United States
Environmental Protection
Agency
Industrial Environmental Research
Laboratory
Cincinnati OH 45268
EPA 600 2-78 004x
SeU'mb^r 1 978
Research and Development
Source Assessment
Open Mining of Coal
State of the Art
-------
RESEARCH REPORTING SERIES
Research reports of the Office of Research and Development, U.S. Environmental
Protection Agency, have been grouped into nine series. These nine broad cate-
gories were established to facilitate further development and application of en-
vironmental technology. Elimination of traditional grouping was consciously
planned to foster technology transfer and a maximum interface in related fields.
The nine 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
8. "Special" Reports
9. Miscellaneous Reports
This report has been assigned to the ENVIRONMENTAL PROTECTION TECH-
NOLOGY series. This series describes research performed to develop and dem-
onstrate instrumentation, equipment, and methodology to repair or prevent en-
vironmental degradation from point and non-point sources of pollution. This work
provides the new or improved technology required for the control and treatment
of pollution sources to meet environmental quality standards.
This document is available to the public through the National Technical Informa-
tion Service, Springfield, Virginia 22161.
-------
EPA-600/2-78-004X
September 1978
SOURCE ASSESSMENT:
OPEN MINING OF COAL
State of the Art
by
S. J. Rusek, S. R. Archer, R. A. Wachter, and T. R. Blackwood
Monsanto Research Corporation
1515 Nicholas Road
Dayton, Ohio 45407
Contract No. 68-02-1874
Project Officer
John F. Martin
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
-------
DISCLAIMER
This report has been reviewed by the Industrial Environmental
Research Laboratory-Cincinnati, 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.
11
-------
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 im-
proved methodologies that will meet these needs both efficiently
and economically.
This report contains an assessment of air emissions from the open
mining of coal. This study was conducted to provide a better
understanding of the distribution and characteristics of emis-
ions from this industry. Further information on this subject
may be obtained from the Extraction Technology Branch, Resource
Extraction and Handling Division.
David G. Stephan
Director
Industrial Environmental Research Laboratory
Cincinnati
m
-------
PREFACE
The Industrial Environmental Research Laboratory (IERL) of the
U.S. Environmental Protection Agency (EPA) has the responsibility
for insuring that pollution control technology is available for
stationary sources to meet the requirements of the Clean Air Act,
the Federal Water Pollution Control Act, and solid waste legisla-
tion. If control technology is unavailable, inadequate, or
uneconomical, then financial support is provided for the develop-
ment of the needed control techniques for industrial and extrac-
tive process industries. Approaches considered include: process
modifications, feedstock modifications, add-on control devices,
and complete process substitution. The scale of the control
technology programs ranges from bench- to full-scale demonstration
plants.
IERL has the responsibility for developing control technology for
a large number of operations (more than 500) in the chemical and
related industries. As in any technical program, the first step
is to identify the unsolved problems. Each of the industries is
to be examined in detail to determine if there is sufficient
potential environmental risk to justify the development of con-
trol technology by IERL.
Monsanto Research Corporation (MRC) has contracted with EPA to
investigate the environmental impact of various industries that
represent sources of pollutants in accordance with EPA's respon-
sibility, as outlined above. Dr. Robert C. Binning serves as MRC
Program Manager in this overall program, entitled "Source Assess-
ment," which includes the investigation of sources in each of
four categories: combustion, organic materials, inorganic mater-
ials, and open sources. Dr. Dale A. Denny of the Industrial Pro-
cesses Division at Research Triangle Park serves as EPA Project
Officer for this series. Reports prepared in this program are of
two types: Source Assessment Documents and State-of-the-Art
Reports.
Source Assessment Documents contain data on pollutants from spe-
cific industries. Such data are gathered from the literature,
government agencies, and cooperating companies. Sampling and
analysis are also performed by the contractor when the available
information does not adequately characterize the source pollu-
tants. These documents contain all of the information necessary
for IERL to decide whether emissions reduction is necessary for
specific industries.
iv
-------
State-of-the-Art Reports include data on pollutants from specific
industries which are also gathered from the literature, govern-
ment agencies, and cooperating companies. However, no extensive
sampling is conducted by the contractor for such industries.
Results from such studies are published as State-of-the-Art
Reports for potential utility by the government, industry, and
others having specific needs and interests.
This State-of-the-Art Report contains data on air emissions from
the open mining of coal. This study was completed for the Ex-
traction Technology Branch of the Resource Extraction and Han-
dling Division, lERL-Cincinnati. Mr. John F. Martin served as
EPA Project Leader.
v
-------
ABSTRACT
This report describes a study of air pollutants emitted from the
open mining of coal. The potential environmental effect of the
source was evaluated using source severity values (source sever-
ity is the ratio of the maximum time-averaged ground level con-
centration of an emission to its hazard factor).
Open coal mining is a major method of mining coal in the United
States. Approximately one-half of the 546 x 106 metric tons of
the raw coal produced in 1972 was mined by open mining methods
(strip and auger). The representative source was defined in this
study as a mine producing 108 x 103 metric tons of raw coal per
year and having an area of 2.0 km2. The representative mine has
a life expectancy of 20 years, a stripping ratio of 13.6 m
overburden/m coal, an annual land disturbance of 98.5 x 103 m2,
and is located in the Midwest (Illinois or Indiana).
Respirable dusts, the only hazardous emissions, are generated
from five unit operations and from wind erosion; the contribu-
tions from these sources to the total dust loading are: coal
transport and unloading, 40%; blasting, 30%; coal loading, 14%;
drilling, 12%; coal augering, 1%; and wind erosion, 3%. The
respirable particulate (<7ym) for the open coal mining industry
in 1972 amounted to 3,600 metric tons. The emission factors for
the unit operations indicate that 13 g of respirable dust are
emitted per metric ton of coal mined. The total dust severity
from the representative source is 1.0 x 10~3, the coal dust
severity is 0.036, and the overburden dust severity is 0.014.
Control technology in open coal mining has been implemented for
drill rigs, haul roads, and coal refuse piles. Cyclones and
water sprays are used on the larger drills to control particu-
lates. Most states enforce water spraying of haul roads to re-
duce dust and improve safety. Control of gaseous pollutants from
stagnant coal piles is achieved by shielding the piles from wind,
applying cooling process, or removing the carbonaceous material.
The open coal mining industry is experiencing a high growth rate
(3.5% per year), and the growth factor for the industry (1978
emissions/1972 emissions) is 1.23.
This report was submitted in partial fulfillment of Contract No.
63-02-1874 by Monsanto Research Corporation under the sponsorship
of the U.S. Environmental Protection Agency. The study covers
the period September 1974 to July 1975, and the work was com-
pleted in September 1977.
vi
-------
CONTENTS
Foreword iii
Preface iv
Abstract vi
Figures viii
Tables ix
Abbreviations and Symbols x
Conversion Factors and Metric Prefixes xii
1. Introduction 1
2. Summary 2
3. Source Description 5
Process description 5
Factors influencing emissions 13
Geographical distribution . 17
4. Emissions 22
Selected pollutants 22
Definition of representative source 30
Source severity 33
4. Control Technology 35
State of the art 35
Future considerations 36
5. Growth and Nature of the Industry 38
Present and emerging technology 38
Industry production trends 46
References 48
Appendices
A. Strip and auger mining techniques from the standpoint
of regional variability 54
B. Respirable dust emission factor derivation and
supportive data 60
C. Input data, derivations, and sample calculations
pertaining to mass emission rates and represen-
tative source definition 69
Glossary 73
vii
-------
FIGURES
Number Page
1 Open coal mining cycle of events and associated
unit operations 7
2 Textural classification chart (U.S. Department
of Agriculture) and comparison of particle
size scales 11
3 Typical Western U.S. coal-bearing strata .... 12
4 Coal production by P-E region and population
density 19
5 Particle size distribution of overburden dust . . 26
6 Surface coal mine size frequency distribution . . 32
7 Surface coal mine production by mine size .... 32
8 Front-end loader 41
9 Scraper (self-propelled unit) 42
10 Straight bulldozer 43
11 Rotary drill with dust control equipment .... 45
vni
-------
TABLES
Number
1 Unit Operations Classification for Open Coal
Mining in the United States 6
2 Analyses of Selected Coals of Various Ranks ... 8
3 Concentrations of Trace Elements in Coal .... 9
4 State Production of Surface-Mined Coal by Pro-
duction Ranking for 1972 18
5 Overburden Dust Composition from an Illinois
Strip Mine 23
6 Emission Factors for Open Coal Mining 27
7 Total Emission Rates of Respirable Dusts from
Open Coal Mining by State and Nationwide ... 29
8 Ratio of Total Emission Rates of Respirable
Dusts from Open Coal Mining to Total Particu-
lates, State and Nationwide 29
9 Contribution to Respirable Mining Dust Emissions
from Each Source Within the Mine 30
10 Growth of Surface Mining 38
IX
-------
ABBREVIATIONS AND SYMBOLS
A —total area of the mine
An —annual land disturbance
A. —number of acres of surface coal land disturbed
per state per year
BCD —background
C —constant
D —representative distance from source
Dip —total dosage
e. —emission factor for wind erosion in the jth state
E^ —emission factor for the ith unit operation
F —primary standard for particulates
K —constant
P —average annual coal production
P. —state coal production for 1972
—production rate for representative mine
Q —emission rate
Qc —emission rate of coal dust from representative source
QjK —amount of respirable dust emitted from surface coal
mines of the jth coal state,
for K = 1, Qji = total respirable dust rate
for K = 2, Qj2 = respirable coal dust rate
for K = 3, Qj 3 = respirable overburden dust rate
Qo —emission rate of silica-containing overburden dust
Qp —emission rate of particulate from representative
source
QT —total release
Sc —coal dust severity from open coal mining
So —silica-containing overburden dust severity from open
coal mining
Sp —total respirable particulate (<7 ym) severity from
open coal mining
-------
Sj^ — stripping ratio
T — life expectancy
u — wind speed
XKJ — composition of respirable dust in the jth coal state,
weight fraction coal or overburden
for K = 1, KIJ = 1.0
for K = 2, X2j = 0.927
for K = 3, X3j = 0.073
X — concentration contribution of a unit operation
„ --time-averaged maximum ground level concentration
p _ . • i .
* of particulates
--lateral dispersion coefficient
O = Ax°'90^ where A is a stability constant
az — vertical dispersion coefficient
CTZ = AxB
constants
CTZ = AxB + C where A, B, and C are stability
T.E. — sum of the appropriate emission factors per state
XI
-------
CONVERSION FACTORS AND METRIC PREFIXES
CONVERSION FACTORS
To convert from
Centimeter (cm)
Joule (J)
Kilogram (kg)
Kilogram (kg)
Kilometer2 (km2)
Meter (m)
Meter2 (m2)
Meter3 (m3)
Metric ton
Radian (rad)
To
Foot
British thermal unit
Pound-mass
(avoirdupois)
Ton (short, 2,000 Ib mass)
Mile2
Foot
Foot2
Foot3
Pound-mass
Degree (°)
Multiply by
3.281 x 10~2
9.479 x 10-1*
2.204
1.102 x 10~3
3.860 x 10-1
3.281
1.076 x 101
3.531 x 101
2.205 x 103
5.730 x 101
Prefix
Mega
Kilo
Centi
Milli
Micro
Symbol
M
k
c
m
y
METRIC PREFIXES
Multiplication
factor
106
103
ID'2
10~3
10~6
Example
1 MJ
1 kg
1 cm
1 mm
= 1 x
106 joules
= 1 x 103 grams
= 1 x 10~2 meter
= 1 x 10~3 meter
= 1 x 10~6 meter
Standard for Metric Practice. ANSI/ASTM Designation E 380-76e,
IEEE Std 268-1976, American Society for Testing and Materials,
Philadelphia, Pennsylvania, February 1976. 37 pp.
Xll
-------
SECTION 1
INTRODUCTION
Open coal raining encompasses strip and auger mining of coal that
lies near the earth's surface, and it is used extensively in all
of the coal bearing areas of the United States. This industry
constitutes a source of air pollution in the form of respirable
dusts. The objective of this work was to assess the environ-
mental impact of open coal mining and to produce a reliable and
timely Source Assessment Document for use by EPA in deciding on
the need for emissions reduction.
This document summarizes information relating to the emissions
from open coal mining. The areas studied were: 1) process and
subprocess unit operations; 2) source sites; 3) mass emissions,
state and nationwide; 4) effects on air quality; 5) state of the
art and future considerations in pollution control technology;
and 6) projected growth and anticipated technological develop-
ments of the industry.
Emission factors were developed for seven mining unit operations
and for the wind erosion emission sources that are characteristic
of the industry. These emission factors were used to compile the
estimated effects on air quality.
-------
SECTION 2
SUMMARY
Open coal mining is a major method of mining coal in the United
States. Approximately one-half of the 546 x 106 metric tons
of the raw coal produced in 1972 was mined by open mining methods
(strip and auger). Most of the open-mined coal was produced in
the Eastern and Interior provinces (86%) with the balance pro-
duced in the Rocky Mountain province (14%). Nearly 50% of the
coal produced in 1972 was obtained by open mining in three
states: Kentucky, Ohio, and Illinois. A total of 16 states out
of a possible 23 were considered in this study. The seven
excluded states accounted for less than 1% each of the total
annual production.
Open coal mining is characterized by a series of seven unit
operations or subprocesses involving excavation of overburden,
removal of the coal, and coal transport. Respirable dusts, the
only hazardous emissions, are generated in five of the subpro-
cesses. The unit operations and their contributions to the total
dust loading are: coal transport unloading, 40%; blasting, 30%;
coal loading, 14%; drilling, 12%; and coal augering, 1%. These
unit operations contribute nearly 97% of the respirable dust
emissions. The balance is attributed to wind erosion (3%).
The respirable particulate (less than 7 ym) emissions for the
open coal mining industry in 1972 amounted to 3,600 metric tons.
All emission rates and contributions are based on assumed
emission factors. The emission factors for the unit operations
indicate that 13 g of respirable dust are emitted per metric ton
of coal mined. An average of 0.019 g of respirable dust is
emitted via wind erosion of the mined surface per second per
square kilometer of mined land. Estimates of the error in the
wind erosion factor were not possible.
The respirable dust from open coal mining is composed of 93%
coal and 7% overburden. The representative free silica content
of the overburden is 20%, while coal averages 3% (all values
being percent by weight).
1 metric ton equals 106 grams; conversion factors and metric
system prefixes are presented in the prefatory material.
-------
Emissions from the open coal mining industry constitute 0.019%
of national emissions of particulates. Four of the 16 states
have emissions of respirable dust exceeding 0.1% of the state
total particulates. These states are Wyoming (0.17%), Kentucky
(0.15%), West Virginia (0.13%), and North Dakota (0.11%).
A severity factor, S, was defined to indicate the hazard poten-
tial of the emission source:
= Xmax
F
where Xmax ^s the time-averaged maximum ground level concentra-
tion of each pollutant emitted from a representative open coal
mining source, and F (the primary ambient air quality standard
for criteria pollutants) is a "corrected" threshold limit value
for non-criteria pollutants.
The representative source was defined as a mine producing
108 x 103 metric tons of raw coal per year and having an area
of 2.0 km2. The representative mine has a life expectancy of
20 years, a stripping ratio of 13.6 m overburden/m coal, an
annual land disturbance of 98.5 x 103 m2, and is located in the
Midwest (Illinois or Indiana). The total dust severity is
1.0 x 10~3, the coal dust severity is 0.036, and the overburden
dust severity is 0.014.
Control technology in open coal mining has been implemented for
drill rigs, haul roads, and coal refuse piles. Cyclones and
water sprays are used on the larger drills to control particu-
lates. Most states enforce water spraying of haul roads to
reduce dust and improve safety. Control of gaseous pollutants
(carbon monoxide, CO; hydrocarbons; and nitrogen oxides, NOx)
from stagnant coal piles is achieved by shielding the piles
from the wind, applying cooling processes, or removing the
carbonaceous material. Although it is not practiced directly
as a method for air pollution control, the judicious placement
of explosive delays in blasting rounds can reduce dust by
efficient fragmentation (small pieces of coal). No control
technology is applied to other facets of the industry.
The application of chemical or water sprays during unit opera-
tions such as coal transport/unloading, loading, and augering
is one viable alternative for suppression of dust during open
coal mining. Windbreaks can effectively reduce visible dust
emissions from coal and overburden wind erosion. The control
problem is complicated by the lack of available technology for
the reduction of respirable dust (less than 7 pm).
The open coal mining industry is experiencing a high growth rate
(3.5% per year) primarily because of rapid development of rich
-------
coal lands west of the Mississippi River. The open production of
raw coal will increase to 312 x 106 metric tons in 1978. Dust
emissions are expected to increase proportionately because there
are no signs of control technology, if available, being applied
to this industry. The growth factor for the industry (1978 emis-
sions/1972 emissions) is 1.23.
-------
SECTION 3
SOURCE DESCRIPTION
PROCESS DESCRIPTION
Emission Sources
Open mining of coal involves withdrawing and winning coal from
surface or near subsurface coal deposits. In 1972, 263 x 106
metric tons, or nearly 50% of the raw coal produced in the
United States, was obtained by open mining (1). Two methods are
used in open coal mining: the first and most common is strip
mining; the second is auger mining. Strip mining, also known
as opencast mining, accounted for 95% of the surface-mined raw
coal produced in 1972 (1). Auger mining is more correctly
termed a secondary or auxiliary method because it is utilized
to extract coal where stripping operations become uneconomical.
