1

The following summary of EPA’s revised modeling for BART sources in Wyoming differs from 

the document posted in the docket on January 8, 2013, in the following ways:

 Generally, the summary was updated to remove language from the previous summary that 

was no longer relevant.

 The summary was updated to clarify that, like pre-control emission rates, post-control 

emission rates were calculated in accordance with the BART Guidelines.

 Language stating that NOx baseline (that is, pre-control) emission rates were taken from 

Wyoming's "Baseline" scenario was removed as this is no longer the case. Language was 

inserted stating that, consistent with the BART Guidelines, pre-control emission rates were 

based on the maximum 24-hour average actual emission rates.

Scenario descriptions in Tables 1 and 2 were revised consistent with the above.

 The modeling results for Jim Bridger Units 1-4 have been added to the document.
2

Summary of EPA’s Revised Additional Visibility Improvement Modeling 

(Corrected 02/07/13)

In response to comments on our proposed rule, EPA has performed new CALPUF 

visibility modeling using revised emissions rates. All Region 8 modeling files are available upon 

request. Contact Laurel Dygowski at dygowski.laurel@epa.gov.

EPA had previously performed additional modeling of NOx control scenarios for both 

BART and reasonable progress sources. This modeling was performed to ascertain the visibility

improvements from individual NOx controls that the state and BART sources had not 

individually evaluated. For baseline (i.e., pre-control) emission rates, the BART Guidelines 

recommend that states use the 24-hour average actual emission rate from the highest emitting 

day of the meteorological period modeled.

1

 The visibility modeling performed by PacifiCorp, 

and subsequently submitted by the state, deviates from this guidance by using the permit limit

emission rates and maximum rated heat input to derive the modeled emission rates instead of the

actual maximum 24-hour average. The visibility modeling performed by Basin Electric, and 

subsequently submitted by the state, also deviates from this guidance by using baseline hourly 

emission rates derived from actual annual average heat input (MMBtu) and actual annual 

average emission rates (lb/MMBtu) from 2001-2003 continuous emissions monitoring (CEM) 

data. In addition, the BART Guidelines recommend that post-control emission rates be

calculated as a percentage of pre-control emission rates.2The visibility modeling performed by 

PacifiCorp and Basin Electric, and subsequently submitted by the state, deviates from the 

 

1

70 FR 39170

2

70 FR 39170
3

guidance by using post-control emission rates calculated in a similar manner to the baseline

emission rates.

For consistency, EPA previously completed additional modeling using the state’s 

baseline emission rates for the Pacificorp sources and Basin Electric’s Laramie River Station. In

response to comments that EPA should have followed the BART Guidelines for its additional 

modeling, EPA has now performed new modeling using the maximum 24-hour average actual 

emission rates for pre-control (i.e., baseline) scenarios. In addition, also consistent with the 

BART Guidelines, EPA has used post-control emission rates reflecting the percentage reduction 

expected with each control option. The results of this new modeling are summarized in this 

document. All other aspects of EPA’s additional visibility modeling followed the 

recommendations made in the State of Wyoming Department of Environmental Quality (WY 

DEQ) BART Air Modeling Protocol.

3

Table 1 describes the control scenarios for the Wyoming’s 

BART sources.

 Tables 3 through 15 show the CALPUFF inputs used for each unit modeled. EPA’s 

modeling modified the state of Wyoming’s emission inputs in order to isolate the impact of 

different NOx control scenarios. As seen in the tables, the NOx emission rates were varied 

across the different scenarios with the other input parameters held constant. For the Pacificorp 

and Basin Electric BART sources, the emission inputs for pollutants other than NOx, as well as 

stack parameters, were derived from the state of Wyoming’s BART Application Analyses that 

can be downloaded from the following website: 

http://deq.state.wy.us/aqd/309(g)%20Attachment%20A_January%202011%20Submittal.asp

 

3

State of Wyoming Department of Environmental Quality Air Quality Division BART Air Modeling Protocol – Individual 

Source Visibility Impairment Analysis, March 2006, 
4

Baseline NOx emission rates were derived from the highest daily rates for 2001-2003 as found in 

the CAMD emissions system, with some outlier values eliminated for Naughton Unit 3.

Table 1- Description of EPA control scenarios for Wyoming’s BART sources

EPA Scenario Description

New Baseline Post-Control Scenario A from state‘s BART Application Analysis with NOx emission 

rate reflecting 24-hour average actual emission rate from the highest emitting day 

of the meteorological period modeled.

Scenario 1 Post-Control Scenario A from state’s BART Application Analysis with NOx emission 

rate that reflects the percent reduction from LNB/OFA controls.

Scenario 2 Post-Control Scenario A from state’s BART Application Analysis with NOx emission 

rate that reflects percent reduction from LNB/OFA and SNCR controls.

Scenario 3 Post-Control Scenario A from state’s BART Application Analysis with NOx emission 

rate that reflects the percent reduction from LNB/OFA and SCR controls.

EPA also performed additional modeling for Dave Johnston’s Units 1 and 2 (see Table 16

and Table 17). These are considered reasonable progress sources and were not part of the state’s 

BART Application Analyses. EPA followed a similar approach for modeling these sources as 

used for the BART sources. Stack parameter data for these sources were obtained from the 

Western Region Air Partnership’s (WRAP) 2002 SMOKE input files. Table 2 summarizes the 

control scenarios for EPA’s reasonable progress source modeling.

Table 18 through Table 22 present the results of the additional visibility modeling for all 

units at each subject facility. Using the updated CALPUFF output, the 98th percentile or 8th

maximum 24-hour visibility impact (deciview [Δdv]) was determined at all Class I areas within 

300 kilometers of the subject facility for each year between 2001 and 2003. These tables also 

present the visibility improvements for EPA Scenario 1, Scenario 2, and Scenario 3, which were

determined by the difference between the new baseline and EPA scenarios. 
5

Table 2 – Description of EPA control scenarios for Reasonable Progress sources (Dave 

Johnston Units 1 and 2)

EPA Scenario Description

New Baseline NOx emission rate reflects 24-hour average actual emission rate from the highest 

emitting day of the meteorological period modeled. All other emission inputs 

obtained from facility’s Title V Operating Permit limits.

