20220108_Black_Thunder_Wy_PM-2.5

Thunder Basin Coal Company, LLC — Black Thunder Mine
A0000611 Application Analysis
Page 26
10.2.3 PM2.5 IMPACTS
The Division operates a PM2.5 sampler at Black Thunder Mine's 36 monitoring site. The sampler operates
for 24 hours every P day, in accordance with EPA sampling guidelines. Table 10-3 presents a summary
of the recent data from the sampler, and all monitored values are well below the NAAQS.
Table
10-3: Monitored PM2.5 at the Black Thunder Mine m3
Year
Annual Average
Annual PM2.5
98` Percentile 24-
Hour Average
24-Hour PM2.5
PM2.5
NAAQS
PM2.5
NAAQS
2012
4.9
12
16
35
2013
4.2
14
2014
3.9
10
3-Year Average
4.3
13
Notes:
1) To attain the annual standard, the 3-year average of the annual mean PM2_5 concentrations must not exceed 12.0 µglm3
2) To attain the 24-hour standard, the 3-year average of the 98th percentile of 24-hour concentrations must not exceed 35 µg/m3
Given the nature of the proposed modification and associated emissions from the Black Thunder Mine,
and the measured PM2.5 concentrations near the mine, the proposed modification will not prevent the
attainment or maintenance of air quality standards for PM2.5.
10.3 ANALYSIS OF LONGTERM PM10 IMPACTS
10.3.1 PM,o Emission Inventories/Selection of Worst Case Years
The applicant developed a summary of the mining activity proposed for the Black Thunder Mine for all of
the years in the mining plan, and then developed fugitive PM10 inventories from this information. Similar
inventories were developed for the nearby mines, which include the exiting School Creek, NARM, and
Antelope mines. Because it is not practical to model all of the years in the life of the mines, the applicant
compared life -of -mine fugitive emissions for the mines, and determined the years which would likely
yield the highest modeled impacts. These "worst -case" years were modeled and the results were
compared to the annual ambient air quality standard. If the maximum predicted impacts from the worst -
case years are below the standard, then it is assumed that the impact from other years in the life of the
mine will fall below the ambient standard.
Fugitive and point source emissions for the nearby mines were taken from the most recent permits or
permit applications that reflect the currently permitted or proposed configurations at the mines. Annual
fugitive PMIo emissions were summarized and evaluated, not just as to the highest total, but also the
location of the mining activity in relation to LNCM boundaries. If the distance from the mining activity
to the LNCM boundary is small, impacts to the receptors along the LNCM boundary may be higher.
Point source emissions are assumed not to vary significantly from year to year and are usually excluded
from the process of selecting the worst -case years.

Thunder Basin Coal Company, LLC — Black Thunder Mine
A0000611 Application Analysis
Page 27
Based on the operating parameters and projected fugitive PMIo emission inventories for the South Group
of Mines, the years 2018 and 2023 were selected to represent the "worst -case" years to simulate in the
modeling analyses for PMIo. Year 2018 was selected as it represents the highest regional PMIo emissions
within the next five (5) years and 2023 was chosen as it represents the highest total emissions from the
South Group of Mines and from Black Thunder Mine itself. Those two years were also used to model
NO2 impacts. Table 10-4 presents calculated fugitive PMIo emissions for the Black Thunder Mine for the
two (2) modeled years.
Table 10-4: Black Thunder Mine Estimated Fugitive PMIo
Emissions 2018 and 2023
Emission Source
2018 PMIo
Emission Rate
2023 PMIo
Emission Rate
Scraper
48.39
48.39
Overburden Removal dra line
1,217.26
1,210.82
Overburden Removal (shovel)
1,864.61
2,194.34
Coal Removal shovel
59.85
59.85
Coal Dumping
54.51
54.51
Wind Erosion
834.37
948.14
Overburden Haul Road
965.14
17138.63
Coal Haul Road
985.77
1,197.90
Grader
318.36
383.20
Dozer
407.84
416.82
Water Trucks
45.91
55.26
Overburden Blasting
8.37
8.89
Coal Blasting
5.34
5.34
Overburden Drilling
0.57
0.35
Coal Drilling
0.12
0.07
Totals
6,816.41
7,722.51
tpy = tons per year