This method accounted for the remaining 5% of the surface-mined
raw coal produced in 1972 (1) .
Strip mining is used in all 23 of the open coal mining states; '
auger mining is utilized in 8. In 1972, there were 2,309 strip
mining operations and 574 auger mining operations in the
United States (1). The average capacity of strip mines is
107.6 x 103 metric tons (1972) (1). Although less than 10% of
the strip mines had capacities over 181 x 103 metric tons, they
accounted for 70% of the 1972 strip production. The average
capacity of the auger mines is 24,600 metric tons (1972) (1).
The 90% of the auger operations with capacities less than
50 x 103 metric tons accounted for 54% of the 1972 auger coal
production.
The United States Bureau of Mines has defined the terms "strip
mining" (open-cast mining) and "auger mining" (2). These defini-
tions are presented in Appendix A. Auger mining is a straight-
forward coal mining method, and techniques do not vary across
the United States. Conversely, strip mining techniques vary
(1) 1974 Keystone Coal Industry Manual. G. F. Nielsen, ed.
McGraw-Hill, Inc., New York, New York, 1974. 859 pp.
(2) A Dictionary of Mining, Mineral, and Related Terms.
P. W. Thrush, ed. U.S. Department of the Interior, Washing-
ton, D.C., 1968. 1269 pp.
-------
widely depending on the characteristics of the coal seam deposits.
Appendix A summarizes the various strip mining techniques that are
practiced, and describes the current equipment utilized in both
strip and auger coal mining.
The differences in strip mining techniques are defined by the
types and combinations of equipment used in the mining operation.
The relationship between emissions and the different mining
methods must be reconciled. Although entire mining operations
may vary from one region of the country to another, they share
common unit operations. Unit operations are defined as distinct
and self-contained processes which are used to perform the exca-
vation and/or transport functions involved in coal mining. Unit
operations in the mining sense are construed as subprocesses in-
volving one or more items of equipment. Table 1 classifies unit
operations into the basic functions, and lists the equipment
normally associated with each. Figure 1 depicts the unit opera-
tions of open coal mining as they relate to the overall mining
process.
TABLE 1. UNIT OPERATIONS CLASSIFICATION FOR
OPEN COAL MINING IN THE UNITED STATES
Unit operation
Materials handled
Class
Function
Prime movers
Drilling
Overburden stripping
Coal loading
Coal transport/unloading
Blasting
Coal augering
Reclamation
Coal, overburden Primary operation
Overburden Primary operation
Coal
Coal
Coal, overburden
Coal
Overburden
Primary operation
Primary operation
Primary operation
Secondary operation
Secondary operation
Excavation
Excavation
Excavation
Transport
Excavation
Excavation
Excavation and
transport
Rotary drill
•i • a ^ -i a
Dragline, power shovel,
bucket wheel excavator,
tractor-scraper, bulldozer.
loading shovel, front-end
loader
Bulldozer, loading shovel,
front-end loader , ^ power
broom
Haul truck
Explosives
Auger
3
Dragline, tractor-scraper,
bulldozer,3 front-end
loader, grader
Denotes major equipment type in specific unit operation.
Emissions of dust occur during each of the unit operations. The
emission sources are comprised of the five primary and two secon-
dary unit operations shown in Table 1, and wind erosion.
Source Composition
Coal and overburden, the emissions source, are exceedingly com-
plex, widely variable entities.
-------
CONTINUE DRILLING UNTIL GEOLOGIC CHARACTER AND
ECONOMIC EXTENT OF RESERVES ARE KNOWN
1.
CONCURRENT EXPLORATORY
DRILLING
PRIME MOVER
ROTARY DRILL
•
UNFAVORABLE
2.
OVERBURDEN STRIPPING
PRIME MOVERS
DRAGLINE
POWER SHOVEL
BUCKET WHEEL EXCAVATOR
TRACTOR-SCRAPER
BULLDOZER
LOADING SHOVEL
FRONT-END LOADER
OPTIONAL SUBOPERATIONS
NOTE: ASSOCIATED UNIT OPERATIONS AND ADDITIONAL
INFORMATION ARE SHOWN IN TABLE 1.
C END CYCLED)
Figure 1. Open coal mining cycle of events
and associated unit operations.
There are four major ranks of coal: 1) lignite, 2) bituminous,
3) subbituminous, and 4) anthracite (3). In 1972, anthracite
accounted for less than 1.2% of the coal used in the United
States (2, 4) and only 2% of the surface-mined coal of all
ranks (1). Therefore, anthracite will not be considered in this
report.
(3) A.S.T.M. Standards on Coal and Coke. ASTM Designation
D 388-38, American Society for Testing and Materials,
Philadelphia, Pennsylvania, September 1948. p. 80.
(4) Minerals Yearbook, 1972; Volume I: Metals, Minerals, and
Fuels. U.S. Department of the Interior, Washington, D.C.,
1974. 1370 pp.
-------
The chemical and physical properties of coal vary widely between
deposits, seams in the deposits, and within sections of the seam
strata. Typical chemical analyses of certain U.S. coals of var-
ious ranks are listed in Table 2. The major elements and compo-
nents in coals are carbon, hydrogen, oxygen, sulfur, nitrogen,
and ash. The variability in ash content of coals is important
from a respirable dust viewpoint. The free silica content in
coal is directly related to ash content (5). From Table 2 it can
be seen that the ash content varies from 3.0% to 11.2%. In addi-
tion to the major elements, there exist a myriad of trace ele-
ments. Brown, Jacobs, and Taylor have studied trace elements in
coal and their data are presented in Table 3 (6). The crustal
abundance of selected elements, which refers to the concentration
of trace elements in the overburden, is also included (7).
TABLE 2. ANALYSES OF SELECTED COALS OF VARIOUS RANKS (5)3
("As received" basis)
Proximate analysis, %
b
Rank
Bituminous :
Low-volatile
Medium-volatile
High-volatile A
High-volatile A
High-volatile B
High-volatile B
High-volatile C
High-volatile C
State
West Virginia
West Virginia
Pennsylvania
Kentucky
Ohio
Kentucky
Illinois
Indiana
Seam
Pocahontas No. 3
Sewell
Pittsburgh
Elkhorn
Middle Kittanning
No. 6
No. 2
No. 6
Mois-
ture
3.5
3.1
2.6
3.1
8.2
7.2
12.1
12.4
Volatile
matter
18.2
25.0
30.0
35.0
36.1
39.8
40.2
36.6
Fixed
carbon
74.4
66.8
58.3
58.9
48.7
48.8
39.1
42.3
Ash
3.9
5.1
9.1
3.0
7.0
4.2
8.6
8.7
Car-
bon
84.0
76.6
79.2
68.4
71.5
62.8
63.4
Ultimate analysis.
Hydro-
gen
4.8
5.2
4.7
5.6
5.8
5.9
5.7
Oxy-
gen
5.6
6.2
10.0
16.4
14.3
17.4
18.6
Sul-
fur
0.6
1.3
1.3
0.6
1.2
2.6
4.3
2.3
%
Nitro-
gen
1.1
1.6
1.5
1.4
1.6
1.0
1.3
Heating
value ,
MJ/kg
33.8
33.2
31.6
33.2
28.3
30.1
26.7
26.5
Subbituminous:
Subbituminous A or high-
volatile bituminous C Wyoming Uncorrelated 16.5 34.2 38.1 11.2
Subbituminous B Wyoming Monarch 23.2 33.3 39.7 3.8
Subbituminous C Wyoming Uncorrelated 24.6 27.7 39.9 7.8
54.6
6.4 33.8
2.1
0.4
1.1
1.0
22.6
21.9
20.0
Lignite :
Lignite
North Dakota Beulah 34.8 28.2 30.8 6.2 42.4 6.7 43.3 0.7 1.7 16.8
Blanks indicate data not reported in reference.
According to A.S.T.M. method of classification.
(5) Chemical Engineers' Handbook, Fourth Edition. J. H. Perry,
ed. McGraw-Hill Book Company, New York, New York, 1963.
1650 pp.
(6) Brown, R., M. L. Jacobs, and H. E. Taylor. A Survey of the
Most Recent Applications of Spark Source Mass Spectrometry.
American Laboratory, 4(11):29-40, 1972.
(7) Abernethy, R. F., M. J. Peterson, and F. H. Gibson. Spectro-
chemical Analyses of Coal Ash for Trace Elements. Bureau of
Mines RI-7281, U.S. Department of the Interior, Washington,
D.C., July 1969. 30 pp.
-------
TABLE 3. CONCENTRATIONS OF TRACE ELEMENTS IN COAL
Element
Aluminum
Arsenic
Barium
Bismuth
Bromine
Boron
Cadmium
Calcium
Cerium
Chlorine
Chromium
Cobalt
Copper
Fluorine
Gallium
Germanium
Iodine
Iron
Lanthanum
Lead
Magnesium
Manganese
Molybdenum
Neodymium
Nickel
Niobium
Phosphorus
Potassium
Praseodymium
Rubidium
Samarium
Scandium
Selenium
Silicon
Silver
Sodium
Strontium
Sulfur
Tellurium
Titanium
Uranium
Vanadium
Yttrium
Zinc
Zirconium
Crustal
ppm in abundance (7) ,
Coal (6) ppm
Major
0.30
69
0.2
0.30
42
0.19
4,000
13
130
4.5
2.3
25
5.7
8.7
0.33
0.20
1,600
5-8
3.9
4,500
30
3.0
8.3
2.7
20
380
410
4.7
3.0
1.7
1.3
0.32
Major
0.22
5,000
100
6,100
0.25
620
1.9
12
7.7
10
76
Major
1.8
425
0.2
10.0
60
100
25
55
15
1.5
30
13
950
1.5
28
75
20
90
22
Major
375
135
33
70
165
Blanks indicate data not reported in
reference. A
-------
The overburden is composed primarily of soil and minerals (rock).
Sand, silt, and clay are the basic constituents of soil. Soil
categories and the defined particle size ranges of soils are
shown in Figure 2 (8). This discussion will be limited solely
to hazardous components of rock and soil, namely siliceous
materials.
Both soil and rock contain amounts of free silica, which occurs
in soils mainly in the form of quartz, Si02 (9, 10). Quartz
silica is found in alluvial soils, various types of sedimentary
rocks, and residual crystalline rocks. Free silica occurs as
opal (including opal pseudomorphic afterplant cells -- phytol-
iths), chalcedonite, agate, flint, chert, and cristobalite, which
is predominant in the lavas of the San Juan coal district of
Colorado (2) . It is also found in the form of amorphous sheets
and as aggregates with amorphous iron and aluminum oxide gel.
Igneous rock, shale, or sandstone is frequently encountered in
surface coal mining. A typical representation of coal-bearing
strata of the Western United States is shown in Figure 3 (11).
Igneous rock contains an average of 12% free silica as quartz
(12), shale averages 22.3%, and sandstone averages 66.8%.
There is no distinct separation of coal and overburden in surface
coal mining. Figure 3 shows that coal seams are stratified.
Thus, mining produces a composite of varying amounts of coal and
overburden.
(8) Brunner, D. R., and D. J. Keller. Sanitary Landfill Design
and Operation. Report SW-65ts, U.S. Environmental Protec-
tion Agency, Washington, B.C., 1972. p. 16.
(9) Jahr, D. J. Proposed Threshold Limit Values for Dusts Con-
taining Free Silica. Staub Reinhaltung der Luft (in
English), 33:86-90, February 1973.
(10) Chemistry of the Soil, Second Edition. F. E. Bear, ed.
Reinhold Publishing Corporation, New York, New York, 1965.
502 pp.
(11) Shoemaker, J. W., E. C. Beaumont, and F. E. Kottlewski.
Strippable Low-Sulfur Coal Resources of the San Juan Basin
in New Mexico and Colorado. Memoir No. 25, New Mexico
Bureau of Mines and Mineral Resources, Socorro, New Mexico,
1971.
(12) Foth, H. D., and L. M. Turk. Fundamentals of Soil Science/
Fifth Edition. John Wiley & Sons, Inc., New York, New York,
1972. 442 pp.
10
-------
100
100 90 80 70 60 50 40 30 20 10
SIEVE OPENINGS IN INCHES
3 2 l'/2 i 3/< 'A 3/e
SAND - 2.0 TO 0.05mm DIAMETER
SILT - 0.05 TO 0.002mm DIAMETER
CLAY - SMALLER THAN 0.002mm DIAMETER
COMPARISON OF PARTICLE SIZE SCALES
U.S. STANDARD SIEVE NUMBERS
4 10 20 40 60 200
n
USDA
uses
1 1 1 1 1 1 1
GRAVEL
GRAVEL
Coarse | Fine Coa
Hill I i I i linn i i
1 II 1 1 1 1
1 1 1
SANO
Veryl 1
coarsep0"6! Med
Fine
__ SIIT CLAY
Tory" 3ILI l-LAT
fine
SAND
rse| Medium | Fine
1 1 III
SILT OR CLAY
II III II
100 50
10
0.05 0.02 0.01 0.005 0.002 0.001
0.5
0.074
GRAIN SIZE, mm
Figure 2. Textural classification chart (U.S. Department
of Agriculture) and comparison of particle
size scales (8).
11
-------
Meters
0
3.0-
6.1-
9.2-
12.2-
15.2-
18.3-
21.4-
24.4-
27.4-
30.5-
33.6-
36.6-
39.6-
SOIL, BROWN, SANDY
SHALE, GRAY WEATHERED
SANDSTONE, ORANGE
SHALE, GRAY, YELLOW, HIGHLY WEATHERED
SHALE, DARK GRAY
SANDSTONE, GRAY, VERY FINE-GRAINED, TR.
SANDSTONE, LIGHT GRAY, VERY FINE-GRAINED
COAL
SHALE, BROWN-GRAY, GRAY
SHALE, GRAY, SANDY
SHALE, GRAY
SHALE, BROWN
COAL
SHALE, BROWN
SHALE, GRAY, BROWN, SANDY
SANDSTONE, GRAY VERY FINE-GRAINED,
CLAY CEMENTED
SANDSTONE, GRAY VERY FINE-GRAINED,
STREAKS OF SHALE
SHALE, GRAY SANDY
SHALE, GRAY GREEN, BROWN, SANDY
SHALE, GRAY, BLUE-GREEN, SANDY
SHALE, BROWN
COAL
45.8-
48.8-
54.9-
58.0-
61.0-
64.0-
67.1-
70.2-
73.2-
76.2-
SHALE, BROWN
SANDSTONE, GRAY VERY FINE-GRAINED,
CLAY CEMENTED
SHALE, GRAY
COAL
SHALE, GRAY, GRAY-GREEN
SANDSTONE, WHITE, FINE-GRAINED
SHALE, BROWN
COAL
COAL, STREAKS OF SHALE, LIGHT BROWN
SHALE, BROWN-BLACK, CARBONACEOUS
COAL
SHALE, BROWN-BLACK, CARBONACEOUS
COAL
SHALE, BROWN
SHALE, GRAY
SANDSTONE, GRAY VERY FINE-GRAINED,
SILTY
SHALE, GRAY, LOCALLY SANDY
79.3-
Total Depth =80.2m
Figure 3. Typical Western U.S. coal-bearing strata (11).
12
-------
Coalbed gas is emitted to the atmosphere during the mining opera-
tion. The primary constituents are methane (63% to 99%), carbon
dioxide, and trace amounts of C2_5 hydrocarbons (13, 14). As
coal weathers in mined-out portions of the workings, it slowly
oxidizes to CO and carbon dioxide (C02).
Explosive detonations represent another source of atmospheric
emissions. The predominant blasting agent in surface mining is
ANFO (ammonium nitrate and fuel oil) (15-17). ANFO accounted
for over 90% of the 431 x 103 metric tons of explosives used by
the coal industry in 1972 (17). A typical blasting mixture con-
sists of 94.5% by weight ammonium nitrate (NIUNOa) and 5.5% by
weight fuel oil. Toxic byproducts of the explosive reaction are
CO, nitrous oxide (NO), and nitrogen dioxide (NOa) fumes (18).
FACTORS INFLUENCING EMISSIONS
Open coal mining is a complex emissions source with respirable
dust emissions emanating from seven possible unit operations
within the mine (see Table 1) plus windblown dust as a result of
mining activity. This section identifies the parameters which
influence the generation of respirable dust from wind forces and
from each of the seven unit operations. Respirable dust is the
only pollutant type considered in the study of open coal mining.
Minor emission sources and the reasons for their exclusion are
discussed in Section 4.
(13) Kim. A. G. The Composition of Coalbed Gas. Bureau of Mines
RI-7762 (PB 221 574), U.S. Department of the Interior,
Washington, D-C., May 1973. 13 pp.
(14) Krickovic, S., and C. Findlay. Methane Emission Rate Stu-
dies in a Central Pennsylvania Mine. Bureau of Mines
RI-7591 (PB 206 359), U.S. Department of the Interior,
Washington, D-C., 1971. 9 pp.
