DRAFT

FINAL REPORT

BART AIR MODELING

INDIVIDUAL SOURCE VISIBILITY 

IMPAIRMENT ANALYSIS

April, 2006

Prepared For:

State of Wyoming

Department of Environmental Quality

Air Quality Division

Cheyenne, WY 82002

Prepared By:

McVehil-Monnett Associates, Inc.

44 Inverness Dr. E., Bldg. C

Englewood, CO 80112

MMA Project Number 1938-05-3
TABLE OF CONTENTS

Section Page

1.0 INTRODUCTION ...............................................................................................................1

2.0 OVERVIEW ........................................................................................................................2

3.0 POLLUTANTS AND EMISSIONS....................................................................................5

4.0 MODELING DOMAIN AND METEOROLOGICAL DATA .........................................11

5.0 CALMET INPUT ..............................................................................................................14

6.0 CALPUFF MODELING....................................................................................................16

7.0 POSTPROCESSING .........................................................................................................18

8.0 DETERMINATION OF SOURCES SUBJECT TO BART .............................................22

APPENDIX A: SOURCES OF METEOROLOGICAL AND OZONE 

MONITORING DATA

Tables

1 WYOMING BART – ELIGIBLE SOURCES.....................................................................4

2 MAXIMUM 24-HR EMISSION RATES FOR BART

 SOURCE ATTRIBUTION MODELING.......................................................................6

3 STACK PARAMETERS FOR BART SOURCE ATTRIBUTION MODELING .............9

4 SOURCE-SPECIFIC MODEL DOMAINS AND METEROLOGICAL 

 DATA YEARS .............................................................................................................12

5 CALMET INPUT PARAMETERS THAT ARE APPLICATION-

 SPECIFIC OR DIFFER FROM DEFAULT VALUES................................................15

6 CALPUFF INPUT PARAMETERS THAT ARE APPLICATION-

 SPECIFIC OR DIFFER FROM DEFAULT VALUES................................................17

7 MONTHLY F(RH) FACTORS FOR CLASS I AREAS ..................................................20

8 NATURAL BACKGROUND CONCENTRATIONS OF AEROSOL 

 COMPONENTS FOR 20% BEST DAYS FOR BART ANALYSIS (μg/m3).............21

9 RESULTS OF CALPUFF VISIBILITY MODELING FOR BART-ELEGIBLE 

SOURCES....................................................................................................................24
1

1.0 INTRODUCTION

The U.S. EPA has issued final amendments to the Regional Haze Regulations, 

along with Guidelines for Best Available Retrofit Technology (BART) Determinations.(1) 

The Guidelines address methodology for determining which facilities must apply BART 

(sources subject to BART) and the evaluation of control options.

The State of Wyoming has utilized air quality modeling, using the CALPUFF 

modeling system, in accordance with the EPA Guidelines to determine the Wyoming 

sources which are subject to BART. This report describes the specific methodology 

applied in the air quality modeling analysis, and presents analysis results defining those 

Wyoming sources that have been determined to be subject to BART.

 

(1) 40 CFR Part 51: Regional Haze Regulations and Guidelines for Best Available Retrofit Technology 

(BART) Determinations; Final Rule. 70 Federal Register, 39103-39172, July 6, 2005.
2

2.0 OVERVIEW

The Wyoming Air Quality Division determined that there are fourteen “BARTEligible” sources in the State. The sources are listed in Table 1. Modeling and analyses 

described in this report were used to determine, for each of these sources, whether they 

are “subject to BART”.(2) A source is subject to BART if air quality modeling indicates 

that the source causes or contributes to visibility impairment in any Class I area, within or 

outside of Wyoming.

Class I areas that could potentially experience visibility impairment due to 

emissions from Wyoming sources were initially defined as all of those within 300 km of 

any BART-eligible source.

In Wyoming: N. Absaroka WA

Washakie WA

Yellowstone NP

Teton WA

Fitzpatrick WA

Bridger WA

Grand Teton NP

In Colorado: Rawah WA

Rocky Mountain NP

Mt. Zirkel WA

Flat Tops WA

Eagles Nest WA

Maroon Bells – Snowmass WA

West Elk WA

In Utah: Arches NP

In South Dakota: Badlands NP

Wind Cave NP

In Idaho: Craters of the Moon NM

Not all of these Class I areas were included in modeling analyses. For each BARTeligible source, those Class I areas deemed most likely to experience visibility impacts on 

the basis of distance, meteorology, and terrain were assessed in the analysis. Modeling 

domains, sources, and the Class I areas addressed for each source are described in 

subsequent parts of the report.

