otherwise indicated.
b Values are from one or more wells downgradient or upgradient (or both) from the site.
c National Interim Primary Drinking Water Standards (NIPDWS) or Secondary Drinking Water Standards, except for
cyanide, where the "detection" limit is given.
d Values are for chronic freshwater animal toxicity.
e Temperature dependent.
f At a hardness of 50 mg/1 CaCOs.
Source: PEDCo Environmental, Inc. 1984
-------
14
exchange capacity, hydraulic conductivity, and carbonate content.
Carbonate neutralizes acids, and metals will precipitate when the pH is
neutral or alkaline. A study of the Tucson mining district found that leakage
from a copper tailings pond, indicated by hardness of and sulfate in the
water, degraded ground water downgradient from the pond.
The Globe-Miami area east of Phoenix was also the focus of a study.
Copper mine runoff degraded surface water, and leaching practices degraded
ground water by lowering the pH and increasing total dissolved solids,
sulfate, copper, and other trace metal concentrations. Because of liquids
leaching through the soil, alluvia in area washes are contaminated with
sulfate, iron, and copper; the plume is advancing downgradient. Abandoned
mines have the same potential; but because of the arid climate, significant
degradation near these mines has not occurred.
The cyanidation process used in gold mining creates the potential for
cyanide migration. Cyanide can be free, part of other compounds, or strongly
complexed with metals. An EPA laboratory study showed that some forms are
mobile, while others are less so. Movement depends on the type of cyanide and
the media through which it travels. Potassium cyanide in leachate is less
mobile than water containing cyanide ions in soils. High pH and low clay
content increase cyanide mobility. In the soil, cyanide salts are biologi-
cally converted to nitrates or become complexed with metals. Without oxygen,
cyanides become gaseous nitrogen compounds. These chemical changes take place
when cyanide concentrations are low. Former mining practices that did not
include wastewater treatment before release can be the source of persistent
cyanide concentrations. One company, reopening a mine closed for nearly
40 years, found levels of cyanide far above detection limits (0.14-0.58 mg/1)
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18
while drilling test wells before activities began. Before mitigative
measures were implemented in 1982, one Nevada gold mine had ground-water
levels as high as 5,509 mg/1.19
Before proper environmental treatment systems were in place, the Missouri
Department of Conservation found a reduction in species diversity in the
aquatic habitat in the lead mining district that was directly attributable to
20
mining waste or milling effluent. In another study, surface water in the
area had low levels of dissolved metals, indicating potential transport out of
the system. A downstream lake was thought to act as a sink, and some
sediments had lead and zinc concentrations of 10 mg/1 (Missouri Clean Water
Conmission effluent guidelines are 0.05 and 0.2 mg/1, respectively, for these
metals). Releases from the sediments could create concentrations that exceed
guideline levels, although little is known about the conditions under which
21
these constituents may be relased from the sediment.
Radionuclide concentrations in uranium mine water are high, but a U.S.
Department of the Interior study showed that these concentrations are reduced
22
downstream as a result of adsorption or deposition in the soil. An
earlier EPA study of the Grants Mineral Belt (New Mexico) estimated tailings
23
pond seepage at 48.3 million gallons a year.
Idaho phosphate mining has been studied extensively. An earlier study at
the EPA site (before current management practices were in place) indicated
that mining practices had increased sediment and nutrients, added oils, and
24
reduced the aquatic habitat. Another study concluded that the potential
existed for surface and subsurface flow patterns to be altered and for water
quality to be degraded by several constituents: arsenic, cadmium, chromium,
copper, lead, molybdenum, selenium, vanadium, zinc, uranium, radium-226,
4-60
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nitrogen, and phosphorus. However, the high carbonate content reduces the
25
solubility, and thus the potential impact, of these elements. Finally, a
recent USGS survey of the phosphate mining industry indicated that neither
sand tailings nor clay slime ponds had a significant effect on ground-water
i}C
quality.
4.4 STRUCTURAL INSTABILITY OF IMPOUNDMENTS
Impoundments may also pose threats to human health and the environment if
they are not structurally stable. The structural failure of impoundments can
release large volumes of waste. The causal factors in the failure of unstable
waste structures and the subsequent flooding range from cloudbursts or minor
earth tremors to extended periods of heavy rainfall, snow, or ice, or the
27
dumping of more wastes than a saturated bank can contain.
Today there are thousands of tailings impoundments across the country that
have varying degrees of structural stability. Many of these facilities are
located in remote areas, but others are built within flood range of homes and
well-traveled roads. If these structures fail, extensive surface water
contamination, property damage, and life-threatening situations may occur.
Although dam and impoundment failures in the mining industry segments
covered in this report have not yet caused human deaths in the United States,
they have been responsible for significant environmental degradation. In
Florida, for instance, the collapse of a phosphate tailings dike in 1971
resulted in a massive fish kill and pollution of the Peace River over a
28
distance of about 120 kilometers. Other dam failures at metal mining
sites have caused water quality degradation, crop failure, reductions in land
29
values, and fish kills.
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Stability problems are becoming more acute as the grade of the ore that is
mined decreases (resulting in larger quantities of mine waste and tailings),
as dam heights increase, and as the areas near mining facilities become more
highly populated. In addition, the recent promulgation of Effluent
Limitations Guidelines and Standards for discharges to surface water may have
aggravated these stability problems, because mine owners or operators may
elect to comply with NPDES permits by impounding larger quantities of water
than in the past. The potential danger posed by these impoundments is
increased by the fact that many new, large mines are situated in mountainous
areas where it is necessary to store large volumes of waste in valleys
upstream of inhabited areas.
The Mine Safety and Health Administration's (MSHA's) recent "Report of
Progress to Implement Federal Guidelines for Dam Safety" states that
"experience has shown that the unregulated disposal of mine and mineral
3?
processing waste has the potential for disastrous consequences."
According to the U.S. Department of Agriculture, an estimated 10-20 percent of
the mine waste disposal embankments in the U.S. and Canada have experienced
33
significant slope stability problems.
Technical personnel from MSHA recently completed field evaluations of
22 metal/nonmetal mine tailings dams located in areas under Bureau of Land
Management leases. They determined that no dams were imminent hazards, but
34
they did find technical deficiencies at many of the sites. Investigations
of mine tailings impounding structures (tailings dams) in the past 2 years,
including five emergency calls requested by metal and nonmetal mine health and
safety district managers, have revealed hazardous conditions. Most of the
impounding structures inspected show some or most of these serious
deficiencies: extremely steep downstream slopes; no emergency outlet
4-62
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structures such as spillways or decant systems; high water, often up to the
crest of the dams; cracks and sloughs in the structures themselves; narrow,
uneven crests; the absence of trash racks to keep drainage pipes unclogged;
and the absence of diverting ditches to keep surface runoff from entering
35
impoundments.
4.5 DAMAGE CASES
EPA has compiled, reviewed, and analyzed data on National Priorities List
(Superfund) mine and mill sites, data on damage at other mine and mill sites
contained in state files, and information in technical reports documenting
37 38
cases of mine waste-related environmental contamination. '
Although this analysis has separated the damage cases into four separate
categories (damage at active, inactive, abandoned, and Superfund sites), it is
important to note that active sites frequently become inactive, and inactive
sites are sometimes abandoned. Therefore, some of the special environmental
problems caused by conditions at inactive or abandoned sites (e.g., the
erosion of tailings and their discharge into surface water, or the collection
39
and discharge of frequently acidic and mineralized mine water) can only be
avoided if active sites undergo some type of closure procedures before they
become inactive or are abandoned.
4.5.1 Active Sites
Problems at active mine and mill sites have been documented in Arizona,
Colorado, Florida, Missouri, Montana, and New Mexico; these sites represent
phosphate, gold, silver, copper, uranium, and molybdenum operations. Releases
ranged from catastrophic (loss of pond liner integrity, pond overflow, dam
40
failure, tailings pipeline break) to chronic (pond seepage). Contaminants
included cyanides, sulfuric acid, and metals (copper, cadmium, chromium, lead,
4-63
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mercury, and zinc). Both surface water and ground-water quality
degradation have been observed, with impairment of aquatic ecosystems most
commonly caused by massive releases. Remedial actions included relocating and
improving pipelines, replacing liners, installing of leachate recovery
systems, and stabilizing dams.
4.5.2 Inactive Sites
EPA has identified inactive mine and mill sites with environmental
contamination in Arizona, California, Idaho, Missouri, Montana, and Utah.
Mining industry segments represented include gold, silver, copper, mercury,
lead, and zinc. Catastrophic releases, often associated with heavy rains,
have resulted from dam failures, flood erosion of tailings, or dike washout.
Several sites had intermittent or seasonal problems caused by snow melt or
spring floods. Other sites, including old mine waste dumps and old tailings
impoundments, had chronic seepage or runoff problems. Contaminants measured
in surface water at concentrations greater than permissible levels in primary
drinking water standards include arsenic, cadmium, and lead. Reductions in
populations of fish and other freshwater organisms were observed near at least
12 inactive mine/mill sites that had had catastrophic or chronic releases.
Mitigation measures included dam repair, pond lining, development of diversion
ditches or secondary ponds, and lime treatment of tailings.
4.5.3 Abandoned Si tes
Many of the waste disposal practices that have resulted in major incidents
of environmental contamination at abandoned mine sites are no longer used
(i.e., the dumping of tailings into streams or onto uncontained piles). EPA
identified abandoned sites where environmental contamination resulted from
such practices in Arizona, California, Idaho, Montana, and Vermont. Gold
(placer and lode), silver, copper, lead, zinc, and unidentified hard rock
4-64
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mining segments were represented. Various combinations of runoff, erosion,
and seepage resulted in the release of arsenic, cadmium, cobalt, iron,
manganese, lead, and zinc into surface waters, with resultant stress on stream
44 45
ecosystems over stretches ranging from 2 to 80 kilometers. ' At some
sites, diversion ditches and trenches to lower the water table have been used
to mitigate these effects, but no mitigation has been attempted at most
abandoned sites.
4.5.4 National Priorities List Sites
Environmental contamination problems at the 13 abandoned mine/mill sites
on the Superfund National Priorities List (NPL) were generally caused by mine
waste disposal practices that are no longer used. These sites are located in
Arizona, California, Colorado, Idaho, Kansas, Oklahoma, and South Dakota.
Mining industry segments represented are gold/silver (five sites), asbestos
(three sites), lead/zinc (two sites), and copper (three sites). The three
asbestos sites differ from the other sites in posing an airborne hazard to
human health. The other 10 sites have chronic runoff and/or seepage, often
with acidic mobilization and transport of arsenic, cadmium, copper, iron,
lead, and/or zinc. Ground-water contamination, jeopardized water supplies, or
potentially contaminated food chains are the effects common to most of these
sites. Degradation of aquatic ecosystems also has been observed at
nonasbestos NPL sites. Mitigative measures applied to date include pond
sealing, installation of dams, berms, and diversion ditches, and use of the
waste in construction. Additional measures will be taken following completion
of the remedial plans for each site.
Brief descriptions of environmental contamination problems and threats to
human health posed by five NPL sites follow.
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1) Mountain View Mobile Home Estates is a 45-unit, 17-acre subdivision
near the city of Globe in east-central Arizona. Before 1973, three mills, the
Metate Asbestos Corporation, the Jaquays Asbestos Corporation, and the Globe
town mill, processed chrysotile asbestos from nearby mines. In 1973 the
Metate mill was found to be in violation of EPA air quality standards, and the
Gil a County Superior Court issued a temporary injunction to cease operations.
The injunction was made permanent in May 1974. Before terminating operations,
the owner of the Metate Corporation obtained a rezoning of this property into
residential subdivisions. Approximately 115,000 cubic meters of asbestos mill
tailings were used as the primary fill to level the site, which was then
covered with topsoil. The mill buildings, housing, and equipment remained
standing on the site. Lots were sold and occupied before the Superior Court
injunction was made permanent.
In October, 1979, asbestos contamination of the soil and air was detected
at the subdivision. Soil samples contained 5 to 50 percent asbestos fibers,
and air samples had as many as 78 fibers/cm . The asbestos in the soil and
the airborne asbestos had contaminated all the households that were tested.
In December 1979, the Arizona Department of Health Services ordered the
responsible asbestos companies to submit site cleanup plans to be implemented
during the spring of 1980. In February 1980, the Arizona Division of
Emergency Services, with the authorization of the governor, provided temporary
housing for the residents (population approximately 130) while their
properties were being decontaminated. The Metate mill was demolished, and
open ground was capped with 6 inches of soil. The residents returned to their
homes, but wind and water erosion exposed some of the asbestos landfill
material on the surface of the soil, in the earth around the homes, and in two
washes draining the site.
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In April 1983, the Centers for Disease Control in Atlanta issued a health
advisory for the site, noting continuing health hazards. The Remedial
Investigation and Feasibility Study funded by EPA proposed three solutions to
the problem.
The site abandonment option was chosen because it was the least costly of
the three and eliminated the need for continued site monitoring and selection
of an offsite disposal area. In addition to relocating the individuals in
this community, it was necessary to demolish existing structures. In this
particular case, mining waste contamination made the housing structures unfit
for habitation and ruined the community.
2) Acid drainage discharging from numerous mines and dumps at the Iron
Mountain site in California flows into Boulder Creek and Slickrock Creek, both
tributaries of Spring Creek. Concentrations of cadmium, copper, iron, and
zinc in the waters of these creeks exceed their respective permissible levels
in Federal drinking water standards by factors of 2 to 5. Spring Creek, with
its load of toxic metals, enters into the Sacramento River. The water supply
intake for the city of Redding (population approximately 50,000) is 2 miles
below the confluence of Spring Creek and the Sacramento River; and the water
intake for Bella Vista Water District, which serves apprxoimately 15,000
people, is located 1 mile farther downstream. Water samples taken at the
Redding intake show elevated levels of cadmium, copper, iron, and zinc.
Samples of fish tissue from resident trout collected in the Sacramento River
showed high levels of cadmium, copper, and zinc.
3) At California Gulch, an NPL site in Colorado, approximately 30
private wells have been abandoned because water from these wells is unfit for
human consumption. The surface water in California Gulch has been polluted so
4-67
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extensively by acid mine drainage and the erosion of mining wastes into the
stream from the nearby mine site that the stream is devoid of any aquatic life.
4) In 1962, the Celtor Chemical Works in Hoopa County, California, was
abandoned by its owners/operators after they received numerous citations for
contributing to pollution and fish kills in the Trinity River. Tailings ponds
and piles located on the flood plain were the sources of contaminants. In
1964, 2 years after closure of the operation, a flood obliterated the
structures and washed the tailings into the stream bed. As late as 1982, soil
and sediment samples collected both on site and off site showed elevated and
potentially health-threatening levels of cadmium (1.4 to 94.0 ppm), copper
(140 to 2700 ppm), lead (6 to 1900 ppm), and arsenic (4.7 to 40 ppm).
5) The Anaconda complex of mining, milling, and smelting facilities in
Montana disposed of approximately 5 billion tons of mining wastes in the
Silver Bow Creek/Clark Fork River. For a stretch of approximately
180 kilometers, the river system was heavily damaged by tailings materials
that were deposited in the river bed and in stream meanders. The river has
recently begun to recover, and the beginning of a renewal in aquatic life can
be seen in small plants and microinvertebrates that have become reestablished
there. Although the waste disposal practices of the early to mid-1900s that
caused this destruction are now prohibited by state and Federal laws; e.g.,
the Clean Water Act, the results of the waste practices of 40 years ago may
take another 40 years, and a considerable amount of resources, to undo.
4.6 RISK ANALYSIS
As shown in the previous portions of this section, some wastes from mining
and beneficiation do have the potential for being hazardous to human health
and the environment. EPA's waste sampling and analysis indicate that some
4-68
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mine waste and mill tailings are EP toxic, generally for lead. The sampling
and analysis also showed that some leachates from copper leach dump operations
have the characteristic of corrosivity, with a pH less than 2.0; and even
those that are slightly less acidic can seriously jeopardize the quality of
ground water. Other waste streams, although not hazardous under current RCRA
characteristics, contain potentially hazardous concentrations of asbestos,
cyanide, or radioactive isotopes. Some tailings have the potential for acid
formation, and tailings impoundments may be subject to catastrophic breaks.
Ground-water monitoring studies by EPA and other organizations have
demonstrated that seepage from tailings impoundments into ground water is
common. Finally, various degrees of damage have been caused by chronic or
sudden releases from active, inactive, or abandoned mine and mill sites.
The previous portions of this section do not, however, provide
quantitative estimates of releases, exposures, or risks associated with
various mine and mill waste disposal practices. Without this information, the
efficacy of current and alternative management practices cannot be compared.
Therefore, EPA is now studying the use and release of cyanides and acids at
typical mining and beneficiation operations. Specifically, cyanide releases
from metal recovery circuits and heap leaching operations are being examined.
Sulfuric acid releases being examined include those from active, inactive, and
abandoned copper leach dumps and copper mill tailings impoundments.
EPA also has begun general studies relating the respective locations of
drinking water supply systems and human population centers to mines and
mills. A preliminary analysis, based on the Federal Reporting Data System,
indicates that for 58 mine/mill sites, 20 have public ground-water systems
within 5 kilometers of the site. These public water systems serve populations
ranging from 42 to 47,494. Another EPA data base, the Graphic Exposure
4-69
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Modeling System, uses Census Department data for population distributions and
shows that people live within 5 kilometers of the mines at 30 of the 58 sites,
with total populations between 5 and 11,736. Only 11 of the 58 sites have
both resident populations and public ground-water systems within 5 kilometers.