(15) Surface Mining, E. P. Pfleider, ed. American Institute
of Mining, Metallurgical and Petroleum Ingineers, Inc.,
New York, New York, 1972. 1048 pp.
(16) Woodruff, S. D. Methods of Working Coal and Metal Mines,
Volume 3. Pergamon Press, New York, New York, 1966. 571 pp.
(17) 1972 Census of Mineral Industries (SIC 1211) , Bituminous
Coal and Lignite. MIC72(P)-12A-1, U.S. Department of Com-
merce, Washington, D.C., April 1974. 7 pp.
(18) Chaiken, R. F., E. B. Cook, and T. C. Ruhe. Toxic Fumes
from Explosives; Ammonium Nitrate-Fuel Oil Mixtures. Bureau
of Mines RI-7867 (PB 233 496), U.S. Department of the Inte-
rior, Washington, D-C., May 1974. 29 pp.
13
-------
Emission Parameters for Wind Erosion of Mined Land
As wind blows across the surface of a coal mine, respirable par-
ticles consisting of coal and soil become entrained. The major
parameters governing respirable dust particle movement from open
coal mining surfaces are the size distribution of particles in
the soil and the local climatic factors (wind, moisture, tempera-
ture) . Minor parameters include the soil surface roughness, dis-
tance across the field, distance sheltered by barriers, and form
of vegetation on the surface. Woodruff and Siddoway (19) have
confirmed Chepil's original assumptions and experimental work on
the mechanisms describing the air entrainment of dust particles
of all sizes from soils. Jenne (20) summarized Chepil's
mechanisms of movement of individual particles on a soil surface
as: 1) sliding or rolling of particles along the surface (sur-
face creep); 2) movement by leaps and bounds (saltation); and
3) movement by airborne transport (suspension). The larger
particles (greater than 100 ym) are affected mostly by saltation
with some surface creep. Particles closer in size to the
respirable range (less than 50 ym) are readily dislodged, and
large volumes are carried into suspension by impacts from larger
grains moving in saltation (20). Impaction of larger particles
releases smaller adsorbed particles because the cohesive forces
are weakened.
Climatic factors, such as wind speed, temperature, and precipita-
tion, affect the respirable dust emissions from soil. Thorn-
thwaite (21) combined the effects of temperature and precipita-
tion into a single parameter called the precipitation-evaporation
index (P-E index). Under saturated soil moisture conditions
there are no respirable emissions at any wind speed. Neither
the functionality relating the climatic factors to the respirable
dust emission rate nor the exact mathematical functionalities
for each of the seven unit operations which follow are known.
Emission Parameters for Rotary Drilling
Rotary bit drills are used to bore holes in overburden and/or
coal (see Figure 11, Section 6). The holes are filled with an
(19) Woodruff, N. P., and F. H. Siddoway. A Wind Erosion Equa-
tion. Soil Science Society of America, Proceedings, 29(5):
602-608, 1965.
(20) Jenne, D. E. An Analysis of High Volume Particulate Samp-
ling Data in Benton, Franklin, and Walla Walla Counties of
Washington - 1970, 1973. Benton-Franklin-Walla Walla
Counties Air Pollution Control Authority, Hanford, Washing-
ton, June 1974. 37 pp.
(21) Thornthwaite, C. W. Climates of North America According to
a New Classification. Geographical Review, 21:633-655,
March 1931.
14
-------
explosive and shot. This unit operation involves a single equip-
ment type. The drill bit, which employs compressed air through
its hollow core to remove cuttings and to cool the bearings (15) ,
produces respirable dust. The rate of uncontrolled emissions is
influenced by the complex interaction of the rate of bore hole
descent, bulk moisture content of material worked, diameter of
bore hole, downthrust applied to the drill bit, amount of air
supplied to the bit, and size distribution of material in the
cuttings. The continuous comminution of particles by the shear-
ing action of the drill bit generates respirable emissions (less
than 7 ym).
Emission Parameters for Overburden Stripping
The unit operation of overburden stripping is simple in nature,
involving the removal of topsoil and consolidated or unconsoli-
dated material above the coalbed. However, seven different types
of equipment are utilized throughout the industry (see Table 1),
the dragline and the power shovel being the predominant types.
Although the equipment varies widely in physical appearance, it
performs the same function. The respirable emissions from each
equipment type are influenced by common parameters. The vari-
ables affecting the quantity of respirable dust emitted are bulk
moisture content of soil, size distribution of particles in the
undisturbed material, struck volumetric capacity,9 and the effi-
ciency of stripping, which accounts for variability in emission
rates between equipment types. The efficiency is inversely pro-
portional to cycle time per metric ton of material excavated.
The cycle time per metric ton for a given piece of equipment is
the time required to load, swing, and dump a quantity of mate-
rial. For example, the efficiency of stripping is lower for a
dragline than for a stationary front-end loader of comparable
size because the dragline has a longer cycle time (15).
Emission Parameters for Coal Loading
Coal loading entails the removal and dumping of coal from the
exposed coal seam. It is a complex unit operation requiring four
types of equipment; the loading shovel and front-end loader are
predominant (see Table 1). The generation of respirable dust
from this operation is a function of the coal's brittleness
(commonly called the Hardgrove Grindability) and moisture con-
tent, size distribution of loosened coal, efficiency of loading
(similar to efficiency of stripping overburden), and the struck
volume capacity of the loading machine. The Hardgrove Grindabil-
ity Index of coal is a number between 0 and 100 showing the rela-
tive hardness or the friability of coal in relation to a standard
coal with a grindability index of 100 (2) .
The capacity of a mine car, tram, hopper, or wagon to the flat
surface at the edges (2).
15
-------
Emission Parameters for Coal Transport/Unloading
This single equipment type unit operation consists of trucking
the coal to the dump site (usually located near the mine tipple).
Emissions of respirable dust are generated by the truck tires on
the haul road en route to the tipple and back to the loading
point, and by the dumping of coal at the mine tipple. Wind
erosion of the coal in the truck en route to the mine tipple is
insignificant (22). The respirable emissions due to vehicular
movement on the unpaved dry haul roads are influenced by vehicle
speed, vehicle dimensions, number and width of the wheels, parti-
cle size distribution and moisture content of the unpaved road
surface, and distance of unpaved road round trip from loading
point to tipple.
Respirable dust is also generated during unloading of the coal at
the tipple. The emissions from coal unloading are a function of
the same factors as those that affect loading emissions with the
exception of the unloading efficiency parameter. The unloading
efficiency term is absent because only trucks are used in this
unit operation. The influencing parameters for coal unloading
are the struck volume of the coal truck, moisture content of the
coal, Hardgrove Grindability, and the size distribution of coal
within the truck.
Emission Parameters for Blasting Coal and Overburden
Blasting is a separate and distinct unit operation which gener-
ates respirable dusts. It is employed to loosen overburden and/
or coal prior to removal. The mass emission rate for blasting
depends on the quantity of charge used, the number of holes
fired, the diameter of the holes, the average millisecond (ms)
delay time between hole firings, the bulk moisture content of the
soil or coal and the particle size distribution of the bulk soil
or coal (post blast). The millisecond delay time between hole
firings is an important parameter in predicting rock fragmenta-
tion characteristics. Langefors and Kilhstrom (23) report that
blasting delays less than 10 ms produce an abundance of small
rock fragments (less than 40 cm) while delays greater than 10 ms
produce large fragments. Delay time is included as a parameter
related to respirable dust mass emissions, because it is assumed
that the generation of respirable dust will be proportional to
the degree of fragmentation.
(22) Blackwood, T. R., and P. K. Chalekode. Source Assessment:
Transport of Sand and Gravel. Contract 68-02-1320, U.S.
Environmental Protection Agency, Research Triangle Park,
North Carolina. (Preliminary document submitted to the EPA
by Monsanto Research Corporation, November 1974.) 86 pp.
(23) Langefors, U., and B. Kihlstrom. The Modern Technique of
Rock Blasting. John Wiley & Sons, Inc., New York, New York,
1963. 405 pp.
16
-------
Emission Parameters for Auxiliary Operations - Coal Augering
The parameters governing horizontal augering into the remaining
highwall are similar to those of rotary drilling. This unit
operation involves a single equipment type, namely the single or
multiple coal auger. The auger, unlike the drill, supplies no
air to the auger tip to remove coal cuttings. Rather, the coal
is fed out of the hole with action similar to that of a wood-
boring drill. The factors influencing respirable dust emissions
are the rate of penetration into the coal seam, bulk coal mois-
ture, diameter of auger, number of augers, sidethrust applied to
auger, and the size distribution of coal resulting from augering.
Emission Parameters for Auxiliary Operations - Reclamation
Reclamation of strip-mined lands involves recontouring the
depleted open pit to specific state requirements. This operation
typically involves a variety of equipment types to smooth over
the displaced overburden spoil banks. The dragline-bulldozer
combination is chosen as representative of the industry since
it is used at over 50% of the mines. The dragline employed has
a lower capacity than those utilized in stripping. The smaller
dragline excavates the required fill material so that the bull-
dozer can level the mined workings. This method permits stra-
tegic placement of valuable topsoil. The emission rate for the
reclamation unit operation is thus a function of two equipment
types: bulldozer and dragline. As such, the parameters influ-
encing dust generation from overburden stripping by dragline are
directly applicable. The emissions from bulldozers are functions
of blade width, horsepower, bulk moisture content of soil, and
size distribution of particles in the soil.
GEOGRAPHICAL DISTRIBUTION
Surface coal mining occurs in 23 of the 48 conterminous states;
16 of these states produced over 95% of the strip-mined coal and
over 99% of the auger-mined coal in 1972. The 16 states are
listed in Table 4, which includes the 7 states that were not con-
sidered because of their low productivity (each state accounted
for less than or equal to 1% of the total production). The strip
mining method was predominant in the 16 states studied; 94% of
the surface coal was strip mined. Auger mining accounted for 6%
of the surface production. Kentucky was the leading producer of
surface coal in 1972. The combined tonnage of the second and
third largest producers, Ohio and Illinois, respectively, approx-
imately equaled that of Kentucky.
Figure 4 depicts P-E regions (U.S. Weather Bureau county group-
ings within states) that are major producers of surface coal. It
also indicates 1972 surface coal production by P-E region and
associated population density per region. The P-E regions were
chosen as geographical boundaries because climatic data are
organized on a P-E regional basis.
17
-------
TABLE 4. STATE PRODUCTION OF SURFACE-MINED COAL
BY PRODUCTION RANKING FOR 1972 (1)
(103 metric tons)
Rank
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
State
Kentucky
Ohio
Illinois
Pennsylvania
Indiana
West Virginia
Alabama
Wyoming
Virginia
Montana
New Mexico
North Dakota
Tennessee
Missouri
Texas
Arizona
Strip
tonnage
50,599
30,914
30,665
23,826
22,229
17,328
11,954
9,514
7,198
7,442
6,563
6,016
4,638
4,129
3,670
2,680
Strip
%
20.3
12.4
12.3
9.5
8.9
6.9
4.8
3.8
2.9
3.0
2.6
2.4
1.8
1.6
1.5
1.1
Auger
tonnage
8,089
563
0
492
0
2,702
44
0
1,905
0
0
0
255
0
0
0
Auger
%
57.3 '
4.0
0
3.5
0
19.2
0.3
0
13.5
0
0
0
1.8
0
0
0
Total
58,688
31,477
30,665
24,318
22,229
20,030
11,998
9,514
9,103
7,442
6,563
6,016
4,893
4,129
3,670
2,680
Total
%
22.3
11.9
11.6
9.2
8.4
7.6
4.5
3.6
3.4
2.8
2.5
2.3
1.9
1.6
1.4
1.0
Total of 16 highest
ranked states
239,365 95.8 14,050 99.6 253,415 96.1
The following states are not considered in this report
17
18
19
20
21
22
23
Total
Washington
Oklahoma
Colorado
Maryland
Kansas
Iowa
Arkansas
of states
ranked 17 to 23
2,
2,
2,
1,
1,
10,
364
301
224
302
113
453
381
138
0-
0.
0.
0.
0.
0.
0.
4.
9
9
9
6
4
3
2
2
0
0
0
59
0
0
0
59
0
0
0
0.4
0
0
0
0.4
2
2
2
1
1
10
,364
,301
,224
,361
,113
453
381
,197
0.
0.
0.
0.
0.
0.
0.
3.
9
9
8
5
4
2
1
9
In general, coal is surface mined in areas remote from popula-
tion concentration. Comparison of the location of surface mines
to population density by P-E region indicates that surface mining
occurs in regions with population densities as low as 0.48 per-
sons/km2 (western states) and in regions as high as 145 persons/
km2 (eastern states). The average population density for the
surface coal industry is 27 persons/km2.
18
-------
NOTE: UPPER FIGURES SHOW COAL
PRODUCTION; LOWER FIGURES
SHOW POPULATION DENSITY.
Figure 4. Coal production by P-E region
(1Q3 metric tons strip and auger)
and population density.
19
(continued)
-------
CEMTBM. I E,ST CBimAL [jji^nrnuu.
I PUINS
NOTE: UPPER FIGURES SHOW COAL
PRODUCTION; LOWER FIGURES
SHOW POPULATION DENSITY.
Figure 4 (continued)
20
-------
NOTE: UPPER FIGURES SHOW COAL
PRODUCTION; LOWER FIGURES
SHOW POPULATION DENSITY.
Figure 4 (continued)
21
-------
SECTION 4
EMISSIONS
SELECTED POLLUTANTS
Major Emissions
The emissions from surface coal mining consist entirely of fugi-
tive dusts, specifically coal dust and overburden dust. The
effects of long-term exposure to coal and overburden dusts are
not well documented for surface coal mines. In contrast, the
health hazards associated with each of these emission types in
related industries are well defined. The inhalation and reten-
tion of coal dust in the lungs of underground coal miners can
result in the development of pneumoconiosis (black lung disease)
(24-28). Pneumoconiosis, also known as potter's or miner's
asthma, can result in death by massive fibrosis of lung tissue
(2). While it is not implied that health hazards to surface
coal workers are comparable to those of deep coal miners, this
discussion will serve to illustrate the potential health hazard
(24) Cheng, L. Formation of Airborne-Respirable Dust at Belt
Conveyor Transfer Points. American Industrial Hygiene Asso-
ciation Journal, 34(12):540-546, 1973.
(25) Corn, M., F. Stein, Y. Hammad, S. Manekshaw, R. Freedman,
and A. M. Hartstein. Physical and Chemical Properties of
Respirable Coal Dust from Two United States Mines. American
Industrial Hygiene Association Journal, 34 (7):279-285, 1973.
(26) Sweet, D. V., W- E. Grouse, J. V. Crable, J. R. Carlberg,
and W. S. Lainhart. The Relationship of Total Dust, Free
Silica, and Trace Metal Concentrations to the Occupational
Respiratory Disease of Bituminous Coal Miners. American
Industrial Hygiene Association Journal, 35(8):479-488, 1974.
(27) Schlick, D. P. Respirable Dust Sampling Requirements Under
the Federal Coal Mine Health and Safety Act of 1969. Bureau
of Mines IC-8484, U.S. Department of the Interior, Washing-
ton, D.C., July 1970. 35 pp.
(28) Cheng, L., and P. P. Zukovich. Respirable Dust Adhering to
Run-of-Face Bituminous Coals. Bureau of Mines RI-7765, U.S.
Department of the Interior, Washington, D.C., 1973. 10 pp.
22
-------
to surface coal workers and the rationale behind the selection
of coal dust as one of the two characteristic pollutants.
The threshold limit value (TLV®) for coal dust ranges from
0.5 mg/m3 to 2.0 mg/m3 as defined by the ACGIH (29). The var-
iability of the TLV depends on the percent of quartz in the dust.
A TLV of 2.0 is used when the quartz (SiO2) content is less than
5.0% by weight. If the quartz content of the respirable dust is
greater than 5.0%, a TLV of 10/(% quartz + 2) is recommended.
The latter TLV is also applicable for quartz-predominating dusts.
The primary hazard of the dust generated from handling overburden
is its free silica content (quartz, cristobalite, tridymite,
etc.). The composition of the particulates emitted during over-
burden handling is displayed in Table 5. These data represent
overburden dusts from an Illinois strip mine. The predominantly
hazardous component, as in coal dust, is free silica as indicated
by the quartz levels. No fibrous constituents (asbestos, serpen-
tine quartz, etc.) were found in any of the dusts.
TABLE 5. OVERBURDEN DUST COMPOSITION FROM
AN ILLINOIS STRIP MINE
(wt %)
Element/
compound
Sample
1
Sample
2
Sample
3
Silicon
Iron
Aluminum
Calcium
Sodium
Magnesium
Titanium
Manganese
Chlorine
Sulfur
Potassium
Si02
(quartz)
5 to 10 5 to 10
4
8
2
0.
0,
5
2
10 to 15
10 to 15
16
0.5
4
2
0.5
0.09
10 to 15
10
20
5 to 10
2
6
0.8
0.5
0.8
4
10
23
(29) TLVs® Threshold Limit Values for Chemical Substances and
Physical Agents in the Workroom Environment with Intended
Changes for 1973. American Conference of Governmental In-
dustrial Hygienists, Cincinnati, Ohio, 1973. 94 pp.
