1 

### Summary of **EPA ’s Additional Visibility Improvement**  **Modeling** EPA 

### performed additional modeling of NOx control scenarios for both BART and reasonable progress sources. **All Region 8 modeling files are available upon request.** Contact Laurel Dygowski at dygowski.laurel@epa.gov. For baseline emissions, the BART Guidelines recommend that states use the maximum 24

-hour average actual emission rate for the meteorological period being modeled. 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 a 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. For consistency, EPA’s 

### additional modeling to ascertain visibility improvements from individual NOx controls used the state’s baseline emission rates for the Pacificor p sites and Basin Electric’s Laramie River Station. All other aspects of EPA’s additional visibility modeling followed the recommendations made in the BART Guidelines


### . The tables beginning on page 4 show the CALPUFF inputs used for each unit modeled. EPA’s modeling modified the state of Wyoming’s 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 inputs 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.asp2



### EPA’s modeling utilized the emission and stack parameter CALPUFF inputs from “Post

-Control Scenario A” in the reports for its Scenarios 1

-3 with the only difference between scenarios being the emission rate for NOx and, in the SCR scenarios, total sulfate rates were increased to account for the additional production that results from SCR controls

. EPA’s “New Baseline” is essentially the state’s “Post

-Control Scenario A” but with the NOx emission rate from their “Baseline” scenario. Table 1 summarizes the control scenarios from EPA’s additional modeling for BART sources.
**Table 1 -**  **Description of EPA control scenarios for Wyoming’s BAR T sources**  **EPA Scenario Description**  New Baseline Post
-Control Scenario A from state‘s BART Application Analysis with NOx

emission rate from state’s “Baseline” scenario Scenario 1 Post
-Control Scenario A from state ’s BART Application Analysis with NOx

emission rate that reflects the visibility improvement from LNB/OFA controls. Scenario 2 Post
-Control Scenario A from state ’s BART Application Analysis with NOx

emission rate that reflects the visibility improvement from SNCR controls Scenario 3 Post
-Control Scenario A from state ’s BART Application Analysis with NOx

emission rate that reflects the visibility improvement from SCR controls EPA also performed additional modeling for Dave Johnston’s Units 1 and 2. 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. Permit limit emission rates with heat input were used to derive emission inputs in the “New Baseline” scenario. Similar to the BART sources, the only differences in the control scenarios are the emission rates for NOx and, in the SCR scenario (Scenario 3), total sulfate rates were increased to account for the additional production that results from SCR controls. Stack parameter data for these sources was 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.3



### Table 2

**– Description of EPA control scenarios for Reasonable Progress sources (Dave**  **Johnston Units 1 and 2) EPA Scenario**  **Description** New Baseline Inputs obtained from facility’s Title V Operating Permit limits Scenario 0 Same inputs as New Baseline with a NOx emission rate that reflect visibility

improvements from LNB controls Scenario 1 Same inputs as New Baseline with a NOx emission rate that reflect visibility

improvements from LNB/OFA controls Scenario 2 Same inputs as New Baseline with a NOx emission rate that reflect visibility

improvements from SNCR controls Scenario 3 Same inputs as New Baseline with a NOx emission rate that reflect visibility

improvements from SCR controls4

**P acificorp**  **- Dave Johnston Unit 3**  New Baseline Scenario 1 Scenario 2 Scenario 3 Hourly Heat Input (mmBtu/hour) 2800 2800 2800 2800 Emission Rates SO2 (lb/MMBtu) 0.15 0.15 0.15 0.15

Nox (lb/MMBtu) 0.7 0.28 0.19 0.07

Calpuff Inputs SO2 (lb/hr) 420 420 420 420

Total Sulfate (SO4)(lb/hr) 2.5 2.5 2.5 5.1 Nox (lb/hr) 1960 784 532 196 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 **Pacificorp -**  **Dave Johnston Unit 4** New Baseline Scenario 1 Scenario 2 Scenario 3 Hourly Heat Input (mmBtu/hour) 4100 4100 4100 4100 Emission Rates SO2 (lb/MMBtu) 0.15 0.15 0.15 0.15

Nox (lb/MMBtu) 0.4 0.15 0.12 0.07

Calpuff Inputs SO2 (lb/hr) 615 615 615 615

Total Sulfate (SO4)(lb/hr) 3.7 3.7 3.7 7.4 Nox (lb/hr) 1640 615 492 287 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 3505

