Office of Research and Development
Industrial Environmental Research FP A-fiOD/7-7fi-n'3fi
Laboratory
Cincinnati,Ohio 45268 December 1976
ASSESSMENT OF
ENVIRONMENTAL ASPECTS OF
URANIUM MINING AND MILLING
Interagency
Energy-Environment
Research and Development
Program Report
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RESEARCH REPORTING SERIES
Research reports of the Office of Research and Development, U.S.
Environmental Protection Agency, have been grouped into seven series.
These seven broad categories were established to facilitate further
development and application of environmental technology. Elimination
of traditional grouping was consciously planned to foster technology
transfer and a maximum interface in related fields. The seven series
are:
1. Environmental Health Effects Research
2. Environmental Protection Technology
3. Ecological Research
4. Environmental Monitoring
5. Socioeconomic Environmental Studies
6. Scientific and Technical Assessment Reports (STAR)
7. Interagency Energy-Environment Research and Development
This report has been assigned to the INTERAGENCY ENERGY-ENVIRONMENT
RESEARCH AND DEVELOPMENT series. Reports in this series result from
the effort funded under the 17-agency Federal Energy/Environment
Research and Development Program. These studies relate to EPA's
mission to protect the public health and welfare from adverse effects
of pollutants associated with energy systems. The goal of the Program
is to assure the rapid development of domestic energy supplies in an
environmentally—compatible manner by providing the necessary
environmental data and control technology. Investigations include
analyses of the transport of energy-related pollutants and their health
and ecological effects; assessments of, and development of, control
technologies for energy systems; and integrated assessments of a wide
range of energy-related environmental issues.
This document is available to the public through the National Technical
Information Service, Springfield, Virginia 22161.
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EPA-600/7-76-036
December 1976
ASSESSMENT OF ENVIRONMENTAL ASPECTS
OF URANIUM MINING AND MILLING
by
A. K. Reed, H. C. Meeks, S. E. Pomeroy,
and V. Q. Hale
Battelle
Columbus Laboratories
Columbus, Ohio 43201
Contract No. 68-02-1323
Task 51
Project Officer
Elmore C. Grim
Resource Extraction and Handling Division
Industrial Environmental Research Laboratory
Cincinnati, Ohio 45268
INDUSTRIAL ENVIRONMENTAL RESEARCH LABORATORY
OFFICE OF RESEARCH AND DEVELOPMENT
U.S. ENVIRONMENTAL PROTECTION AGENCY
CINCINNATI, OHIO 45268
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DISCLAIMER
This report has been reviewed by the Industrial Environmental Research
Laboratory, U. S. Environmental Protection Agency, and approved for publication.
Approval does not signify that the contents necessarily reflect the views and
policies of the U. S. Environmental Protection Agency, nor does mention of trade
names or commercial products constitute endorsement or recommendation for use.
ii
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FOREWORD
When energy and material resources are extracted, processed,
converted, and used, the related pollutional impacts on our
environment and even on our health often require that new and
increasingly more efficient pollution control methods be used.
The Industrial Environmental Research Laboratory - Cincinnati
(lERL-Ci) assists in developing and demonstrating new and
improved methodologies that will meet these needs both efficiently
and economically.
In this report a preliminary assessment was made of the
potential environmental impacts associated with the mining and
milling of domestic uranium ores. All forms of pollution except
radiation were considered.
It was concluded that the impacts identified were not
believed to be of immediate concern but rather are potential
problems which may arise in the long term. Future environmental
studies should consider tailings pond disposal, deep well injection
to.dispose of toxic wastes and reclamation of spoils.
Results of this work will be of interest to State and Federal
agencies and mining firms who are interested in assessing and
controlling the environmental impacts of uranium mining and
milling.
For further information contact the Resource Extraction and
Handling Division.
David G. Stephan
Director
Industrial Environmental Research Laboratory
Cincinnati
ill
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ABSTRACT
This research program was initiated with the basic objective of making a
preliminary assessment of the potential environmental impacts associated with
the mining and milling of domestic uranium ores. All forms of pollution
except radiation were considered.
The program included a review of the characteristics and locations of
domestic uranium ore reserves and a review of the conventional methods for
mining and milling these ores. Potential environmental impacts associated
with the entire cycle from exploration and mining to recovery and production
of yellowcake are identified and discussed. Land reclamation aspects are also
discussed.
The methods currently used for production of yellowcake were divided into
four categories - open pit mining-acid leach process, underground mining-acid
leach process, underground mining-alkaline leach process, and in-situ mining.
These are discussed from the standpoint of typical active mills which were
visited during the program. Flowsheets showing specific environmental impacts
for each category are provided.
It was generally concluded that the use of tailings ponds and deep well
injection to dispose of the more toxic chemical wastes represent the major
impacts which should be considered in future environmental studies.
This report was submitted in fulfillment of Contract No. 68-02-1323 by
Battelle, Columbus Laboratories, under sponsorship of the U. S. Environmental
Protection Agency. This report covers the period February 12, 1976, to July
7, 1976, and work was completed as of September 30, 1976.
xv
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TABLE OF CONTENTS
Foreword
Abstract iv
Figures - . vii
Tables vii
1. Introduction 1
2. Conclusions 2
3. Uranium Resources in the United States 4
Types of Uranium Deposits 4
Deposits in the Rocky Mountain Region 5
Sandstone Deposits ........ 5
Vein Deposits 7
By-Product Uranium From Copper Leach Solution 8
By-Product Uranium From Phosphoric Acid Production . . 8
Other Unconventional Deposits 9
Location of Active Mills 9
4. Mining and Recovery Processes 13
Conventional Mining Operations 13
Surface Mining 13
Underground Mining 15
In-Situ and Heap Leaching 16
Conventional Recovery Processes 16
Ore Preparation 16
Acid Leaching 17
Carbonate Leaching 17
Liquid-Solids Separation 18
Solution Purification and Concentration 18
Product Precipitation 19
Yellowcake Drying 20
5. Potential Environmental Impacts 21
Exploration 21
Air 21
Liquids 21
Land Surface 22
General Impacts From Mining 22
Fugitive Dust 22
Vehicle Emissions 23
Mine Water 23
Solids 27
General Impacts From Milling ~ - 28
Dust 28
Chemicals 28
Liquids 28
Solids 33
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TABLE OF CONTENTS
(Continued)
Specific Impacts From Typical Mining-Milling
Operations 34
Open Pit-Acid Leach Process 34
Underground Mine-Acid Leach Process 37
Underground Mining-Alkaline Leach Process 39
Ih-Situ Mining Process 40
6. Reclamation 44
Disturbed Areas 44
Spoils 44
Final Mining Pit 46
Tailing Ponds 46
Stabilization 47
Spoils 47
Tailings 47
Revegetation 47
References 49
vi
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FIGURES
Number Page
1 Uranium Reserve Regions, Western United States 6
2 Location of Active Uranium Mills in the United
States 12
3 Uranium Extraction Flowsheet, Open Pit-Acid Leach
Process 36
4 Uranium Extraction Flowsheet, Underground Mine-Acid
Leach Process 38
5 Uranium Extraction Flowsheet, Underground
Mine-Alkaline Leach Process 41
6 Uranium Extraction Flowsheet, In-Situ Mining
Process 43
TABLES
1 Types of Uranium Deposits 10
•
2 Active Uranium Mills in the United States and Ore
Characteristics 11
3 Estimated Air Pollutant Emissions From Earth Hauling
Equipment at a 1350 Mt/Day Underground Mine 24
4 Estimated Air Pollutant Emissions From Earth Hauling
Equipment at a 1350 Mt/Day Surface Mine 24
5 Composition of Discharge Water From Mines 25
6 Composition of Discharge Water From Underground Mines . . 26
7 Chemicals Used in Milling Operations . T 30
8 Trace Elements Leached From Ore by Milling Process .... 31
9 Analysis of an Alkaline Leach Mill Tailings Effluent ... 31
10 Process Variations Used by Active Uranium Plants 35
vii
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SECTION 1
INTRODUCTION
Uranium is an important energy source for which projected demands will
greatly increase in the near future. Identified exploitable uranium deposits
in the United States are mostly in sandstones and related rocks and the
principal known deposits are in Wyoming, the Colorado River Plateau, and the
Texas Gulf Coast.
Uranium occurs as coatings on sand grains or as filling or cement in
interstitial spaces where it has accumulated by water deposition. Because of
this, the uranium content of the ore is on the order of 0.2 to 0.3 percent
U30s- Thus, large amounts of material must be handled in mining and initial
processing operations. Some deposits are at depths which require underground
mining but surface mining is a more economical method where it can be used.
Primary processing facilities are located near the mines to reduce haul-
ing costs. Uranium from the ore is typically recovered by alkaline or acid
Leaching depending upon the nature of the ore. Solvent extraction and the use
of ion exchange resins are important variations in concentrating the uranium
values which are then precipitated to form yellowcake (85-95 percent
The scope of this investigation thus was to identify the steps involved
from mining of ore to output of yellowcake, evaluate alternative processing
methods, and assess the potential environmental impacts associated with each
operation.
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SECTION 2
CONCLUSIONS
Several potentially significant, environmental impacts have been identi-
fied based on this preliminary survey of the domestic uranium industry. The
impacts identified, however, are not believed to be of immediate concern but
rather are potential problems which may arise in the long term. Following is
a summary of the impacts believed to be of major significance.
(1) Tailings Pond Disposal. It is currently estimated that
over 9 million metric tons of tailings per year are
disposed of to tailings ponds by the domestic uranium
industry. In addition, an equal or greater amount of
waste milling solutions are also disposed of to the
ponds. The liquid portions contain various heavy
metals as well as being highly acid or alkaline depending
on the type of mill generating the waste.
The use of a tailings pond represents only a tempo-
rary solution to the potential environmental problems
which could be caused by these wastes. Methods are needed
to stabilize this material and reclaim the tailings areas.
Greater information is also needed on the movement and
amount of contaminants that enter ground and surface waters
through percolation and seepage from the tailings ponds.
Studies in New Mexico, for example, show that tailings
pond seepage can result in ground water contamination by
selenium; contamination by other substances may also
have occurred.
(2) Deep Well Injection. Several uranium mills dispose of
toxic liquid and chemical wastes by deep well injection.
The wastes result either from excess liquid not evaporated
in the tailings pond or from waste regenerant solutions
used by in-situ mining operations. Very little is known
about the overall long-term impacts on ground waters due
to deep well injection.
A similar though different impact can occur in those
plants using in-situ mining in that a loss of leaching
solution pumped into the ore body via wells could contami-
nate local groundwaters. This aspect of the overall industry
needs to be closely monitored so that if a problem does
arise the overall impact can be minimized.
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(3) Reclamation. Some research has been initiated in recent years
on reclamation of spoils, especially in coal mining operations,
but also at uranium mines. This research is directed almost
entirely to soil and water management. Additional areas of
research which are needed are the development of plant species
that are adapted to reclamation needs and to development of
alternative uses of disturbed lands which cannot be restored
to their premine condition.
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SECTION 3
URANIUM RESOURCES IN THE UNITED STATES
A preliminary survey of the geologic deposition and mineralization of
uranium resources has been conducted and is presented in this section. This
survey is based on a review of the literature and information obtained from
government agencies and industry. Some engineering judgments were applied to
quantify resource estimates where data did not exist or were poorly defined.
The terms "reserves" and "resources" need to be clarified before a dis-
cussion of mineral supply can be meaningful. They are not interchangeable
and require careful definition.
Reserves are that quantity of ore minerals in identified deposits that
can be developed at current levels of technology and costs.
Resources (whether concentrated or dilute) are fixed in limit by the
composition of the earth's crust, seas, and atmosphere. Some resources can
become reserves at higher costs and as such are most often "implied reserves"
extrapolated from generalized data.
To evaluate the supply of uranium, resources must be continuously
reassessed in terms of new geologic knowledge and changes in technology.
TYPES OF URANIUM DEPOSITS
Uranium minerals are known to occur almost everywhere in the earth's
crust which contains a mean abundance of about 2 ppm uranium. However, the
larger concentrations of uranium which make up the ore reserves are located
only in a few well-defined areas in the world. For example, about 30 percent
of the world's reported uranium reserves are found in the Rocky Mountain area
of the United States.^' The uranium is found in rather small areas in which
a few large or many small ore deposits of differing mineralization occur.
Uranium is found in a wide variety of locations. This gross variety is
considered the result of uranium's (1) physical properties, particularly its
polyvalency, (2) large atomic radius, (3) high chemical reactivity, (4) rela-
tive solubility of many of its hexavalent compounds in aqueous solutions, and
(5) its relative abundance. Consequently, virtually no geologic environment
can be considered totally free of uranium, although certain habitats
are favored.