23
-------
The prolonged inhalation of dusts containing free silica may
result in the development of a disabling pulmonary fibrosis most
commonly known as silicosis. The action of free silica on the
lungs results in diffuse, nodular fibrosis which is progressive
and may continue to increase for several years after exposure is
terminated (2). The clinical onset of uncomplicated silicosis is
shortness of breath on exertion, sometimes accompanied by dry
cough. Where the disease advances, the shortness of breath be-
comes more acute and the cough more troublesome. Further pro-
gress of the disease results in marked fatigue, loss of appetite,
pleuritic pain, and total incapacity to work. Extreme cases may
eventually result in death from destruction of the lung tissues.
The ACGIH has suggested a TLV of 10/(% quartz + 2) mg/m3 for res-
pirable dusts containing quartz in the form of free silica (29).
Cristobalite- and tridymite-containing dusts have values one-half
that calculated from the quartz formula.
Assuming that the biological effects of the composite dust (coal
+ overburden) are additive, a composite TLV may be defined (29).
For coal containing less than 5% by weight quartz, the TLV in
mg/m3 of the composite respirable dust is given by:
TLV
5.OX + (1-X )(Zi + 2.0)
Coal <5% Si02
10.0 (2)
where X = wt fraction of respirable coal dust in
composite dust
Zi = wt % of pure respirable quartz dust in
noncoal dust
If the coal contains more than 5% by weight quartz, the TLV of
coal dust becomes that of quartz-bearing dust. The composite TLV
is then:
TLV
10.0 (3)
X (Z2 + 2.0) + (1-X )(Zi + 2.0)
Coal >5% Si02
where Z2 = wt % of pure respirable quartz dust in coal dust
When toxic impurities (i.e., coal or Si02) do not represent more
than 1.0% by weight of the composite dust, the TLV becomes that
of an "inert" dust (10.0 mg/m3) and would be treated as total
particulates of criteria pollutants (29).
Minor Emission Sources
The specific emission sources excluded from this environmental
source assessment, because they were not considered to be
24
-------
characteristic of open coal mining, are discussed in this section.
Respirable particulates and gaseous emissions (NOx/ CO, and hy-
drocarbons) from diesel-powered equipment were not selected as
characteristic because these emissions constitute a mobile source
where control technology is generally available or in the process
of development.
Gaseous emissions from other operations were excluded. Examples
are toxic gases (NO, N02, CO) that are formed by the detonation
of ammonium nitrate-fuel oil mixtures (18). Trace quantities of
these gases were detected in confined quarters such as under-
ground mines (18). Open field sampling and chemical analyses
were performed to determine the presence of hazardous constitu-
ents (including NO, N02, and CO) in samples of gases from the
blasting unit operation. Results indicate that these compounds
are not present in measurable quantities. As a result, toxic
fumes from blasting are not considered an environmental hazard.
The hydrocarbons and other gases released from coal as it is
mined represent another gaseous emission source. These gases are
predominantly methane (98%) with traces (1 ppm to 20 ppm) of
ethylene, propane, propylene, butanes, pentanes, hydrogen, heli-
um, oxygen, and nitrogen (13, 14, 30). Thus, it is reasonable to
assume that all coalbed gas is pure methane. A survey conducted
in 1973 indicated that a total of 6.08 x 106 m3 of methane is
released from U.S. underground coal mines daily (30). Using the
total 1973 underground coal tonnage production of 273.5 x 106
metric tons, the emission ratio of methane per metric ton of coal
is about 3.9 kg/metric ton. Assuming that the production of
methane is the same for surface coal, a nationwide emission rate
of 31.3 g/s is estimated for the surface coal industry. This
emission rate constitutes 23% of the total mass emission rate
from the industry (as noted later in this section). However,
methane gas is hazardous only from the standpoint of asphyxiation
(TLV = 1,000 ppm) (29). Coalbed gas was therefore neglected as
an emission source because of the low hazard associated with it.
The severity associated with this gas was calculated for the
representative source (mean size coal mine) and was found to be
0.0033 (national emission burden of 0.0038% of total hydrocarbon
emissions).
The gases (CO and CO2) formed by the slow oxidation of coal as it
weathers in mined-out portions of the workings and in storage
piles are considered minor. Preliminary work has shown that
these gases can be neglected as an emissions source for coal
(30) Irani, M. C., et al. Methane Emission from U.S. Coal Mines
in 1973, A Survey. Supplement to Bureau of Mines IC-8558,
U.S. Department of the Interior, Washington, B.C., December
1974. 52 pp.
25
-------
storage piles near power plants (31). Exclusion of this emission
source is further justified because coal is seldom stored at
surface mines and does not remain uncovered for the length of
time necessary to generate measurable quantities of gas (31).
Particle Size Analysis
\
The particle size distribution of overburden dust was determined
from presurvey samples gathered during sampling at one mine.
Filters from high-volume samplers were observed using optical
microscopy techniques (32), and the number of particles in random
fields were counted. Results are shown in Figure 5. The log-
normal distribution indicates the presence of processes which
continuously comminute particles; i.e., unit operations. Parti-
cle sizing of coal dust was not performed.
100
1.0
o.i
OVERBURDEN
I 1 I I I I
Figure 5.
10 20 30 40 50 60 70 80 90 95 98 99
CUMULATIVE FREQUENCY, % of number
Particle size distribution of
overburden dust (log-normal).
(31) Blackwood, T. R., and R. A. Wachter. Source Assessment:
Coal Storage Piles. Contract 68-02-1874, U.S. Environmental
Protection Agency, Cincinnati, Ohio. July 1977, 84 pp.
(32) Blackwood, T. R., T. F. Boyle, T. L. Peltier, J. V.
Pustinger, and D. L. Zanders. Fugitive Dust from Mining
Operations - Appendix. Contract 68-02-1320, Task 10, U.S.
Environmental Protection Agency, Research Triangle Park,
North Carolina. (Final report submitted to the EPA by
Monsanto Research Corporation, September, 1975.) 65 pp.
26
-------
Emission Factors
Exact calculation of the state and national emission rates of
respirable dust presupposes knowledge of the emission rate for
every mine in the country. The large number of strip and auger
mines precludes the gathering of such data (23, 26). A method
was developed in this study to obtain estimated statistical emis-
sion factors from field sampling for each of the seven character-
istic unit operations and wind erosion (see Appendix B). The
emission factor is useful in predicting emission rates over large
areas. Multiplying the emission factors by appropriate weighting
factors yields the emission rate. A summary of the rounded emis-
sion factors developed is presented in Table 6. The wind erosion
emission factors were obtained from the methods presented by
Woodruff and Siddoway (18). Although the literature values com-
puted per state account for both respirable and nonrespirable
particle mass emissions, the values obtained can be considered
"worst case" estimates for respirable dust. The unit operation
emission factors were obtained solely from field sampling as no
data were available in the literature. Besides the methodology,
Appendix B summarizes the assumptions used to arrive at these
estimated emission factors. Error estimates given are at the 95%
confidence level.
TABLE 6. EMISSION FACTORS FOR OPEN COAL MINING
For unit operations For wind erosion
Unit No. of
operation samples
Drilling 4
Overburden stripping 6
Coal loading 4
Coal transport and
unloading 3
Blasting 2
Coal augering -c
Reclamation 4
Total
Emission 95% Emission
factor. Standard Confidence factor,
g/metrio ton deviation interval" State [ (g/s • Jtm2)103lb
1.6 0.63 1.0 Alabama
-c -c -c Arizona
2.0 1.4 2.3 Illinois
Indiana
5.4 2.8 7.0 Kentucky
4.28 0.13 ±1.6 Missouri
°'P "c ~° North Dakota
- New Mexico
Ohio
13 - - Pennsylvania
Tennessee
Texas
Virginia
West Virginia
Wyoming
7.47
56.2
11.7
6.05
7.47
11.7
52.0
56.2
7.47
7.47
11.7
89.0
7.47
7.47
56.2
Note.—Data may not add to totals due to independent rounding.
Estimate of the confidence interval from observed population standard deviation using "student t"
distribution.
Not included in total.
CNot applicable.
Estimated from drilling emission factor.
Total emission factor on a national basis.
Mass Emission Rates and Contribution to Total Air Emission
The statewide emission rate of respirable dusts from surface coal
mining was estimated from the unit operation emission factors
multiplied by the state annual coal production plus the state
acreage disturbed, multiplied by the wind erosion emission
27
-------
factor. A composition term was included to arrive at the emis-
sion rates for coal dust and overburden dusts. Samples of coal
mine dusts collected during field sampling indicate that the res-
pirable dust contains on the average 93% coal and 7% overburden
dusts. The emission rates can be expressed mathematically as:
6
Q.v = A.e.Xv. + 3.17 x 10~8 P.XV. Y" E. (4)
j•"• J J -^J J •"•J '^TI -L
where Q.^ = amount of respirable dust emitted from surface
coal mines of the jth coal state, g/s
for K = 1, Q.J = total respirable dust rate
for K = 2, Q-2 = respirable coal dust rate
for K = 3, Q. = respirable overburden dust rate
J 3
X . = composition of respirable dust in the jth coal
-^ state, weight fraction coal or overburden
for K = 1, X,. = 1.0
for
for
K =
K =
2,
3,
X
.
= 0.
93
ZD
X
3
j
= 0.
07
A. = number of acres of surface coal land disturbed
•^ per state per year, km2
P. = state annual coal production, metric tons/year
E. = emission factor for the ith unit operation,
g/metric ton coal
e. = emission factor for wind erosion in the jth
-^ state, g/s-km2
The rates of respirable particulate emissions of each type
(total, coal, and overburden) due to open mining of coal were
calculated from Equation 4 for each of the 16 major surface min-
ing states (j = 1 to 16) to arrive at the national loading. The
resulting state and national mass emission rates from open coal
mining are presented in Table 7. Coal dust is the major emis-
sion component, constituting 93% of the total emissions. The
total respirable dust rate for open coal mining is 114 g/s.
Table 8 shows the respirable dust rate as compared with the total
state and national particulate loadings. Open coal mining con-
tributes more than 0.1% of each state's particulate emissions
burden in Kentucky, North Dakota, West Virginia, and Wyoming; it
contributes less than 0.1% of the burden in each of the remain-
ing 12 states.
Table 9 shows the contribution to the national open coal mining
rate from the various unit operations and windblown sources with-
in surface mines. The unit operations of blasting, coal trans-
port/unloading, and coal loading account for over 85% of the
28
-------
to
TABLE 7. TOTAL EMISSION RATES OF RESPIR-
ABLE DUSTS FROM OPEN COAL MINING
BY STATE AND NATIONWIDE3
Total dust,
V
j Location g/s, K=l
1 Alabama
2 Arizona
3 Illinois
4 Indiana
5 Kentucky
6 Missouri
7 Montana
8 New Mexico
9 North Dakota
10 Ohio
11 Pennsylvania
12 Tennessee
13 Texas
14 Virginia
15 West Virginia
16 Wyoming
Total
Other states
Nationwide
5.13
1.18
13.15
9.39
25.07
1.82
3.61
2.86
2.70
15.88
10.55
2.15
1.70
3.91
8.73
4.13
109.8
4.26
114.06
Coal dust,
V
g/s, K=2
4.78
1.09
12.29
8.84
23.39
1.68
3.19
2.66
2.47
12.58
9.78
1.98
1.54
3.64
8.07
3.84
101.8
4.0
105.8
Overburden
dust, Q ,
g/s, K=3
0.35
0.09
0.86
0.55
1.68
0.14
0.42
0.20
0.23
3.3
0.77
0.17
0.16
0.27
0.66
0.29
8.00
0.26
8.26
TABLE 8. RATIO OF TOTAL EMISSION RATES OF
RESPIRABLE DUSTS FROM OPEN COAL
MINING TO TOTAL PARTICULATES,
STATE AND NATIONWIDE3
1
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
Total dust,
Location % , K=l
Alabama
Arizona
Illinois
Indiana
Kentucky
Missouri
Montana
New Mexico
North Dakota
Ohio
Pennsylvania
Tennessee
Texas
Virginia
West Virginia
Wyoming
Nationwide
0.013
0.051
0.036
0.040
0.145
0.028
0.042
0.088
0.108
0.028
0.018
0.017
0.009
0.026
0.129
0.173
0.019
Coal dust,
%, K=2
0.012
0.047
0.034
0.037
0.135
0.026
0.037
0.082
0.099
0.022
0.017
0.015
0.008
0.024
0.119
0.161
0.018
Overburden
dust,
%, K=3
0.001
0.004
0.002
0.003
0.010
0.002
0.005
0.006
0.009
0.006
0.001
0.002
0.001
0.002
0.010
0.012
0.001
Based on assumed emission factors.
Based on assumed emission rates.
-------
emissions, while overburden stripping, reclamation, and coal
augering account for less than 1% of the emissions of respirable
dust.
TABLE 9. CONTRIBUTION TO RESPIRABLE MINING DUST
EMISSIONS FROM EACH SOURCE WITHIN THE MINE
(percent of national mining total)
CoalOverburdenTotal
Source dust dust dust
Wind erosion
Drilling
Overburden stripping
Coal loading
Coal transport and
unloading
Blasting
Coal augering
Reclamation
1.6
5.8
0
14
40
30
1
0
1.6
5.8
0
0
0
0
0
0
3 '
12
0
14
40
30
1
0
National total 93 7 100
Based on assumed emission factors.
Data may not add to totals due to independent
rounding.
The emission factors (EjJ were estimated from field data as was
XKJ. Coal production rates per state, Pj, are those given in
Table 4 as reported by the United States Bureau of Mines (1).
Values for state land disturbed annually by surface mining, Aj,
were supplied in part by Paone, et al. (33), and partially by
estimates made using the average coal stripping ratio per state
and the associated production found in a recent United States
Bureau of Mines report (34). Sample calculations and all input
data are shown in Appendix C.
DEFINITION OF REPRESENTATIVE SOURCE
The representative surface coal mine is a single facility where
94% of the coal is mined via strip mining methods and 6% is mined
via coal augering (U.S. average, see Table 4). All surface
(33) Paone, J., J. L. Morning, and L. Giorgetti. Land Utiliza-
tion and Reclamation in the Mining Industry, 1930-1971.
Bureau of Mines IC-9642, U.S. Department of the Interior,
Washington, D.C., 1971. 148 pp.
(34) Strippable Reserves of Bituminous Coal and Lignite in the
United States. Bureau of Mines IC-8531, U.S. Department of
the Interior, Washington, D.C., 1971. 148 pp.
30
-------
mining facilities have common methods of extracting coal from the
ground; the sizes and amounts of equipment differ. It is there-
fore assumed that respirable dust emissions are directly propor-
tional to the size of the mine.
The lack of heterogeneity within the surface coal industry indi-
cates that a representative source may be defined by size of
mine. Based on the 2,225 strip coal mines operating in the
United States in 1972, the mean mine size was 108 x 103 metric
tons/yr. The mean was chosen instead of the most frequently
occurring size (i.e., the mode) for reasons which are illustrated
in Figures 6 and 7. The frequency of occurrence of mines of the
six defined size classes (U.S. Bureau of Mines) is shown in
Figure 6. Of the 2,225 mines, 44% fall into the class yielding
between 9 x 103 and 45 x 103 metric tons of coal per year. This
class produced only 10.3% of the total surface coal as shown in
Figure 7; 56% of the coal was produced by mines yielding more
than 450 x 103 metric tons/yr. The mean size lies between these
two extremes. Additionally, the mean size was chosen over the
mode because the mines would become larger to offset the cost of
control technology, should it be developed for surface coal min-
ing. This would change the skewed distribution shown in Figures
6 and 7 into a more normal Gaussian distribution.
The representative source mine of 108 x 103 metric tons has unit
operations to the extent predicted by the mean emission para-
meters indicated in Table 9. The distribution of average emis-
sions within the industry is an indication of activity. Thus,
13% of the activity within the representative mine is devoted to
drilling, and 13%, 38%, 32%, and 1%, are devoted to coal loading,
coal transport/unloading, blasting, and coal augering, respect-
ively. The average production weighted wind erosion emission
factor calculated from data in Table 6 is 0.019 g/s • km2 which
indicates that the representative mine is located in either
Illinois or Indiana.
The area of the representative mine is generally defined by its
production rate, stripping ratio, and life expectancy. The
representative mine has a life expectancy of 20 years based on
averages compiled by the United States Bureau of Mines (35). The
average stripping ratio is 13.6 m of overburden per meter of
coal. A relationship was developed which computes the average
mine size, expressed as:
A = 5.45 x 10~8 (T)(P)(SR) (5)
(35) Coal Analyses of Model Mines for Strip Mining of Coal in the
United States. Bureau of Mines IC-8535, U.S. Department of
the Interior, Washington, D.C., 1972. 115 pp.
31
-------
70
60
50
. 40
>-
o
a
£ 30
20
10
MEAN
103
104
105
SIZE, metric tons/yr
106
10'
Figure 6. Surface coal mine size frequency distribution.
70
60
50
o
P 40
20
10
MEAN
0 i i I t{~l l~jT I I I 1 It _ >,- JJ |^^^_^_ J__^_t__l_ At I II I
103 104 105 106
SIZE, metric tons/ yr
Figure 7. Surface coal mine production by
mine size (1972 tonnage basis).