Scenario 1 Same inputs as New Baseline, but with a NOx emission rate that reflects percent 

reduction from LNB/OFA controls

Scenario 2 Same inputs as New Baseline, but with a NOx emission rate that reflects percent 

reduction from LNB/OFA and SNCR controls

Scenario 3 Same inputs as New Baseline, but with a NOx emission rate that reflects percent 

reduction from LNB/OFA and SCR controls

Table 3 – Modeling Inputs for Pacificorp - Dave Johnston Unit 3

CALPUFF Inputs New Baseline Scenario 1 Scenario 2 Scenario 3

SO2 (lb/hr) 420 420 420 420

Total Sulfate (SO4)(lb/hr) 2.5 2.5 2.5 5.1

NOx (lb/hr) 1671.0 706.3 529.7 163.3

HNO3 0 0 0 0

NO3 0 0 0 0

PM10-2.5 (coarse PM)(lb/hr) 23.9 23.9 23.9 23.9

PM2.5 (lb/hr) 18.1 18.1 18.1 18.1

Stack Height (meters) 152.4 152.4 152.4 152.4

Base Elevation (meters) 1509 1509 1509 1509

Stack Diameter (meters) 4.57 4.57 4.57 4.57

Exit Velocity (meters/second) 25.5 25.5 25.5 25.5

Exit Temperature (Kelvin) 348 348 348 348
6

Table 4 – Modeling Inputs for Pacificorp - Dave Johnston Unit 4

CALPUFF Inputs New Baseline Scenario 1 Scenario 2 Scenario 3

SO2 (lb/hr) 615 615 615 615

Total Sulfate (SO4)(lb/hr) 3.7 3.7 3.7 7.4

NOx (lb/hr) 1983.0 765.1 612.1 270.8

HNO3 0 0 0 0

NO3 0 0 0 0

PM10-2.5 (coarse PM)(lb/hr) 35.1 35.1 35.1 35.1

PM2.5 (lb/hr) 26.4 26.4 26.4 26.4

Stack Height (meters) 152 152 152 152

Base Elevation (meters) 1509 1509 1509 1509

Stack Diameter (meters) 5.79 5.79 5.79 5.79

Exit Velocity (meters/second) 25.7 25.7 25.7 25.7

Exit Temperature (Kelvin) 350 350 350 350

Table 5 – Modeling Inputs for Pacificorp - Naughton Unit 1

CALPUFF Inputs New Baseline Scenario 1 Scenario 2 Scenario 3

SO2 (lb/hr) 278 278 278 278

Total Sulfate (SO4)(lb/hr) 16.7 16.7 16.7 33.3

NOx (lb/hr) 1322.0 540.7 405.5 128.2

HNO3 0 0 0 0

NO3 0 0 0 0

PM10-2.5 (coarse PM)(lb/hr) 33.4 33.4 33.4 33.4

PM2.5 (lb/hr) 44.3 44.3 44.3 44.3

Stack Height (meters) 145 145 145 145

Base Elevation (meters) 2115 2115 2115 2115

Stack Diameter (meters) 4.88 4.88 4.88 4.88

Exit Velocity (meters/second) 18.1 18.1 18.1 18.1

Exit Temperature (Kelvin) 323 323 323 323
7

Table 6 – Modeling Inputs for Pacificorp - Naughton Unit 2

CALPUFF Inputs New Baseline Scenario 1 Scenario 2 Scenario 3

SO2 (lb/hr) 360 360 360 360

Total Sulfate (SO4)(lb/hr) 21.6 21.6 21.6 43.2

NOx (lb/hr) 1636.0 660.7 495.5 156.7

HNO3 0 0 0 0

NO3 0 0 0 0

PM10-2.5 (coarse PM)(lb/hr) 55.7 55.7 55.7 55.7

PM2.5 (lb/hr) 73.9 73.9 73.9 73.9

Stack Height (meters) 145 145 145 145

Base Elevation (meters) 2115 2115 2115 2115

Stack Diameter (meters) 5.49 5.49 5.49 5.49

Exit Velocity (meters/second) 18.5 18.5 18.5 18.5

Exit Temperature (Kelvin) 323 323 323 323

Table 7 – Modeling Inputs for Pacificorp - Naughton Unit 3

CALPUFF Inputs New Baseline Scenario 1 Scenario 2 Scenario 3

SO2 (lb/hr) 814 814 814 814

Total Sulfate (SO4)(lb/hr) 33.3 33.3 33.3 66.6

NOx (lb/hr) 2368.0 2137.4 1496.2 323.9

HNO3 0 0 0 0

NO3 0 0 0 0

PM10-2.5 (coarse PM)(lb/hr) 23.9 23.9 23.9 23.9

PM2.5 (lb/hr) 31.6 31.6 31.6 31.6

Stack Height (meters) 145 145 145 145

Base Elevation (meters) 2113 2113 2113 2113

Stack Diameter (meters) 8.08 8.08 8.08 8.08

Exit Velocity (meters/second) 20.2 20.2 20.2 20.2

Exit Temperature (Kelvin) 322 322 322 322
8

Table 8 – Modeling Inputs for Pacificorp – Wyodak

CALPUFF Inputs New Baseline Scenario 1 Scenario 2 Scenario 3

SO2 (lb/hr) 759 759 759 759

Total Sulfate (SO4)(lb/hr) 5.5 5.5 5.5 11.6

NOx (lb/hr) 1397.0 1022.0 817.6 266.4

HNO3 0 0 0 0

NO3 0 0 0 0

PM10-2.5 (coarse PM)(lb/hr) 70.5 70.5 70.5 70.5

PM2.5 (lb/hr) 40.2 40.2 40.2 40.2

Stack Height (meters) 122 122 122 122

Base Elevation (meters) 1347 1347 1347 1347

Stack Diameter (meters) 6.1 6.1 6.1 6.1

Exit Velocity (meters/second) 23.5 23.5 23.5 23.5

Exit Temperature (Kelvin) 350 350 350 350

Table 9 – Modeling Inputs for Basin Electric – Laramie River Station Unit 1

CALPUFF Inputs New Baseline Scenario 1 Scenario 2 Scenario 3

SO2 (tpy) 3745 3745 3745 3745

Total Sulfate (SO4)(tpy) 3.06 3.18 3.18 3.18

NOx (tpy) 9557.16 7099.1 5679.1 1848.8

HNO3 0 0 0 0

NO3 0 0 0 0

PM10-2.5 (coarse PM)(tpy) 0 0 0 0