Thunder Basin Coal Company, LLC - Black Thunder Mine
A0000611 Application Analysis
Page 28
Calculated fugitive emissions as presented by the applicant for the South Group of Mines are shown in
Table 10-5.
Table 10-5: South Group of Mines
Fu itive PMIo Emission Summaries
Year
Black Thunder
School Creek
NARM
Antelope
Totals
2015
6,375
1,051
3,645
2,153
13,224
2016
6,512
916
35676
2,367
13,471
2017
6,817
992
3,674
2,519
14,002
2018
6,816
1,035
3,501
2,792
14,144
2019
6,475
1,081
3,703
2,716
13,975
2020
6,787
19109
31)793
2,712
14,401
2021
6,657
1,252
3,858
2,757
14,524
2022
6,901
1,158
3,975
2,809
14,843
2023
7,722
1,134
3,471
2,802
15,129
2024
6,769
1,150
3,383
2,821
14,123
2025
6,881.
1,123
3,314
2,781
14,099
2026
5,212
1,126
3,320
2,781
12,439
2027
3,438
1,096
3,366
2,780
10,680
2028
4,111
1,138
3,274
2,801
11,324
2029
4,869
833
3,632
2,827
12,161
2030
5,043
--
--
1 2,858
7,901
2031
5,864
--
--
1 1,656
7,520
The emission rates associated with each of the mines for the worst -case years were verified by the
Division, and these calculations are contained in Appendix B (2018) and C (2023) of this analysis.
10.3.2 Emissions Apportioning
Fugitive emissions for the worst -case years were apportioned into multiple area and volume sources based
on the location and extent of mining activities.
A detailed accounting of the apportioned particulate emissions and sources is contained in the permit
application. The area/volume sources that were used to represent the 2018 and 2023 PMja emissions at
the mines in the South Group are shown in Figures 10-5 and 10-6.
Fugitive and point source emissions for NARM were taken from the permit application for Permit MD-
16282. Fugitive and point source emissions for the Antelope Mine were taken from the permit
application for Permit MD-13361, and similar information for the School Creek Mine was obtained from
the permit application for Permit MD-6445.

Thunder Basin Coal Company, LLC— Black Thunder Mine
A0000611 Application Analysis
Page 29
Figure 10-5: Fugitive PM1a Sources for 2018
465000 470000 475000 480000 485000
1 1 I Ii
4845000 = `
T
i Black
4840000 Thunder
Mine
4835000
d
�School
Creek Mlne
V 4830000
v
ba
C
r
t
4825000
!1=301111I1I11
4815000
4810000
I I NARM
Mine
465000 470000 475000 480000 485000
VPM Easting (meters) (Zone 13, NAD Yn

Thunder Basin Coal Company, LLC — Black Thunder Mine
A0000611 Application Analysis
Page 30
Figure 10-6: Fugitive PMIe Sources for 2023
465000 470000 475000 480000 485000
, � I 1
11
4845000
Black
Thunder
4840000
- f
Mine
4835000 � 835000
h School I I`
w Creek Mine
E 4830000 830000
ao
e:
A _
t
4825000- - 4825000
F
° NARM
4820000 - (`1 r---1 820000
48150001 I '' Antelope �4815000
`` Mine {
IS111I1I1I61
465000 470000 475000 480000 485000
UTM Easting (meters) (Zone 13, NAD 27)
10.3.3 PMIe Background Concentration
The Division requires that all mines in the PRB submit and justify an annual background PMIe
concentration to represent all background sources that are not explicitly input to dispersion modeling
analyses. The applicant determined that a background concentration of 11.2 µg/m3 was appropriate for
the mine, and the Division concurred.

Thunder Basin Coal Company, LLC — Black Thunder Mine
A0000611 Application Analysis
Page 31
10.3.4 PMIO Dispersion Modeling Results
To arrive at total predicted impacts for 2018 and 2023, the contributions from each mine were summed
and the annual background level was added. The Division employed the "Mine A/Mine B" policy where
appropriate for evaluating the final predicted ambient PM 10 concentrations.
The maximum model -predicted PMio concentration for 2018, including background, was 43.3 µg/m3.
This impact was predicted to occur along the northern LNCM of the Black Thunder Mine. For 2023, the
maximum model -predicted concentration, with background, was 45.6 µg/m3 and was predicted to occur
along the western LNCM of the Black Thunder Mine. All modeled impacts were below the WAAQS.
Results of the modeling are summarized in Table 10-6. Figure 10-7 shows the locations of the maximum
predicted impacts.
Table 10-6:
Summary of Modeled Annual
PMIOImpacts
UTM Location
Background
Total
Year
Predicted PM10 Impact
Concentration
Predicted
WAAQS
X (m)
Y (m)
(µg/m)
(µg/m)
Impact
(µg/m3)
( m3)
2018
477399
4846663
32.4
11.2
43.6
50
2023
468261
4841011
34.6
45.8
Note: U I M Coordinates are expressed in NA L) 27, Lone 13.

Thunder Basin Coal Company, LLC— Black Thunder Mine
A0000611 Application Analysis
Page 32
4845000 -�
Figure 10-7: Maximum PM1a Locations
469000 474000 479000 484000
2018 IMPACT = 43.6 pg%m3
All Sources
conabution from Black Thunder = 30.2 pgW
2023 IMPACT = 45.8 pgW
All Sources
contribution from Black Thunder = 30.7 pgW
Black Thunder Mine
z
I School Creek
Mine
F.
I
4825000
25000
NARM
Le
I ! L
4820000
820000
_t .,.1
L .o
I IL I
I —
4815000
Li I
815000
J Antelope Mine EL J
I r
4810000
-
810000
464000
469000 474000 479000
484000
UTM Easting (meters) (Zone 13, NAD 27)