**Pacificorp -**  **Jim Bridger Unit 1** New Baseline Scenario 1 Scenario 2 Scenario 3 Hourly Heat Input (mmBtu/hour) 6000 6000 6000 6000 Emission Rates SO2 (lb/MMBtu) 0.15 0.15 0.15 0.15

Nox (lb/MMBtu) 0.45 0.26 0.2 0.07

Calpuff Inputs SO2 (lb/hr) 900 900 900 900

Total Sulfate (SO4)(lb/hr) 54.1 54.1 54.1 108.1 Nox (lb/hr) 2700 1560 1200 420 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 **Pacificorp -**  **Jim Bridger Unit 2** New Baseline Scenario 1 Scenario 2 Scenario 3 Hourly Heat Input (mmBtu/hour) 6000 6000 6000 6000 Emission Rates SO2 (lb/MMBtu) 0.15 0.15 0.15 0.15

Nox (lb/MMBtu) 0.24 0.26 0.2 0.07

Calpuff Inputs SO2 (lb/hr) 900 900 900 900

Total Sulfate (SO4)(lb/hr) 54.1 54.1 54.1 108.1 Nox (lb/hr) 1440 1560 1200 420 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

**P acificorp**  **- Jim Bridger Unit 4** 6 New Baseline Scenario 1 Scenario 2 Scenario 3 Hourly Heat Input (mmBtu/hour) 6000 6000 6000 6000 Emission Rates SO2 (lb/MMBtu) 0.15 0.15 0.15 0.15

Nox (lb/MMBtu) 0.45 0.26 0.2 0.07

Calpuff Inputs SO2 (lb/hr) 900 900 900 900

Total Sulfate (SO4)(lb/hr) 54.1 54.1 54.1 108.1 Nox (lb/hr) 2700 1560 1200 420 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 **Pacificorp -**  **Naughton Unit 1** New Baseline Scenario 1 Scenario 2 Scenario 3 Hourly Heat Input (mmBtu/hour) 1850 1850 1850 1850 Emission Rates SO2 (lb/MMBtu) 0.15 0.15 0.15 0.15

Nox (lb/MMBtu) 0.58 0.26 0.21 0.07

Calpuff Inputs SO2 (lb/hr) 278 278 278 278

Total Sulfate (SO4)(lb/hr) 16.7 16.7 16.7 33.3 Nox (lb/hr) 1073 481 389 130 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 3237

**Pacificorp -**  **Naughton Unit 2** New Baseline Scenario 1 Scenario 2 Scenario 3 Hourly Heat Input (mmBtu/hour) 2400 2400 2400 2400 Emission Rates SO2 (lb/MMBtu) 0.15 0.15 0.15 0.15

Nox (lb/MMBtu) 0.54 0.26 0.21 0.07

Calpuff Inputs SO2 (lb/hr) 360 360 360 360

Total Sulfate (SO4)(lb/hr) 21.6 21.6 21.6 43.2 Nox (lb/hr) 1296 624 504 168 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 **Pacificorp -**  **Naughton Unit 3** New Baseline Scenario 1 Scenario 2 Scenario 3 Hourly Heat Input (mmBtu/hour) 3700 3700 3700 3700 Emission Rates SO2 (lb/MMBtu) 0.22 0.22 0.22 0.22

Nox (lb/MMBtu) 0.45 0.37 0.3 0.07

Calpuff Inputs SO2 (lb/hr) 814 814 814 814

Total Sulfate (SO4)(lb/hr) 33.3 33.3 33.3 66.6 Nox (lb/hr) 1665 1369 1110 259 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 3228

**Pacificorp –**  **Wyodak** Note: CALPUFF inputs for Pacificorp’s Wyodak facility were inadvertently left out of the original “CALPUFF Modeling Summary” file. New Baseline Scenario 1 Scenario 2 Scenario 3 Hourly Heat Input (mmBtu/hour) 4700 4700 4700 4700 Emission Rates SO2 (lb/MMBtu) 0.16 0.16 0.16 0.16

Nox (lb/MMBtu) 0. 31 0. 23 0.18 0.07

Calpuff Inputs SO2 (lb/hr) 759 759 759 759

Total Sulfate (SO4)(lb/hr) 5.5 5.5 5.5 11.6 Nox (lb/hr) 1457 1081 846 329 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 3509

