EVALUATION OF FUGITIVE DUST EMISSIONS
FROM MINING
TASK 1 REPORT
IDENTIFICATION OF FUGITIVE DUST SOURCES
ASSOCIATED WITH MINING
REDCo ENVIRONMENTAL
-------
EVALUATION OF FUGITIVE DUST EMISSIONS
FROM MINING
TASK 1 REPORT
IDENTIFICATION OF FUGITIVE DUST SOURCES
, ASSOCIATED WITH MINING
, prepared~y ,-
PEDCo-Environmerrta .. ,', ,,- . .-.~\ \1!S , Inc.'
. I \ "
SUl t . r - --Square
. io 45246
Contract No. 68-02~132l
Task No. 36 '
EPA Project Officer:
S. J. Hubbard
Prepared for
Industrial Environmental Research Laboratory
Resource Extraction and, Handling Division
U.S. ENVIRONMENTAL PROTECTION AGENCY
5555 Ridge Avenue
Cincinnati, Ohio 45268
April 1976
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" CONTENTS
1.
INTRODUCTION
2.
MAJOR MINING INDUSTRIES
Coal Mining
Copper Mining
Stone Quarrying
Phosphate Rock Mining
3.
" pOage
1
.4
5
8
11
MINING OPERATIONS WITH POTENTIAL FOR
. FUGITIVE DUST
13
17
Overburden Removal
Blasting
Shovels/Truck Loading
Haul Roads
Truck Dumping
Crushing
Transfer and Conveying
Cleaning
Storage
Waste Disposal
Land Reclamation
4.
SUMMARY
5.
REFERENCES
19
27
31
36
42
44
48
52
55
60
64 "
"72
76
ii
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No.
2.1
2.2
2.3
2.4
3.1
3.2
3.3
3.4
3.5
3.6
3.7
3.8
3.9
FIGURES
~ocations of Largest 'U.S. Coal Mines
Locations of Largest U.S. Copper Mines
Production'of Crushed Rock by State, percent
Locations of Largest u.s. Phosphate Rock Mines
Overburden Removal
Blasting
Truck Loading
Haul Roads
Truck Dumping
Crushing
Transfer and Conveying
Storage
Waste Disposal
3.10 Reclamation
3.11 Climatic Factors for Use in the Wind Erosion
'Equation
iii
Page
7
10
12
14
24
30
33
;39
43
47
50
56
61
67
70
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No.
2.1
2.2
2.3
3.1
3.2
4.1
TABLES
Largest U.S. Coal Mines
Largest U;S. Copper Mines; 1973
Largest U.S. Phosphate Rock Mines, 1975
Dust-Producing Operations by Mining Industry
Emission. Factors for Crushed Rock Storage
Piles
Summary of Emission Estimates for Mining
Operations
iv
. P.a.ge
6
9
15
18
58
73
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1.
INTRODUCTION
This evaluation of fugitive dust air pollution from
mining operations was undertaken to identify and compile
currently available information on emission sour6es, regu-
latory approaches, control techniques, and. research programs
related to mining activities. An analysis of the assembled
information will then be used as the basis for recommending
near-term research and development programs which might be
implemented by IERLjCincinnati to fill gaps in the data base
. .
and further document effective control techniques for fugi-
tive dust from mining operations. For the more promising
recommended R & D efforts, proposed technical approaches
will also be developed.
The project is composed. of three tasks, each of which
will have its own task report:
Task 1 -
Identification of fugitive dust sources
associated with mining activities.
Assessment of current status of the
environmental .aspects of fugitive dust.
Recommendation of promising research
Task 2 -
Task 3 -
areas.
The project is similar in scope to a.study recently com-
. 1
pleted by Monsanto Research Corporation. However, the
iptent of. the present contract is to provide recommendations
for specific research programs while the Monsanto Research
study was designed to compile p~eliminary data on fugitive'
dust emissions from open sources and to recommend other
1
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souices for testing. Therefore, only the first of the three
tasks overlaps to any extent with this previous work; their
work has been utilized in preparing the Task I report.
The present Task I report summarizes current knowledge
concerning fugitive dust sources at mines and ranks the
identified sources in order of relative importance from the
, ,
standpoints of air quality impact and need for further
, .
research. Data for the report were obtained from a litera-
ture search and from PEDCo's files on fugitive dust sources.
The literature search was not intended to be exhaustive, but
to be thorough enough to uncover all studies in which fugi-
tive dust emissions from mining operations were quantified
by a reasonably accurate procedure. In this task, primary
importance was attached to the identification of all mining
activities that are major dust sources and the estimation of
representative emission rates from these various sources.
The scope of the project includes both surface and
underground mining plus related operations normally per-
, ,
formed at the mine sites, such as crushing and storage. It
does not include dust that is generated and remains under-
ground or in an enclosed area--only emissions that ,affect
ambient air quality. Also, it does not include emissions
which occur off-site during shipping or at distant process-
ing plants. Almost all particulate emissions at mines would
be categorized as fugitive dust since they are generally
emitted at ground level as a result of equipment activity or
material transfer. rather than from stacks.
This report is divided into three chapters following
the Introduction. Chapter 2 describes four major mining
industries (coal, copper ore, rock quarrying, and phosphate:
rock) and the sizes and geographic distribution of their
mines. Chapter 3 describes 11 different mining operations
which are responsible for significant fugitive dust emis-
sions in one or more of the major mining industries, and
2
-------
presents estimates of emissions from each of these 'opera-
tions. The final chapter summarizes those Qperations which'
have the greatest air quality impacts and tho~e'for which
additional emission data are most needed.
3
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2.
MAJOR MINING INDUSTRIES
The four mining industries which are probably the
largest sources of. fugitive dust nationally are coal,
copper, crushed stone, and phosphate rock mining. These
. industries are each described briefly in. this chapter to
provide a basis for evaluating the extent and impacts of
fugitive dust air pollution from mining operations.
All four of these materials are mined primarily in
surface mines, which have far more potential for fugitive
dust emissions than underground mines. In addition, the
tonnages removed from these mines are generally greater than
for other minerals and ores. Some other materials which
were also considered because of their large tonnages and
surface operations are iron, oil shale, and sand and gravel.
Iron ore mining was eliminated because ferrous metals are
not within the purview of the Resource Extraction and Han-
dling Division of the Cincinnati Industrial Environmental
Research Laboratory, EPA, the sponsoring group for this
work. oil shale was not included because there are pres-
ently no large-scale oil shale surface mines in operation.
Sand and gravel mining was not included because much of this
material is mined and processed wet and is therefore non-
dusting.
Mines other than the four types used as examples here
can certainly be major.fugiti.ve dust sources. They have the
same unit operations and points of dust release, so their
emissions can be estimated by ~omparison wi~h any one o! the
four-mini;~ i~du~tries for-~hich data have b~~ a~sembled. .
------ -
--.-
4.
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2.1
COAL MINING
)
There were 603.4 million tons of bituminous coal and
lignifemined in the u.s. in 1974 in a total of 5,2~7 mines~
Of these mines, 3,208 were surface mines ,and 2,039 were
underground. Production from surface mines surpassed under-
ground mines in 1974 for the first time, accounting for 54
2
percent of the total.
The 50 largest coal mines and their 1973 and 1974
production rates are listed in Table 2.1. These mines, 34
surface mines and 16 underground, produced 24.6 percent of
the coal mined in 1974. Their locations are shown in Figure
2.1. They are concentrated in the coal mining areas of
Appalachia, the Central states, the Northern Great Plains,
and the Four Corners area. All of the Western mines shown,
plus those in Indiana, Ohio, and most of those in Kentucky
are surface mines.
Although total coal production has been relatively
stable for several years, there has been a definite shift
from the East and from underground mines to the strip mines
of low sulfur coal in the West. This trend is expected to
accelerate in the future with the opening of giant new'mines
in Powder River Basin, northwestern Colorado, the Four
Corners area, and the lignite fields of North Dakota and
eastern Montana. Many of these mines will be used to supply
coal gasification plants and mine-mouth power plants.
The most unique aspect of surface coal mining is the
huge amount of earth moving associated with it. The over-
burden removal operations to get to the coal seams dwarf
previous major earth moving projects such as canals and
. da,ms. A new generation of larger earth moving equipment was
developed to handle this task.
Trucks are used at almost all surface mines to trans-
port the coal from the mine to the processing area or load-'
ing'ramp. For shipment to consumers, railroa~s are the most
5
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Table 2.1
LARGEST u. S.
Company
Mine
Utah International
Decker
Peabody
Peabody
Southwestern
Illinois
Peabody
C&K
Peabody
Washington
Irrigation Dist.
Clinchfield Div.,
Pittston
Peabody
Central Ohio.
Arnax.
Consolidation,
Central Division
Peabody
Western Energy
Arch Minerals
Arnax
Peabody
U.S.Steel
Peabody
Pacific Power &
Light
Arnax
Arch Minerals
Peabody
Peabody
Monterey
Inland Steel
Kemmerer
Arnax
Consolidation,
Mountaineer Div.
Old Ben
Peabody
Peabody
Island Creek
Consolidation,
Christopher Div.
ConsolidatiOn,
Mountaineer Div.
Rosebud
Old Ben
Freeman
Consolidation,
Ohio Valley Div.
Peabody
Mathies
Peabody
Arnax
Arnax
Mountain Drive
Old Ben
Peabody
Knife River
. s
Navajo 5
Decker No.1
River KingS
River Queens,u
Captains
No. IOu
Foxs
Black Mesas
Centra lias
Moss No. 3u
Sinclair5
MuskingumS
.. s
Belle Ayr . s
Egypt Valley
Lynnvilles
Colstrips
Seminoe No. IS
LeahyS
Universals
Robena
Kens,u
Dave JohnstonS
AyrgemS
Seminoe No. 2s
Camp No. lU
KayentaS
No.1
Inland
Sorensen5
Ayrshires
Robinson Runu
Old Ben No. 15.
Big SkyS .
Homesteads
Pevler No. IS'u
Humphrey No. 7u
LoveridgeU
Rosebuds
No. 24u
Orient No. 3u
Irelandu
vogueS
Mathiesu.
StarU
WrightS
Minnehaha5
Mountain Drives
No. 26u
Baldwinu
Beulahs
s
u
strip mines
underground mines
State
COAL MINES
Est. ~roduction,
10 ton/yr
1974 1973
NM
MT
IL
KY
IL
6955
6786
6474
4703
4347
7389
4159 .
6526
4172
4451
4147
2620
3247
3229
3903
5291
3668
898
4257
4065
4254
2865
2942
3044
2871
3202
2897
3206
1498
2620
2695
2588
2546
250
2401
2396
1972
2449
1733
2692
2185
1510
2377
2207
2343
2412
2036
1999
2097
2012
1663
2100
1291
1726
Source: Bituminous Coal Data, 1974 Edition, National Coal
Association, Washington, D.C., 1975.
6
IL
PA
AZ
WA
4132
4000
3933
3890
VA
3679
3529
3367
3313
3253
KY
OH
t'lY
OH
IN
MT
WY
IL
IN
PA
KY
WY
.3232
3213
3142
2834
2833
2815
2793
2687
KY
WY
KY
AZ
IL
IL
WY
IN
WV
2685
2590
2528
2515
2480
2469
2437
2404
2380
IN
MT
KY
KY
WV
2345
2229
2194
2189
2155
.1985
wv
WY
IL
IL
WV
1963
1960
1919
],860
1814
1809
1808
1790
1790
1765
1739
1727
1722
KY
PA
KY
IN
IN
KY
IL
IL
ND
-------
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1
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300
Figure 2.1.
Locations of largest U.S. coal mines.