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Deposits of potential economic importance first were identified at the
Wood Mine in Colorado in a vein deposit. In 1898 the deposits in sandstone
were discovered. Subsequently the Rocky Mountain region became the principal
domestic source of uranium. It is estimated that this region contains about
90 percent of the U. S. reserves.(D The uranium reserve regions of the
western United States with production areas and areas with reserves greater
than 500 tons I^Os are shown in Figure 1. In view of these data, the Rocky
Mountain region then must be considered as the prime source for the future
use of uranium in the U. S. for at least several decades.
Deposits in the Rocky Mountain Region
The overall Rocky Mountain area in the United States has been identified
as a uranium metallogenic province. This constitutes a broad, indefinitely
defined region centering on the curr'ent Rocky Mountains and in which an ini-
tial concentration of uranium may have occurred. Subsequent to this concen-
tration in early Precambrian time, the uranium was redistributed, reworked,
and reconcentrated by many igneous, sedimentary, and metamorphic processes.
The currently exploitable deposits are the results of that reworking.
In the Rocky Mountain region, 98 percent of the U^Og recovered has come
from sandstones and related rocks. Estimates of known reserves in those rocks
were more than 95 percent of the total reserves in 1958, and 97 percent in
1974.' ' There are probably comparable amounts of undiscovered, commercial-
grade uranium present there also. About 70 percent of the domestic production
of U30s has come from the Colorado Plateau part of the Rocky Mountains. An
evaluation of the potential U30g reserves and resources of the United States
should first consider the possibilities in comparable areas in the Colorado
Plateau and adjoining districts, especially at depth, rather than that large
high-grade deposits might be expected in other areas in the United States.
Sandstone Deposits
Most of the uranium deposits of the Colorado Plateau and adjoining
districts occur in frequently predictable stream-laid lenses of sandstone,
dominantly in the Chinle, Shinarump, and Morrison Formations. Uranium de-
posits also occur in sediments in the Wind River Formation in Gas Hills and
Shirley Basin areas, Wyoming and in other formations of lesser importance
elsewhere. These deposits also are known as the peneconcordant deposits, and
constitute by far the bulk of the "conventional" deposits. The uranium ore
bodies traditionally form tabular or lenticular layers (pods) that are nearly
concordant (parallel) to the bedding. Locally they deviate from it, espe-
cially in detail. In many deposits the elongate pods have the transverse
cross-section form of an erect crescent and are referred to as rolls. They
thus differ in form and origin from classical sedimentary (bedded) deposits
of other minerals that closely and consistently follow the bedding. The
occurrences of ore in the truly bedded deposits often can be predicted.
The ore bodies vary greatly in size, from those containing only a few
tons to those hundreds of meters across and containing millions of tons of
ore. Some deposits are thousands of meters long. In the Shirley Basin and
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SPOKANE,
POWDER
RIVER
R.VERTON,^
• U—>>'~^*
GAS HILLS
CROOKS GAP,
MAYBELL
^BELFIELD
CAVE HILLS
SLIM BUTTES
BLACK HILLS |
•EDGEMONT
GREEN RIVER
SAN RAFAEL
MARYSVALE
WHITE CANYON
GRAND JUNCTION
CASP|R_ SHIRLEY
FRONT"" BASIN
RAN£LLrDENVER
LISBON MARSHALL URAVAN
VALLEY~PASSr-L MINERAL
•^ BELT
GRANTS
MINERAL
BELT
MONUMEN1
VALLEY
KENDRICKBAY
AREAS WITH PRODUCTION AND $35.00 RESERVES
GREATER THAN 500 TONS U30g (NAMES SHOWN)
OTHER AREAS WITH PRODUCTION AND $35.00
RESERVES GREATER THAN 10 TONS U308
Source: AEC, Grand Junction. CO
FIGURE 1. URANIUM RESERVE REGIONS, WESTERN UNITED STATES
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the southern part of the Powder River Basin, Wyoming, and in the Ambrosia
Lake District, New Mexico, groups of ore bodies and the intervening thinner
mineralized zones extend intermittently from 8 to 10 kilometers.^'
Within many metal deposits other than uranium, low-grade ores commonly
form a mineralized halo, centered around the higher grade ores. However, for
uranium deposits, the edges of the peneconcordant ore bodies terminate
abruptly with no large halo of low-grade ore.
The specific sources of uranium, precise flow paths, specific and local
causes of ore deposition, and the ages of the deposits are somewhat uncertain
and may vary significantly from deposit to deposit. In general the ore was
formed by ground-water solutions that moved downdip by gravity to a reducing
environment where the uranium was precipitated. The uranium probably was
deposited and reworked by various processes, including weathering in some
instances as a final process. The primary source and controls to initial ore
deposition often are obscure. Although guides to prospecting are available
and helpful, most uranium deposits are discovered in their outcrops, and the
mineralization is traced by exploration, including drilling. This is
especially the case in the more irregular deposits.
The depth of favorable stratigraphic units is probably not critical to
the occurrence of uranium deposits. Some deposits have been discovered at
depths between 700 and 1200 meters. Certainly more can be expected to be
found. Once the incentive exists for exploration to those greater depths and
once targets are identified, more such discoveries can be expected. Butler
concluded that at least 300 million tons of ore-grade rock and probably as
much as one billion tons may occur in sandstones in the United States. Much
of the larger amount, if actually present, is overlain by at least 600 meters
of rock and will be difficult to find and exploit. Most of the occurrences
may be expected in the western part of the United States and probably in the
Rocky Mountain area.
Vein Deposits
Vein deposits, including true veins, aggregates of veinlets, and miner-
alized breccia ("collapsed") pipes also are categorized as "conventional"
deposits, together with the sandstone occurrences. They are widely distrib-
uted throughout much of the United States. With few exceptions, however,
the vein deposits represent small reserves and production.
Vein deposits that have produced uranium occur throughout the Rocky
Mountain region, especially in Colorado and Utah, and in northeastern
Washington, western and northern Idaho, southeastern- Oregon, the Great Basin
of Nevada, southern California and Alaska. They are generally-small. For
example, five of the largest deposits in the Rocky Mountain region originally
contained as much as 100,000 tons of ore. However, all vein deposits com-
bined have yielded 1,644,000 tons or about 2.5 percent of the total ore pro-
duced in the Rocky Mountain region. The Marysvale, Utah, deposit, together
with those of the Schwartzwalder Mine in Colorado, and the Midnite Mine in
northeastern Washington are the largest vein deposits in the United States.
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The downward extent of uranium in the vein deposits is undetermined in
most districts. Butler and others(2) cite vein systems which extend to 400
meters below the surface. At the Sunshine Mine in Idaho, uranium traces (but
not of a commercial grade) have been found below the 900 meter level.(2)
Probably uranium in some of the better districts extends considerably below
the known depth of occurrence.
Most uranium occurrences in vein deposits are likely of hydrothermal
origin. Recent data, however, suggest that some" vein deposits may be of
secondary origin, formed by downward-moving waters.
Geologic terranes suitable for uranium deposits are extremely wide-
spread. Undiscovered resources may equal or exceed those now known. Re-
sources of uranium in veins were considered by Butler(2) to range from a few
million to 10 million tons of ore-grade rock.
By-Product Uranium From Copper Leach Solution
The United States Bureau of Mines (USBM) has demonstrated the presence
of trace amounts of uranium in certain copper deposits of the southwestern
United States. Their studies have shown the practicability of recovering
the uranium from some copper leach solutions as a by-product of the copper
recovery. Unfortunately, uranium is not found in significant quantities in
all copper leach dumps. For instance, uranium runs as high as 50 ppm in
leach dumps from Twin Buttes, Nevada, but is as low as 2 ppm in similar
dumps at Butte, Montana. The normal range for uranium in copper dump
material is 1 to 12 ppm.
Thirteen operations were studied by USBM. However, more than twice that
many more porphyry copper deposits are known, many of which should have com-
parable amounts of uranium present. For instance, samples of oxide copper
ore from Yerington, Nevada, contain uranium. In addition, more such deposits
can be expected so that the total tonnage of uranium resources may be several
times larger than quoted. The total tonnage is a small, though significant,
fraction of that considered available from the conventional deposits.
By-Product Uranium From Phosphoric Acid Production
Phosphate rock which is used for producing phosphoric acid is also a
potential source of uranium. Many phosphate rock deposits have been examined
for uranium content. Grades higher than 0.1 percent have been reported, but
most phosphate rock contains between 0.003 and 0.02 percent U30g. The
Florida phosphate rock, which provides about 80 percent of total U. S.
production, contains 0.01 to 0.02 percent U30g.
With the increasing cost of uranium, there has been renewed interest in
its recovery from dilute phosphoric acid produced by the "wet process".
Uranium Recovery Corporation (URC), a subsidiary of United Nuclear Corpora-
tion, has just completed its first full-scale module (only the initial
extraction and stripping operations take place at the phosphoric acid plant)
at the W. R. Grace and Company plant near Bartow, Florida.
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URC has contracted to install two modules in a new phosphoric acid plant
owned by a subsidiary of International Minerals and Chemical Company near
Mulberry, Florida. This is nearby to URC's completed central processing
plant. In addition to the URC work, programs and pilot-scale operations are
being carried out by Westinghouse, Gulf Oil Chemicals, and Freeport Minerals.
Other Unconventional Deposits
Because of the wide diversity of occurrences of uranium, the potential
exists for uranium resources in many environments not yet adequately under-
stood. Among the other more promising unconventional deposits are the marine
black shales, coal, lignites, and related carbonaceous shales. Conventional,
as used here, includes the peneconcordant sandstone deposits and vein
deposits. Other occurrences are unconventional because they are not
generally produced or, at best, irregularly produced under current conditions.
A summary of the various types of uranium deposits, their principal
mineral consists, and typical occurrences in the United States is given in
Table 1.
LOCATION OF ACTIVE MILLS
The locations of active mills within the continental United States are
shown in Figure 2. The names on the map are cities or producing zones.
There are in some cases three or more active mills operating in one locale,
e.g., Grants, New Mexico. Table 2 describes each of these mills with regard
to sources of ore and ore mineralization.
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TABLE 1. TYPES OF URANIUM DEPOSITS
(4)
Type of deposit
Principal
uranium minerals
Typical U.S. occurrences
Vein deposits
Flat-lying deposits
in sedimentary
rocks:
Vanadium-bearing
sandstones 'a'
Copper-bearing
sandstones
Asphaltic
sandstones
Other sandstones
Limestone
Phosphate rock
Lignite
Bituminous shales
Uraninite, torbernite,
autunite, and
uranophane
Uraninite, coffinite
Uraninite and uranium
phosphates, vanadates,
sulfates, carbonates,
and silicates
Uraninite, uranium
hydrocarbons, and
carnotite
Uraninite and coffinite;
and uranium phosphates,
silicates, arsenates,
and carbonates
Uraninite, carnotite,
tyuyamunite, and
uranophane
Carbonate-fluorapatite
Uranium hydrocarbons
and minor secondary
uranium minerals
Uranium-hydrocarbon
complex
Front Range, Colorado;
Marysvale district, Utah;
Spokane area, Washington.
Colorado Plateau of
Colorado, Utah, Arizona,
and New Mexico. Black
Hills area, South Dakota.
Powder River Basin,
Wyoming. Big Indian
Wash, Utah.
White Canyon, Utah.
San Rafael Swell area,
Utah.
Wind River Basin, Wyo-
ming. Grants-Laguna
area, New Mexico.
Grants-Laguna area, New
Mexico.
Central Florida; Bear
Lake area, Idaho; Utah;
Wyoming; and western
Montana.
Western North and South
Dakota; eastern Montana.
Tennessee.
(a) Early production from these areas was oxidized or "carnotite-type"
ore, with the exception of the Big Indian area.
10
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TABLE 2. ACTIVE URANIUM MILLS IN THE UNITED STATES AND
ORE CHARACTERISTICS
Mill and Location
Capacity,
tpd ore
Ore Source
Mineralization
Kerr-McGee Corporation
Grants, New Mexico
7000
3500
United Nuclear-Homestake
Partners,
Grants, New Mexico
Anaconda Blue Water Plant 3000
Grants, New Mexico
Utah International, Inc. 3400
Gas Hills and Shirley
Basin, Wyoming
Exxon Highland Mill 2850
Powder River Basin, Hy.
Western Nuclear, Inc. 1500
Jeffrey City, Wyoming
Union Carbide Corporation 1350
Gas Hills, Wyooing
Federal American Partners 950
Gas Hills, Wyoming
Petrotomics Company, 1500
Shirley Basin, Wyoming
(Start-up: 1978)
Atlas Corporation 1500
Moab, Utah
Rio Algora Corporation 750
La Sal, Utah
Union Carbide Corporation 2000
Uravan, Colorado
Cotter Corporation 450
Canon City, Colorado
Dawn Mining Company 500
Stevens County, Washington
Conoco and Pioneer Nuclear, 1750
Inc., Falls City, Texas
ARCO-U.S. Steel, Dalco 125
Geoige West, Texas
Wyoming Minerals 125
Bruni, Ttxas
(a)
(a)
Five company-owned under-
ground mines in Ambrosia
Lake area.