PM2.5 (tpy) 702 702 702 702

Stack Height (meters) 184.404 184.404 184.404 184.404

Base Elevation (meters) 1348 1348 1348 1348

Stack Diameter (meters) 8.6868 8.6868 8.6868 8.6868

Exit Velocity (meters/second) 21.336 21.336 21.336 21.336

Exit Temperature (Kelvin) 338.7056 338.7056 338.7056 338.7056
9

Table 10 – Modeling Inputs for Basin Electric – Laramie River Station Unit 2

CALPUFF Inputs New Baseline Scenario 1 Scenario 2 Scenario 3

SO2 (tpy) 3725 3725 3725 3725

Total Sulfate (SO4)(tpy) 2.8 3.25 3.25 3.25

NOx (tpy) 8786.3 6240.6 4992.8 1625.0

HNO3 0 0 0 0

NO3 0 0 0 0

PM10-2.5 (coarse PM)(tpy) 0 0 0 0

PM2.5 (tpy) 698 698 698 698

Stack Height (meters) 184.404 184.404 184.404 184.404

Base Elevation (meters) 1348 1348 1348 1348

Stack Diameter (meters) 8.6868 8.6868 8.6868 8.6868

Exit Velocity (meters/second) 21.03 21.03 21.03 21.03

Exit Temperature (Kelvin) 338.7056 338.7056 338.7056 338.7056

Table 11 – Modeling Inputs for Basin Electric – Laramie River Station Unit 3

CALPUFF Inputs New Baseline Scenario 1 Scenario 2 Scenario 3

SO2 (tpy) 4060 4060 4060 4060

Total Sulfate (SO4)(tpy) 0.22 0.22 0.22 0.22

NOx (tpy) 8834.5 6354.9 5083.9 1654.8

HNO3 0 0 0 0

NO3 0 0 0 0

PM10-2.5 (coarse PM)(tpy) 0 0 0 0

PM2.5 (tpy) 716 716 716 716

Stack Height (meters) 184.404 184.404 184.404 184.404

Base Elevation (meters) 1348 1348 1348 1348

Stack Diameter (meters) 8.6868 8.6868 8.6868 8.6868

Exit Velocity (meters/second) 22.25 22.25 22.25 22.25

Exit Temperature (Kelvin) 352.0 352.0 352.0 352.0
10

Table 12 – Modeling Inputs for Pacificorp – Jim Bridger Unit 1

CALPUFF Inputs New Baseline Scenario 1 Scenario 2 Scenario 3

SO2 (lb/hr) 900 900 900 900

Total Sulfate (SO4)(lb/hr) 54.1 54.1 54.1 54.1

NOx (lb/hr) 2788.1 1279.8 1023.9 355.5

HNO3 0 0 0 0

NO3 0 0 0 0

PM10-2.5 (coarse PM)(lb/hr) 77.4 77.4 77.4 77.4

PM2.5 (lb/hr) 102.6 102.6 102.6 102.6

Stack Height (meters) 152 152 152 152

Base Elevation (meters) 2036 2036 2036 2036

Stack Diameter (meters) 7.32 7.32 7.32 7.32

Exit Velocity (meters/second) 24.7 24.7 24.7 24.7

Exit Temperature (Kelvin) 328 328 328 328

Table 13 – Modeling Inputs for Pacificorp – Jim Bridger Unit 2

CALPUFF Inputs New Baseline Scenario 1 Scenario 2 Scenario 3

SO2 (lb/hr) 900 900 900 900

Total Sulfate (SO4)(lb/hr) 54.1 54.1 54.1 54.1

NOx (lb/hr) 2772.3 1386.5 1109.2 374.1

HNO3 0 0 0 0

NO3 0 0 0 0

PM10-2.5 (coarse PM)(lb/hr) 77.4 77.4 77.4 77.4

PM2.5 (lb/hr) 102.6 102.6 102.6 102.6

Stack Height (meters) 152 152 152 152

Base Elevation (meters) 2036 2036 2036 2036

Stack Diameter (meters) 7.32 7.32 7.32 7.32

Exit Velocity (meters/second) 24.7 24.7 24.7 24.7

Exit Temperature (Kelvin) 328 328 328 328
11

Table 14 – Modeling Inputs for Pacificorp – Jim Bridger Unit 3

CALPUFF Inputs New Baseline Scenario 1 Scenario 2 Scenario 3

SO2 (lb/hr) 900 900 900 900

Total Sulfate (SO4)(lb/hr) 54.1 54.1 54.1 54.1

NOx (lb/hr) 2670.1 1408.5 1126.8 358.4

HNO3 0 0 0 0

NO3 0 0 0 0

PM10-2.5 (coarse PM)(lb/hr) 77.4 77.4 77.4 77.4

PM2.5 (lb/hr) 102.6 102.6 102.6 102.6

Stack Height (meters) 152 152 152 152

Base Elevation (meters) 2036 2036 2036 2036

Stack Diameter (meters) 7.32 7.32 7.32 7.32

Exit Velocity (meters/second) 24.7 24.7 24.7 24.7

Exit Temperature (Kelvin) 328 328 328 328

Table 15 – Modeling Inputs for Pacificorp – Jim Bridger Unit 4

CALPUFF Inputs New Baseline Scenario 1 Scenario 2 Scenario 3

SO2 (lb/hr) 900 900 900 900

Total Sulfate (SO4)(lb/hr) 54.1 54.1 54.1 54.1

NOx (lb/hr) 2968.9 1449.9 1159.9 374.5

HNO3 0 0 0 0

NO3 0 0 0 0

PM10-2.5 (coarse PM)(lb/hr) 77.4 77.4 77.4 77.4

PM2.5 (lb/hr) 102.6 102.6 102.6 102.6

Stack Height (meters) 152 152 152 152

Base Elevation (meters) 2033 2033 2033 2033

Stack Diameter (meters) 9.45 9.45 9.45 9.45

Exit Velocity (meters/second) 12.9 12.9 12.9 12.9

Exit Temperature (Kelvin) 322 322 322 322
12

Reasonable Progress Sources 

Table 16 – Modeling Inputs for Pacificorp - Dave Johnston Unit 1

CALPUFF Inputs New Baseline Scenario 1 Scenario 2 Scenario 3

SO2 (lb/hr) 1620 1620 1620 0

Total Sulfate (SO4)(lb/hr) 1 1 1 2

NOx (lb/hr) 679.6 298.8 224.1 74.7

HNO3 0 0 0 0