-------
common means with 66 percent of the tonnage in 1974. Almost
40 percent of this amount was in unit trains. The remainder
of coal shipment is evenly divided among barges, trucks, and
mine-mouth operations (with 11 percent each). All other
modes of transportation account for less than one percent.2
2.2
COPPER MINING
Domestic mine production of recoverable copper in 1975
was 1.41 million tons, down sharply from the 1.60 million
tons in 1974 and 1.72 million tons in 1973 as a result of
decreased demand for copper products. The principal copper~
producing states were Arizona, with 56.6 percent of the
total, Utah (12.7%), New Mexico (10.4%), Montana (7.2%),
Nevada (5.6%), and Michigan (5.2%).3 The largest 25 copper
mines, which provided 89 percent of the total production in
1973, are listed in Table 2.2. Their locations are shown in
Figure 2.2.
Open pit mines accounted for 83 percent of mine output
and underground mines for 17 percent. The production of
copper from leach pads and in-place leaching (mainly recov-
ered by precipitation with iron) was 160,000 tons in 1973,
or 9 percent of the output from the mines.3
As indicated from the above data, copper mining is
characterized by very large mines of relatively low grade
ore rather. than many small mines in rich veins. The average
Yleld nationally of copper in copper ore was only 0.53 .
percent. This low grade ore necessitates the handling of
large quantitites.of material in the mining and processing
steps. Also, wide variations in copper content within the
ore body may require the mining and handling of additional
amounts of waste material that is too low in copper content
to justify recovery.
8
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Table 2.2
LARGEST. U.S. COPPER MINES,
1973
Kennecott Copper
Utah Copper
Magma Copper
San Manuel
Phelps Dodge
Morenci
Anaconda
Berkeley Pit
Phelps Dodge
Tyrone
Kennecott Copper
Ray Pit
Cyprus Mines
Pima
White Pine Copper
White Pine
Duval Sierrita
Sierrita
Kennecott Copper
Chino
Anamax Mining
Twin Buttes
Phelps Dodge
New Cornelia
Inspiration Copper
Inspiration
Asarco
Mission
Kennecott Copper
Ruth
Anaconda
Yerington
Asarco
Silver Bell
Anaconda
Butte Hill
Cities Service
Copper Cities
Duval
Mineral Park
Magma Copper
Magma
Phelps Dodge
Copper Queen
UV Industries
Continental
Bagdad Copper
Bagdad
Duvat
Esperanza
a This figure includes underground as well as open pit
production.
Company/Mine
\
!
NA = not available
Estimated
production,
tons
255,000
158,300a
119,500
127,800a
104,000
98,900
88,100
76,600
NA
67,800
73,600
53,800
43,100
46,600
50,000
35,800
23,800
NA
NA
NA
NA
NA
NA
NA
NA
State
Utah
Arizona
Arizona
Montana
New Mexico
Arizona
Arizona
Michigan
Arizona
New Mexico
Arizona
Arizona
Arizona
Arizona
Nevada
. Nevada
Arizona
Montana
Arizona
Arizona
Arizona
Arizona
New Mexico
Arizona
Arizona
Co~nty
Salt Lake
Pinal
Cochise
Silver Bow
Grant
Pinal
Pima
Ontonagon
Pima
Grant
Pima
Pima
Gila
Pima
White Pine
Lyon
Pima
Silver Bow
Gila
Mohave
Pinal
Cochise
Grant
Yavapai
Pima
Source: Preprint from the 1973 Bureau of Mines Minerals
Yearbook, Copper, U.S. Department of the Interior, Bureau
of Mines, Washington, D.C., 1973, pp 2-5.
Source: Fugitive Dust from Mining Operations, Monsanto
Research Corporation, Dayton, Ohio, prepared for U.S.
Environmental Pro~ection Agency, 1975.
9
-------
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Figure 2.2.
Locations of largest U.S. copper m~nes-
;!OO
300
-------
Approximately 94 percent of the ore is concentrated
before it is smelted. The concentration {by froth flota-
tion} usually occurs at the mine site because of the reduc-
tion that can be obtained in the amount of material to be
shipped to the smelter. The smelters are located inprox-
imity to the major ore deposits~ most of the concentrated
ore is shipped via unit trains on private tracks owned by
the copper companies. The smaller mining companies that do
not have their own smelters send their ore to custom smel-
ters, which may involve longer shipping distances.
2.3
STONE QUARRYING
Production of stone in 1974 totaled 1.044 billion tons
of which 1.042 billion were crushed.4 Crushed stone was
produced in every state except Delaware, with the six states
of Florida, Illinois, Missouri, Ohio, Pennsylvania, and
Texas accounting for more than one third of the national
total. The percentage of total crushed rock quarried in
. .
each state with significant production is shown in Figure
2.3.
There were 5,431 active quarries in the country in
1974. Of these, 228 mined at least 900,000 tons during the
year and accounted for 37 percent of the domestic produc-
tion.4 Stone quarrying tends to bean industry of smaller
operations serving local and regional needs.
Almost all stone quarries are open pit mines. Blasting
is normally used in quarrying crushed rock. Other equipment
such as rippers and hydraulic excavators may be used to
break the rock loose. Surge piles between the quarrying and
the crushing/sizing operations are also quite common.
Most of the crushed rock is used for construction-
related purposes such as roadbases, concrete aggregate,. or
cement manufacture. In many cases, pits or quarries may be
11
-------
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, \, .; !,' ~ \., i l '''r 1.1 i 4.2
. 3.4 '. i-.- ,!' " ,1.8 ,I 5.0 (...... k'....{:;6KY 3.9 )..../ ....\RG\i-I~~. . .
\ 'ARIZO-'-'- ., ',. . KEN ~. -.-.-
....J NA '''''''-'-.-.' '~.J J.,-'T":'CA'ROLINI>. \
'. , I NEw ME)(fCO-'-'T.L._._._.-.-.-.-.1..' . .r'-'-'-'-' J N. .)
. Y . ' , .-.-., OKLAHOMA .-.-.-'-'\ 'Til~NESSEE .~' ~
0,," ,'! , TEMS , iARKANSAS.., 4.3 ,'" .-'-'-'~
;; I i!' 2.2. . '. ,-,-'r'..!'",. S.CI>.RGlINI>. .
i .,' ; I. ! !-.- ~ALI>.BAMt\GEORGIA \.,
.. ~ ,'"'. I I I . .
'.. i , -.-.-.-.", ( il.8 \ 4.0 ".
J'\. '. ,'; ~._._.-j " \
,''''''''',,, 'lOUISIANA. , .
.'-..J.. '-,r'-.-.~.J 5.5 I I I \
, . \ . .
, , !MISSISSIPPI,
'\ i -'-"!.
, '
, ..---.
'...1 \
\\,..(
~
tV
~
/.I."~..
.,~.
,
SC31t':'I'M,!('s
IC>';'
200
JOO
-~--
..:..
Figure 2.3.
Production of crushed rock by state, percent.
-------
operated in conjunction with specific construction projects'
'and mined only intermittently. The crushing plants are
often portab~e and may be used to service as many as 10
different quarries.
Because it is desirable to have quarries located close
to the points of usage for the stone, quarries are more
likely to be located iri or near.populated areas than are
other types of mines. This proximity has also caused more
concerns about the environmental impacts of quarries than
the more remote mines--noise, dust, truck traffic, blasting,
. .
and inadequate site reclamation after mining have all
created local problems at some quarries.
2.4
PHOSPHATE ROCK MINING
Marketable phosphate rock production in 1975 was 48.8
million tdns, an increase from the 45.7 million tons of 1974
and 42.1 million tons of 1973. Mining. of phosphate rock is
concentrated in Florida, which accounted for 77.7 percent of
the total output in 1975, and particularly in Polk County in
west central Florida. Locations of the largest 24 mines are
shown in Figure 2.4, and their estimated production rates
are presented in Table 2.3~ These 24 mines accounted for 77
percent of phosphate rock mined in 1975.5
Mining procedures are somewhat different for the differ-
ent types of phosphate rock deposits found in Florida,
Tennessee, and the Western states. The Florid~ land pebble
deposits are contained in a matrix of sandy clay averaging
16 ft in thickness, overlain bya 20 ft overburden of sandy
'I 6
SOl. Prior to mining, the land is drained and vegetation
is removed. Draglines with 35 to 55 cubic yd buckets strip
the' overbu~den and mine the matrix simultaneously. The
overbur~en is dumped into an adjacent mined-out area or
stacked on natural ground adjacent to the cut. The matrix
13
-------
1-'
~
ow"""........ '.
, ASHIN "- 0 0
GrON ,..,.... 0 -~.
. 'M --.. ..""" .
I ' ONrANA -"-"- 0 . . . "E\
o , I ..-....,... 1\. {../>.\,~
, \ -..-..-......... ~c> "'. .
, . " ,NORTH DAKOTA ' "-'. ~.' . 0 : -
'-. I '. ! ~MINNESOTA ......,,~,,~ 0 I
OReGo -.-.-.-. . } , \ .h ' .
N "'\, " .-\ ' 0
.., ~ . ,,... '
.I IDAH~' 0 ~._. 0 \." <.~CHIGAN ~c::::::J '," (\
~ \.... :-.-.-.-. .SOUT;;-OAKOTA'-'-))) WISCONSIN .~n0 rd" ! \~.
. I .) WYOMING -.-.-/ I' r~o ~ ~ /' ' t.,.J
'- ' , ,. ,\. "..----'" \-;,.~S
CAL/~O'-' I I " I" . ~ L.-'~'
RNIA ...,..-. ...I., , , " '7 ''iORK ,,;0"'''' . ~,
'NtVAO' '- , . r.'-'-'-'-'~ o. / NE'I'i .-'r:' ' .
! 4 .-.~.-. ; 17.'-'-,-,-, ,IOWA, ~N'S-:\.."I-N\ '?-'. ~
I . UTAM-'" . NEBRASKA -.-.~\ ~._._. . ,pEN IN' V
I' , ." . ILLINOIS ." \ .
" 'L. . , ' .J D'I~',:rOH'O, :>
I -...,.. 1. \.. ,IN. 1\
( i 0 . i C'QlORAi:>O'-' .-., l) ~ l !\.. '~:-M:).i?, .
\. ii, ~,_._._._._._.. 'ws'souRi',,! 0 l 0 \ 0 ,/w,,'J'/~:1' n~~.,.
'. i ' ' KANSAS ~ \. I r'- r ,..' ~.
\ . I I\,\., ). .~, ,
,I ' , ,'I. ~ I
'L I ! I I.,. - ..1'-' " .../ .-,N'I'- .
., r.A'-'- . 0 , 0 . .... 0 ~ENTUCKY .F' ~~_.-
. RIZO '-'-.' I. .., ~ .-' .
...J NA ..,..-.-.-. . I .j ~'-'T':'Cl'-ROLlNA)
'. , I NEW MEX/CO-'-'T'.L.-.-.-.-.-.-.-. . "! -1"'-'-'-'-' J N. .
. 0 \.: ", .-.-., OKLAHOMA 1-.-.-.-.: !TEI~NESSEE."" ?j
0." 1. , ,TEXAS, ,ARKANSAS I 0''''' -'-'-'~
> i ;! . . ,-,,,,,':f".J.,: S.CP;ROLINA .
i ' ; I. !. !-'-':AlABAMA\GEORGIA \,
" . ! '"""- I l. I . ,
~ , , . '-'-'-', ( i \ '\
" ". " ; l._._.~ I' \ . 0
.I ,,",,',,' 'lOUISIANA. , '
'-- J... .-.r'-'-._.J . I I , \
... \ . .
,0 \ {MISSISSIPPI',
'\ i -'-'1'
, '
, ..--.
'../ \
\ (0,
. v
. 0 \,.~~' 0
~
I.
:~
"r(
Scalt')1 M,:rs
100
:!r:f) .
300
.:./
Figure 2.4.
. ,
Locations of largest U.S. phosphate rock mines~
.'
-------
Table 2.3.