Ore from Ambrosia Lake and
Smith Lake areas, under-
ground mines.
Open pit Paguate Mine.
Company-owned open pits
close to mill site.
Company-owned open pits at
top of Fort Union Formation.
Gas Hills, Wyoming, district
open pits and underground.
Golden Goose mine in Crooks
Gap area.
Open-pit operations at Globe
and Aljob company-owned nines.
Company-owned open pits at
mill site.
Company-owned open pit mine
adjacent to mill.
Six Atlas mines in S.E. Utah
or adjoining areas of Colo-
rado. Also 24 underground
Independent mines.
Company-owned underground
mine in San Juan County, Utah.
Sixty different underground
mines in Uravan Mineral Belt,
45 are company owned.
Principal source is Schwartz-
walder underground mine near
Golden, Colorado.
"Porphyry" uranium deposit in
Mldnite open pit mine.
Open pit mine at site.
In situ leaching of uranium
from Miocene Oakville for-
mation.
In situ leaching of uranium.
Grayish-colored sandstone containing from 2 to 5
percent lime, traces of Mo and V.
Ore minerals are coffinite, uraninite, tyuyamu-
nite, and camotite on sandstone or as inter-
stitial filling. Small amounts of Mo, V, and Se.
Sandstone w/uraniutn as interstitial lenses associ-
ated with carboniferous materials and with kero-
gens. Ore is low in lime w/some dolomitic and
bentonitic clays. Traces of Mo and V.
Sandstone w/10-15 percent of clay. Uranium min-
erals are unoxidized uraninite and coffinite.
Significant amounts of Se, As, Mo, and P.
3000 ft of interbedded shales and sandstone.
Traces of As and Se.
Cemented sandstone with interstitial occurrence
of autunite and carnotite. Traces of Mo and W.
Ore is in sandstone. Traces of Mo present.
Sandstone containing 1.5 to 3 percent lice.
Traces of Mo and V.
Ore In Wind River Formation containing uraninite-
coated sandstone with 3.5 percent CaCC-j. Traces
of Mo and V.
Fine-grained sandstone w/uranium mostly as urani-
nite and some tyiyamunite ore from White Canyon,
Utah, contains sulfide copper and V.
Ore minerals are principally uraninite ore
sandstone.
Ores are sandstone containing carnotite and 4-5
percent limestone with 1 percent ^2®$' Traces of
Ko and Cu.
Pitchblende is main nineral along with 15-20 per-
cent pyritic sulfides, 0.75 percent Cu and 0.15
percent Mo.
Secondary minerals uraninite, coffinite, and
pitchblende.
Sandstone formation of interbedded sands, silts,
and bentonitic clays. Significant amounts of Ko.
(a) Capacity In cons per year of yellowcake.
11
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ro
FIGURE 2. LOCATION OF ACTIVE URANIUM MILLS IN THE UNITED STATES
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SECTION 4
MINING AND RECOVERY PROCESSES
CONVENTIONAL MINING OPERATIONS
After a uranium deposit has been delineated and evaluated as economi-
cally feasible to mine, a mining method that is physically, economically,
and environmentally adaptable to the recovery of uranium ore from the
deposit must be selected. Factors affecting the selection of a mining
method are
• The spatial characteristics of the ore body (size, shape,
attitude, depth)
• The physical or mechanical properties of the deposit and
the surrounding rock
• Ground water and hydraulic conditions
• Economic factors (ore grade, production rates, comparative
mining costs)
• Environmental factors (surface preservation or restoration,
air and water pollution prevention).
There are two basic types of mining techniques used by the uranium
industry. These are surface and underground mining.
Surface Mining
A surface (or open pit) mine is an open-air excavation for the extrac-
tion of uranium ore. It is used to remove uranium ore from a near-surface
deposit in any rock type. This method is best suited to ore bodies of sub-
stantial horizontal dimensions which permit high rates of production and low
costs.(!' Surface mining accounts for more than half of the ore mined and
uncovers more ore per mine than does underground mining.
Open pit mining permits a wide production flexibility; it also provides
for selective mining and has the potential for 100 percent recovery of ore
within the pit limits. Mechanization provides high unit production and
requires fewer men. Mine safety, a major problem in underground mines, is
much better in surface mines.(1)
13
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Open pit mining is used where the ore deposits are near the surface
and covered with loose, easily removable soil. Some open pit mining may be
done at depths of more than 150 meters (492 ft); but usually, below 90
meters (295 ft), underground methods are preferred.(1) The ratio of over-
burden to ore removed in uranium mines is unusually large as compared to
other types of mining with ranges from 8:1 to 35:1. The expense of removing
the larger amounts of overburden is justified by the greater value of the
product being recovered.(5)
The pit layout is determined by several factors as follows:^ '
Orientation of the deposit jointings
The stripping ratio
Required rate of production
The availability of equipment
Slope stability.
The first step in surface mining is the removal and stockpiling of the
topsoil for later use in reclamation. This is usually accomplished with
tractor scrapers. The deeper overburden is then removed by scrapers or
power shovels and hauled to the disposal area. Some blasting and ripping is
also required. Optimally, the ore body is divided into areas so that one
area may be stripped before starting the stripping on the next. This will
enable mining to start before the whole ore body is exposed. Overburden
from the first part of the mined area will be placed on the surface, but
overburden from the succeeding areas will be used to backfill areas where
mining has been completed. The overburden is then covered with topsoil and
seeded. The final area of the pit is left open, its sides graded, and
remains as a lake, if it is below the water table.
When the ore body has been exposed, it is cleaned of waste material
with tractor scrapers and bulldozers. Ore is blasted or loosened with
rippers and mined with backhoes working on benches and loaded onto trucks for
hauling to the mill.
Some problems are encountered however, in surface mining, including
adverse weather limitations in some areas, and environmental problems such as
surface scarring, dust, noise, and vibrations from blasting.
Ground water intrusion also has been a problem in many of the open pit
mines. Water influx occurs in any surface mine which penetrates the water
table and water seepage must be removed for mining to progress. The tradi-
tional and an effective mine dewatering method is to allow the water to drain
into the mine and to collect in a sump via a system of ditches. From the
collection sump, the water is pumped out of the mine. In this way, the floor
of the mine is kept workable. As the mine is deepened by removal of over-
burden or ore, the mine floor is reditched. This method requires care in
scheduling the mining to assure that the sump is always the lowest point. It
also requires regular, sometimes continuous, maintenance to keep the sump and
ditch network clear. Water seepage from the exposed mine walls can often
14
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make necessary the provision of flatter wall slopes and/or benches and thus
larger stripping requirements, due to stability considerations.
Water pumped from mines may be discharged onto the land surface; for
example, to control dust, pumped through an ion exchange plant, or used as
mill process water. Mine water discharged to the environment may be
decanted through settling ponds to remove suspended solids before
being released.
A method of reducing water influx dewatering is the use of a ring of
wells located around the periphery of the mine. With proper placement, these
wells cause a localized depression in the intercepted water tables. This
method usually produces a highly clarified water. However, the locally
induced piezometric drawn down regime may influence a slightly larger area
than the sump collection method.
The amount and quality of developed mine water is also site and situa-
tion specific. Surface mine dewatering rates reported in the literature
range from less than 1890 to more than 11,000 1pm (500-3000 gpm).(6)
Underground Mining
Underground mining methods are used where the depth of the deposit makes
the removal of the overburden too costly. A mining system is selected or
developed on a safety and cost basis; suitable ground support and sometimes
preservation must be provided. The choice of a mining method usually is
dictated more by the spatial or mechanical characteristics of the deposit
than by any other factor.
Underground mining produces environmental problems principally by the
discharge of mine waters into streams and by surface disturbances such as
subsidence, both concurrent and subsequent to mining.^'
Room-and-pillar mining is a common variation used for underground
mining of uranium. Suitable deposits for exploitation by room pillar are
relatively flat-lying or slightly dipping deposits in which the ore is of
uniform grade and thickness. Room and pillar and modified room and pillar
are methods of cutting up a deposit by excavating a grid of rooms separated
by pillars of uniform cross-section. Many grid layouts have been employed,
including systems with rib pillars and square pillars with checkerboard
spacing.
Veins and steeply bedded deposits are often mined by shrinkage
stoping. This method is basically an overhand stoping system in which part
of the broken ore is accumulated as the stope is completed. The ore gains
30 to 50 percent in bulk as it is broken and some ore must be periodically
withdrawn through chutes or drawpoints in order to maintain a working floor
for additional mining. In general the vein material must be strong enough
to stand unsupported across the width of the stope. When broken, it should
not pack to the degree that it cannot be withdrawn. In deposits which
approach vertical, hanging wall and footwall rock must be relatively
15
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competent to prevent failure, both for safety consideration and prevention of
excessive dilution of ore.
In-Situ and Heap Leaching
Recently interest has increased in some areas in the use of in-situ
leaching of underground deposits of uranium. This is especially true in
South Texas where Mobil, Wyoming Minerals, and ARCO are actively engaged in
pilot scale or production programs.('»°/ Investigations are also under way
in Wyoming.(9)
In-situ mining simply means the leaching oi the ore in the geological
formation in which it occurs. The subsurface deposit is flooded with a
leach solution which is subsequently pumped to the surface ready for concen-
tration, precipitation, dewatering, and drying. Thus porosity and permea-
bility are all important in solution mining for uranium. The rock surround-
ing the ore body also should be relatively impermeable. This is necessary to
help contain the leach solutions within the producing formation so that
surface and ground waters do not become contaminated.
Currently in-situ mining projects for uranium are using a sodium or
ammonium carbonate solution for leaching of the ore. Sulfuric acid leaching
has been tried but is not now favored since excessive precipitation of cal-
cium sulfate may cause plugging of the leaching channels. Recovery of ura-
nium values from the pregnant solution is normally done by resin ion
exchange systems followed by conventional concentration, precipitation,
and drying.
Solution mining is also being applied commercially to remove uranium
from waste heaps or piles and is, rather broadly, termed heap leaching.
Heap leaching is particularly useful for the treatment of low-grade ores
which may be located at a considerable distance from the processing facili-
ties. Uranium recovery can be done at the site or the solutions pumped or
hauled to the recovery plant. Again, conventional processing such as resin
ion exchange is used to recover the uranium.
CONVENTIONAL RECOVERY PROCESSES
The following discussion is only meant to provide a general view of the
processes used for extraction of uranium. For a detailed description, please
refer to Merritt who provides a comprehensive and relatively recent treatise
on the subject.(4)
Ore Preparation
Ore preparation steps in the mill consist primarily of crushing, grind-
ing, and blending; and these operations are similar to the corresponding
processes used for other ores. Conventional equipment is used for crushing
16
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the ore to less than 2.5-cm sizes. Grinding is usually done wet to a size
typically between 20 and 200 mesh.
The uranium minerals usually form a coating on sand grains which is
partially removed in the grinding operation. The slimes thus generated have
a high uranium content and are sometimes separated from the sands for
separate treatment. Usually, however, a slime separation step is incorporated
later in the operation. Uranium milling differs in this respect signifi-
cantly from conventional milling operations where slime separation often
takes place early in the process to enable efficient application of. other
physical separation techniques.
Acid Leaching
Acid leaching is the most commonly used method for extraction of the
uranium values and is always done at atmospheric pressure. Sulfuric acid is
used in the acid leaching process. To oxidize reduced uranium minerals,
reagents such as Mn02 and NaC103 are added although aeration is often suf-
ficient. Leaching takes place in a number of agitated vessels arranged in
series. The larger operations normally use rubber-lined steel tanks;
smaller operations frequently use wooden vats. The total retention time in
the leaching vessels typically is between 10 and 20 hr, depending on the
leaching characteristics of the ore. Slightly elevated temperatures (35 C)
may be used to reduce the total leaching time.
The acid consumption for leaching depends very much on the carbonate
content of the ore and may range from 14 to 160 kg/metric ton of ore treated.
The consumption is commonly between 25 and 50 kg/ton. The pH of the leach
solution ranges between 0.5 in the tank where fresh acid is added to about
1.2 in the last tank.
Carbonate Leaching
Carbonate leaching is used when the carbonate content of the ore to be
treated is so high that the acid consumption would be prohibitive if acid
leaching were used. Carbonate leaching is much slower than acid leaching
and to improve the extraction rate, elevated temperature and pressure are
sometimes used. Leaching vessels are either Pachuca tanks, or autoclaves, or
a combination of the two.