32
-------
where A = total area of the mine, km2
T = life expectancy, yr
P = average annual coal production, metric ton/yr
S = stripping ratio, m/m
The representative mine has an area of 2.0 km2. The area mined
per year by the representative mine is 98.5 x 103 m2. Appendix C
contains the derivation of Equation 5.
SOURCE SEVERITY
The maximum severity from the representative open coal mine was
determined for each dust emission (coal, overburden, and total).
The severity is defined as the_time-averaged maximum ground level
concentration of a pollutant (xmax) divided by the primary stand-
ard, F. Using a severity model (36) based on Turner's dispersion
model (37) and an average wind speed of 4.5 m/s and class C sta-
bility (U.S. average), the following equation was determined for
total particulates from open sources:
Sp = mgX/ P = 4,020 Qp D-1'18^
where S = total particulate (<7 ym) severity from open
" coal mining (dimensionless)
Q = emission rate of particulate from represen-
" tative source, g/s
_ D = representative distance from source, m
X = time-averaged maximum ground level concen-
max, p tration of particulates, g/m3
F = primary standard for particulates, g/m3
P
The model for coa! dust (less than 5% quartz) severity is ex-
pressed mathematically as (36):
S = 1.58 x 105 Q D"1' 18Lf (7)
C C
(36) Blackwood, T. R. Final Report Outline of the Source Assess-
ment Document. Contract 68-02-1874, U.S. Environmental Pro-
tection Agency, Research Triangle Park, North Carolina.
(Report submitted by Monsanto Research Corporation, May
1975.) 16 pp.
(37) Turner, D. B. Workbook of Atmospheric Dispersion Estimates
Public Health Service Publication No. 999-AP-26, U.S.
Department of Health, Education, and Welfare, Cincinnati,
Ohio, 1969. 52 pp.
33
-------
where S = coal dust severity from open coal mining
(dimensionless)
Q = emission rate of coal dust from representative
source, g/s
Finally, the model for overburden dusts containing free silica
is (36):
S = 7.05 x 105 Q D-1>811+ (8)
where S = silica-containing overburden dust severity from
open coal mining (dimensionless)
Q = emission rate of silica-containing overburden
dust, g/s
Equation 7 was developed for coal containing the U.S. average of
3% free silica (TLV = 2 mg/m3); Equation 8 was developed for
overburden dust containing the U.S. average of 20% free silica
(TLV =0.44 mg/m3).
The first estimate of severity was made at the physical bound-
aries of the representative mine where the severity is highest
because of the inverse distance relationship. The representative
source had an area of 2.0 km2, and the representative distance
to the boundary was 792 m. Equation 4 was used to compute the
emission rates Qp, Qc, and Qo where these were as follows:
Q = 0.0455 g/s
Q = 0.0418 g/s
\*r
Q = 3.70 x 10~3 g/s
The severities computed for total dust, coal dust, and over-
burden were 1.0 x 10~3, 0.036, and 0.014, respectively.
34
-------
SECTION 5
CONTROL TECHNOLOGY
STATE OF THE ART
Emissions from open mining activities are generated from two
sources, mining unit operations and wind entrainment. Air pollu-
tion at surface mines is a facet of the coal industry for which
virtually no control technology or techniques have been estab-
lished. Air pollution control, except for mine refuse piles,
drills, and haul roads, has never been implemented.
Mine refuse piles are accumulations of wastes from the coal min-
ing operation. These wastes contain carbonaceous material which
is susceptible to spontaneous combustion. There are three
methods of control: 1) removal of oxygen, 2) lowering of kind-
ling temperature, and 3) removal of carbonaceous material.
These methods of control are accomplished, respectively, by
coating or otherwise shielding the pile from air currents, by
applying cooling processes, and by cleaning the refuse to remove
the carbonaceous matter. Piles are shielded from air currents
by layer piling, piling with clay, sealing with clay and fly ash,
digging out and backfilling, and using trenches for storage
piles (38).
When pile fires occur they are extinguished by flooding, blanket-
ing, slurry injection, compacting, loading out, and sealing.
Water and bulldozers also have been used to isolate the burning
sections. However, extinguishment can generate additional
pollutants.
Drilling of blast holes using compressed air is an example of an
equipment-related source of emissions. A variety of cyclones and
baghouses are available for control of dust. Dust control during
blasting is allied closely with control of the blasting practice.
Well-planned, delayed shots will result in complete combustion
of the explosives.
(38) Maneval, R. R. Recent Advances in Extinguishment of Burning
Coal Refuse Banks for Air Pollution Reduction. American
Chemical Society, Division of Fuel Chemistry, Preprints,
13(2):27-41, 1969.
35
-------
Emissions from wind entrainment are primarily generated from the
loading and hauling of the coal and overburden. Rubber-tired
equipment generates more dust than do crawler units. Asphalt
mixtures are applied at some facilities for two reasons: to de-
crease the haulage time of the trucks and to suppress the dust.
Most states enforce water spraying of haul roads to reduce dust
and improve operator safety.
Stockpiles are a source of wind-entrained emissions at surface-
mined sites. The size of these piles, however, is kept to a
minimum, with coal loaded onto the transport units as soon as
possible. Control techniques available are discussed in depth
in the document entitled, "Source Assessment: Coal Storage
Piles" (31).
FUTURE CONSIDERATIONS
Emissions from various sources in open mining may be controlled
by applying the research and development of related areas. The
"mechanical" dust created by the movement of equipment over the
soil and coal, along with the dust generated by the loading and
dumping of these materials, may be controlled by the application
of a "chemical" spray (39). The chemical spray consists of a
dilute water solution of a surfactant or other chemical agent.
Water will not wet coal dust because of the difference in their
surface tensions. If the surface tension of the water is
reduced by addition of a surfactant or other wetting agent, it
will then wet the dust. The spray solution is applied from
headers directed over the source of the emissions. This tech-
nology may be applied to the travel and handling operations of
the equipment; however, its cost-effectiveness in relation to
open mining activities has not been studied.
Coal loaded in trucks may generate dust. This source has been
controlled (40) by covering the material with tarpaulins or
spraying with a chemical agent. The dumping operation emits ad-
ditional dust which has been controlled through the use of en-
closures placed over the dump area. Application of these control
methods to open mining activities may also prove successful.
Wind entrainment generates fugitive dust from a variety of
sources within the mine area. Control may be accomplished by
good housekeeping procedures. Mine roads may be controlled by
(39) No More Coal-Dust Problem for Georgia Power. Power, 105(7)
184-185, 1961.
(40) Minnick, L. J. Control of Particulate Emissions from Zinc
Plants - A Survey. Journal of the Air Pollution Control
Association, 21 (4):195-200, 1971.
36
-------
coating with either water or an emulsified asphalt (41). Asphalt
should be used in areas where water may evaporate rapidly. As-
phalt is usually applied to "out of the pit" roads since its
effect on flotation and coal recovery may be adverse. Water
spray trucks may work well in the pit area. Roadways have been
coated with calcium chloride at underground mines, and this may
work satisfactorily at surface mines. The construction of berms,
the planting of suitable ground cover and windbreaks, erection of
fencing, and minimum disturbance of vegetation can shield areas
from wind entrainment (40). Cleaning of stripped rock by mechan-
ical or hand sweeping has also been applied.
In general, however, control technology development has not been
of serious concern to the surface mining industry.
(41) Herde, R. S. Dust Control on Mine Roads. Mining Congress
Journal, 51:90-92, July 1965.
37
-------
SECTION 6
GROWTH AND NATURE OF THE INDUSTRY
PRESENT AND EMERGING TECHNOLOGY
The popularity of any particular mining technique is illustrated
by the "metric tons per man-shift" production level. In 1960,
the average bituminous coal production was: 1) 20.8 metric tons/
man-shift for strip mining, 2) 28.5 metric tons/man-shift for
auger mining, and 3) 9.6 metric tons/man-shift for underground
mining (16). The growth of open (surface) mining since 1920 is
shown in Table 10.
TABLE 10. GROWTH OF SURFACE MINING (42)
Total coal
produced /
Year 10 6 metric tons
1920
1930
1940
1950
1960
1970
1972
597.6
487.1
464.7
508.4
394.0
555.7
546.6
Percent
surface
mined
1.7
4.2
9.7
24.1
31.7
43.9
48.9
Percent
deep
mined
98.3
95.8
90.3
75.9
68.3
56-1
51.1
There are three basic methods of stripping coal (16). In the
first, a single stripping shovel traveling on the exposed coal
seam digs and removes the overburden ahead of it and piles it in
the cut from which coal has previously been removed. In the
second, a single dragline traveling on a bench above the coal
strips overburden to widen the bench for its travel way for the
next cut and removes the highwall bench over which it has trav-
eled to expose the coal seam. In the third, a shovel and a drag-
line are used in tandem with both traveling on exposed coal. The
shovel, working ahead of the dragline, removes the lower bench
to expose the coal seam and piles the spoil in the cut from which
(42) Dials, G. E. , and E. C. Moore.
ment, 16(7):18-24, 1974.
The Cost of Coal. Environ-
38
-------
coal has previously been removed. The dragline removes the upper
portion of the overburden to form another bench and casts the
spoil behind the shovel. Numerous combinations of shovels, drag-
lines, bulldozers, scrapers, and other types of equipment are
used throughout the industry. Stripping methods are discussed
further in Appendix A.
There are two types of augering operations presently in use (16):
1) augering highwalls left by stripping operations, and 2) auger-
ing outcrop coal.
In planning an open mining activity, one of the first tasks is
testing the material to determine its specific characteristics.
Factors such as bank weight and volume (before excavation), loose
weight and volume (after excavation), density, and swell factor
are analyzed. Open mining operations then begin with the acqui-
sition of the land based on prior knowledge of surface topo-
graphy, overburden, seam characteristics, etc. Plant location is
then influenced by access to transportation, sufficient area,
refuse disposal sites, and shortest haulage distance to the
cleaning plant. The economics of open mining are ultimately
determined by the stripping ratio.
In mining coal, the value of the equipment used is directly re-
lated to its production potential. Machines are used to their
maximum effectiveness since this increases the standard of pro-
duction and decreases the manual labor costs. The machine that
will provide the greatest production at the lowest cost will
generally be the one selected for the job. Determination of the
production potential is based on the type of material to be
handled and the capabilities of the machine. Equipment charac-
teristics such as struck capacity, nominal heaped capacity, and
fill factor express the amount of material that the equipment
container will hold. Material is generally classified as easy,
medium, hard, and very hard, and the energy requirements of the
equipment must be correlated with the material classification.
These factors all govern the choice of the equipment described
below.
Shovels
Shovels are used for the removal, dumping, and loading of over-
burden and/or coal. The shovel has evolved from a very crude
device to a highly sophisticated piece of equipment. This has
resulted from the continual improvement in design and adherence
to the basic operating principles that resulted from the in-
creased demand for production. The main concern, therefore, is
the bucket, and everything is designed to promote its maximum
effectiveness.
Power shovels are classified by the "struck" capacities of their
buckets. Shovel buckets generally range in size from 14 m3 to
39
-------
107 m3 (15). Every bucket size has a corresponding "depth of
cut" which is the height of the material bank that will fill the
bucket. Shovels presently available make it possible to mine
deposits which could not previously be considered. To remove
the material, a powerful steam or electric motor is needed. The
larger shovels in use are generally electric or diesel-electric
(43). Most of the recently purchased shovels are electric be-
cause they are more economical and convenient to use than are
diesel-electric (44). Diesel-powered units are used where
greater mobility is required.
A shovel has an average equipment capability of 83%, with the
larger shovels being more efficient. Shovels are generally used
where the material is too rough for other prime movers. They
require little surface preparation, less labor, and exhibit a
longer operating time than other equipment (15). The shovel
works a cylindrical pattern of: 1) loading the bucket, 2) swing-
ing to a dump point, 3) dumping the load, and 4) swinging back
for the next cut (16) .
Draglines
Draglines are also utilized for the removal, dumping, and loading
of overburden and/or coal. They are designed to dig below the
level of the machine and must be placed on solid ground (45).
Draglines are used in the excavation of the "easy" to "hard"
material classes of overburden. Smaller units are generally
used for the loading of trucks since the larger units do not
have loading preceision. Buckets of the larger draglines can
cast the overburden at any point on a 6.28 rad circle.
As with shovels, dragline buckets are classified by their struck
capacities. These bucket capacities range from 0.3 m3 to 168 m3.
Draglines also follow a cylindrical pattern of: 1) dragging the'
bucket and filling, 2) hoisting and swinging to the dump point,
3) dumping the load, 4) lowering and swinging back the empty
bucket, and 5) casting the bucket for the next load (15).
Today, electric motors are used on draglines because they provide
greater power than other types, are easily controlled, and are
economical. Diesel-electric engines are utilized when greater
mobility is required. The smaller draglines rely solely on
diesel power for mobility.
(43) Marion Power Shovel Introductory Brochure. Marion Power
Shovel Company, Marion, Ohio, 1968.
(44) Tractors and Scrapers Versus Shovels and Trucks. Mining
Congress Journal. 52:42-45, January 1966.
(45) Carson, B. A. General Excavation Methods. F. W. Dodge
Corporation, New York, New York, 1961. pp. 96-122.
40
-------
Draglines have greater range and adaptability than other prime
movers. They will dig deeper box cuts (greater overburden), can
handle moist material, and are not restricted by the pit dimen-
sions. Because of location outside of the pit, the dragline is
not dependent on the floor quality and is safe from pit floodings
or landslides (45).
The size of draglines doubled between 1954 and 1966. This trend
is exemplified by the recent development of a dragline with a
168 m3 bucket which weighs 24 metric tons (46).
Bucket Wheel Excavators
Wheel excavators are elaborate machines that can be used only in
specialized situations. They are most successful in areas that
do not require blasting. Excavators can work continuously below,
above, or at the working level in tandem with belt conveyors
which economically transport the material. This lowers the cost
of the power required since it extends the discharge radius of
the unit (15).
Wheel excavators are unsatisfactory for the following reasons:
they exhibit a low operating efficiency; they have difficulty in
handling hard materials; they require extensive surface prepara-
tion; and they have less flexibility than the draglines or
shovels (15). In addition, they require a higher capital cost
and demand a greater labor force than do other excavators.
Front-end Loaders
Front-end (F-E) loaders (see Figure 8) are used at almost all
mining activities because of their production capability, versa-
tility, and adaptability.
PISTON FOR BUCKET ROTATION
BUCKET
ENGINE
LIFTING PISTON
Figure 8. Front-end loader.
(46) Big Muskie: King of the Giants. Coal Age, 74(12):50-61
1969.
41
-------
The F-E loader was originally a modified tractor with arms and a
bucket attached, but it now has a specially designed frame.
Steady improvements in design have corresponded with the accept-
ance of the F-E loader. It is well suited to the handling of
stockpiled material or well-blasted rock. When equipped with
rubber tires, it is an efficient haulage unit for short dis-
tances.
Bucket capacities range from 0.4 m3 to 12.2 m3. F-E loaders with
buckets greater than 3 m3 are all tire mounted. Crawler-mounted
units are used on difficult surfaces, but they are slow moving
and are used to transport material only over short distances.
The rubber-tired units are faster and more agile.
Scraper
Scrapers (see Figure 9) are available in a variety of designs and
capacities that can be used in any mining system. They are gen-
erally used for handling material in refuse or stockpiles (47).
Scrapers are presently available in four models: hoe, box,
crescent, and folding (48). The digging and hauling qualities of
a unit are functions of its weight, blade curvature, and harnes-
sing of the rope pull which is the only adjusting piece of equip-
ment on the machine.
EJECTOR
PUSHER BLOCK
BOWL-/ CUTTING EDGE-^ LAPRON
Figure 9. Scraper (self-propelled unit).
Scrapers are used as auxiliary equipment when overburden is to be
moved hundreds of meters. This is done when the soil is loose or
relatively soft, as in the upper portion of the overburden.
Scraper operation is complex and cyclical, requiring the coor-
dination of man and machine. Scrapers are rated by their struck
and/or heaped capacity.
(47) Young, G. I. Elements of Mining. McGraw-Hill Book Company,
New York, New York, 1946. 414 pp.
(48) Wetson, J. A. Guide to the Selection of Mine Scrapers.
Engineering and Mining Journal, 168:173-175, January 1967.
42
-------
The selection of a scraper depends on the type of tractor that
will pull the unit. The self-propelled unit shown in Figure 9
provides vastly improved haulage speeds. Four-wheel drive units
are the newest innovation. They can be used on steeper grades
and they provide greater pulling power than do the older types.
Bulldozers
A bulldozer (see Figure 10) is also an evolution of the tractor,
with a curved steel blade attached to the front by pivotal arms.
The blade can be lowered, raised, or tilted by means of adjoining
cables or rams.
LIFT ARM
BLADE
EDGE OR KNIFE
PUSH ARM
Figure 9. Scraper (self-propelled unit).
Bulldozers are currently used for numerous activities such as
land clearing and preparation, maintenance and clearance of haul-
age roads, cleanup for shovels and draglines, maintenance of
spoil piles, ripping and stump removal, and various other strip-
ping activities (49). Dozers are generally used when the soil
does not have to be pushed more than 100 m.
