United States
Environmental Protection
Agency
Industrial Environmental
Research Laboratory
Cincinnati, OH 45268
Research and Development
EPA-600/S7-84-048 July 1984
Project Summary
Improved Emission Factors for
Fugitive Dust from Western
Surface Coal Mining Sources
Kenneth Axetell, Jr. and Chatten Cowherd, Jr.
The primary purpose of this study was
to develop emission factors for signifi-
cant surface coal mining operations
that would be applicable at Western
surface coal mines and would be based
on widely acceptable, state-of-the-art
sampling and data analysis procedures.
The approach was to develop emission
factors for individual mining operations
in the form of equations with correction
factors to account for site-specific
conditions. Factors were determined
for three particle size ranges—less than
2.5 fan (fine particulate), less than 16
Aim (inhalable particulate), and total
suspended particulate.
A total of 265 tests were run at three
mines during 1979 and 1980. The
following sources were sampled: Drill-
ing (overburden), blasting (coal and
overburden), coal loading, bulldozing
(coal and overburden), dragline opera-
tions, haul trucks, light- and medium-
duty vehicles, scrapers, graders, and
wind erosion of exposed areas and coal
storage piles. The primary sampling
method was exposure profiling; how-
ever, upwind-downwind, balloon, wind
tunnel, and quasi-stack sampling meth-
ods were used on sources unsuitable for
exposure profiling.
Several variables that might affect
emission rates, such as vehicle speed,
were monitored during the tests.
Significant correction parameters in the
emission factor equations were then
determined by multiple linear regres-
sion analysis. Confidence intervals
were also calculated for each of the
factors.
Data for determination of deposition
rates were obtained, but scatter in the
data prevented the development of an
algorithm. Control efficiencies for two
unpaved road control measures were
estimated.
The full report concludes with a
comparison of the generated emission
factors with previous factors, a state-
ment regarding their applicability to
mining operations, and recommenda-
tions for additional research in Western
and other mines.
This Project Summary was developed
by EPA's Industrial Environmental
Research Laboratory. Cincinnati, OH,
to announce key findings of the research
project that is fully documented in a
separate report of the same title (see
Project Report ordering information at
back).
Introduction
Operations of surface coal mines vary
from mine to mine, and the relative
amounts of dust produced by the different
operations will vary greatly. A ranking of
the sources was performed to determine
which significant particulate sources
warranted sampling, based on average
mine conditions. The most significant
dust-producing operations are shown in
Table 1.
Sampling Program
The number of mines to be surveyed
was set at three—a compromise between
sampling over the widest range of
mining/meteorological conditions by
visiting a large number of mines and
obtaining the most tests within the given
budget and time limits by sampling at only
a few mines. The three mines selected
were in diverse geographic areas in the
Western coal fields having the largest
strippable reserves: Fort Union (North
-------
Dakota), Powder River Basin (Montana-
Wyoming), and San Juan River (New
Mexico-Arizona). These mines had most
of the significant dust-reproducing
operations, and most operations could be
sampled at more than one location in
each mine. While sampling was limited to
several weeks at each mine, seasonal
variations in emission rates were consid-
ered by sampling during three of four
seasons.
A total of 265 tests (245 of them on
uncontrolled sources) were conducted
during four sampling periods. Table 1
summarizes the tests by mine and by
source. The total number of samples
required for each source to achieve a 25
percent relative error at a 20 percent risk
level was determined statistically. The
calculated sample size could not be
obtained from some sources because of
difficulties encountered in the field, such
as source inactivity, inability to place the
sampling array in the required location
due to topographical barriers, unstable
wind directions, and low or high wind-
speeds. A major effort was made to obtain
a statistically adequate sample size for
haul trucks, the major dust-producing
source.
Sampling Techniques
A thorough review of possible fugitive
dust sampling techniques indicated that
no one technique was adequate to
sample all sources. Exposure profiling,
designated as the preferred technique,
was used whenever possible (63 profiling
tests were performed). Each of the five
different sampling techniques used in the
study is described briefly in the follow-
ing paragraphs.