 

2 All sources except Dyno Nobel N.A. and OCI Wyoming are addressed in this report. Those two sources 

were analyzed in separate but identical analyses.
3

Wyoming has followed the BART guideline for evaluation of all BART-eligible 

sources. The threshold for classification of a source as subject to BART is a visibility 

impact exceeding 0.5 deciview (dv) compared to the 20% best days natural background, 

based on the 98th percentile of modeled 24-hour delta – deciview values.
4

Table 1. Wyoming BART – Eligible Sources

Basin Electric Laramie River Power Plant Boilers # 1, 2, 3

Black Hills P & L Neil Simpson # 1 Power Plant Boiler

Dyno Noble N.A. Cheyenne Plant Misc. Sources

FMC Corporation Granger Soda Ash Plant Boilers # 1, 2

FMC Corporation Green River Sodium Plant Three boilers

General Chemical Co. Green River Soda Ash Two boilers

OCI Wyoming Big Island Soda Ash Plant Boilers # 4, 5, 6

P4 Production Rock Springs Coking Plant Calciner

PacifiCorp Dave Johnson Power Plant Boilers # 3, 4

PacifiCorp Jim Bridger Power Plant Boilers # 1 – 4

PacifiCorp Naughton Power Plant Boilers # 1, 2, 3

PacifiCorp Wyodak Power Plant Boiler

Sinclair Oil Co. Casper Refinery Boiler # 7

Sinclair Oil Co. Sinclair Refinery Misc. Sources
5

3.0 POLLUTANTS AND EMISSIONS

The pollutants included in the CALPUFF modeling analyses were sulfur dioxide 

(SO2), nitrogen oxides (NOx), and particulate matter. Where data were available, 

particulate matter emissions were quantified separately as fine particles (PM2.5) and 

coarse particles (PM10). If no particle size information was available, all particles were

assumed to be PM2.5. Emissions of ammonia (NH3) and volatile organic compounds 

(VOC) were not considered. It is believed that emissions of these pollutants have 

negligible impact on regional haze in Wyoming.

Table 2 presents a listing of emission rates modeled for all BART-eligible 

sources. The emission rates were determined by the Division based upon existing 

permits, allowable rates, and emissions reporting data. They represent the best available 

estimates of maximum 24-hour average emissions for each source and pollutant. Table 3 

lists stack parameters for each source. The data in Tables 2 and 3 were used for all 

BART modeling to define the individual source’s impact on visibility.
6

Table 2. Maximum 24-hr Emission Rates for BART Source Attribution Modeling

Source Emission Unit NOx SO2 PM2.5 PM10

lb/hr g/s lb/hr g/s lb/hr g/s lb/hr g/s

Basin Electric Boiler # 1 2619.4 330.04 1284.0 161.78 158.3 19.95 387.7 48.85

Laramie River Boiler # 2 1502.3 189.29 1284.0 161.78 158.3 19.95 387.7 48.85

Boiler # 3 2719.2 342.61 1320.0 166.32 158.9 20.02 389.1 49.03

Black Hills Boiler 112.8 14.21 351.6 44.30 28.0 3.53 68.7 8.66

Neil Simpson # 1

Dyno Nobel IC Engine 170.6 21.50

IC Engine 170.6 21.50

Nitric Acid Plant 6.0 0.76

Nitric Acid Plant 6.0 0.76

Prill Tower 54.0 6.80

Wet Scrubber 19.7 2.48

Wet Scrubber 15.8 1.99

Prill Tower 43.1 5.43

Boiler 6.1 0.77

FMC Corporation Boiler # 1 251.0 31.63 71.7 9.03 35.8 4.51

Granger Soda Ash Boiler # 2 251.0 31.63 71.7 9.03 35.8 4.51

FMC Corporation NS-1A Boiler 523.3 65.93 1064.4 134.1 45.0 5.67

Sodium Products NS-1B Boiler 374.3 47.16 1064.4 134.1 45.0 5.67

PH-3 Boiler 43.4 5.47 8.4 1.06

General Chemical Boiler C 245.6 30.95 640.8 80.74 50.0 6.30

Green River Soda Ash Boiler D 501.6 63.20 1056.0 133.05 80.0 10.08
7

Table 2. Maximum 24-hr Emission Rates for BART Source Attribution Modeling (Continued)

