Appendix B 

ALCOA BART MODELING REPORT

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Appendix L.8 - 107

January 18, 2008
Site-Specific Modeling for BART 

Analysis at Alcoa Inc. – Tennessee 

Operations’ South Plant, Blount 

County, Tennessee 

February 2007 

Prepared For: 

Alcoa Inc. -Tennessee Operations 

Blount County, Tennessee 

Prepared By: 

TRC Environmental Corporation 

Wannalancit Mills 

650 Suffolk Street 

Lowell, Massachusetts 01854 

(978) 970-5600 

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Appendix L.8 - 108

January 18, 2008
i 

TABLE OF CONTENTS 

Page 

LIST OF FIGURES II

1. INTRODUCTION 1-1

2. SOURCE DESCRIPTION 2-1

2.1 Initial (base case) run 2-1

2.2 Control scenario 2-8

3. GEOPHYSICAL AND METEOROLOGICAL DATA 3-1

3.1 Terrain 3-1

3.2 Land Use 3-2

3.3 Meteorological Data Base 3-6

4. AIR QUALITY MODELING METHODOLOGY 4-1

4.1 Model Selection 4-1

4.1.1 Major Features of CALMET 4-2

4.1.2 Major Features of CALPUFF 4-4

4.2 Modeling Domain 4-9

4.3 Meteorological Modeling Options 4-9

4.4 Dispersion Modeling Options 4-9

4.5 Visibility Calculations 4-11

5. RESULTS 5-1

6. REFERENCES 6-1

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Appendix L.8 - 109

January 18, 2008
ii 

LIST OF FIGURES 

 Page 

Figure 2-1. Aerial photo of the facility with the potrooms and point sources underlined in red. 2-2

Figure 2-2. Aloca South Plant layout in plant coordinates. 2-3

Figure 3-1 Terrain contour (m MSL) at 4 km resolution (VISTAS CALMET Domain 3) use for the 

screening run. 3-3

Figure 3-2 Terrain contour (m MSL) at 1 km resolution on the 334 km x 259 km CALMET and 

CALPUFF model domains. 3-4

Figure 3-3. Dominant Land Use categories at 1 km resolution on the 334 km x 259 km CALMET and 

CALPUFF model domains. 3-5

Figure 3-4 Surface, upper air, MM5 and precipitation stations to be used in the 2001 modeling.. 3-12

Figure 3-5 Surface, upper air, MM5 and precipitation stations to be used in the 2002 modeling.. 3-13

Figure 3-6 Surface, upper air, MM5 and precipitation stations to be used in the 2003 modeling. 3-14

Figure 3-7 Ozone stations, both CASTNet and AIRS used in the 2001 modeling. 3-17

Figure 3-8 Ozone stations, both CASTNet and AIRS used in the 2002 modeling. 3-18

Figure 3-9 Ozone stations, both CASTNet and AIRS used in the 2003 modeling. 3-19

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Appendix L.8 - 110

January 18, 2008
iii 

LIST OF TABLES

 Page 

Table 2-1. Line Sources and Parameters used in CALPUFF 2-4

Table 2-2. Point Sources and Parameters used in CALPUFF 2-5

Table 2-3. Point and Line Source Emissions. 2-6

Table 2-4. PM10 Speciation Assumptions. 2-7

Table 2-5. Point Sources Added in the Wet Scrubber Scenario to Replace P01 to P04 2-9

Table 2-6. Point Source P15 (SO2 Control Source) Emission Rate. 2-9

Table 3-1. U.S. Geological Survey Land Use and Land Cover Classification System 3-7

Table 3-2. Default CALMET Land Use Categories and Associated Geophysical Parameters Based on the 

U.S. Geological Survey Land Use Classification System (14-Category System) 3-8

Table 3-3. Meteorological data sources and parameters available 3-9

Table 3-4. NWS hourly surface stations for 2001, 2002 and 2003. 3-10

Table 3-5. Upper air stations used for 2001, 2002 and 2003. 3-10

Table 3-6. Hourly NWS precipitation stations for 2001, 2002 and 2003. 3-11

Table 3-7. Ozone stations for 2001, 2002 and 2003. 3-16

Table 4-1. Major features of the CALMET meteorological model 4-3

Table 4-2. Major Features of the CALPUFF Model. 4-7

Table 4-3. Summary of Natural Background for Soil 4-14

Table 4-4. Monthly Site-Specific f(RH) values based on the Centroid of the Area, for Visibility Method 6 

application 4-14

Table 5-1. Results for visibility impact using Method 6 – Base case run - year 2001 5-3

Table 5-2. Results for visibility impact using Method 6 –Base case run - year 2002 5-4

Table 5-3. Results for visibility impact using Method 6 –Base case run - year 2003 5-5

Table 5-4. Results for visibility impact using Method 8 –Base case run - year 2001 5-6

Table 5-5. Results for visibility impact using Method 8 –Base case run - year 2002 5-7

Table 5-6. Results for visibility impact using Method 8 –Base case run - year 2003 5-8

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Appendix L.8 - 111

January 18, 2008
iv 

Table 5-7. Results for visibility impact using Method 6 – Wet scrubber scenario - year 2001 5-9

Table 5-8. Results for visibility impact using Method 6 – Wet scrubber scenario - year 2002 5-9

Table 5-9. Results for visibility impact using Method 6 – Wet scrubber scenario - year 2003 5-9

Table 5-10. Results for visibility impact using Method 8 – Wet scrubber scenario - year 2001 5-10

Table 5-11. Results for visibility impact using Method 8 – Wet scrubber scenario - year 2002 5-10

Table 5-12. Results for visibility impact using Method 8 – Wet scrubber scenario - year 2003 5-10

Table 5-13. Summary Table of Compliance at the 98th percentile change in light extinction for Initial 

Runs 5-11

Table 5-14. Summary Table of Compliance at the 98th percentile change in light extinction for the control 

scenario 5-11

Table 5-15. Base case run – Source group and species contributions at the 8th Highest light extinction 

change for Great Smoky Mountains National Park using CALPOST Method 6 5-12

Table 5-16. Base case run – Source group and species contributions at the 8th Highest light extinction 

change for Great Smoky Mountains National Park using CALPOST Method 8 5-13

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Appendix L.8 - 112

January 18, 2008
Introduction 1-1 

1. INTRODUCTION 

TRC Environmental Corporation has conducted site-specific BART (Best Available 

Retrofit Technology) modeling for Alcoa Inc. – Tennessee Operations’ South Plant. 

This facility is situated in Blount County, Tennessee in Alcoa City north of Maryville 

west of the Appalachian Mountains not far from the Tennessee/North Carolina 

border. The Alcoa South Plant facility is a primary aluminum smelter and secondary 

aluminum production facility. 

On July 6, 2005 the US Environment Protection Agency produced the Federal 

Register document, 40 CFR Part 51 in order to introduce new National Regional 

Haze Regulations for Best Available Retrofit Technology. The regional haze rule 

requires States to submit implementation plans (SIPs) to address regional haze 

visibility impairment in 156 Federally-protected parks and wilderness areas, 

commonly referred to as “Class 1 Areas”. The final rule included a requirement for 

BART for certain large stationary sources that were put in place between 1962 and 

1977. The regional haze rule uses the term “BART-eligible source” to describe those 

sources which have the potential to emit 250 tons or more of a visibility-impairing air 

pollutant, were put in place between August 7, 1962 and August 7 1977 and whose 

operations fall within one or more of 26 specifically listed source categories, of 

which Primary Aluminum Ore Reduction Plants are one. 

BART review is required when the source emits any air pollutant which may 

reasonably be anticipated to cause or contribute to any impairment of visibility in any 

Class 1 area. In identifying a level of control of BART, States are required by 

section 169A(g) of the CAA to consider; (a) the costs of compliance, (b) the energy 

and non-air quality environmental impacts of compliance, (c) any existing pollution 

control technology in use at the source, (d) the remaining useful life of the source and 

(e) the degree of visibility improvement which may reasonably be anticipated from 

the use of BART. 

The purpose of the modeling is to assess the ambient air quality impacts of sulfur 

dioxide (SO2), particulate matter (PM) and nitrogen oxides (NOx) emissions and 

compare the impacts to Significant Impact Levels (SILs) at all the Class I areas located 

within a radius of 300 km of the facility. A total of six Class I areas are located within 

this radius: Mammoth Cave National Park, Great Smoky Mountains National Park, 

Linville Gorge Wilderness Area, Shining Rock Wilderness Area, Cohutta Wilderness 

Area and Joyce-Kilmer/ Slickrock Wilderness Area. A screening run on a 4-km 

resolution domain has determined that there will be no exceedances of a 0.5 deciview 

screening threshold at the most distant Class I area (Mammoth Cave National Park), so 

this Class I area is not subject to further analysis. A set of refined modeling 

simulations on a high resolution (1-km) grid is conducted in this report to evaluate 

impacts at the five remaining Class I areas. 