In one plant, using autoclaves only, the total retention time is 6-1/2
hr at a temperature of 120 C, and under a total pressure of 5 atm. In
addition to the air used to achieve the operating pressure, a small amount
of ammoniacal cupric sulfate solution is added to help oxidize the ore. The
sodium carbonate consumption is about 25 kg/ton of ore.
Another mill leaches the ore at atmospheric pressure in Pachuca tanks
at approximately 80 C for a total period of 96 hr. No oxidizing agent is
used besides the air used in the Pachucas. The soda ash consumption is about
35 kg/ton of ore.
17
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In another plant the ore is first leached for 4-1/2 hr in autoclaves at
93 C and 5 atm pressure, followed by 36 hr of leaching at 80 C in Pachucas.
Again, no oxidant besides air is found to be necessary.
Liquid-Solids Separation
The uranium-bearing solution obtained by either acid or carbonate
leaching must be separated from the barren solids prior to solution purifi-
cation and uranium recovery. Conventional techniques that also find wide-
spread application in the uranium milling industry are filtration and coun-
tercurrent decantation. A method that is only widely used in the uranium
industry is the resin-in-pulp process.
Filtration as the primary separation technique is usually preferred in
carbonate circuits. This is because carbonate solutions are often recy-
cled; the filtration process requires very little dilution as compared with
countercurrent decantation, the most likely alternative. Also, carbonate
solutions are very viscous and are difficult to wash away.
Countercurrent decantation is the most widely used method in mills
with acid circuits. The underflow from the countercurrently operated thick-
eners is pumped to a tailing disposal area. The overflow is treated with
flocculating agents and then passed through a precoat filter to clarify the
solution for further treatment.
In resin-in-pulp circuits, cyclones and classifiers are used to first
separate the coarse sand fraction from the slimes. The coarse fraction is
readily cleaned by countercurrent washing. The slime fraction is contacted
with an ionic resin which adsorbs the uranium from the solution. In most
operations the resin is contained in open baskets covered with either stain-
less steel or plastic screen with 28 mesh openings. Some mills use a con-
tinuous countercurrent process in which the resin is directly suspended in
the slime slurry. The slurry is contained in cells arranged in series to
form a bank. After leaving a cell the slurry is passed over a vibrating
60-mesh screen which separates the resin from the pulp. The resin is
dumped into the adjacent cell on one side while the pulp moves to the next
cell on the other side. After six to eight adsorption stages, the pulp is
barren and can be discarded. Fresh acid eluant solution is used to desorb
the uranium from the resin. Uranium can either be precipitated directly
from the resin-in-pulp eluate or extracted from the eluate in a
solvent-extraction circuit.
Solution Purification and Concentration
Sulfuric acid is not a solvent selective for uranium only. To produce
yellowcake of acceptable quality, it is necessary to remove impurities such
as molybdenum, vanadium, selenium, iron, and many others. Furthermore,
pregnant solutions from acid leaching contain only between 0.6 and 2.0
g/liter U308. This is too low for efficient precipitation of yellowcake.
Solvent extraction techniques and, in some cases, resin ion exchange
processes are used to achieve both solution purification and concentration.
18
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The most commonly used method for purification and concentration of
acid leach solutions is solvent extraction. The process depends on the
selective extraction of uranium from the pregnant solution to an organic
phase which is brought into intimate contact with it. Another aqueous
phase, with different acid and salt contents than the original pregnant
solution, is used to strip the uranium from the organic phase back into an
aqueous phase from which it can subsequently be precipitated. By proper
selection of the relative volumes of the two aqueous phases, the I^Og con-
tent of the final solution can be made to be between 30 and 50 g/liter, a
suitable concentration for subsequent precipitation.
Ion exchange resins are used in about half of the mills using an acid
circuit. In most cases, however, they use the resin-in-pulp system dis-
cussed in the preceding section. The eluant from these systems usually con-
tains from 10 to 12 g/liter 11303. Sometimes, these solutions are further
concentrated by solvent extraction. This provides not only additional puri-
fication, but it also saves on reagents because a much smaller volume of
solution needs to be neutralized for precipitation than would be required
otherwise.
Two mills use ion exchange resins to extract uranium from clarified
solutions rather than from pulps. One of these mills uses a conventional
vertical ion exchange column. The other uses a unique moving bed system,
pioneered in this mill, and since then applied in at least two cases for
purification of mine water.
The mills with carbonate circuits use either the resin-in-pulp system
or precipitate uranium directly from the clarified leach solutions. Direct
precipitation from carbonate circuits is possible for several reasons.
Firstly, carbonate leaching is sufficiently selective to eliminate the need
for solution purification. Secondly, carbonate leach solutions have a
U30g content of about 7 g/liter which makes precipitation more efficient
than from the more dilute acid solutions. Lastly, neutralization of the
solution is not required and, therefore, no reagent saving would be realized
by further concentration.
Product Precipitation
Precipitation of yellowcake from acid circuits is achieved by neutrali-
zation to a pH of between 6.5 and 8.0. This is usually done in two stages
to allow precipitation of iron hydroxide and other impurities at a pH of
approximately 4.0. Any base may be used as neutralizing agent but ammonia is
preferred by the majority of operators because it results in a cleaner product.
Domestic mills using a carbonate circuit precipitate yellowcake by
addition of caustic soda to achieve a pH of 12. Uranium precipitates as the
sodium salt. In one case the precipitate is redissolved and reprecipitated
to eliminate some impurities. Other precipitation methods are practiced in
other countries but have found no acceptance here.
19
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Yellowcake Drying
Following the precipitation stage, a yellowcake is typically obtained by
filtering or centrifuging the yellowcake slurry. The moist cake is then
dried and/or calcined by either of two types of equipment. Most U. S. mills
actually calcine the yellowcake at temperatures from 350 C to 900 C in a
Skinner multiple-hearth furnace. This apparently decomposes much of the
sulfate which would otherwise be present as an impurity. Three mills,
however, employ steam drying at more modest temperatures (100-150 C) as a
final treatment of the yellowcake before shipment.
20
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SECTION 5
POTENTIAL ENVIRONMENTAL IMPACTS
EXPLORATION
Uranium exploration in the 1950rs often consisted of flying, driving, or
walking over an area with a portable Geiger counter and about the only environ-
mental effect was the off-road jeep trails that were left. The shallow deposits
that could be found by this method have been exploited and such deposits will
rarely, if ever, be found now. Exploration now requires extensive drilling to
locate, delineate, and appraise deeper lying deposits.
Air
Various air pollutants are generated as a result of the exploration opera-
tions. Essentially all air pollutants generated are the result of the operation
of machinery, including trucks, drill rigs, backhoes, and other vehicles. The
pollutants generated are those associated with the operation of internal com-
bustion engines and dust resulting from vehicles traveling over unpaved roads
and trails. These pollutants include particulates, oxides of nitrogen, carbon
monoxide, unburned hydrocarbons, and sulfur dioxide. The total quantities of
these combustion products emitted to the atmosphere is dependent on the number
and types of equipment in use, as well as their frequency and duration of
operation.
The most visible form of air pollutants is dust generated by moving
vehicles. This effect can be lessened by minimizing the speed of travel over
unpaved roads and trails, and the number of trips within the exploration area.
It is expected that any impact of exploration operations on air quality
would be slight and restricted to the immediate vicinity of drilling rigs and
that the duration of any such effects would be short term.
Liquids
Some local and minor alterations to the surface water system of the ex-
ploration area may result from temporary road building and from drilling
operations. The maximum possible use of existing roads and the program of
reclaiming (grading and reseeding) disturbed areas would serve to assure the
minimum possible disruption to the watersheds. The planned location of mud
pits distant from zones subject to erosion would minimize possible surface
runoff alterations.
21
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Care in road building and mud pit placement is important to protect not
only surface water supplies (i.e., impacts on developed shallow alluvial waters)
but also confined subsurface water resources. Procedures designed to minimize
surface runoff alterations can also lessen the potential for alteration of
aquifer recharge waters. The transfixing of various developable aquifers
presents some potential for the alteration of confined-water characteristics
(physical, chemical, and biological).
Land Surface
Roads—
The movement and servicing of drill rigs away from established roadways
will make trails and perhaps even require that a rough road be bladed out. In
the semiarid areas where much of this activity is likely to take place, these
off-road trails may persist for many years. Such roads often become waterways
during rainstorms and erode down to unweathered rock and soil parent material.
Establishment of vegetation along these strips is extremely slow and may never
occur without a reclamation program.
Drill Pads—
A drill rig, with its attendant equipment, requires an area about 30 by
45 meters. The drill rig itself needs to be level, which condition can be
achieved either by bulldozing the area or by blocking up the rig. Rig-leveling
causes the least surface disturbance, but a certain amount of vegetation will
be destroyed just by activity associated with the drilling.
Conventional drilling methods usually require a pit for drilling mud which
may be scooped out by a bulldozer to be 1.5 meters wide and 3 meters long. At
the completion of drilling, the mud can be allowed to dry and the scooped out
soil replaced. This small area, along with the rest of the disturbed drilling
pad will be subject to wind erosion and may be slow to revegetate. Lubricating
oils and fuel which may be spilled or discarded may also have a short-term
adverse impact.
GENERAL IMPACTS FROM MINING
Fugitive Dust
Particulates of ore and soil may enter the atmosphere from several
sources. Underground mine operations contribute less dust than does surface
mining. Underground mine sources are the ventilation shafts which exhaust the
air drawn through the mine. This air contains dust particles created by the
mining activities.
Surface mining activities generate much greater quantities of dust.
Causes of dust include scraping and digging for removal of topsoil and over-
burden, blasting, and hauling of overburden and ore; wind erosion of over-
burden may also occur, contributing to atmospheric dust. If the ore and
overburden are moist, little dust is created in blasting and stripping; haul
roads are frequently watered to reduce dust stirred up by ore trucks.(6)
Dust from spoil piles may be created by wind action; this dust may be reduced
by reclamation and stabilization of the spoil surface.
22
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The dust emitted to the atmosphere is primarily silica with small amounts
of uranium, thorium, sulfates, and other elements and compounds associated with
the soil overburden and ores of the particular area. These materials are dis-
tributed over the landscape. However, due to the low quantities of dust normally
involved, no significant impacts of dust upon vegetation, livestock, wildlife,
or water quality should be anticipated. In areas where the ore or overburden is
dry or haul roads are not watered, greater quantities of dust are emitted to the
atmosphere and settle out on the surrounding area. Vegetation is not normally
significantly impacted by the increased dust, unless it is completely covered,
but utilization of the plants by animals may be reduced. Large amounts of dust
increase the likelihood of surface water contamination through runoff.
Vehicle Emissions
Most of the emissions result from the combustion of hydrocarbon fuels in
the heavy-duty diesel-powered equipment used in the mining operations. These
emissions are primarily particulates, NOX, SOjj, and hydrocarbons. Surface mine
operations result in considerably more emissions than underground mines, since
the overburden must be removed before the ore can be mined. The estimated air
pollutants emitted from a hypothetical 1350 MT (1500 ton)/day underground and
surface mine are presented in Tables 3 and 4. The quantities of pollutants
from vehicles involved in mining will not likely be sufficient to cause a
measurable increase in a region's inventory.
Mine Water
One of the major environmental impacts associated with mining is the
withdrawal of groundwater to prevent flooding. Declining water levels in the
tapped aquifers, and possibly adjacent formations, is immediately noticed.(H)
This may affect the availability of local and possibly regional water supplies
for municipalities and industries. Lowering of the water table may also affect
the vegetation community, especially in arid regions of the west where many of
the plants are dependent on subsurface water. Water levels in the aquifers
will likely return to pre-mining conditions, after mining operations cease.
Another of the major environmental impacts of mining is the discharge of
water into the environment. Water from relief wells drilled around the mines
to reduce mine water influx and water that collects in the mines is often
discharged without any treatment. Surface mine dewatering rates range 0.77
to more than 11.0 m3/min (205-2904 gpm). Mine water may contain uranium,
selenium, zinc, sodium, sulfates, nitrates, and other substances. The com-
position of the water varies with the composition of the aquifers and other
rock formations through and over which the water flows and leaches out the
various substances. Water discharged from mines also contains suspended
solids picked up as it flows across mined surfaces and through collection
ditches. The composition of representative discharged mine waters is shown
in Tables 5 and 6.
The discharge of mine water in the arid west may transform dry washes
and ephemeral streams into perennial streams. This increased water leads to
changes in biota and land use by wildlife and livestock, particularly in
23
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TABLE 3. ESTIMATED AIR POLLUTANT EMISSIONS FROM
EARTH HAULING EQUIPMENT AT A 1350 MT/
DAY UNDERGROUND MINE
Pollutant
Particulates
Sulfur oxides
Carbon monoxide
Hydrocarbons
Nitrogen oxides
Emissions ,
kg /day
2.4
5.0
41.9
6.9
68.1
Source: Reference 6.