Source Emission Unit NOx SO2 PM2.5 PM10

lb/hr g/s lb/hr g/s lb/hr g/s lb/hr g/s

OCI Boiler # 4 13.3 1.68 7.5 0.95

Big Island Boiler # 5 13.3 1.68 8.6 1.08

Boiler # 6 13.3 1.68

P4 Production Calciner 72.9 9.19 218.0 27.47 22.0 2.77

Pacificorp Boiler # 3 1194.2 150.47 2671.0 336.54 149.0 18.77 364.9 45.98

Dave Johnston Boiler # 4 1447.3 182.36 1737.0 218.86 372.5 46.93 357.9 45.09

Pacificorp Boiler # 1 2008.4 253.05 1683.0 212.05 162.7 20.50 398.3 50.19

Jim Bridger Boiler # 2 1716.7 216.30 1683.0 212.05 162.7 20.50 398.3 50.19

Boiler # 3 1941.1 244.57 1683.0 212.05 162.7 20.50 398.3 50.19

Boiler # 4 2030.8 255.88 1004.0 126.50 145.6 18.35 356.4 44.91

Pacificorp Boiler # 1 1079.8 136.05 2218.8 279.56 129.5 16.32 317.1 39.95

Naughton Plant Boiler # 2 1322.5 166.63 2844.0 358.34 159.0 20.03 389.3 49.05

Boiler # 3 2052.9 258.66 1839.5 231.77 228.6 28.80 559.7 70.52

Pacificorp Boiler 1189.0 149.81 2050.0 258.30 118.9 14.98 291.1 36.68

Wyodak

Sinclair Boiler 26.7 3.36 98.2 12.37 15.6 1.97

Casper Refinery
8

Table 2. Maximum 24-hr Emission Rates for BART Source Attribution Modeling (Continued)

Source Emission Unit NOx SO2 PM2.5 PM10

lb/hr g/s lb/hr g/s lb/hr g/s lb/hr g/s

Sinclair Heater 15.6 1.97

Refinery Heater 7.9 1.00

Heater 5.5 0.69

Heater 5.5 0.69

Heater 9.6 1.21 1.0 0.13

Heater 2.1 0.26 0.5 0.06

Heater 2.6 0.33 0.3 0.04

Heater 3.2 0.40

Heater 3.8 0.48

Heater 8.6 1.08

Heater 3.4 0.43

Heater 9.0 1.13

Heater 1.8 0.23

Heater 4.3 0.54

Boiler # 10 23.0 2.90 2.3 0.29

SRU # 1 5.1 0.64 340.0 42.84
9

Table 3. Stack Parameters for BART Source Attribution Modeling

Source Emission Unit Height Temp Vel Dia

(m) (K) (m/s) (m)

Basin Electric Boiler # 1 182.9 332.2 15.2 9.54

Laramie River Boiler # 2 182.9 332.2 15.2 9.54

Boiler # 3 182.9 358.2 22.9 8.66

Black Hills Boiler 76.2 442.4 21.9 1.83

Neil Simpson # 1

Dyno Nobel IC Engine 13.41 485.9 16.78 1.68

IC Engine 13.41 485.9 16.78 1.68

Nitric Acid Plant 21.34 438.7 11.88 0.61

Nitric Acid Plant 21.34 438.7 11.88 0.61

Prill Tower 39.93 310.4 24.23 1.52

Wet Scrubber 23.62 294.3 51.51 0.46

Wet Scrubber 51.21 369.3 6.89 0.46

Prill Tower 41.76 357.6 2.72 3.55

Boiler 21.34 505.4 5.15 0.33

FMC Corporation Boiler # 1 45.72 333.2 21.29 1.98

Granger Soda Ash Boiler # 2 45.72 333.2 21.2 1.98

FMC Corporation NS-1A Boiler 91.44 414.8 54.49 1.83

Sodium Products NS-1B Boiler 91.44 410.9 54.96 1.83

PH-3 Boiler 21.34 394.3 8.34 2.29

General Chemical Boiler C 47.55 452.6 15.98 3.05

Green River Soda Ash Boiler D 47.55 460.9 25.12 3.05

OCI Boiler # 4 16.76 434.1 18.39 1.98

Big Island Boiler # 5 24.38 440.1 21.53 1.83

Boiler # 6 24.38 434.1 21.53 1.83

P4 Production Calciner 39.62 1255.4 12.24 4.75

Pacificorp Boiler # 2 152.4 444.8 33.22 4.57

Dave Johnston Boiler # 3 76.2 325.9 8.53 7.01
10

Table 3. Stack Parameters for BART Source Attribution Modeling (Continued)

Source Emission Unit Height Temp Vel Dia

(m) (K) (m/s) (m)