If EPA identifies significant mining waste releases of cyanides, acids, or
other constituents of concern, further analyses will focus on actual or
potential risks to human populations or aquatic ecosystems. These studies
will take into consideration the properties of various kinds of mine
overburden, mill tailings, and heap/dump materials. Constituents other than
EP toxic metals will be examined to determine whether their release can
jeopardize aquatic organisms. Degradation, attenuation, precipitation, and
other processes affecting the transport of released materials will be
examined. To assess the potential for ground-water contamination,
site-specific estimates will be made for such factors as porosity,
permeability, and moisture content in the unsaturated zone, and for hydraulic
conductivity in the saturated zone.
The risk analyses will be used to quantify threats that releases from mine
and mill wastes pose to human health and the environment. These analyses will
permit EPA to consider the wide variation in mining practices and settings,
and to determine how changes in management practices can be implemented to
improve and protect human health and the environment. EPA would conduct risk
analysis as part of the development process for any major regulation of
hazardous waste from the mining and beneficiation of ores and minerals.
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4.7 SUMMARY
To identify mining and beneficiation wastes with the potential to endanger
human health and the environment, EPA conducted an extensive program of
sampling and analyzing mine waste, mill tailings, and wastes from heap and
dump leach operations to determine their chemical properties. These studies
were supplemented by data from ground-water monitoring, estimates of acid
formation potential, a survey of state files to obtain documented cases of
damage to human health and environment, and a review of the pertinent
literature. In the sampling and analysis studies, corrosivity and EP toxicity
were measured, because they are the RCRA Subtitle C characteristics most
likely to be exhibited by wastes from mines, mills, and leach operations. The
radioactive content of many solid and liquid samples also was measured. When
appropriate, measurements were taken of asbestos or cyanide content. Most
mine waste samples, most settled solid samples, and some low-grade ore samples
were also subjected to a modified EP toxicity test, in which deionized water,
rather than acetic acid, was used as the extracting medium. It should be
noted that EPA has not yet performed quantitative assessments of the risks
posed by mining wastes. These will require measurement or estimation of waste
constituent transport, as well as receptor population exposure, dose, and
response.
Extrapolating from the sampling and other analytic results, EPA estimated
the amounts of potentially hazardous waste generated by the mining industry
segments of concern annually. Estimated amounts are: 50 million metric tons a
year (MMTY) of corrosive wastes; 11 MMTY of EP toxic wastes; 23 MMTY of
cyanide-containing wastes; 95 MMTY of wastes with high acid formation
potential; and 182 MMTY of copper leach dump wastes with the potential for
releasing toxic metals and acidic (but not corrosive) liquids. If a
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radioactivity level of 5 pCi per gram of waste is chosen as the radioactivity
hazard criterion, 352 MMTY of phosphate mine waste and mill tailings and 91
MMTY of uranium overburden and low-grade ore would be considered hazardous.
The total amount of potentially hazardous waste generated annually, 755 MMT,
is not equal to the sum of the wastes in these categories because some of the
wastes are in more than one category.
Analyses of ground water monitoring results and damage cases showed that a
number of constituents leak from tailings impoundments and copper leach dump
operations. However, it is not clear that this seepage constitutes a danger
to human health, although it could degrade the quality of water in aquifers.
The instability of impoundment dams was identified as a possible threat to
human health and the environment, with damage at active, inactive, and
abandoned sites attributed to catastrophic releases of impounded slimes,
sands, and water.
In assessing the 13 mine/mill sites on the National Priorities List (NPL),
prepared under the Comprehensive Environmental Response, Compensation, and
Liability Act (CERCLA), EPA determined that the contamination problems
associated with these sites were generally caused by disposal practices no
longer used. Natural recovery and decontamination processes at these sites
have been slow, and additional time and resources will be needed before
recovery is complete.
To determine the degree of risk from wastes at existing mine, mill, and
leaching operations, identified as hazardous or potentially hazardous, EPA is
conducting studies on release rates, exposure pathways, and possible effects
on human health and the environment. These risk assessments will permit EPA
to consider the wide variability in mining wastes and environments and to
determine which changes in management practices would be most beneficial.
4-72
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SECTION 4 FOOTNOTES
1 PEDCo Environmental, Inc. 1984.
2 ERCO 1984.
3 Harty and Terlecky 1982.
4 Liquid wastes are also considered corrosive and therefore hazardous if
they corrode steel at a rate greater than 6.35 rrni per year at a test
temperature of 55°C, as determined by the test method specified in National
Association of Corrosion Engineers Standard TM-01-69, standardized in "Test
Methods for the Evaluation of Solid Waste, Physical/Chemical Methods" or an
equivalent test method approved by the Administrator (40 CFR 261.22). "EPA
chose metal corrosion rate as its other barometer of corrosivity because
wastes capable of corroding metal can escape from the containers in which
they are segregated and liberate other wastes" (45 FR 33109, May 19,
1980). Because of the preliminary nature of the findings of this report,
and because mining wastes are not likely to be stored in metal containers,
EPA's corrosivity analyses for this report are based solely on the pH
measure.
5 Wastes are also considered EP toxic (and thus hazardous) if the extract
of a representative sample of waste contains any of the following
pesticides or herbicides at levels specified in 40 CFR 261.24 (b), Table 1:
Endrin; Lindane; Methoxychlor; Toxaphene; 2,4-D; 2,4,5-TP Si 1 vex. EPA did
not use the EP toxicity test to analyze mining wastes for these
contaminants.
6 US EPA 1982a.
7 US EPA 1982a.
8 US EPA 1982b.
9 Cook et al. 1976.
10 US EPA 1982a.
PEDCo Environmental, Inc. 1984.
12 Williams and Steinhorst 1984.
13 US EPA 1977.
14 PEDCo Environmental, Inc. 1984.
Pima Association of Governments 1983.
4-73
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16 Gordon 1984.
17 US EPA 1976.
18 Letter to Nevada Division of Environmental Protection from
Margaret Hills, Inc. 1981.
19
File memo from Cortez Gold Mines, Cortez, NV, 1983.
20
Ryck and Whitely 1974.
21 Jennett and Foil 1979.
22
U.S. Department of the Interior 1980.
23 US EPA 1977.
24 Platts and Hopson 1970.
25 Ralston et al. 1977.
26 U.S. Geological Survey, U.S. Bureau of Land Management,
and U.S. Forest Service, 1977.
27 Carroll 1983.
9ft
" BOM 1981 a.
29 SCS Engineers 1985.
Soderberg and Busch 1977.
31 Klohn 1981.
32 MSHA 1983.
33 USDA Forest Service 1979a.
34 MSHA 1983.
35 MSHA 1983.
36 The data from the state files and the National Priorities List were not
analyzed in depth, nor were any of the sites visited, but enough documented
cases were obtained to demonstrate the range and severity of contamination
problems that may be associated with mine and mill waste disposal.
37 SCS Engineers 1985.
4-74
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op
Unites et al. 1985.
?Q
Jy Martin and Mills 1976.
40 Schlick and Wahler 1976.
41
Missouri Geological Survey 1979.
42 Gordon 1984.
43 SCS Engineers 1984.
44
Schrader and Furbish 1978.
45 Jennett and Foil 1979.
4-75
-------
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SECTION 5
THE ECONOMIC COST
OF POTENTIAL HAZARDOUS WASTE MANAGEMENT
This section examines the potential cost to facilities and selected
segments of the mining industry if EPA were to regulate mining and
beneficiation wastes under the hazardous waste controls of Subtitle C of
RCRA. The cost study on which these estimates are based was restricted to
five major metal mining segments (copper, lead, zinc, silver, and gold), and
covered mines currently active in 1984. The estimates do not cover mining
segments in which there are potential hazards from radioactivity or asbestos,
although studies assessing the cost of reducing exposure to radioactivity are
underway.
To examine potential costs that might be imposed on the selected metal
mining segments, the Agency constructed eight hypothetical regulatory
scenarios differing in degree of impact. These scenarios utilized
combinations of four different sets of management standards, varying in
stringency, and two different sets of hazardous waste criteria for determining
which waste streams would be regulated. The estimated incremental costs
reflect the added expenditures that facilities and industry segments would
incur above and beyond the cost of current waste management practices.
The results are tentative, since they are based on only a sampling of
sites, very general engineering cost evaluations, and various hypothetical
regulatory scenarios. Nevertheless, the estimates do provide a first
approximation of the potential level and variation of cost under the specified
assumptions. They do not evaluate broader economic effects such as implied
5-1
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mine or mill closings, employment losses, price changes, or international
trade effects.
The subsections below describe the methods and summarize the results.
5.1 COST METHODOLOGY
To estimate the costs of potential regulation, EPA (1) established
criteria for determining whether waste is potentially hazardous; (2) developed
hypothetical alternative regulatory standards for waste management practices
with different degrees of stringency; (3) estimated the incremental cost of
imposing those standards at a large sample of mining facilities; and (4)
extrapolated these results to the universe of applicable mining facilities in
the segments covered by the study.
The cost study focused only on currently active (1984) "major" mines—
i.e., mines generating greater than 10,000 short tons of ore per year, except
for gold and silver operations where a lower production cutoff was used. For
the five metal segments studied (copper, lead, zinc, gold, and silver), the
study results cover approximately 190 active mine sites representing an
estimated 95 percent of the total active mines and 99 percent of the total
amount of waste currently generated in these five segments.
EPA established two levels of criteria, referred to here as Scenarios A
and B, for determining whether waste is hazardous. EPA also defined four
levels of regulation, varying from imposing full Subtitle C regulations (most
stringent) to imposing only a basic maintenance and monitoring function (least
stringent). Combining the two hazardous waste scenarios and the four
regulatory standards resulted in eight different scenarios.
To estimate the additional cost of each of these eight scenarios at
specific sites, EPA (1) identified the capital and operation and maintenance
5-2
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needs for each scenario; (2) developed engineering cost functions reflecting
these requirements; (3) established a data base with all the necessary
information (e.g., waste volumes, acreage, perimeter distance, current waste
management practice) for estimating costs from the cost functions; and (4)
applied information from 47 specific mines to the cost functions to develop
the incremental costs at those sites.
Finally, EPA extrapolated the site-specific results to the universe of
mining waste to develop industry totals. It did so by projecting from the
site-specific cost by industry segment (copper, gold, silver, lead, zinc), by
waste operation (mine waste, leach operation, tailings), and by scenario. The
distinguishing feature of this approach is that the costs reflect real-world,
site-specific data.
5.1.1 Hazardous Waste Criteria
Regulated waste volumes depend on the criteria selected for determining
whether wastes should be regulated, and EPA used the basic waste character-
istics described in Section 4 to specify which waste streams should be
considered as potentially hazardous for costing purposes, creating two sets of
waste: "A" and "B." (Estimates of the volume of potentially hazardous wastes
are discussed in Section 4.2.)
"A-Scenario" Wastes include waste streams meeting the Subtitle C tests for
EP toxicity and corrosivity. In addition, they include gold mine tailings
wastes from cyanide-process metal recovery operations (originally promulgated
as interim final Subtitle C listed hazardous wastes prior to the Section 3001
exempti on).
"B-Scenario" Wastes include all wastes under the "A" list, as well as:
• Gold and silver heap leach operations (because of cyanide content);
5-3
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t Wastes with high acid formation potential--i.e., those found to
contain high sulfides (mainly pyrites) and low carbonate or other
buffering mineral content (as defined in Section 4); and
• Copper dump leach liquids (because of acidity).
The "B" list of wastes represents a range of mine waste characteristics of
concern over and above the hazard characteristics already contained in
existing EPA hazardous waste regulations as expressed by the "A" list. The
Agency examined the "B Scenario" list to be able to explore, quantitatively
and systematically, the waste quantity and management cost implications of
regulating these additional wastes of concern.
5.1.2 Regulatory Standards
EPA structured four regulatory alternatives for different levels of waste
management practice. The regulatory alternatives covered a range of
variations on Subtitle C management standards, ranging from the full set of
standards at one extreme to a much more modest program of basic preventive
maintenance and ground-water monitoring at the other end of the spectrum.
The Full Subtitle C Regulatory Scenario (Scenario 1) provides for a full
application of current EPA hazardous waste regulation to potentially hazardous
"A" or "B" mine waste, leach piles, and mill tailings. For present costing
purposes, it represents a maximum cost strategy, including: a security fence
around the perimeter, capping of both existing and new waste sites at closure,
corrective action via interceptor wells for existing waste amounts (assuming
10 percent of the sites need them), and liners for all new waste piles,
leaching areas, and tailings ponds. It also requires activities common to all
of the alternative management strategies:
t Permitting;
• Surface water run-on and runoff diversion/collection
ditches (mine waste only);
5-4
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• Ground-water monitoring wells and testing;
• Leachate collection ditches; and
• Post-closure inspection, drainage maintenance, and
ground-water monitoring.
The Tailored Standard Scenario (Scenario 2) represents an intermediate
cost alternative. This scenario includes the five common activities listed
above. However, the waste management technique here is distinguished by
substitution of waste treatment processes where considered feasible—namely,
the removal of cyanide from gold and silver tailings and removal of sulfides
(pyrites) from copper mill tailings. The scenario assumes that all sites
would require interceptor wells because it assumes a 100 percent failure rate
for all waste sites, except for treated wastes at gold and copper sites
(treatment is the alternative to interceptor wells).
The Corrective Action Scenario (Scenario 3) also represents an
intermediate alternative with to regulatory standards that are less stringent
than those embodied in Scenario 1. The applicable activities are identical to
those listed under Scenario 2 (including the 100 percent failure assumption),
with the exception that cyanide is not removed from gold and silver tailings,
and sul fides are not removed from copper mill tailings.
The Basic Maintenance and Monitoring Scenario (Scenario 4) includes only
the five activities common to the other scenarios. By design, this represents
a least-cost scenario consistent with providing a measure of protection
against surface water contamination and a first warning of any offsite
movement of contaminated leachate. It can also be regarded as the first stage
of a corrective action strategy.
Combining the four regulatory standard alternatives with the two
alternative sets of potential hazard criteria yields eight possible levels of
5-5
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cost. Table 5-1 summarizes the definitions of costing scenarios in terms of
their alphanumeric designations: the numbers 1 through 4 represent the
alternative regulatory standards, and the letters A and B represent the
applicable potential hazard criteria.
5.1.3 Estimating Incremental Costs at Specific Sites
EPA identified the cost elements required for each scenario. Cost
elements are the individual capital requirements, and individual operation and
maintenance requirements. EPA also developed engineering cost functions for
each cost element for performing the activities that the management standards
require. EPA then created a data base for 47 mining facilities that
incorporated the information necessary to calculate costs from the engineering
cost functions. This included identifying the current waste management
practice (baseline practice) at each of the 47 sites. This information was
necessary to develop incremental costs that reflect the costs of practices
required under each of the four regulatory standards above and beyond the
baseline practice. In addition, the data base incorporated information
relative to site-specific geography, product production, total waste
quantities, waste quantities that would meet the hazardous waste criteria,
type of industry, and type of waste operations. Finally, EPA computed the
incremental cost for each scenario at each site by applying the data base
information to the engineering cost functions.
5.1.3.1 Cost Elements
As discussed previously, imposing various degrees of regulation requires a
different mix of outlays for capital, operation, and maintenance. The mix of
cost elements varies by the stringency of the regulatory standard. For
convenience, Table 5-2 summarizes the cost elements included in each of the
four regulatory standard scenarios. A discussion of each element follows.
5-6
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Table 5-1 Definition of Costing Scenario
Variations by specified hazards
Variations by type of
regulatory approach
"A" SCENARIOS: Subtitle C
Definitions:
• EP Toxicity Characteristic
• Corrosivity Characteristic
• Cyanide Gold-Mine Tailing
Liquid Waste
"B" SCENARIOS: Subtitle C Above,
Plus!
• Cyanide Toxicity Characteristic
0 High Acid Generation Potential
Characteristic
• Copper Dump Leach Listing
1. Full Subtitle C Regulations
2. Tailored Standards
(varying by type of hazard)
3. Corrective Action
100% failure bracket
4. Basic Maintenance and
Monitoring
Zero failure bracket
5-7
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Table 5-2 Summary of Cost Elements Included for Each Scenario
Regulatory scenario
Cost
1.
2.
3.
4.
5.
6.
7.
8.
el ement
Permitting
Leach ate system
Monitoring system
Run-on/runoff system
Post-closure maintenance
and operation
Site security
Liners (new waste only)
Closure cap
1 2
X X
X X
X X
X X
X X
X
X
X
3
X
X
X
X
X
4
X
X
X
X
X
9. Tailings treatment
(for copper and gold)
10. Corrective action via
interceptor wells
Note: Explanations as to variations between and within scenarios are
contained in the text.
a Only for existing accumulated waste sites (that were closed at time of
RCRA implementation).
b Exceptions: gold and copper tailings (subject to treatment instead).
5-8
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Permitting. Mining operations with hazardous wastes would require RCRA
permits. Permits would be based on geological and engineering studies
describing the plan for managing wastes and containing or treating
contamination. Incremental costs in this study vary among states with more
advanced permitting requirements and those with less.
Site Security. RCRA regulations require that security be provided to
prevent the general public and livestock from coming into contact with
hazardous waste. For this study, EPA assumed that operators of facilities
would install and maintain cyclone fences around all hazardous waste areas
during their active lifetime and a 30-year post-closure period.
Caps and Liners. RCRA Subtitle C rules require caps when disposal sites
are closed and that new waste landfills and impoundments be lined. The cap
assumed for this study consists of vegetation, topsoil, clay or sand,
polyethylene cover, and clay. We assumed that liners were composed of a
combination of clay and synthetic liner materials.