LARGEST U.S. PHOSPHATE ROCK MINES,
1975
Company/Mine
Estimated
production,
106 ton/yr
State
County
IMC
Clear Springs
Noralyn
Homeland
Phosphoria
- Achan
Kingsford
11.0
Polk
Agrico
Palmetto
Payne Creek
Saddle Creek
Fort Green
7.0 -
Mobil
Fort Meade
Nichols
3.3
1.2
3.sa
Occidentai
Suwannee
Swift
Silver City
Watson
2.6
W. R. Grace
Bonny Lake
2.5
Brewster
Haynsworth
1.8
Gardinier
Fort Meade
1.8
USS-AgriChemicals
Rockland
Lake Hancock
1.2
Texasgulf
_Lee Creek
o.sa
Borden
Tenoroc
0.4
Beker
Manatee
0.4
Stauffer
Vernal
0.4a
Florida
Florida
Polk
Florida
Polk
Polk
Florida
Hamil ton
Florida
Polk
Florida
Polk
Florida
Polk
Florida
Polk
Florida
Polk
N. Carolina
Beaufort
Florida
Hillsborough
Florida
Manatee
Utah
Uintah
a This figure is 1973 data, Preprint from the 1973 Bureau
of Mines Minerals Yearbook, Phosphate Rock, pp. 3-5.
Source: - Particulate and Sulfur Dioxide-Area Source Emission
Inventory for Duval, Hillsborough, Pinellas, and Polk Counties,
Florida, PEDCo-Environmental Specialists, Inc., Cincinnati,
Ohio, prepared for U.S. Environmental Protection Agency, June
1975.
15
-------
is deposited in a previously prepared sluice pit where
hydraulic guns slurry it. The slurry is pumped for dis-
tances up to six miles to a washing plant.
Phosphate rock ore in Tennessee is stripped and mined
from consolidated deposits with 2 or 3 cubic yd draglines,
then trucked to the processing plant.
In Western states, all phosphate ore is strip mined
except for two underground mines in Montana. Mines in
southeastern Idaho use scrapers, bulldozers, or power
shovels to remove overburden and mine the ore. Phosphate
rock in Utah is quarried after an overlying limestone layer
is drilled, blasted, and removed. Ore mined in Western
states is either hauled by truck or moved by rail to pro-
cessing plants. .
In the period 1971 to 1975, demand for phosphata rock
worldwide exceeded production capacity, reversing a condi- .
tion of oversupply that characterized the industry for the
previous five years. Indications of reduced demand and
resistance to higher prices were noted in 1975. Mining
capacity now appears capable of satisfying anticipated
demands. Florida output ~s projected to steadily increase
to a level of about 55 million tons per year by 1980 and
remain near that level for 10 to 20 years.6 .
16
-------
3 .
MINING OPERATIONS WITH POTENTIAL FOR FUGITIVE DUST
There is no established classification of mining opera~
tions. The Council on Environmental Quality Report to
congress7 on coal ,surface mining and reclamation identified
nine discrete operations associated with surface mining:
. ,
construction of access roads, scalping or clearing of vege-
tation, drilling and blasting to fracture the overburden,
removal and placement of overburden, removal of the coal,
rehandling and grading of the overburden, revegetation,
water drainage control, and sediment basin construction. In
an air quality study of mining,8Environmental Research and
. ,
Technology described the operations somewhat differently:
topsoil removal and placement, overburden removal and redis-
tribution, coal removal and transport, conveying, sorting,
crushing, storage, vehicular traffic on unpaved roadsJ and
. coal fires.
The breakdown of operations used in this report is
oriented toward isolation of specific dust-producing activi-
ties. For each of the 11 operations identified (see Table
3.1), the operation is described and all available emission
estimates compiled and compared. Also, variables on which
the emission rate is dependent are'discussed, e.g., climate
and size of material being handled.
All of the 11 operations are not found in every type of
mine, and in some cases the operation is only a significant
dust source at one type of mine. The operations that are
usually dust sources wi thin a particul'ar mining industry are
shown in Table 3.1.
17
-------
Table 3.1. DUST-PRODUCING OPERATIONS .BY
MINING INDUSTRY
Mining industry
Operation Coal Copper Rock P20S rock.
Overburden removal x + + x
Blasting + x x 0
Shovels/Truck loading x x x 0
Haul roads x x x 0
Truck dumping + x x 0
Crushing + + x 0
Transfer & conveying + + + x
Cleaning 0 0 0 0
Storage + + x x
Waste disposal + x 0 +
Reclamation x 0 + x
x = usually a major source
+ = a minor or occasional source
o = usually not a dust source
18
-------
In estimating the total fugitive dust emissions from a.
mine, it is preferable to identify the dust-producing activ-
ities present and estimate emissions for each one .separately
rather than to use a single emission factor for the entire
mine. The former procedure permits direct determination of
the major source areas--the ones needing control--and results
in accurate assessments even if the mine has some atypical
processes.
3.1
OVERBURDEN REMOVAL
Description
Overburden removal is an operation in almost all
surface mining and entails removal of all topsoil, subsoil,
and other strata overlying the deposit to be mined. Signif~
icant advances in methods of surface mining have occurred in
recent years with the development of giant excavating and
hauling equipment designed specifica~ly for these operations.
In 1965, coal surface mining was not considered feas-
ible unless the overburden depth to seam thickness was 10:1
or less--i.e., a coal seam five feet thick to justify
removal of 50 ft of overburden. With introduction of the
larger equipment, this range of overburden to seam thickness
has increased to as much as 30:1. Removal of up to 200 ft
of overburden is now feasible for coal mining, wh.ile the
average in 1965 was 48 ft.9
There are three major types of coal strip mining--area,
contour, and auger. Area strip mining is used where the
terrain is relatively flat. Large-scale excavation equip-
ment, usually draglines, remove the overburden material and.
deposit it in spoil banks in a trench left by the previous
strip. Thus, only the initial strip produces waste over-
burden that must be disposed of or stored for land
19
-------
reclamation.
Trenches excavated by draglines are normally
about 100 to 200 ft wide.
On land to be mined with slopes greater than about 15
degrees, contour strip mining is usually employed. In this
mining method, the overburden is removed from the slope to
create a flat excavation, or bench, resulting in a, vertical
'highwall on one side and a downslope pile of spoils on the
other side. The exposed deposit is then mined and the land
reclaimed by backfilling the previously worked area with
newly removed overburden. If a pattern of backfilling to
the original or similar contour is carried out concurrently
with the mining and the backfilled land is'revegetated, the'
mined area can usually be successfully reclaimed. Leaving
the spoils on the downslope can result in landslides and
prevent reclamation.
The third type of strip mining--auger mining--is
usually done in conjunction with contour mining. The
deposit exposed in the highwall by the contour method is
mined by using large drills or augers to pull the deposit
horizontally from the seam.
A national bill to regulate surface mining of coal has
been passed by the Congress on two different occasions.
However, because of steep slope performance standards con-
tained in both bills, the President has vetoed them. The
two states where the majority of contour and auger coal
mining methods are used, Pennsylvania and West Virginia,
have laws prohibiting spoils on downslopes. In West Vir-
ginia, all but the last 20 feet ~f the highwall must be
covered and in Pennsylvania all of the highwall must be
re-covered.
Increasingly, as demand for complete land reclamation
grows, the overburden material is segregated by removing
topsoil and other subsoil components 'suitable for revege-
tation, storing them separately, and then covering the
20
-------
contoured spoil banks with these two layers during the
reclamation process. This greatly increases the ability to
revegetate and reclaim the land. It also increases the time
and cost of overburden removal, with the need for bulldozers
and scrapers for removing up to five feet each of topsoil
and other subsoil strata and transporting this soil to
storage areas.
For other types of surface mining such as open pit
mining and quarrying, overburden removal may be only a one-
time or occasional operation. rather than continuous. For
. .
these types of mines, the deposit to be removed is of the
same magnitude or larger than the overburden volume and the
location of the mining activity is relatively fixed. There~
fore, the overburden is removed permanently and may be
transported off-site for disposal.
In excavating overburden, three kinds of equipment are
used in typical surface mining operations:
o
Draglines
Shovels
Small mobile tractors, including
bulldozers, scrapers, and front-
end loaders
o
o
Most surface mining operations use these equipment items in
varying combinations.
Draglines are electrically powered equipment capable of
moving large amounts of material with a bucket capacity
ranging from 30 to 220 cu yd (overburden has an average
density of 1.3 ton/cu yd). The .dragline moves along the
surface or bench, positions its bucket on the overburden to
be removed, and loads it by dragging it toward the machine.
The loaded bucket is then lifted, the machine rotated, and
the bucket dumped in an area that has already been mineq.
21
-------
Alternately, the excavated material may be temporaril¥
stockpiled and moved to a final disposal site by loading
onto trucks.
Shovels are large diesel or electrically powered
stripping equipment used in surface mines for a number of .
years and specifically designed for a particular mine.oper-
ation. These machines proceed along a bench scooping up
fragmented overburden in buckets with capacities of up to
130 cu yd. In the l~rgest surface mines, shovels are often
used in conjunction with draglines.
. .
Tractors are typically used either in small mines or in
conjunction with larger,. more specialized equipment in large
mines. The principal advantages of tractors are their
maneuverability, ability to negotiate steep grades, and
capability to dig and transport their own loads. They are
used for a variety of tasks, including clearing, topsoil
removal, preparing benches, and leveling spoil piles.
A fourth type of excavation equipment, the bucket wheel
excavator, is seldom used in this country. It has a rotat-
ing bucket wheel mounted at the end of a boom up to 400 ft
long. As the wheel rotates, the buckets along the perimeter
. .
are loaded when they cut into the deposit with an upward
motion. Continuing rotation causes the buckets to be
inverted and empty onto a conveyor which then transports the
material to a disposal area~ Only very large mines with
suitably soft overburden material can justify the expense of
this equipment.
Emission Estimate
The two primary fugitive dust sources associated with
overburden removal are:
22
-------
o
Dumping of dragline buckets or shovels
full of overburden material into adja-
cent tr~nches or spoil banks, as shown
o
in Figure 3.1.
Operation of scrapers and bulldozers in
topsoil and subsoil removal and transfer.
. .
. If .the overburden material must be transferred .to trucks for
removal, . the emissions from loading, travel on haul .roads,
and dumping are considered under these other mining operations.
No sampling specifically for either of these two
-...F
sources has been done.
However, some emission estimates
have been made.
Hittman estimated 0~002 Ib/ton of coal
mined as the average emission factor nationally for exca-
vation at coal surface mines where area stripping was used,
and b.003 lb/ton of coal with contour stripping.9 For
uncontrblled mining in the Southwest (primarily the Four
Corners area), their estimate was 0.26 lb/ton of coal; with
. .
controls (assumed to be watering), fugitive dust emissions
were estimated to be 0.009 lb/ton of coal. Battelle esti-
mated the total fugitive dust emissions from surface mining
of coal in Western states to be 0.1 lb/ton of overburden
removed and indicated that overburden removal was the larg-
est emission source at these mines.10 Considering the
common ratios of overburden removed to coal mined (5:1 to
20:1), Battelle's factor appears to .be an order of magnitude
higher than Hittman's value. From both of these references,
it can be concluded that emissions from strip mining and
particularly the overburden .removal process vary consider~
ably geographically, presumably because of the much drier
climate in the Western states.
PEDCo estimated that the dragline operation at a lig-
nite surface mine in North Dakota had an emission rate of
0.05lb/ton of overburden removed, primarily resulting from
23
-------
,;;- r
'tt~
~
!!I.
, "
Figure
Overburden removal.
3.1.
Source:
Phosphate,
Florida Phosphate Councily
24
p
6.