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Appendix L.8 - 113

January 18, 2008
Introduction 1-2 

The topography of the screening domain area consisted of gentle rolling terrain on its 

west side where elevation of the land ranges from ~120m in the southwest to ~ 300m 

in the north. A much higher elevation terrain crosses the domain from the northeast 

corner to the center southern portion of the domain. This is the southern part of the 

Appalachian Mountains, whose peaks can reach 2000 meters. The refined domain is 

a zoom on the southern part of the Appalachian Mountains including the highest 

complex terrain areas. As a result, there is a strong potential for terrain effects, both 

on the meteorological fields and in terms of plume-terrain interaction effects. A nonsteady-state modeling approach is useful in this assessment to properly evaluate the 

air quality impacts of the facilty’s sources. The CALMET and CALPUFF nonsteady-state models (Scire et al., 2000a,b) are used in the modeling analysis. The 

U.S. Environmental Protection Agency (USEPA) has promulgated the CALPUFF 

modeling system as a Guideline Model for Class I impact assessments and other long 

range transport applications or near field applications involving complex flows 

(USEPA, 2000), and the model is recommended by both the Federal Land Managers 

Air Quality Workgroup (FLAG, 2000) and the Interagency Workgroup on Air 

Quality Modeling (IWAQM, 1998). CALPUFF is specifically recommended by the 

USEPA for BART analyses (Federal Register, 6 July 2005). 

CALMET is a diagnostic meteorological model that produces three-dimensional 

wind fields based on parameterized treatments of terrain effects such as slope flows 

and terrain blocking effects. Meteorological observations are used to determine the 

wind field in areas where the observations are representative. Hourly meteorological 

data produced by the Mesoscale Model, Version 5 (MM5) on a 12 km grid are used 

in CALMET for 2001 and 2002 to define the initial guess wind fields before 

CALMET’s terrain adjustments is computed. For 2003, MM5 fields produced on a 

36 km grid are used for the initial guess fields. The CALMET simulations, on a 4-

km grid resolution domain (Domain 3) prepared for VISTAS was used in the 

screening analysis. Because of the proximity of the Alcoa facility to the Great 

Smoky Mountains National Park and the expected terrain influences, a refined 

simulation on a 1-km grid, is used to better resolve the terrain effects on the wind and 

pollutant dispersion. 

CALPUFF is a non-steady-state puff dispersion model. It accounts for spatial 

changes in the CALMET-produced meteorological fields, variability in surface 

conditions (elevation, surface roughness, vegetation type, etc.), chemical 

transformation, wet removal due to rain and snow, dry deposition, and terrain 

influences on plume interaction with the surface. CALPUFF contains a module to 

compute visibility effects, based on a humidity-dependent relationship between 

particulate matter concentrations and light extinction, as well as wet and dry acid 

deposition fluxes. The screening and refined meteorological and dispersion modeling 

simulations were conducted for a three-year period (2001, 2002 and 2003). SO2, PM, 

and NOx, emissions and their secondary products resulting from chemical 

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Appendix L.8 - 114

January 18, 2008
Introduction 1-3 

conversions from the Alcoa facility are modeled at receptors in the Class I areas and 

their impacts on visibility are evaluated. 

This report outlines the techniques and data sources used in the BART analyses. The 

screening modeling was conducted in accordance with the procedures outlined in the 

VISTAS modeling protocol, and the 4-km VISTAS Domain 3 was used, even though 

the proximity of the facility to the closest Class I area. The refined analysis is based 

on the use of a more detailed terrain using procedures described in this site-specific 

protocol. In Section 2, a general description of the study area and the source 

configuration is provided. Descriptions of the site characteristics and the data bases 

(meteorological, geophysical, and aerometric) used in the analysis are provided in 

Section 3. Section 4 includes an overview of the CALMET and CALPUFF models, 

and the parameters used in the analysis. The results are summarized in Section 5. 

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Appendix L.8 - 115

January 18, 2008
Source Description 2-1

2. SOURCE DESCRIPTION 

2.1 Initial (base case) run 

The Alcoa South Plant facility is a primary aluminum smelter and secondary 

aluminum production facility located in Blount County, Tennessee west of the 

Appalachian Mountains not far from the Tennessee/North Carolina border. 

A BART applicability analysis was completed for the facility to determine those 

sources subject to the BART controls. The BART-eligible sources include two 

potlines (4 potrooms), an anode bake furnace, an aluminum scrap crusher, a 

delacquering furnace, and 2 aluminum scrap melting furnaces. Figure 2-1 displays 

an aerial photo of the facility with the potrooms and point sources subject to BART 

outlined. 

Since the Facility is located less than 50 km away from the Great Smoky Mountains 

National Park Class I area, downwash is applied. The building parameters were 

computed in a previous study dated December 1999. The building downwash 

parameters for the Aluminum Reclamation Crusher has been recomputed in this 

application, since this stack was not modeled in the previous study. It emits PM 

only. Figure 2-2 displays in plant coordinates the location of the buildings, potrooms 

and stacks. In this figure, true north is 7 degrees east of plant north shown on the 

figure. 

Table 2-1 lists the line source parameters while Table 2-2 shows the source 

parameters for the point sources. Table 2-3 summarizes the line and point source 

emission rates for the modeled pollutants and Table 2-4 summarizes the particulate 

speciation for all the sources. Note that coarse particulates are defined as particulates 

in the size range of 10 microns to 2.5 microns while fine particulates are equal to or 

less than 2.5 microns (i.e. PM2.5 ). The particulate matters provided are already in 

three categories: PM10-PM2.5, solid PM2.5 and organic condensable. For modeling 

purposes, particulate matter is divided into six size categories: PM800 (6-10μm), 

PM425 (2.5-6μm), PM187 (2.5-1.24μm), PM112 (1-1.24μm), PM081 (0.62-1μm) 

and PM056 (0.5-0.62μm). PM10 provided is partitioned the following way: 

1- PM10-PM2.5 is half in PM800 and half in PM425 and then added to form 

PMC – Coarse particulate matter has an extinction efficiency of 0.6. 

2- Solid PM2.5 is half in PM081 and half in PM056 and then added to form 

SOIL – Fine particulate matter has an extinction efficiency of 1.0. 

3- Organic Condensable is separated half in PM081 and half in PM056 and then 

added to form Secondary Organic Aerosol (SOA) – SOA has an extinction 

efficiency of 4.0. 

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Appendix L.8 - 116

January 18, 2008
Source Description 2-2

Figure 2-1. Aerial photo of the facility with the potrooms and point sources in Geographic 

Coordinates. 

-83.985 -83.98 -83.975 -83.97 -83.965 -83.96

Longitude (in degree)

35.77

35.775

35.78

Latitude (in degree)

ALCOA South Plant in Blount County, Alcoa city north of Maryville

Geographic Projection, units: degree (dd)

Datum: NAD83

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Appendix L.8 - 117

January 18, 2008
Source Description 2-3

Figure 2-2. Alcoa South Plant layout in plant coordinates – North represents the plant north. 

True north is 7 degrees east of plant north. 

-400 -200 0 200

Y-East Plant Coordinates (in meters)

-600

-400

-200

0

200

400

600

800

1000

X-North Plant Coordinates (in meters)

Building locations and BART point sources locations 

in Plant Coordinate

Anode Bake Furnace

Aluminum Scrap Crusher Delacquering Furnace

Aluminum scrap 

Melting Furnaces

2 Lines (4 potrooms)

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Appendix L.8 - 118

January 18, 2008
Source Description 2-4

Table 2-1. Line Sources and Parameters used in CALPUFF

Source 

ID 

Emission 

Unit ID # Stack Name 

Release 

Height 

(m) 

Monitor 

Width 

(m) 

Exit 

Velocity 

(m/s) 

Delta T (Exit 

T – Tair) 

(oK) 

Begin 

UTM 

E/N (km) 

Ending 

UTM 

E/N (km) 

L01 TNPOT0045b_1 Potline#1 Room 1 18.57 3.05 1.34 22.5 231.5522, 

3963.2083 

231.5770, 

3962.7618 

L02 TNPOT0045b_2 Potline#1 Room 2 18.57 3.05 1.34 22.5 231.5006, 

3963.2057 

231.5257, 

3962.7594 

L03 TNPOTL2RM_3 Potline#2 Room 3 18.57 3.05 1.34 22.5 231.4504, 

3963.2030 

231.4755, 

3962.7564 

L04 TNPOTL2RM_4 Potline#2 Room 4 18.57 3.05 1.34 22.5 231.3988, 

3963.2006 

231.4239, 

3962.7534 

Notes: L01-L04: F’ = 761.6 m4/s3; Ave. line source width = 3.05m; Ave. building dimension = 480.67m; H = 18.57m, W = 22.65m; Ave. building separation 

The Release height (m), Monitor width (m), Exit Velocity (m/s) and Exit Temperature (oK) are all taken from the 1999 ALCOA Tennessee study The coordinates are displayed in UTM17 NAD27 datum taken from “Stacks_Model_TNBART_Oct2005_rev1.xls” and in Lambert conformal pr

parallel 33N, 45N, origin: 40N, 97W (projection of CALMET/CALPUFF run). They show a slight shift from the aerial photo, but are kepis not adequate to digitalize all individual stacks. 

Notes 1. Source information from “Stacks_Model_TNBART_Oct2005_rev1.xls” transmitted in the email from Mike Palazzolo to Joe Scire date2 L01-L04: Average Line Source Buoyancy Parameter (F') Calculation

F' = [gLW

mw(Ts-Ta)]/Ts = 761.6 m4/s3 where 

g = acceleration of gravity = 9.81 m/s2 

L = line source length = 480.67 m Wm = line source width = 3.05 m 

w = line source exit velocity = 1.34 m/s Ts = line source exit temperature = oK 

Ta = ambient air temperature = oK 

Ts - Ta = 

ΔT = 22.5 oK 

Pre-Hearing DraftRegional Haze SIP for TN Class I Areas
Source Description 2-5

Table 2-2. Point Sources and Parameters used in CALPUFF. 

