### BART AIR MODELING PROTOCOL

INDIVIDUAL SOURCE VISIBILITY

IMPAIRMENT ANALYSIS

March , 2006

State of Wyoming

Department of Environmental Quality

Air Quality Division

Cheyenne, WY 82002TABLE OF CONTENTS

Section Page

1.0 INTRODUCTION

................................ ................................ ................................ ............... 1

2.0 OVERVIEW

................................ ................................ ................................ ........................ 2

3.0 POLLUTANTS AND EMISSIONS

................................ ................................ .................... 4

4.0 MODELING DOMAIN AND METEOROLOGICAL DATA

................................ ......... 10

5.0 CALMET INPUT

................................ ................................ ................................ .............. 14

6.0 CALPUFF MODELING

................................ ................................ ................................ .... 16

7.0 POSTPROCESSING

................................ ................................ ................................ ......... 18

8.0 DETERMINATION OF SOURCES SUBJECT TO BART

................................ ............. 22

Tables

1 WYOM ING BART

– ELIGIBLE SOURCES

................................ ................................ ..... 3

2 MAXIMUM 24

- HR EMISSION RATES FOR BART

SOURCE ATTRIBUTION MODELING

................................ ................................ ....... 5

3 STACK PARAMETERS FOR BART SOURCE ATTRIBUTION MODELING

............. 8

4 SOURCE

- SPECIFIC MODEL DOMAINS AND METEROLOGICAL

DATA YEARS

................................ ................................ ................................ ............. 12

5 CALMET INPUT PARAMETE RS 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 AERO SOL

COMPONENTS FOR 20% BEST DAYS FOR BART ANALYSIS (μg /m 3 )

............. 211

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) Determinatio n s. ( 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 will apply air quality modeling, using the CALPUFF

modeling system, in acco rdance with the EPA Guidelines to determine the Wyoming

sources which are subject to BART. This protocol defines the specific methodology to

be used by the State. The Protocol may also be used for determining the improvement in

visibility to be achieved by potential BART controls.

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

(BART) Determinations; Final Rule. 70 Federal Register, 3 9103

- 39172, July 6, 2005.2

2.0 OVERVIEW

The Wyoming Air Quality Division has determined that there are fourteen

“BART

- Eligible” sources in the State. The sources are listed in Table 1. Modeling and

analyses described in this Protocol will be used to determine, for each of these sources,

whether they are “subject to BART”. A source will be subject to BART if air quality

modeling indicates that the source causes or contribute s 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 defined as those within 300 km of any BART

eligible source

In Wyoming: N. Absaroka WA

Was h a kie WA

Yellowstone NP

Teton WA

Fitzpatrick WA

Bridger WA

Grand Teton NP

In Colorado: Rawah WA

Rocky Mountain NP

Mt. Zir kel NP

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 NP

Not all of these Class I areas will be included in modeling analyses. For each BART

eligible source, those Class I areas deemed most likely to experience visibility impac ts on

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

domains, sources, and Class I area s are described in subsequent parts of this Protocol.

Wyoming will follow the BART guideline for evaluation of all BART

- el igible

sources. The threshold for classification of a source as subject to BART will be a

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

based on the 98 th percentile of modeled 24

- hour delta

– deciview values.3

Ta ble 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. Sources4

3.0 POLLUTANTS AND EMISSIONS

The pollutants to be included in the CALPUFF modeling analyses will be sulfur

dioxide (SO 2 ), nitrogen oxides (NO

x ), and particulate matter. Where data are available,

parti culate matter emissions will be quantified separately as fine particles (PM2.5) and

coarse particles (PM10). If no particle size information is available, all particles will be

assumed to be PM2.5. Emissions of ammonia (NH 3 ) and volatile organic compound s

(VOC) will not be 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 to be modeled for all BART

- eligible

sources. The emission rates were dete rmined 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 sou rce. The data in Tables 2 and 3 will be used for all

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

.5

Table 2. Maximum 24

- hr Emission Rates for BART Source Attribution Modeling

Source Emission Unit NO

x SO 2 P M2.5 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 10.086

Table 2. Maximum 24

- hr Emission Rates for BART Source Attribution Modeling (Continued)