-------
dumping of the excavated material from a height of at least
100 feet into the trench. For the ,particular mine surveyed,
this was equivalent to 0.42 lb/ton of lignite mined. In
addition, three scrapers stripping the topsoil and subsoil
layers were estimated to each produce ,fugitive dust emis-
sions of 16 lb/hr of operation, or a total of 0.03 lb/ton of '
lignite mined on an annual basis. These' estimates were made
by comparison with emission rates from similar fugitive qust
sources, such as construction and aggregate handling, which
had been tested. The resulting emission estimates of 0.45
lb/ton of lignite or 0.054 lb/ton o'f overburden removed
compare well with Battelle's average factor if it is assumed
that about half of the total strip mining emissions result
from the overburden removal operation (the val~e was 63
percent for the particular mine that PEDCo surveyed).
Engineering Research and Technology (ERT) has provided
input8 to the Bureau of Land Management on the air quality
aspects of coal development in northwest Colorado for an
environmental impact statement.ll 'They proposed an emission
factor of 0.0024 percent of the material moved (0.048
lb/ton) for topsoil removal, overburden removal, or coal
removal, including a cor~ection for climatic conditions and'
control measures (watering) at the mines. This emission
rate was obtained by applying a p~blished emission factor12
for aggregate handling and storage to the overburden han-
dling operation, but reducing that emission rate bya factor
of three because the material at the mines is coarse broken
,rock containing few fines rather than aggregate. This
emission rate was further,reduced to account for lack of
fugitive dust on wet or frozen days. The resulting factor
agrees quite well with the PEDCo value for mining in a
similar 9limatic area, especially considering the rather
crude methods of approximation used in both cases.
25
-------
Overburden removal for copper mining, rock quarrying,
and phosphate rock.mining may be much .less of a fugitive
dust source than in coal mining for several.reasons:
o.
Much less overburden material is handled
in open pit mines and quarries.
If the overburden material is to be
o
o
removed permanently,
separate handling of
is required.
Phosphate rock deposits in Florida and
other Southeastern states are generally
mined in areas where the water table is
near the. surface and the overburden has
a high moisture. content and therefore
does not produce dust when moved. Aver-
age overburden depths in Florida are
no segregation and
topsoil fractions
o
about 20 ft.
If the overburden depth is fairly shallow,
the excavated material will not be dropped
as far from the dragline bucket or shovel
to the trench or spoil bank, creating less
of an impact and less opportunity for dis-
persion of airborne material.
PEDCo estimated particulate emissions from dragline
operations at an open pit copper mine in Butte, Montana to
be 29 ton/yr.13 No data were obtained on the amount of
. overburden removed annuallYi the .emission rate per ton of
ore mined was 0.0008 Ib, almost negligible in comparison
with the factor for coal mining. The excavation area was
noted to be moist and nondustingi emissions were estimated
by assuming the active dragline operation of 2 acres to be
equivalent to an active construction site, using an emission
factor of 1.2 .ton/acre/month.
26
-------
- -
Th~- Baitelle,PEDCo,_an~ ERTdata show th~t overburden
removal is potentially one of the 1argest fugitive dust
sources at surface mines. It is also one of the most
variable. The dust losses from this operation vary with the
composition and texture of the overburden material, its
moisture content, excavation-procedures, equipment employed,
etc. For any specific mine, the emission rate is probably
most closely related to the amount of overburden m0ved.
3.2
BLASTING
Description
Drilling and blasting are done to fracture hard,
consolidated m~terial so it can be removed more easily and
efficiently by the excavating equipment. Blasting may be
needed for certain impenetrable overburden or for partings
between the seams being mined, but more commonly to loosen
- the deposit itself. This operation is a routine part of
open pit mining and quarrying; its use in surface coal
mining is dependent on the depth and hardness of both the
overburden and the coal bed; it is almost never required
with phosphate rock mining. -
The blastholes are drilled from the surface of the rock
layer or deposit to the depth to which the deposit is to be
broken. Shelves of 30 to 50 ft depth are often used if a -
deposit- of greater-thickness is being mined. A flat bench
is first prepared for the drilling rig, which is mounted on~ -
a tractor or truQk. The holes are drilled in a predeter-
mined pattern by an electrically-powered rotary drill 4 to
15 inches in diameter. Larger holes (containing more explo-
sive~) are drilled for fracturing rock than ~or breaking
coal. Typical blasting patterns range from 20 ft by 20 ft -
to-SO ft by 100 ft, with the blasthole spacings varying with
27
-------
the material to be fractured. When a particularly resistant
rock formation is encountered, a pneumatic drill may be
required.
Normally, the explosive is a mixture of ammonium
nitrate and fuel oil. Either dynamite or metalized mixtures
such as ammonium nitrate and aluminum can be used when a
more powerful explosive is required. From 300 to 11,000 lb
. .
'ofexplosives are charged into each hole, depending on its
depth, location in the pattern, and the material encountered
in drilling. Millisecond d~lays .in the blasting sequence
are programmed to maximize the breaking effect and to mini-
mize seismic shock. Mats may be used with small blasts to
reduce the scattering of rock fragments during the blast.
The frequency of blasting is rarely more than once per
day and may be much less often. For reasons of safety and
to minimize disruption of other mining activities, blasting
is usually conducted between work shifts. The area to be .
blasted must also be cleared of equipment and workers during
the time that the holes are being charged and wired for
detonation, so drilling and blasting are generally as iso-
lated from the other active mining operations as possible.
Emission Estimate
Sampling of drilling and blasting operations at one
g~anite guarry indipated emission rates of 0.0008 lb/ton of
granite quarried for drilling and 0~16 lb/ton due to blast-
ing.14 Of 11 different processes sampled at the quarry (not
the same 11 mining operations described herein},-plasti~g
erbduced the most emissions, accounting for 63 percent of
the total fuqitive dust emissions from the quarry and crush-
--
~ng plant. More explosive charge is required for blasting
granite than other ore. Based on the results of. this study,
the research firm that conducted the sampling, Monsanto
. -
Re~~arch, ha~ scheduled further field testing of emissions
from blasting. 28 .
~
~""-s.~/)
-------
PEDCo estimated emissions from, daily ,blasting at a
large open pit copper mine to be about 200 lb of suspended
material per blast, or about 0.061 lb/ton of ore. This
estimate was based on visual observation and was noted to be
only an order of magnitude value. The large difference
'between the two available emission factors could be due to
. ,
unreliability of the PEDCo estimate or to actual differences
between the amounts of dust generated by the two blasting
, .
operations. The additional scheduled testing may resolve
this question.
Blasting is a difficult operation to sample because of
its short duration and the danger of placing sampling equip-
ment or men close enough to the area of the expected plume
prior to the blast. Also, the force of the blast throws
much material into the air that is larger in particle size
than suspended particulate. Distinction of this settleable
material (which may have a much greater mass) from the sus-
pended fraction may not be possible at the time of the
sampling; particle sizing analysis on the collected sample
, '
and correction for the percent by weight of settleable
particulate may be necessary. Observation of film footage
of blasting shows that much of the fine dust that remains
airborne is actually generated as the blasted rock returns
to the surface after being lifted by the force of the blast,
not by the initial explosion. IS The d~illing part of this
operation is amenable to conventional o~en source sampling
methods, but these emissions arepropably negligible com-
pared to em~ssions from blasting.
The dust plume from a blasting 'operation is shown in
Figure 3.2. Blasting is not similar to any other fugitive
dust source, so development of an emission factor cannot be
accomplished by comparison or extrapolation of data from
other operations.
This operation is an obvious dust source wherever it
occurs. While its appearance indicates that it is a major
29
-------
Figure
3.2.
Blasting.
30
-------
source of mining. emissions, its time-averaged contribution
. .
may be quite small because the ~missions occur.for only a
few seconds per day or week.
3.3 SHOVELS/TRUCK LOADING
Description
In most surface mines, the ore or material being mined
is loaded onto off-highway trucks for transport from the
point where it is removed to a central transfer location or
processing area at. the mine site. The material can also be
transported within the mine in a mechanical or hydraulic
conveyor system, but this method is rarely used except in
phosphate rock mining, where the deposit is usually pumped
as a slurry through a pipeline to the processing area.
Another seldom used alternative to shovel and truck opera-
tion is the mobile storage bin into which material can be
loaded directly by dragline, then crushed and.loaded into
trucks.
Any of the excavation ~quipment described in Section
3.1 can. be used .to excavate the deposit and load it onto
trucks. However, electric powered, crawler-mounted shovels
are most often employed for this purpose because they can
load the trucks more quickly. The shovel breaks the frac-
tured deposit loose, scoops the bucket full of material,
. .
lifts the bucket and swings it over the truck bed, and
releases.the load through t~e hinged bottom 6f the bucket.
When the truck is full, it drives off and another moves into
position while the shovel is scooping another bucket of
material~
The newer haul trucks at mines usually have load capac-
ities of 100 to 200 tons and are diesel-electric powered.
The trucks may be either end dumping or the gondola-shaped
31
-------
bottom dumping, depending on the configuration o~ ~he tipple,
or dumping area. The same trucks may also carry low grade.
ore or unmarketable material in the deposit to a separate
, '
dump area for disposal. The loading operation and fugitive
dust potential for ~cooping and loading this waste material
is identical to that for the material being mined.
, . ,
A small front-end loader may be assigned to the area
being worked by the shovel to remove spilled material that
could cause damage to truck tires and to move materials that
cannot be easily reached by the less maneuverable shovel.
For irregular deposits and smaller mines, ,a front-end loader
,may be used instead of an electric powered snovel.
The area where the shovel is working is normally.
freshly exposed, so the material has almost the same mois-
ture content as the unexposed deposit. However, the posi-
tion where the trucks are loaded may dry rapidly as a result
of the traffic movement. It is difficult for watering
trucks or other control equipment to gain access to truck
loading areas because of the danger of driving near the
mining equipment or haul trucks (which have poor close range
visibility) and because the shovel, the deposit, and the
power line for the shovel often block access from all but
one direction.
Emission Estimate
, Dust is generated at many point~ in the truck loading
operation, but mainly by the scooping of loose material by
the shovel, dumping from the shovel bucket into the truck
bed, and movemerit of trucks. into position to be loaded.
Dust generation from truck loading is shown in Figure 3.3.
, '
Several emission estimates have been made for the entire
operation. Midwest Research Institute sampled the loading
-
of crushed rock by front-end loaders and determined an~
<.....:-
32
-------
~
t.: .-
-.- .
"':o. . .... .......... .
~-A,). :~~~~~. 'r~.'- . 1Ib.-
!., '=""-~::._"'1-.. '1'-.... _..:.--....~
.,'.01;.
..!'-.
1; ~ ;,w
T I
.. ."
-....--.r
. ~7:" -"''''~
.-i'" .~' .'-'/' .~,
.It'''L.....rtr~ .~,'" f Jo /" ...
.... ,''''.'. -.."
.~. ~,
,-
.J/
. .
-
r-
w
w
~..
Figure 3.3.
Truck loading.
Source:
Draft E1S,
Eastern Powder River Coal Basin,
1974,
p 1-74.
-------
average emission rate of 0.05 Ib/ton of
sipn factor was also applied by PEDCo to
ore by shovels as the differences in the
13
thought to offset one another:
.-
12
rock. This emis-
loading of copper
two operations were
o
the shovel must break the fractured rock
- loose instead of just scooping it out,
resulting in higher emis&ions than £or
loading of aggregate;
the shovel is not as maneuverable as a
front-end loader and therefore drops the
rock a greater distance into the truck;
the crushed rock tested was very dry and
contairied a substantial amount of fines,
in comparison with moderate moisture con-
tent and few fines for the shovel opera-
o
o
o
tion; and
the crushed rock loading was
higher wind speed conditions
copper ore loading.
exposed to
than the
The effect of the shovel's larger bucket size on emission
rate could not be determined.
The PEDCo emission factor estimate for loading lignite
- -
coal in North Dakota is- 0.02 Ib/ton loaded. This lower
estimated emission rate was based on comparison with loading
of crushed rock, considering the higher moisture content and
fewer fines in the lignite. The lower value also appears
reasonable in comparison with emissions from other oper~-
tions at the lignite mine, such as truck dumping and grader
operation.