NO3 0 0 0 0

PM10-2.5 (coarse PM)(lb/hr) 149.726 149.726 149.726 149.726

PM2.5 (lb/hr) 198.474 198.474 198.474 198.474

Stack Height (meters) 152.4 152.4 152.4 152.4

Base Elevation (meters) 1509 1509 1509 1509

Stack Diameter (meters) 3.35 3.35 3.35 3.35

Exit Velocity (meters/second) 28.35 28.35 28.35 28.35

Exit Temperature (Kelvin) 418.15 418.15 418.15 418.15

Table 17 – Modeling Inputs for Pacificorp - Dave Johnston Unit 2

CALPUFF Inputs New Baseline Scenario 1 Scenario 2 Scenario 3

SO2 (lb/hr) 1620 1620 1620 1620

Total Sulfate (SO4)(lb/hr) 1 1 1 2

NOx (lb/hr) 653.7 296.7 222.5 74.2

HNO3 0 0 0 0

NO3 0 0 0 0

PM10-2.5 (coarse PM)(lb/hr) 149.726 149.726 149.726 149.726

PM2.5 (lb/hr) 198.474 198.474 198.474 198.474

Stack Height (meters) 152.4 152.4 152.4 152.4

Base Elevation (meters) 1509 1509 1509 1509

Stack Diameter (meters) 3.35 3.35 3.35 3.35

Exit Velocity (meters/second) 28.69 28.69 28.69 28.69

Exit Temperature (Kelvin) 425.93 425.93 425.93 425.93
13

Table 18 – Model Results for PacifiCorp – Dave Johnston Units

Unit Class I Area

by Year

New Baseline Scenario 1 Scenario 2 Scenario 3

98th Percentile

Visibility Impact

(∆dv)

98th Percentile

Visibility Impact 

(∆dv)

Visibility Improvement 

(∆dv)

98th Percentile

Visibility Impact 

(∆dv)

Visibility Improvement 

(∆dv)

98th Percentile

Visibility Impact 

(∆dv)

Visibility Improvement 

(∆dv)

Unit 1

Badlands 2001 0.824 0.659 0.165 0.631 0.193 0.578 0.246

Badlands 2002 0.585 0.490 0.095 0.462 0.123 0.419 0.166

Badlands 2003 0.773 0.659 0.114 0.618 0.155 0.539 0.234

Wind Cave 2001 0.921 0.717 0.204 0.683 0.238 0.622 0.299

Wind Cave 2002 0.879 0.769 0.110 0.741 0.138 0.686 0.193

Wind Cave 2003 1.226 0.918 0.308 0.874 0.352 0.787 0.439

Unit 2

Badlands 2001 0.802 0.658 0.144 0.631 0.171 0.577 0.225

Badlands 2002 0.590 0.487 0.103 0.460 0.130 0.422 0.168

Badlands 2003 0.774 0.659 0.115 0.617 0.157 0.538 0.236

Wind Cave 2001 0.904 0.701 0.203 0.676 0.228 0.630 0.274

Wind Cave 2002 0.875 0.763 0.112 0.736 0.139 0.683 0.192

Wind Cave 2003 1.206 0.918 0.288 0.873 0.333 0.788 0.418

Unit 3

Badlands 2001 0.800 0.417 0.383 0.350 0.450 0.211 0.589

Badlands 2002 0.641 0.310 0.331 0.250 0.391 0.152 0.489

Badlands 2003 0.882 0.440 0.442 0.359 0.523 0.208 0.674

Wind Cave 2001 1.03 0.529 0.500 0.435 0.594 0.238 0.791

Wind Cave 2002 0.84 0.448 0.395 0.370 0.473 0.230 0.613

Wind Cave 2003 1.32 0.683 0.639 0.564 0.758 0.318 1.004

Mt Zirkel 2001 0.216 0.115 0.101 0.093 0.123 0.061 0.155

Mt Zirkel 2002 0.353 0.177 0.176 0.148 0.205 0.096 0.257

Mt Zirkel 2003 0.439 0.228 0.211 0.190 0.249 0.105 0.334

Rawah 2001 0.264 0.147 0.117 0.122 0.142 0.07 0.191

Rawah 2002 0.486 0.262 0.224 0.222 0.264 0.14 0.349

Rawah 2003 0.484 0.241 0.243 0.197 0.287 0.11 0.375

RMNP 2001 0.311 0.166 0.145 0.139 0.172 0.09 0.224

RMNP 2002 0.475 0.230 0.245 0.189 0.286 0.09 0.381

RMNP 2003 0.688 0.346 0.342 0.281 0.407 0.15 0.539

Unit 4 Badlands 2001 0.995 0.456 0.539 0.456 0.539 0.320 0.675
14

Unit Class I Area

by Year

New Baseline Scenario 1 Scenario 2 Scenario 3

98th Percentile

Visibility Impact

(∆dv)

98th Percentile

Visibility Impact 

(∆dv)

Visibility Improvement 

(∆dv)

98th Percentile

Visibility Impact 

(∆dv)

Visibility Improvement 

(∆dv)

98th Percentile

Visibility Impact 

(∆dv)

Visibility Improvement 

(∆dv)

Badlands 2002 0.762 0.365 0.397 0.332 0.430 0.222 0.540

Badlands 2003 1.049 0.556 0.493 0.479 0.570 0.322 0.727

Mt Zirkel 2001 0.242 0.124 0.118 0.123 0.119 0.122 0.120

Mt Zirkel 2002 0.424 0.216 0.208 0.189 0.235 0.165 0.259

Mt Zirkel 2003 0.557 0.279 0.278 0.238 0.319 0.192 0.365

Rawah 2001 0.332 0.163 0.169 0.139 0.193 0.100 0.232

Rawah 2002 0.586 0.316 0.270 0.282 0.304 0.208 0.378

Rawah 2003 0.557 0.270 0.287 0.235 0.322 0.169 0.388

RMNP 2001 0.373 0.186 0.187 0.166 0.207 0.122 0.251

RMNP 2002 0.515 0.264 0.251 0.236 0.279 0.149 0.366

RMNP 2003 0.869 0.421 0.448 0.364 0.505 0.239 0.630

Table 19 – Model Results for PacifiCorp – Naughton Units

Unit Class I Area

by Year

New Baseline Scenario 1 Scenario 2 Scenario 3

98th Percentile

Visibility Impact 

(∆dv)