The exposure profiler consisted of a
portable tower (4 to 6 m in height)
supporting an array of sampling heads
Each sampling head was operated as an
isokmetic exposure sampler The air-flow
stream passed through a settling chamber
that trapped particles larger than about
50yum, and then flowed upward through a
horizontally position, standard 8x10 in.
glass fiber filter. Sampling intakes were
positioned directly into the wind, and
sampling velocities were adjusted to
match the mean wmdspeed at each
height (as determined immediately prior
to the test). Windspeed was monitored by
hot-wire anemometers throughout the
test, and flow rates were adjusted for
major changes in mean windspeed.
Operating concurrently with the profiler,
dichotomous samplers placed at two
heights on the tower determined particle
size distribution. Duplicate dustfall
Table 1. Summary of Tests Performed
Source
Drilling. ovbb
Blasting, coal
Blasting, ovb.
Coal loading
(shovel/truck or
front-end loader)
Bulldozing, ovb.
Bulldozing, coal
Dragline
Haul trucks
Light- and
medium-duty trucks
Scrapers
Graders
Exposed area, ovb.
Exposed area, coal
Total
Sampling
technique
Quasi-slack
Balloon
Balloon
Uw-dwc
Uw-dw
Uw-dw
Uw-dw
Profiling
Profiling
Profiling
Profiling
Wind tunnel
Wind tunnel
Mine 1
11
3
2
2
4
4
6
7"
5
5"
11
10
70
Mine 2
-
6
8
7
3
5
9
5
6
5
14
7
75
Mine 1W*
12
10*
2
3
6
33
Mine 3
7
7
3
IS
4
5
8
9
3
2
2
6
16
87
Total
30
16
5
25
15
12
19
35
13
15
7
34
39
265
^Winter sampling period.
"ovb. = overburden.
0 Uw-dw = upwind-downwind.
aFive of these tests were comparability tests (profiling and upwind-downwind).
"Six of these tests were done by upwind-downwind.
buckets located at the profiler and 20 and
50 m downwind of the source provided
information on deposition.
The exposure profiler concept was
modified for sampling blasting operations.
The large horizontal and vertical dimen-
sions of the blast plumes required a
suspended array of samplers as well as
ground-based samplers in order to
sample over the plume cross-section in
both dimensions. Five 47-mm polyvinyl
chloride (PVC) filter heads and sampling
orifices were attached to a line suspended
from a tethered balloon. The samplers
were located at different heights (2.5,7.6,
15.2, 22.9, and 30.5m), and each sampler
was attached to a wind vane so that the
orifices would face directly into the wind.
The samplers were connected to a
ground-based pump with flexible tubing.
The pump maintained an isokinetic flow
rate for a windspeed of 5 mph. To avoid
equipm'ent damage from blast debris and
to obtain a representative sample of the
plume, the balloon-suspended samplers
were located about 100 m downwind of
the blast area. The balloon-supported
samplers were supplemented with five
hi-vol/dichotomous sampler pairs spaced
20 m apart and located on an arc at the
same distance as the balloon from the
edge of the blast area.
The upwind-downwind array used for
sampling point sources included 15
samplers (10 hi-vol and 5 dichotomous).
One of each sampler type was located
upwind of any dust from the source.
Initially, downwind samplers were placed
at nominal distances of 30, 60, 100, and
200 m; however, these distances had to
be frequently modified because of physical
obstructions (e.g., highwall) or potential
interfering sources. Two samplers of
each type were placed at a distance of 30
m, three hi-vols and two dichotomous
samplers at 60 m, three hi-vols at 100 m, |
and one hi-vol at 200 m. Both sampler
types were mounted on tripod stands at
a height of 2.5 m, the highest manageable
height for this type of rapid-mount stand.
The downwind array was modified
slightly for sampling line sources. It
consisted of two pairs of hi-vol/dichoto-
mous samplers at 5, 20, and 50 m and
two hi-vols at 100 m. The two rows of
samplers were separated by 20 m. The
upwind-downwind method allowed in-
direct measurement of deposition through
calculation of apparent emission rates at
a series of downwind distances.