The ERT air
cited in Section
quality analy~is for Colorado coal mines
3.1 proposed the same emission factor for
loading as for overburden _removal, 0.048
coal removal and
34
-------
lb/ton. This value is almost the same as those developed
for crushed rock and copper ore, and may be a function of
lower moisture content in the coal beds. in northwest. Colo-
rado than in North Dakota lignite.
Monsanto Research's sampling at a crushed granite plant
indicated that loading onto haul trucks produced negligible
emissions,14 reportedly because of the large aggregate size,
i.e., the absence of fine granite dust.
The Hittman report included an emission factor o£ 0.04
. .
percent due to "windage losses" in truck hauling at coal
mines.9 It was indicated that most o.f these emissions
-
occurred at the two ends of the hauling trip--loading and
dumping--and that most of the weight loss was probably as
airborne particulate. . However, much of the airborne partic-
ulate could still be due to settleable material. If it is
assumed that half of the total "windage losses" of.0.8
lb/ton (0.04 percent) occur during loading and that 25
. .
percent of this material remains suspended, the emission
estimate for truck loading would be 0.10 lb/ton. This is
. .
higher than the other estimates, but certainly close enough
to confirm the relative magnitude of these other values.
Independent emission estimates for the truck loading
. .' .
operation cover a fairly wide range, possibly indicative of
the many variables involved in this operation~ The most
important of these variables are the moisture content and
amount of fines in the material being loaded, the number and
types of equipment working in the loading area, and cllmatic
conditions at the mine.
35
-------
3.4
HAUL ROADS
Description
. Haul roads, mostly temporary unpaved roads between the
active mining areas, tipple, waste disposal areaSi and
equipment service areas, are common to all surface mines.
In a typical mine, these. roads constitute about 10 percent
of the total area directly disturbed by the mining.16
Because of .the size of the trucks and crawler-mounted equip-
ment that use these roads, they are normally constructed at
least 40 ft wide. In mines opened in recent years, particu-
larly those in the West that use 100 to 200 ton capacity
trucks, the roads may be as wide as 100 ft.
Some of the haul roads at the mine lead from bench
level at the bottom of the deposit to undisturbed surface
elevations, which may be 200 to 300 ft higher. Therefore,
these haul roads either have a steep grade or follow a
circuitous route to the higher elevation. In areas where
contour mining is practiced and lighter equipment is used,
the roads generally exhibit poor alignment and drainage, low
durability, and marginal maintenance. Where area mining is
practiced with its attendant heavy equipment, roads are
necessarily better engineered.
Road surfaces vary according to the terrain, type of
operation and size of equipment used. Road surfaces may be
graveled but more commonly they are just graded. In areas
of flat open terrain, the roads are graded with berms
thrown up at .the road edges from excess material generated
during grading or maintenance.. In Eastern states, where
mine operations are located in hilly or forested terrain,
the use of berms is often prohibited or discouraged because
of its adverse drainage effect.
36
-------
Haul roads are normally cleared of spilled material and
regraded frequently while in use. Heavy equipment tends to
.rut and compact the surface. Continuous maintenance of haul
roads for the heavy equipment makes higher speeds possible
and provides greater usage time of the roads. Generally,
the haul roads are built and maintained as cheaply as possi-
ble while still not slowing down production from the mine.
At any given time, only a portion of the roads at the mine
site will be active, but the "abandoned roads are left as is
for possible reuse when the active mining area moves again.
In the interim period, they serve a definite purpose in
providing good access throughout the mine.
In addition to the haul trucks, other .vehicles use the
haul roads regularly--water trucks, fuel and service trucks,
pickup trucks, motor graders, bulldozers, and explosives
trucks. The vehicle miles traveled (VMT) per day on haul
roads can be estimated from the numbers of each type of
vehicle in operation at a mine and their respective driving
patterns (e.g., round trip distance from loading area to
tipple and number of loads per shift per truck). Alterna-
tively, the VMT can be estimated from total gasoline and
diesel fuel usage and average fuel consumption rates for the
different vehicles.
Haul roads at mines are routinely watered for dust
suppression during all periods when water on the road sur-
face does not create a safety hazard (generally when temper-
atures are above freezing). The water is usually applied by
. .
large tank trucks equipped with a pump and directional
nozzles which spray the road surface and adjacent shoulders
and berms. Fixed pipeline spray systems have also been used
. .
on main haul roads that are relatively permanent.. Various
chemicals may be added to the water or applied separately to
the road surface to improve binding and reduce dusting.
Over 100 dust suppressant.materials are now marketed, and
37
-------
many of them have been_proven effective for short periods in
tests on mining haul roads.l? As a result 6f the frequent
watering, heavy bearing loads on the road surfaces, and
chemical applications, mining haul roads usually have the
appearance of oiled or crudely paved roads rather than rural
gravel roads.
Emission Estimate
There have been several studies during the past few
years of emission rates from unpaved roads. However, as
indicated above, emissions from mining haul roads may be
much different than those from normal unpaved roads because.
of the larger vehicles, compacted surfaces, and frequent
watering. Figure 3.4 shows alarge~capacity truck on a
well-controlled haul road. Close observation of well-
controlled haul roads reveals that much of the dust is
generated near the edges of th~ roads, where the surface is
composed of looser -material, and in areas where the surface
has dried. Also, haul roads have fugitive dust emissions
that result from movement other than traffic--roa& construc-
tion and repair, loss of fines from the open bed trucks
during transit, and wind erosion on abandoned and seldom
used roads. Vehicle exhaust contains particulate emissions,
but it is not considered to be fugitive dust and is therefore
not included in the emission estimates.
There have been at least three different emission esti-
mates made specifically for traffic on unpaved haul roads.
The first of these was by PEDCo. It was developed from
EPA's published emission factor for unpaved roads:18 .
38
-------
.'"
-
~~~
.-----
<\..0:
....'-
r
,
'h
filii!
1
j
..", .A;<
$
.. 'li'J
. .: I'
. -
~
411.. ...
- "..
~::'r.'"
.'.-". -. t...~~~~
~'.- ~ .;,,; '~'- ',;" . "";J":', -"!'...~~..,.. ..- ._'~
.' " .....~~: -' " ... " 11
<~ -,~~~.: ~'. <-". . ~~:/.:;1
,.:, - .1.-"'. ' ~;..:~---- f;.~~~" .
"<~::.:. ..::..:.~~
... "" ~
...
..
,.
'. -
.'
, -,
'...
- -
....
-........,.
~
- ----
-,.
-
'.
.-,. \..".
. ..;.:.,
-
....
IfjI .
~
:--{'$:;,,~
~'''' "--
"'
Figure
3.4.
Haul
roads.
39
-------
EF = (0.60) (0.81) (s) (5/30) (1-'W/365)
( eq . 1 )
where EF = emission factor, lb/VMT
. .
0.6 = average fraction of emitted particulate
in the suspended particulate size range
(less than 30 ~ diameter)
s = silt .content, percent
5 = average vehicle speed, mph
W = days with 0.01 inch or more of. precipi-
tation or reported snow cover
This emission factor was modified to account for the much
larger surface area of the road in contact with the truck.
tires. It was assumed that the relative emission rates for
off-highway trucks, even though they have only four tires,
would be two and one-half times as great as for light duty
vehicles, based on the comparative widths of tire faces.
Other input data used to calculate the emission factors for
two different mining operations are summarized below:
Parameter
For open pit
copper mine
For lignite
surface mine
Average vehicle
. Days/yr with no
cover
Emission reduction due to
watering and chemicals,
percent
speed, mph
rain or snow
15
274
20
166
80
50
Emission factors,
lb/annual VMT
Haul trucks.
Pickup trucks
1.1
0.4
2.2
0.9
in addition, an uncontrolled emission factor of 32
lb/hr was proposed for g~ader operat~ons in these PEDCo
studies, and the same control efficiencies were assumed for
40
-------
the graders working on the haul roads as for the truck
traffic. Windage losses in transit were thought to be
negligible in comparison with emissions from the road sur-
faces in these two instances, but for some materials the
emissions from the moving trucks could be significant.
erosion emissions from the haul roads were assumed to be
i~di&tinguishable from wind erosion of other exposed areas
at the mines and were therefore considered in another source
Wind
category.
Monsanto Research's study ofa granite quarry showed
emission rates from hvehicular movement on unpaved roads" of
0.048 Ib/ton of material processed, or about 2.4 Ib for each
round trip to the crusher, assuming 50 ton capacity trucks
and only haul truck traffic on the roads. A conscientious
haul-road watering program was reportedly being implemented
at the mine during the test program. Since the dimensions
of the quarry and hauling frequency were not described, it
is not possible to compare this value directly with the
other available emission factors. However, it appears to be
somewhat lower.
ERT used a base emission factor of 3.7 Ib/VMT (obtained
. . )17 f
from an early study of fugitive dust emlSSlon sources or
both haul trucks and light duty vehicles at surface mines in
northwestern Colorado. This factor was then reduced by
multiplying by a climatic correction of 0.44, the fraction
of days when the surface was not wet or frozen, and a con-
trol factor of 0.50 to account for watering of the roads on
dry days. The resulting net emission factor was 0.8 Ib/VMT
for total annual travel at the mine. This value is near the
weighted average of emission rates for the copper. mine and
employed the same rationale as the PEDCo study in applying
correction factors to account for differences between emis-
sion rates from normal unpaved roads and mining haul roads.
41
-------
The available emission factors for this mining opera-
tion are in fairly close agreement. Using any of these
values, haul roads are shown to be a major fugitive.dust
~ . -
source at all surface mines, even with the relatively ~igh
-- '.
control efficiencies obtained with frequent watering and use
of chemical dust suppressants. The calculation procedures
used to derive the factors indicate that variables which
affect emissions from this operation most are vehicle speed,
estimated control efficiencies, and climatic conditions at
the mine.
3.5
TRUCK DUMPING
Description
Truck dumping is the simplest operation at the mine to
describe--it involves only the dumping. of the mined material
from the truck into a tipple or receiving hopper for the
primary crusher. The same operation may also occur at the
edge of a spoils slope if the truck is dumping waste mater-
ial or overburden. While the operation is quite simple, it
has been identified as a significant fugitive dust source at
.d'ff t' 13,19.. h 'F'
many 1 eren mlnes, . as sown ln 19ure .3.5.
Emission Estimate
Dust is generated as
truck bed and strikes the
Three different estimates
the material tumbles from the
ground or side of the hopper.
of the emission rate from this
operation were located. Midwest Research Institute, in a
sampling study of aggregate handling operations, estimated
that dumping of crushed rock or gravel onto storage piles
accounted for about 12 percent of the total emissions of
0.33 Ib/ton from handling, or 0.04 Ib/ton. The truck dump-
ing operation was not sampled in. isolation from the other
42
-------
a
,
.~
,c:..
w
~
, .
'1:11,
"",
Q
.-
.. ...........--...,.
~-I:II
II! w.
!II
!
."i
. ~
-...-.--.. . ~.. .--
-- -- ._~~~ ----:o..~_. - ~. ,.,..-. ."1)-- -~---' ~""- -;.,~J
t"-.~, ~~.::':;~"~:~': -7":7~~' ::: -...:.: ' - '~.:-;....-: cf ,- . - ~._~
c A """ !!"~" -..,.... ....-- ..-..." .-....
.' -'- .. 4] .
. -,...
-~ ..~;
.-: . . -
~
-~:
'.
4.;;~,;. - ,,;..
J ~~....."
'""
-~
- - ,.
J ~. ..... ~ ...
...... ",..---J6"'" ~
...-- - ---
- --
Figure
3.5.
Truck dumping.
Source:
Draft E1S,
Eastern Powder
River Coal
Basin,
1974,
p
1-75.