TABLE 4. ESTIMATED AIR POLLUTANT EMISSIONS FROM EARTH
HAULING EQUIPMENT AT A 1350 MT/DAY SURFACE
MINE
Pollutant
Particulates
Sulfur oxides
Carbon monoxide
Hydrocarbons
Nitrogen oxides
Emissions
per Operating Day,
Mining
Operations
17.0
35.4
294.2
48.4
484.6
kg /day
Overburden
Removal
18.9
39.3
327.4
53.8
538.4
Source: Reference 6.
24
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TABLE 5. COMPOSITION OF DISCHARGE WATER FROM MINES
(a)
Surface Mines
Applicant
Mine Designation
Mine Location
Flow rate, mVdav x 103
pH
Alkalinity
Total Solids
Total Dissolved Solids
Total Suspended Solids
Total Volatile Solids
Ammonia (as N)
Kjeldahl Nitrogen
Nitrate (as N)
Phosphorus Total as P
Kerr-McGee
Shirley
Basin,
Wyoming
1.7
7.9
180
612
411
163
38
0.22
0.22
<0.01
0.05
Getty Oil
KGS-JY-Mine
Shirley
Basin,
Wyoming
5.4
7.5
164
840
627
49
164
1.33
1.33
0.002
0.07
Utah Intl.
Shirley Basin
Shirley
Basin,
Wyoming
10.9
6.7-8.2
144-150
850-1,275
750-825
40-420
40-92
1.42-1.60
1.42
0-1.06
2.30
Cotter Corp.
Schwartz-
walder
Golden,
Colorado
0.3
7.3
244
1,220
1,042
178
244
0.15
0.55
12.0
0.4
Underground Mines
Union Carbide
Eula Belle
Uravan,
Colorado
0.3
8.6
358
730
590
140
70.7
<0.10
145
0.35
0.2
Union Carbide
Martha Belle
Uravan,
Colorado
0.2
8.4
384
3,103
650
2,453
192
<0.10
0.3
0.39
0.4
Union Carbide
Burro
Slick Rock,
Colorado
0.1
8.8
704
1,790
1,780
6
125
3.3
21.8
1.9
0.15
Source: Reference 12.
(a) Composition data given in mg/1 unless otherwise specified.
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TABLE 6 . COMPOSITION OF DISCHARGE WATER FROM UNDERGROUND MINES
Operator
Designation
Location
Flow rate (m3/day x 10 3)
pH
Total dissolved solids
Total suspended .solids
Total solids
so4
Cl
Fe
Mo
Na
NH3
NO.,
Se
V
Mn
Total U
Kerr-McGee^a' Kerr-McGee^'1' Kerr-McGee^3'
Sec. 30W Sec. 35 Sec. 36
Grants Grants Grants
New Mexico New Mexico New Mexico
5.1 14.3
22 100
51 8.5
2.6 5.0
160 200
19 11
1.14 0.35
0.03 0.07
0.7 0.8
0.7 0.05
4.7 19
8.4
38
13
0.3
187
0.05
0.25
0.01
0.9
0.11
3.0
United Nuclear^3"1
Churchrock Mine D
Grants
New Mexico
7.8
118
4.9
0.2
95 *
0.05
0.22
0.04
0.5
0.09
10.4
(a) , •, (b
Kerr-McGee Rio Algom
Churchrock Humeca
Grants La Sal
New Mexico Utah
8.3
7 ,
2962
47
3712
300
1.2 1597
0
0/>
97 1335
0.05 N
0.53
9
0.01 <0
0.8
0.8 N
0.88 0
.6
.16
.D.
.5
.005
.D.
.035
(a) Average concentrations in mg/1; Source: Reference 11
(b) Average concentrations in ppm; Source: Reference 13
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arid regions. The water may enter other streams, where its components contami-
nate the water and are transported to other areas. The water may also evaporate
leaving behind its dissolved and suspended materials. Seepage into shallow
aquifers may occur thus contaminating ground water. Water from mines is some-
times decanted through settling ponds before being discharged into the environ-
ment where percolation into ground water often occurs.
Heavy metals such as selenium, vanadium, radium, and molybdenum are
potentially toxic elements frequently found in uranium mine water, such as in
the Grants Mineral Belt of New Mexico(H) (see Table 6) . These elements may
enter the human food chain if the receiving water system is used for irrigation
or livestock watering.
The use of mine water for dust suppression on haul roads would cause a
gradual accumulation of any dissolved or entrained solids on the roadways.
Depending upon the concentration and composition of these dissolved or entrained
materials, leaching of the accumulated material by rainfall could adversely
affect water quality in local surface drainage areas. This possibility should
be considered in each area where dust suppression is needed and the water used
for dust control should be treated as necessary to prevent these potentially
adverse effects.
Solids
The effects of solid wastes revolve primarily around the quantity of
material excavated. The volume of waste from an underground mine is relatively
small, consisting primarily of the rock and overlying material excavated from
the shafts and haulage drifts. The mine waste is disposed of on the surface.
The area where this material is placed will no longer be biologically produc-
tive unless it.is reclaimed.
Surface mining operations require the removal of overburden to depths as
great as 150 meters (492 feet) but more commonly to depths of 30-120 meters
(98-394 ft)(5) ; areas of 160 ha (395 ac) may be excavated. The range of over-
burden to ore volumes ranges 8:1 to 35:1.(5) Currently, overburden from
initial pit construction is stored on the surface; as mining continues the
overburden is used to backfill the pit. Current practices call for the
reclamation of overburden spoils by covering with topsoil and establishing
vegetation to regain lost productivity and reduce erosion. Approximately
100 ha (247 ac) are required for waste storage at a mine that is expected to
disturb about 400 ha (988 ac) through excavation.(12) when spoils are not
used to backfill the mine, the area so covered is at least temporily unpro-
ductive. Spoil material is not conducive to the growth of vegetation without
supplemental treatment. If the spoils are not seeded or chemically treated,
wind and water erosion may occur and if streams are-nearby, they may become
polluted from spoils runoff.
A potential problem with backfilling is the possible contamination of
ground water. This may occur when ground water saturates the backfill
material and substances may leach from the mixed overburden substrates and
enter the aquifers flowing through the area.
27
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GENERAL IMPACTS FROM MILLING
Dust
Fugitive dust originates from ore stockpiles and mill tailings. It is
usually siliceous in nature but some ores are high in calcium and magnesium.
Some iron is usually present and small amounts of various elements may be asso-
ciated with the uranium, such as vanadium, copper, and phosphorus. Dust from
ore piles may be reduced during dry and windy periods by wetting. The quantity
of tailings dust varies with the treatment of disposed tailings. Dried
impounded tailings and untreated, abandoned tailings piles contribute signifi-
cantly more dust to the atmosphere than moist or stabilized tailings.
Process dust can be emitted locally from ore crushing and grinding and
yellowcake drying; however, the quantity of dust escaping is normally kept
small, either by wet crushing or through the use of scrubbers. Scrubbers are
also used to capture dust during the drying of yellowcake.
Although uranium and associated metals frequently found in the dust are
toxic, their concentrations and the volumes of dust are sufficiently low that
their impacts are localized and very minor.(6»12)
Chemicals
Gaseous emissions from milling are from fuel combustion and the chemicals
used in the various processes.
The use of fuels, such as natural gas, results in the emission of hydro-
carbons, SOX, NOX, CO, and C02• These effluents are small in quantity and do
not result in a significant impact to the local environment.
Chemicals used in the processing of uranium ore give off small quantities
of various gaseous effluents in the mill. The primary effluents from the acid
leach processes are S02» kerosene, ammonia, and amines.(10»13) Approximately
166 kg/yr (366 Ib/yr) of kerosene and 129 kg/yr (285 lb/yr) of S02 may be
vented from a 1814 MT/day (2000 ton/day) nominal plant, (10) Effluents from the
alkaline leach process may include ammonia and caustic soda vapors.(13) xhe
small quantity of vapor emitted is quickly dissipated and is not expected to
accumulate in the environment or have any significant environmental impacts.
Vapors of organic chemicals enter the atmosphere via evaporation from
tailings ponds.(13)
Liquids
Liquid discharges for acid and alkaline leach systems are approximately
4.2 and 1.05 cubic meters (1000 and 250 gallons) per metric ton of ore
processed, respectively.(5) The recycling of liquids considerably reduces the
requirements for water and chemicals, but the wastes must eventually be dis-
posed of. Water requirements are met by the utilization of mine water or well
water. A well is normally drilled to meet the requirements for potable water.
28
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The use of wells to supply process water results i'n a decrease in the amount of
water available in aquifers for other uses, but the quantities withdrawn are not
expected to have any major long-term effects upon regional water supplies. The
use of mine water for process water eliminates the need for process water wells
and reduces the volume of mine water discharged into the environment.
Liquid wastes from mills are aqueous solutions containing various chemicals
(Table 7), leached elements (Table 8), and suspended ore fines and other solids.
An analysis of an alkaline leach mill effliient is shown in Table 9.
Liquid wastes from milling operations are discharged into settling lakes
but until recently the wastes were often discharged directly into stream
channels. The current practice is to discharge the liquids along with solids
into settling basins where the liquids either evaporate or percolate into the
soil; excess water in the pond may be treated and discharged into streams or
injected into deep wells. Some of the clarified water may be recycled for use
as process water.
Wastes from an acid leaching process have a pH of about 1.5 to 2.0.
These liquors contain the unreacted portion of the sulfuric acid leaching
agent and other soluble inorganics such as calcium, sodium, magnesium, and
iron cations with sulfate and chloride anions. Small amounts of other metals
leached from the ore are also present. One to three percent of the ore is
dissolved in the process waste. The major organics present are those of the
raffinate solution (primarily kerosine, amines, and isodecanol) introduced in
the solvent extraction process. A mill processing 1,814 MT (2000 ton) of ore
per day produces about 2,722 MT (3000 tons) per day of waste milling
solution. (10) The waste milling solutions are used to transport the tailings
sands and slimes to the disposal site.
Waste solutions from alkaline leach processes have a pH of about 9.5 to
11.0 from the unreacted carbonate-bicarbonate leach solutions . (14) The use of
an alkaline leach system is more specific for uranium than the acid leach
system and fewer elements are leached from the ore. (15) Water requirements
for the alkaline leach system are about one-fourth those of the acid leach
system. A portion of the alkaline process water is discharged to the tailings
pond to prevent a buildup of dissolved solids while the remainder is recycled
through the plant. Some pond water is often recycled through mills to reslurry
sand and slimes for disposal. The volumes of liquids in ponds are reduced
through seepage into the soil, evaporation, or, after settling and filtration,
by stream discharge or deep well injection.
The quantity of seepage from the ponds varies, d_epending upon the pond
design. In evaporation-percolation ponds, seepage may account for as much as
85 percent of the losses; in clay-lined ponds with a buildup of tailings
seepage may account for only 7 percent of the loss. Excess liquids from ponds
may be discharged to streams or disposed of underground in areas where suffi-
cient land is not available; the water is neutralized and treated to remove
heavy metals and other contaminants and may flow through a series of settling
ponds before discharging or injecting.
29
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TABLE 7. CHEMICALS USED IN MILLING OPERATIONS
Acid Leach Process
Alkaline Leach Process
Acid Leach Circuit:
sulfuric acid
sodium chlorate
Liquid-Solid Separation Circuit;
polyacrylamides
guar gums
animal glues
Ion-Exchange Circuit:
strong base anionic resins
sodium chloride
sulfuric acid
sodium bicarbonate
ammonium nitrate
Solvent Extraction Circuit:
tertiary amines
(usually alamine-336)
alkyl phosphoric acid
(usually EHPA)
isodecanol
tributyl phosphate
kerosine
sodium carbonate
ammonium sulfate
sodium chloride
ammonia gas
hydrochloric acid
Precipitation Circuit:
ammonia gas
magnesium oxide
hydrogen peroxide
Alkaline Leach Circuit:
sodium carbonate
sodium bicarbonate
ammonium carbonate
ammonium bicarbonate
Ion-Exchange Circuit:
strong base anionic resins
sodium chloride
sulfuric acid
sodium bicarbonate
ammonium nitrate
Precipitation Circuit:
ammonia gas
magnesium oxide
hydrogen peroxide
Source: Reference 5.