A portable wind tunnel consisting of an
inlet section, a test section, and an outlet
diffuser was used to measure dust
emissions generated by wind erosion of
exposed areas and storage piles. The test
section has a 1 by 1 ft cross section so it
could be used with rough surfaces. The
open-floored test section was placed
directly on the 1 by 8 ft surface to be
tested, and the tunnel air flow was
adjusted to predetermined values that
corresponded to the means of NOAA
windspeed ranges. Tunnel windspeed
was measured by a pitot tube at the
downstream end of the test section and
related to windspeed at the standard 10
m height by means of a logarithmic^
profile. An emission-sampling module™
-------
was located between the tunnel outlet
and the fan inlet to measure particulate
emissions generated in the test section.
The sampling train, which was operated
at 15 to 25 ft vmin, consisted of a tapered
probe, cyclone precollector, parallel-slot
cascade impactor, backup filter, and hi-
vo\ motor. Interchangeable probe tips were
sized for isokinetic sampling over the
desired tunnel windspeed range.
For quasi-slack sampling of overburden
drilling, a wooden enclosure with 4 by 6 ft
end openings was fabricated in the field.
During each test, the enclosure was placed
adjacent to, and downwind of the drill
platform. The cross section of the
enclosure was divided into four rectan-
gles of equal area, and a hot-wire
anemometer measured wind velocity at
the center of each rectangle. Four
exposure profiler samplers with remote
flow controllers were used to sample in
the four enclosure subareas. Sampler
flow rates were adjusted at 2-to 3-minute
intervals to near-isokinetic conditions
with the windspeed measurements. This
sampling technique did not measure
particle size distribution of deposition.
Source Characterization
Many independent variables influence
particulate emission rates from mining
sources. If these variables are to be
quantified and included as parameters
(correction factors) in the emission factor
equations, suspected variables must be
measured for each emission test.
Summary of Results
Total suspended particulate (TSP) and
inhalable particulate (IP) emission rates
are presented in Table 2. For some
sources, the number of test values is
lower than the number of tests reported
in Table 1. This indicated elimination of
data after a test was completed. For
example, the plume may have missed the
sampling array for most of the period or
the sampler may have malfunctioned.
Most of the tests for which no data are
presented in Table 2 (36 out of 44) were
run on exposed areas. These tests were
unproductive because eroding particles
could not be generated on the test
surfaces, even at the highest windspeed
simulated in the wind tunnel.
The geometric mean values in Table 2
are not emission factors; no consideration
has been given to correction factors at
this point.
The relative standard deviations of
emission rates by individual sources
ranged from 0.7 to 1.5. Relative standard
deviation is a measure of sample variation.
Table 2. Emission Rates by Source
Source
Drilling, ovb."
Blasting, coal
Blasting, ovb.
Coal loading
(shovel/truck or
front-end loader)
Bulldozing, ovb.
Bulldozing, coal
Dragline
Haul trucks
Light- and
medium-duty trucks
Scrapers
Graders
Exposed area, ovb.
Exposed area, coal
No. of
values
30
14
4
25
15
12
19
33
11
14
7
10
27
Geometric mean Range of emission rates
emission rate from individual tests
Units
Ib/hole
Ib/blast
Ib/blast
Ib/ton
Ib/h
Ib/h
Ib/yd3
Ib/VMT
Ib/VMT
Ib/VMT
Ib/VMT
Ib/acre-s
/b/acre-s
TSP
1.16
28.7
74.3
0.039
3.70
46.0
0.050
9.1
2.43
24.3
5.8
0.0803
O.0980
IP
10.5
40.0
0.010
1.96
20.5
0.013
4.1
1.54
11.7
2.8
0.0549
0.0642
TSP
0.04-7.29
1.6-5140
35.2-270.0
007-1.090
0.9-20.7
3 0-439.0
0.004-0.400
0.6-73 1
0.35-9.0
3.9-355 0
1.8-34.0
0.0107-0.537
0.0096-2.27
IP
0.4-142.8
16.9-93.9
0.002-0.378
0.48-32.60
0.9-236.0
0.002-0.061
0.4-42. 1
0.34-5. 1
1.4-217.0
0.9-15.4
0.0073-0 336
0.0053-1.40
"ovb. - overburden.