-------
handling operations and the estimate of 12 percent was
partially subjective. This emission factor for dumping of
aggregate onto storage piles was recently publish~d in
Supplement 5 of EPA' s Comp"ilati"onof "Air" PoTlu"tan"t" Emission
Factors~18
Monsanto Research determined an" emission rate of
0.00034 ~b/ton for truck unloading at the hopper of a pri-
mary crusher.14 The material being handled was quarried
granite with very little fine material present.
For two separate studies, PEDCo used an emission factor
of 0.02 Ib/ton for truck dumping. This value was derived by
taking half the publishedEPA emissio~ factor for dumping of
aggregate because of the much larger size of the broken ore
and coal being handled and its higher moisture content. The
50 percent reduction was based on the estimated control
efficiency of watering, I? which is probably comparable to
the effects of higher moisture content and larger material
size.
Intuitively, it seems that emissions from truck dumping
should be less than for the truck loading operation because
dumping does not include the activity of the shovel or
front-end loader in loosening and scooping the deposit. In
comparison with the values presented in Section 3.3 for
emissions from truck loading, the MRI and PEDCo factors for
truck dumping appear to be quite reasonable. However, as
with most of the mining operations, there may be a wide
range of emission rates for mines of different minerals or
in different climates;
3.6
CRUSHING
Description
The crushing operation is a fugitive dust source at
both underground "and surface mines. The material is charged
44
-------
to the primary crusher by means of a receiving hopper. At
large mines, there may be more than one hopper or dumping
bin serving separate primary crushers placed in parallel.
Primary crushers are jaw crushers, set to act upon rocks
larger than about six inches and to pass smaller sizes.
Depending on the ultimate size requirements of the product,
the material from the primary crusher maybe screened with
the undersize going directly to the screening plant and the
oversize to secondary crushing, or all material from primary
crushing may be routed .to the secondary crusher. The secon~
darycrushers are of the cone or gyratory type.
As the material is crushed, much more surface area is
created. If the incoming material has a high internal
moisture content (such as lignite coal), the new surfaces
will be moist and nondusting. However, if the material has
a low internal moisture content, the crushing greatly
increases the potential for airborne dust generation. The
new surfaces tend to dry out as the material continues
through the process on conveyor belts and tnrough the secon-
dary crushers and screens. As the rock or coal becomes more
finely ground and drier, the in-process dust releases become
greater.
One method of suppressing the in-process dust is by
adding water to keep the material moist at all stages of
processing. If the use of water can be tolerated, it is
.usually sprayed at the crusher locations and shaker screens.
The addition of water may cause blinding of the finest .size
screens, thereby reducing their capacity.
The crushing/screening op~tatiort is either fully
enclosed or the dust emission points are hooded, with a
local exhaust system, control device, and stack. This is
the only operation at the mines that would not be strictly
defined as a fugitive dust source, . since the emissions are
confined and emitted at a single point (as shown in Figure
45
-------
3.6) . However, .most crushing operations still have some
fugitive dust losses that escape the hooding system at.
points such as the crusher discharges and conveyor transfer
points. . At rock quarries, most of the crusners are port-
able, are not well enclosed, and therefore usually have
particularly high fugitive dust emissions. One emission
estimate for coal preparation assumed that half the dust
generated went through a collection system to controls and
8
half escaped.
Emission Estimate
. For coal crushing, EPA's published compilation of
emission factors does not include a quantitative estimate,
but states that "the crushing, screening, or. sizing of coal
are minor sources of dust.,,20 The writeup on coal crushing
.also indicates that 95 percent control can be achieved by
use of water sprays and 99+ percent control is possible with
sprays followed by mechanical dust collectors. The Hittman
9
report also states that dust emissions from coal prepa-
ration plants are negligible.
Based on some data from coal processing for coke pro-
duction, PEDCo estimated2l that the uncontrolled emission
rates for the three major emission points in the operation
would be:
Primary crushing =
Secondary crushing =
Secondary screening =
0.02
0.06
0.10
lb/ton
lb/ton
lb/ton
In combination .with the estimated control efficiencies cited
above, these values appear to substantiate the non-quantita-
tive evaluations that coal crushing is only a minor dust-
producing source.
46
-------
- ---
--- --
"'1.~. --
<'~..-~-,
\
\
\
,
\
Figure 3.6.
Crushing.
47
-------
In contrast, the current EPAemission factors for rock
h' "t h' h h below'. 20
crus lng are qUl e 19, as sown
Primary crushing = 0.5 Ib/ton total
= 0.1 Ib/ton suspended particulate
Secondary crushing
and screening = 1.5
= 0.6
lb/ton total
lb/ton suspended particulate
It has been noted that even the lower of the two sets of
emission factors often overestimates annual emissions from
rock quarries in regional emission inventories, indicating
that these factors are most applicable to uncontrolled
portable crushers or must be combined with very high control
efficiencies to produce reasonable values. It cannot be
determined from the source descriptions whether the EPA
emission factors include just stack emissions or both stack
emissions and fugitive dust losses.
Crushing operations at a granite quarry have been
sampled by Monsanto Research.14 Their results, which
include both stack emissions and fugitive dust, are more
consistent with expected emission rates than the EPA values:
Primary
Secondary
Secondary
crushing = negligible
crushing = 0.018 lb/ton
screening = 0.026 Ib/ton
\
3.7
TRANSFER AND CONVEYING
Description
Although conveyor systems may be used to transport
material frQm the active mining area to the processing area
48
-------
or to deliver the processed mat~rial to the consumer, don-
veying is most often found within the processing area~-
moving the crushed material to storage, a cleaning process,
or the train loading station. This operation also includes
the loading of train cars and other transfer of the mater-
ial, except for conveyors within the crushing or storage
operations which are considered to be integral to these
operations. Because of the large tonnages that must be
moved in mining, most of the transport systems are belt
conveyors rather than screw, vibrating, or continuous-flow
conveyors.
Generally,
conveyor runs between processes are less
than 1,000 ft. The average length of the few haulage con-
22
veyors between pits and crushers is about 2,100 ft, and
off-site delivery conveyors of up to 12 mi have been built
for coal.
Loss of material from the conveyors is primarily at the
feeding, transfer, and discharge points and occurs due to
spillage or windage. A conveyor belt is shown in Figure
3.7. The total weight loss in transit is certainly greater
than the fugitive dust emissions from this operation since
much of the spillage is deposited along the conveyor and
. ""
some of the windblown material is in the settleable size
range.
Excessive moisture in the material or air currents can
create discharge problems on belt conveyors. Therefore,
most are enclosed, and in some cases the transfer points may
be hooded and vented to a dust collector". Both the enclo-
sure and the hooding greatly reduce fugitive dust emissions
from this operation.
"Emission Estimate
Conveying is one of the most variable mining operations
with respect to fugitive dust emission rates. In many
49
-------
-
Figure 3.7.
Transfer and conveying.
50
-------
mines, there are no belt conveyors or similar transfer
processes; the material is moved by truck to the tipple and.
loaded directly onto trains. At other mines, extensive
networks of unenclosed conveyors are used, such as with
bucket wheel excavators. Also., the ~missions from conveying
different materials vary. greatly, depending in part on size
distribution and moisture content.
ERT proposed a single emission factor for the combined
processing sources at coal mines in northwestern Colorado--
0.44 lb/ton (0.044 percent of material processed with half
of these emissions fugitive dust). The processing sources
at these mines were identified as transfer and conveying~
crushing, and storage. Since other emission estimates are
available specifically for the crushing and storage opera-
tions at coal mines, a value for conveying can be determined
by subtraction from the overall ERT emission factor. Using
the higher of alternative emission estimates for crushing
and storage of 0.18 lb/ton and 0.054lb/ton, respectively,
the indicated emission rate for conveying would .be 0.20
lb/ton. This seems to be excessive in comparison with
estimates for conveying other material, and may be an indi-
cation that other unidentified particulate sources are also
included in the ERT emission factor for the processing area.
The value of 0.20 lb/ton does not account for the relatively
. .
. .
hig~ control efficiencies, usually at least 90 percent,
associated with enclosed transfer and conveying systems.
The Hittman report stated that coal conveyor systems
"are either covered or operated at such a speed that dusting
does not occur to any great extent." Also, it was poin~ed
out that only a small proportion of coal transport is done
by this method. However, the same report used a value of
0~04 percent, or 0~8 lb/ton, loss through spillage at con-
veyor transfer points. Even if only a few percent of the
51
-------
spillage losses are in the form of dust, emissions from coal
. .
conveying would be comparable to those from coal storage
piles.
Monsanto Research sampled conveying operatioDs at a
. .
gr~nite quarry and determined that fugitive dust emissions
-.. r4---
from conveying crushed granite are also negligible. The
~poit did not mention whether the conveyor was enclosed.
Monsanto Research also sampled storage and handling
operations for phosphate rock and derived an emission factor
of 0.35 Ib/ton for the combined operations. 23 With a stated
emission factor of 0.20 Ib/ton for storage, the indicated
emission rate for handling (conveying and loading onto
railroad cars after drying) .is 0.15 Ib/ton. It is assumed
that all the handling following drying is in enclosed,
controlled systems.
PEDCo developed an emission factor for transfer and
loading of dry phosphate rock which agrees well with Monsanto
Research's factor. The PEDCo emission estimate of 1.5
Ib/ton uncontrolled, with average
to 95 percent, was developed from
company estimates provided by six
in Flordia.
control efficiencies of 90
source test'data~nd
phosphate industry plants
3.8
CLEANING
Description
Cleaning or beneficiation of the ore improves the
quali ty of. the mined material by separating undesired c.ompo-
nents at the mine site. This operatiori greatly reduces the
amount of material which must be shipped to the processing
plant and also decreases solids handling and disposal proh- .
lems in all subsequent refining steps (or the combustion
process in the case of coal).
52
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By far the most cOmInon method of beneficiation is froth
flotation, where a slurry of the crushed ore is subjected to
aeration in the presence of reagents which selectively
separate the mineral being mined from other material in the
deposit~ In order for the flotation process to work prop-
erly, the ore must be crushed or ground small enough to
liberate the mineral being extracted. Metallic ores are
generally ground finer than 48 mesh and coal ana most non~
metallic ores should be 2G mesh or finer.
In flotation machines, the ore is suspended in water at
a loading of 15 to 35 percent solids by means of air or
mechanical ~gitation. Surfaces of the mineral particles are
treated with chemicals called promoters or collectors which
make the particles aerotropic and hydrophobic. With con-
tinued' aeration or agitation and the addition of a frother,
a layer of foam forms at the water surface. The treated
mineral particles become attached to air bubbles, rise to
the surface, and are skimmed ~ff. untreated components
collect in the bottom area and are drained off as.underflow.
The valuable concentrate from froth flotation may be either
the froth product or the underflow product. Metallic sul-
fides of copper, lead, zinc, nickel, mercury, and molybdenum
collect in the froth.
The initial low~grade concentrate may be processed
through a second "cleaner" flotation cell to remove addi-
tional extraneous material. The tailings from the cleaner
cells are recirculated through the system or concentrated
separately in additional cells~ Regrinding of these mid-
dlings is necessary in many ores. The tailings or wast~
material from the flotation machine are discarded in slurry
form for easier transport. The final cdncentrate is de-
watered irt thickeners, and filters prior to shipment.
Well over 90 percent of non-ferrous metallic ores are
1. 24
concentrated by froth flotation prior to sme t1ng. Most
53
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of the phosphate rock fines in Florida are recovered by
flotation. About 70 percent of the coal from underground
mines and 30 percent from surface mines are subjected to
some type of mechanical cleaning--by jigs, concentrating
tabl~s, dense media, or flotation. Of the coal that is
cleaned, about 20 percent is thermally dried.9
Emission Estimate
Much of the cleaning operation is performed in water,
and even after the concentrate or cleaned material is
dewatered it is still wet and non-dusting. Only if an
unusual cleaning process such as magnetic separation, dry
tabling, mechanical classification, or air blowing is used
does this operation have any potential for fugitive dust
generation.