Monitoring Wells. RCRA rules require ground-water monitoring of hazardous
waste disposal sites. The study assumes that wells will be located around the
general perimeter of each waste disposal operation (500 feet between each
well), and that four replicate samples will be taken and analyzed twice a year
for appropriate contaminants.
Run-On and Runoff Systems. Regulations provide that precipitation be
directed around hazardous waste piles to avoid leaching of contaminants.
Runoff from surfaces of piles must also be controlled. The costs here reflect
primarily ditching and flow control systems.
Leachate Collection Systems. RCRA rules require a system to collect and
treat contaminated seepage from hazardous waste piles. A full system
includes: (1) ditches or trenches on the downgradient sides of the waste pile;
5-9
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(2) an intermediate liquid storage system; and (3) a chemical treatment plant.
Corrective Action via Interceptor Wells. At some sites, contamination
migrates into ground water, forming a plume that can migrate from the site.
When this happens, RCRA Subtitle C rules require corrective action. For this
study, EPA assumed that interceptor wells would be installed in the plume, or
at the downgradient edge of the plume, to pump the contaminated water to the
surface. EPA assumed that all contaminated water would be sent to a treatment
plant. In Scenario A, interceptor wells are installed at closure only for
existing waste.
Tailings Treatment. This applies only to Scenario 2 where treatment of
new waste is employed when feasible rather than interceptor wells.
Specifically, EPA assumes that future gold and copper ore tailings would be
treated to separate out pyrite concentrates for disposal as a hazardous waste,
using a flotation circuit, and that a treatment plant would be installed to
destroy cyanide in gold beneficiation operations.
Closure. When the useful life of a waste pile or tailings pond is over,
the study assumed the site would be capped with impervious cover material.
The design and cost of the cap depends on whether the waste site is from past
operations or future operations.
Post-Closure. Operation and maintenance (O&M) costs are assumed to be
incurred for 30 years after closure. The annual O&M costs would consist of
several elements: (1) maintenance of the cap and fencing; (2) inspection; (3)
detection or compliance monitoring; (4) maintenance of the run-on and runoff
systems; (5) operation of the leachate collection; and (6) operation of the
interceptor well/treatment system.
Financial Assurance. RCRA Subtitle C rules require firms to demonstrate
that they can meet closure and post-closure costs. They may do so by posting
5-10
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surety bonds, by purchasing a letter of credit, by establishing a trust fund,
by purchasing an insurance policy, or by passing a financial test.
5.1.3.2 Cost Functions
Engineering cost functions were developed for each of the waste management
practice cost elements listed in Table 5-2. The functions generally take the
form: C = aV , where C = cost, a = a constant, V = the volume of waste,
and b = the elasticity of cost with respect to volume (which shows how cost
changes as a result of small volume changes). Many of the functions use the
number of acres or perimeter distance as the independent variable rather than
waste volume. Permitting costs are based on type and size of mine, as well as
current State agency permitting requirements.
5.1.3.3 Sample Facility Data Sources
The Agency's cost study utilized and built upon a mine facility data base
providing site-specific data for 47 metal mining properties, with information
on geophysical characteristics, mine/mill technologies and efficiencies,
2
historical production levels, and other salient factors. Additional site-
specific data were assembled on the type and size of current waste management
areas and practices, as well as life expectancy of ore bodies and current
production cost factors. The data were supplemented by survey information on
current State mining waste regulations. These data provide the primary inputs
for estimating historical and current mine, tailings, and leach pile waste
generation rates as well as simulating baseline management practices at each
of the 47 properties.
EPA waste characteristics sampling data were available for one or more
waste streams at 41 of the 47 facilities; and the combination of these two
data sources then formed the basis for calculating potentially hazardous waste
quantities and incremental hazardous waste management compliance costs for
5-11
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each database facility under the various hypothetical regulatory scenarios,
using the cost functions previously described.
Appendix B provides a fuller discussion of the facilities data base, the
methods used in estimating waste generation rates, and the techniques employed
to extrapolate waste quantities and compliance costs from the sample sites to
the segment totals for the mining segments in the study.
5.1.4 Total Number of Facilities and Waste Quantities Regulated
EPA aggregated the site-specific regulated waste quantities, capital
costs, and O&M costs for each facility in the data base by industry, by
scenario, and by waste operation. The resulting industry totals for numbers
of facilities affected and regulated waste quantities are summarized for the
specific segments in Table 5-3.
As indicated in Table 5-3, 99 out of 191 metal mining facilities
(52 percent) and 67 million metric tons out of a total annual generation of
725 million metric tons (9 percent) of metal mining waste would be subject to
potential Subtitle C regulation under Scenario A. However, except for gold,
less than half of the facilities in any given segment would be affected.
Furthermore, not all of a given affected facility's waste sources would
necessarily be subject to regulation. For example, copper mine and tailings
wastes were not found by our sampling to be potentially hazardous under our
Scenario A definition, but some copper dump leach piles are potentially
hazardous in Scenario A. This accounts in part for the relatively low
percentage of waste meeting the hazard criteria, in contrast to the higher
percentage of facilities. In addition, the (listed) cyanide process tends to
dominate the gold milling/processing operation, but a relatively smaller
fraction of total waste.
5-12
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Table 5-3 Numbers of Potential RCRA Mine Facilities and
Quantities of Hazardous Waste in EPA Cost Study,
Scenario A and B, by Mining Sector
Copper
Gold
Silver
Lead
Zinc
Total s
Copper
Gold
Silver
Lead
Zinc
Total s
Number of
Regul ated/
total
6/22
75/100
12/50
3/7
3/12
99/191
21/22
100/100
25/50
3/7
3/12
152/191
facilities
Percent
regulated
27
75
24
43
25
52
96
100
50
43
25
80
Annual
(millions
Regulated/
total
A__
50/632
13/65
1/17
3/9
0.3/2.4
67/725
B_ _„
276/632
24/65
4/17
3/9
0.3/2.4
307/725
waste generation
of metric tons/year)
Percent
regulated
7.9
19.6
5.7
33.3
11.5
9.3
43.7
36.6
22.3
33.3
11.5
42.3
Source: Estimated by Charles River Associates 1985a.
5-13
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In Scenario B, the fraction of firms under regulation increases to about
80 percent overall, and the fraction of regulated waste increases to about
40 percent. Almost all copper sites (although still less than half of the
total waste volume) would face regulation under this scenario, as well as all
gold mines (due to cyanide heap leach and metal recovery). For silver, lead,
and zinc, the fraction of facilities affected ranges from 25 to 50 percent and
the fractions of waste regulated from 11 to 33 percent under Scenario B..
This methodology relies on the use of real-world sites with site-specific
information concerning prevailing regulations and current waste management
practices, geography, and mine operations. It requires a high level of detail
in building up the cost estimates for each EPA data base site. The results
presented below are based on the application of this methodology to a large
sample (47) of real-world sites and the extension of those results to the
remaining sites.
5.2 POTENTIAL COSTS OF RCRA SUBTITLE C WASTE MANAGEMENT
This section discusses potential costs for the metal mining industry in
the aggregate, for individual segments, and for individual mine facilities if
certain wastes were managed as hazardous wastes under various regulatory
scenarios. The discussion also provides some insights as to the relationship
of compliance costs to mine production costs.
5.2.1 Potential Total Cost for the Metal Mining Industry
EPA's cost analysis leads to three principal findings with respect to
total potential cost. The first is that the waste management costs of RCRA
could be quite substantial under the types of regulatory scenarios that this
report considers, as Table 5-4 illustrates. In annual ized cost terms, costs
for the five metal mining segments would be measurable in the millions of
5-14
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Table 5-4 Potential Total Cost For Metal Mining Industry9
Under Various RCRA Regulatory Scenarios
Regul atory
scenarios"
1A
2A
3A
4A
IB
28
3B
4B
Lifetime0
($ millions)
$2,421
937
1,036
128
9,985
3,577
2,809
330
DPVLd
($ millions)
$1,279
305
332
60
5,746
1,139
800
137
Annual e
($ million)
$185
47
46
7
854
210
118
17
a Industry segments include: copper, lead, zinc, gold, and silver.
b See Subsection 5.1.1 and Table 5-1.
c Lifetime cost (1985 dollars), not discounted, including: closure and 30
years post-closure costs for existing wastes; opening and managing a new
waste management facility for 15-year future operations; closure at end of
15th year; post-closure management for 30 years.
d Discounted Present Value of Lifetime Costs, as listed in note (c). Real
discount rate of 9.0 percent.
e Lifetime Costs Annualized over 15-year future mine production period using
a real discount rate of 9.0 percent.
Source: Estimated by Charles River Associates 1985a.
5-15
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dollars per year up to several hundred minion dollars per year over a 15-year
mine production cycle. Lifetime costs (undiscounted) for operating the mines
in five metals segments would be measurable in the hundreds of million
dollars, possibly up to several billion dollars over the next 15 years of mine
production.
The second major conclusion is that costs vary substantially among the
RCRA management scenarios chosen for analysis. Generally speaking, the
highest cost scenarios (1A and IB) are several times more costly than the
intermediate cost counterparts (2A and 3A, 2B and 3B). Similarly, the minimum
maintenance and monitoring scenarios (4A and 4B) cost only a fraction as much
as the intermediate cases.
The third finding is that the additional waste management cost incurred by
adding additional B-Scenario wastes is also very substantial: Scenario B is
typically two to four times more costly than Scenario A for given regulatory
standards or strategies.
The figures presented in Table 5-4 assume that the potentially hazardous
portions of both existing waste (accumulated at these sites from past
operations) as well as new (future) waste generated at these sites would be
managed as RCRA Subtitle C hazardous waste. If only new wastes generated in
the future were to be regulated, the costs would be 40 to 70 percent of those
shown in Table 5-4, depending on the scenario considered.
5.2.2 Potential Costs for Individual Segments
Potential total costs for the five individual metal mining segments vary
widely among the segments analyzed and across alternative regulatory
scenarios, as Table 5-5 illustrates. By far, the largest aggregate lifetime
cost for each alternative falls on copper mining, because of the extremely
large quantities of waste and the relatively high proportion of total waste
5-16
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Table 5-5 Potential Total Costs For Selected Metal Mining Sectors
Under Various RCRA Regulatory Scenarios
Sector
Subtitle C
Tailored standards
1A
IB
2A
2B
Lifetime costs {$ million)3
Copper
Gold
Silver
Lead
Zinc
Total s
Copper
Gold
Silver
Lead
Zinc
Total s
Copper
Gold
Silver
Lead
Zinc
Total s
$1 ,400
670
46
260
45
$2,421
Di
$ 710
370
28
140
26
$1,279
$ 110
48
4
19
4
$ 185
$8,300
1,200
180
260
45
$9,985
scounted present
$5,000
490
90
140
26
$5,746
Annuali zed costs
$ 740
75
16
19
4
$ 854
$400
250
60
180
47
$937
value ($ mill
$ 96
110
23
58
18
$305
$2,400
770
180
180
47
$3,577
ion)b
$ 770
230
63
58
18
$1,139
($ million/year)0
$ 14
17
4
9
3
$ 47
$ 150
37
11
9
3
$ 210
a Lifetime cost (1985 dollars), not discounted, including: closure and
30 years post-closure costs for existing wastes; opening and managing a
new waste management facility for 15-year future operations; closure at
end of 15th year; post-closure management for 30 years.
b Discounted Present Value of Lifetime Costs, as listed in note (a).
Real discount rate of 9.0%.
c Lifetime costs annualized over 15-year future mine production period,
using a real discount rate of 9.0%.
Source: Estimated by Charles River Associates 1985a.
5-17
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that is of potential concern, particularly in the dump leaching and milling
operations. The gold segment bears the second highest lifetime total cost
since most gold production uses cyanide processes either in leaching or
milling operations.
5.2.3 Potential Costs for Individual Mine Facilities
As noted previously, the number of mine facilities that might be subjected
to hazardous waste regulations is highly uncertain, depending on various
possible definitions of hazardous waste constituents, variations in natural
mineral deposits, and differences in ore processing methods. EPA waste
sampling suggests wide variations among different segments as to percentage of
mines with potentially hazardous waste, as well as wide variations within
individual segments regarding possible quantities and characteristics of such
waste materials. This section examines potential cost implications for
individual facilities among and within the five segments analyzed.
Table 5-6 provides a comparative summary of individual mine facility cost
estimates for two illustrative scenarios--Scenario IB (the highest cost
scenario estimated) and Scenario 4B (the lowest cost scenario for the B-waste
group). Potential costs are presented on both a lifetime and an annual ized
basis. For the high-cost scenario (IB), average lifetime costs for affected
facilities would range from $7 million for silver mines up to almost $400
million for individual copper mines. Annualized and discounted over a 15-year
mine production cycle, these would translate into new annual average cost
burdens for individual mines, ranging from $600,000 per year (silver mines) up
to $35 million per year (copper mines) per facility.
The facilities with the highest costs—those with the greatest volumes of
potentially hazardous wastes or especially difficult management conditions--
would experience additional management costs that would be significantly
5-18
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Table 5-6 Potential Incremental Compliance Costs
For Individual RCRA Mine Facilities
For High- and Low-Cost Scenarios
Copper
Gold
Silver
Lead
Zinc
Copper
Gold
Silver
Lead
Zinc
Copper
Gold
Silver
Lead
Zinc
Scenario IB
Scenario 4B
Average
facility
Maximum
cost
facility3
Average
facility
Maximum
cost
facility3
390
12
7
85
15
240
5
4
46
9
35.1
0.8
0.6
6.5
1.4
Lifetime costs ($ millions)b
,300
170
120
170
27
10.0
0.6
0.5
11.0
3.0
-Discounted present value ($ mill ion/year)c-
1
,100
63
50
110
16
3.8
0.3
0.3
4.4
1.1
-Annual ized costs ($ mi 11 ion/year)d-
190
9
10
14
4
0.50
0.04
0.04
0.57
0.20
33.0
16.0
10.0
17.0
6.0
16
8
5
7
3
2.4
0.9
0.6
1.2
0.5
3 Maximum means the maximum cost for a facility in the EPA data base.
b Lifetime cost (1985 dollars), not discounted, including: closure and
30 years post-closure costs for existing wastes; opening and managing a
new waste management facility for 15-year future operations; closure at
end of 15th year; post-closure management for 30 years.
c Discounted present value of lifetime costs, as listed in note (a).
Real discount rate of 9.0%.
d Lifetime costs annual ized over 15-year future mine production period
using a real discount rate of 9.0%.
Source: Estimated by Charles River Associates 1985a.
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higher than the average. For example, in the zinc and copper segments, a
high-cost facility would face costs about three times higher than the
average. For silver and gold, the costs of meeting the Scenario IB RCRA
regulation would be on the order of 15 times the industry average.
Differences between the two scenarios are equally striking. Facilities
employing RCRA cap and liner controls (Scenario IB) would have 5 to 40 times
more RCRA-related waste management costs over their lifetime than if they
employed only the maintenance and monitoring functions estimated for
Scenario 4B.
5.2.4 Potential RCRA Costs Relative to Mine Production Costs
Comparing potential facility compliance costs to total mine production
costs provides insight on the possible effect of RCRA Subtitle C regulations
on individual mine economics. Table 5-7 shows potential incremental
compliance costs per unit of mine product (typically, concentrated ore) and
potential incremental RCRA costs as a percentage of the segment's average
current total direct production cost. Potential cost impacts of hazardous
waste regulation for an average mine for the low-cost Scenario 4B range from
about 1 to 5 percent of total production costs for the five metal segments.
By contrast, for the high-cost Scenario IB, potential incremental RCRA
regulation costs would range from about 20 to 120 percent of current total
direct product costs, on the average, for individual facilities in the five
segments.
The high-cost mines again would experience impacts significantly greater
than the average. In Scenario IB, EPA estimates that the high-cost facilities
in all five segments would face potential RCRA compliance costs in excess of
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Table 5-7 Potential Incremental RCRA Compliance Costs
Relative to Facility Production Costs
Cost per unit of product3
(Dollars per metric ton)
Average for
affected
facilities
High-cost
facility
Percent of direct product cost3
Average for
affected
facilities
High-cost
facility
Copper
Gold
Silver
Lead
Zinc
17.6
5,625.5
267.9
5.4
28.7
i.UW-1
$ 44.1
29,466.9
1,071.5
15.4
57.3
Low-cost scenario (4B)
1.7%
1.1%
2.5%
1.9%
5.2%
4%
6%
10%
5%
10%
Copper
Gold
Silver
Lead
Zinc
$ 1,212.5
117,867.6
4,286.1
60.6
209.4
niyn-tubu
$ 3,417.1
267,881.0
16,608.6
253.5
319.7
icenor i u \. ID i -
120%
23%
40%
21%
39%
340%
54%
160%
88%
58%
3 Direct costs of mine product are based on sector averages of current
cash operating costs for facilities, as estimated by
Charles River Associates for EPA. Costs do not include facility-level
capital investment, depreciation, interest expense, or corporate overhead.
Source: Estimated by Charles River Associates, 1985a.
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50 percent of their total direct production costs. Even under the low-cost
Scenario 48, estimates for the most-affected facilities in each of the five
segments range between 5 and 10 percent of total mine production costs.
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SECTION 5 FOOTNOTES
Charles River Associates 1985a.
2
This data base was originally developed by Charles River Associates.