There are six types of dozers on the market: 1) straight bull-
dozers, 2) angle dozers, 3) tilt dozers, 4) push dozers, 5) U-
shaped dozers, and 6) other modifications (50). The main con-
trolling factor in the selection of equipment is the condition
and type of material being excavated. Dozers are available with
(49) Warren, P. J. Tractor Dozers Blaze the Trail. Rock Pro-
ducts, 66:84-86, 94-96, March 1963.
(50) Adler, Y., and H. E. Naumann. Analyzing Excavation and
Materials Handling Equipment. Research Division Bulletin
No. 53, Virginia Polytechnic Institute, Blacksburg,
Virginia, February 1970. 230 pp.
43
-------
crawlers or wheels. The crawlers are generally used for the rip-
ping, land clearing and preparation, and cleaning activities,
whereas wheeled dozers are used for spreading the overburden
because of their increased mobility and speed. Crawler tractors
are used on the harder soils where greater traction (strength) is
required to push material over short distances. Wheel dozers are
used if the material is loose and is to be pushed over long dis-
tances (51). Production rates of 230 m3/hr to 350 m3/hr can be
expected for wheeled dozers since they are faster and have more
frequent loadings. Crawler dozers have rates of 115 m3/hr to
185 m3/hr but are less costly than wheeled units since the latter
need to be heavier (52).
Recently developed bulldozers of the four-wheel drive, rubber-
tired version are more amenable to high production and have
better traction. The large crawler units were developed for use
as rippers, and they can be substituted for blasting in shales
and sandstones.
Coal Augers
Augering of coal is accomplished with either single or multiple
auger units that can dig up to 67 m deep and produce from 180 to
270 metric tons/day. Augering is performed on seams where there
is a constant pitch and no strains of interfacing material to
cause equipment breakage. It is done in a patterned manner which
effectuates the greatest removal of coal.
Drills
Drills presently in use are predominantly the rotary types (53).
Rotary drills use compressed air to remove the cuttings from bore
holes of 12 cm to 38 cm in diameter. The thicker the overburden,
the larger the diameter of the drill used and the fewer the holes
required. Newer drills have self-contained dust control appara-
tus as shown in Figure 11 (54). Tilt features are available that
enable angled and horizontal drilling to be performed when rocks
are near the surface.
(51) Rubber-Tired Dozer Was a Busy Rig. Roads and Streets,
102:165, November 1959.
(52) Rodonsky, J. Track and Wheels in the Open-Pit - Where Do
They Perform Best? Engineering and Mining Journal, 158:
87-89, April 1957.
(53) Guides for Successful Stripping. Coal Age, 67:186-205,
July 1962.
(54) Harwood, C. F., and T. P. Blaszak. Characterization and
Control of Asbestos Emissions from Open Sources. EPA-650/2-
74-090, U.S. Environmental Protection Agency, Research Tri-
angle Park, North Carolina, December 1974. 195 pp.
44
-------
CENTER LINE OF HOLE
AND ROTARY DRIVE
LAZY SUSAN
EXHAUST FAN
3,000cfm
ACCESS DOORS
36 BAGS SLY
TYPE BAG FILTER
HYDRAULIC
JACK
HINGED
REAR FLAP OF
RUBBER SKIRT
RUBBER
HYDRAULIC JACK-7 SKIRT
Figure 11. Rotary drill with dust control equipment (54).
The newer method of inclined drilling is gaining wider acceptance
in the industry due to its greater toe and back breakage, better
fragmentation, use of fewer explosives/metric ton small diameter
of holes required, and greater overburden throwing distances (16).
Automation of drills to speed up the process, to keep pace with
the increased tempo of mining production, has met with limited
success (55). Development of such drills is particularly needed
because of the lack of skilled manpower available for operation
of the drills presently in use.
Haulage Equipment
The size of haulage units may vary over a large range since the
units are matched to the capacity of the loading rigs. A general
rule of thumb in the industry is to use trucks having a capacity
which is four to five times that of the dipper capacity of the
loading units.
(55) Li, T. M. Rotary Drilling with Automated Controls - New
Force in Open-Pit Blast Hole Production. Coal Age, 79(8):
82-89, 1974.
45
-------
In applications where haulage roads are steep, individual elec-
tric drives are sometimes connected to each wheel. Engines up to
522 kW are common among haulage units, which are diesel powered.
Over the years, the cost of haulage has decreased as the size of
haulers and the quantity of coal hauled have increased. Fuel
consumption averages more than 1.85 x 10 3 m3/km. The increased
use of tandem-drive axle and dual rear wheels has cut the costs
and increased production. In addition, the use of paved haul
roads has cut down travel times and increased productivity.
Larger haulage units, up to 200 metric tons, are now being util-
ized, and the trend is toward even larger units.
Blasting
The most commonly used blasting explosive, ANFO, is a mixture of
ammonium nitrate and fuel oil, usually in the proportion of
454 kg of NH^NOa to 2.2 kg to 2.7 kg of fuel oil. At smaller
facilities the explosive is usually bagged, and the fuel oil is
poured over the bags at the drill site. Larger facilities have
mixing plants and the mixture is transported to the drill site
where it is either poured into the holes or blown in using com-
pressed air. Pneumatic loading of horizontal drill holes is a
new technique that may replace the need to hand or mechanically
tamp the charge (56). The holes are spaced according to their
size, the overburden thickness, and the type of rock.
A slurry blasting agent of ammonium nitrate, sodium nitrate, a
high explosive sensitizer, and water has recently been developed
which may replace ANFO.
INDUSTRY PRODUCTION TRENDS
Coal Development
The trend in the coal industry is to increase the open mining
proportion of production. The introduction of multiple-headed
augers has increased the production rate of auger mining. The
use of the "haulback" method of strip mining has made this method
of extraction more environmentally acceptable. With over 70% of
the nation's coal reserves lying in the western states, the
growth for this region is anticipated to extend into the 21st
century. Conventional equipment will be used to mine these re-
serves, but it will require larger booms for greater spoil reach.
With coal reserves growing, the demand for larger capacity mining
units has increased. Larger units are being introduced each year
(56) Murray, J. R., and J. W. Francis. Consol Tries Pneumatic
Bulk Loading of Horizontal Drill Holes. Coal Age, 79(1):
64-65, 1974.
46
-------
to cope with the increased amounts of rock and dirt that must be
removed. Despite the higher cost of larger units, the overall
cost for mining a cubic meter of overburden with them is lower
than that of the smaller machinery. Thus, over the years, the
average depth of overburden removed to expose coal seams will
steadily increase. Since most western coals are relatively low
in sulfur content and occur in thicker seams than in the east,
this area has become more environmentally and economically
attractive.
Growth Factor
The total annual surface coal production predicted for 1978 is
312 x 106 metric tons based on projections made by the National
Petroleum Council in 1973 (57). This forecast assumes a sus-
tained growth rate of 3.5% per year. The emissions are expected
to increase in proportion to the growth due to the assumed lack
of further control technology implementation. The growth factor,
defined as the ratio of 1978 emissions of respirable dust to 1972
emissions of respirable dust, is 1.23.
(57) U.S. Energy Outlook - Coal Availability. A Report by the
Coal Task Group of the Other Energy Resources Subcommittee
of the National Petroleum Council's Committee on U.S. Energy
Outlook, Washington, B.C., 1973. p. 287.
47
-------
REFERENCES
1. 1974 Keystone Coal Industry Manual. G. F. Nielsen, ed.
McGraw-Hill, Inc., New York, New York, 1974. 859 pp.
2. A Dictionary of Mining, Mineral, and Related Terms.
P. W. Thrush, ed. U.S. Department of the Interior, Wash-
ington, D.C., 1968. 1269 pp.
3. A.S.T.M. Standards on Coal and Coke. ASTM Designation
D 388-38, American Society for Testing and Materials,
Philadelphia, Pennsylvania, September 1948. p. 80.
4. Minerals Yearbook, 1972; Volume I: Metals, Minerals, and
Fuels. U.S. Department of the Interior, Washington, D.C. ,
1974. 1370 pp.
5. Chemical Engineers' Handbook, Fourth Edition. J. H. Perry,
ed. McGraw-Hill Book Company, New York, New York, 1963.
1650 pp.
6. Brown, R. , M. L. Jacobs, and H. E. Taylor. A Survey of the
Most Recent Applications of Spark Source Mass Spectrometry .
American Laboratory, 4(11):29-40, 1972.
7. Abernethy, R. F. , M. J. Peterson, and F. H. Gibson. Spec-
trochemical Analyses of Coal Ash for Trace Elements. Bureau
of Mines RI-7281, U.S. Department of the Interior, Washing-
ton, D.C., July 1969. 30 pp.
8. Brunner, D. R. , and D. J. Keller. Sanitary Landfill Design
and Operation. Report SW-65ts, U.S. Environmental Protec-
tion Agency, Washington, D.C., 1972. p. 16.
9. Jahr, D. J. Proposed Threshold Limit Values for Dusts Con-
taining Free Silica. Staub Reinhaltung der Luft (in
English), 33:86-90, February 1973.
10. Chemistry of the Soil, Second Edition. F. E. Bear, ed.
Reinhold Publishing Corporation, New York, New York, 1965.
502 pp.
48
-------
11. Shoemaker, J. W., E. C. Beaumont, and F. E. Kottlewski.
Strippable Low-Sulfur Coal Resources of the San Juan Basin
in New Mexico and Colorado. Memoir No. 25, New Mexico
Bureau of Mines and Mineral Resources, Socorro, New Mexico,
1971.
12. Foth, H. D., and L. M. Turk. Fundamentals of Soil Science,
Fifth Edition. John Wiley & Sons, Inc., New York, New York,
1972. 442 pp.
13. Kim. A. G. The Composition of Coalbed Gas. Bureau of Mines
RI-7762 (PB 221 574), U.S. Department of the Interior,
Washington, D.C., May 1973. 13 pp.
14. Krickovic, S., and C. Findlay. Methane Emission Rate
Studies in a Central Pennsylvania Mine. Bureau of Mines
RI-7591 (PB 206 359), U.S. Department of the Interior, Wash-
ington, D.C., 1971. 9 pp.
15. Surface Mining. E. P. Pfleider, ed. American Institute of
Mining, Metallurgical and Petroleum Engineers, Inc.,
New York, New York, 1972. 1048 pp.
16. Woodruff, S. D. Methods of Working Coal and Metal Mines,
Volume 3. Pergamon Press, New York, New York, 1966.
571 pp.
17. 1972 Census of Mineral Industries (SIC 1211), Bituminous
Coal and Lignite. MIC72(P)-12A-1, U.S. Department of Com-
merce, Washington, D.C., April 1974. 7 pp-
18. Chaiken, R. F., E. B. Cook, and T. C. Ruhe. Toxic Fumes
from Explosives; Ammonium Nitrate-Fuel Oil Mixtures. Bureau
of Mines RI-7867 (PB 233 496), U.S. Department of the Inte-
rior, Washington, D-C., May 1974. 29 pp.
19. Woodruff, N. P., and F. H. Siddoway. A Wind Erosion Equa-
tion. Soil Science Society of America, Proceedings, 29(5):
602-608, 1965.
20. Jenne, D. E. An Analysis of High Volume Particulate Sam-
pling Data in Benton, Franklin, and Walla Walla Counties of
Washington - 1970, 1973. Benton-Franklin-Walla Walla
Counties Air Pollution Control Authority, Hanford, Washing-
ton, June 1974. 37 pp.
21. Thornthwaite, C. W. Climates of North America According to
a New Classification. Geographical Review, 21:633-655,
March 1931.
49
-------
22. Blackwood, T. R., and P. K. Chalekode. Source Assessment:
Transport of Sand and Gravel. Contract 68-02-1320, U.S.
Environmental Protection Agency, Research Triangle Park,
North Carolina. (Preliminary document submitted to the EPA
by Monsanto Research Corporation, November 1974.) 86 pp.
23. Langefors, U-, and B. Kihlstrom. The Modern Technique of
Rock Blasting. John Wiley & Sons, Inc., New York, New York,
1963. 405 pp.
24. Cheng, L. Formation of Airborne-Respirable Dust at Belt
Conveyor Transfer Points. American Industrial Hygiene Asso-
ciation Journal, 34 (12):540-546, 1973.
25. Corn, M., F. Stein, Y. Hammad, S. Manekshaw, R. Freedman,
and A. M. Hartstein. Physical and Chemical Properties of
Respirable Coal Dust from Two United States Mines. American
Industrial Hygiene Association Journal, 34 (7):279-285, 1973.
26. Sweet, D. V., W. E. Grouse, J. V. Crable, J. R. Carlberg,
and W. S. Lainhart. The Relationship of Total Dust, Free
Silica, and Trace Metal Concentrations to the Occupational
Respiratory Disease of Bituminous Coal Miners. American
Industrial Hygiene Association Journal, 35 (8):479-488, 1974.
27. Schlick, D. P. Respirable Dust Sampling Requirements Under
the Federal Coal Mine Health and Safety Act of 1969. Bureau
of Mines IC-8484, U.S. Department of the Interior, Washing-
ton, D.C., July 1970. 35 pp.
28. Cheng, L., and P. P. Zukovich. Respirable Dust Adhering to
Run-of-Face Bituminous Coals. Bureau of Mines RI-7765, U.S.
Department of the Interior, Washington, D.C., 1973. 10 pp.
29. TLVs® Threshold Limit Values for Chemical Substances and
Physical Agents in the Workroom Environment with Intended
Changes for 1973. American Conference of Governmental In-
dustrial Hygienists, Cincinnati, Ohio, 1973. 94 pp.
30. Irani, M. C., et al. Methane Emission from U.S. Coal Mines
in 1973, A Survey. Supplement to Bureau of Mines IC-8558,
U.S. Department of the Interior, Washington, D.C., December
1974. 52 pp.
31. Blackwood, T. R., and R. A. Wachter. Source Assessment:
Coal Storage Piles. Contract 68-02-1874, U.S. Environmental
Protection Agency, Cincinnati, Ohio. July 1977- 84 pp.
50
-------
32. Blackwood, T. R., T. F. Boyle, T. L. Peltier, J. V.
Pustinger, and D. L. Zanders. Fugitive Dust from Mining
Operations - Appendix. Contract 68-02-1320, Task 10, U.S.
Environmental Protection Agency, Research Triangle Park,
North Carolina. (Final report submitted to the EPA by
Monsanto Research Corporation, September 1975.) 65 pp.
33. Paone, J. , J. L. Morning, and L. Giorgetti. Land Utiliza-
tion and Reclamation in the Mining Industry, 1930-1971.
Bureau of Mines IC-9642, U.S. Department of the Interior,
Washington, D.C., 1971. 148 pp.
34. Strippable Reserves of Bituminous Coal and Lignite in the
United States. Bureau of Mines IC-8531, U.S. Department of
the Interior, Washington, D.C., 1971. 148 pp.
35. Coal Analyses of Model Mines for Strip Mining of Coal in the
United States. Bureau of Mines IC-8535, U.S. Department of
the Interior, Washington, D.C., 1972. 115 pp.
36. Blackwood, T. R. Final Report Outline of the Source Assess-
ment Document. Contract 68-02-1874, U.S. Environmental Pro-
tection Agency, Research Triangle Park, North Carolina.
(Report submitted by Monsanto Research Corporation,
May 1975.) 16 pp.
37. Turner, D. B. Workbook of Atmospheric Dispersion Estimates.
Public Health Service Publication No. 999-AP-26, U.S.
Department of Health, Education, and Welfare, Cincinnati,
Ohio, 1969. 52 pp.
38. Maneval, R. R. Recent Advances in Extinguishment of Burning
Coal Refuse Banks for Air Pollution Reduction. American
Chemical Society, Division of Fuel Chemistry, Preprints,
13(2):27-41, 1969.
39- No More Coal-Dust Problem for Georgia Power. Power, 105(7):
184-185, 1961.
40. Minnick, L. J. Control of Particulate Emissions from Zinc
Plants - A Survey. Journal of the Air Pollution Control
Association, 21 (4):195-200, 1971.
41. Herde, R. S. Dust Control on Mine Roads. Mining Congress
Journal, 51:90-92, July 1965.
42. Dials, G. E., and E. C. Moore. The Cost of Coal. Environ-
ment, 16(7):18-24, 1974.
43. Marion Power Shovel Introductory Brochure. Marion Power
Shovel Company, Marion, Ohio, 1968.
51
-------
44. Tractors and Scrapers Versus Shovels and Trucks. Mining
Congress Journal. 52:42-45, January 1966.
45. Carson, B. A. General Excavation Methods. F. W. Dodge Cor-
poration, New York, New York, 1961. pp. 96-122.
46. Big Muskie: King of the Giants. Coal Age, 74(12):50-61,
1969.
47. Young, G. I. Elements of Mining. McGraw-Hill Book Company,
New York, New York, 1946. 414 pp.
48. Wetson, J. A. Guide to the Selection of Mine Scrapers.
Engineering and Mining Journal, 168:173-175, January 1967.
49. Warren, P. J. Tractor Dozers Blaze the Trail. Rock Pro-
ducts, 66:84-86, 94-96, March 1963.
50. Adler, Y., and H. E. Naumann. Analyzing Excavation and
Materials Handling Equipment. Research Division Bulletin
No. 53, Virginia Polytechnic Institute, Blacksburg,
Virginia, February 1970. 230 pp.