For most sources with at least 10 data
points, emission rates varied more than
two orders of magnitude; however,
similar variations were noted in inde-
pendent variables thought to have an
effect on emission rates.
Multiple Linear Regression
Analysis
The method for developing correction
factors was based on multiple linear
regression (MLR). Briefly, values for all
variables being considered as possible
correction factors were first tabulated by
source along with the corresponding TSP
emission rates for each test. The data
were then transformed to their natural
logarithms (In) because a preliminary
analysis had indicated the emission rates
were lognormally rather than normally
distributed. The transformed data were
applied to the MLR program, specifying the
stepwise option and permitting entry of
all variables that increased the multiple
regression coefficient.
Wind Erosion Sources
The emission rates reported in Table 2
for wind erosion from coal pile surfaces
and exposed ground areas were obtained
by testing several naturally occurring
surfaces at successively increasing
windspeeds simulated in the wind
tunnel. Analysis of SP (the size fraction
less than 30 /urn) and IP emission rates
indicated that the rates (1) increased with
windspeed above a threshold level on
newly exposed surfaces and (2) decreased
sharply with time after the onset of
erosion.
Threshold velocities for detectable
movement of surface particles were
unexpectedly high. This was attributed to
the presence of natural crusts on many of
the surfaces tested. The decay in emission
rates with time was explained by the
limited quantity of particles in any
specified particle size range present on
the surface (per unit area) that could be
removed by wind erosion at a particular
windspeed. The available quantity, or
erosion potential could be restored by a
disturbance of the surface such as the
addition or removal of material from a
storage pile or the plowing of an exposed
ground area.
Particle Size Distribution
Emission factors were developed for
three size ranges—fine particulate (FP,
<2.5 um); inhalable particulate (IP, <15
urn); and total suspended particulate (TSP,
no well-defined upper cut point, but
approximated as 30 um). Dichotomous
samplers generated the FP and IP data
and hi-vol samplers generated the TSP
data. Suspended particulate (SP) emission
rates determined from exposure profiling
tests were not actually TSP; rather, these
rates were the fraction of total particulates
less the 30 fjm in aerodynamic diameter.
Only a calculated estimate of the sus-
pended fraction could be made because
the profiler samplers indiscriminately
collect all particle sizes present in the
plume.
Independent data analyses were per-
formed on IP qnd TSP/SP data to derive
emission factors for these two size
ranges. Data analysis problems associated
with the very low concentrations prevented
determination of emission factors for the
FP size fraction by calculation of emission
rates followed by multiple linear regres-
sion. Instead, net FP concentrations for
-------
all tests were expressed as a fraction of
TSP or SP, and the average fraction for
each source was applied to the TSP/SP
emission factor for that source to
calculate an FP emission factor.
Table 3 shows the average ratios of FP
and IP to TSP or SP emission rates by
source. The IP fractions were reasonably
consistent, varying from 0.30 to 0.67. In
general, these ratios were lower than the
frequently quoted average ratio of 0.65
for urban ambient monitoring. These
ratios were based on measurements
taken near the sources. As the emissions
proceed downwind, greater deposition in
the TSP fraction should increase the
ratio.
The variation of FP/TSP ratios was
much wider, from 0.026 to 0.196. The
0.196 value for bulldozing overburden
appeared to be an anomaly, however.
Exclusion of this value makes the range
0.026 to 0.074. The fairly consistent
ratios of FP and IP to TSP for different
sources indicate that the size distribution
is similar in all fugitive dust sources at
mines.