5-23
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SECTION 6
CONCLUSIONS AND RECOMMENDATIONS
6.1 SCOPE
As detailed in Section 1, this report covers the waste generated from the
extraction and beneficiation (concentration) of metallic ores, phosphates, and
asbestos and the mining of uranium. Although these selected mining segments
include only about five percent of the 13,000 active mining operations in the
U.S. noncoal mining industry, the facilities covered in this report generate
over 90 percent of the total waste material produced by all noncoal mines.
6.2 SUMMARY OF CONCLUSIONS
The Agency's conclusions from the studies presented in this report are
summarized under major groupings paralleling the organization of the report,
namely: (1) Structure and Location of Mines, (2) Waste Quantities, (3)
Potential Hazard Characteristics, (4) Evidence of Environmental Transport, (5)
Evidence of Damage, (6) Management Practices, and (7) Potential Costs of
Regulation.
6.2.1 Structure and Location of Mines
Because of the wide availability of detailed and comprehensive information
published by the U.S. Bureau of Mines and supplemented by data from industry
trade associations, EPA's conclusions on the numbers, sizes, and locations of
U.S. mines are based solely on these standard sources.
1. There is a relatively small number of mines in the segments under
consideration in this study. Fewer than 500 mine sites (1985)
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extract and concentrate metals, phosphates, and asbestos in the U.S.
(excluding gold placer mines). Of these, about 290 (62 percent) are
accounted for by the precious metals (gold, silver) and uranium
segments alone.
2- There is a great diversity in the size of mining facilities. This is
true whether one measures size in terms of property area, product
tonnage, total volume of material handled, or waste generated. The
largest mine sites (e.g., in the iron ore, copper, and phosphate
segments) are measured in terms of square kilometers, and each one
handles more than 10 million tons of material per year. By contrast,
about 25 percent of the mines included in this study handle less than
1,000 tons per year.
3. There is also great diversity in the unit value of product mined. In
the segments studied, this value varies from $20 per ton for crude
phosphate to over $10 million per ton for gold.
4. With few exceptions (notably in the precious metals) the trend has
been toward a reduction in the number of active mines in most
segments and an increase in the number of inactive mines, closed or
abandoned mines.
5. Metals, phosphate, and asbestos mining are very heavily concentrated
in a few States and EPA Regions. Over 90 percent of the mine sites
in the industry segments are west of the Mississippi River, and over
60 percent are concentrated in just 10 States with 20 or more mines
each. Eight of these 10 States are in the Rocky Mountain and Great
Basin regions (EPA Regions 6,8,9, and 10), where almost 65 percent of
U.S. metal mines are located.
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6. These mines are generally located In areas of low population
density. They are often, although not always, located several
kilometers from population centers and the sources of public water
supplies (reduced human exposure Impact).
6.2.2 Waste Quantities
The conclusions summarized in this section are derived primarily from EPA
studies. Waste quantity estimates are based largely on primary data from the
U.S. Bureau of Mines on ore concentration and productivity for individual mine
properties or producing regions, supplemented by EPA-sponsored engineering
studies and extrapolations. These studies and extrapolations are described in
detail in Section 4.1 and Appendix B to this report. Waste types and
quantities reported here include all mine overburden and waste rock (mine
waste), material subject to dump (copper) or heap (gold and silver) leach
operations, and tailings from beneficiation processes.
1. Annual aggregate waste quantities for these segments are large by any
standard. Mines in the metal, phosphate, and asbestos segments
produce about 1.0 to 1.3 billion metric tons per year of various
types of mining waste. By contrast, total municipal "post-consumer"
solid waste totals 150 million tons and total industrial hazardous
waste for all industries other than mining totals about 250 million
tons per year.
2. Total waste accumulated by all active, inactive, and abandoned mines
since 1910 is estimated at 50 billion metric tons.
3. Ratios of waste to product in mining vary considerably, but are
generally substantially higher than for any other industries. The
percentage of marketable ore obtained from mining operations ranges
from 60 percent of the material excavated at iron ore mines to
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30 percent at surface copper mines and 7 percent at surface uranium
mines. By contrast, 50 percent or more of all the harvested wood in
the forest products industry becomes marketed wood or paper products,
and only a very small percentage of crude oil remains as waste in the
production of fuels and petrochemicals.
4. Total waste quantities vary greatly among facilities in mining. As
noted earlier, 25 percent of the mines in this study are rated at
less than 1,000 tons per year of total material handled (well within
the waste generation range of facilities in, say, the pulp and paper
or petrochemicals industries.) On the other hand, the larger
facilities in the copper, iron, and phosphate mining segments handle
more than 10 million tons per year each. Any one of these larger
individual facilities will generate more total waste in the normal
course of its activities than all firms together in almost any other
industry.
5. Aggregate waste in mining is concentrated in a few segments and a few
states. Seventy percent of the 1.3 billion tons of total mining
waste (1982) was generated in two segments, copper (39 percent) and
phosphates (31 percent). This suggests that almost 23 percent of all
mining waste is generated in Arizona (68 percent of copper
production), and that almost 23 percent of this waste is generated in
Florida (74 percent of U.S. phosphate production). An additional 14
percent of all mining waste was contributed by iron mining (largely
in Minnesota), and 6 percent by uranium (Colorado, New Mexico, Utah,
and Wyoming). All remaining nonfuel mining segments together
generated the remaining 10 percent of total mining industry waste.
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6.2.3 Potential Hazard Characteristics
Data on waste hazard characteristics are the result of extensive EPA
sampling and analysis studies, as described in Section 4, and are based on
samples from 86 extraction and beneficiation sites.
1. Of the 1.3 billion metric tons of waste produced each year, only
61 million metric tons (5 percent) of copper, gold, silver, lead, or
zinc wastes exhibited RCRA hazardous characteristics. These include
50 million metric tons of corrosive (pH less than 2.0) copper leach
dump waste and 11 million metric tons of gold, silver, lead, or zinc
overburden or tailings that were EP toxic (generally for lead). EP
toxicity test leachates from gold, silver, lead, zinc, uranium, and
other metal wastes had toxic metal concentrations between 20 and 100
times the levels set by the National Interim Primary Drinking Water
Standards; however, these were below the threshold of being a
hazardous waste.
2. Twenty-three million metric tons per year of gold and silver wastes
are potentially hazardous because they have been leached using a
cyanide solution. These cyanide wastes include those metal recovery
wastes previously listed as hazardous, as well as heap leaching
wastes, but do not include copper mill tailings or other mill
tailings with low (less than 10 mg/liter) concentrations of cyanide
from flotation circuits.
3. Copper leach dump material (182 MMT) and copper mill tailings
(95 MMT) may be hazardous. In addition to the 50 MMT/year of copper
leach dump waste estimated to be corrosive, the remaining 132 MMT of
this waste may also pose potential hazards because of its low pH and
relatively high concentrations of toxic metals. Copper leach dump
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wastes are potentially hazardous even when the pH level of their
leachate is not below 2.0, because their leachate is still quite
acidic and contains toxic metals. However, toxic constituents in and
hazardous characteristics of these wastes do not exceed EPA's
established criteria. Similarly, copper, gold, silver, and lead mill
tailings containing high (greater than 1 percent) concentrations of
pyritic material and low (less than 1 percent) concentrations of
carbonate buffers have a high potential for forming and releasing
sulfuric acid.
4. Naturally occurring radioactivity (radium-226) levels in excess of
five picocuries per gram (pCi/g) has been estimated for 443 million
metric tons/year of wastes from sites generating uranium mine waste
and phosphate wastes. Use of an alternative radioactivity measure of
20 pCi/g yields an aggregate estimate of about 93 million metric
tons/year of radioactive waste, most of which is uranium mine waste.
5. Four asbestos mines generate about 5 million metric tons per year of
waste containing high (greater than 1 percent) asbestos fiber
content. Only asbestos mines were tested in the current study for
asbestos fibers.
6. EPA's solid waste sampling thus far has not found any hazardous
characteristic in waste from the iron ore, molybdenum, or certain
minor metals segments. The Agency tested wastes from virtually all
metal mining segments but did not test wastes from all mineral mining
segments, on the assumption that these wastes are unlikely to be
hazardous.
7. Based on the above, the Agency concludes that as many as 80 percent
of the metal mining facilities and perhaps 56 percent of the waste
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generated could be considered potentially hazardous to human health
or the environment under some circumstances. Generally, a given mine
site will exhibit only one primary problem: EP toxicity, cyanide
contamination, corrosivity/acidity, radioactivity, or asbestos,
according to the Agency's sampling results.
6.2.4 Evidence of Environmental Transport of Potentially Hazardous
Constituents
The potentially hazardous constituents and characteristics of various
mining wastes can be transported from the location of storage or disposal to
possible receptors by various combinations of surface water flow, seepage into
ground water and ground-water flow, and wind currents. The Agency's studies
in this area focused primarily on efforts to evaluate environmental transfer
to and through surface and ground water. Study methods included both a
literature search and a limited field monitoring study at eight selected mine
sites (one only for surface water) over a 6- to 9-month monitoring period.
1. Ground-water monitoring is difficult, expensive, and has seldom been
conducted at mine sites on a comprehensive basis. Because of complex
geologic strata (presence of an ore body) and the extensive size of
many mine properties, proper ground-water monitoring is technically
difficult and costly. Historical practice in the mining industry has
not required such monitoring. As a result, there is very little
available information in the literature, and almost none on a
complete or comprehensive basis. Most mines have no historical or
contemporary ground-water monitoring information.
2. EPA's limited field monitoring shows environmental transfer of mine
waste constituents to ground water, but not necessarily transfer of
the EP toxic constituents of concern. Mine waste constituents—both
indicator sulfates, chlorides, and some elements that could be
6-7
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considered environmentally harmful—were shown to migrate from waste
management areas to local aquifers. Short-term monitoring detected
seepage from tailings impoundments (a copper, lead, phosphate sand,
and two gold impoundments), a copper leach dump, and a uranium mine
water pond. However, the EP toxic constituents of concern did not
appear to have migrated at these sites during the short period of
this study.
3. EPA's limited field monitoring generally did not show contamination
of surface waters, but this may be the result of local circumstances
of management, climate, and parameters monitored. Surface water
contamination would not be expected downstream from an intact
tailings impoundment. However, abnormally heavy precipitation could
lead to releases or bypasses to protect the integrity of the
impoundment dam.
4- Other scattered monitoring study data suggest mixed or inconclusive
results regarding ground water and surface water contamination by
constituents of concern. In Arizona, copper mine runoff has degraded
surface water, and uncontained leachate from copper leach dump
operations has degraded ground water by lowering pH and increasing
concentrations of sulfates, copper, and total dissolved solids.
Abandoned gold recovery operations that did not treat wastes before
release can be the source of persistent cyanide contamination.
Generally, contaminant plumes from tailings impoundments (other than
uranium mill tailings impoundments) have not been studied.
6.2.5 Evidence of Damage
The Agency's conclusions on observed damage to the enviroment and health
are based on an extensive survey of State government natural resource and
6-8
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health agency files through 1984 to obtain evidence of environmental
incidents, followed by review and evaluation of the evidence obtained. All 50
States were surveyed by telephone, and 10 were visited. The mining sites
reported on were not visited to observe or verify data obtained in the
survey. Several hundred initially reported incidents were evaluated and
eventually narrowed down to 20 verifiable cases of damages having substantial
documentation. The damage survey was supplemented by reviews of published
reports and National Priorities List (Superfund) data.
1. Damage cases are about equally distributed between catastrophic
(sudden releases, spills) and chronic (seepage, periodic runoff)
incidents.
2. Documented damage typically involves physical or chemical degradation
of surface water ecosystems, often including fish kills or reduction
in biota, but seldom involves direct effects on human health.
3. A number of incidents of damage caused by mining wastes at currently
active sites in the phosphate, gold, silver, copper, and uranium
industries have been well documented in several States, including
Arizona. Colorado, Florida, Missouri, Montana, and New Mexico.
Similar results have been documented at inactive sites, but abandoned
and Superfund sites may have additional problems.
4. Damage to surface waters has often been reducible or reversible by
use of modified waste management practices or other physical controls.
6.2.6 Waste Management Practices
The Agency's conclusions on waste management practices are based on
literature reviews, site visits in conjunction with waste sampling,
engineering design studies, and consultation with State regulatory agencies
and mine company engineers.
6-9
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1. Site selection, including both the mine property itself and the
specific location of waste storage, treatment, and disposal
activities, is perhaps the single most important aspect of
environmental protection in the mining industry. The selection of
the mine property is based primarily on the ability of the operation
to produce a commodity (e.g., copper, gold, etc.) at a competititve
price and a reasonable profit. The cost of transporting waste via
pipeline, conveyor, or truck to the disposal site is an important
variable in determining the profitability of the mine, because of the
large volume of material moved at most mines.
2. The potential for waste utilization as a solution, or even as a
significant contributor, to waste management in most mining segments
is extremely limited.
3. There are few major innovations under development that would lead to
major changes in mine production processes or waste management
practices.
4. The difference between "best practice" and typical practice is often
significant among mines in many major segments. These differences
are related to both voluntary management practices and variations in
State regulations.
5. Within known technological options, there appear to be major
opportunities for process modifications, some source separation of
wastes, treatment of acids and cyanides, and, possibly, controlled
release of certain effluents that could significantly reduce damage
potentials in certain contexts.
6. Many waste management practices being applied to hazardous waste in
6-10
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other industries—most notably caps and liners—have not been
attempted for mining wastes.
6.2.7 Potential Costs of Regulation
The Agency conducted engineering cost analyses, using several different
hypothetical regulatory scenarios, for a sample of 47 actual sites, and then
extrapolated these costs to the universe of facilities in the copper, lead,
zinc, silver, and gold mining segments. EPA's approach, methods, and
assumptions are discussed briefly in Section 5 and in Appendix B.
1. For five metal mining segments, total annualized costs could be
substantial, but vary considerably across different hypothetical
regulatory scenarios. Annualized costs range from $7 million per
year (for a scenario that emphasizes primarily basic maintenance and
monitoring of RCRA hazardous wastes) to over $800 million per year
(for a highly unlikely scenario that approximates a full Subtitle C
regulatory approach emphasizing cap and liner containment for an
expanded range of potentially hazardous wastes).
2. Almost 60 percent of total projected annualized costs at operating
facilities can be attributed to the management of waste accumulated
from past production.
3. Costs would vary greatly among segments. Some segments may not be
affected at all (iron, molybdenum), because their waste streams
apparently do not contain hazardous constituents. Total lifetime
costs for affected segments could range from $45 million for zinc up
to $8.3 billion for copper (for the highest cost scenario).
4. Costs would vary greatly among mines within segments. Incremental
compliance costs, as a percentage of direct product cost, could vary
as much as 25:1 among facilities within a given segment. Factors
6-11
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affecting these differences include geography, ore grade, past waste
accumulation, percentage of waste with hazardous characteristics, and
process and waste management practice efficiencies.
6.3 RECOMMENDATIONS
Section 8002(f) of RCRA requires EPA to conduct a study of the adverse
effects of mining waste and to provide "recommendations for Federal...actions
concerning such effects." Based on our findings from this study, we make
several preliminary recommendations for those wastes and industry segments
included in the scope of the study. The recommendations are subject to change
based on continuing consultations with the Department of the Interior (DOI)
and new information submitted through the public hearings and comments on this
report. Pursuant to the process outlined in RCRA §3001(b)(3)(C), we will
announce our specific regulatory determination within six months after
submitting this report to Congress.
First, EPA is concerned with those wastes that have the hazardous
characteristics of corrosivity or EP toxicity under current RCRA regulations.
EPA intends to investigate those waste streams. During the course of this
investigation EPA will assess more rigorously the need for and nature of
regulatory controls. This will require further evaluation of the human health
and environmental exposures mining wastes could present. EPA will assess the
risks posed by various types of mining waste sites and alternative control
options. The Agency will perform additional waste sampling and analysis,
additional ground-water or surface water monitoring analysis, and additional
analysis of the feasibility and cost-effectiveness of various control
technologies.
6-12
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If the Agency determines through the public comments, consultation with
DOI and other interested parties, and its own analysis, that a regulatory
strategy is necessary, a broad range of management control options consistent
with protecting human health and the environment will be considered and
evaluated. Moreover, in accordance with Section 3004(x), EPA will take into
account the "special characteristics of such waste, the practical difficulties
associated with implementation of such requirements, and site-specific
characteristics...," and will comply with the requirements of Executive Orders
12291 and 12498 and the Regulatory Flexibility Act.
Second, EPA will continue gathering information on those waste streams
that our study indicates may meet EPA's criteria for listing—dump leach waste,
because of its high metal concentrations and low pH, and wastes containing
cyanides. Although these waste streams are potential candidates for listing
as hazardous wastes, we need to gather additional information similar to the
information gathered for the rulemaking for corrosive and EP toxic wastes.
When we have gathered sufficient information, we will announce our decision as
to whether to initiate a formal rulemaking. If the Agency finds it necessary
to list any of these wastes, we will also develop appropriate management
standards in the same manner as those for corrosive and EP toxic wastes.
Finally, EPA will continue to study radioactive waste and waste with the
potential to form sulfuric acid. The Agency is concerned that radioactive
wastes and wastes with the potential for forming acid may pose a threat to
human health and the environment, but we do not have enough information to be
able to conclude that they do. We will continue to gather information to
determine whether these wastes should be regulated. If EPA finds that it is
necessary to regulate these wastes, the Agency will develop the appropriate
measures of hazard and the appropriate waste management standards.