Sourc e Emission Unit NO

x SO 2 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 Johns t on 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 39 8.3 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 2050.0 258.3 0 118.9 14.98 291. 1 36.68

Wyodak

Sinclair Boiler 26.7 3.36 98.2 12.37 15.6 1.97

Casper Refinery7

Table 2. Maximum 24

- hr Emission Rates for BART Source Attribution M odeling (Continued)

Source Emission Unit NO

x SO 2 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 42.848

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 16.7 8 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

OIC 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 Johns t on Boiler # 3 76.2 325.9 8.53 7.019

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

Source Emission Unit Height Temp Vel Dia

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

Pacific orp 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

Pacific orp 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

Pacific orp 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 1.5210

4.0 MODELING DOMAIN AND METEOROLOGICAL DATA

The determination of those sources subject to BART will be carried out through

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

CAL PUFF will be developed using the CALMET meteorological processor; input data

will consist of MM 5 prognostic model fields, augmented with surface and upper air data

from observing station s 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 is 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 will

utilize three separate modeling domains an d meteorological data sets.

The model domains will include 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 n ortheast

data sets have been developed for prior Wyoming analyses and can be used directly for

BART modeling. The southea st domain meteorological fields will be developed

specifically for the BART analyses. MM 5 model output for the appropriate area and

y ears have been acquired by the Division, and will be 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 to be used for each source’s BART evaluation

are shown in Table 4. The assignments in Table 4 w ere developed on the basis of

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

considering meteorological a nd terrain factors. All source

- Class I area distances exceed

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

application for CALPUFF.

Only those Class I areas t hat are most likely to be impacted by each source will be

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 will be evalua ted. 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.

P ossible exceptio n s exists in the case of the Laramie River and Dave Joh n ston

power plants

. These sources are generally upwind of the Wind Cave and Badlands Class

I areas, and therefore will be modeled in the northeast Wyoming domain. However, all

of these sources are a pproximately the same distance from northern Colorado Class I

areas as they are from Wind Cave and Badlands. Because of prevailing wind directions,11

it is unlikely that impacts in Colorado exceed those in the South Dakota areas. However,

if one or more of these sources are not subject to BART based on the Win d

Cave/Badlands modeling, it will be appropriate to remodel such sources in the southeast

Wyoming domain to confirm that they do not exceed the subject

- to

- Bart threshold at the

nearest Colorado areas.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 Northea st WY 2001, 2002, 2003 Wind Cave, Badlands

Laramie River

2. Black Hills North e a st WY 2001, 2002, 2003 Wind Cave, Badlands

Neil Simpson # 1

3. Dyno Nobel South e a st WY 2001, 2002, 2003 Rocky Mountain NP, Rawah,

Cheyenne Plant Mt. Z i rkel

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, Fitzpatr ick

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 No rth e a st WY 2001, 2002, 2003 Wind Cave, Badlands

Dave Johnston13

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. Zirkel14

5.0 CALMET INPUT

I nput options for CALMET generally applied default values except where

application

- specific choices are required. Because the CALMET meteorological

processing for the three modeling domains have been done at different times for different

applications, ther e are some minor differences in several individual inputs. None of these

are likely to cause significant differences in the final meteorological fields produced by

CALMET.

Table 5 summarizes the CALMET inputs. Where there were differences between

the C ALMET runs, a range of values is shown.

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

Wyoming) data set, which has 20 km resolution. The southwest Wyoming CALMET

processing used, in addition to the MM5 input, data from 63 surface weather stations and

249 precipitation stations. The northeast Wyoming analyses included 13 surface stations

and 62 precipitation stations. (The number of stations may vary slightly between years

due to data availability.) The southeast Wyoming analysis will use surface and

precipitation data from a number of stations comparable to what was used for the

northeast domain. The number of upper air stations used as input to the CALMET

processing varied from none (1996 only) to three, depending upon the ready 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) 8

– 10

Top of lowest layer (m) 20

Top of highest layer (m) 2980

– 3500

Input Group 4

Observation mode (NOOBS) 0 or 1

Input Group 5

Prog. Wind data (IPROG) 4 or 14

(RMAX1) 20

– 30

(RMAX2) 40

– 50

(RMAX3) N/A

Terrain influence ( TERRAD) 15

(R1) 5

(R2) 15

– 25

Input Group 6

Max mixing ht (ZI MAX) 2980

- 3500

CALMET Model Version 5.53A, Level 04071616

6.0 CALPUFF MODELING

CALPUFF modeling wi ll be 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 will be as prescribed in

Sections 3.0 and 4.0 of this Protocol. Each source will be modeled separately for each of

three years of meteorological data, utilizing the CALMET meteorological fields

generated for the applicable years/model domains.