98th Percentile

Visibility Impact 

(∆dv)

Visibility Improvement 

(∆dv)

98th Percentile

Visibility Impact 

(∆dv)

Visibility Improvement 

(∆dv)

98th Percentile

Visibility Impact 

(∆dv)

Visibility Improvement 

(∆dv)

Unit 1

Bridger 2001 1.634 0.799 0.835 0.649 0.985 0.404 1.230

Bridger 2002 1.350 0.675 0.675 0.557 0.793 0.368 0.982

Bridger 2003 1.490 0.756 0.734 0.624 0.866 0.411 1.079

Fitzpatrick 2001 0.732 0.349 0.383 0.283 0.449 0.174 0.558

Fitzpatrick 2002 0.481 0.239 0.242 0.198 0.283 0.131 0.350

Fitzpatrick 2003 0.609 0.304 0.305 0.248 0.361 0.155 0.454

N. Absaroka 2001 0.266 0.129 0.137 0.109 0.157 0.073 0.193

N. Absaroka 2002 0.279 0.141 0.138 0.120 0.159 0.083 0.196

N. Absaroka 2003 0.158 0.079 0.079 0.068 0.090 0.048 0.110

Washakie 2001 0.327 0.166 0.161 0.138 0.189 0.090 0.237

Washakie 2002 0.402 0.205 0.197 0.172 0.230 0.112 0.290

Washakie 2003 0.291 0.145 0.146 0.119 0.172 0.083 0.208

Teton 2001 0.408 0.208 0.200 0.168 0.240 0.113 0.295
15

Unit Class I Area

by Year

New Baseline Scenario 1 Scenario 2 Scenario 3

98th Percentile

Visibility Impact 

(∆dv)

98th Percentile

Visibility Impact 

(∆dv)

Visibility Improvement 

(∆dv)

98th Percentile

Visibility Impact 

(∆dv)

Visibility Improvement 

(∆dv)

98th Percentile

Visibility Impact 

(∆dv)

Visibility Improvement 

(∆dv)

Teton 2002 0.477 0.229 0.248 0.186 0.291 0.121 0.356

Teton 2003 0.331 0.160 0.171 0.132 0.199 0.088 0.243

Grand Teton 2001 0.480 0.230 0.250 0.188 0.292 0.124 0.356

Grand Teton 2002 0.665 0.332 0.333 0.274 0.391 0.177 0.488

Grand Teton 2003 0.331 0.161 0.170 0.131 0.200 0.098 0.233

Yellowstone 2001 0.392 0.198 0.194 0.165 0.227 0.108 0.284

Yellowstone 2002 0.544 0.267 0.277 0.219 0.325 0.137 0.407

Yellowstone 2003 0.339 0.165 0.174 0.136 0.203 0.089 0.250

Unit 2

Bridger 2001 1.952 0.983 0.969 0.804 1.148 0.531 1.421

Bridger 2002 1.575 0.787 0.788 0.653 0.922 0.441 1.134

Bridger 2003 1.859 0.956 0.903 0.796 1.063 0.543 1.316

Fitzpatrick 2001 0.853 0.422 0.431 0.344 0.509 0.216 0.637

Fitzpatrick 2002 0.619 0.299 0.320 0.249 0.370 0.163 0.456

Fitzpatrick 2003 0.709 0.340 0.369 0.276 0.433 0.181 0.528

N. Absaroka 2001 0.347 0.167 0.180 0.137 0.210 0.092 0.255

N. Absaroka 2002 0.344 0.185 0.159 0.158 0.186 0.112 0.232

N. Absaroka 2003 0.193 0.097 0.096 0.082 0.111 0.062 0.131

Washakie 2001 0.427 0.217 0.210 0.175 0.252 0.124 0.303

Washakie 2002 0.484 0.247 0.237 0.208 0.276 0.141 0.343

Washakie 2003 0.350 0.174 0.176 0.145 0.205 0.101 0.249

Teton 2001 0.511 0.261 0.250 0.215 0.296 0.146 0.365

Teton 2002 0.609 0.294 0.315 0.241 0.368 0.161 0.448

Teton 2003 0.406 0.202 0.204 0.169 0.237 0.108 0.298

Grand Teton 2001 0.603 0.295 0.308 0.243 0.360 0.156 0.447

Grand Teton 2002 0.932 0.458 0.474 0.375 0.557 0.234 0.698

Grand Teton 2003 0.421 0.208 0.213 0.171 0.250 0.121 0.300

Yellowstone 2001 0.518 0.262 0.256 0.219 0.299 0.146 0.372

Yellowstone 2002 0.536 0.285 0.251 0.244 0.292 0.176 0.360

Yellowstone 2003 0.354 0.172 0.182 0.142 0.212 0.095 0.259

Unit 3 Bridger 2001 2.222 2.051 0.171 1.559 0.663 0.761 1.461
16

Unit Class I Area

by Year

New Baseline Scenario 1 Scenario 2 Scenario 3

98th Percentile

Visibility Impact 

(∆dv)

98th Percentile

Visibility Impact 

(∆dv)

Visibility Improvement 

(∆dv)

98th Percentile

Visibility Impact 

(∆dv)

Visibility Improvement 

(∆dv)

98th Percentile

Visibility Impact 

(∆dv)

Visibility Improvement 

(∆dv)