6-13
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SECTION 7
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APPENDIX A
SUMMARY OF MAJOR WASTES FROM THE MINING AND
PROCESSING OF OIL SHALES
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APPENDIX A
SUMMARY OF MAJOR WASTES FROM THE MINING AND
PROCESSING OF OIL SHALES
A.I INTRODUCTION
It is projected that the first U.S. commercial oil shale plant (Union
Oil's 10,000 bbl/day Long Ridge facility) will come on line in 1985. Other
larger plants are scheduled to start production between 1987 and 1994, and
many of these may be supported by the Federal Government through the U.S.
Synthetic Fuels Corporation. It has been estimated that in the western United
States alone, mining and processing volumes could eventually reach 1 million
metric tons per day.
The mining methods that will be used include room-and-pillar, lane-and-
pillar, open pit, and vertical-modified-in-situ (VMIS); production rates are
expected to range from about 12,000 to approximately 150,000 metric tons per
day. Downstream, or auxiliary, operations will include oil upgrading, gas
cleanup, and raw and wastewater treatment, but the processes that will be used
in these operations are more diverse and less well defined than mining and
retorting operations.
Although the types and quantities of solid wastes that will be produced by
oil shale plants are not well defined at this time, it is estimated that
production of the volume of oil shale anticipated (1 million metric tons per
day) will require the disposal of 810,000 metric tons of retorted shale per
1 The information in this Appendix has been summarized from "High Volume
Wastes from the Mining and Processing of Oil Shales," written by E.R. Bates,
U.S. Environmental Protection Agency, 1985, but not yet published.
A-l
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day, 66,000 metric tons of raw shale fines per day, and over 3,000 metric tons
per day of spent catalysts, treatment chemicals and sludges, and byproduct
wastes. This would result in 300 million metric tons per year of wastes that
must be disposed of in an environmentally acceptable and cost-effective manner.
Table A-l shows the estimated quantities of solid waste that are projected
to be produced by a commercial oil shale industry mining 1 million metric tons
per day of raw oil shale. Some of these wastes, such as spent arsenic guard
bed catalysts and API separator bottoms, will most certainly be hazardous.
For the most part, these wastes will be produced in the large-scale
solids-handling operations associated with most oil shale facilities. They
include spent shale from retorting operations, dusts recovered from air
pollution controls, and unused raw shale (sub-ore, fines, dust).
Non-marketable byproducts, oily solids, scrap, and garbage are also considered
major solid wastes.
A number of other solid wastes that may contain materials that are
classified as hazardous will also be generated by commercial oil shale
facilities. These include spent catalysts, used chemicals and sludges from
gas cleanup operations, and water treatment sludges and slurries. Hydrogen
plants, which produce hydrogen for hydrotreating the crude shale, will be the
major source of a variety of spent catalysts. As listed in Table A-l, these
catalysts may include Co-Mo and ZnO catalysts from the hydro-desulfurizer
(HDS) unit; Ni-base, Fe-O, and Cu-Zu catalysts from the reformer; Ni-base
catalysts from the methanator; and arsenic guard bed and hydrodenitrification
(HDN) catalysts from the hydrotreater. However, as can be seen from the
individual quantities and totals listed, discrepancies exist in the estimates
of quantities that may be produced.
A-2
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Table A-l Relative Quantities of Solid Wastes Potentially
Generated by the Oil Shale Industry
Type of
waste
Mean Quantity of
Waste Produced
(metric tons/
million metric
tons of shale
mined)
Standard Deviation
(metric tons/
million metric
tons of shale
mined)
Percent
Uncertainty3
(*)
Data
Points
(N)
Major Solid Wastes:
Spent Shale
Raw Shale
Rejects
Off-Spec
Byproducts
Oily Solids
Scrap and
Garbage
TOTAL5
Spent Catalyst
Hydrogen Plant0
HDS Unit
Co-Mo
ZnO
Reformer0
Ni-base
Fe-Cr
Cu-Zn
Methanator
Ni-base
Hydrotreater0
Guard Bed
HDN
810,000
66,100
1,180
340
40
880,000
Generation:
3.50
0.96
0.41
0.65
3.01
0.81
1.23
1.64
0.34
0.34
20.5
15.6
1.45
24,000
12,200
170
180
20
40,000
0.25
0.18
0.20
0.17
0.24
0.02
2.8
2.0
3.0
18.5
14.4
52.9
50.0
5.0
7.1
18.8
48.8
26.2
19.5
5.9
13.7
12.8
8
8
4
5
4
-
5
4
3
4
2
2
4
2
4
4
4
2
TOTAL c
26.9
5.1
19.0
A-3
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Table A-l (Continued)
Type of
Waste
Mean Quantity of
Waste Produced Standard Deviation
(metric tons/ (metric tons/
million metric million metric Percent
tons of shale tons of shale Uncertainty3
mined) mined) (%)
Data
Points
(N)
Gas Cleanup Processes:
Activated Alumina 1.86 0.90 48.4
Co -Mo
A1203
DEA
Stretford
Chemicals
TOTAL0
FGD Sludges
Water Treatment
Biological
SI udges
Sludges
& Floats
Tank Bottom
(WWT) Sludges
API Separator
Bottoms
API Float
Raw Water
Treatment
0.11
0.13
0.60
1.87 0.58 31.0
2.06 0.54 26.4
2,250 1,500 66.0
Sludges and Slurries:
545
6,900
150
20 -
2 -
72 -
3
2
2
1
3
6
3
3
1
2
2
1
1
Sludges & Floats
a Percent uncertainty is the relative standard deviation.
b Included in this total are 2340 million metric tons of solid wastes not
broken out separately above.
c Quantities in subcategories do not equal the total for these categories. These
discrepancies result from the small data base, differing information from
various projects, and uncertainty since these plants have not yet been operated.
For a full explanation, see Heistand 1985.
Source: Heistand 1985
A-4
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Because planned gas cleanup operations are more diverse and less well
defined than oil upgrading, the amounts of chemicals used (activated alumina,
Co-Mo, A^Og, DEA, and Stretford chemicals) and flue gas desulfurization
(FGD) sludges from gas cleanup processes are more difficult to estimate, and a
solid statistical analysis of the mean factors listed in Table A-l is not
feasible. Information on chemicals other than activated alumina and the
Stretford chemicals is incomplete, and several projects plan to use more than
one of the gas cleanup chemicals listed. The estimated total of used
chemicals generated from fuel gas cleanup is about 2.1 metric tons per million
metric tons of oil shale mined. While FGD has been suggested as an
alternative to fuel gas cleanup processes, the amounts of FGD chemicals such
as calcium sulfate or gypsum are quite high, with mean quantities projected to
be 2,250 metric tons per million metric tons of shale (Heistand 1985).
Sludges and slurries will be generated in raw and wastewater treatment in
commercial oil shale facilities. Because the exact composition and amounts of
the wastewaters requiring treatment are not well defined and many of the
resulting materials may be used on site, only limited information is available
for estimating the volume of water treatment sludges and slurries (Heistand
1985). The dry weights of these wastes are listed in Table A-l.
A.2 POTENTIAL DANGERS TO HUMAN HEALTH
AND THE ENVIRONMENT
Oil shale facilities will produce large volumes of solid wastes that have
only a limited reuse potential. In some cases, spent catalysts may be
reclaimed and recycled back into the process. Elemental sulfur, which can be
removed by some air pollution control technologies, has some market potential
A-5
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although the presence of trace impurities may constrain its use. Hazardous
wastes such as some spent catalysts and sludges will be disposed of in
licensed hazardous waste facilities.
The catalyst that is of particular concern in oil shale upgrading is the
arsenic guard bed catalyst. Raw shale oil contains significant amounts of
arsenic (15 ppm range) that must be removed prior to upgrading and refining.
Arsenic is removed by the arsenic guard bed catalyst, which must be replaced
periodically and reclaimed or disposed. However, no facilities currently
exist to reclaim the catalyst, and environmentally safe disposal of this spent
catalyst, which may contain 20 percent arsenic as well as other contaminants,
and be pyrophoric (tend to autoignite), may be difficult. As noted in
Table A-l, approximately 15 metric tons of spent arsenic guard bed catalyst
will be produced for each million metric tons of shale mined.
Other dangers to human health and the environment posed by oil shale
mining and processing may result from the long-term effects of the onsite
disposal of millions of tons of retorted oil shale, raw oil shale waste, and
other process wastes. These hazards include the following:
• Auto-oxi dati on/autoi gni ti on
• Leaching
• Mass failure.
A.2.1 Auto-oxidation/Autoigm'tion
Auto-oxidation resulting in autoignition may be a serious problem if raw
shale fines and/or carbonaceous spent shales are not disposed of in a manner
that minimizes this hazard. If oil shale disposal sites are not properly
designed they could autoignite, releasing large quantities of pollutants such
S02, NO , H2S, C02, trace elements, and hydrocarbons. Combustion
A-6
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could also impair pile stability, resulting in disposal pile failure and/or
acceleration of the leaching process. EPA has recently conducted tests to
assess the potential for autoignition of waste raw oil shale fines and
retorted oil shales (EPA 1984). The results of these tests indicate that raw
shale fines have an autoignition potential similar to that of bituminous
coals, while retorted shales appear to be less reactive.
A.2.2 Leaching
High inorganic salt loading and possible organics in leachates from raw
shale fines or spent shale could have potentially significant impacts on
ground-water supplies and on surface waters that supply the water needs of
millions of people. Because the composition of retorted oil shales varies
based on the properties of the raw shale feed and the retorting process used,
the composition of any leachates from retorted shale disposal sites will vary
depending on the properties of the retorted shale and on other wastes disposed
of with the retorted shale, such as wastewaters for cooling/wetting and
treatment sludges.
The available data indicate that even if raw and retorted shale wastes are
not defined as hazardous under RCRA, the leachates from these wastes are high
in dissolved salts as well as other contaminants and could have a serious
impact on surface and ground water if significant amounts of leachate are
produced. The amount of leachate produced will depend to a large extent on
site-specific characteristics and the disposal controls employed. Because
billions of tons of retorted oil shale may eventually be produced, the
cumulative impact on water quality could be very great.
A.2.3 Mass Failure
Retorted oil shale disposal sites will be the largest solid waste disposal
sites ever constructed. A typical 50,000 bbl/day surface retorting plant will
A-7
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produce about 450 million cubic feet/year of solid waste, which would cover an
area of about 3.5 square miles to a depth of 150 feet over an operating plant
life of 30 years (USEPA 1980). Mass failure of one of these fills could cause
extensive property damage and threaten lives. Failure of even one of the
several disposal piles proposed could destroy downstream reservoirs; threaten
shale oil upgrading, storage, and loading facilities; and deposit millions of
tons of leachable retorted shale in the Colorado River and/or its tributaries.
The most likely cause of a disposal site failure is saturation of the
waste pile and/or liquefaction of the pile bottom leading to slippage.
Moisture that could contribute to this problem might result from wastewaters,
precipitation and infiltration, ground-water intrusion into the pile, or
surface streams routed over or through the disposal site.
A.3 DISPOSAL ALTERNATIVES
A.3.1 Alternatives for Minimizing Environmental Impacts
Oil shale operations will result in significant land disturbances on and
near the development site. Use of the land required for access to the site
for mining, processing facilities, and waste disposal will permanently modify
the terrain and influence the ecosystem by causing changes in the vegetation
and habitat. Local aesthetics will also be affected.
The most significant impacts on the environment will probably result from
the disposal of solid shale wastes, which will remain long after a mine has
been depleted and the processing facility has closed down. A major factor to
consider in solid waste disposal is the surface- and ground-water regime of
the site. While a waste landfill should blend in cosmetically with the
surroundings, it must also be sufficiently isolated from the surrounding
A-8
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strata to protect the hydrologic environment. Other factors that influence
waste disposal and may contribute to the extent of environmental impacts are
the size and duration of the oil shale operation and the mining and retorting
technologies used. Because a substantial amount of raw shale will need to be
mined and processed to produce oil, the processed shale will be the major
waste produced by oil shale processing and its disposal will be the primary
environmental issue.
The physical and chemical properties of the processed shale as well as the
geology and hydrology of the site will be the determining factors in selecting
disposal and reclamation approaches. Every retorting method produces shale
that is unique and every development site has features not found elsewhere,
and therefore their combination should be analyzed on an individual basis.
The physical and chemical characteristics of the processed shale will be
determined by the source of the raw shale, its particle size after crushing
and retorting, and the temperature of the retorting.
There are primarily two types of processed shale—carbonaceous and burned
(decarbonized). Carbonaceous processed shales are produced by indirect
retorting in which residual coke on the retorted material is not incinerated.
Examples of this type of retorting are the TOSCO II and Union B processes.
Burned shales originate either from direct-heat processes, such as Paraho and
Modified in Situ (MIS), in which the air is introduced in the retort to cause
combustion of the residual carbon or from combination-mode processes, such as
Lurgi, Superior, and Union C, in which the retorting primarily occurs in the
indirect mode, but the residual coke on the procesed shale is incinerated in a
separate stage.
A-9
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The mining and processing of oil shale actually result in an increase in
the volume of shale. In-place density of the raw shale is approximately 2.16
3
g/cm , but it is only practical to compact the processed shale to about 1.5
to 1.6 g/cm . Even after losing about 20 percent of its original weight,
the shale after retorting will occupy about 10 to 15 percent more volume than
it originally occupied. This will be an important factor when considering
different approaches for the disposal of processed shale.
Processed shale moisturizing will be essential in disposing of the
processed shale and will serve several functions. The processed shale will
emerge from most retorts at elevated temperatures, requiring cooling and/or
moisturizing prior to handling and disposal. Transporting the processed shale
to the disposal area will involve extensive materials handling and transfer
that will be potential sources of airborne particulates, and these particulate
emissions can be minimized by moisturizing and using covered transport.
Perhaps the most significant advantage to moisturizing is that it facilitates
proper compaction and cementing of the processed shale, which will allow the
disposal of the maximum quantity of material in a given space and will provide
greater stability to a waste landfill.
Several alternatives are available for the disposal of shale processing
wastes. The disposal approaches available are surface disposal (canyon or
valley fill, surface pile), open pit backfill, underground mine backfill, in
situ retort abandonment, and, the least likely, commercial utilization of
wastes. The approaches or combinations of approaches used will depend largely
on site-specific features, the mining and retorting methods used, the surface
and subsurface hydrology of the area, and the properties of the processed
shale resulting from the retorting methods used. These disposal alternatives
are discussed in the following paragraphs.
A-10
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A.3.2 Surface Landfills
The disposal of wastes in a valley or canyon near the plant site may be
the approach preferred by many oil shale developers. This selection is
influenced by the terrain of oil shale areas where large valleys and/or
canyons are available on development sites to accommodate the wastes
generated. Proper reclamation can allow for the landfill to be blended into
the surrounding terrain.
The advantages of this type of landfill are that the surface area needing
to be reclaimed or revegetated would be reduced and the bulk of the material
would be protected from the weather. However, water contamination resulting
from run-on and runoff and mechanical failure resulting from mass movement and
slippage are two disadvantages of this method that must be considered. If the
disposal area is flat, the landfill will need to be built above the surface as
a pile, in which case it will not blend into the surrounding environment and
will be visible from a distance. Although surface waste piles may limit
run-on and runoff problems, pile-up operations are more difficult and involve
more skill than valley fill operations, and exposure of landfills to wind and
water may result in excessive erosion.
The disadvantages of surface landfills as a disposal alternative can be
summarized as follows:
t Exposure to rain, snow, and wind may result in erosion of the waste
pile and mechanical failure.
• Waste particles disturbed by weather may become airborne or be
carried into surface- or ground-water supplies in runoff from the
waste pile.
• Surface landfills may not blend into the surrounding terrain.
A-ll
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A.3.3 Open Pit Backfilling
Open pit backfilling is a type of surface landfill that may be an
alternative for open pit mining operations. Backfilling requires that the
overburden, sub-ore, and processing wastes generated during the first 20-30
years be temporarily stored or permanently disposed of in another location so
that they do not inhibit mining operations. Once the mine pit has been
sufficiently developed, the waste can be disposed of in the non-active pit
areas while mining continues on the active faces. After the project is shut
down, some of the initial waste stored outside the pit can be returned to the
mine, but approximately 20-30 percent of the total mined-out volume would
still need to be permanently disposed of outside the pit.
The advantages of open pit mining and backfilling are that they allow for
greater resource recovery than underground methods and the erosion potential
is greatly reduced because the bulk of the material will not be exposed to the
weather. In addition, if backfilling is complete, the land can be brought
back to its original contour. The disadvantages of open pit backfilling
include the following:
• Additional disposal is required outside the open pit.
• A depression in the land surface may result from compaction and
settling of materials backfilled into the pit, allowing water
collection and possible waste pile infiltration.
t Ground water may be contaminated, particularly if the pit intersects
an existing aquifer.
A.3.4 Underground Mine Backfilling
Returning the processed shale to the underground mine is an attractive
disposal approach and several underground backfilling methods are available,
A-12
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although none has been tested on a large scale. Slurry backfilling via
pipelines is practical for processed shale disposal but requires large amounts
of water. Transportation by conveyors or trucks and subsequent compaction
using standard machinery is another method. Pneumatic transport is also a
possibility.
The advantages of using underground mine backfilling are that the waste
would be protected from the weather, erosion potential would be diminished,
and the need for surface reclamation and revegetation would be reduced. Also,
the danger of mine subsidence would be significantly reduced.
The disadvantages inherent in this disposal alternative include the
following:
• The logistics of simultaneous mining and backfilling operations may
be complex, requiring substantial above-ground disposal capacity
before backfilling can commence.