Concentration calculations will be made for all receptors within the desi gnated

Class I areas. Receptors will be 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 will conform with standard default values with limited

exception s . Table 6 lists non

- default and application

- specific parameters that will be

used in CALPUFF. Chemical transformation calculations will use MESOPUFF II

equations, and dispersion coefficients will be PG coefficients ( MDISP=3).

Since most of the sources to be evaluated have relatively tall stacks, and only

impacts at distances greater than 50 km are of interest, building wake effects will not be

considered for any sources. Puff splitting will not be used for CALPUFF modeling, in

order to limit computation time to reasonable levels.

Background ozone concentrations will be considered in the model by use of

hourly ozone files from representative monitoring sites in each model domain. A default

ozone concentration (for missing data hours) will be specified as 44 ppb, based on

average data from northeast Wyoming. The background ammonia concentration will be

specified as 2.0 ppb for all model domains. The value of 2.0 is based on monitoring data

from nearby states and IW AQM 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 lauds, and 10.0 ppb for agricultural lauds

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

within a model domain , a value of 2.0 ppb has been 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 will be used for all modeled particles except PM10.

Since PM10 represents coarse particles with diameters between 2.5 and 10.0 μm, the

mass

- mean PM10 diameter has been estimated as 7.0 μm.17

Table 6. CALPUFF Input Parameters that are Application

- Specific or Differ F rom

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 SO 2 , SO 4 , NO

x , HNO 3 , NO 3 , PM10, PM25

Species emitted SO 2 , NO

x , 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 (hou rly 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 04071618

7.0 POSTPROCESSING

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

- hour

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

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

area.

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

nitrate, coarse particles, and fine particles). T he 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, will be used.

Ammonium sulfate 3.0

Ammonium nitrate 3.0

PM Coarse (PM10) 0.6

PM Fine (PM25) 1.0

Monthly ave rage relative humidity factors F (RH) will be used in the light

extin ction calculations to account for the hygroscopic characteristic of sulfate a nd 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 t han 0.3 units;

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

area.

CALPOST visibil ity Method 6 (MV ISBK=6) will be used for determination of

background visibility. It should be noted that when Method 6 is us e d, the CALPOST

calculation of f

(RH) and the CALPOST designation of ma ximum relative humidity

(RHMAX) are irrelevant and not used for calculations

.

The natural background conditions as a reference for determination of the delta

dv change due to a source sho uld 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 are needed for input to CALPOST.

Annual species concentrations corresponding to the 20% best days have been

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

concentrations given in Guidance for Est imating 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 a rea 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% best19

days aerosol concentration s to be used f or Wyoming BART evaluations are listed in

Table 8.

Concentratio ns 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 conce ntrations 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

Badlands Bridger, Fitzp atrick,

Grand Teton NP Rocky Mt. NP

,

Rawah, Mt. Zirkel,

Savage Run

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 2.0321

Table 8. Natural Background Concentrations of Aerosol Components for 20% Best Days for BART Analyses (μg/m 3 ).

Aerosol

Component Wind Cave

Badland 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 1.13522

8.0 DETERMINATION OF SOURCES SUBJECT TO BART

Results of the CALPOST visibility processing for a BART

- eligible source will b e 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 98 th

percentile change in visibility (∆dv) of 0.5 dv. Therefore, if the 8 th high est ∆dv value is

equal to or greater than 0.5 dv, the source will be considered to cause or contribute to

visibility impairment in the subject Class I area.

The highest model

- predicted daily ∆dv values for each Class I area and year will

be ranked. If t he 8 th highest value for each of the three years at each Class I area in a

given model domain is less than 0.5 dv, the source will have been demonstrated to have

insignificant visibility impacts and will not be subject to BART. If the 8 th high for any

yea r or Class I area equals or exceeds 0.5 dv, the source will be subject to BART.