30
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TABLE 8. TRACE ELEMENTS LEACHED FROM ORE
BY MILLING PROCESS
Magnesium
Copper
Manganese
Barium
Chromium
Molybdenum
Selenium
Lead
Arsenic
Vanadium
Iron
Cobalt
Nickel
Zinc
Thorium
Uranium
Radium
Source: Reference 5,
TABLE 9. ANALYSIS OF AN ALKALINE LEACH MILL TAILINGS
EFFLUENT
Solution Analysis
U3°8
Mn
Cu
Fe
Zn
so4
co3
HC03
Th
Na
PH
Solids Analysis
U3°8
Mn
Cu
Fe
Th
ppm
6.8
0.01
0.01'
1.0
0.6
7,500
4,000
1,100
2.0
7,100
9.5
Percent
0.017
0.01
0.0028
1.36
0.0005
Source: Reference 13.
31
-------
Water seeping from tailings ponds may contain many contaminants such as
nitrates, sulfates, trace elements (e.g., selenium in the Grants, New Mexico
area) and organic chemicals.'^,12) Ground and surface water may become polluted
as a result of seepage. Numerous radiological studies have illustrated that
pollutions of ground and surface water occurs from seepage and mill discharge.
Contamination of wells by nonradiological pollutants resulted in water unfit for
livestock in Colorado. Nitrates, which travel more rapidly in soil than some
other constituents, have polluted ground water in New Mexico. Trees have died
down-gradient from a tailings pile in Colorado, reportedly indicating a high
mineralization of ground water. (5) Ground water contaminated with selenium and
nitrates has been shown to occur near tailings ponds in the Grants Mineral
Belt of New Mexico.(H) In some areas where seepage is a problem, catchment
basins or wells have been placed downslope from the pond to intercept the con-
taminated water and pump it back to the tailings pond.
Surface water may become contaminated through ground water discharge into
ponds or streams or by discharges from mill operations. Some seepage may occur
along the tailings pond dam and surface ponds may develop in low areas near the
tailings ponds. Prior to the use of waste treatment facilities, wastes were
discharged directly into streams. This resulted in the elimination of most
aquatic life immediately below the discharges. The most toxic effects were
from the raffinate components.(16,17) No wastes are now discharged to streams
which have not been treated to reduce the toxic components of the liquids.
Treatment may include decanting through a series of settling ponds, neutralizing
the acid, removing thorium and other metals, and precipitating solids. (-5) Con-
taminants occurring in treated effluents are not expected to create any environ-
mental problems because of the low levels and characteristics of the chemicals
involved.
Liquid wastes may be injected into deep wells for disposal. The disposal
zone is usually hundreds of feet below the surface and must be separated from
aquifers by impermeable formations or contamination of present or potential
water supplies may occur. Also, the injection well must be properly cased to
prevent aquifer contamination. Contamination of aquifers from injected wastes
appears to have occurred in New Mexico.(H) The effluents are treated to
remove suspended solids to prevent plugging in the zone and to retard growth
of microorganisms. If the disposal zone material will not neutralize the
wastes, the effluents are neutralized before injection.
Tailings are presently discharged into impoundments primarily to retain
the solid wastes, but they are also designed to serve as retention and
settling basins for the liquid wastes. The pond sizes vary with the amount
of land available, disposition of liquid effluents, and type and size of mill.
Ponds range from a few to more than a hundred hectares in size with one or
more ponds per mill. A 1,814 MT/day mill in Wyoming requires a tailings
disposal area of about 60 ha.(10)
Tailings are discharged into impoundments, usually against the upstream
edge of the dam, thus forcing the free solution away from the dam. Another
method is to separate the sands from the slimes and use the sands to increase
the dam height while depositing the slimes in the inner portion of the pond.
As the slimes precipitate they act as a sealant to reduce seepage from the
pond.
32
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An ideal tailings pond to reduce the impacts of seepage of contaminants
and to confine the waste solids should be near the mill located in a natural
ravine with four basic qualifications: (1) limited runoff, (2) downstream
openings capable of being dammed, (3) adequate storage volume, and (4) an
underlying impermeable geologic formation. Natural runoff should be diverted
from the tailings pond to prevent flooding during high rainfalls. The dam
would be constructed with a clay core to prevent seepage and an outer shell of
erosion resistant material. If the pond is not located on an impermeable for-
mation, a clay blanket should be placed over the entire basin behind the dam to
reduce seepage.
Tailings ponds support little, if any, aquatic life because of their pH
and toxic substances. However, their effects on birds, particularly waterfowl,
and other wildlife which may inadvertently use the ponds are not known.(6,10,18)
It is expected that waterfowl in the central and pacific flyways do land in the
ponds during migration, particularly in the arid western regions of the U.S.
The birds probably do not remain in the ponds for any extended period of time,
but they can be expected to ingest some of the solution. The effect of the
chemicals upon feathers and skin, toxic effects, bio-accumulation, or suit-
ability of the affected birds for human consumption has not been evaluated.
Sewage treatment facilities are necessary to handle the needs of the
employees. The facilities consist of aerated lagoons, septic tanks with leach
fields and oxidation ponds. Effluents from the facilities are discharged to
the mill process water system or tailings pond.
Solids
Large quantities of solid wastes must be disposed of at milling sites.
Approximately 98 percent of all processed ore is discharged as tailings. Over
six million metric tons of tailings were produced by mills in 1974.(5) This
waste is disposed of in tailings ponds and consists of approximately 80 per-
cent sands and 20 percent slimes.(5) Some solids are also suspended in the
liquid effluents.
Old methods of tailings disposal were to discharge the wastes directly
into streams or to create piles, frequently near the streams. Direct discharges
resulted in high sediment loads and dissolved solids in the streams. Tailings
were frequently washed into streams by high waters and water percolating through
the piles leached out contaminants that moved into ground water and streams.
Tailings piles were not reclaimed when milling operations ceased.
Several types of environmental problems may result from tailings solids.
Substances (e.g., selenium and nitrates) may leach from the tailings and enter
ground and surface waters when the tailings basin is permeable. This has been
shown to be a problem in the Grants Mineral Belt area of New Mexico. (H) Tail-
ings must be kept moist to prevent wind erosion. Otherwise the tailings
particles will be transported to adjacent lands and waters where contaminants
may be taken up by crops or ingested by livestock. Abandoned tailings are
biologically unproductive due to their high acidity or alkalinity, lack of soil
33
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and moisture and blowing sand. If tailings ponds are to be covered with soil
when operations cease, additional areas must be disturbed to obtain this soil,
thus increasing the area to be reclaimed.
SPECIFIC IMPACTS FROM TYPICAL
MINING-MILLING OPERATIONS
This section presents a summary of the environmental impacts from example
uranium processing categories. It is based on field visits to typical plants
and information obtained from the literature. The following categories and
number of plants in each category were selected for evaluation:
Number
Category of Plants
(1) Open pit mining-acid leach process 8
(2) Underground mining-acid leach process 4*
(3) Underground mining-alkaline leach process 4*
(4) In-situ mining 2
Open Pit-Acid Leach Process
This industry category is the most prevalent in total number of plants (8)
and accounts for about 50 percent of the total U.S. production of yellowcake.
The plants in this category, for the most part, are in various geographical
sections but the majority of the plants are in Wyoming. Table 10 lists these
plants and certain aspects concerning the processing method to produce
yellowcake.
The open pit acid-leach category is typified by the Exxon, Highland Mine
located in the Powder River Basin of Wyoming. The flowsheet for this mill is
shown in Figure 3. Following is a discussion of the various environmental
impacts indicated in this figure.
Mine Water—
The influx of water to open pit mines is discussed in detail in the pre-
ceding section. This general impact occurs in the Highland Mine since the pit
is below the local water table. The water is controlled by a system of ditches
and a sump from which the water is pumped to a settling basin. Final disposal
of the water is to the mill process or the tailings pond.
Another aspect pertaining to mine water is the use of diversion dams to
direct rainfall away from the open pit operations. Three such dams are used
at the Highland Mine and the water is currently discharged to a nearby stream.
Includes one plant which has both an acid and an alkaline leaching circuit.
34
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TABLE 10. PROCESS VARIATIONS USED BY ACTIVE URANIUM PLANTS
10
ID
m
a
n
CD
Pi
5
Liquid/Solid Concentration Precipitation
Plant Location Separation Method Method Reagent Dryer
Open Pit Mine Acid Leach Process
Exxon Wyoming
Utah International, Inc. Wyoming
Union Carbide, Uravan Colorado
Union Carbide, Gas Hills Wyoming
Petrotomics Company Wyoming
Anaconda Company New Mexico
Conoco and Pioneer Nuclear, Inc. Texas
Dawn Mining, Company Washington
CCD
CCD
CCD
SS
CCD
SS
CCD
CCD
SX
IX + SX
IX
RIP
SX
RIP
SX
IX
NH3
NH3
NH3
NH3
NH3
MgO
NaOH
NH3
MH
SD
MH
MH
MH
SD
--
"••
Underground Mine-Acid Leach Process
Kerr-McGee Nuclear Corporation New Mexico
Federal-American Partners (&) Wyoming
Atlas Corporation (acid circuit) Utah
Western Nuclear, Inc. Wyoming
CCD
SS
CCD
SS
Underground Mine- Alkaline Leach
Rio Algom Corporation Utah
United Nuclear-Home stake Partners New Mexico
Atlas Corporation (alkaline circ) Utah
Filtration
Filtration
SS
SX
RIP + SX
SX
RIP + SX
Process
None
None
RIP
Cotter Corporation Colorado CCD + Filtration None
In- Situ
Atlantic Richfield Company Texas
Wyoming Minerals Texas
(a) This plant uses some ore from open pit mines
Mining
--
M ••
Legend: CCD - Continuous countercurrent decantation RIP -
SS - Sand- slime separation
SX - Solvent extraction
IX - Column ion exchange
MH -
SD -
IX
IX
Re sin- in- pulp system
Multiple hearth- skinner
Steam dryer-Proctor and
350 F)
NH3
NH3
NH3
NH3
NH3
NaOH
NH3
NaOH
NH3
dryer
SD
MH
MH
MH
--
MH
MH
MH
SD
(600-1500 F)
Schwartz (200-
-------
Fugitive
Dust
Organic
Vapors
OJ
Yellowcake
Precipitation
Yellowcake
Figure 3. Uranium extraction flowsheet, open pit-acid leach process.
-------
Fugitive Dust—
This impact is discussed in detail in the preceding section.
Particulate Emissions—
At the Highland Mine, ore is crushed by a jaw-crusher and stored in silos
prior to feeding into a rod mill. Particulate emissions are generated at both
the crusher station and the ore transfer and storage facilities. The emissions
are controlled by two Ducon scrubbers at the crusher and ore silos. These
scrubbers are rated at 95 percent efficiency and would result in a total partic-
ulate emission of about 130 tons per year.(10)
Tailings Pond Seepage—
This potential environmental impact is perhaps the major consideration
within the uranium industry. Impoundment of all mill wastes to a tailings pond
is almost universally applied. For the Highland Mine, it is estimated that
about 2000 tons per day of solid wastes and 3000 tons per day of liquid wastes
will be disposed of to the tailings pond.(10) The liquid will have a pH of 1.5
to 2.0. Included in these wastes are various heavy metal compounds, organic
materials such as kerosine (165 kilograms per year) and ammonia.
Ideally, the tailings pond will be a final disposal with evaporation
taking care of much of the liquid effluents. However, seepage can occur from
the pond and has been noted at the Highland Mine. The current seepage is low,
has a neutral pH, but is high in sulfates. It is currently being pumped back
to the pond from a collection sump and is monitored closely.
Organic Vapors—
Vapors of kerosine and ammonia are, of course, prevalent in any solvent
extraction and precipitation process. This impact, however, is not of signif-
icance except as it pertains to plant personnel.
Dryer Emissions—
Emissions from the drying or calcining of yellowcake prior to shipment are
an environmental impact in all uranium plants. At the Highland Mine, the yellow-
cake is dried at about 300 C in a gas-fired furnace. The exhaust gases are con-
trolled by a Tubulaire wet scrubber estimated at 99.3 percent efficiency. Dust
emissions of U308 are estimated at about 380 kilograms per year.d0) In
addition the dryer exhaust would contain organic vapors from decomposition of a
polyacrylamide flocculant, and small quantities of ammonia and S02 •
Underground Mine-Acid Leach Process
This category accounts for almost one-third of the^ total production of
uranium in the United States. However, only four plants are contained in this
category. The major production is obtained in the Grants Mineral Belt of New
Mexico.
In this category, the basic process of uranium extraction remains essen-
tially the same as described in the previous category. However, due to under-
ground mining operations, there is an added impact of underground mine water.