Index Emission 

Unit ID # 

Stack Name Stack 

Height 

(m) 

Stack 

 Diameter 

(m) 

Exit 

Velocity 

(m/s) 

Exit 

Temp 

(oK) 

UTM 

Easting 

 (km) 

UT

North

 (km

P01 TNPOTL0045a_N A398 Line 1 North 15.96 3.82 20.40 382.8 231.536 3963P02 TNPOTP0045a_S A398 Line 1 South 15.96 3.82 20.40 382.8 231.539 3962P03 TNPOTL0048_N A398 Line 2 North 22.60 4.88 10.32 377.5 231.433 3963P04 TNPOTL0048_S A398 Line 2 South 22.60 4.88 10.46 373.5 231.441 3962P05 TNANOD0008_1 Bake Stack #1 22.15 1.22 11.46 347.0 231.421 3962P06 TNANOD0008_2 Bake Stack #2 22.15 1.22 11.46 347.0 231.421 3962P07 TNANOD0008_3 Bake Stack #3 22.15 1.22 11.46 347.0 231.422 3962P08 TNANOD0008_4 Bake Stack #4 22.15 1.22 11.46 347.0 231.422 3962P09 TNANOD0008_5 Bake Stack #5 22.15 1.22 11.46 347.0 231.423 3962P10 TNANOD0008_6 Bake Stack #6 22.15 1.22 11.46 347.0 231.423 3962P11 TNCRSH0208 Aluminum Reclamation 

Crusher 

18.29 1.22 12.62 295.4 231.300 3963

P12 TNDFRN0201 Aluminum Reclamation 

Delacquering Furnace #1 

22.86 1.45 16.10 1155.4 231.315 3963

P13 TNMFRN0203 Aluminum Reclamation 

Melting Furnace #1 

20.73 1.92 10.46 524.3 231.316 3963

P14 TNMFRN0204 Aluminum Reclamation 

Melting Furnace #2 

20.73 1.83 18.11 711.5 231.282 3963

Note: UTM 17 Coordinates correspond to a datum of NAD27; LCC coordinates are in datum NWS-84. Note 2: Exit velocity for Aluminum Reclamation Delacquering Furnace has been updated to 16.10 m/s according to new spreadsheet “Stacks_Model_TN received by Joe Scire on October 24, 2006. 

Pre-Hearing DraftRegional Haze SIP for TN Class I Areas
Source Description 2-6

Table 2-3. Point and Line Source Emissions. 

Source 

ID 

Emission 

Unit ID # Stack Name 

PM10-

PM2.5 

g/s 

Solid 

PM2.5

g/s 

Org. Condensables 

g/s 

SO2

g/s 

NOx 

g/s 

L01 TNPOT0045b_1 Potline#1 Room 1 0.825 1.163 1.110 0.457 0.002 L02 TNPOT0045b_2 Potline#1 Room 2 0.825 1.163 1.100 0.457 0.002 L03 TNPOTL2RM_3 Potline#2 Room 3 0.722 1.018 0.972 0.457 0.001 L04 TNPOTL2RM_4 Potline#2 Room 4 0.722 1.018 0.972 0.457 0.001 

P01 TNPOTL0045a_N A398 Line 1 North 0.024 0.013 0.200 30.0 0.163 P02 TNPOTP0045a_S A398 Line 1 South 0.024 0.013 0.200 30.0 0.163 P03 TNPOTL0048_N A398 Line 2 North 0.090 0.048 0.745 30.0 0.087 P04 TNPOTL0048_S A398 Line 2 South 0.090 0.048 0.745 30.0 0.087 P05 TNANOD0008_1 Bake Stack #1 0.008 0.005 0.047 3.11 0.399 P06 TNANOD0008_2 Bake Stack #2 0.008 0.005 0.047 3.11 0.399 P07 TNANOD0008_3 Bake Stack #3 0.008 0.005 0.047 3.11 0.399 P08 TNANOD0008_4 Bake Stack #4 0.008 0.005 0.047 3.11 0.399 P09 TNANOD0008_5 Bake Stack #5 0.008 0.005 0.047 3.11 0.399 P10 TNANOD0008_6 Bake Stack #6 0.008 0.005 0.047 3.11 0.399 P11 TNCRSH0208 Aluminum Reclamation Crusher 0.097 0 0 0 0 P12 TNDFRN0201 

Aluminum Reclamation 

Delacquering Furnace #1 

0.045 0.027 0.001 0.087 1.358 

P13 TNMFRN0203 

Aluminum Reclamation 

Melting Furnace #1 

0.128 0.076 0.002 0.003 0.214 

P14 TNMFRN0204 

Aluminum Reclamation 

Melting Furnace #2 

0.137 0.081 0.002 0.004 0.228 

Note: Emission rates from Excel Spreadsheet “Stacks_model_TNBART_December2006R1.xls” sent to Joe Scire on December 21, 2006 

Pre-Hearing DraftRegional Haze SIP for TN Class I Areas
Source Description 2-7

Table 2-4. PM10 Speciation Assumptions. 

Coarse Filterable PM Fine Filterable PM Condensabl

Source 

ID 

Coarse 

Filterable 

PM 

Fine 

Filterable 

PM 

Condensable 

PM 

Total 

(Filterable 

+Cond) PM 

6-10 μm 2.5-6 μm 1.25- 2.5μm 1.00- 1.25μm 0.625- 1.00μm 0.500- 0.625μm 0.625- 1.00μm 0

0.6

(g/s) (g/s) (g/s) (g/s) (g/s) (g/s) (g/s) (g/s) (g/s) (g/s) (g/s) 

L01 0.825 1.163 1.110 3.098 0.4125 0.4125 0 0 0.5815 0.5815 0.555 0L02 0.825 1.163 1.110 3.098 0.4125 0.4125 0 0 0.5815 0.5815 0.555 0L03 0.722 1.018 0.972 2.712 0.361 0.361 0 0 0.509 0.509 0.486 0L04 0.722 1.018 0.972 2.712 0.361 0.361 0 0 0.509 0.509 0.486 0

P01 0.024 0.013 0.200 0.237 0.012 0.012 0 0 0.0065 0.0065 0.100 0P02 0.024 0.013 0.200 0.237 0.012 0.012 0 0 0.0065 0.0065 0.100 0P03 0.090 0.048 0.745 0.883 0.045 0.045 0 0 0.024 0.024 0.3725 0P04 0.090 0.048 0.745 0.883 0.045 0.045 0 0 0.024 0.024 0.3725 0P05 0.008 0.005 0.047 0.06 0.004 0.004 0 0 0.0025 0.0025 0.0235 0P06 0.008 0.005 0.047 0.06 0.004 0.004 0 0 0.0025 0.0025 0.0235 0P07 0.008 0.005 0.047 0.06 0.004 0.004 0 0 0.0025 0.0025 0.0235 0P08 0.008 0.005 0.047 0.06 0.004 0.004 0 0 0.0025 0.0025 0.0235 0P09 0.008 0.005 0.047 0.06 0.004 0.004 0 0 0.0025 0.0025 0.0235 0P10 0.008 0.005 0.047 0.06 0.004 0.004 0 0 0.0025 0.0025 0.0235 0P11 0.097 0 0 0.097 0.0485 0.0485 0 0 0 0 0 P12 0.045 0.027 0.001 0.073 0.0225 0.0225 0 0 0.0135 0.0135 0.0005 0P13 0.128 0.076 0.002 0.206 0.064 0.064 0 0 0.038 0.038 0.001 0P14 0.137 0.081 0.002 0.220 0.0685 0.0685 0 0 0.0405 0.0405 0.001 0

Note: Emission rates from Excel Spreadsheet “Stacks_model_TNBART_December2006R1.xls” sent to Joe Scire on December 21, 2006 

Pre-Hearing DraftRegional Haze SIP for TN Class I Areas
Source Description 2-8

2.2 Control scenario 

A control scenario is evaluated in this analysis for the Class I areas showing an exceedance 

of the light extinction exemption threshold of 0.5 deciviews in the initial run. The control 

run uses wet scrubbers. The four A398 stacks are replaced by one P15 stack (see Tables 2-

5 and 2-6) which has wet scrubbers for SO2 control. Particulate matter is treated in a similar 

way as in the initial run. 

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Source Description 2-9

Table 2-5. Point Sources Added in the Wet Scrubber Scenario to Replace P01 to P04, the Four A398 Stacks. 

Index Emission 

Unit ID # 

Stack Name Stack 

Height (m) 

Stack 

 Diameter (m) 

Exit Velocity 

(m/s) 

Exit 

Temp 

(oK) 

UTM 

Easting 

 (km) 

UT

North

 (km

P15 TNSO2 SO2 Control Device 45.72 7.64 16.79 309.0 231.485 3963

UTM 17 Coordinates correspond to a datum of NAD27; LCC coordinates are in datum NWS-84. Note: Stacks parameters from Excel Spreadsheet “Stacks_model_TNBART_December2006R1.xls” sent to Joe Scire on December 21, 2006 

Table 2-6. Point Source P15 Emission Rates (SO2 Control Point Source for the Wet Scrubber Scenario). 