• Because of the difficulties in backfilling, coupled with the
expansion volume caused by mining, crushing, and retorting and
difficulty in achieving a high degree of compaction in underground
mines, perhaps only 60 percent of all processed shale can be
accommodated.
• Release of volatiles from retorted and backfilled shales may create a
fire hazard or otherwise endanger workers.
A.3.5 In-Situ Retort Abandonment
Although in-situ retorting processes do not involve surface handling and
disposal of processed shale, the retorted mass underground is waste that must
be managed. Although spent retorts may appear in some ways to be equivalent
to backfilled wastes in underground mines, there are important differences.
A-13
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With in-situ retorts, it is not possible to control the amount and placement
of material, and the extent of ground-water seepage into the retort cannot be
determined or managed until after the retort field is abandoned and
ground-water levels are no longer depressed.
The primary concerns associated with the abandonment of in-situ retorts
are ground-water infiltration, the retention of heat in the retorted mass, and
the creation of a combustion hazard caused by air leaking into the retort.
A.3.6 Potential Utilization of Wastes
Retorted oil shale, particularly decarbonized shales, raw shale fines,
spent catalysts, elemental sulfur, and biological treatment sludges may have a
limited potential for use on site. Decarbonized western oil shales have
cementing properties similar to those of low-grade commercial cement and may
be used as a cement substitute. Raw shale rejects and fines from mining and
raw shale preparation could be processed by some types of retorts or formed
into briquettes for processing by other retort facilities. Some spent
catalysts could be reclaimed and reused in the upgrading process, although no
facilities presently exist to reclaim them. Some air pollution control
technologies remove elemental sulfur, which may have a limited market value if
it is not contaminated by impurities. Biological treatment sludges may be
useful on site as soil conditioners for revegetation if they do not contain
significant quantities of harmful contaminants.
Unfortunately, even if each of these wastes is used to the maximum extent
possible, it will not have a significant impact on the total amount of solid
oil shale waste requiring disposal.
A-14
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A.4 CONTROL TECHNOLOGIES
The following discussion of the control technologies applicable for oil
shale waste disposal is derived from EPA's Pollution Control Technical Manual
(1983) for TOSCO II oil shale retorting and summarizes the major control
technologies for preventing contamination of surface- and ground-water
supplies by runoff or leachate, for preventing the generation of dusts, and
for preventing mass failure of a surface landfill. Selecting and applying the
appropriate control technologies must be based on site- and plant-specific
features, and controls must be integrated into the overall disposal design.
The following sections specify control technologies and practices in the
following areas:
t Surface hydrology
• Subsurface hydrology
• Surface stabilization.
(Control technologies for oil shale wastes are similar to those mitigative
measures specified in Section 3 of this report.)
A.4.1 Surface Hydrology Control Technologies
Solid waste management practices in the area of surface hydrology entail
the handling of surface waters on and around the disposal facility to prevent
surface streams and precipitation from running onto the waste pile and to keep
contaminated waters (runoff, leachate) from infiltrating natural waters.
Surface hydrology control technologies that are applicable to surface
landfills include run-on diversion systems, runoff collection systems, and
runoff/Ieachate collection ponds.
A.4.2 Subsurface Hydrology Control Technologies
The technologies and practices in the area of subsurface hydrology involve
handling ground-water seepage under landfills to prevent infiltration of the
A-15
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pile. These technologies also prevent leachate from the pile from
contaminating ground water. These include liners and covers, leachate
collection systems, and ground-water collection systems.
A.4.3 Surface Stabilization Technologies
Control technologies in the area of surface stabilization address the
disturbed land surface and the problems associated with the disposal and
reclamation of waste material. They include dust controls, such as the use of
water and binders and the paving of haul roads, and erosion controls, such as
mulching, revegetation, and designs that provide slope stability.
A. 5 CONCLUSIONS
The oil shale industry will produce unprecedented volumes of solid waste
consisting primarily of retorted oil shales, raw oil shale fines, overburden
and subgrade ore, wastewater, and smaller quantities of known hazardous
wastes. Although most known hazardous wastes will be disposed of in licensed
disposal or recycling facilities, a majority of the solid wastes produced will
be disposed of on or close to the plant site. If this large volume of wastes
is not properly managed, it may produce leachates that could contaminate the
water supplies of millions of people, pose an autoignition hazard, and, if a
mass failure occurred, do extensive property damage and threaten lives.
Control technologies to prevent serious adverse impacts resulting from the
disposal of billions of tons of oil shale wastes have been proposed, but their
application to oil shale wastes on the scale required has not been
demonstrated. Further, for these technologies to be effective they must be
incorporated into highly technical and well-integrated disposal designs that
A-16
-------
are both site- and process-specific. Finally, there has been no experience in
disposing of wastes having the characteristics and volume of those that will
be generated by the oil shale industry.
A-17
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REFERENCES FOR APPENDIX A
Heistand, R.N. 1985. "Estimating Solid Wastes from Oil Shale Facilities,"
Proceedings of the 18th Oil Shale Symposium. Golden, Colorado: Colorado
School of Mines Press.
USEPA. 1984. Auto-oxidation Potential of Raw and Retorted Oil Shale.
EPA-600/2-84-153. A.D. Green, Editor, Research Triangle Institute.
Cincinnati, OH: U.S. Environmental Protection Agency.
USEPA. 1983. Pollution Control Technical Manual: TOSCO II Oil Shale
Retorting with Underground Mining. EPA-600/8-83-003. Cincinnati, OH:
U.S. Environmental Protection Agency.
USEPA. 1980. Environmental Perspective on the Emerging Oil Shale Industry.
EPA-600/2-8-205a. EPA Oil Shale Research group. E.R. Bates and T.L. Thoem,
Editors. Cincinnati, OH: U.S. Environmental Protection Agency.
A-18
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APPENDIX B
METHODOLOGY
-------
APPENDIX B
METHODOLOGY
The most important empirical input for this study was derived from
analyses of sampling results and information about active mines in the
industry segments of concern. EPA's sampling methodology (described more
fully in Section 4.1) involved sampling waste from at least one mine and mill
in various mining region-commodity categories. These results were
supplemented by sampling results from other studies so that EPA's waste
samples would represent the full range of wastes and industries covered by
this study. EPA's data base containing information about active mines in the
industry segments of concern is described below. The Agency's methodology
relied on contractor studies, EPA staff analyses, field and laboratory
results, engineering estimates, and economic projections and trends. This
appendix first describes EPA's data base, and then discusses how the Agency
determined current industry control practices, estimated the amounts of waste
involved, and extrapolated from waste volumes at individual mines to totals
for all mining industry segments.
B.I EPA'S DATA BASE
EPA compiled a data base of mines in the following industry segments as
follows:
• Copper—I3 mines;
• Gold—11 mines;
• Lead--? mines;
B-l
-------
• Silver--9 mines;
• Uranium~9 mines;
t Zinc--7 mines; and
• Phosphate--!8 mines.
EPA had the following information about these mines:
• Name and location;
• Amount of product produced annually;
• Amounts and types of wastes existing on site and the amounts
generated annually;
• Expected operating life of the mine; and
• Dimensions of waste management areas (e.g., area and perimeter of
mine waste piles; depths, surface areas, height and width of berms of
tailings impoundments; area and perimeter of heap/dump leach
operations, etc.).
B.2 CURRENT INDUSTRY BASELINE PRACTICES
FOR THE USE OF MITIGATIVE MEASURES
EPA assessed current industry baseline practices for the use of various
mitigative measures as follows. The Agency assumed that mines located in
states having regulations as stringent as RCRA requiring mines to have
mitigative measures (e.g., ground-water monitoring, run-on/runoff controls,
liners for tailings ponds, leachate collection and removal, pads for heap
leach operations) currently used the required mitigative measures. In the
case of closure, EPA assessed whether mine sites perform some or all of the
procedures currently required by RCRA. Mines in states that do not have
regulations requiring a certain mitigative measure, or requiring measures that
are not as stringent as current RCRA requirements, were assumed not to be
using a measure unless the Agency had specific knowledge that a measure was
voluntarily being used at a specific mine in that state.
B-2
-------
These assumptions were used to estimate the percentage of mines in various
industry segments where sufficiently stringent mitigative measures are
currently being used (see Section 3 of this report), and to determine baseline
industry practices for the analysis of the economic costs of various
regulatory scenarios (presented in Section 5 of this report).
8.3 ESTIMATED AMOUNTS OF POTENTIALLY HAZARDOUS MINING WASTE
EPA estimated the amount of potentially hazardous mining waste by type of
hazard, industry segment, and type of waste (mine waste, tailings, leach
waste) using EPA's waste sampling results (presented in Section 4.1),
site-by-site estimates of the amount of mining waste at operations at sites
represented in the data base described above, and estimates of the total
amount of waste generated by each mining industry segment.
EPA's first step in estimating the annual generation of potentially
hazardous mining waste was to project the number of mines active in 1985, the
amount of waste generated annually, and the amount of waste existing at these
mine sites in 1985. Because of the variability in the number of active mines
in recent years, EPA projected past trends to arrive at 1985 estimates instead
of using historical data from the most recent year for which such data were
available. These projections are based on an extrapolation of mineral produc-
tion levels and a review of the current operating status of mines, amounts of
waste generated, and the amount of existing waste at the mines represented in
the EPA data base. (These projections are presented in Table 4-17 of the
report.)
B-3
-------
EPA developed estimates of the amounts of specific mining wastes that may
be potential candidates for listing (copper dump leach wastes, silver and gold
heap leach wastes, silver and gold metal recovery wastes) based on annual
generation data for each of these wastes. EPA estimated the amounts of waste
that are hazardous because of their characteristics (i.e., corrosivity, EP
toxicity, cyanide content, radioactivity, asbestos content, acid formation
potential) based on the waste sampling and acid formation potential data for
waste management operations represented in EPA's data base.
For sampled mines represented in the EPA data base, Table B-l shows the
percentage of all U.S. mining waste management operations and of all wastes
generated by these operations in 1985, by industry segment. As this table
shows, the data base used by EPA as the basis for this report on hazardous
mining waste represents a considerable portion of the total number of mining
waste operations and of all mining waste generated by these industry segments:
t For mine waste operations, the data base represents between 5 (gold
industry) and 43 (lead industry) percent of all mine waste operations
in each of the respective segments.
t For heap/dump leach operations, the data base represents between 17
percent (gold and silver industry segments), and 32 percent (copper
industry) of all such operations in each of the respective segments.
• For tailings operations, the data base represents between 6 percent
(gold industry) and 67 percent (copper industry) of all tailings
operations.
In all cases, the percentage of waste represented in the data base is
larger than the percentage of operations. For example, in the copper industry
segment, 93 percent of all copper tailings waste but 67 percent of all copper
B-4
-------
Table B-l Percentage of Mines and Annual Amount of Waste Generated by
Sampled Mines Represented In EPA's Data Base
Mining
industry
segment
Type of waste
management
operation
Percentage of
all mining waste
management operations
in industry segment
(1985)
Percentage of
annual mining waste
generated by
industry segment in
1985
Copper
Gold
Lead
Mine waste
Dump leach
Tailings
Mine waste
Heap leach
Tailings
Mine waste
Tailings
Phosphate Mine waste
Tailings
Silver
Mine waste
Heap leach
Tailings
Uranium Mine waste
Zinc
Mine waste
Tailings
32
32
67
5
17
6
43
50
21
21
10
17
11
14
33
33
73
38
93
35
53
34
56
60
45
34
57
53
73
26
69
70
Source: Charles River Associates 1985c.
B-5
-------
tailings operations are represented in the data base. Although only 26
percent of all of the mine waste generated annually by the uranium segment is
reflected in the data base, the data base generally reflects at least half of
the total amount of waste generated by the waste management operations of each
of the respective industry segments.
To provide estimates of the maximum amount of potentially hazardous waste
generated by the mining industry segments of concern, EPA assumed that if any
waste sample from a waste management operation failed a particular hazard
criterion, all of the waste from that operation failed that hazard criterion.
For example, if one of five samples from a tailings pond was EP toxic, EPA
assumed that all waste from that tailings operation was EP toxic. Similarly,
if a sample of pregnant leachate from a dump leach pile had a pH of less than
or equal to 2, waste from the entire dump leach operation was considered
corrosive.
Table B-2 shows the number of sampled waste management operations
represented in the EPA data base that had at least one sample that was
classified as hazardous. It also shows how many of these waste management
operations had at least one sample classified as hazardous because it was EP
toxic, corrosive, radioactive, or had high acid formation potential.
To estimate the total amount of potentially hazardous waste generated
annually, EPA extrapolated results from the sampled wastes represented in the
EPA data base to wastes generated by mines included in the data base and to
wastes generated by mines included in the data base but not sampled by EPA.
For mines not sampled by EPA but represented in the EPA data base, EPA
estimated the amount of potentially hazardous waste generated annually as
follows. The annual amount of waste generated at operations at these mines,
B-6
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Table B-2 Number of Sampled Waste Management Operations Represented in EPA's
Data Base with at Least One Sample Classified as Hazardous
Mining
industry
segment
Copper
Mine waste
Dump leach waste
Ta i 1 i ngs
Gold
Mine waste
Heap leach waste
Tailings
Lead
Mine waste
Tai 1 i ngs
Phosphate
Mine waste
Tailings
Silver
Mine waste
Heap leach waste
Tailings
Uranium
Mine waste
Zinc
Mine waste
Tailings
Number of
hazardous
waste
management
operations
7
3
12
6
5
4
3
3
7
7
5
1
5
6
4
4
EP toxic
0
0
0
1
0
2
1
1
0
0
1
0
1
0
0
1
Corrosive
0
1
0
0
0
0
0
0
0
0
0
0
0
0
0
0
High acid
formation
potential
0
0
4
0
0
0
0
0
0
0
0
0
1
0
0
0
Radium-226
greater than
or equal to
5 pCi/g
0
0
0
0
0
0
0
0
5
4
0
0
0
6
0
0
Radium-226
greater than
or equal to
20 pCi/g
0
0
0
0
0
0
0
0
0
1
0
0
0
5
0
0
Source: EPA sampling results and EPA data base.
-------
as reported in the data base, was multiplied by the percentage of sampled
operations reported in the data base as having potentially hazardous waste.
To estimate the amount of potentially hazardous waste generated annually by
those mining operations not represented in the data base, EPA multiplied the
percentage of waste found to be potentially hazardous at mines represented in
the data base by the estimated amount of waste generated by the mines that
were not represented in the data base. Table B-3 illustrates EPA's
methodology for estimating the total amount of potentially hazardous mining
waste generated annually.
One limitation of this approach is that not all of EPA's sampling data
could be used in the projections of the total amount of potentially hazardous
waste, i.e., only data for waste operations represented in the EPA data base
were used to estimate projected amounts of waste. EPA recognizes that use of
this methodology may overlook some data. For example, if EPA had sampling
results showing that a sample taken from an operation that was not represented
in the data base had a hazardous level of one of the properties considered
hazardous in this report, no waste from such an operation in that industry
segment was classified as having that property. To illustrate, one sample
taken by EPA at a copper waste operation was EP toxic, but because this
particular operation was not represented in the EPA data base, no waste from
this industry segment is reported here to be EP toxic. A similar problem
occurs with respect to the acid formation potential of wastes in the gold and
silver industry segments; the analysis of minerals for these industry segments
shows that a significant percentage of these tailings have high acid formation
potential. However, since none of these tailings operations were located at
mines represented in the EPA data base, no tailings from these segments are
B-8
-------
Table B-3 Methodology for Estimating the Total Amount
of Potentially Hazardous Mining Waste Generated Annually
Source of data
Method for determining
amount of waste
Method for determining
percentage of potentially
hazardous waste
Sampled sites
represented in
EPA's data base
Site-by-site estimates
for sites represented
in EPA's data base
Sampling results
Non-sampled sites
represented in
EPA's data base
Sites not
sampled and not
represented in
EPA's data base
Site-by-site estimates
for sites represented
in EPA's data base
Total amount of mining
waste based on Bureau
of Mines estimates
minus amount of mining
waste represented in
EPA's data base
Percentage of all sites
found to have hazardous
waste
Extrapolation based on
relative amount of waste
found to be hazardous in
mines represented in
EPA's data base
B-9
-------
considered potentially hazardous because of their high acid formation
potential. Despite these anomalies, EPA decided to base its estimates on data
from the sampled operations represented in EPA's data base because complete
sampling data and estimates of the amount of waste generated annually were
available only for these operations. In addition, EPA's data base only
included information on mines that were active in 1985.
B-10
-------
APPENDIX C
SELECTED CRITERIA
ANALYZED FOR TOXIC EFFECTS
-------
TABLE C-l
A COMPARISON OF LEVELS OF EP TOXIC METALS ALLOWED
BY VARIOUS EPA STANDARDS AND CRITERIA
Metals Measured
by RCRA's EP
Toxldty Test
Levels Specified
by 40 CFR 261.24,
Characteristic of
EP Toxldty, mg/1
Maximum Contaminant
Levels Specified
by 40 CFR 141.11,
National Interim
Primary Drinking
Water Standards,
mg/1
Levels Specified by
45 FR 79318, Nov. 20,
1980 Ambient Water
Quality Criteria for
the Protection of
Aquatic Life, mg/1
(24-hour average)
Arsenic
Barium
Cadmium
Chromium (VI)
Lead
Mercury
Selenium
Silver
5.0
100.0
1.0
5.0
5.0
0.2
1.0
5.0
.05
1.0
.01
.05
.05
.002
.01
.05
NA
NA
.000025
.00029
.0038
.0002
0.035
NA
NA - Not Applicable
C-l
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TABLE C-2
ARSENIC TOXICITY TO AQUATIC BIOTA
Toxic
Effect
Most Sensitive
Organism Tested
Toxic
Concentration,
mg/1
Source
Acute toxicity
Cladocera
Simocephalus
serruiatus
0.812 As
+3
US EPA (1980a)
Daphm'a magna
Minnows
Chronic toxicity Algae
Daphm'a magna
7.4 As
+5
27-45 As
+3
+3
2.32 As
0.91 As+3
0.52 Total As
US EPA (1980a)
McKee and Wolf
(1963)
US EPA (1980a)
US EPA (1980a)
NRCC (1980)
Bass
7.6
McKee and Wolf
(1963)
a The terms LC50 and EC50 refer to contaminant concentrations lethal (LC50)
or causing significant toxic effects (EC50) to 50 percent of a test
population within a selected test duration.
b 100% kill in 2 weeks.