A generalized flowsheet for this type of mill is shown in Figure 4. This
37
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Recycle Resin
oo
1 t
1 Under- 1 fc Jaw 1 RIP Circuit Sweco Elution
ground f™ * Crusher UCountercurrent) ~^- Screen r Circuit ^ niter -».,
i Mine
1 . . i '
' t J ,'
| Secondary
Mine Water Cone ' Particulate
j _ Crusher i -Emissions
r-1-- "2, 1 •
| Resin ' ! ,
r— I Ion i ' — •-• Rod
1 [Exchange ' | Mill
1 ! _ » '
To SX Ball
Circuit Mill
H0SO. , | Steam
24 ]
1 MO. — i r— Iron Powder
n 2 1 i " * T
Trnn fnH ,1.1 ,1 I ,
Mltle T«o^U4«« f
Leacnine -« '
Water • m ,
• j Tanks
HO
' t ''
b limes
Separation ;
Sands
Tailings
Seepage ^
H20
SU
Organic Pregnant Liquorf
Vapors L "™"
• Solvent U* .
.mes Extraction ! *
^L L->
I Stripping ,
T" "" '•'
Pregnant Barren
Strip Organic
NH3 ...
if f ^
; Yellowcake
i Precipitation .
1 i-T- 1 _-— CNH . •> _ SO .
1 1 1 ^—-^'2 4
k Bleed ,. T . ,
*^
Pond
_, ^ _.^_
Thickener '
V" i ^L
\ ! Particulates
^Centrifuge & Vapors
— i- .... :
r .„„ j
Dryer
\ — p-
Yellowcake
Figure 4. Uranium extraction flowsheet, underground mine-acid leach process.
-------
flowsheet is highlighted with the sand slime separation and resin-in-pulp (RIP)
circuits. The various environmental impacts due to this type of operation are
discussed below.
Mine Water—
The impact of mine water from underground mining is higher than that of
the open pit mining operation. In this case a substantial amount of uranium is
dissolved in the mine water. For example, at the Kerr-McGee plant in New
Mexico, the mine water typically contains 2-12 ppm 11303, and this water is
processed at the mine site to recover the dissolved uranium by resin ion ex-
change in fixed bed columns. Portions of this effluent water (uranium stripped)
are pumped back for the underground leaching operation and the remainder is
disposed of. After treatment, the mine water will typically contain about 1.0
ppm 11303.
Particulate Emissions—
Most of the particulate emissions occur during primary and secondary
crushing of the ore. The emission sources are.controlled by wet scrubbers. No
information is presently available on emission rates for example plants in this
category.
Tailings Pond Seepage—
For sand-slime separation circuits, the slime portion of the tailings is
impounded whereas the sand fraction Is used for dam-building purposes. The
tailings will have a low pH of 1.5. Most of the metal and organics content of
of the tailings remain in the pond.
Seepage from the tailings pond does occur. In some mills where the tail-
ings water is not returnable for use in the mill because of its high dissolved
solids content, the deep well disposal technique is practiced to dispose of the
solution. For example, at the Anaconda plant in New Mexico, up to 1500 1pm are
disposed of by deep well injection. In one case, however, the excess water,
after neutralization, is discharged to the Colorado River.
Organic Vapors—
The impact due to organic vapors is not significant except as it pertains
to plant personnel.
Dryer Emissions—
The impact due to dryer emission may be significant, however, the exhaust
gases (e.g., U30g dust, S02, and other organics) are typically controlled by
wet scrubbers. Estimates of these emissions are described for the previous
category.
Underground Mining-Alkaline Leach Process
Although underground mining is the most common method of uranium mining,
the combination of underground mining and alkaline leaching process is utilized
by only a small proportion of the uranium mills. This category accounts for
only about 15 percent of the total U.S. production of yellowcake.
39
-------
An example of the underground mining-alkaline leach category is the Humeca
Mill operated by the Rio Algom Corporation in La Sal, Utah. The flowsheet for
this mill is shown in Figure 5. A discussion of the various environmental
impacts indicated in this figure follows.
Mine Water—
Water from the production shaft is utilized in the mill process. Most of
the water from the ventilation shaft is diverted to a nearby ranch with the
remainder being used in mining operations or disposed of in the tailings pond.
Mine Air Particulates—
The high air flow rate and low quantity of particulates (2.2 mg/m3) will
result in a very negligible impact.
Fugitive Dust—
Fugitive dust is minimal; its impact has been discussed in the previous
section.
Mill Particulate Emissions—
Air cleaning equipment has been installed at the ore transfer areas,
crushing plant, and ore sampling room to remove particulate matter from the
air before it is discharged to the atmosphere. In these areas the air is
passed through cloth bag filters. Vapors and dust from the yellowcake pack-
aging and drying operations are passed through a venturi scrubber and centri-
fugal eliminator. All mill air effluent contain less than 0.03 grains/ft3
(68.3 mg/m3).
Tailings Pond— .
Impact may result from both the impounded tailings solution and seepage
from the pond.
The tailings solution has a pH of about 9.5 and contains high concen-
trations of dissolved solids. Typically, a major part of the solution will
be recycled to the mill process to be used in leaching. This results in a
solution disposal rate of only one-fourth that of acid-leach mills.
The impacts of seepage from the pond have been discussed earlier. Ap-
proximately 500 tons of solids and 280,000 liters of waste milling solution
will be discharged daily into the pond. Approximately 10 percent of the
solution is expected to be lost through seepage until the pond is sealed by
tailings.
Combustion Vapor—
Approximately 32 percent of the flue gas from the natural gas fuel is
directed to the carbonation tower where the C02 is absorbed. The remainder
of the gas is discharged out a stack. The quantities of combustion products
are not expected to have any impacts.
In-S^itu Mining Process
Recovery of uranium by in-situ mining has been used for a number of years
40
-------
Fugitive
Dust
Under-
ground
Mine
i
I t
Ore
Storage
Mine
Water
Pregnant
Solution
1 Particulate
I—Emissions
Pachuca-Autoclave
Leaching
Separart-
Filtration
Circuit
Reclaim
Wash ' I
Water Residue
Residue
Flue Gas
1
NH,
Yellovcake
Precipitation
Participates
& Vapors
Yellowcake
Figure 5. Uranium extraction flowsheet, underground mine-alkaline leach process.
-------
but has just recently experienced a rapid growth rate, especially in South
Texas. Presently, however, only two plants (see Table 3) are considered to be
in a production stage although several other companies are involved in pilot
testing. The production of yellowcake by these two plants is currently esti-
mated at about 250 tons per year which accounts for 1-2 percent of the total
U.S. production of yellowcake.
The in-situ mining category is typified by the ARCO plant located approxi-
mately 16 kilometers southwest of George West, Texas. The flowsheet for this
plant is shown in Figure 6. Following is a discussion of the various environ-
mental impacts indicated in the figure.
Potential Leachate Losses—
The potential loss of leachate (ammonium carbonate solution) produces
perhaps the primary environmental impact which could arise from this type of
operation. At the ARCO facility, the solution is pumped into the ore body at
the rate of about 7000 1pm and ideally is totally withdrawn at the same rate.
It is realized, however, that some losses must occur due to dilution and mixing
with ground waters and migration of the solution both in a horizontal and
vertical plane. The magnitude and effect of such losses are unknown at the
present time. Consequently, ARCO has numerous monitor wells to warn of
potential leachate losses.
The pumping of solution 1 mile to and from the recovery facilities also
could cause an impact to the environment through pipeline failures or main-
tenance activities.
Sludge—
Backwash sludge from the recovery operations amount to about 15 tons per
year at the ARCO plant. The sludge consists primarily of sandstone solids but
probably contains small amounts of heavy metals. It is currently disposed of
by burial. This environmental impact is not believed to be significant.
Sparge Air—
This atmospheric emission is considered a minor impact primarily because
of the small volumes involved. The gases would contain some C02 and acid
vapors.
Dryer Emissions—
This impact is similar to other industry categories and is described in
previous sections.
Chemical Wastes—
All chemical wastes at the ARCO plant are sent to a holding reservoir
where evaporation takes care of much of the liquid volume. The excess solution
(less than 400 1pm), however, is disposed of by deep well injection, some 1400
meters below the surface. Typically the injected solution would have a high
concentration of dissolved solids and contain significant quantities of heavy
metals such as molybdenum, uranium, arsenic, and selenium, which makes the
solution highly toxic. The overall impact both in the near and long term of
deep well injection is unknown.
42
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Potential
Leachate
Losses
Backwash Water
, if
1^
Pattern ) ' **
, ! Surge
Area ; 6
tank
I
Sparge Air
NaOH
1
*
[7— I 1 _ Eluate
c C Storage
t h _ ,
Tank
v r
a c NH,
to
' 1 ' ,Tank
. — ^, Backwash
Reservoir
pipeline • • . .
• 1 Fil- 1 »• Sludge, 15 tons/yr
ii
' • Make-up Chemicals
/-> "^ !
R
a
r e
jj s Solution
0 „ Storage
— "
n ._
~* " Tank „ ,
H SO 1, i • jalL
i r *
i r— • Solution 1
Clarifier i-*-Dust and Vapors
_, ^T^
°"H
i
Yellovjcake
l Caust
Caustic Waste
Chemical
Reservoir
Deep Well
Disposal, <100 gpm
Figure 6. Uranium extraction flowsheet, in-situ mining process.
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SECTION 6
RECLAMATION
DISTURBED AREAS
The objective of reclamation is to reconstitute the disturbed area in
such a manner that when operations end all of the disturbed land will be
suitable for alternative uses.
Spoils
Many of the known uranium deposits in the United States occur in areas
where efforts to reclaim disturbed areas may be expected to meet with rather
severe problems. The Wyoming Basins and Colorado Plateau areas have low
rainfall, generally 25 cm (10 in.) or less, and thus the soils are poorly
weathered and leached and vegetation has not been prolific enough to develop
reservoirs of soil organic matter. This makes reclamation doubly difficult
because the disturbed soils and spoils are often not of good quality for
plants and because sufficient water for plant establishment and growth may
be lacking or expensive. Because they disturb much greater areas, surface
mines are of much greater concern than are underground mines.
Chemical and Physical Properties—
Soil has been defined as the upper, weathered, and biologically moled
part of the regolith. Another, more detailed definition is: a natural body,
engendered from a variable mixture of broken and weathered minerals and
decaying organic matter, which covers the earth in a thin layer and which may
supply, when containing the proper amounts of air and water, mechanical
support and in part sustenance for plants. These definitions are very broad.
Overburden materials, except for the so-called topsoil, which make up mine
spoils do not fit within either definition. This may be the case in many of
the areas where uranium ore is found. These are areas where low rainfall
inhibits weathering, allows salt accumulation, and limits plant and
microbiological populations.
Spoils consist of the unweathered and unconsolidated rock, gravels, and
allied materials which lie from the surface down to as much as 90 m (295
feet). These materials have not been exposed to weathering processes to re-
duce the materials to the finer sized sands, silts, and clays or to leach out
salts. Neither have they had the biological activities of plants and animals
to modify the soil physical and chemical properties and to add organic mat-
ter. Thus, the spoils have poor textural properties, are barren of nutrients
44
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needed for plant growth, and have no soil fauna (worms, microorganisms, and
related organisms) to aerate the surface and make nutrients available.
The usual practice to overcome these problems is to cover the spoils
with previously stockpiled topsoil. Where the amount or quality of topsoil
make this uneconomical, it may be possible to add fertilizers and soil
conditioners to the spoils and thus reestablish the productive capacity of
the area. Stabilizing the spoils against erosion with chemicals is another
alternative but is generally unacceptable because (1) chemical costs are
high, (2) the improvement is only temporary, and (3) the chemicals seal the
surface and prevent moisture penetration.
Water Relationships—
When an area of land surface is disturbed, it follows that surface
water patterns are also disturbed. Where the disturbance goes deeply be-
neath the land surface, ground water patterns may also be disturbed. Of par-
ticular concern in reclamation is the availability of water to support plant
growth. This water must come from precipitation, ground water, or be
supplied by irrigation.
The fact that spoils are in piles limits their ability to retain rain-
fall unless the piles are graded to provide catchment basins and terraces.
In addition, spoils may weather rapidly to clay or clayey materials which
resist water infiltration. The result is likely to be that most precipita-
tion will become runoff and not only fail to provide water for vegetation but
also erode the piles of spoil. This is unsightly and keeps the surface from
achieving the stability necessary for successful reclamation. In addition,
the runoff water is likely to carry with it suspended particles and soluble
salts that pollute receiving streams.
Normal open-pit mining practices seek to minimize the large spoil piles
and abandoned pits by backfilling mined-out pits. Topsoil replaced on the
backfill will likely not be over about 0.3 meter in thickness and beneath it
will be the unconsolidated spoil as described above. Thus the layer of top-
soil may have nearly all of the water holding capacity and this will not be
sufficient to sustain vegetation for very long. These areas and the spoil
piles, also with a layer of topsoil, may require irrigation for several
years before plants can sustain themselves.
There are practices in the grading of spoils which can help with water
management and conservation. The forming of catchment basins and terraces
to hold water on the spoils will increase the amount of runoff available to
the plants as well as decrease water erosion. Another practice which has
apparently been ignored is to establish a planned slope direction or aspect.