**Basin Electric –**  **Laramie River Station Unit 1** New Baseline Scenario 1 Scenario 2 Scenario 3 Hourly Heat Input (mmBtu/year) 46814433 46814433 46814433 46814433 Emission Rates SO2 (lb/MMBtu) 0.16 0.16 0.16 0.16

Nox (lb/MMBtu) 0.27 0.23 0.12 0.07

Calpuff Inputs SO2 (tpy) 3745 3745 3745 3745

Total Sulfate (SO4)(tpy) 3.06 3.18 3.18 3.18 Nox (tpy) 6320 5384 2809 1639 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
**Basin Electric –**  **Laramie River Station Unit 2** New Baseline Scenario 1 Scenario 2 Scenario 3 Hourly Heat Input (mmBtu/year) 46557738 46557738 46557738 46557738 Emission Rates SO2 (lb/MMBtu) 0.16 0.16 0.16 0.16

Nox (lb/MMBtu) 0.27 0.23 0.12 0.07

Calpuff Inputs SO2 (tpy) 3725 3725 3725 3725

Total Sulfate (SO4)(tpy) 2.8 3.25 3.25 3.25 Nox (tpy) 6285 5354 2793 1630 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 338.705610

**Basin Electric –**  **Laramie River Station Unit 3** New Baseline Scenario 1 Scenario 2 Scenario 3 Hourly Heat Input (mmBtu/year) 47765529 47765529 47765529 47765529 Emission Rates SO2 (lb/MMBtu) 0.17 0.17 0.17 0.17

Nox (lb/MMBtu) 0.27 0.23 0.12 0.07

Calpuff Inputs SO2 (tpy) 4060 4060 4060 4060

Total Sulfate (SO4)(tpy) 0.22 0.22 0.22 0.22 Nox (tpy) 6448 5493 2866 1672 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) 352.0 352.0 352.0 352.011



### Reasonable Progress Sources **Dave Johnston Unit 1** New Baseline Scenario

0 Scenario

1 Scenario

2 Scenario

3 Hourly Heat Input (mmBtu/hour) 1350 1350 1350 1350 1350 Emission Rates SO2 (lb/MMBtu) 1.2 1.2 1.2 1.2 1.2

Nox (lb/MMBtu) 0.75 0.3675 0.2625 0.45 0.15

Calpuff Inputs SO2 (lb/hr) 1620 1620 1620 1620 0

Total Sulfate (SO4)(lb/hr) 1 1 1 1 2 Nox (lb/hr) 1012.5 496.125 354.375 607.5 202.5 HNO3 0 0 0 0 0 NO3 0 0 0 0 0 PM10
-2.5 (coarse PM)(lb/hr) 149.726 149.726 149.726 149.726 149.726 PM2.5 (lb/hr) 198.474 198.474 198.474 198.474 198.474 Stack Height (meters) 152.4 152.4 152.4 152.4 152.4 Base Elevation (meters) 1509 1509 1509 1509 1509 Stack Diameter (meters) 3.35 3.35 3.35 3.35 3.35 Exit Velocity (meters/second) 28.35 28.35 28.35 28.35 28.35 Exit Temperature (Kelvin) 418.15 418.15 418.15 418.15 418.15
**Dave Johnston Unit 2** New Baseline Scenario

0 Scenario

1 Scenario

2 Scenario

3 Hourly Heat Input (mmBtu/hour) 1350 1350 1350 1350 1350 Emission Rates SO2 (lb/MMBtu) 1.2 1.2 1.2 1.2 1.2

Nox (lb/MMBtu) 0.75 0.3675 0.2625 0.45 0.15

Calpuff I nputs SO2 (lb/hr) 1620 1620 1620 1620 1620

Total Sulfate (SO4)(lb/hr) 1 1 1 1 2 Nox (lb/hr) 1012.5 496.125 354.375 607.5 202.5 HNO3 NO3 PM10
-2.5 (coarse PM)(lb/hr) 149.726 149.726 149.726 149.726 149.726 PM2.5 (lb/hr) 198.474 198.474 198.474 198.474 198.474 Stack Height (meters) 152.4 152.4 152.4 152.4 152.4 Base Elevation (meters) 1509 1509 1509 1509 1509 Stack Diameter (meters) 3.35 3.35 3.35 3.35 3.35 Exit Velocity (meters/second) 28.69 28.69 28.69 28.69 28.69 Exit Temperature (Kelvin) 425.93 425.93 425.93 425.93 425.93