51. Rubber-Tired Dozer Was a Busy Rig. Roads and Streets,
102:165, November 1959.
52. Rodonsky, J. Track and Wheels in the Open-Pit - Where Do
They Perform Best? Engineering and Mining Journal, 158:
87-89, April 1957.
53. Guides for Successful Stripping. Coal Age, 67:186-205,
July 1962.
54. Harwood, C. F., and T. P. Blaszak. Characterization and
Control of Asbestos Emissions from Open Sources. EPA-650/2-
74-090, U.S. Environmental Protection Agency, Research Tri-
angle Park, North Carolina, December 1974. 195 pp.
55. Li, T. M. Rotary Drilling with Automated Controls - New
Force in Open-Pit Blast Hole Production. Coal Age, 79(8):
82-89, 1974.
56. Murray, J. R., and J. W. Francis. Consol Tries Pneumatic
Bulk Loading of Horizontal Drill Holes. Coal Age, 79(1):
64-65, 1974.
57. U.S. Energy Outlook - Coal Availability. A Report by the
Coal Task Group of the Other Energy Resources Subcommittee
of the National Petroleum Council's Committee on U.S. Energy
Outlook, Washington, D.C., 1973. p. 287.
52
-------
58. Stefanko, R., R. J. Ramani, and M. R. Ferko. An Analysis of
Strip Mining Methods and Equipment Selection. Office of
Coal Research R&D Report No. 61, Interim Report No. 7, U.S.
Department of the Interior, Washington, D.C., 29 May 1973.
131 pp.
59. 1972 National Emissions Report. EPA-450/2-74-012, U.S.
Environmental Protection Agency, Research Triangle Park,
North Carolina, June 1974. 422 pp.
53
-------
APPENDIX A
STRIP AND AUGER MINING TECHNIQUES FROM THE STANDPOINT
OF REGIONAL VARIABILITY
Strip (opencast) mining and auger mining are the two methods most
widely used for removing surface coal.
Strip mining consists of removing the overburden, extracting the
coal, and then replacing the overburden. When the overlying
material consists of earth or clay, it can be removed directly by
scrapers or excavators, but where rock is encountered it is
necessary to resort to blasting to prepare the material for
handling by the excavators. The usual method of working is to
extract the coal in a series of regular slices called cuts. The
length of each cut is governed by the limits of the area to be
worked. The width of the cut depends on the type of excavating
equipment available; for example, in the case of dragline exca-
vators the casting distance will be a determining factor. The
first operation is to make an initial cut, called the box cut,
into solid ground. Overburden from this cut has to be loaded
into vehicles and transported to a suitable dumping ground. The
exposed coal can then be excavated. Next, the overburden of the
second cut is deposited into the void of the preceding cut,
thereby exposing a fresh area of coal for excavation. This
system is repeated across the area to be worked, and the box cut
overburden is used to fill the void of the final cut (2).
Auger mining is a method often used by strip mine operators when
the overburden gets too thick to be removed economically. Large-
diameter, evenly spaced holes are drilled up to 61 m into the
coalbed by an auger. Like a bit used for boring holes in wood,
this consists of a cutting head with screwlike extensions. As
the auger turns, the head breaks the coal, and the screwlike
extensions raise it and dump it on an elevating conveyor; this,
in'turn, carries the coal to an overhead bin or loads it directly
into a truck. Auger mining is relatively inexpensive, and it is
reported to recover approximately 60% to 65% of the coal (2).
There are two broad strip coal mining techniques practiced in the
United States, contour mining and area mining. Both types can be
used only if the overburden thickness is less than approximately
61 m (the limit of current equipment). Contour mining finds
application in hilly terrain where the topography governs pit
design. The objective of contour mining is to extract coal by
54
-------
excavating narrow strips which follow the circumference of the
hill. Coalbeds generally lie flat in the ground; thus it is
impractical to completely extract coal lying in a hillside. The
overburden becomes increasingly deeper, resulting in uneconomical
extraction. This fact can be readily seen in Figure A-l (58).
The term maximum stripping ratio is used to determine where min-
ing becomes uneconomical. Stripping ratio is usually defined as
the ratio of the depth of overburden removed to depth of coal
produced (meters of overburden/meter coal). Thus, large amounts
of overburden are commonly removed if the coal seam is thick, as
shown in Figure A-l. The maximum stripping ratio varies from
region to region, but 20:1 is a typical figure. At one Illinois
mine as much as 24 m of overburden is stripped to recover 71 cm
of coal (16).
Area mining, the second general method of strip mining, involves
the development of large flat open pits in a series of long nar-
row strips, usually 30 m wide by 1 km or more in length. The
objective of area mining, which also applies to contour mining,
is to expose, recover, and haul away the coal as economically as
possible. This usually means that the overburden should be moved
only once. The above definition of stripping ratio holds iden-
tically for area mining. A generalized schematic representative
of open pit or area mining at an Illinois mine is shown in Fig-
ure A-2. This schematic depicts a dragline working a multiple
coal seam operation. The view of a Wyoming mine in Figure A-3
shows two seams being worked from an upper and a lower bench.
Regional variations exist in strip mining (58), and the three
divisions of East and Mideast, Central, and Midwest and West can
be used to classify these variations as described below.
East and Mideast
The East is characterized by steep, hilly topography with the
coal outcropping on both sides of the hills. Strip mining is
generally confined to small tracts of land, and because of the
nature of the terrain, contour mining with small equipment is
more common than area mining (58).
The Mideast is also noted for hilly terrain, although the slopes
are not as steep as those encountered in Pennsylvania. Contour
mining is generally the rule, especially in Ohio, and variations
from mine to mine concern the amount of land affected as one
(58) Stefanko, R., R. J. Ramani, and M. R. Ferko. An Analysis
of Strip Mining Methods and Equipment Selection. Office of
Coal Research R&D Report No. 61, Interim Report No. 7, U.S.
Department of the Interior, Washington, B.C., 29 May 1973.
131 pp.
55
-------
HILLSIDE BEFORE MINING
DEPICTING STRIPPING RATIO, meters overburden/meter coal removed
ECONOMICAL
UNECONOMICAL
HILLSIDE AFTER MINING
Figure A-l.
Hillside before and after mining showing
typical stripping ratio variability (58).
56
-------
DRAGLINE
ROAD ON
LEVELED
SPOIL
EXPOSED ILLINOIS
NO. 6 SEAM
PLAN VIEW
1.8 m:NO. 6 SEAM SECTIONAL VIEW
Figure A-2. Dragline positioned on leveled spoil
removing parting for multiple seam
operation in Illinois (58) .
57
-------
HAULAGE ROAD
v v v
v SURFACE
Figure A-3. Plan view of a Wyoming open pit coal mine (58).
tract and the equipment size used. In this area equipment with
capacities up to 164 m3 is used to mine coal from seams at depths
up to 56 m (58).
Central
As the topography of the land becomes more flat in the Central
region of the country, the mining methods become more tradition-
al. The pits are nearly straight for their entire length. Dif-
ferent kinds of equipment such as bucket wheel excavators find
rather widespread use in this area because of the unconsolidated
nature of the upper strata. In other areas of the Central region
where the upper strata are consolidated, large draglines are
utilized to mine coal (58).
Midwest and West
The Midwest region of the United States is the western portion of
the Great Plain, specifically the states of North and South
Dakota. The topography of this area is nearly flat, and although
no surface mining is currently under way in South Dakota, ample
lignite reserves are present for future development (58).
58
-------
The topography of the West is characterized by gently rolling
hills which gradually steepen toward the Rocky Mountains. The
coal seams are generally subbituminous and lignite. Small capa-
city equipment is utilized to mine these coals. The most strik-
ing characteristic of the coal seams in this region is their
thickness, which approaches 31 m in some areas (58).
59
-------
APPENDIX B
RESPIRABLE DUST EMISSION FACTOR DERIVATION
AND SUPPORTIVE DATA
UNIT OPERATIONS
The emission factors for open coal mining were arrived at by
field sampling two mines. Information on overburden dusts re-
sulting from drilling, overburden removal (stripping), and blast-
ing was obtained from mine A, a bituminous coal mine located in
Illinois. Mine B, a subbituminous coal mine located in Wyoming,
was sampled for information on coal dusts resulting from blasting,
transport/unloading, and loading.
The field measurements were made on a portable respirable dust
monitor manufactured by GCA Corporation, Model RDM 101-4. When
employed in the respirable "mode" the instrument measures mass
concentrations of particles having mean diameters (assumed
spherical) less than 7 ym. The instrument is capable of measur-
ing dust concentrations ranging from 20 yg/m3 to 10 x 103 yg/m3.
The accuracy of the instrument is defined in its specifications
as "...within ±25% of the measurements obtained from a companion
simultaneous gravimetric respirable mass sample for 95% of the
samples."
The general procedure for determining the respirable dust emis-
sion factors consisted of sampling the equipment actively engaged
in mining for mass concentrations, computing an emission rate via
one of Turner's (37) Gaussian plume models (point source, line
source, dose), and finally relating the emission rate to perti-
nent weighting parameters. The weighting parameters were used to
convert the mass emission rate to mass emissions (g) per metric
ton of coal mined in the case of the unit operations. The spe-
cific weighting parameters used are discussed in this section.
The three-diminsional coordinate system describing the location
of the GCA sampler with respect to the emission source is de-
picted in Figure B-l for point sources. The GCA sampler was
elevated downwind approximately 2 m above ground in all instances
to minimize ground effect. Care was taken to ensure that the
plume was not missed when sampling at x distances less than 100 m
by choosing elevated sites. A rule of thumb generally used to
set the minimum sampling distance was that the sampler be set a
distance x that is greater than 18 times z, the effective height
60
-------
of the emission source (from the sampler datum). The mass con-
centration contribution of the source was estimated as the dif-
ference between the downwind reading and the background reading.
Background readings were obtained by sampling with the GCA
monitor at the mine boundaries furthest upwind.
WIND
GCA SAMPLER
SITE(x,y,z)
- n
Figure B-l.
Three-dimensional rectangular coordinate
systems (point sources).
The raw concentration data from mines A and B are presented in
Table B-l. The results indicate that draglines and overburden
blasting operations do not emit significant quantities of res-
pirable dust, although much visible dust was witnessed. Over-
burden stripping is performed by several types of equipment
throughout the industry, but the functions of each type are simi-
lar and thus the emission factor for overburden stripping was
assigned a zero value. The overburden blasting did not emit res-
pirable particulates; the coal blasting operation at mine B did.
This suggests a greater friability of coal versus overburden.
Drilling operations generated the highest concentrations of dust.
Of all unit operations, drilling comminutes the particles of
greatest amount, especially in tough overburden (rock). Coal
drilling operations were not sampled because they are not as
widely used throughout the industry as overburden drilling.
The unit operations of reclamation and coal augering were also
not sampled. The reclamation operation is similar in nature to
overburden stripping and perhaps less severe. Thus, an emission
factor of zero was assigned to it. Coal augering generates res-
pirable dust that is expected to be similar in magnitude to that
61
-------
TABLE B-l. RAW DATA - UNIT OPERATIONS
Wind
Atmospheric speed,
Unit operation Date stability m/s
Overburden stripping 4/16/75 C 3.0
Drilling 4/17/75 D 9.0
Distance,
X
117.9
101.2
70.7
87.5
87.5
152.4
33.5
33.5
33.5
33.5
Blasting 4/18/75 D 9.8 260.0
76.2
Blasting 5/15/75 B 4.47
457.2
76.2
Loading 5/15/75 B 5.4
76.2
76.2
76.2
Transport 5/15/75 B 2.2 22.9
Transport 5/15/75 B 3.6 1 **•*
76.2
Unloading 5/15/75 B 4.47
76.2
y
0
0
0
0
0
0
0
0
0
0
0
0
30.5
9.1
0
0
0
0
0
4.6
0
0
m
z
15.2
15.2
15.2
15.2
15.2
0
0
0
0
0
0
-12.2
30.5
-12.2
0
0
0
0
0
0
0
0
Dust type
Overburden.
a
Overburden
Overburden
Overburden
Overburden
Overburden
a
Overburden
Overburden
Overburden
Overburden
Overburden
Coalc
Coal
CoalC
Coal
Coal
Coal
Coal
Coal
Coal
Coal
Coal
Downwind
cone . ,
b
<50b
<50b
3
0
0
0
0
0
0
901.2
2,001.2
1,091.2
2,101.2
0.0
480.0
140.0
70.0
273.0
378.0
194.0
460.0
1,280.0
320.0
430.0
60.0
Comments
Bucyrus-Erie 1450-W
60-yd3 dragline.
Bucyrus-Erie 61-R
15-in-dian>. drill
(no control) .
9,107 kg ANFO detonated
(twelve-55-ft holes)
(4-min sample).
196 kg ANFO (4-min sample)
536 kg ANFO (4-min sample)
Approx. 27 metric tons
coal loaded into truck
by 750-metric ton per
hour front-end loader.
91 metric tons loaded
into truck in 5 min.
!91 metric tons loaded
into truck in 6 min.
12.9 km/hr transport
(0.524 rad angle,
unwatered road) .
Onpaved road, 1 truck
36.6 m of transport,
1 truck.
One 91-metric ton truck
unloading on unwatered
road.
One 91-metric ton truck
unloading on watered
road .
Mine A.
Below detectable limits.
CMine B.
Background is for one truck on a watered road, no unloading.
-------
measured for drilling. The emission factor for coal augering is
obtained from the emission factor from drilling, with an appro-
priate correction factor applied.
Point Source
To arrive at the emission factors the emission rates must first
be obtained from the raw data. Turner's Gaussian diffusion point
source model (37) given below in general form was utilized in the
case of the unit operations of loading, drilling, and unloading:
1 /x_\2 1 /z_V
Q = 4x110- a ue2^ e °z' (B-l)
where Q = emission rate, g/s
X = concentration contribution of a unit
operation, g/m3
a = lateral dispersion coefficient
^ a = Ax0'90^1 where A is a stability constant
a = vertical dispersion coefficeint
a = AXB + C where A, B, and C are stability
constants
u = wind speed, m/s
Line Source
The unit operation of transport was estimated by assuming that
the emissions from the vehicles resemble a continuously emitting
infinite line source with the angle between the wind direction
and line source being . The model is Gaussian and is expressed
as (37):
q = -|sinc|>/2? c^uxe (B-2)
where q = source strength per unit distance, g/s-m
Total Dosage from a Finite Release
The blasting unit operation mass emission was estimated as a
total release integrated over the time of passage of the blast.
This release of mass is expressed as follows (37):
QT = DTira azue2V'eV (B-3)
63
-------
where Q_ = total release, g
D = total dosage, g-s/ra3
D_ = xt where t is the total sampling time, s
J. S S
The calculated values of Q, q, and QT are presented in Table B-2.
TABLE B-2. MASS EMISSIONS3
Unit
operation Date
Drilling 4/17/75
Blasting 5/15/75
Loading 5/15/75
Transport 5/15/75
Unloading 5/15/75
X x 106 D^ x 106
Q Q
Model g/m g-s/m
Point 901.2
2,001.2
1,091.2
2,101.2
Dose 480.0 115,200
140.0 33,600
Point 70.0
273.0
378.0
194.0
Line 460.0
1,280.0
320.0
Dose 430.0 103,200
60.0 14,400
Qi 9/3
0.16
0.35
0.19
0.36
0.483
0.537
0.744
0.382
q, g/s-ra QT' g
531.0
1,841.0
0.00307
0.01108
0.00905
169.2
23.6
Blanks indicate data not applicable.
Since the equipment sampled was typical of the industry, the mass
emissions per equipment type were converted to emission factors
for use in describing the industry contribution. The following
describes the conversion of the mass emissions per unit operation
to workable emission factors using appropriate weighting factors.
Drilling Overburden
Q = 0.35 g/s
At mine A, it takes 45 min to drill 16.8 m or 6.2 x 10~3 m/s.
Thus,
0.35 g
1 s
_ = 56.4 g dust
6.2 x 10~3 m meter of hole
64
-------
To estimate the g/metric ton of coal mined, we must estimate the
amount of ANFO per metric ton of coal mined and the ANFO packing
per hole. From annual Illinois state statistics on surface coal
production and ANFO usage, we obtain (1, 17):
52.7 x 10 6 kg ANFO = 1,716.6 g ANFO
30.7 x 10 6 metric tons coal metric ton coal
Mine A uses 46,039.1 g ANFO/m; thus,
56.4 g dust x _ 1 m _ 1,716.6 g ANFO _ 2.10 g dust
m 46,039.1g ANFO metric ton coal metric ton coal
Similarly, for the other three data points, the emission factors
are:
For #2: 1.14 g dust/metric ton coal
For #3: 0.962 g dust/metric ton coal
For #4: 2.16 g dust/metric ton coal
The average drilling emission factor is 1.59 g/metric ton of coal
with a standard deviation of 0.628.