C-2
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TABLE C-3
CADMIUM TOXICITY TO AQUATIC BIOTA
Toxic
Effect
Most Sensitive
Organism Tested
Toxic
Concentration
(mg/1 x 10-3)
Source
Acute toxicity
(LC50/EC50)a
Cladoceran
Simocephalus
serrulatus
3.5-35
US EPA (1980b)
Striped bass
larvae
1.0
US EPA (1980b)
Chronic toxicity
Diatoms
Asterionell a
formosa
2.0
US EPA (1980b)
Daphnia pulex
1.0
US EPA (1980b)
Rainbow trout
Brook trout
0.7-130
1.0
US EPA (1980b)
NRCC (1979a)
The terms LC50 and EC50 refer to contaminant concentrations lethal (LC50)
or causing significant toxic effects (EC50) to 50 percent of a test
population within a selected test duration.
C-3
-------
TABLE C-4
CHROMIUM TOXICITY TO AQUATIC BIOTA
Toxic
Effect
Acute toxicity
(LC5Q/EC50)a
Most Sensitive
Organism Tested
(freshwater)
Algae
Mate rmil foil
Scud
Daphnia magna
Toxic
Concentration Level
(mg/1 )
Cr VI Cr III
0.01-0.50
9.9
0.067 3.1
6.4 2.0-59
Source
US EPA (1980c)
US EPA (1980c)
US EPA (1980c)
US EPA (1980c)
0.016-0.7 0.33
NRCC (1980)
Fathead minnow 17.6-66 5.0-67 US EPA (1980c)
Benthic organisms
3.0-60 NRCC (1980)
Chronic toxicity
Daphnia magna
0.066 US EPA (1980c)
Rainbow trout 0.073-0.265
US EPA (1980c)
Fathead minnow
1.02
US EPA (1980c)
The terms LC50 and EC50 refer to contaminant concentrations lethal (LC50)
or causing significant toxic effects (EC50) to 50 percent of a test
population within a selected test duration.
C-4
-------
Chronic toxicity
TABLE C-5
LEAD TOXICITY TO AQUATIC BIOTA
Toxi c
Effect
Acute toxicity
(LC50/EC50)a
Most Sensitive
Organism Tested
Algae
Invertebrates
(scud)
Daphnia magna
Sticklebacks
and trout
Fathead minnow
Toxic
Concentration
Level (mg/1 )
0.3-30
0.5-1.0
0.124
0.45-1.91
0.30
2.4-482
Hardness
(mg/1 Cs
CaC03)
46
45-152
soft
20-360
Source
NRCC (1979)
US EPA (1980d)
US EPA (1980d)
US EPA (1980d)
NRCC (1979)
US EPA (1980d)
Algae
Daphnia magna
Rainbow trout
0.1-2.0
0.012-0.128 52-151
0.019-0.128 19-128
NRCC (1979)
US EPA (1980d)
US EPA (1980d)
a The terms LC50 and EC50 refer to contaminant concentrations lethal (LC50)
or causing significant toxic effects (EC50) to 50 percent of a test
population within a selected test duration.
C-5
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TABLE C-6
MERCURY TOXICITY TO AQUATIC BIOTA
Toxic Most Sensitive
Effect Organism Tested
Acute toxicity Phytoplankton
Crayf i sh
Rainbow trout
Chronic toxicity Daphnia magna
Toxic
Concentration
mg/la
0.9-60
0.02
155-400
29
1.27-1.87
0.52-1.00
Compound
Mercury
salts
HgCl2
HgCl2
CH3HgCl
HgCl2
CH3HgCl
Source
McKee
(1963)
US EPA
US EPA
US EPA
US EPA
and Wolf
(1980e)
(1980e)
(1980e)
(1980e)
Minnow
0.01
HgN0
McKee and Wolf
(1963)
Algae
1,030*
HgCl
US EPA (1980e)
a
b
Expressed as mercury, not the compound.
The terms LC50 and EC50 refer to contaminant concentrations lethal (LC50)
or causing significant toxic effects (EC50) to 50 percent of a test
population within a selected test duration.
C-6
-------
TABLE C-7
SELENIUM TOXICITY TO AQUATIC BIOTA
Toxi c
Effect
Most Sensitive
Organism Tested
Toxi c
Concentration
mg/1
Selenite (+4) Selenate (+6)
Acute toxicity
Blue-green algae 15-30
Chronic toxicity
Scud
Fathead minnow
Daphnia sp.
Rainbow trout
0.34
0.62-11.3
0.092-0.69
0.088
17-40
0.76
11.8-12.5
Source: US EPA (1980f)
a The terms LC50 and EC50 refer to contaminant concentrations lethal (LC50)
or causing significant toxic effects (EC50) to 50 percent of a test
population within a selected test duration.
C-7
-------
TABLE C-8
CYANIDE TOXICITY TO AQUATIC BIOTA
Toxic Organism Toxic
Effects Tested Concentration
mg/1
Acute toxlclty Daphnia pulex 0.083
-------
TABLE C-9
SUMMARY OF RADIATION EFFECTS
• Radiation has been demonstrated to be carcinogenic, mutagenic, and
teratogenic (US EPA 1984).
• Radium poses a danger to human health because of its property as an
alpha emitter, and because it is concentrated in bone tissue
following absorption into the body (US EPA 1984).
• Chromosome aberrations in human lymphocytes following radiation
exposure by ingestlon of Ra-226 or by inhalation of Rn-222 have been
demonstrated (US EPA 1984).
• An increased incidence of leukemia and osteosarcoma has been observed
in patients who received injections of Ra-224 for medical purposes
(US EPA 1984).
• US EPA (1984) estimated the radionucllde emissions from a reference
underground uranium mine of assumed typical dimensions to be 11,500
Ci/yr as radon-222, 0.02 Ci/yr as uran1um-238, and 3 x 10'4 Ci/yr
as thorium-232. The most important emission was expected to be
radon-222. The lifetime human mortality risk factor for persons
residing within 2000 meters of the sources of these emissions was
estimated to be on the order of 10'2.
• In general, organisms of lower phyla are more resistant to ionizing
radiation than are higher vertebrates (McKee and Wolf 1963).
• Radon, a decay product of radium, poses a danger to human health
because it is an inert (noble) gas that diffuses into buildings where
it builds up (concentrates) in the indoor air. The decay products of
radon may be inhaled and retained in the lung, greatly increasing the
risk of lung cancer.
C-9
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TABLE C-10
EFFECTS OF ASBESTOS EXPOSURE
Chrysotile and amphibole fibers are toxic to the bacteria E. cpli and
£. aureus (NRCC 1980). ~
Mussels and freshwater fish have been shown to take up asbestos
fibers from water and store these in muscle tissue, but the effect on
mortality rates was not determined (NRCC 1980, US EPA 1980h).
The ambient water quality criteria for the protection of human health
developed by US EPA (1980h), assuming the ingestion of 2 liters per
day of contaminated water, are 300,000 fibers per liter (f/1), 30,00
f/1. and 3,000 f/1 for a projected cancer incidence rate of 10-5,
10~6, and 10~7, respectively.
Cytotoxicity of intestinal tissue has been observed following
ingestion of asbestos fibers by rats (US EPA 1980h).
Asbestosis, the noncancerous disease resulting from inhalation of
asbestos fibers, is a chronic, progressive pneumoconiosis (US EPA
1980). The lowest cumulative asbestos respiratory exposure level at
which severe forms of asbestosis have been detected is 25 fibers -
year/cm3 (US EPA 1980i).
The risk of asbestosis rises with increasing asbestos exposure; the
dose-response curve for asbestosis mortality can be qualitatively
described as linear (US EPA 1980i).
Several studies of worker exposure to asbestos have linked asbestos
respiratory exposure to increased rates of pleural and peritoneal
mesothelioma; cancer of the lung, stomach, esophagus, pharynx,
colon-rectum, skin, and kidney; leukemia; and neoplasms of the
digestive organs and peritoneum (US EPA 1980h).
Several dose-response relationships have been established for
asbestos exposure and human mortality from various diseases. Over
50% of the deaths among a group of 17,800 asbestos insulation workers
exposed at levels of 10 to 20 f/cm3 and studied over a 10-year
period could be attributed to asbestos-related diseases. Chronic
exposure at this level was shown to result in death rates from
mesotheliomas from 1.3 to 4 times those of the general U.S.
population of the same age and sex (US EPA 1980h).
Among male asbestos plant workers, respiratory exposure for less than
2 years at asbestos levels of 20 or more f/cm3 resulted in
significantly increased rates of cancer deaths. Females exposed for
the same duration but at the lower levels of 5 to 10 f/cm3
exhibited significant increases in the rates of death from cancers of
the lung and pleura (US EPA 1980h).
C-10
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0 Excess malignant respiratory disease has been reported among asbestos
mine workers exposed to an average air concentration of 0.25 f/cm3
(US EPA 1980h).
• Estimates of human exposure to asbestos for persons living within 30
km of asbestos mines or mills are 0.4 f/cm3 compared with the
average ambient urban exposure of 5 x 10~3 f/cm3 (electron
microscope visible fibers) (Suta and Levine 1979, as cited by Colgley
et al. 1981).
C-ll
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TABLE C-ll
THE SUMMARY OF EFFECTS OF DECREASING pH ON FISH
PH Range Effects
9.0 - 6.5 Harmless to most fish; toxicity of other poisons may
be affected by changes within this range.
6.5 - 6.0 Unlikely to be harmful to fish unless free carbon
dioxide is present in excess of 100 mg/1; egg
hatchability and growth of alevins of brook trout
significantly lower at all pH levels below 6.5.
6.0 - 5.5 Egg production and hatchability of fathead minnow
reduced; reduced egg production and larval survival
of flagfish; roach reproduction may be affected;
unlikely to be harmful to fish unless free carbon
dioxide is present in excess of 20 mg/1.
5.5 - 5.0 Increased hatching time of Atlantic salmon eggs;
mortality of brown trout eggs is high; threshold of
tissue damage for finger!ing brown trout; growth of
flagfish larvae may be reduced; roach reproduction
reduced at least 50 percent; may be harmful to
non-acclimated salmonids if the calcium, sodium, and
chloride concentrations or the temperature is low.
5.0 - 4.5 Harmful to eggs and alevins or larvae of most
salmonids and white sucker, and to adults
particularly in soft water containing low
concentrations of calcium, sodium, and chloride; may
be harmful to carp; roach recruitment impaired; fish
mortalities can be expected.
4.5 - 4.0 Expected to be harmful to salmonids at all stages;
likely to be harmful to tench, bream, roach,
goldfish, carp, fathead minnow, bluegill;
acclimation may increase resistance to these levels.
4.0 - 3.5 Lethal to most fish over extended periods.
3.5 and below Acutely lethal to fish.
Source: Potter et al. 1982
C-12
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TABLE C-12
SUMMARY OF DAMAGES TO AQUATIC ECOSYSTEMS WITH DECREASING pH
pH Range Effects
8.0 - 6.0 Long-term changes of less than 0.5 pH units are
likely to alter the biotic composition of
freshwaters to some degree. The significance of
these slight changes is, however, not great.
A decrease of 0.5 to 1.0 pH units in the range of
8.0 to 6.0 may cause detectable alterations in
conmunity composition. Productivity of competing
organisms will vary. Some species will be
eliminated.
6.0 - 5.5 Decreasing pH will cause a reduction in species
numbers and, among remaining species, significant
alterations in ability to withstand stress.
Reproduction of some salamander species is
impaired.
5.5 - 5.0 Many species will be eliminated, and species
numbers and diversity will be reduced.
Crustacean zooplankton, phy to plank ton,
mamphipods, most mayfly species, and some
stonefly species will begin to drop out. In
contrast, several pH-tolerant invertebrates will
become abundant, especially the air-breathing
forms (e.g., Gyrinidae, Notonectidae, Corixidae),
those with tough cuticles that prevent ion losses
(e.g., Sialis lutaris), and some forms that live
within the sediments (01igochaeta, Chromomidae,
and Tubificidae). Overall, invertebrate biomass
will be greatly reduced.
5.0 - 4.5 Decomposition of organic detritus will be
severely impaired. Autochthonous and
allochthonous debris will accumulate rapidly.
Most fish species are eliminated.
4.5 All of the above changes will be greatly
exacerbated, and most fish will be eliminated.
Source: Potter et al. 1982
C-13
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REFERENCES FOR APPENDIX C
Colgley, D., Krusell, N., Mclnnes, R., Bell, 1981. GCA Corporation.
Lifecycle of asbestos in commercial and industrial use including
estimates of releases to air, water and land. Draft Report.
Washington, DC: U.S. Environmental Protection Agency. Contract
68-02-2607/68-02-3169.
McKee, J.E., Wolf, H.W. 1963. Water Quality Criteria. Sacramento,
CA: The Resources Agency of California, State Water Quality
Control Board. Publication No. 3-A.
NRCC. National Research Council Canada. 1979a. Effects of Cadmium
in the Canadian Environment. Ottawa, Canada: NRCC No. 16743.
NRCC. National Research Council Canada. 1979.b. Effects of Lead
in the Environment-!978. Ottawa, Canada: NRCC No. 16736.
NRCC. National Research Council Canada. 1980. Executive reports.
Effects of Chromium, Alkali Hal ides, Arsenic, Asbestos, Mercury,
Cadmium in the Canadian Environment. Ottawa, Canada: NRCC No.
17585.
Potter, W., Chang Ben K-Y, Adler, D. 1982. The Effects of Air
Pollution and Acid Rain on Fish, Wildlife, and Their Habitats.
Rivers and Streams. Fish and Wildlife Service, U.S. Department
of Interior, FWS 14-16-0009-80-085.
USEPA. 1984. Radionuclides; Background Information; Document for
Final Rules, Vol. 1. Washington, DC: EPA-560/12-80-003.
USEPA. 1980.a. Ambient Water Quality Criteria for Arsenic. U.S.
Environmental Protection Agency. Washington, D.C.
EPA-440/5-80-021.
USEPA. 1980.b. Ambient Water Quality Criteria for Cadmium. U.S.
Environmental Protection Agency. Washington, D.C.
EPA-440/5-80-025.
USEPA. 1980.c. Ambient Water Quality Criteria for Chromium. U.S.
Environmental Protection Agency. Washington, D.C.
EPA-440/5-80-035.
USEPA. 1980.d. Ambient Water Quality Criteria for Lead. U.S.
Environmental Protection Agency. Washington, D.C.
EPA-440/5-80-057.
USEPA. 1980.e. Ambient Water Quality Criteria for Mercury. U.S.
Environmental Protection Agency. Washington, D.C.
EPA-440/5-80-058.
C-14
-------
USEPA. 1980.f. Ambient Water Quality Criteria for Selenium. U.S.
Environmental Protection Agency. Washington, D.C.
EPA-440/5-80-070.
USEPA. 1980.g. Ambient Water Quality Criteria for Cyanides. U.S.
Environmental Protection Agency. Washington, D.C.
EPA-440/5-80-037.
USEPA. 1980h. Ambient Water quality criteria for asbestos.
U.S. Environmental Protection Agency. Washington, D.C.:
EPA-440/5-80-022.
USEPA. 1980i. Support document for proposed rule on friable
asbestos-containing materials in school buildings; health
effects and magnitude of exposure. Washington, DC:
EPA-560/12-80-003.
C-15
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APPENDIX D
GLOSSARY
-------
GLOSSARY
ACID DRAINAGE - drainage from mines and mining wastes that has a pH ranging
from below 2.0 to 4.5; the acidity is caused by the oxidation of sulfides
exposed during mining, which produces sulfuric acid and sulfate salts.
The acid dissolves minerals in the rocks, further degrading the quality of
the drainage water.
ACID FORMATION POTENTIAL - the propensity of exposure and subsequent oxidation
of naturally ocurring metal sulfides (especially iron pyrite) in ores and
mining waste to produce acid. An acid environment greatly increases the
leaching and mobility of toxic waste constituents, including heavy metals.
WAL6AMATION - a method of extracting a precious metal from its ore by
alloying it with mercury.
AQUIFER - a water-bearing bed or structure of permeable rock, sand, or gravel
capable of yielding quantities of water to wells or springs.
BACKFILLING - a waste management practice for mining waste in which the waste
material is immediately used for refilling previously excavated areas.
BELOW-GRADE DISPOSAL - a disposal method for tailings in which the
tailings are placed in an excavated pit so that at closure the entire
deposit is below the level of the original land surface.
BENEFICIATION - the treatment of ore to concentrate its valuable constituents.
BERM - a ledge or shoulder, as along the edge of a paved road.
BIOLOGICAL ACID LEACHING - a waste pretreatment method that may be a feasible
substitute for certain current dump leaching practices. The biological
acid leaching process converts sulfur in the ore to elemental sulfur,
which is potentially saleable and is less hazardous to the environment
than sulfuric acid, the usual dump leach waste constituent.