Bridger 2002 1.838 1.695 0.143 1.291 0.547 0.694 1.144

Bridger 2003 2.391 2.220 0.171 1.693 0.698 0.878 1.513

Fitzpatrick 2001 1.144 1.057 0.087 0.816 0.328 0.400 0.744

Fitzpatrick 2002 0.896 0.822 0.074 0.623 0.273 0.305 0.591

Fitzpatrick 2003 0.881 0.810 0.071 0.612 0.269 0.279 0.602

N. Absaroka 2001 0.542 0.499 0.043 0.380 0.162 0.188 0.354

N. Absaroka 2002 0.583 0.541 0.042 0.423 0.160 0.221 0.362

N. Absaroka 2003 0.288 0.266 0.022 0.205 0.083 0.115 0.173

Washakie 2001 0.808 0.746 0.062 0.575 0.233 0.291 0.517

Washakie 2002 0.775 0.712 0.063 0.542 0.233 0.267 0.508

Washakie 2003 0.589 0.541 0.048 0.405 0.184 0.197 0.392

Teton 2001 0.858 0.789 0.069 0.603 0.255 0.304 0.554

Teton 2002 0.962 0.884 0.078 0.665 0.297 0.307 0.655

Teton 2003 0.609 0.560 0.049 0.426 0.183 0.206 0.403

Grand Teton 2001 1.009 0.932 0.077 0.723 0.286 0.362 0.647

Grand Teton 2002 1.090 1.003 0.087 0.757 0.333 0.360 0.730

Grand Teton 2003 0.800 0.734 0.066 0.547 0.253 0.266 0.534

Yellowstone 2001 0.834 0.768 0.066 0.583 0.251 0.282 0.552

Yellowstone 2002 0.860 0.791 0.069 0.600 0.260 0.292 0.568

Yellowstone 2003 0.451 0.416 0.035 0.319 0.132 0.154 0.297

Table 20 – Model Results for PacifiCorp – Wyodak Unit

Unit Class I Area

by Year

New Baseline Scenario 1 Scenario 2 Scenario 3

98th Percentile

Visibility Impact 

(∆dv)

98th Percentile

Visibility Impact 

(∆dv)

Visibility Improvement 

(∆dv)

98th Percentile

Visibility Impact 

(∆dv)

Visibility Improvement 

(∆dv)

98th Percentile

Visibility Impact 

(∆dv)

Visibility Improvement 

(∆dv)

Unit 1

Badlands 2001 0.579 0.455 0.124 0.389 0.190 0.243 0.336

Badlands 2002 0.746 0.613 0.133 0.539 0.207 0.299 0.447

Badlands 2003 0.706 0.536 0.170 0.479 0.227 0.285 0.421

Wind Cave 2001 0.840 0.648 0.192 0.558 0.282 0.322 0.518
17

Unit Class I Area

by Year

New Baseline Scenario 1 Scenario 2 Scenario 3

98th Percentile

Visibility Impact 

(∆dv)

98th Percentile

Visibility Impact 

(∆dv)

Visibility Improvement 

(∆dv)

98th Percentile

Visibility Impact 

(∆dv)

Visibility Improvement 

(∆dv)

98th Percentile

Visibility Impact 

(∆dv)

Visibility Improvement 

(∆dv)

Wind Cave 2002 0.958 0.751 0.207 0.637 0.321 0.365 0.593

Wind Cave 2003 1.138 0.896 0.242 0.762 0.376 0.431 0.707
18

Table 21 – Model Results for Basin Electric – Laramie River Station Units

Unit Class I Area

by Year

New Baseline Scenario 1 Scenario 2 Scenario 3

98th Percentile

Visibility Impact 

(∆dv)

98th Percentile

Visibility Impact 

(∆dv)

Visibility Improvement 

(∆dv)

98th Percentile

Visibility Impact 

(∆dv)

Visibility Improvement 

(∆dv)

98th Percentile

Visibility Impact 

(∆dv)

Visibility Improvement 

(∆dv)

Unit 1

Badlands 2001 1.278 0.993 0.285 0.840 0.438 0.489 0.789

Badlands 2002 0.738 0.582 0.156 0.504 0.234 0.297 0.441

Badlands 2003 1.051 0.820 0.231 0.684 0.367 0.327 0.724

Wind Cave 2001 1.038 0.838 0.200 0.721 0.317 0.399 0.639

Wind Cave 2002 1.077 0.888 0.189 0.778 0.299 0.486 0.591

Wind Cave 2003 0.788 0.618 0.170 0.531 0.257 0.331 0.457

Rawah 2001 0.322 0.269 0.053 0.231 0.091 0.125 0.197

Rawah 2002 0.555 0.454 0.101 0.395 0.160 0.239 0.316

Rawah 2003 0.351 0.300 0.051 0.270 0.081 0.163 0.188

RMNP 2001 0.408 0.318 0.090 0.267 0.141 0.154 0.254

RMNP 2002 0.603 0.481 0.122 0.416 0.187 0.262 0.341

RMNP 2003 0.590 0.472 0.118 0.404 0.186 0.219 0.371

Unit 2

Badlands 2001 1.194 0.895 0.299 0.776 0.418 0.461 0.733

Badlands 2002 0.685 0.532 0.153 0.464 0.221 0.284 0.401

Badlands 2003 0.974 0.734 0.240 0.614 0.360 0.312 0.662

Wind Cave 2001 0.978 0.769 0.209 0.666 0.312 0.377 0.601

Wind Cave 2002 1.031 0.831 0.200 0.734 0.297 0.475 0.556

Wind Cave 2003 0.739 0.562 0.177 0.498 0.241 0.321 0.418

Rawah 2001 0.307 0.248 0.059 0.213 0.094 0.119 0.188

Rawah 2002 0.521 0.417 0.104 0.366 0.155 0.229 0.292

Rawah 2003 0.327 0.275 0.052 0.250 0.077 0.154 0.173

RMNP 2001 0.379 0.287 0.092 0.242 0.137 0.147 0.232

RMNP 2002 0.580 0.450 0.130 0.386 0.194 0.251 0.329

RMNP 2003 0.551 0.429 0.122 0.370 0.181 0.203 0.348

Unit 3

Badlands 2001 1.141 0.923 0.218 0.810 0.331 0.472 0.669

Badlands 2002 0.733 0.577 0.156 0.493 0.240 0.299 0.434

Badlands 2003 0.896 0.696 0.200 0.593 0.303 0.309 0.587

Wind Cave 2001 0.988 0.787 0.201 0.683 0.305 0.389 0.599
19

Unit Class I Area

by Year

New Baseline Scenario 1 Scenario 2 Scenario 3

98th Percentile

Visibility Impact 

(∆dv)

98th Percentile

Visibility Impact 

(∆dv)

Visibility Improvement 

(∆dv)

98th Percentile

Visibility Impact 

(∆dv)

Visibility Improvement 

(∆dv)

98th Percentile

Visibility Impact 

(∆dv)

Visibility Improvement 

(∆dv)