Three different particle sizing methods
were evaluated early in the study—
cascade impactors, dichotomous sam-
plers, and microscopy. Side-by-side com-
parison of these methods showed that
the cascade impactors and dichotomous
samplers gave approximately the same
particle size distributions. In contrast,
the microscopy data varied widely. It was
concluded that microscopy is a useful tool
for semiquantitative estimates of various
particle types, but it is inadequate for
primary particle sizing of fugitive dust
emissions. Despite several unresolved
problems involved in the generation of
fine particle data for fugitive dust
sources, data from the present study are
thought to be reasonable based on their
consistency and the observed agreement
between dichotomous and cascade
impactor data.
Deposition
The emission factors in this study were
all developed from sampling data obtained
very near the source. Emissions are
subject to deposition as distance from the
source increases
A secondary objective of this study was
to develop a deposition function specifi-
cally for use with the mining emission
factors. Deposition rates were measured
by two different methods—dustfall catch
and apparent source depletion at succes-
sive distances from the source. Although
initial side-by-side testing of the two
methods indicated that apparent source
Table3. Average Particle Size Distributions by Source
Source
Blasting
Coal loading
Bulldozing, coal
Bulldozing, ovb.
Dragline
Haul trucks*
Light- and
medium-duty
vehicles*
Scrapers*
Graders*
Coal storage piles*
Exposed areas'
No. of tests
18
24
12
14
19
28
11
14
7
27
10
Average
IP /TSP
0.46
0.30
0.49
0.54
0.32
0.52
0.65
0.49
0.48
0.61
0.67
Std dev.
of IP/ TSP
0.29
0.15
0.24
0.50
0.22
0.08
0.16
0.07
0.10
0.08
0.06
Average
FP/TSP
0.051
0.030
0.031
0.196
0.032
0.033
0.074
0.026
0.055
Std. dev.
of FP/TSP
O.O39
0.035
0.033
0.218
O.O40
0.037
O.O78
0.021
0.041
'Expressed as fractions of SP (<30 (imj rather than TSP.
depletion gave the better results, dustfall
measurements were still taken at 5, 20,
and 50 m from the source as part of the
exposure profiling tests; these dustfall
measurements proved to give much more
reliable estimates of deposition rates
during most of the sampling at the three
mines.
The deposition rates by test were
correlated with several potential variables
such as windspeed and particle distribu-
tion. These analyses did not reveal any
significant relationships that could form
the basis for an empirical deposition
function. Because these analyses were
nonproductive and the primary method
for measuring deposition (apparent
source depletion in upwind-downwind
sampling) gave unusable results, a
deposition function cannot be presented
at this time
If additional testing is performed to
develop a deposition function, dustfall
measurement is recommended as the
sampling method. The main shortcoming
of dustfall as a measurement of deposition
is that it measures total paniculate rather
than the amount of deposition in the TSP
or IP range.
Control Measures
Two mining control measures—appli-
cation of water and application of a
calcium chloride solution—were evaluated
by comparing emission rates from treated
and untreated areas. Testing was done on
the same or adjacent lengths of roadway
under similar traffic and meteorological
conditions so that the only substantial
variable between test pairs was applica-
tion of the dust control. The number of
tests available for determination of
control efficiencies was limited and sta-
tistically inadequate.
The results of 1-hour test periods
immediately after watering (shown in
Table 4) indicate that water at a rate of
0.05 gal/yd2 reduced paniculate emis-
sions from haul roads by 60 to 70 percent
and those from coal loading by 78
percent. Maintenance of that range of
efficiencies would require the reapplica-
tion of water at an approximate frequency
of once per hour. Results showed that
calcium chloride still reduced paniculate
emission rates from an access road by 95
percent about three months after its
application, but no information was
obtained on the life expectency of this
control. Application rate for the 30
percent solution of calcium chloride was
0.6 gal/yd2.
Table 4 shows that control efficiencies
for IP were essentially the same as those
for TSP, whereas those for FP were
slightly lower. The 60 to 70 percent
control efficiency for watering haul roads
was higher than the 50 percent widely
reported in the technical literature,
possible because testing was done right
after the water was applied.
.Comparison of Sampling
Techniques
The two major sampling techniques,
exposure profiling and upwind-downwind
sampling, were run simultaneously on a
common source for several tests to
determine relative performance.