Transport of Coal (Unwatered Road)
1. 0.00307 g/m-s - one 91-metric ton truck at 3.58 m/s , 4-min
sample
or 0.738 g/v-m
2. 0.01108 g/m-s - one 91-metric ton truck at 2.23 m/s and one
pickup truck at 4.47 m/s, 4-min sample
or 1.33 g/v-m
3. 0.00905 g/m-s - one 91-metric ton truck at 3.58 m/s, 4-min
sample
or 2.17 g/v-m
avg. : 1.41 ±0.720 g/v-m
Since the representative mine has an area of 1.97 km2, the dis-
tance for transport is a maximum of 700 m. Thus,
1.41 g/v-m (700 m)(91 Jgriftons ) = 10'85 ?/metric ton
65
-------
In a representative mine the road is watered to reduce this dust.
The sampling results show that over a 50% reduction is achieved
through watering (200 yg/m3 on watered road vs. 430 yg/m3 on un-
watered road; same distance, wind speed, etc.). Thus, the emis-
sion factor for a watered road would be
10.85 g/metric ton (0.465) = 5.04 g/metric ton
Blasting Coal
Floor (1.81 kg ANFO/metric ton): 4.06 g/metric ton
Wall (1.23 kg ANFO/metric ton): 4.24 g/metric ton
avg.: 4.15 ±0.127 g/metric ton
Loading Coal (Including 30-m Transport and Payloader)
115.9 g - 29.9 metric tons (1/3 truck) =3.87 g/metric tons
225.6 g T 91 metric tons (5 min) = 2.487 g/metric tons
312.4 i 91 metric tons (6 min) = 3.444 g/metric ton
160-3 T 91 metric tons (6 min) = 1.767 g/metric ton
avg.: 2.89 ± 0.947 g/metric ton
Loading Coal (Corrected to Exclude Transport)
2.89 - (1.41 g/v-m x 3.0 m/91 metric ton) = 1.96 g/metric ton
±1.42
Unloading Coal (Including 40-m Transport)
(unwatered road)
169.2 g T 91 metric tons = 1.865 g/metric ton
Unloading Only
1. 1.865 - 1.24 = 0.625 g/metric ton
2. 23.6 g 4 91 metric tons = 0.260 g/metric ton
avg.: 0.442 + 0.257 g/metric ton
The emission factors are summarized in Table B-3. Coal augering
is similar to drilling. The weighting parameter used to derive
the representative factor was the ratio of annual auger produc-
tion to annual strip coal production for 1972. This is not a
statistically derived value and as such no error estimate can be
made for it. All factors are expressed in grams of respirable
dust emitted per metric ton of raw coal produced.
66
-------
TABLE B-3. EMISSION FACTORS
(grams of respirable dust/metric ton of raw coal)
Operation
Drilling ,
Transport
(dry load)
Blasting
Loading coal
(inc. trans.)
(exc. trans.)
Unloading coal
(inc. trans. ) ,
(exc. trans.)
Coal augering
2.
0.
4.
3.
1.
0.
#1
10 r
738C
06
87
A
865d
623
1
1
4
2
0
Sample
#2 #3
.14 0.962
.33C 2.17C
.24
.49 3.44
.260
#4
2.16 1
(1
5
4
1.77 (2
1
0.
Average
± standard
deviation
.59
.41
.04
.15
.89
.96
442
+
+
±
+
±
±
±
0.
0-
0.
2.
0.
0.
1.
0.
084
628r
72)c
57
127
H
947)d
42
257
Blanks indicate data not applicable.
Added together to arrive at a factor for transport/unloading.
°Units are grams of respirable dust/vehicle-meter, used to
derive factor in grams/metric ton of coal.
Only used to derive the exc. trans, factor.
WIND EROSION - WORST CASE
The Woodruff-Siddoway (W-S) equation was solved by nomograph to
arrive at the emission factors for wind eroded land (19). The
factors were calculated for each coal state. The W-S equation
describes the amount of total dust emitted. This includes res-
pirable dust and dust via saltation, which is large particle
dust (greater than 7 ym). As a result, the emission factor es-
timates for wind erosion are higher than those for respirable
dust alone. The emission factors are thus a worst case esti-
mate. The assumptions used when calculating the wind erosion
emission factors are listed below:
• Assume no ridges (K = 1)
• Assume no vegetation (V = 0)
• Deviation of percent soil cloddiness based on:
1. descriptions of soil types found in
various states; i.e., loam, sandy loam,
clay, etc.
2. typical particle-size distributions of
various types of soil.
3. based on these two situations, the average
for a particular state was derived. For
example, a very general estimate was made
67
-------
that North Dakota is 1/6 sandy loam, 1/2
silt loam, 1/6 sand, and 1/6 clay.
Percent soil fractions larger than 0.84 mm
in North Dakota = 1/6 (particles >0.84 mm
in sandy loam) + 1/2 (particles >0.84 mm in
silt loam) + 1/6 (particles >0.84 mm in sand)
+ 1/6 (particles >0.84 mm in clay).
The above information was then used to solve the W-S equation.
68
-------
APPENDIX C
INPUT DATA, DERIVATIONS, AND SAMPLE CALCULATIONS
PERTAINING TO MASS EMISSION RATES AND
REPRESENTATIVE SOURCE DEFINITION
MASS EMISSIONS
The work sheet for Equation 4 is presented in Table C-l. The
parameters and units of each are given below:
A. = state areas of land disturbed annually, km2
e. = state emission factor for wind erosion, g/s-km2
P. = state coal production for 1972, metric tons/yr
ZE. = sum of the appropriate emission factors per
1 state;
EE. = 13.3 for all six unit operations, g/metric ton
EE. = 13.2 for states not having coal augering
1 operations, g/metric ton
Q. = total respirable dust mass emissions per state
-1 from open coal mining, g/s
Q. = respirable coal dust mass emissions per state, g/s
Q. = respirable overburden dust mass emissions per
•* state, g/s
Percent ratios are obtained by dividing Q.^, Qjj2/ and Q.3 by
total particulates per state (dimensionless).
The composition of dust emitted from the industry was estimated
to contain 93% coal and 7% overburden dusts. This was estimated
by considering the dust composition from the unit operations and
wind erosion. Overburden stripping and reclamation are not in-
cluded as their respirable dust hazard is negligible (see Appen-
dix B). The breakdown is shown in Table C-2.
69
-------
TABLE C-l. INPUT DATA AND COMPUTATIONS FOR DETERMINING STATEWIDE MASS EMISSIONS3
6
Qjk = AjejXk + 3-171 X 10"8 Pjxk
j State
1 Alabama
2 Arizona
3 Illinois
4 Indiana
5 Kentucky
6 Missouri
7 Montana
8 New Mexico
9 North Dakota
10 Ohio
11 Pennsylvania
12 Tennessee
13 Texas
14 Virginia
A.
11.675
0.991
27.988
16.017
49.716
7.644
2.723
2.210
3.683
35.208
43.455
7.624
1.942
10.680
15 West Virginia 40.877
16 Wyoming
Total
Other states
National
3Blanks indicate
Total respirable
Respirable coal
2.760
data not
dust K =
dust K =
e. x 103
7.47
56.2
11.7
6.05
7.47
11.7
185.4
56.2
51.2
7.47
7.47
11.7
89.0
7.47
7.47
56.2
applicable
i, K! = i
2, X2 = 0.
A.e.
3 3
0.087
0.056
0.327
0.097
0.371
0.089
0.505
0.124
0.188
0.263
0.324
0.089
0.172
0.079
0.305
0.155
P. x 10~3
11,988
2,680
30,665
22,229
58,688
4,129
7,442
6,563
6,016
31,477
24,318
4,893
3,670
9,104
20,031
9,514
253,415
10,197
263,612
3.
EE.
13.27
13.18
13.18
13.18
13.27
13.18
13.18
13.18
13.18
13.27
13.27
13.27
13.18
13.27
13.27
13.18
,171 x 10'
XP.EE.
5.04
1.12
12.82
9.29
24.70
1.73
3.11
2.74
2.51
13.25
10.23
2.06
1.53
3.83
8.43
3.98
106.6
4.26
110.86
5.13
1.18
13.15
9.39
25.07
1.82
3.61
2.86
2.70
15.88
10.55
2.15
1.70
3.91
8.73
4.13
109.8
4.26
114.06
a
Respirable overburden dust
.00.
927.
STotal
national
particulate
Total
particulate
C d (all sources), Ratio. Ratio
Sj2 QJ3 g/s (59) total coal
4.78 0.35
1.09 0.09
12.29 0.86
8.84 0.55
23.39 1.68
1.68 0.14
3.19 0.42
2.66 0.20
2.47 0.23
12.58 3.3
9.78 0.77
1.98 0.17
1.54 0.16
3.64 0.27
8.07 0.66
3.84 0.29
101.8 8.00
4.0 0.26
105.8 8.26
, K = 3, Xs = 0.
emissions (all
37,370
2,304
36,241
23,729
17,318
6,418
8,646
3,259
2,504
55,994
57,406
12,990
17,419
15,139
6,776
2,391
566,7206
073.
sources ) , g/s .
0.013 0.012
0.051 0.047
0.036 0.034
0.040 0.037
0.145 0.135
0.028 0.026
0.042 0.037
0.088 0.082
0.108 0.099
0.028 0.022
0.018 0.017
0.017 0.015
0.009 0.008
0.026 0.024
0.129 0.119
0.173 0.161
0.019 0.018
Ratio
over- ,
burden
0.001
0.004
0.002
0.003
0.010
0.002
0.005
0.006
0.009
0.006
0.001
0.002
0.001
0.002
0.010
0.012
0.001
(59) 1972 National Emissions Report. EPA-450/2-74-012, U.S. Environmental Protection Agency, Research Triangle Park, North Carolina,
June 1974. 422 pp.
-------
TABLE C-2. DISTRIBUTION OF COAL AND OVERBURDEN EMISSIONS
Unit
operation/
source
Drilling
Coal loading
Transport/
unloading
Blasting
Auger ing
Wind erosion
Total
National
emissions,
g/s
13
16
45
34
0
3
114
.28
.37
.79
.67
.7
.2
.1
Estimate
of dust,
% coal
50
100
100
100
100
50
Coal
emissions,
g/s %
6.
16.
45.
34.
0.
1.
105.
64
37
79
67
7
61
8
Estimate
of dust,
i overburden
50
0
0
0
0
50
Overburden
emissions,
g/s
6.
0
0
0
0
1.
8.
64
61
2
Thus the weight percent of coal in the dust is 105.8/114.1 x 100
= 93%. This is a crude approximation, but it is indicative of
the fact that coal dust is the major pollutant.
REPRESENTATIVE - MINE SIZE AND DISTANCE
Representative Size
Mine A disturbs 6.197 x 105 m2/yr of land, per personal communi-
cation with mining personnel. This mine produces 835,531 metric
tons per year at a 13.6 (m/m) stripping ratio. The land distur-
bance of any mine should be proportional to stripping ratio and
tonnage; thus, for one year:
AD = 5.45 x 10"
P x S
R
(C-l)
where An = annual land disturbance, km2
D
P = annual tonnage, metric tons
S = stripping ratio, m/m
R
The average life expectancy of any strip mine is approximately
20 years (35). The average mining property size, A^, is 20 times
Equation C-l; thus,
V
Ap = 1.09 x 10~6 P x S
R
(C-2)
The representative mine size is computed knowing P and SR. The
weighted average SR for the United States is 16.82 as calculated
from Reference 34 and the state coal production for 1972.
71
-------
The average mine size is 108 x 103 metric tons per year computed
by dividing the total 1972 U.S. surface production by the number
of strip mines (2,225). Thus, using Equation C-2, A = 2.0 km2.
Representative Distance
The mine area is assumed circular such that the radius is the
representative distance. Thus,
r = V_E. = 0.792 km = 792 m
¥ ir
72
-------
GLOSSARY
amorphous: Without stratification or other division; uncrystal-
lized.
ANFO: Ammonium nitrate and fuel oil mixture used as an explo-
sive.
anthracite: Hard compact natural coal containing only a small
amount of volatile matter.
auger: Similar to a bit used for boring holes in wood the auger
consists of a cutting head with screwlike extensions; the
head breaks the coal and the extensions raise and dump it
onto conveyors.
auger mining: Method of removing surface coal by boring holes
into the coal bed using an auger.
azimuth: Horizontal direction expressed as the angular distance
between the direction of a fixed point (as the observer's
heading) and the direction of the object.
bituminous: Soft coal containing considerable volatile matter.
confidence interval: Range over which the true mean of a popu-
lation is expected to lie at a specific level of confidence.
emission burden: Ratio of the total annual emissions of a pollu-
tant from a specific source to the total annual state or
national emissions of that pollutant.
fibrosis: Growth of fibrous connective tissue in an organ in
excess of that naturally present.
free silica: Crystalline silica defined as silicon dioxide
(SiO2) arranged in a fixed pattern (as opposed to an
amorphous arrangement).
growth factor: Ratio of 1978 emissions of respirable dust to
1972 emissions of respirable dust.
hazard factor: Primary ambient air quality standard (for cri-
teria pollutants) or a reduced threshold limit value (for
noncriteria pollutants).
73
-------
lignite: Variety of coal intermediate between peat and bitumi-
nous containing much volatile matter; also called brown coal
or wood coal.
noncriteria pollutant: Pollutant for which ambient air quality
standards have not been established.
overburden: Loose soil, gravel, sand, or similar material over-
lying a deposit of useful geological materials (such as a
coal seam).
pneumoconiosis: Disease of the lungs caused by habitual inhala-
tions of irritant mineral or metallic particles.
precipitation-evaporation index: Reference used to compare the
precipitation and temperature levels of various P-E regions
of the U.S.
respirable particulates: Particulates with a geometric mean
diameter less than or equal to 7 ym.
severity: Hazard potential of a representative source defined
as the ratio of time-averaged maximum concentration to the
hazard factor.
silicosis: Diffuse fibrosis of the lungs caused by the chronic
inhalation of silica dust less than or equal to 10 ym in
diameter.
stripping ratio: Ratio of the depth of overburden removed to
depth of coal produced.
strip mining: Coal mining method by which overburden is removed
coal is extracted in a series of regular slices, and the
overburden is replaced.
subbituminous: Coal that is lower rank than bituminous but
higher than lignite.
threshold limit value: Concentration of an airborne contaminant
to which workers may be exposed repeatedly, day after day,
without adverse affect.
tipple: Apparatus by which loaded cars are emptied by tipping
sometimes including an elevated runway or framework upon
which the cars are run for tipping.
74
-------
TECHNICAL REPORT DATA
(Please read/nstmctions OH the revtne btfort completing}
REPORT NO.
EPA-600/2-78-004x
3. RECIPIENT'S ACCESSION NO.
4. TITLE AND SUBTITLE
SOURCE ASSESSMENT;
OPEN MINING OF COAL
State of the Art
6. REPORT DATE
September 1978 issuing date
6. PERFORMING ORGANIZATION CODE
AUTMOR(S) ~~~ " '
S. J. Rusek, S. R. Archer, R. A. Wachter, and
T. R. Blackwood ,
8. PERFORMING ORGANIZATION REPORT NO.
MRC-DA-709
PERFORMING ORGANIZATION NAME AND ADDRESS
Monsanto Research Corporation
1515 Nicholas Road
Dayton, Ohio 45407
10. PROGRAM ELEMENT NO.
1BB610
II.CONTRACf/'GrtANTNO.
68-02-1874
12. SPONSORING AGENCY NAME AND ADDRESS
Industrial Environmental Research Lab. - Cinn, OH
Office of Research and Development
U.S. Environmental Protection Agency
Cincinnati, Ohio 45268
13. TYPE OF REPORT AND PERIOD COVERED
Task Final, 9/74 - 9/77
14. SPONSORING AGENCY CODE
EPA/600/12
IS. SUPPLEMENTARY NOTES
IERL-CI project leader for this report is John F. Martin, 513-684-4417
ie. ABSTRACT
report describes a study of atmospheric emissions from the
open mining of coal. The potential environmental effect of this emission
source was evaluated using source severity, defined as the ratio of the
maximum ground-level concentration of a pollutant at a representative plant
boundary to a hazard factor. The hazard factor is the ambient air quality
standard for criteria pollutants and an adjusted threshold limit value for
other pollutants. Respirable dusts are generated from five unit operations
and from wind erosion; contributions from these sources to the total dust
loading are: coal transport and unloading, 40%; blasting, 30%; coal load-
ing, 14%; drilling, 12%; coal augering, 1%; and wind erosion, 3%. Emissior
factors for the unit operations indicate that 13 g of respirable dust are
emitted per metric ton of coal mined. Total dust severity is 0.036, and
overburden dust severity is 0.014.
Control technology in open coal mining has been implemented for drill rigs,
haul roads, and coal refuse piles. The industry is experiencing a high
growth rate (3.5% per year), and the growth factor for the industry (1978
emissions/1972 emissions) is 1.23.
17.
KEY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
Air Pollution
Coal Mining
Dust
Silicon Dioxide
b.IDENTIFIERS/OPEN ENDED TERMS
Air Pollution Control
Stationary Sources
Source Severity
Open Mining
Particulate
COSATI Field/Group
48A
18. DISTRIBUTION STATEMENT
RELEASE TO PUBLIC
19. SECURITY CLASS (This Ptport)
Unclassified
21. NO. OF PAGES
87
20 SECURITY CLASS (Thtjpagel
Unclassified
22. PRICE
EPA Form 2220-t |t-73)
75
U. S. GOVERNMENT PRINTING OFFICE: 1978 — 657-060/1494
------- |