Thermal dryers at coal cleaning plants are significant
particulate air pollution sources, but they would not be
categorized as fugitive dust sources. Emission estimates
for the common types of coal dryers are presented in EPA's
Compilation of Air Pollutant Emission Factors, along with
estimated effici~ncies of various control devices:
Type dryer
Fluidized bed
Flash
Uncontrolled emissions,
Ib/ton
20
16
25
Multilouvered
Cleaning has been included as a mining operation with
potential for fugitive dust emissions mainly for complete-
ness. At most min~s, there are no emissions associated with
this operation. No emission factors were found in the
literature for sources other than the thermal coal dryers.
54
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3.9
STORAGE
Descriptian
This aperatian invalvesanyapen starage pile af the
mined material that is lacatedat the mine site, either
priar to. ar after same initial pracessing. The star age
piles may be shart-term with a high turnaver to. accammadate
irregular daily ar weekly thraughput rates far different
~equentialpracesses, ar may pravide a lang-term reserve far
emergency suppliesar to. meet cyclical seasanal demands.
Frequently, hawever, there is no. stackpiling af material" at
the mine site becauseaf the extra handling required.
The material is usually placed an the starage pile by
meansaf a tipple arrangement ar a canveyar, as shawn in
Figure 3.8. Equipment such as bulldazers, frant~end laaders,
and small shavels may be used to. mave material within the
star age area ar pasitian it for laading aut af star age.
The emissian estimates presented in this sectian are,
with the exce~tian af dry phasphate rack, far unenclased
starage piles. In cald ar wet cl~mates, the material may be
placed in starage silas fram which it can be laaded directly
into. unit.trains. Silas vary in diameter, height, and
number depending an mine praductian and train scheduling.
Far caal, silas abaut 150 ft high and 70 ft in diameter with
a capacity af appraximately 11,000 tans are typical. The
. .
anly fugitive dust lasses assaciated with silas ar"ather
.enclased starage facilities are fram transfer and canveying;
which are cansidered as a separ.ate aperatian (see Sectian
3.7).
Also, the starage aperatian as defined
include tapsail ar waste material starage.
parts af ather aperatians, reclamatian and
herein daes nat
These are also.
waste dispasal.
55
-------
Figure
3.8.
Storage.
--
56
-------
Emission Est~m~te
Fugitive dust' emissions from the storage area occur as
a result of several activities. According to sampling data
compiled and evaluated by Midwest Research Institute,12 the
four major emission-producing activities and their approxi-
mate relative contributions for crushed rock storage are:
Loading onto piles
Equipment and vehicle
movement in storage area
Wind erosion
Loadout from piles
12%
40%
33%
15%
Although the percentage contributions from these activities
may vary for storage of different materials or for specific
storage area configurations, the same activities are prob-
ably the major dust sources for all types of open storage.
The MRI study produced emission factors applicable to a
wide range of aggregate storage operations, possibly includ-
ing crushed ore storage. These values are summarized in
Table 3.2. MRI also developed a climatic factor to correct
the emission estimates shown in Table 3.2 for different
geogra~hic areas: (100/PE)2, where PE is the annual precipi-
tatipn-evaporation index. a EPA has adopted the MRI emission
factor ~ased on tonriage throughput for storage piles with a
normal mix of activity for publication in the latest supple-
ment to their Compilation of A~r Pollutant Emission Factors:
0.33/(PE/100)2 lb/ton.
The Rittman report contained emission estimates for
aboveground coal storage for only two coal mining areas, the
a A national map showing PE values for
country can be found on p. 99 of EPA's
Pollutant Emission Factors, Supplement
all parts of the
Compilation of Air
No. 5 ~
57
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Table 3.2.
EMISSION FACTORS FOR CRUSHED ROCK.
STORAGE PILES
Activity rating
Activea
Emission factor
Ib/acre of Ib/ton placed
storage/day in storage
Inactive (wind
erosion only)
. b
Normal mlX .
13.2 0.42
3.5 0.11
10.4 0.33
a Eight to 12 hours of activity per 24-hr period.
b Five active days per week.
Source: Development of Emission Factors for Fugitive Dust
Sources, U.S. Environmental Protection Agency, Research
Triangle Park, North Carolina, Publication Number EPA 450/
3-74-037, June 1974.
58
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Northwest (Powder River Basin) and the Southwest (Four
Corners area). In the Northwest, emissions were assumed to
be "minimal" because of the rapid turnover of coal in stor-
age. The, emission factor for coal storage in the Southwest
was ,0.0235 lb/ton, based on the average wind erosion rate
for arid portions of the Great Plains, 428 lb/acre/yr. The
coal at the single mine for which this estimate is appli-
, ,
cable is stored iri piles 90 ft wide, 800 ft long, arid 30 ft
high, containing about 30,000 tons of blended coal.
A coal storage pile was sampled for dust losses by
Monsanto Research. On two separate runs, the coal pile
produced emissions at rates of 0.009 and 0.016 lb/ton in the
pile (static rate); these were converted 'to an annual emis-
sion rate of 0.054 lb/ton placed in storage by use of addi-
, 23,
tional information on the storage throughput rate. It
was indicated that no loading or unloading took place in the,
storage area during either of the sampling periods.
Monsanto Research, performed a simil'ar sampling study
for a phosphate rock storage pile and developed an averag~
emission factor of 0.20 lb/ton of "wet" rock in open stoi-
age. The phosphate rock may be shipped wet to the chemical
processing plant or it may be dried at the mine site.
Because of the difficulty in handling the material after it
has been dried~ the trend is toward locating the driers and
grinders at the chemical processing plant rather than at the
mine. However, if the phosphate rock is dried on-site, then
subsequent storage prior to shipment is a major fugitive
dust source even though the dry phosphate rock must be
stored in an enclosure. !PA's ~ublished emission factor for
transfer and stor~ge of dry rotk is 2.0 lb/ton uncon-
trolled..20 Source test data ~nd' company estimates of mater-
ial loss collected by PEDCo for nine phosphate industry
plants and. mines in Florida indicated exactly the same
, '
average uncontrolled emission rate as the EPA value--2.0
59
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1b/tort.Overa1l control efficiencies for storage buildings
of 90 to 95 percent can be obtained by use of baghouses or
scrubbers on vents and at transfer points within the building. .
3.10 WASTE DISPOSAL
Description
In the mining and beneficiation of minerals and ores,
large amounts of waste material are often generated.
Examples of this waste material are low grade ore; slack
coal, extraneous unmarketable rock of relatively large size,
tailings, coal slurry, and mud slime. The waste may have
the same handling characteristics as the raw mater~a1 being
mined and be disposed of in a fill such as shown in Figure
3.9. (e.g., a waste dump, leach pad, or gob pile) , or the
waste may be a slurry resulting from a cleaning or separa-
tion process which requires ponding.
The waste disposal operation is distinguished from
. .
overburden disposal because in most cases the area used for
wastes is not reclaimed. The wastes are segregated and
saved for future reprocessing, for byproduct recovery, or
because they contain higher concent~ations of toxic mater-
ia1s.than the overburden. .If the waste contains no poten-
tially recoverable material and its toxic components do not
create a leaching problem, it can be buried in the spoils
for disposal.
Some of the activities associated with waste disposal
are the same as for the mining of the ore, i.e., truck
loading and dumping, haul road traffic, scraper operation,
and grader operation. For purposes of estimating emissions
by unit operation at the mine, movement of waste material
should not be considered a distinct operation from the
60
-------
Figure
3.9.
Waste disposal.
Source: Environmental Protection in Surface Mining of Coal,
U.S. Environmental Protection Agency, EPA 670/2-74-093, 1974,
P 66.
61
-------
primary activity (e.g., shovel/truck loading) unless it
employs different equipment or occurs at a separate location
such as the dump site.
The other aspect of waste disposal is the disposal site
itself. If berms or di~es are constructed to contain a
slurry waste, this ~ctivity is part of the waste disposal
operation. Also, dried or inactive ponds of fine waste
material, particularly copper tailings, are subject to
severe wind erosion 'if they are not stabilized.
Waste disposal at coal mines creates another potential
particulate air pollution source--spontaneous combustion of
coal refuse piles and gob piles. However, burning coal
waste piles are not fugitive dust sources, so they are not
included within the scope of this report.
Emission Estimate
Excluding the disposal site, most of the fugitive dust-
producing processes associated with waste disposal. utilize
the same equipment and activities as used in other mining
operations. Therefore, their emissions can be estimated by
comparison with these operations and application of appro-
priate emission factors.
The equipment activity which occurs at .the disposal
sitei such as berm construction or grading of a leach pad,
can generally be categorized as heavy earthwork construc-
tion. It may be appropriate to apply the emission factor
for heavy construction from Supplement 5 of EPA's Compilation'
of Air Pollutant Emission Factors--l.2 ton per acre of
active construction per month. However., this value is
applicable only in arid Western areas in which the sampling
to develop the emission factor was done.12
Emission estimates for dried tailings have been devel-
oped by PEDCo with use of the u.S. Department of Agriculture's
62
-------
wind erosion eq~ation.25These estimates are a function of
. . 17
regional climatic conditions and assume no surface crustlng:
Climatic £actora
Emissions,
ton/acre/yr
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1.0
1.2
1.3
2.6
4.0
5.3
6.6
8.0
9.3
10.6
.12.0
13.3
16.0
If complete crusting of the fine tailings material does
occur, emissions are reduced by about 80 percent. Approx-
imately the same emission reductions can be achieved by
either chemical or vegetative stabilization of the tailings.
For most waste dumps and gob piles, there are emissions
when the material is dumped onto the pile but probably no
additional emissions from wind erosion due to a lack of
small particles on the surface.
No other references were found which identified waste
of mines,
producing
operations as significant fugitive dust sources.
exception of tailings pile erosion at certain types
waste disposal is generally a very minor dust-
operation.
disposal
With the
a See Fig~re 3.11 fbr climatic factors for all parts of the
country.
63
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3.11 LAND RECLAMATION
Description
All surface mining causes considerable alteration of
the land on which it occurs and a.certain amount of the
surrounding area as well. Experience has shown that the
most successful land reclamation results whereprogrami are
prep1anned by the mine operators and become a concurrent
part of the daily operation of the mine.16 Segregation of
the various strata in overburden removal is. critical so that
inferior spoil can be buried under clean fill, with topsoil
returned to the surface to ensure successful revegetation.
This practice of continuous reclamation has already
been introduced in Section 3.1 where the earth moving
aspects of overburden removal were considered. In area
strip mining, drag1ines fill mined strips with overburden
removed from succeeding strips and topsoil is placed on top
to prevent rehandling. In contour mining, the reclamation
follows a pattern of grading and backfilling the bench
between the highwa1l and the downslope. In this type of
. .
surface mining, the topsoil can be stockpiled for a limited
time and replaced after the mining and grading have been
completed. In contour mining by the block cut method,
topsoil is removed and placed on graded areas ina single
operation.
Success in reclaiming mined land is determined to a
large extent by geographic location and climatic conditions.
.' .
Each location has its owh inherent problems to be dealt-with
if an area is to be returned to the o~iginal topography. In
contour mining operations in the East, careful practices of.
grading and backfilling can return natural drainage patterns
and contour to the land. Use of trees alone to revegetate
these areas was found to be unsatisfactory, due to the
64
-------
length of time required for the trees to establish them-
selves and the loss of soil.byerosion in the interim.
. .
Presently,' herbaceous species are preferred to stabilize the
land. rapidly and plant covers suitable to the area are
selected to control erosion, siltation, dust, and acid
formation. In addition, seeding is no longer limited to the
spring. Selecting species appropriate to the season when
planting is needed and following with a.perennial species in
.spring qr fall provides optimum conditions for revegetation.