Source 

ID 

Emission 

Unit ID # Stack Name 

PM10-

PM2.5

g/s 

Solid 

PM2.5

g/s 

Org. Condensables 

g/s 

SO2

g/s 

NOx 

g/s 

P15 TNSO2 SO2 Control Device 0.00 14.6 0.00 6.00 0.5 

Note: Emission rates from Excel Spreadsheet “Stacks_model_TNBART_December2006R1.xls” sent to Joe Scire on December 21, 2006 

Pre-Hearing DraftRegional Haze SIP for TN Class I Areas
Geophysical and Meteorological Data 3-1 

3. GEOPHYSICAL AND METEOROLOGICAL DATA 

Screening runs were performed for 2001-2003 using the VISTAS 4-km resolution 

CALMET Domain 3. Six Class I areas, Great Smoky Mountains National Park, Cohutta 

Wilderness, Joyce Kilmer/ Slickrock Wilderness, Linville Gorge Wilderness, Shining Rock 

Wilderness and Mammoth Cave National Park, are located within the 300-km radius around 

the facility as it is displayed on Figure 3-1. The red outline represents the VISTAS 4-km 

CALMET domain, the black circle is the 300-km limit around the South Plant facility 

showing the Class I areas to include in the screening analysis, the purple outline represents 

the CALPUFF computation domain. The results of the screening run show that Mammoth 

Cave National Park does not have any exceedances of the 0.5 dv screening threshold. The 

highest impacts at Mammoth Cave using the VISTAS visibility procedures (Method 6, 

annual average natural background) were 0.17, 0.30 and 0.35 dv for 2001-2003, 

respectively. As a result, Mammoth Cave is not subject to further analysis. The highest 

impact at the other Class I areas exceeded the 0.5 dv threshold, so these five Class I areas 

are included in the refined modeling analysis. 

Since the South Plant facility distance to the closest receptors in the Great Smoky 

Mountains National Park is less than 30 km and because of the complexity of the terrain in 

this area, a refined run with higher grid resolution is performed as described hereafter. The 

refined run includes the five remaining Class I areas while Mammoth Cave National Park is 

excluded. 

3.1 Terrain 

Gridded terrain elevations for the refined modeling domain are derived from 3 arc-second

digital elevation models (DEMs) produced by the United States Geological Survey (USGS). 

Data are provided in files covering 1 degree by 1 degree blocks of latitude and longitude. 

The 1-degree DEMs are produced by the Defense Mapping Agency using cartographic and 

photographic sources. USGS 1:250,000 scale topographic maps are the primary source of 

1-degree DEMs. 

One degree DEM data consists of an array of 1201 by 1201 elevations referenced on the 

geographic (latitude/longitude) coordinate system of the World Geodetic System 1972 

Datum. Elevations are in meters relative to mean sea level, and the spacing of the 

elevations along each profile is 3 arc-seconds, which corresponds to a spacing of 

approximately 90 meters. 

The CALMET computational domain for the refined run is a 1-km resolution domain 

covering part of Tennessee and North Carolina. This domain covers an area of 334 km by 

259 km (Figure 3-2) which includes the five Class I areas discussed earlier and the South 

Plant facility with a buffer zone of 50 km on each side of the domain. The terrain is rather 

complex with the southern part of the Appalachian Mountains range crossing the domain 

from northeast to southwest. Several valley can be described and the highest peaks can 

reach 2000 meters. Figure 3-2 shows contours of the terrain averaged to 1 km. The USGS 

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Appendix L.8 - 125

January 18, 2008
Geophysical and Meteorological Data 3-2 

elevation records located within each grid cell in the computational domain are averaged to 

produce a mean elevation at each grid point. Adequate representation of the important 

terrain features and valleys associated with the Class I area and the surrounding area are 

captured by the 334 x 259 grid cells, a workable number of cells. The CALPUFF 

computational domain is the same as the CALMET domain. The CALMET and CALPUFF 

domain extends beyond the Class I areas in order to provide an adequate buffer zone at the 

boundaries, and to allow the effects of flow curvature and possible small-scale recirculation 

to be evaluated. 

3.2 Land Use 

The USGS land use data in the vicinity of the facility is used to produce a gridded field of 

dominant land use categories. The land use data used in the analysis are the Composite 

Theme Grid (CTG) land use data from the USGS, at a resolution of 200 m. 

Land use data are processed to produce a 1 km resolution gridded field of fractional land 

use categories. The 37 USGS land use categories are then mapped into 14 CALMET land 

use categories. Surface properties such as albedo, Bowen ratio, roughness length, and leaf 

area index are computed proportionally to the fractional land use. The USGS land use 

categories are described in Table 3-1. Table 3-2 displays the 14 CALMET land use 

categories and their associated geophysical parameters. Figure 3-3 show the dominant land 

use categories used in the modeling. 

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Appendix L.8 - 126

January 18, 2008
Geophysical and Meteorological Data 3-3 

Figure 3-1. Terrain contours (m MSL) at 4 km resolution (VISTAS CALMET Domain 3) use for the screening 

run. The 12 Class I areas located in the domain are shown. The six Class I areas within the black 

circle (300-km radius around South Plant facility) are used in the screening run. The purple line 

delimits the CALPUFF computational domain for the screening run. 

600 700 800 900 1000 1100 1200 1300 1400 1500 1600

LCC East (km)

-600

-500

-400

-300

-200

-100

0

100

LCC North (km)

 33.N

 35.N

 37.N

 39.N

-1

100

300

500

700

900

1100

1300

1500

1700

1900

2100

2300

2500

2700

2900

3100

3300

3500

3700

3900

4500

Terrain (m)

Cohutta W

Dolly Sods W

Great Smoky Mountains NP

James River Face W

Joyce-Kilmer-SlickRock W

Linville Gorge W

South Plant

Mammoth Cave NP

Mingo W

Otter Creek W

Shenandoah NP

Shining Rock W

Sipsey W

1

2

1 - CALMET VISTAS domain 3

2 - CALPUFF computational domain

LCC Origin: 40.00N, 97.00W

Datum: NWS-84

Matching Parallels: 33.00N, 45.00N

VISTAS 4-km resolution CALMET DOMAIN 3 

including all 12 Class I areas on the Domain

Class I areas

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Appendix L.8 - 127

January 18, 2008
Geophysical and Meteorological Data 3-4 

Figure 3-2. Terrain contours (m MSL) at 1 km resolution on the 334 km x 259 km CALMET and CALPUFF 

model domains. The five Class I areas to be modeled in the refined run and the facility are also 

shown. 

1100 1150 1200 1250 1300 1350 1400

LCC East (km)

-500

-450

-400

-350

-300

LCC North (km)

 35.N

 36.N

.

.

. .

LCC Origin: 40N, 97W

Datum: NWS-84

Matching Parallels: 33N, 45N

False Easting: 0

False Northing: 0

-1

100

300

500

700

900

1100

1300

1500

1700

1900

2100

2300

2500

2700

2900

3100

3300

3500

3700

3900

4500

Terrain of the refined Domain with 5 Class I areas included

1km resolution domain - 334 x 259 cells

South Plant

Cohutta W

Joyce Kilmer-Slickrock

Shining Rock W

Linville Gorge W

Great Smoky Mountains NP

TN

KY

NC

SC

GA

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Appendix L.8 - 128

January 18, 2008
Geophysical and Meteorological Data 3-5 

Figure 3-3. Dominant land use categories at 1 km resolution on the 334 km x 259 km CALMET and 

CALPUFF model domains. The five Class I areas to be modeled in the refined run and the facility 

are also shown. 

1100 1150 1200 1250 1300 1350 1400

LCC East (km)

-500

-450

-400

-350

-300

LCC North (km)

 35.N

 36.N

.

.

. .

LCC Origin: 40N, 97W

Datum: NWS-84

Matching Parallels: 33N, 45N

LandUse categories of the refined Domain with 5 Class I areas included

1km resolution domain - 334 x 259 cells

South Plant

Cohutta W

Joyce Kilmer-Slickrock

Shining Rock W

Linville Gorge W

Great Smoky Mountains NP

Snow/Ice

Tundra

Barren

Wetland

Water

Forest

Range

Agriculture

Urban/Built-Up

TN

KY

NC

SC

GA

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Appendix L.8 - 129

January 18, 2008
Geophysical and Meteorological Data 3-6 

3.3 Meteorological Data Base 

The wind fields in the modeling domain are expected to be variable. Depending on the 

location, some of the observational data is only representative of a small area around itself. 

The local terrain is expected to influence the local flow, much of the structure in the wind 

fields is determined by CALMET using its diagnostic wind field module, rather than being 

driven by observations. 