Pacificorp Boiler # 1 152.4 333.2 22.3 7.32

Jim Bridger Boiler # 2 152.4 333.2 22.3 7.32

Boiler # 3 152.4 333.2 25.2 7.32

Boiler # 4 152.4 333.2 13 9.45

Pacificorp Boiler # 1 60.96 410.8 26.52 4.27

Naughton Plant Boiler # 2 68.58 410.8 21.34 4.88

Boiler # 3 137.16 323 19.81 8.08

Pacificorp Boiler 121.9 346.9 22.6 6.1

Wyodak

Sinclair Boiler 41.39 549.8 12.9 1.37

Casper Refinery

Sinclair Heater 33.53 672 10.3 0.76

Refinery Heater 36.6 477.6 4.39 1.22

Heater 27.43 1016.5 9.33 1.22

Heater 33.53 630.4 8.09 0.91

Heater 45.72 727.6 5.88 1.52

Heater 19.2 855.4 2.08 1.22

Heater 41.15 635.9 2.24 1.22

Heater 36.6 838.7 6.49 1.22

Heater 36.6 866.5 3.4 1.52

Heater 36.6 866.5 6.96 1.52

Heater 36.6 833.2 5.15 1.52

Heater 36.6 683.2 13.47 0.91

Heater 12.8 810.9 8.35 0.91

Heater 27.4 716.5 5.03 1.22

Boiler # 10 15.24 449.8 9.08 1.52

SRU # 1 49.1 810.9 1.4 1.52
11

4.0 MODELING DOMAIN AND METEOROLOGICAL DATA

The determination of those sources subject to BART was carried out through 

application of the CALPUFF modeling system. Wind and meteorological fields for 

CALPUFF were developed using the CALMET meteorological processor; input data

consisted of MM5 prognostic model fields, augmented with surface and upper air data 

from observing stations within the model domain.

The Class I areas potentially affected by Wyoming sources are located over a 

large area within and surrounding the state. Wyoming BART – eligible sources are 

widely distributed within the state. Therefore, a very large modeling domain would be 

required to address all sources and Class I areas. It was also desired to utilize to the 

extent possible meteorological data fields previously used for long-range transport 

modeling that have been checked and quality assured. For these reasons, BART 

modeling utilized three separate modeling domains and two meteorological data sets.

The model domains included a Southwest Wyoming domain, utilizing 

meteorological data for 1995, 1996, and 2001, and Northeast and Southeast Wyoming 

domains with 2001, 2002, and 2003 meteorological data. The southwest and northeast 

data sets were developed for prior Wyoming analyses and were readily adapted for 

BART modeling. The southeast domain meteorological fields were developed 

specifically for the BART analyses. MM5 model output for the southeast domain were

acquired by the Division, and used in CALMET (with additional surface and upper air 

data) to generate required input meteorological fields for CALPUFF. The three modeling 

domains, along with the locations of Class I areas and BART – eligible sources, are 

shown in Figure 1.

Model domains and Class I areas used for each source’s BART evaluation are 

shown in Table 4. The assignments in Table 4 were developed on the basis of 

source/Class I area locations, distances to each Class I area, and professional judgment 

considering meteorological and terrain factors. All source-Class I area distances exceed 

50 km, and are less than 300 km, thus falling within the range of recommended 

CALPUFF application.

Only those Class I areas most likely to be impacted by each source were modeled. 

Areas greater than 300 km from a source have been excluded. Also, when several Class I 

areas are located in the same direction from a source, only the closest Class I areas were

evaluated. If impacts are less than the BART threshold for the Class I areas modeled, it 

can be reasonably assumed that areas at a greater distance and in directions of less 

frequent plume transport will not experience significant impacts.

 
12

Table 4. Source-Specific Model Domains and Meteorological Data Years

Source Modeling

Domain

Meteorological

Data Years

Class I Areas

to be Evaluated

1. Basin Electric Northeast WY 2001, 2002, 2003 Wind Cave, Badlands

 Laramie River

2. Black Hills Northeast WY 2001, 2002, 2003 Wind Cave, Badlands

 Neil Simpson # 1

3. Dyno Nobel Southeast WY 2001, 2002, 2003 Rocky Mountain NP, Rawah, 

 Cheyenne Plant Mt. Zirkel

4. FMC Corporation Southwest WY 1995, 1996, 2001 Bridger, Fitzpatrick

 Granger Soda Ash

5. FMC Corporation Southwest WY 1995, 1996, 2001 Bridger, Fitzpatrick 

 Sodium Products

6. General Chemical Southwest WY 1995, 1996, 2001 Bridger, Fitzpatrick

 Green River Soda Ash

7. OCI Southwest WY 1995, 1996, 2001 Bridger, Fitzpatrick 

 Big Island Plant

8. P4 Production Southwest WY 1995, 1996, 2001 Bridger, Fitzpatrick 

 Rock Springs Coking

9. Pacificorp Northeast WY 2001, 2002, 2003 Wind Cave, Badlands

 Dave Johnston
13

Table 4. Source-Specific Model Domains and Meteorological Data Years (Continued)

Source Modeling

Domain

Meteorological

Data Years

Class I Areas

to be Evaluated

10. Pacificorp Southwest WY 1995, 1996, 2001 Bridger, Fitzpatrick 

 Jim Bridger

11. Pacificorp Southwest WY 1995, 1996, 2001 Bridger, Fitzpatrick 

 Naughton Plant

12. Pacificorp Northeast WY 2001, 2002, 2003 Wind Cave, Badlands 

 Wyodak

13. Sinclair Northeast WY 2001, 2002, 2003 Wind Cave, Badlands

 Casper Refinery

14. Sinclair Southeast WY 2001, 2002, 2003 Rocky Mountain NP, Rawah, 

 Sinclair Refinery Mt. Zirkel
14

5.0 CALMET INPUT

Input options for CALMET generally applied default values except where 

application-specific choices are required. Table 5 summarizes the CALMET inputs. 