In these Eastern states, as well as those Central states
where contour mining is used, a period of two to three years
is required to reach this condition.9
In Florida, area mining is practiced where phosphate
. .
rock is mined. Draglines strip overburden and fill the
previous strip with this material in a single operation.
The overburden is approximately 20 ft deep, with phosphate
deposits of some 16 ft lying below. Land reclamation gener-
ally results in an area being filled and then graded tb a
level somewhat less than the original topography. Since the
water table is comparatively close to the surface, this
. .
depression usually creates lakes but the process is completed
. and the area stabilized in one to two years.26
Area mine .reclamation in Midwestern states p~ses the
fewest reclamation problems. These lands can be returned to
their original topography by spoil segregation, backfilling,
and grading as deposits are removed. Compaction of the soil
can be controlled with conve~tional equipment, and this
ground preparation for revegetation is aided by a climate
that provides sufficient annual precipitation.
Reclamation in the West is another matter. Here tHe
seam thickness of deposits mined is much greater and the
original elevation cannot be restored. If a pattern of
continuous reclamation is used at these mines,' the over-
burden is deposited by draglinesparallel to the strip being
65
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mined; smaller draglines or bulldozers then level these
deposits to reduce slopes. This returns the area to a
topography that will meet proper conditions for land sta-
bility, drainage control, and maintenance of vegetation. A
recently regraded area is shown in Figure3.l0. The process
of. reestablishment is estimated to require a minimum of five
years. Due to the arid or semiarid climate, successful
reclamation to native climax vegetation is questionable.
The extreme climatic conditions, with a seasonal variation
of -60 to 1200 F and an annual precipitation for 75 percent.
of the area of less than 20 inches, create a soil of highly
saline condition that contributes to a lack of adequate -
topsoil. Wind also erodes this unprotected soil, adding to
the problems of reestablishment. It is possible to regrade
this disturbed land but knowledge for successful seeding and
procedures for revegetating the area are not yet adequate.
In certain areas, such as the rimrock country in eastern
Montana, it has been recommended that no mining be permitted
in certain deposits. Here it would be impossible to restore
the original drainage patterns and slopes.
The amount of soil loss due to wind erosion of the
barren land prior to revegetation is a function of the
surface soil type, roughness of the surface, windspeed,
average surface moisture content, and unsheltered distance
across the regraded area. Obviously, the total wind erosion
losses from a reclaimed area are directly proportional to
the length of time to establish protective vegetation on the
. .
surface. While these wind erosion losses are low level
except during wind storms, they occur fairly continuously
over the entire reclamation area and therefore may produce
more fugitive dust than the mining and processing operations
in some high wind erosion areas of the country.
66
-------
-..,~ -,~,
~-
""II:""
~:
$i!'jj
.
1
Figure
3.10.
Reclamation.
67
-------
Emission Es.tirn:ate
For continuous reclamation, the earthmoving by the
dragline and scrapers produces a large amount of fugitive
dust, but these emissions are already included as part of
the overburden removal operation. If the topsoi'l is stored
and later redistributed or if a smaller dragline or bull-
dozer is used to grade the spoils area before applying the
topsoil layer, emissions from these activities can be esti-
mated with the same emission factors as for overburden
removal.
All other emissions associated with the reclamation
operation are due to wind erosion over the unreclaimed or
partially reclaimed land. Emissions from wind erosion
across cleared or unprotected soil surfaces have been esti-
mated by use of the u.s. Department of Agriculture's wind
erosion equation in several recent studies. The wind ero-
sion equation was originally developed to estimate soil
.' 12
losses from cropland, but has been.adapted to predict the
suspended particulate fraction of total soil losses and has
been applied to evaluate exposed soil surfaces other than
cropland.
The modified wind erosion equation is as follows:
E = a I K C L' V'
.< eq . 2 )
where E = emission factor, ton/acre/yr
a = portion of total wind erosion losses
that would be measured as suspended
particulate
I = soil erodibility,
K = surface roughness
C = climatic factor
L' =. unsheltered field width factor.
ton/acre/yr
factor
V' = vegetative cover factor
68
-------
In this equation, K, C, LI, and VI are all dimensionless.
27
Some recent work. has indicated that the variable "a,"
as well as.I, is related to soil type. Values for "a" and I
which. might be appropriate to surface mined areas during or
following regrading are summarized below:
Surface .so.i1. type
.a
. I ,. t.on/ ac.re/yi: .
. Rocky, gravelly
Sandy
Fine
Clay loam
0.025
0.010
0.041
0.025
38
134
52
47
Values for K can vary between 0.5 and 1.0, with 0.5
denoting a surface with deep furrows and ridges, which
protect against wind erosion, and 1.0 denoting a smooth
. .
erodible surface. Unless the surface of a regraded spoil
area has been plowed or roughened, a K factor of 1.0 should
be used in the wind erosion equation.
Climatic factors (C) for use in the equation have been
determined for most parts of the country by USDA, as shown
in Figure 3.11 (the values in the figure should be multi-
plied by 0.01). For exposed areas greater than about 2000
ft wide, the field width (L) no longer ~ffects the emission
rate and LI = 1.0. For smaller reclamation areas. in irregu-
lar terrain where the field .width is only about 1000 ft, the
LI value is approximately 0.7. Since there is little or no
vegetation on the recently regraded surfaces, VI in the
equation is' almost always 1.0~
By substituting the appropriate data into the wind,
erosion equation, the annual emission rate for any specific
situation can be calculated. This e~timated emission rate
(E) is then
mine during
dust due to
multiplied by the number of barren acres at the
a particular year to determine total fugitive
wind erosion. For a.more detailed explanation
69
-------
~
o
. ,
/
i
I
I
I
I
Figure 3.11.
Climatic factors for use in the wind erosion equation.
Source:
Armbrust, D. V. and N. P. Woodruff, 1968.
-------
of the modified wind erosion equation, see Appendix A of .
Development of Emis.s.ion Fac.to.r.sfor. Fugitive. Du.st Sources .12
While this method of estimating wind erosion .emissions.
is acknowledged to have limited acduracy, no other method
has been proposed. All efforts to quantify wind erosion
emissions which were found in the literature used some
published USDA data on annual soil losses per acre as their
basis. Because the emission rates p~r unit time from wind
erosion are very low and highly variable, it is not possible
to check the accuracy of the estimates by comparison with
source sampling. results.
71
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4.
SUMMARY
Eleven different mining operations were evaluated for
their potential as fugitive dust sources. Although these
operations do not have the same emission rates at all mines
or in all mining industries, the intent of this report was
to identify operations that may be major dust sources at
mines.
Emission estimates for the mining operations are summa-
rized in Table 4.1. These estimates should be used only
after reviewing the descriptions in Chapter 3 relevant to
their development and applicability. From these emission
estimates and typical production rates, it can be determined
that the approximate ranking of operations in order of
decreasing emission ratas is:
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
Overburden removal
Haul roads
Reclamation
Storage
Shovels/Truck loading
Transfer and conveying
. Truck dumping
Blasting
Crushing
Waste disposal
Cleaning
Overburden removal is much more of a dust problem at
surface coal mines and phosphate rock mines than at copper
72
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Table 4.1.
SUMMARY OF EMISSION ESTIMATES FOR MINING OPERATIONS
....J
W
NO. of Emission factors by industry More
emission data
Operation estimates . Range Units Coal CoppeI Rock P205 rock needed
Overburden 5 0.0008-0.45 lb/ton of ore 0.0008
removal 0.048-0.10 lb/ton of 0.05 x
overburden
Blasting 2 0.001-0.16 lb/ton of ore x.
Shovels/True 5 neg-0.10 lb/ton of ore 0.05 0.05 0.05 NA
loading
Haul roads 4 0.8-2.2 lb/VMT depends on speeds & controls x
Truck 3 0.00034-0.04 lb/ton of ore 0.02 0.02 0.04 NA
dumping
Crushing 4 neg-0.7 lb/ton of ore. neg 0.044 x
Transfer & 5 neg-0.2 lb/ton of ore 0.15 x
conveying
Cleaning 0 usually neg neg
negligible.
Storage 5 0.0235-0.42 lb/ton of ore 0.054 0.33 0.33 0.20
3.5-13.2 lb/acre/day 10.4
Waste 1 neg-:-14.4 ton/acre/yr
disposal ,
Reclamation 1 use wind ero- ton/acre/yr depends on climate & soil x
sion equation I I I
NA = not applicable
-------
mines and rock quarries because of the greater amounts of
overburden material handled in the former mines. Fugitive
dust from reclamation is also associated primarily with coal
mining and phosphate rock mining, and results from regrading
of the spoils and wind erosion across the re9raded surfaces.
Haul roads are a major dust source at almost all mines, even
though they are normally kept watered. The remaining opera-
tions generate dust through the handling or processing of
the material being mined. Because of. this, emission rates
for most of them are highly dependent on the characteristics
of the material as mined, Le., moisture content, amount of
fines, hardness.
Some of the operations create dust only in a few
instances, such as copper tailings as a waste disposal
source or air blowing as a cleaning process for coal. Waste
disposal and cleaning operations generally are not signifi-
cant fugitive dust sources at mines.
In order to estimate the fugitive dust emissions that
stay suspended, an attempt has been. made to expre.ss the
.emission factors in terms of the fraction less than 30
microns diameter wherever possible. Since data were not
available to do this in all cases, some of the reported
emission estimates may overstate the impact of those opera-
tions on a regional scale.
Table 4.1 also note& those operations for which more
sampling or emission data are needed before reliable emis-
sion factors can be developed. More than half the opera-
tions, including thqse indicated to be the three largest
sources at mines, are on this list. Many of these opera-
tions have not been sampled previously because of extreme
. .
difficulties in defining a representative process for sam-
pling or because of special technical problems such as those
encountered with measuring blasting or wind erosion emissions.
74
-------
The. air qu~lity impact of fugitive dust from a specific
mining industry is a function of the number of mines and the
population exposed to their emissions. There are a rela-
tively large number of coal mines. The dusty Western sur-
face mines are in remote locations, but the Midwest surface
mines, although less dusty, are often in areas of moderate
population density. There are relatively few copper mines
and these are in isolated locations except for the mines
near Tucson, Salt Lake City, and Butte~ In all three of
these cities, fugitive .dust from mining is shown to cause
increased urban particulate concentrations. Stone quarries
account for the most mining sites and they are often located
near urban areas to reduce. transportation costs. Phosphate
rock is produced from relatively few mines, mainly in a
limited area of west central Florida. With the exception of
the cities of Lakeland and Winter Haven, population exposure
to these mining emissions is low.
The air quality impact of mining emissions is attenu-
atedby two additional factors. At many of the larger
mine~, the dust-producing activities occur in a pit that is
considerably below surrounding ground level. Emissions from
a depressed level have a lesser impact on ambient concentra-
tions than the same emissions would have at ground level or
from an elevated source. At other large mines, the property
extends for many miles from the points of emission origin so
that .concentrations may be negligible by the time the dust
plume reaches a property line.
75
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REFERENCES
Fugitive Dust from Mining Operations, Final Report, ,
Task No.6. Monsanto Research Corporation, Dayton,
Ohio. Prepared for u.S. Environmental Protection,
Agency, Research Triangle Park, North Carolina. May
1975.
2.
Mineral Industry Surveys, Coal--Bituminous and Lignite
in 1974. u.S. Department of the Interior, Bureau of
Mines, Washington, D.C. 1976.
3.
Mineral Industry Surveys, Copper Production in December
1975. u.S. Department of the Interior, Bureau of '
Mines, Washington, D.C. 1976.
4.
Mineral Industry Surveys, Stone in 1974. u.S. Depart~
ment of the Interior, Burea~ of Mines, Washington, D.C.
1975.
5.
Mineral Industry Surveys, Phosphate Rock, 1975. u.S.
Department of the Interior, Bureau of Mines, Washington,
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