Profiling towers and the upwind-
downwind samplers (hi-vols and dichoto-
mous samplers) were placed 5, 20, and
50 m downwind of the sources to
measure the decrease in paniculate flux
with distance. This design allowed the
indirect determination of deposition
rates. Duplicate hi-vols and dichotomous
samplers were placed at each of three
distances, and two additional hi-vols
were located 100 m downwind of the
source. Upwind samplers consisted of
three hi-vols and a dichotomous sampler,
-------
Table 4. Control Efficiencies for Watering and Calcium Chloride
Avg. Emission
No. Tests
Source
Haul road.
Mine 2
Haul road.
Mine 3
Coal Idg..
Mine 3
Access
road.
Mine 1
Control
measure
Watering
Watering
Watering
Calcium
chloride
Size
fraction
TSP"
IP
FP
TSP"
IP
FP
rsp
IP
FP
TSP"
IP
FP
Uncon-
trolled
4
4
4
4
4
3
5
4
4
3
3
3
Con-
trolled
4
4
4
5
5
5
9
9
9
2
2
2
rate, Ib/VMT*
Uncon-
trolled
5.3
2.8
0.19
16.3
8.9
0.21
0.188
0.053
0.0028
6.8
5.4
0.74
Con-
trolled
2.2
1.1
0.08
5.0
2.4
0.10
0.042
0.010
0.0009
0.35
0.34
0.09
Mean
control
eff., %
59
61
58
69
73
54
78
81
68
95
95
88
"Emission factors for coal loading are expressed in units of Ib/ton.
b Measured as SP, the size fraction less than 30 um.
all located 20 m from the upwind edge of
the source.
Haul trucks and scrapers were selected
for sampling in the comparison study.
Because they are ground-level moving
point sources (line sources) that emit
from relatively fixed boundaries, both
sampling methods were applicable and
the required extensive sampling array
could be located without fear of the
sources changing location. Also, haul
trucks and scrapers are two of the largest
fugitive dust sources at most surface coal
mines.
Five tests of each source were run over
a 15-day period. All five tests of each
source were performed at the same site,
so only two sites (one for each source) and
one mine were involved in the comparison
study.
These data were subjected to Analysis
of Variance (ANOVA) to evaluate whether
differences in emission rates by sampling
method, source, and downwind distance
were statistically significant. Sampling
method and downwind distance were
found to have significant effects(cr = 0.20)
on both TSP and IP emission rates;
emission source (haul truck or scraper)
was not a significant variable. The
emission rates produced by profiling
averaged 24 percent higher for TSP and
52 percent higher for IP than correspond-
ing upwind-downwind emission rates,
according to the ANOVA results.
Both methods of sampling showed
large overall reductions in TSP and IP
emission rates with distance. In 6 of 10
tests, however, profiling showed lower
emission rates at the closest sampling
sites (5 m) than at the middle sites (20 m).
These inverted values were attributed to
a systematic bias between measurements
taken by two contractors, each of whom
operated one of these profilers. The
reduction of IP emission rates with
distance was surprising, because very
little deposition of sub-15 um particles
was expected over a 50-m interval.
The reason for the relatively poor
comparisons between emission rates
obtained by the two sampling/calculation
methods was traced primarily to the
precision of the samplers. It was not
possible to establish from the data which
sampling method was more accurate
because the paired results were compared
with each other rather than a known
standard. Error analyses performed, after
the side-by-side sampling led to the
conclusion that the accuracy of state-of-
the-art testing of fugitive emissions is
+25 to 50 percent with either of these
two sampling methods.
Conclusions
Resulting Emission Factors
The emission factors resulting from
this study (Table 5) are in the form of
equations with correction factors for
independent variables that were found to
have a significant effect (generally at the
0.05 risk level) on each source's emission
rates. The range of independent variable
values over which-sampling was con-
ducted, and for which the equations are
valid, are also shown in the table. Any
ambient air quality analysis using these
emission factors should have some
provision for considering deposition.