BLOCK-CAVING - a large production low-cost method of mining, in which the
greater part of the bottom area of a block of ore is undercut, the
supporting pillars are blasted away, and the ore caves downward and is
removed. As the block caves and settles, the cover follows.
COLLECTION TRENCH - a mitigative system used to prevent seepage from reaching
ground waters or surface waters. Also effective in protecting the
integrity of a tailings pond dam.
COLLOID - an extremely fine-grained material of particles having diameters of
TeTs than 0.00024 mm that can be easily suspended in solution.
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CONTAINMENT SYSTEMS - a. mitigative measures that prevent leachate from
entering the ground water and posing a threat to human health and the
environment. These measures include: liners, cutoff walls, interceptor
wells, hydraulic barriers, and grouting; b. a type of run-on/runoff
control that collects onsite stormwater or dike seepage in holding or
evaporation ponds for the treatment necessary for final disposal or to
prepare the waste for recycling.
CUT-AND-FILL UNDERGROUND MINING (cut-and-fill stoping) - a mining method in
which the ore is excavated by making successive flat or inclined slices,
working upward from the level. After each slice is blasted down, all
broken ore is removed and the stope is filled with waste to within a few
feet of the back before the next slice is taken out. During the process,
there is just enough room between the top of the waste pile and the back
of the stope to provide working space.
CUTOFF WALLS - a mitigative measure employed as a containment system to
prevent seepage from contaminating ground water. Walls, collars, or other
structures reduce percolation of water along smooth surfaces or through
porous strata.
DEWATERING - removing water from a mine by pumping or drainage. Water produced
from mine dewatering may be discharged directly or indirectly to a surface
stream, used in the milling process in make-up water, pumped to a tailings
pond, or used on site for dust control, cooling, or drilling fluid.
DIKE STABILIZATION - a mitigative measure that controls liquids. The
structural integrity of the dike or dikes constructed to confine the
wastes is considered, an assessment is made of the ability of the dike
system to withstand additional loads, including the weight of several
layers of a capping system, and construction equipment is used to place
and compact the final cover.
DIVERSION METHODS - a type of run-on/runoff control that prevents offsite
water from entering a waste management site and causing erosion and
flooding.
DREDGING - the various processes by which large floating machines (dredges)
scoop up earth material at the bottom of a body of water, raise it to the
surface, and discharge it into a pipeline or barge, return it into a
pipeline or barge, or return it to the water body after the removal of ore
minerals.
DUMP LEACHING - a beneficiation process in which sub-ore-grade material is
leached by acid to recover copper. The material to be leached is placed
directly on the ground and the leaching may continue for years or decades.
DUMP LEACH WASTE - a large-volume waste that results from the dump leaching
process.
0-2
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ELECTROSTATIC SEPARATION - a process of ore concentration used to separate
minerals on the basis of their conductivity. The ore is charged with high
voltages and the charged particles are dropped onto a conductive rotating
drum. The conductive particles discharge rapidly, are thrown off, and are
then collected. The nonconductive particles keep their charge, adhere to
the drum by electrostatic attraction, and are removed separately.
ELECTROWINNING - recovery of a metal from an ore by means of electrochemical
processes.
FINAL COVER - a mitigative measure which, when properly installed over the
exposed surfaces of a waste impoundment, ensures control of erosion,
fugitive dust, and surface water infiltration; promotes proper drainage;
and creates an area that is esthetically pleasing and amenable to
alternative level uses.
FRESHWATER INJECTION WELLS (freshwater input wells) - a mitigative measure
that contains seepage, in which freshwater (water with less than 0.2
percent salinity) is pumped into wells for pressure maintenance. Used in
the formation of a hydraulic barrier, and most effective under conditions
of subsurface homogeneity.
FROTH FLOTATION - often referred to simply as flotation, this process is the
separation of finely crushed minerals from one another by causing some to
float in a froth and others to sink. Oils and various chemicals are used
to activate, make flotable, or depress the minerals.
GANGUE - the valueless rock or mineral aggregates in an ore, that part of an
ore that is not economically desirable but cannot be avoided in mining.
It is separated from the ore minerals during concentration and is
generated as tailings.
GEOCHEMICAL PROCESSES - processes that control the rate of movement of
contaminants from the soluble liquid phase (seepage) to the solid phase
(soil , geologic material) of the system.
GRAVITY CONCENTRATION - the separation of minerals by a concentration method
operating by virtue of the differences in density of various minerals; the
greater the difference in density between two minerals, the more easily
they can be separated by gravity methods.
GROUND WATER - water found underground in porous rock strata and soils.
GROUT CURTAIN - a mitigative system used to prevent ground-water contamination.
Seepage losses are controlled by grouting the foundation rock of a waste
disposal facility. Used when waste presents a serious pollution hazard to
groundwater.
HALF-LIFE - the time required for a radioactive substance to lose 50 percent
of its activity by decay. Each radionuclide has a unique half-life.
D-3
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HAZARDOUS WASTE - a solid waste, or combination of solid wastes, which, because
of its quantity, concentration, or physical, chemical, or infectious
characteristics, may (1) cause, or significantly contribute to, an
increase in mortality or an increase in serious irreversible, or
incapacitating reversible illness; or (2) pose a substantial present or
potential hazard to human health or the environment when improperly
treated, stored, transported, disposed of, or otherwise managed.
HEAP LEACHING - an extraction process in which ore is leached by cyanide to
recover gold and silver, or by other reagents to recover uranium. The
material to be leached is placed on a pad; the volume of material leached
is smaller than in the dump leaching process. Leaching continues for
months.
HEAP LEACH WASTE - a large-volume waste generated by the heap leaching process.
HYDRAULIC BARRIERS - a mitigative measure used to prevent ground-water contami-
nation. A barrier used in conjunction with interceptor walls is
established downgradient of an embankment to prevent seepage losses
through the foundation of a waste disposal facility.
HYDRAULIC HEAD - the height of a free surface of a body of water above a given
subsurface point.
HYDROGEOLOGIC EVALUATION - a detection and inspection measure used in combi-
nation with ground-water monitoring at a waste disposal or tailings pond
facility to identify potential pathways of leakage and contamination by
ground water; determine whether contamination of ground-water has occurred
and, if so, the extent of contamination. If contamination has occurred,
this evaluation is used to generate data about factors such as the size,
depth, and rate of flow of a contaminated plume to facilitate
implementation of a mitigative strategy.
HYDROLOGIC PROCESSES - geologic phenomena that determine the critical flow
paths and velocities that control the leachate seepage from a waste
disposal area.
INTERCEPTOR WALLS - a mitigative measure used to prevent ground-water
contamination. Interceptor walls installed at points that intersect the
plumes of contaminated seepage control seepage losses through the
foundation of a waste disposal facility.
ISOTOPE (nuclide) - any of two or more species of atoms of a chemical element
with the same atomic number and position in the periodic table and nearly
identical chemical behavior, but with differing atomic mass or mass number
and different physical properties.
LEACHATE - 1) the beneficiation solution (pregnant liquor) obtained from heap
leach and dump leach processes; 2) the liquid resulting from water
percolating through, and dissolving materials in, waste.
D-4
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LEACHATE COLLECTION, REMOVAL, AND TREATMENT SYSTEMS - mitigative measures
used on lined waste piles to prevent the leacnate from building up above
the liner. Leachate collection prevents the buildup of water over the
liner and thus prevents deformation of piles and overflow of the
containment system. Collected waste is treated and disposed of by
treatment methods such as neutralization, precipitation, and flotation.
LINERS - a mitigative measure used to prevent ground-water contamination in
wn~ich synthetic natural clay, or bentonite materials that are compatible
with the wastes are used to seal the bottom of tailings ponds and waste
pi 1 es.
MAGNETIC SCAVENGING (MAGNETIC SEPARATION) - the separation of magnetic
materials from nonmagnetic materials, using a magnet. Magnetic scavenging
is an important process in the beneficiation of iron ores in which the
magnetic mineral is separated from nonmagnetic material; for example,
roasted pyrite from sphalenite.
MILL TAILINGS - the waste rock (gangue) discarded after ore milling. See
tailings.
MINE WASTE - a large-volume waste consisting of the soil or rock generated by
mining operations during the process of gaining access to an ore or
mineral body. The waste includes the overburden from surface mines,
underground mine development rock, and other waste rock.
MINE WASTE PILES - a waste management practice used for mine waste or the area
where mine waste or spoil materials are disposed of or piled.
MINE WATER - a large-volume waste consisting of the water that infiltrates a
mine and is subsequently removed to facilitate mining.
MINE WATER PONDS - impoundments used to hold mine water prior to evaporation,
recycling, or discharge.
NPDES - National Pollutant Discharge Elimination System, EPA's system of
permits for controlling the discharge of water pollutants to surface
waters.
OPEN-CAST MINING - a surface mining method in which the overburden is removed
and minerals are extracted in a series of regular slices called cuts and
the overburden of each subsequent cut is replaced into the void of the
preceding cut. This method is primarily used in the mining of coal.
OPEN-CUT MINING (OPEN-PIT MINING) - a surface mining method involving the
removal of the overburden, and breaking and loading the mineral, as
happens in a stone quarry. This method is primarily used for
metalliferous ores such as iron and copper.
D-5
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OPEN-STOPE MINING - a method of stoping in which no regular artificial method
of support is employed, although occasional props or cribs may be used to
hold local patches of insecure ground. The walls and roof are self-
supporting, and open stopes can be used only where the ore and wall rocks
are firm. This method is usually confined to small ore bodies because the
length of unsupported span that will stand without breaking is limited.
PLACER MINING - a form of mining in which a gravel deposit containing gold is
washed to extract the gold.
POND-SEDIMENT REMOVAL - a mitigative measure used to remove the sediment that
builds up in wastewater retention ponds.
OVERBURDEN - consolidated or unconsolidated material overlying the mined area.
PICOCURIE - a unit of radioactivity defined as 0.037 disintegrations per
second, and abbreviated as pCi.
POTENTIALLY HAZARDOUS WASTES - wastes that have characteristics that may pose
a threat to human health or the environment.
PRECIPITATION - 1) a process of separating mineral constituents from a solution
by means of a reagent; 2) rain, snow, or hail.
QUARRYING - a method of surface mining used for stone or mineral deposits.
This method is primarily used for non-metallic materials such as limestone
and building stone.
RCRA - Resource Conservation and Recovery Act, the legislation under which
EPA regulates hazardous waste.
RCRA SUBTITLE C CHARACTERISTICS - criteria used to determine if an unlisted
waste is a hazardous waste under Subtitle C of RCRA:
- corrosivity - a solid waste is considered corrosive if it is
aqueous and has a pH less than or equal to 2 or greater than or
equal to 12.5 or if it is a liquid and corrodes steel at a rate
greater than 6.35 mm per year at a test temperature of 55°C
- EP toxicity - a solid waste exhibits the characteristic of EP
(extraction procedure) toxicity if, after extraction by a
prescribed EPA method, it yields a metal concentration 100 times
the acceptable concentration limits set forth in EPA's Primary
Drinking Water Standards.
- ignitability - a solid waste exhibits the characteristic of
ignitability if it is a liquid with a flashpoint below 60°C or a
non-liquid capable of causing fires at standard temperature and
pressure.
D-6
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- reactivity - a waste Is considered reactive If It reacts violently,
forms potentially explosive mixtures, or generates toxic fumes
when mixed with water, or if it is normally unstable and
undergoes violent change without deteriorating.
RADIONUCLIDE (radioisotope) - an unstable isotope of an element that decays
or disintegrates spontaneously, emitting radiation.
RADIUM-226 - a radioactive daughter product of the decay of uranium-238.
Radium is present in all uranium-bearing ores; it has a half-life of 1620
years.
RETORTING OF OIL SHALE - the heat-dependent distillation process in which oil
Is extracted from the raw shale.
REVEGETATION - the third step in the final cover procedure of a reclamation
and closure system, revegetation is used during the active operation of
the tailings pond and at closure. Regrading, contouring, and revegetation
of tailings areas prevent erosion, stream turbidity and sedimentation, and
provi de dust control.
RIP-RAP - a foundation or sustaining wall of stones thrown together
irregularly.
ROOM-AND-PILLAR MINING - a method of mining used to mine coal and metal, in
which the roof is supported by pillars left at regular intervals.
RUN-ON/RUNOFF CONTROL - a mitigative measure used to control liquids and
involving diversion methods and runoff acceleration practices.
RUNOFF ACCELERATION PRACTICES - a type of run-on/runoff control that reduces
ground-water pollution by preventing the ponding or percolation of
rainfall on wastepiles.
SECURITY SYSTEMS - a mitigative measure used for the security of control
systems and protection of the public that may include the posting of "No
Trespassing" signs, locked gates, security guards, and fencing.
SEEPAGE COLLECTION SYSTEMS - mitigative measures that control seepage by (1)
restricting seepage outflow, or (2) using drainage methods to discharge
the seepage without the danger of piping of material or buildup of a high
ground-water elevation within the embankment.
SHEEPFOOT ROLLER - an earth compaction machine with a roller of "feet" used to
compact by striking the earth repeatedly.
SLIMES - a material of extremely fine particles encountered in the treatment
of ore. Primary slimes are extremely fine particles derived from ore,
associated rock, or clay. They are usually found in old dumps and in ore
deposits that have been exposed to climatic action; they include clay,
alumina, hydrated iron, near-colloidal common earths, and weathered feld-
spars. Secondary slimes are very finely ground minerals from the true ore.
D-7
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SLURRY WALLS - a seepage collection/blockage mitigative system. Seepage
losses are controlled by grouting the walls of a waste disposal facility
with a slurry compound of cement and water. This system is used when
waste presents a serious pollution hazard to ground water.
SMCRA - Surface Mining Control and Reclamation Act.
SMELTER SLAG - the rough vesicular 1 aval ike waste remaining after the
processing of ore and minerals.
SOLVENT EXTRACTION - a method of separating one or more substances from a
mixture, by treating a solution of the mixture with a solvent that will
dissolve the required substance or substances, leaving the others.
SQUARE-SET STORING - a method of stoping in which the walls and back of the
excavation are supported by regular framed timbers forming a skeleton that
encloses a series of connected, hollow, rectangular prisms in the space
formerly occupied by the excavated ore and providing continuous lines of
support in three directions. The ore is excavated in small, rectangular
blocks just large enough to provide room for standing a set of timber.
This method is most applicable in mining deposits in which the ore is
structurally weak. The primary function of the square sets is to furnish
temporary support only for loose fragments of rock and to offer a
passageway to the working face. Permanent support for the stope walls is
supplied by filling the sets with broken waste rock.
STOPE - an excavation where the ore is drilled, blasted, and removed by
gravity through chutes to ore cars on the haulage level below. Stopes
require timbered openings (manways) to provide access for men and
materials. Raises connect a stope to the level above and are used for
ventilation, convenience in getting men and materials into the stope, and
admitting backfill.
STRIP MINING - mines from which minerals that lie near the surface
are extracted using a cutting technique by which long, shallow cuts are
made in the ground after the removal of overburden. These mines are
primarily used in the mining of coal.
SURFACE WATER - water that rests on the surface of the rocky crust of thex
earth.
SURFACE WATER DIVERSION - this control system consists of canals, channels,
or pipes that totally or partially surround a waste management site or
leaching operation and divert surface water flow around it and back into
the natural system channel downgradient of the waste area. The most
important functions of diversion ditches are to reduce the volume of water
contacting the waste (run-on) and to minimize downstream environmental
damage (runoff).
D-8
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TAILINGS - a large-volume waste consisting of the materials remaining after
th~e"~va1 uable constituents (also termed values) of the ore have been
removed by physical or chemical beneficiation, including crushing,
grinding, sorting, and concentration by a variety of methods.
TAILINGS PONDS - a waste management practice for tailings consisting of
an area closed at the lower end by a constraining wall or dam to which
mill tailings are run. The size and design of the ponds vary widely by
industry segment and location.
TAILINGS SLURRY - the method used to transport tailings from the mill. The
slurry consists of 50 to 70 percent (by weight) liquid mill effluent and
30 to 50 percent solids (clay, silt, and sand-sized particles).
THICKENED DISCHARGE - a disposal method for tailings in which the tailings
slurry is partially dewatered and discharged from a single point. The
result is a gently sloping, cone-shaped deposit.
UMTRCA - Uranium Mill Tailings Radiation Control Act.
UNDERGROUND MINE DEVELOPMENT ROCK - rock removed while sinking shafts or
accessing or exploiting the ore body.
VALUE - the valuable constituents of an ore.
WASTE ROCK - rock that must be broken and disposed of to gain access to and
excavate the ore; valueless rock that must be removed or set aside before
the milling process.
WASTE STABILIZATION - a mitigative measure used to control liquids; proper
consolidation and stabilization of the waste are necessary to ensure
long-term support for the final cover. The first step in stabilization of
tailings is dewatering the wastes. The wastes are then tested to
determine the amount of settlement of the wastes due to compression from
the final cover system and the construction used in applying the cover
system components.
WASTE UTILIZATION - a current mining waste disposal practice that involves:
(1) the extraction of economically valuable amounts of metals or minerals
in the waste, and (2) the use of this waste material for productive
purposes.
WASTEWATER TREATMENT - a mitigative measure used to control liquids. The
wastewater that remains onsite after active mining and milling processes
is treated and then either discharged or transported to a licensed
disposal site.
• U S GOVERNMENT PRINTING OFFICE 1986 618-851/40390
D-9
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