All MM5 prognostic data had 36 km resolution, except for the 1995 (southwest 

Wyoming) data set, which has 20 km resolution. The MM5 data were used in CALMET, 

along with data from surface, upper air, and precipitation observations, to generate the 

final meteorological files required as input to CALPUFF. Appendix A lists the surface 

and upper air stations from which data were used for each domain and meteorological 

year. The number of upper air stations used as input to the CALMET processing varied 

from none (1996 only) to three, depending upon the availability of data from 

representative stations. For 1996, the MM5 data fields were used alone to define upper 

air conditions.
15

Table 5. CALMET Input Parameters that are Application-Specific or Differ from Default 

Values

CALMET Input Parameter Value(s)

Input Group 2

 Map projection (PMAP) Lambert Conformal

 Grid spacing (DGRIDKM) 4

 Number vertical layers (NZ) 10

 Top of lowest layer (m) 20 

 Top of highest layer (m) 3500

Input Group 4

 Observation mode (NOOBS) 0

1 (for 1996 only)

Input Group 5

 Prog. Wind data (IPROG) 14

 (RMAX1) 30

 (RMAX2) 50

 (RMAX3) N/A

 Terrain influence (TERRAD) 15

 (R1) 5

 (R2) 25

Input Group 6

 Max mixing ht (ZIMAX) 3500

CALMET Model Version 5.53A, Level 040716
16

6.0 CALPUFF MODELING

CALPUFF modeling was conducted for each BART-eligible source to calculate 

concentrations of each visibility-impairing pollutant in each Class I area. Source 

emissions, meteorological data, and model domains were as prescribed in Sections 3.0 

and 4.0. Each source was modeled separately for each of three years of meteorological 

data, utilizing the CALMET meteorological fields generated for the applicable 

years/model domains.

Concentration calculations were made for all receptors within the designated 

Class I areas. Receptors were defined for each area by the standard receptor points 

developed by the Federal Land Managers (FLMs) and available from the National Park 

Service web site database. 

CALPUFF model options conformed with standard default values with limited 

exceptions. Table 6 lists non-default and application-specific parameters that were used 

in CALPUFF. Chemical transformation calculations used MESOPUFF II equations, and 

dispersion coefficients were PG coefficients (MDISP=3).

Since most of the sources have relatively tall stacks, and only impacts at distances 

greater than 50 km are of interest, building wake effects were not considered for any 

sources. Puff splitting were not used for CALPUFF modeling, in order to limit 

computation time to reasonable levels.

Background ozone concentrations were considered in the model by use of hourly 

ozone files from representative monitoring sites in each model domain.(3) A default 

ozone concentration (for missing data hours) was specified as 44 ppb, based on average 

data from northeast Wyoming. The background ammonia concentration was specified as 

2.0 ppb for all model domains. The value of 2.0 is based on monitoring data from nearby 

states and IWAQM guidance. North Dakota has specified a background ammonia 

concentration of 2.0 ppb for the western part of the state, as indicated by 2000-2001 

monitoring data from Beulah. Colorado found background ammonia concentrations of 

0.5 to 1.6 ppb for the Mt. Zirkel area. The IWAQM Phase II report suggests values of 

0.5 ppb for forested areas, 1.0 ppb for arid lands, and 10.0 ppb for agricultural lands 

(within a factor of two). Since a single background ammonia value must be specified 

within a model domain, a value of 2.0 ppb was selected as reasonable given the available 

data. Experience has suggested that this value is conservative in that it is unlikely to 

significantly limit nitrate formation in the model.

Default particle size data were used for all modeled particles except PM10. Since 

PM10 represents coarse particles with diameters between 2.5 and 10.0 μm, the massmean PM10 diameter was estimated as 7.0 μm.