The 80 and 95 percent confidence
intervals for TSP were presented in the
report. The average 80 percent confidence
interval was -20 to +24 percent, less than
the relative error anticipated in the study
design.
The emission factors are for uncontrolled
emission rates. Control efficiencies of a
few control measures were estimated in
limited testing, of the report. These
control efficiencies should be applied to
the calculated emission factors in cases
where such controls have been applied or
are anticipated.
A comparison of the emission factors
developed in this study with others based
on actual testing in surface coal mines
indicated ratios of new to existing factors
ranging from 0.4 to 2.2.
Limitations to Applications of
Factors
Although these emission factors were
designed to be widely applicable through
the use of correction factors, the following
limitations should be considered in their
application:
1. The factors should be used only for
estimating emissions from Western
surface coal mines. There is no basis
for assuming they would be appropri-
ate for other types of surface mining
operations, or for coal mines located
in other geographic areas, without
further evaluation.
2. Correction factors used in the
equations should be limited to
values within the ranges tested (see
Table 15-1 of the full report). This is
particularly important for correction
factors with a large exponent,
because of the large change in the
resulting emission factor associated
with a change in the correction
factor.
3. These factors should be combined
with a deposition function for use in
ambient air quality analyses. After
evaluation of the deposition data
from this study, no empirical deposi-
tion function could be developed.
Any function subsequently devel-
oped from these data should have
provision for further deposition
beyond the distance of sampling in
this study (100-200m).
4. The factors were obtained by sam-
pling at the point of emission and do
not address possible reductions in
emissions from dust being contained
within the mine pit.
5. As with all emission factors, these
mining factors do not assure the
calculation of an accurate emission
value from an individual operation.
The emission estimates are more
reliable when applied to a large
number of operations, as in the
preparation of an emission inventory
for an entire mine. The emission
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Table 5. Summary
Source
Drilling
Blasting
Coal loading
Bulldozing,
coal
Bulldozing,
ovb.
Dragline
Scrapers
Graders
Light- and
medium-duty
vehicles
Haul trucks
of Western
TSP/IP
TSP
TSP
IP
TSP
IP
TSP
IP
TSP
IP
TSP
IP
TSP
IP
TSP
IP
TSP
IP
TSP
Surface Coal Mining Emission Factors
Prediction equation
for emission factor
1.3
961 A°«
D18/W19
2550 Aos
01S/W23
7./6//W12
0.119/M09
78.4 s1 2/M1 3
/S.6s15//W14
5.7s12/M13
;.Os15//W14
0.002; rf1V/M°3
0.002 / o°7/M°3
(2.7 x W-^s^W24
(6.2 x /0~V "W25
0.040S25
0.05/ S20
5.79 VM40
322 /M43
0.0067 w34L02
FP fraction
of TSP
None
0.03O
0.019
0.022
0.105
0.017
0.026
0.031
0.040
0.017
Units
Ib/hole
Ib/blast
Ib/ton
Ib/h
Ib/h
Ib/yd*
Ib/VMT
Ib/VMT
Ib/VMT
Ib/VMT
Range of correction
parameters
None
A =area blasted, ff
= 1076 to 103.334
M = moisture, %
= 7.2 to 38
D = depth of holes, ft
20 to 135
M =6.6 to 38
s = silt content. %
=6.0 to 11.3
M =4.0 to 22.0
s =3.8 to 15.1
M =2.2 to 16.8
d =drop distance, ft
=5 to 100
M =0.2 to 16.3
s =7.2 to 25.2
W = vehicle weight, tons
=36 to 64
S = vehicle speed, mph
=5.0 to 11.8
M =0.9 to 1.7
w = average number of wheels
IP'
0.005 r w35
=6.1 to 10.0
L =silt loading g/m2
=3.8 to 254.0
"Silt loading was not a significant correction parameter for the IP fraction.
factors are also more reliable when
estimating emission over the long
term because of short-term source
variation.
Appropriate adjustments should be
made in estimating annual emissions
with these factors to account for
days with rain, snow cover, temper-
ature below freezing, and intermit-
tent control measures
The selection of mines and their
small number may have biased final
emission factors, but the analysis
did not indicate that a bias exists.