Wind Cave 2002 0.993 0.800 0.193 0.702 0.291 0.461 0.532

Wind Cave 2003 0.728 0.583 0.145 0.496 0.232 0.336 0.392

Rawah 2001 0.314 0.258 0.056 0.227 0.087 0.144 0.170

Rawah 2002 0.533 0.432 0.101 0.380 0.153 0.241 0.292

Rawah 2003 0.348 0.296 0.052 0.269 0.079 0.166 0.182

RMNP 2001 0.392 0.301 0.091 0.255 0.137 0.162 0.230

RMNP 2002 0.584 0.473 0.111 0.417 0.167 0.276 0.308

RMNP 2003 0.555 0.438 0.117 0.379 0.176 0.220 0.335

Table 22 – Model Results for PacifiCorp – Jim Bridger Units

Unit Class I Area

by Year

New Baseline Scenario 1 Scenario 2 Scenario 3

98th Percentile

Visibility Impact 

(∆dv)

98th Percentile

Visibility Impact 

(∆dv)

Visibility Improvement 

(∆dv)

98th Percentile

Visibility Impact 

(∆dv)

Visibility Improvement 

(∆dv)

98th Percentile

Visibility Impact 

(∆dv)

Visibility Improvement 

(∆dv)

Unit 1

Bridger 2001 0.692 0.387 0.305 0.337 0.355 0.252 0.440

Bridger 2002 1.353 0.826 0.527 0.734 0.619 0.445 0.908

Bridger 2003 0.721 0.408 0.313 0.355 0.366 0.233 0.488

Fitzpatrick 2001 0.382 0.227 0.155 0.201 0.181 0.132 0.250

Fitzpatrick 2002 0.599 0.375 0.224 0.337 0.262 0.239 0.360

Fitzpatrick 2003 0.338 0.196 0.142 0.173 0.165 0.113 0.225

Mt. Zirkel 2001 1.077 0.628 0.449 0.552 0.525 0.353 0.724

Mt. Zirkel 2002 1.397 0.805 0.592 0.703 0.694 0.433 0.964

Mt. Zirkel 2003 1.204 0.650 0.554 0.553 0.651 0.331 0.873

Rawah 2001 0.807 0.445 0.362 0.383 0.424 0.238 0.569

Rawah 2002 0.944 0.517 0.427 0.467 0.477 0.336 0.608

Rawah 2003 1.081 0.585 0.496 0.501 0.580 0.292 0.789

RMNP 2001 0.571 0.337 0.234 0.300 0.271 0.180 0.391

RMNP 2002 0.993 0.582 0.411 0.505 0.488 0.306 0.687

RMNP 2003 0.937 0.530 0.407 0.460 0.477 0.290 0.647
20

Unit Class I Area

by Year

New Baseline Scenario 1 Scenario 2 Scenario 3

98th Percentile

Visibility Impact 

(∆dv)

98th Percentile

Visibility Impact 

(∆dv)

Visibility Improvement 

(∆dv)

98th Percentile

Visibility Impact 

(∆dv)

Visibility Improvement 

(∆dv)

98th Percentile

Visibility Impact 

(∆dv)

Visibility Improvement 

(∆dv)

Grand Teton 2001 0.273 0.163 0.110 0.147 0.126 0.092 0.181

Grand Teton 2002 0.312 0.174 0.138 0.160 0.152 0.152 0.160

Grand Teton 2003 0.389 0.223 0.166 0.195 0.194 0.124 0.265

Teton 2001 0.263 0.156 0.107 0.140 0.123 0.098 0.165

Teton 2002 0.403 0.245 0.158 0.218 0.185 0.147 0.256

Teton 2003 0.369 0.208 0.161 0.180 0.189 0.118 0.251

Washakie 2001 0.383 0.215 0.168 0.187 0.196 0.126 0.257

Washakie 2002 0.422 0.239 0.183 0.209 0.213 0.153 0.269

Washakie 2003 0.240 0.145 0.095 0.132 0.108 0.104 0.136

Yellowstone 2001 0.201 0.121 0.080 0.109 0.092 0.082 0.119

Yellowstone 2002 0.407 0.254 0.153 0.228 0.179 0.145 0.262

Yellowstone 2003 0.357 0.199 0.158 0.172 0.185 0.100 0.257

Unit 2

Bridger 2001 0.689 0.407 0.282 0.353 0.336 0.257 0.432

Bridger 2002 1.347 0.869 0.478 0.765 0.582 0.453 0.894

Bridger 2003 0.718 0.430 0.288 0.372 0.346 0.236 0.482

Fitzpatrick 2001 0.380 0.238 0.142 0.210 0.170 0.134 0.246

Fitzpatrick 2002 0.596 0.391 0.205 0.350 0.246 0.241 0.355

Fitzpatrick 2003 0.337 0.206 0.131 0.180 0.157 0.115 0.222

Mt. Zirkel 2001 1.072 0.660 0.412 0.577 0.495 0.358 0.714

Mt. Zirkel 2002 1.391 0.842 0.549 0.737 0.654 0.440 0.951

Mt. Zirkel 2003 1.198 0.690 0.508 0.586 0.612 0.337 0.861

Rawah 2001 0.803 0.471 0.332 0.404 0.399 0.241 0.562

Rawah 2002 0.940 0.548 0.392 0.483 0.457 0.340 0.600

Rawah 2003 1.076 0.621 0.455 0.529 0.547 0.296 0.780

RMNP 2001 0.568 0.350 0.218 0.317 0.251 0.183 0.385

RMNP 2002 0.989 0.612 0.377 0.531 0.458 0.311 0.678

RMNP 2003 0.933 0.559 0.374 0.483 0.450 0.293 0.640

Grand Teton 2001 0.272 0.170 0.102 0.152 0.120 0.094 0.178

Grand Teton 2002 0.311 0.184 0.127 0.161 0.150 0.152 0.159

Grand Teton 2003 0.387 0.235 0.152 0.204 0.183 0.126 0.261
21

Unit Class I Area

by Year

New Baseline Scenario 1 Scenario 2 Scenario 3

98th Percentile

Visibility Impact 

(∆dv)

98th Percentile

Visibility Impact 

(∆dv)

Visibility Improvement 

(∆dv)

98th Percentile

Visibility Impact 

(∆dv)

Visibility Improvement 

(∆dv)

98th Percentile

Visibility Impact 

(∆dv)

Visibility Improvement 

(∆dv)