The CALMET model requires meteorological information from the surface and upper air as 

well as geophysical information about the land use and terrain heights. Specifically, 

CALMET requires surface observations of wind speed, wind direction, temperature, cloud 

cover, ceiling height, surface pressure, relative humidity, and precipitation type (e.g., snow, 

rain, etc.). These variables are routinely measured at the National Weather Service (NWS) 

surface stations. The upper air data includes twice-daily observations of vertical profiles of 

wind speed, wind direction, temperature, and pressure. In addition, hourly precipitation 

measurements are included in the modeling and are required for wet deposition calculations 

in CALPUFF. Three-dimensional gridded data from the prognostic numerical model MM5 

are also included with two different resolution, 12-km for 2001 and 2002 and 36-km for 

2003. Table 3-3 lists the types of observational and modeled data available that are used in 

the modeling. There are around 12-13 surface meteorological stations in the refined run 

that are located within the modeling domain (Table 3-4). The surface data is extracted from 

the VISTAS surface standard dataset available on the TRC Atmospheric Studies Group web 

site (http://www.src.com). Upper air data closer to the refined domain is selected from the 

VISTAS Domain 3 dataset (Table 3-5). The 4 upper air stations selected are located outside 

the modeling refined domain. 

Approximately 32-33 precipitation stations are available for use in the modeling (Table 3-

6). These data are also extracted as a subdomain of VISTAS standard precipitation dataset. 

Figures 3-4 to 3-6 shows the locations and spatial coverage of all of these stations for 2001, 

2002 and 2003. 

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Appendix L.8 - 130

January 18, 2008
Geophysical and Meteorological Data 3-7 

Table 3-1. U.S. Geological Survey Land Use and Land Cover Classification System

Level I Level II 

10 Urban or Built-up Land 11 

12 

13 

14 

15 

16 

17 

Residential 

Commercial and Services 

Industrial 

Transportation, Communications and Utilities 

Industrial and Commercial Complexes 

Mixed Urban or Built-up Land 

Other Urban or Built-up Land 

20 Agricultural Land 21 

22 

23 

24 

Cropland and Pasture 

Orchards, Groves, Vineyards, Nurseries, and 

 Ornamental Horticultural Areas 

Confined Feeding Operations 

Other Agricultural Land 

30 Rangeland 31 

32 

33 

Herbaceous Rangeland 

Shrub and Brush Rangeland 

Mixed Rangeland 

40 Forest Land 41 

42 

43 

Deciduous Forest Land 

Evergreen Forest Land 

Mixed Forest Land 

50 Water 51 

52 

53 

54 

55 

Streams and Canals 

Lakes 

Reservoirs 

Bays and Estuaries 

Oceans and Seas 

60 Wetland 61 

62 

Forested Wetland 

Nonforested Wetland 

70 Barren Land 71 

72 

73 

74 

75 

76 

77 

Dry Salt Flats 

Beaches 

Sandy Areas Other than Beaches 

Bare Exposed Rock 

Strip Mines, Quarries, and Gravel Pits 

Transitional Areas 

Mixed Barren Land 

80 Tundra 81 

82 

83 

84 

85 

Shrub and Brush Tundra 

Herbaceous Tundra 

Bare Ground 

Wet Tundra 

Mixed Tundra 

90 Perennial Snow or Ice 91 

92 

Perennial Snowfields 

Glaciers 

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Appendix L.8 - 131

January 18, 2008
Geophysical and Meteorological Data 3-8 

Table 3-2. Default CALMET Land Use Categories and Associated Geophysical Parameters based on the U.S. Geologic

Classification System (14-Category System)

Land Use Type Description Surface 

Roughness (m)

Albedo Bowen Ratio Soil Heat 

Flux Parameter

Anthropo

Heat Flux (

10 Urban or Built-up Land 1.0 0.18 1.5 .25 0.0 20 Agricultural Land - 

Unirrigated 

0.25 0.15 1.0 .15 0.0 

-20* Agricultural Land - Irrigated 0.25 0.15 0.5 .15 0.0 

30 Rangeland 0.05 0.25 1.0 .15 0.0 40 Forest Land 1.0 0.10 1.0 .15 0.0 50 Water 0.001 0.10 0.0 1.0 0.0 54 Small Water Body 0.001 0.10 0.0 1.0 0.0 55 Large Water Body 0.001 0.10 0.0 1.0 0.0 60 Wetland 1.0 0.10 0.5 .25 0.0 61 Forested Wetland 1.0 0.1 0.5 0.25 0.0 62 Nonforested Wetland 0.2 0.1 0.1 0.25 0.0 70 Barren Land 0.05 0.30 1.0 .15 0.0 80 Tundra .20 0.30 0.5 .15 0.0 90 Perennial Snow or Ice .05 0.70 0.5 .15 0.0 

* Negative values indicate "irrigated" land use 

Pre-Hearing DraftRegional Haze SIP for TN Class I Areas
Geophysical and Meteorological Data 3-9 

Table 3-3. Meteorological Data Sources and Parameters Available

Type of Dataset Frequency Source Parameters 

Surface obs. Hourly NWS Wind speed, wind 

direction, temperature, 

ceiling height, cloud 

cover, relative humidity, 

surface pressure, 

precipitation type 

Upper Air Twice-daily NWS Soundings of wind speed, 

wind direction, 

temperature, and pressure 

Precipitation Hourly NWS Hourly precipitation 

amounts 

Modeled Profiles 

MM5 for 2001, 2002 and 

2003 

Hourly VISTAS/EPA Hourly, gridded fields of 

winds, temperature, 

pressure, and humidity and 

liquid water content on 12 

km grid for 2001 and 

2002. 

Hourly gridded fields on a 

36-km grid for 2003. 

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Appendix L.8 - 133

January 18, 2008
Geophysical and Meteorological Data 3-10 

Table 3-4. NWS Hourly Surface Stations for 2001, 2002 and 2003. 

WMO INIT Station Name State Year Latitude Longitude Elevation 

(0.1 m) 

LCC X1

(km) 

LCC Y1

(km) 

722154 KDNN Dalton GA 01,02,03 34.717 -84.867 216 1102.564 -510.885 

723048 K6A3 Andrews NC 01 35.2 -83.867 518 1185.117 -445.273 

723118 KCEU Clemson-Oconee Co A SC 01,02,03 34.667 -82.867 271 1283.806 -490.111 

723119 KGMU Greenville Downtown SC 01,02,03 34.850 -82.350 319.4 1327.112 -462.648 

723120 KGSP Greer Greenv’lSpartanbrg AP SC 01,02,03 34.90 -82.217 291.7 1338.156 -455.227 

723124 KGRD Greenwood AP SC 01,02,03 34.233 -82.15 192 1356.201 -527.227 

723125 KAND Anderson County AP SC 01,02,03 34.5 -82.717 231.6 1300.218 -506.274 

723144 KFQD Rutherfordton NC 01,02,03 35.433 -81.933 329 1353.882 -392.747 

723145 KHKY Hickory Regional AP NC 01,02,03 35.733 -81.383 348.4 1397.141 -351.662 

723148 KMRN Morganton/Lenior AP NC 01,02,03 35.817 -81.6 4 1376.347 -345.806 

723150 KAVL Asheville Regional AP NC 01,02,03 35.433 -82.533 652.3 1300.433 -401.509 

723183 KTRI Bristol TRI City AP TN 01,02,03 36.467 -82.400 457.2 1293.970 -286.574 

723246 KOQT Oak Ridge TN 01,02,03 36.017 -84.233 277 1139.638 -360.373 

723260 KTYS Knoxville Mcghee 

Tyson AP 

TN 01,02,03 35.817 -83.983 293.2 1164.964 -379.127 

1

 Lambert Conic Conformal (LCC) projection, LCC origin (40N, 97W), standard parallels (33N, 45N), datum NWS-84.

Table 3-5. Upper Air Stations used for 2001, 2002 and 2003. 

# Station Name WBAN# WMO# Latitude Longitude LCC X1

 LCC Y1 Elevation 

 (deg) (deg) (km) (km) (m) 

1 

Peachtree City, GA 

FFC 

53819 72215 33.35 -84.56 1150.994 -657.420 246 

2 

Greensboro, NC 

GSO 

13723 72317 36.08 -79.95 1516.732 -290.880 277 

3 

Roanoke/Blacksburg, VA 

RNK 

53829 72318 37.20 -80.41 1453.770 -176.566 648 

4 

Nashville, TN 

BNA 

13897 72327 36.25 -86.57 929.093 -361.386 180 

1 Lambert Conic Conformal (LCC) projection, LCC origin (40N, 97W), standard parallels (33N, 45N), datum NWS-84.

Pre-Hearing Draft

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Appendix L.8 - 134

January 18, 2008
Geophysical and Meteorological Data 3-11 

Table 3-6. Hourly NWS Precipitation Stations for 2001, 2002 and 2003. 