The confidence intervals cited in
Table 13-10 of the full report esti-
mate how well the equations predict
the measured emission rates at the
geometric mean of each correction
factor. For predicting rates under
extreme values of the stated range
of applicability of the correction
factors, confidence intervals would
be wider
Error analyses for exposure profiling
and upwind-downwind sampling
indicated potential errors of 30 to 35
percent and 30 to 50 percent,
respectively, independent of the
statistical errors due to source
variation and limited sample size.
10. Geometric means were used to
describe average emission rates
because the data sets were dis-
tributed lognormally rather than
normally. This procedure makes
comparison with previous emission
factors difficult, because previous
factors were all arithmetic mean
values.
11. Wind erosion emission estimates
should be restricted to calculation
of emissions relative to other
mining sources; they should not be
included in estimates of ambient
air impact.
Recommendations
A comprehensive study that has
evaluated alternative sampling and
analytical techniques is bound to identify
areas where additional research would be
valuable. Also, some inconsistencies
surface during the data analysis phase,
when it is too late to repeat any of the field
studies. Therefore, a brief list of recom-
mendations for further study is presented
here.
Sampling at Midwestern and Eastern
coal mines is definitely needed so
that emission factors applicable to
all surface coal mines are available.
A resolution of which deposition
function is most accurate in describ-
ing fallout of mining emissions is
still needed. Closely related to this is
the need for a good measurement
method for deposition for several
hundred meters downwind of the
source (dustfall if recommended for
measurements up to 100 or 200 m).
In the present study, both the source
depletion and dustfall measurement
methods were found to have defi-
ciencies.
A method for obtaining a valid size
distribution of particles over the
range of approximately 1 to 50 /jm
under near-isokinetic conditions is
needed for exposure profiling. The
method should utilize a single sample
for sizing rather than building a size
distribution from fractions collected
in different samplers.
The emission factors presented
herein should be validated by sam-
pling at one or more additional
-------
Western mines and comparing
calculated values with the measured
ones.
Standardized procedures for hand-
ling dichotomous filters should be
developed. These should address
such areas as numbering of the
filters rather than their petri dishes,
proper exposure for filters used as
blanks, transporting exposed filters
to the laboratory, equilibrating
filters prior to weighing, and evalua-
tion of filter media other than Teflon
for studies where only gravimetric
data are required.
One operation determined in the
study design to be a significant dust-
producing source, shovel/truck
loading of overburden, was not
sampled because it was not per-
formed at any of the mines tested.
Sampling of this operation at a mine
in Wyoming and development of an
emission factor would complete the
list of emission factors for significant
sources at Western coal mines (see
Table 2-1 of the full report).
Further study of emission rate decay
over time from eroding surfaces is
needed. In particular, more informa-
tion should be obtained on the effect
of wind gusts in removing the
potentially erodible material from
the surface during periods when the
average wmdspeed is not high
enough to erode the surface
More testing of controlled sources
should be done so that confidence in
the control efficiencies is comparable
to that for the uncontrolled emission
rates.
Kenneth Axetell, Jr. is with PEDCo Environmental. Inc.. Kansas City, MO 54108;
and Chatten Cowherd, Jr. is with Midwest Research Institute, Kansas City, MO
64110.
Jonathan G. Herrmann and Thompson G. Pace are the EPA Project Officers (see
below).
The complete report, entitled "Improved Emission Factors for Fugitive Dust from
Western Surface Coal Mining Sources," (Order No. PB 84-170 802; Cost:
$23.50, subject to change) will be available only from:
National Technical Information Service
5285 Port Royal Road
Springfield, VA 22161
Telephone: 703-487-4650
The EPA Project Officer can be contacted at:
Industrial Environmental Research Laboratory
U. S. Environmental Protection Agency
Cincinnati, OH 45268
*USGPO: 1984-759-102-10615
-------
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Environmental Protection Information
Agency Cincinnati OH 45268
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Penalty for Private Use $300
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