 

3

See Appendix A for list of ozone stations.
17

Table 6. CALPUFF Input Parameters that are Application-Specific or Differ From 

Default Values

CALPUFF Input Parameter Value(s)

Input Group 1

 Number of species modeled (NSPEC) 7

 Number of species emitted (NSE) 4

Input Group 2

 Dispersion coefficients (MDISP) 3

Input Group 3

 Species Modeled SO2, SO4, NOx, HNO3, NO3, PM10, PM25

 Species emitted SO2, NOx, PM10, PM25

Input Group 4

 Map projection (PMAP) Lambert Conformal

 Grid spacing (DGRIDKM) 4

 Cell face heights (ZFACE) same as used for applicable CALMET 

 

 Sampling grid F

 

Input Group 8 

 Particle size parameters mean 0.48, st. dev. 2.0

except 7.0, 2.0 for PM10

Input Group 11

 Ozone input option (MOZ) 1 (hourly ozone files)

 Monthly ozone (BCKO3) 44 ppb

 Monthly ammonia (BCKNH3) 2.0 ppb

Input Group 12

 Max mixing height (XMAXZ1) same as applicable CALMET

CALPUFF Model Version 5.711A, Level 040716
18

7.0 POSTPROCESSING

The CALPOST processor is used in the final processing step to calculate 24-hour 

average visibility results. Output was specified in deciview (dv) units. The output 

consists of the highest deciview impact on each day from all receptors within each Class I 

area.

Calculations of light extinction were made for each pollutant modeled (sulfate, 

nitrate, coarse particles, and fine particles). The sum of all extinction values is then used 

to calculate the delta-dv change relative to natural background. Default extinction 

coefficients for each species, as given below, were used.

Ammonium sulfate 3.0

Ammonium nitrate 3.0

PM Coarse (PM10) 0.6

PM Fine (PM25) 1.0

Monthly average relative humidity factors F(RH) were used in the light extinction 

calculations to account for the hygroscopic characteristic of sulfate and nitrate particles. 

Monthly f(RH) values, from the EPA Guidance for Estimating Natural Visibility 

Conditions Under the Regional Haze Rule, are shown in Table 7 for each set of Class I 

areas. Values shown in Table 7 represent the average f(RH) for the Class I areas listed. 

In many cases the tabulated f(RH) values for a given month are the same for each Class I 

area within a group. Where differences occur, they are no greater than 0.3 units; the 

average values are within 0.1 to 0.2 units of the Guideline values for any individual area.

CALPOST visibility Method 6 (MVISBK=6) was used for determination of 

background visibility. It should be noted that when Method 6 is used, the CALPOST 

calculation of f(RH) and the CALPOST designation of maximum relative humidity 

(RHMAX) are irrelevant and not used for calculations.

The natural background conditions as a reference for determination of the deltadv change due to a source should be representative of the 20% best natural visibility days. 

EPA BART guidance provides the 20% best days deciview values for each Class I area 

on an annual basis, but does not provide species concentration data for the 20% best 

background conditions. These concentrations were needed for input to CALPOST.

Annual species concentrations corresponding to the 20% best days were

calculated for each Class I area to be addressed, by scaling back the annual average 

concentrations given in Guidance for Estimating Natural Visibility Conditions Under the 

Regional Haze Rule (Table 2-1). A separate scaling factor was derived for each Class I 

area such that, when multiplied by the Guidance table annual concentrations, the 20% 

best days deciview value for that area would be calculated. The scaled aerosol 

concentrations were then averaged over the Class I areas to be addressed in each model 

domain to provide data (to be used for each month) for CALPOST input. The 20% best 

days aerosol concentrations used for Wyoming BART evaluations are listed in Table 8.
19

Concentrations were generally very similar at all of the Class I areas in a given 

model domain. Comparison of predicted deciview values for individual Class I areas 

(using annual average f(RH) and concentrations from Table 8) to the Guidance 20% best 

deciview tabulations show agreement within one percent for all Class I areas.
20

Table 7. Monthly f(RH) Factors for Class I Areas

Month Wind Cave NP

Badlands NP

Bridger WA

Fitzpatrick WA

Rocky Mt. NP

Rawah WA

Mt. Zirkel WA

 Jan 2.65 2.50 2.10

 Feb 2.65 2.30 2.13

 Mar 2.65 2.27 2.00

 Apr 2.55 2.10 2.10

 May 2.70 2.10 2.23

 Jun 2.60 1.83 1.87

 Jul 2.30 1.57 1.77

 Aug 2.30 1.53 1.83

 Sep 2.20 1.80 2.00

 Oct 2.25 2.03 1.87

 Nov 2.75 2.47 2.07

 Dec 2.65 2.43 2.03
21

Table 8. Natural Background Concentrations of Aerosol Components for 20% Best Days for BART Analyses (μg/m3).

Aerosol

Component

Wind Cave NP

Badlands NP

Fitzpatrick WA

Bridger WA

Rawah WA

Rocky Mountain NP

Mt. Zirkel WA

 Ammonium Sulfate .047 .045 .045

 Ammonium Nitrate .040 .038 .037

 Organic Carbon .186 .178 .178

 Elemental Carbon .008 .008 .007

 Soil .198 .189 .189

 Coarse Mass 1.191 1.136 1.135
22

8.0 DETERMINATION OF SOURCES SUBJECT TO BART

Results of the CALPOST visibility processing for each BART-eligible source 

consisted of a listing of daily maximum ∆dv values for each Class I area and year of 

meteorological data. The visibility impact threshold to identify those sources subject to 

BART is a 98th percentile change in visibility (∆dv) of 0.5 dv. Therefore, if the 8th

highest ∆dv value for any year is equal to or greater than 0.5 dv, the source is considered 

to cause or contribute to visibility impairment in the subject Class I area.