Station ID State Year of Longitude Latitude LCC X1 LCC Y1

Data (deg) (deg) (km) (km) 

91619 GA 01,02,03 34.412N 83.207W 1257.438 -522.814 

91863 GA 02,03 34.759N 84.765W 1111.152 -505.028 

91998 GA 01,02,03 34.450N 83.855W 1198.178 -527.400 

92479 GA 01,02,03 34.572N 84.000W 1183.123 -515.908 

92578 GA 01,02,03 34.417N 84.118W 1174.885 -534.457 

94651 GA 01 34.456N 84.456W 1143.661 -534.485 

96091 GA 01,02,03 34.929N 83.396W 1231.787 -468.722 

98935 GA 01,02,03 34.721N 83.722W 1205.839 -495.903 

157677 KY 01,02,03 36.667N 84.483W 1107.585 -292.208 

310300 NC 01,03 35.432N 82.537W 1300.094 -401.676 

310301 NC 01,02,03 35.600N 82.533W 1297.500 -383.243 

310312 NC 01,02,03 35.883N 81.950W 1344.151 -343.838 

310967 NC 01,02,03 36.069N 81.352W 1393.513 -314.528 

314764 NC 01,02,03 35.433N 82.234W 1327.075 -397.187 

317845 NC 01,02,03 35.314N 81.534W 1391.626 -399.719 

318448 NC 01,02,03 35.567N 82.383W 1311.423 -384.698 

380613 SC 01,02,03 34.601N 82.434W 1323.974 -491.127 

381770 SC 01,02,03 34.660N 82.824W 1287.801 -490.270 

383747 SC 01,02,03 34.885N 82.224W 1337.797 -456.971 

384581 SC 01,02,03 34.983N 83.067W 1260.431 -458.293 

385017 SC 01,02,03 34.499N 82.022W 1362.944 -496.200 

385278 SC 01,02,03 34.792N 83.246W 1247.555 -481.693 

386831 SC 01,02,03 34.882N 82.719W 1293.409 -464.465 

388707 SC 01,02,03 34.949N 82.443W 1317.009 -453.167 

388951 SC 01,02 34.398N 82.230W 1345.997 -510.354 

401094 TN 01,02,03 36.473N 82.404W 1293.512 -285.975 

401978 TN 01,02,03 35.029N 84.724W 1110.822 -474.866 

402934 TN 01,02,03 36.142N 82.426W 1297.430 -322.459 

404950 TN 01,02,03 35.818N 83.986W 1164.682 -379.056 

406272 TN 01,02,03 36.169N 83.402W 1210.771 -332.974 

406750 TN 01,02,03 36.023N 84.233W 1139.545 -359.715 

407850 TN 01,02,03 35.766N 84.777W 1095.105 -394.595 

407884 TN 01,02,03 36.416N 82.984W 1243.498 -300.302 

408766 TN 01,02,03 36.249N 84.697W 1095.011 -340.636 1 Lambert Conic Conformal (LCC) projection, LCC origin (40N, 97W), standard parallels (33N, 45N), datum NWS-84.

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Appendix L.8 - 135

January 18, 2008
Geophysical and Meteorological Data 3-12 

Figure 3-4. Surface, upper air and precipitation stations and MM5 data used in the 2001 modeling. The five 

Class I areas and the facility are also shown. 

1000 1100 1200 1300 1400 1500

LCC East (km)

-600

-500

-400

-300

-200

LCC North (km)

-1

100

300

500

700

900

1100

1300

1500

1700

1900

2100

2300

2500

2700

2900

3100

3300

3500

3700

3900

4500

Terrain (m)

LCC Origin: 40.00N, 97.00W

Datum: NWS-84

Matching Parallels: 33.00N, 45.00N

Upper air stations

Surface stations

precipitation stations

Surface stations, Precipitation stations and Upper air stations

over CALMET domain - year 2001

MM5 grid points over the domain

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Appendix L.8 - 136

January 18, 2008
Geophysical and Meteorological Data 3-13 

Figure 3-5. Surface, upper air and precipitation stations and MM5 data used in the 2002 modeling. The five 

Class I areas and the facility are also shown. 

1000 1100 1200 1300 1400 1500

LCC East (km)

-600

-500

-400

-300

-200

LCC North (km)

-1

100

300

500

700

900

1100

1300

1500

1700

1900

2100

2300

2500

2700

2900

3100

3300

3500

3700

3900

4500

Terrain (m)

Surface stations, Precipitation stations and Upper air stations

over CALMET domain - year 2002

Upper air stations

Surface stations

Precipitation stations

LCC Origin: 40.00N, 97.00W

Datum: NWS-84

Matching Parallels: 33.00N, 45.00N

MM5 grid points over the domain

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Appendix L.8 - 137

January 18, 2008
Geophysical and Meteorological Data 3-14 

Figure 3-6. Surface, upper air and precipitation stations and MM5 data used in the 2003 modeling. The five 

Class I areas and the facility are also shown. 

1000 1100 1200 1300 1400 1500

LCC East (km)

-600

-500

-400

-300

-200

LCC North (km)

-1

100

300

500

700

900

1100

1300

1500

1700

1900

2100

2300

2500

2700

2900

3100

3300

3500

3700

3900

4500

Terrain (m)

Surface stations, Precipitation stations and Upper air stations

over CALMET domain - year 2003

Upper air stations

Surface stations

Precipitation stations

LCC Origin: 40.00N, 97.00W

Datum: NWS-84

Matching Parallels: 33.00N, 45.00N

MM5 grid points over the domain

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Appendix L.8 - 138

January 18, 2008
Geophysical and Meteorological Data 3-15 

3.4 Air Quality Monitoring Data 

CALPUFF uses hourly ozone concentration measurements in the chemical transformation 

rates (SO2 to SO4, NOx to HNO3/NO3). The ambient ozone measurements are used in 

determining SO2 loss rates due to chemical transformation to sulfate and in determining 

NOx loss rates to nitrate. Ambient ozone monitoring data for 2001, 2002 and 2003 are 

extracted from the U.S. EPA AIRS and CASTNet networks and are used to develop hourly 

ozone monitoring data files for the each year of the modeling analysis. Data for VISTAS 

Domain 3 are extracted from the standard ozone dataset available on the TRC CALPUFF 

web site (http://www.src.com) to create the hourly ozone file. A total of ~35 monitoring 

stations, listed in Table 3-7, are used in the modeling. See Figures 3-7 to 3-9 which show 

the locations of each of the available stations for each year modeled. 

A constant background ammonia concentration of 0.5 parts per billion (ppb) as 

recommended in the BART Modeling Protocol is used for CALPUFF runs of every point 

and lines sources. 

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Appendix L.8 - 139

January 18, 2008
Geophysical and Meteorological Data 3-16 

Table 3-7. Ozone Stations for 2001, 2002 and 2003. 

Network Year ID Latitude Longitude UTM X 

(km) 

UTM Y 

(km) 

AIRS 01,02,03 130850001 34.37778N 84.05611W 1181.109 -537.962 

AIRS 01,02,03 132130003 34.785N 84.62695W 1123.221 -500.474 

AIRS 01,02,03 210130002 36.60806N 83.73695W 1174.094 -289.300 

AIRS 01,02,03 370110002 35.97167N 81.93417W 1343.932 -333.920 

AIRS 01,02,03 370210030 35.5N 82.6W 1293.290 -395.136 

AIRS 01,02,03 370270003 35.93583N 81.53028W 1380.288 -331.779 

AIRS 03 370750001 35.25793N 83.79562W 1190.583 -437.988 

AIRS 01,02,03 370870004 35.50528N 82.96472W 1260.708 -399.683 

AIRS 01,02,03 370870035 35.37917N 82.7925W 1278.227 -411.081 

AIRS 01,02,03 370870036 35.59N 83.0775W 1249.225 -391.967 

AIRS 01,02,03 370990005 35.52445N 83.23612W 1236.198 -401.313 

AIRS 01,02,03 371730002 35.43551N 83.4437W 1219.158 -413.859 

AIRS 01,02,03 371990003 35.73774N 82.28523W 1317.069 -364.619 

AIRS 01,02,03 450010001 34.32556N 82.38611W 1333.182 -520.586 

AIRS 01,02,03 450070003 34.775N 82.49028W 1315.835 -472.896 

AIRS 01,02,03 450210002 35.13028N 81.81639W 1369.841 -424.079 

AIRS 01,02,03 450730001 34.805N 83.2375W 1248.103 -480.151 

AIRS 01,02,03 450770002 34.68607N 82.83866W 1286.031 -487.622 

AIRS 01,02,03 450830009 34.98861N 82.07555W 1349.239 -443.444 

AIRS 01,02,03 470010101 35.965N 84.22334W 1141.302 -365.953 

AIRS 01,02,03 470090101 35.63139N 83.94361W 1171.408 -398.967 

AIRS 01,02,03 470090102 35.60306N 83.78361W 1186.118 -399.997 

AIRS 01,02 470630003 36.30778N 83.13448W 1232.073 -314.190 

AIRS 01,02,03 470650028 35.07639N 85.15167W 1071.664 -474.795 

AIRS 01,02,03 470651011 35.14028N 85.17W 1069.096 -467.990 

AIRS 01,02,03 470890002 36.11445N 83.60111W 1194.058 -341.582 

AIRS 01,02,03 470930021 36.08472N 83.76473W 1180.059 -346.975 

AIRS 01,02,03 470931020 36.01944N 83.87361W 1171.459 -355.536 

AIRS 01 470931030 35.89834N 83.95722W 1165.967 -369.882 

AIRS 01,02,03 471210104 35.28889N 84.94611W 1087.033 -449.008 

AIRS 01,02,03 471550101 35.69667N 83.60972W 1200.089 -387.457 

AIRS 01,02,03 471550102 35.56278N 83.49806W 1212.219 -400.643 

CASTNet 01,02,03 COW137 35.0608N 83.4305W 1226.514 -454.742 

CASTNet 01,02,03 PNF126 36.1058N 82.0454W 1331.666 -320.908 

CASTNet 01,02,03 GRS420 35.6331N 83.9422W 1171.507 -398.762 

CASTNet 01,02,03 SPD111 36.47N 83.8268W 1168.403 -305.576 

 

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January 18, 2008
Geophysical and Meteorological Data 3-17 

Figure 3-7. CASTNet and AIRS ozone stations used in the 2001 modeling. The five Class I areas in the domain 

and the facility are also shown. 