Teton 2001 0.262 0.162 0.100 0.145 0.117 0.099 0.163

Teton 2002 0.401 0.256 0.145 0.227 0.174 0.149 0.252

Teton 2003 0.367 0.219 0.148 0.189 0.178 0.120 0.247

Washakie 2001 0.381 0.226 0.155 0.196 0.185 0.127 0.254

Washakie 2002 0.420 0.252 0.168 0.219 0.201 0.154 0.266

Washakie 2003 0.239 0.150 0.089 0.136 0.103 0.106 0.133

Yellowstone 2001 0.200 0.125 0.075 0.113 0.087 0.083 0.117

Yellowstone 2002 0.405 0.264 0.141 0.237 0.168 0.148 0.257

Yellowstone 2003 0.356 0.210 0.146 0.181 0.175 0.102 0.254

Unit 3

Bridger 2001 0.668 0.412 0.256 0.357 0.311 0.253 0.415

Bridger 2002 1.312 0.879 0.433 0.771 0.541 0.447 0.865

Bridger 2003 0.696 0.434 0.262 0.376 0.320 0.233 0.463

Fitzpatrick 2001 0.369 0.241 0.128 0.212 0.157 0.133 0.236

Fitzpatrick 2002 0.581 0.394 0.187 0.353 0.228 0.239 0.342

Fitzpatrick 2003 0.327 0.208 0.119 0.182 0.145 0.113 0.214

Mt. Zirkel 2001 1.042 0.667 0.375 0.582 0.460 0.354 0.688

Mt. Zirkel 2002 1.352 0.851 0.501 0.744 0.608 0.434 0.918

Mt. Zirkel 2003 1.161 0.698 0.463 0.592 0.569 0.332 0.829

Rawah 2001 0.779 0.477 0.302 0.408 0.371 0.239 0.540

Rawah 2002 0.911 0.554 0.357 0.487 0.424 0.337 0.574

Rawah 2003 1.042 0.628 0.414 0.535 0.507 0.293 0.749

RMNP 2001 0.550 0.353 0.197 0.319 0.231 0.180 0.370

RMNP 2002 0.960 0.618 0.342 0.536 0.424 0.307 0.653

RMNP 2003 0.906 0.565 0.341 0.488 0.418 0.290 0.616

Grand Teton 2001 0.264 0.172 0.092 0.153 0.111 0.093 0.171

Grand Teton 2002 0.301 0.186 0.115 0.161 0.140 0.152 0.149

Grand Teton 2003 0.376 0.237 0.139 0.206 0.170 0.124 0.252

Teton 2001 0.253 0.164 0.089 0.146 0.107 0.098 0.155

Teton 2002 0.391 0.258 0.133 0.228 0.163 0.147 0.244

Teton 2003 0.356 0.221 0.135 0.191 0.165 0.118 0.238
22

Unit Class I Area

by Year

New Baseline Scenario 1 Scenario 2 Scenario 3

98th Percentile

Visibility Impact 

(∆dv)

98th Percentile

Visibility Impact 

(∆dv)

Visibility Improvement 

(∆dv)

98th Percentile

Visibility Impact 

(∆dv)

Visibility Improvement 

(∆dv)

98th Percentile

Visibility Impact 

(∆dv)

Visibility Improvement 

(∆dv)

Washakie 2001 0.369 0.229 0.140 0.198 0.171 0.126 0.243

Washakie 2002 0.408 0.255 0.153 0.221 0.187 0.153 0.255

Washakie 2003 0.232 0.151 0.081 0.137 0.095 0.105 0.127

Yellowstone 2001 0.194 0.126 0.068 0.114 0.080 0.082 0.112

Yellowstone 2002 0.395 0.266 0.129 0.238 0.157 0.145 0.250

Yellowstone 2003 0.345 0.212 0.133 0.182 0.163 0.101 0.244

Unit 4

Bridger 2001 0.739 0.426 0.313 0.369 0.370 0.258 0.481

Bridger 2002 1.420 0.861 0.559 0.741 0.679 0.415 1.005

Bridger 2003 0.781 0.467 0.314 0.409 0.372 0.250 0.531

Fitzpatrick 2001 0.426 0.260 0.166 0.229 0.197 0.142 0.284

Fitzpatrick 2002 0.638 0.412 0.226 0.368 0.270 0.252 0.386

Fitzpatrick 2003 0.371 0.216 0.155 0.189 0.182 0.122 0.249

Mt. Zirkel 2001 1.189 0.698 0.491 0.606 0.583 0.355 0.834

Mt. Zirkel 2002 1.475 0.846 0.629 0.722 0.753 0.464 1.011

Mt. Zirkel 2003 1.281 0.730 0.551 0.623 0.658 0.342 0.939

Rawah 2001 0.832 0.476 0.356 0.407 0.425 0.231 0.601

Rawah 2002 1.033 0.587 0.446 0.501 0.532 0.321 0.712

Rawah 2003 0.958 0.565 0.393 0.496 0.462 0.288 0.670

RMNP 2001 0.629 0.354 0.275 0.304 0.325 0.185 0.444

RMNP 2002 1.064 0.646 0.418 0.561 0.503 0.317 0.747

RMNP 2003 0.927 0.558 0.369 0.488 0.439 0.295 0.632

Grand Teton 2001 0.305 0.178 0.127 0.159 0.146 0.091 0.214

Grand Teton 2002 0.451 0.275 0.176 0.241 0.210 0.152 0.299

Grand Teton 2003 0.404 0.242 0.162 0.210 0.194 0.118 0.286

Teton 2001 0.324 0.189 0.135 0.165 0.159 0.103 0.221

Teton 2002 0.406 0.258 0.148 0.224 0.182 0.132 0.274

Teton 2003 0.337 0.196 0.141 0.170 0.167 0.121 0.216

Washakie 2001 0.447 0.256 0.191 0.219 0.228 0.120 0.327

Washakie 2002 0.443 0.266 0.177 0.232 0.211 0.156 0.287

Washakie 2003 0.269 0.161 0.108 0.140 0.129 0.104 0.165
23

Unit Class I Area

by Year

New Baseline Scenario 1 Scenario 2 Scenario 3

98th Percentile

Visibility Impact 

(∆dv)

98th Percentile

Visibility Impact 

(∆dv)

Visibility Improvement 

(∆dv)

98th Percentile

Visibility Impact 

(∆dv)

Visibility Improvement 

(∆dv)

98th Percentile

Visibility Impact 

(∆dv)

Visibility Improvement 

(∆dv)

Yellowstone 2001 0.236 0.129 0.107 0.112 0.124 0.084 0.152

Yellowstone 2002 0.436 0.268 0.168 0.236 0.200 0.144 0.292

Yellowstone 2003 0.346 0.201 0.145 0.173 0.173 0.097 0.249