Table 9 presents the model results for each source, year, and Class I area. The 

table lists, in each case, the number of days on which the calculated ∆dv value at any 

receptor exceeded 0.5, and the largest ∆dv value calculated for any day and receptor. 

Based on the Table 9 results, the following Wyoming sources have been determined to be 

subject to BART.

Pacificorp Bridger Power Plant

Pacificorp Naughton Power Plant

FMC Granger Soda Ash Plant

FMC Green River Sodium Plant

General Chemical Green River Soda Ash Plant

Basin Electric Laramie River Power Plant

Pacificorp Dave Johnson Power Plant

Pacificorp Wyodak Power Plant

Four sources that were screened did not have results indicating a significant 

visibility impact in the Class I areas modeled. The P4 Production Rock Springs Coking 

Plant had no impacts exceeding 0.4 dv at the Bridger or Fitzpatrick WAs. The source is 

more than 200 km from any other Class I area (compared to 115 km from Bridger WA). 

Therefore it is concluded that P4 Production is not subject to BART.

Similarly, Black Hills Neil Simpson # 1 Power Plant produced only one day out 

of three years with an impact exceeding 0.5 dv at Wind Cave and Badlands NPs. The 

plant is 165 km from Wind Cave (generally upwind) and 300 km or more from all Class I 

areas in other directions. It is concluded that Neil Simpson # 1 has no significant Class I 

area visibility impacts and is not subject to BART.

Results are slightly less clear in the cases of the Sinclair Refinery and Sinclair 

Casper Refinery. Screening of these sources (for the Southeast and Northeast domains, 

respectively) indicate no impacts exceeding 0.5 dv. However, these sources are 

approximately equidistant from Class I areas in other domains, with a possibility of 

plume transport in those directions. Thus, an additional CALPUFF model run was 

executed for Sinclair; it was modeled in the Northeast domain to evaluate impacts at 

Wind Cave and Badlands NPs. The results of that analysis (included in Table 9) also 

show no impact exceeding 0.5 dv. Since total emissions from the Sinclair Casper 

Refinery are substantially less than from the Sinclair Refinery, and the latter is shown to 
23

have insignificant impacts in both the northeast and southeast domains, it is concluded 

that neither Sinclair source is subject to BART.
24

Table 9. Results of CALPUFF Visibility Modeling for BART-Eligible Sources

SW Domain 1995 1996 2001 1995 1996 2001

(Num Values >.5 DV) (Num Values >.5 DV) (Num Values >.5 DV) Largest DV Change Largest DV Change Largest DV Change

P4 Production

Bridger Wilderness 0 0 0 0.143 0.381 0.388

Fitzpatrick Wilderness 0 0 0 0.081 0.129 0.094

Pacificorp Bridger

Bridger Wilderness 55 21 42 9.717 8.666 4.617

Fitzpatrick Wilderness 25 15 23 3.337 3.764 4.327

Pacificorp Naughton

Bridger Wilderness 105 109 128 5.984 6.185 7.331

Fitzpatrick Wilderness 48 43 81 3.305 5.253 4.789

FMC - Granger

Bridger Wilderness 3 13 7 0.862 1.719 1.090

Fitzpatrick Wilderness 0 2 0 0.260 1.140 0.272

FMC - Green River

Bridger Wilderness 20 24 38 2.063 2.788 2.214

Fitzpatrick Wilderness 5 8 11 1.003 1.811 1.235

General Chemical

Bridger Wilderness 11 18 27 1.471 2.369 1.757

Fitzpatrick Wilderness 4 5 6 0.702 1.658 1.077

NE Domain 2001 2002 2003 2001 2002 2003

(Num Values >.5 DV) (Num Values >.5 DV) (Num Values >.5 DV) Largest DV Change Largest DV Change Largest DV Change

Basin Electric

Bad Lands 81 57 62 5.503 5.879 5.441

Wind Cave 73 58 62 6.273 7.709 8.518

Black Hills

Bad Lands 0 0 0 0.207 0.346 0.374

Wind Cave 0 0 1 0.234 0.425 0.700

Pacificorp Dave Johnston

Bad Lands 88 65 79 4.299 4.051 3.482

Wind Cave 91 69 77 4.460 4.678 4.326

Pacificorp Wyodak

Bad Lands 20 23 29 1.155 2.160 2.484

Wind Cave 30 28 37 1.671 2.490 3.685

Sinclair Casper

Bad Lands 0 0 0 0.075 0.089 0.091

Wind Cave 0 0 0 0.112 0.119 0.106

Sinclair Refinery

Bad Lands 0 0 0 0.196 0.166 0.132

Wind Cave 0 0 0 0.303 0.189 0.247

SE Domain 2001 2002 2003 2001 2002 2003

(Num Values >.5 DV) (Num Values >.5 DV) (Num Values >.5 DV) Largest DV Change Largest DV Change Largest DV Change