1100 1150 1200 1250 1300 1350 1400

LCC East (km)

-500

-450

-400

-350

-300

LCC North (km)

-1

100

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Terrain (m)

LCC Origin: 40.00N, 97.00W

Datum: NWS-84

Matching Parallels: 33.00N, 45.00N Ozone stations

Ozone stations location over CALMET domain - year 2001

South Plant

TN

KY NC

SC

GA

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January 18, 2008
Geophysical and Meteorological Data 3-18 

Figure 3-8. CASTNet and AIRS ozone stations used in the 2002 modeling. The five Class I areas in the domain 

and the facility are also shown. 

1100 1150 1200 1250 1300 1350 1400

LCC East (km)

-500

-450

-400

-350

-300

LCC North (km)

-1

100

300

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Terrain (m)

LCC Origin: 40.00N, 97.00W

Datum: NWS-84

Matching Parallels: 33.00N, 45.00N Ozone stations

Ozone stations location over CALMET domain - year 2002

TN

KY

NC

SC

GA

South Plant

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Appendix L.8 - 142

January 18, 2008
Geophysical and Meteorological Data 3-19 

Figure 3-9. CASTNet and AIRS ozone stations used in the 2003 modeling. The five Class I areas in the domain 

and the facility are also shown. 

1100 1150 1200 1250 1300 1350 1400

LCC East (km)

-500

-450

-400

-350

-300

LCC North (km)

-1

100

300

500

700

900

1100

1300

1500

1700

1900

2100

2300

2500

2700

2900

3100

3300

3500

3700

3900

4500

Terrain (m)

LCC Origin: 40.00N, 97.00W

Datum: NWS-84

Matching Parallels: 33.00N, 45.00N Ozone stations

Ozone stations location over CALMET domain - year 2003

TN

KY NC

SC

GA

South Plant

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Appendix L.8 - 143

January 18, 2008
Air Quality Modeling Methodology 4-1 

4. AIR QUALITY MODELING METHODOLOGY 

4.1 Model Selection 

The terrain of the region, the large source-receptor distances, and the importance of 

chemical transformation, wet deposition, and dry deposition are principal factors in the 

selection of a modeling approach. The terrain considerations included the need to 

incorporate terrain channeling effects on the flow field, diurnally varying slope flows 

(downslope flows at night, upslope flows during the day), and representing the strong 

spatial variability of the wind fields over relatively short distances. The ability to treat 

plume interactions and plume impingement on terrain above stack height are also important. 

The CALPUFF modeling system (Scire et al., 2000a,b) is used in the BART analysis for the 

six Class I areas in the 300-km radius of Alcoa South Plant facility. CALPUFF and its 

meteorological model CALMET, are designed to handle the complexities posed by complex 

terrain, the long source receptor distances, chemical transformation and deposition, and 

other issues related to Class I impacts. The CALPUFF modeling system has been adopted 

by the U.S. EPA as a Guideline Model for source-receptor distances greater than 50 km, and 

for use on a case-by-case basis in complex flow situations for shorter distances (Federal 

Register, April 15, 2003a). CALPUFF is recommended for Class I impact assessments by 

the Federal Land Managers Workgroup (FLAG, 2000) and the Interagency Workgroup on 

Air Quality Modeling (IWAQM, 1998). CALPUFF is recommended by the USEPA for 

BART analyses (Federal Register, 6 July 2005). 

CALMET is a diagnostic meteorological model that produces three-dimensional wind and 

temperature fields and two-dimensional fields of mixing heights and other meteorological 

fields. It contains slope flow effects, terrain channeling, and kinematic effects of terrain. 

CALPUFF is a non-steady-state Gaussian puff model. It includes algorithms for building 

downwash effects as well as chemical transformation, wet deposition, and dry deposition. 

One capability of CALPUFF not found in many specialized models such as CTDMPLUS is 

the ability to treat the combined effects of multiple processes (e.g., building downwash 

effects in complex terrain; dry deposition and overwater dispersion, etc.). A complete 

summary of the capabilities and features of CALMET and CALPUFF is provided in 

Sections 4.1.1 and 4.1.2. 

Regulatory models such as the Industrial Source Complex Short Term (ISCST3) model 

have several important limitations for this study. One critical limitation is that ISCST3 is a 

steady-state, straight line plume model that cannot respond to the significant terrain-induced 

spatial variability to the wind fields that dominate transport in the vicinity of the Class I 

areas. ISCST3 uses spatially-invariant wind fields based on single-station wind 

observations. Also, the steady-state formulation does not account for causality effects, 

which can be important for source-receptor distances greater than a few kilometers. 

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January 18, 2008
Air Quality Modeling Methodology 4-2 

4.1.1 Major Features of CALMET 

The CALMET meteorological model consists of a diagnostic wind field module and 

micrometeorological modules for overwater and overland boundary layers. When using 

large domains, the user has the option to adjust input winds to a Lambert Conformal 

Projection coordinate system to account for Earth's curvature. The diagnostic wind field 

module uses a two-step approach to the computation of the wind fields (Douglas and 

Kessler, 1988). In the first step, an initial-guess wind field is adjusted for kinematic effects 

of terrain, slope flows, and terrain blocking effects to produce a Step 1 wind field. The 

second step consists of an objective analysis procedure to introduce observational data into 

the Step 1 wind field to produce a final wind field. 

The major features and options of the meteorological model are summarized in Table 4-1. 

The techniques used in the CALMET model are briefly described below. 

Step 1 Wind Field

Kinematic Effects of Terrain: The approach of Liu and Yocke (1980) is used to evaluate 

kinematic terrain effects. The domain-scale winds are used to compute a terrain-forced 

vertical velocity, subject to an exponential, stability-dependent decay function. The 

kinematic effects of terrain on the horizontal wind components are evaluated by applying a 

divergence-minimization scheme to the initial guess wind field. The divergence 

minimization scheme is applied iteratively until the three-dimensional divergence is less 

than a threshold value. 

Slope Flows: The slope flow algorithm in CALMET has recently been upgraded (Scire and 

Robe, 1997). It is based on the shooting flow algorithm of Mahrt (1982). This scheme 

includes both advective-gravity and equilibrium flow regimes. At night, the slope flow 

model parameterizes the flow down the sides of the valley walls into the floor of the valley, 

and during the day, upslope flows are parameterized. The magnitude of the slope flow 

depends on the local surface sensible heat flux and local terrain gradients. The slope flow 

wind components are added to the wind field adjusted for kinematic effects. 

Blocking Effects: The thermodynamic blocking effects of terrain on the wind flow are 

parameterized in terms of the local Froude number (Allwine and Whiteman, 1985). If the 

Froude number at a particular grid point is less than a critical value and the wind has an 

uphill component, the wind direction is adjusted to be tangent to the terrain. 

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January 18, 2008
Air Quality Modeling Methodology 4-3 

Table 4-1. Major Features of the CALMET Meteorological Model

Boundary Layer Modules of CALMET 

 - Overland Boundary Layer - Energy Balance Method 

 - Overwater Boundary Layer - Profile Method 

 - Produces Gridded Fields of: 

 - Surface Friction Velocity 

 - Convective Velocity Scale 

 - Monin-Obukhov Length 

 - Mixing Height 

 - PGT Stability Class 

 - Air Temperature (3-D) 

 - Precipitation Rate 

• Diagnostic Wind Field Module of CALMET

 - Slope Flows 

 - Kinematic Terrain Effects 

 - Terrain Blocking Effects 

 - Divergence Minimization 

 - Produces Gridded Fields of U, V, W Wind Components 

 - Inputs Include Domain-Scale Winds, Observations, and 

 (optionally) Coarse-Grid Prognostic Model Winds 

 - Lambert Conformal Projection Capability 

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January 18, 2008
Air Quality Modeling Methodology 4-4 

Step 2 Wind Field 

The wind field resulting from the adjustments described above of the initial-guess wind is 

the Step 1 wind field. The second step of the procedure involves the introduction of 

observational data into the Step 1 wind field through an objective analysis procedure. An 

inverse-distance squared interpolation scheme is used which weighs observational data 

heavily in the vicinity of the observational station, while the Step 1 wind field dominates 

the interpolated wind field in regions with no observational data. The resulting wind field is 

subject to smoothing, an optional adjustment of vertical velocities based on the O'Brien 

(1970) method, and divergence minimization to produce a final Step 2 wind field. 

CALMET Boundary Layer Models 

The CALMET model contains two boundary layer models for application to overland and 

overwater grid cells. 

Overland Boundary Layer Model: Over land surfaces, the energy balance method of 

Holtslag and van Ulden (1983) is used to compute hourly gridded fields of the sensible heat 

flux, surface friction velocity, Monin-Obukhov length, and convective velocity scale. 

Mixing heights are determined from the computed hourly surface heat fluxes and observed 

temperature soundings using a modified Carson (1973) method based on Maul (1980). 

Gridded fields of Pasquill-Gifford-Turner (PGT) stability class and optional hourly 

precipitation rates are also determined by the model. 