It has been determined that vegetation on a north-facing slope requires only
about half the amount of applied water as that on a south-facing slope.
Water requirements of horizontal surfaces and east and west slopes are about
intermediate between those of the north and south slopes. This relates to
the angle of incidence of the sun and thus the soil temperature. Grading
spoils so as to leave long north slopes should make water use as efficient
45
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as possible and reduce the length of time that irrigation is required to
establish the vegetation.
Final Mining Pit
Open-pit mining leaves a hole in the ground when operations cease even
though the mine is backfilled throughout its operation. The alternative
would be to place the spoils generated by the opening of the mine back into
this final pit. Likely this could be done only if the shape and position of
the orebody made it possible to plan the mine so that the final pit was next
to the original spoil pile. Even then, if the mine has operated for a
number of years, the value received by digging up spoils which have become
stabilized and probably vegetated is questionable.
The final pit must be considered in abandoning a mine and, unless
handled properly, it will constitute a hazard to both people and wildlife.
The remaining highwalls should be graded so that the sides can be walked up
and down without danger to wildlife, livestock, or humans. Even in semiarid
areas, an open-pit mine will probably intercept aquifers and the abandoned
pit will fill with water to some depth which will depend upon the hydrostatic
head in the aquifer.
In a semiarid area, as is the case where many uranium ore deposits are
located, the resulting small lake could be an asset as a source of drinking
water for domestic animals and wildlife if the water is not contaminated. It
would be extremely attractive to these animals and, as stated above, would be
hazardous to them unless properly graded to minimize the danger of drowning.
Even when a pit has been properly graded, it will likely take some time for
the banks to stabilize. Erosion of the banks by rainfall and sloughing off
of materials softened by wetting from the standing water may result. To
minimize this, the banks should be planted to soil-holding vegetation,
preferably grass, and then monitored until establishment is successful.
Tailing Ponds
The tailings themselves should be of little or no concern in a discus-
sion of reclamation because they should be completely stabilized and covered
with up to 0.6 m (2 feet) of soil when milling operations cease. Great care
is taken in the design, preparation, and management of tailings ponds to
prevent radioactive liquids and radon air emissions from being released to
the environment.
The actual area to be reclaimed will be larger than the pond itself
because an adjoining area will have to be scraped to provide the soil cover
for the pond. Such a scraped area, in a semiarid environment, is extremely
difficult to reclaim because the newly exposed surface lacks the
characteristics of a developed soil. Reclamation of these areas will
encounter the same problems as spoil piles.
46
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STABILIZATION
Spoils
The digging and piling of mine overburden usually leaves fine-textured
and easily eroded materials on the surface and, at the same time, allows
these materials to dry out. These piles are thus subject to wind erosion.
They are also subject to water erosion because the materials are
unconsolidated and because natural drainage channels no longer exist.
Tailings
The objective in stabilizing tailings is different from that of spoils
and thus the methods to be used are likely to be different. With tailings,
the concern is the escape of radioactivity while, with mine spoils, stability
must be achieved to permit vegetation to become established.
Tests have been made of various chemical treatments for sealing the
surface of tailings primarily to prevent wind erosion. A study was con-
ducted by the Bureau of Mines, Salt Lake City Metallurgy Research Center on
tailings at Tuba City, Arizona.(19) Materials used were an elastomeric
polymer and a calcium lignosulfonate. These were sprayed on the dried ponds
as aqueous solutions where they formed crusts which were strong enough to
prevent wind erosion and which, upon drying, were insoluble in water. The
persistence of these crusts needs to be evaluated. The direct cost of
materials and their application was about $827 per hectare ($335 per acre)
in 1969, while the cost to cover tailings with soil and rock at other loca-
tions was from $2,717 to $12,350 per hectare ($1100 to $5000 per acre).
Reclamation of the tailings area of Exxon's Highland Mine, upon cessation
of operations, was projected in 1973 at $2,470 per hectare ($1000 per acre).
This will include allowing the free water to evaporate and covering the
surface with 0.6 meter (2 feet) of soil into which sufficient limestone has
been mixed to neutralize acid which may move up into the plant root zone.
The area will be planted to grasses with medium rooting depths which will
utilize most of the depth of the soil covering but not extend into
the tailings.
REVEGETATION
The usual concept, a valid one, is that revegetatioii of a disturbed area
will be most successful by using plant species that are indigenous to the
immediate area. These species are at least adapted to the climate, elevation,
and insolation level.
Problems emerge in two specific areas having to do with revegetation.
The first is the frequent (in the past, total) lack of advance planning for
future uses of the reclaimed land. The usual assumption is that the
premine productivity can be restored by planting the same species that were
there before mining and this becomes the reclamation program. Such a program
ignores the fact that the soil and water conditions and relationships will be
47
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so disrupted by the mining activity that these same species may not now be
adapted and they may not even survive the new conditions. In the semiarid
areas of the country, particularly the southwest deserts, restoration of
premine conditions is a restoration of range to a low level of productivity.
A specific problem area is that of management of plant species suitable for
reclamation. Indigenous plant species should be the most successfully
established. However, many of the desirable plant species are poor or
unreliable seed producers, they are slow to become established, they
produce low yields, and they do not respond well to management.
Normal soil, even in dry climates, has a high population of soil fauna
and microorganisms which are necessary for plant growth. These organisms
break down organic matter so that it can be recycled as plant nutrients and
they also mix and aerate the soil surface. In the stripping operation, the
overburden materials are so mixed and inverted that there is little chance
of a viable population of the soil-born organisms remaining. Even when the
original topsoil is stockpiled, these organisms are likely to die out in all
but the surface of the stockpile. The result is that when the topsoil is
spread over the graded spoils, the soil organism populations may be lacking
or so greatly reduced that normal soil functions are greatly delayed.
The spoils may quickly become inoculated with the microorganisms
(fungi, bacteria) from their being carried by the wind from surrounding
areas; however, the re-introduction of soil invertebrates may be quite slow.
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REFERENCES
(1) Battelle-Pacific Northwest Laboratories. Assessment of Uranium and
Thorium Resources in the United States and the Effect of Policy
Alternatives. Final Report to the National Science Foundation.
December 1974.
(2) A. P. Butler, Jr., "Uranium", Geologic Atlas of the Rocky Mountain
Region, Rocky Mountain Assoc. of Geologists, Denver, Co., pp 315-317,
1972.
(3) "Uranium Recovery From Phosphoric Acid Nears Reality as a Commercial
Uranium Source", E/MJ, December 1975.
(4) R. C. Merrit, The Extractive Metallurgy of Uranium, Colorado School of
Mines Research Institute, Golden, Colorado, 1971.
(5) D. A. Clark, State of the Art: Uranium Mining, Milling, and Refining
Industry. EPA-660/2-74-038, U. S. EPA. NERC, Corvallis, Oregon.
June 1974.
(6) Battelle's Columbus Laboratories. Environmental Analysis Concerning
Exploration for Uranium and Possible Resultant Mining and Milling
Operations on the Navajo Indian Reservation, San Juan County, New
Mexico. Final Report to Exxon Company. April 1975.
(7) "Developers Eye Texas Potential for In-Situ Uranium Leaching", E/MJ,
July 1975.
(8) "In-Situ Leaching Opens New Uranium Reserves in Texas", E/MJ,
July 1975.
(9) "Wyoming Uranium Miners Set Sights on Higher Production", E/MJ,
December 1975.
(10) Atomic Energy Commission Report to Exxon Company. "Environmental
Impact Statement on the Highland Uranium Mill". Docket No. 40-8102.
March 1973.
(11) U. S. Environmental Protection Agency, Region VI, Dallas, Texas.
September, 1975. Impact of Uranium Mining and Milling on Water
Quality in the Grants Mineral Belt, New Mexico. EPA 906/9-75-002.
188 p.
(12) U. S. Atomic Energy Commission, Directorate of Licensing. Fuels and
Materials. April, 1974. Environmental Survey of the Uranium Fuel
Cycle. WASH-1248. Various paging.
49
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(13) Supplemental Environmental Report, Operating License Stage. November,
1971. Rio Algom Corp., Moab, Utah. Docket 408084-2. 331 p.
(14) U. S. Environmental Protection Agency, Office of Radiation Programs,
Field Operations Division. Washington, D.C. Oct., 1973. Environmental
Analysis of the Uranium Fuel Cycle, Part I - Fuel Supply. Various
paging.
(15) New Solution Cuts Uranium Mining Costs. 1975. Chemical Week 17(26):
28-29.
(16) W. E. Sigler, W. T. Helm, J. W. Angelovic, D. W. Linn, and S. S. Martin.
Dec., 1966. The Effects of Uranium Mill Wastes on Stream Biota. Utah
Agricultural Experiment Station, Utah State University, Logan, Utah.
Bull. 462, 76 p.
(17) J. B. Anderson, E. C. Tsivoglu, and S. D. Shearer. 1975. Effects of
Uranium Mill Wastes on Biological Fauna of the Animal River
(Colorado-New Mexico), pp 373-383. In: Radioecology, V. Schultz and
A. W. Klement, Jr., eds. Rheinhold Publishing Co., New York. 746 p.
(18) U. S. Atomic Energy Commission, Directorate of Licensing, Fuels and
Materials. 1974. Final Environmental Statement related to the Utah
International, Inc. Shirley Basin Uranium Mill, Shirley Basin,
Wyoming. Docket No. 40-6622. Various paging.
(19) Havens, R. and K. C. Dean, Chemical Stabilization of the Uranium
Tailings at Tuba City, Arizona, U. S. Department of Interior, Bureau
of Mines, R. I. 7288, 1969.
50
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TECHNICAL REPORT DATA
(Please read Instructions on the reverse before completing)
1. REPORT NO.
EPA-600/7-76-036
3. RECIPIENT'S ACCESSION-NO.
4. TITLE AND SUBTITLE
ASSESSMENT OF ENVIRONMENTAL ASPECTS OF URANIUM MINING
AND MILLING
5. REPORT DATE
December 1976 issuing date
6. PERFORMING ORGANIZATION CODE
7. AUTHOR(S)
A. K. Reed, H. C. Meeks, S. E. Pomeroy, and V. Q. Hale
8. PERFORMING ORGANIZATION REPORT NO.
9. PERFORMING ORGANIZATION NAME AND ADDRESS
Battelle Columbus Laboratories
505 King Avenue
Columbus, Ohio 43201
10. PROGRAM ELEMENT NO.
EHE-623
11. CONTRACT/GRANT NO.
68-02-1323, Task 51
12. SPONSORING AGENCY NAME AND ADDRESS
Industrial Environmental Research Laboratory - Gin., OH
Office of Research and Development
U. S. Environmental Protection Agency
Cincinnati, Ohio 45268
13. TYPE OF REPORT AND PERIOD COVERED
Final 2/12/76 - 7/7/76
14. SPONSORING AGENCY CODE
EPA/600/12
15. SUPPLEMENTARY NOTES
is. ABSTRACT This research program was initiated with the basic objective of making a pre-
liminary assessment of the potential environmental impacts associated with the mining
and milling of domestic uranium ores. All forms of pollution except radiation were
considered.
The program included a review of the characteristics and locations of domestic
uranium ore reserves and a review of the conventional methods for mining and milling
these ores. Potential environmental impacts associated with the entire cycle from
exploration and mining to recovery and production of yellowcake are identified and
discussed. Land reclamation aspects are also discussed.
The methods currently used for production of yellowcake were divided into four
categories - open pit mining-acid leach process, underground mining-acid leach process,
underground mining-alkaline leach process, and in-situ mining. These are discussed
from the standpoint of typical active mills which were visited during the program.
Flowsheets showing specific environmental impacts for each category are provided.
It was generally concluded that the use of tailings ponds and deep well injection
to dispose of the more toxic chemical wastes represent the major impacts which should
be considered in future environmental studies.—___
7.
KEY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
b.lDENTIFIERS/OPEN ENDtD TERMS C. COSATI Field/Group
*Surface Mining, Underground Mining
*Waste Treatment, *Waste Disposal, *Mine
Water, *Seepage, *Stabilization, Research
and Development, Surface Water, Underground
Water, Industrial Plants
*Mining Wastes, *Leach-
ability of Solids,
Physical Upgrading,
Suspended Solids,
Revegetation.
05A
05B
05C
05D
05E
08G
13B
3. DISTRIBUTION STATEMENT
Release to the Public
19. SECURITY CLASS (ThisReport)
Unclassified
21. NO. OF PAGES
59
20. SECURITY CLASS (Thispage)
Unclassified
22. PRICE
EPA Form 2220-1 (9-73)
51
.& U.S. GOVERNMENT PRINTING OFFICE:1977-757-056/5554 Region No. 5-I I
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