Sinclair Refinery

Rocky Mountain NP 0 0 0 0.242 0.282 0.144

Rawah Wilderness 0 0 0 0.267 0.320 0.151

Mt. Zirkel Wilderness 0 0 0 0.425 0.213 0.177
APPENDIX A

SOURCES OF METEOROLOGICAL AND 

OZONE MONITORING DATA

SOUTHWEST DOMAIN

Meteorological Data:

 1995 1996 2001

 Surface Upper Air Surface* Upper Air Surface Upper Air 

Baggs, WY Denver, CO Rock Springs, WY None Rawlins, WY Riverton, WY

Craig, CO Grand Junction, CO Riverton, WY (Vertical profiles Riverton, WY Salt Lake City, UT

Tg Soda Ash Lander, WY Lander, WY Based on data Salt Lake City, UT Grand Junction, CO

OCIW Salt Lake City, UT Big Piney, WY Generated at each Rock Springs, WY

Naughton Power Plt Evanston, WY 36 km. spaced Big Piney, WY

General Chemical Jackson Hole, WY grid cell by MM5) Casper, WY

Whitney Canyon Worland, WY Evanston, WY

Shute Creek Gas Pl Rawlins, WY Jackson Hole, WY

Pinedale, WY Ogden, UT Pocatello, ID

Centennial, WY Salt Lake City, UT Ogden, UT

Yellowstone NP Pocatello, ID

Craters of the Moon Idaho Falls, ID

Denver, CO Soda Springs, ID

Grand Junction, CO Malad City, ID

Cheyenne, WY Casper, WY

Lander, WY

Rock Springs, WY

Casper, WY

Salt Lake City, UT

Pocatello, ID

Rawlins, WY

Riverton, WY

* - 63 National Weather Service stations were input because the original modeling domain developed with the 1996 data set is substantially larger than the 

SWWYTAF domain, extending into a large part of Montana, the entire state of Wyoming and the western Dakotas; only those stations located within the 

SWWYTAF domain are listed

Precipitation Stations: total of 249 stations in original modeling domain

Ozone Monitoring Stations:

Pinedale, WY

Centennial, WY

Yellowstone NP, WY

Craters of the Moon NM, ID

Highland, UT

Hayden, CO
NORTHEAST DOMAIN

Meteorological Data: all years except where noted

 Surface Upper Air

Ellsworth AFB, SD Rapid City, SD

Chadron, NE

Lander, WY

Scottsbluff, NE

Sheridan, WY

Billings, MT

Cody, WY

Rawlins, WY

Riverton, WY

Worland, WY

Casper, WY

Rapid City, SD

Gillette, WY

Buffalo, WY – 2003 only

Precipitation Stations: total of 62 stations (63 for 2003)

Ozone Monitoring Stations:

Thunder Basin, WY

Robbinsdale, SD (except 2001)
SOUTHEAST DOMAIN

Meteorological Data: all years

 Surface Upper Air

Lamar Municipal Airport, CO Denver, CO

Pueblo Memorial Airport, CO Grand Junction, CO

Goodland, CO Rapid City, SD

Colorado Springs Municipal Airport, CO Riverton, WY

Limon, CO

Leadville Lake County Airport, CO

Meeker Airport, CO

Eagle County Airport, CO

Aspen Pitkin County Airport, CO

Gunnison County Airport, CO

Burlington Carson Airport, CO

Akron Washington Co Airport, CO

Grand Junction Walker Field, CO

Montrose Regional Airport, CO

Greeley - Weld County Airport, CO

Loveland Ft Collins – Loveland, CO

Cheyenne, WY

Laramie Regional Airport, WY

Denver International Airport, CO

Douglas Converse County Airport, WY

Casper Natrona Co International Airport, WY

Craig Craig - Moffat Cnty Airport, CO

Hayden Yampa Valley Airport, CO

Rifle Garfield County Airport, CO

Rock Springs Sweetwater Co Airport, WY

Rawlins Municipal Airport, WY

Lander Hunt Field, WY

Torrington Municipal Airport, WY

Riverton, WY

Big Piney Marbleton Airport, WY

Precipitation Stations: total of 108 stations

Ozone Monitoring Stations:

Centennial, WY

Rocky Mountain NP, CO