Overwater Boundary Layer Model: The aerodynamic and thermal properties of water 

surfaces suggest that a different method is best suited for calculating the boundary layer 

parameters in the marine environment. A profile technique, using air-sea temperature 

differences, is used in CALMET to compute the micrometeorological parameters in the 

marine boundary layer. 

An upwind-looking spatial averaging scheme is optionally applied to the mixing heights 

and 3-dimensional temperature fields in order to account for important advective effects. 

4.1.2 Major Features of CALPUFF 

By its puff-based formulation and through the use of three-dimensional meteorological data 

developed by the CALMET meteorological model, CALPUFF can simulate the effects of 

time- and space-varying meteorological conditions on pollutant transport from sources in 

complex terrain. The major features and options of the CALPUFF model are summarized 

in Table 4-2. Some of the technical algorithms are briefly described below. 

Complex Terrain: The effects of complex terrain on puff transport are derived from the 

CALMET winds. In addition, puff-terrain interactions at gridded and discrete receptor 

locations are simulated using one of two algorithms that modify the puff-height (either that 

of ISCST3 or a general "plume path coefficient" adjustment), or an algorithm that simulates 

enhanced vertical dispersion derived from the weakly-stratified flow and dispersion module 

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January 18, 2008
Air Quality Modeling Methodology 4-5 

of the Complex Terrain Dispersion Model (CTDMPLUS) (Perry et al., 1989). The puffheight adjustment algorithms rely on the receptor elevation (relative to the elevation at the 

source) and the height of the puff above the surface. The enhanced dispersion adjustment 

relies on the slope of the gridded terrain in the direction of transport during the time step. 

Subgrid Scale Complex Terrain (CTSG): An optional module in CALPUFF, CTSG 

treats terrain features that are not resolved by the gridded terrain field, and is based on the 

Complex Terrain Dispersion Model (CTDMPLUS) (Perry et al., 1989). Plume 

impingement on subgrid-scale hills is evaluated at the CTSG subgroup of receptors using a 

dividing streamline height (Hd) to determine which pollutant material is deflected around 

the sides of a hill (below Hd) and which material is advected over the hill (above Hd). The 

local flow (near the feature) used to define Hd is taken from the gridded CALMET fields. 

As in CTDMPLUS, each feature is modeled in isolation with its own set of receptors. 

Puff Sampling Functions: A set of accurate and computationally efficient puff sampling 

routines are included in CALPUFF which solve many of the computational difficulties 

encountered when applying a puff model to near-field releases. For near-field applications 

during rapidly-varying meteorological conditions, an elongated puff (slug) sampling 

function may be used. An integrated puff approach may be used during less demanding 

conditions. Both techniques reproduce continuous plume results under the appropriate 

steady state conditions. 

Building Downwash: The Huber-Snyder and Schulman-Scire downwash models are both 

incorporated into CALPUFF. An option is provided to use either model for all stacks, or 

make the choice on a stack-by-stack and wind sector-by-wind sector basis. Both algorithms 

have been implemented in such a way as to allow the use of wind direction specific building 

dimensions. CALPUFF also includes the PRIME building downwash module. 

Dispersion Coefficients: Several options are provided in CALPUFF for the computation 

of dispersion coefficients, including the use of turbulence measurements (σv and σw), the 

use of similarity theory to estimate σv and σw from modeled surface heat and momentum 

fluxes, or the use of Pasquill-Gifford (PG) or McElroy-Pooler (MP) dispersion coefficients, 

or dispersion equations based on the Complex Terrain Dispersion Model (CTDM). Options 

are provided to apply an averaging time correction or surface roughness length adjustments 

to the PG coefficients. 

Overwater and Coastal Interaction Effects: Because the CALMET meteorological 

model contains both overwater and overland boundary layer algorithms, the effects of water 

bodies on plume transport, dispersion, and deposition can be simulated with CALPUFF. 

The puff formulation of CALPUFF is designed to handle spatial changes in meteorological 

and dispersion conditions, including the abrupt changes that occur at the coastline of a 

major body of water. 

Dry Deposition: A full resistance model is provided in CALPUFF for the computation of 

dry deposition rates of gases and particulate matter as a function of geophysical parameters, 

meteorological conditions, and pollutant species. Options are provided to allow userPre-Hearing Draft

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January 18, 2008
Air Quality Modeling Methodology 4-6 

specified, diurnally varying deposition velocities to be used for one or more pollutants 

instead of the resistance model (e.g., for sensitivity testing) or to by-pass the dry deposition 

model completely. For particles, source-specific mass distributions may be provided for 

use in the resistance model. 

Wind Shear Effects: CALPUFF contains an optional puff splitting algorithm that allows 

vertical wind shear effects across individual puffs to be simulated. Differential rates of 

dispersion and transport among the "new" puffs generated from the original, well-mixed 

puff can substantially increase the effective rate of horizontal spread of the material. 

Wet Deposition: An empirical scavenging coefficient approach is used in CALPUFF to 

compute the depletion and wet deposition fluxes due to precipitation scavenging. The 

scavenging coefficients are specified as a function of the pollutant and precipitation type 

(i.e., frozen vs. liquid precipitation). 

Chemical Transformation: CALPUFF includes options for parameterizing chemical 

transformation effects using the five species scheme (SO2, SO=

4, NOx, HNO3, and NO−3) 

employed in the MESOPUFF II model or a set of user-specified, diurnally-varying 

transformation rates. 

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January 18, 2008
Air Quality Modeling Methodology 4-7 

Table 4-2. Major Features of the CALPUFF Model. 

 • Source types

 - Point sources (constant or variable emissions) 

 - Line sources (constant or variable emissions) 

 - Volume sources (constant or variable emissions) 

 - Area sources (constant or variable emissions) 

 • Non-steady-state emissions and meteorological conditions

 - Gridded 3-D fields of meteorological variables (winds, temperature) 

 - Spatially-variable fields of mixing height, friction velocity, convective velocity scale, 

 Monin-Obukhov length, precipitation rate 

 - Vertically and horizontally-varying turbulence and dispersion rates 

 - Time-dependent source and emissions data for point, area, and volume sources 

 - Temporal or wind-dependent scaling factors for emission rates, for all source types 

 • Interface to the Emissions Production Model (EPM)

 - Time-varying heat flux and emissions from controlled burns and wildfires 

 • Efficient sampling functions

 - Integrated puff formulation 

 - Elongated puff (slug) formulation 

 • Dispersion coefficient (σy, σz) options

 - Direct measurements of σv and σw

 - Estimated values of σv and σw based on similarity theory 

 - Pasquill-Gifford (PG) dispersion coefficients (rural areas) 

 - McElroy-Pooler (MP) dispersion coefficients (urban areas) 

 - CTDM dispersion coefficients (neutral/stable) 

 • Vertical wind shear

 - Puff splitting 

 - Differential advection and dispersion 

 • Plume rise

 - Buoyant and momentum rise 

 - Stack tip effects 

 - Building downwash effects 

 - Partial penetration 

 - Vertical wind shear 

 • Building downwash

 - Huber-Snyder method 

 - Schulman-Scire method 

 - PRIME method 

 • Complex terrain

 - Steering effects in CALMET wind field 

 - Optional puff height adjustment: ISC3 or "plume path coefficient" 

 - Optional enhanced vertical dispersion (neutral/weakly stable flow in CTDMPLUS) 

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Air Quality Modeling Methodology 4-8 

Table 4-2. Major Features of the CALPUFF Model (Cont’d) 

 • Subgrid scale complex terrain (CTSG option)

 - Dividing streamline, Hd, as in CTDMPLUS: 

 - Above Hd, material flows over the hill and experiences altered diffusion rates 

 - Below Hd, material deflects around the hill, splits, and wraps around the hill 

 • Dry Deposition 

 - Gases and particulate matter 

 - Three options: 

 - Full treatment of space and time variations of deposition with a resistance model 

 - User-specified diurnal cycles for each pollutant 

 - No dry deposition 

 • Overwater and coastal interaction effects

 - Overwater boundary layer parameters 

 - Abrupt change in meteorological conditions, plume dispersion at coastal boundary 

 - Plume fumigation 

 • Chemical transformation options

 - Pseudo-first-order chemical mechanism for SO2, SO=

4, NOx, HNO3, and NO−3 

(MESOPUFF II method) 

- Pseudo-first-order chemical mechanism for SO2, SO=

4, NO, NO2 HNO3, and NO−3 (RIVAD/ARM3 

method) 

 - User-specified diurnal cycles of transformation rates 

 - No chemical conversion 

 • Wet Removal

 - Scavenging coefficient approach 

 - Removal rate a function of precipitation intensity and precipitation type 

 • Graphical User Interface

 - Point-and-click model setup and data input 

 - Enhanced error checking of model inputs 

 - On-line Help files 

 • Interface Utilities

 - Scan ISCST3 and AUSPLUME meteorological data files for problems 

 - Translate ISCST3 and AUSPLUME input files to CALPUFF input format

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Air Quality Modeling Methodology 4-9 

4.2 Modeling Domain 

CALMET and CALPUFF use terrain-following coordinates. In order to cover a large 

enough area for the refined analysis, a modeling domain of 334 x 259 grid cells, uniform in 

the horizontal with a spatial resolution of 1km is used. In the vertical, a stretched grid is 

used with finer resolution in the lower layers and somewhat coarser resolution aloft thus 

allowing adequate representation of the mixed layer. The ten vertical levels are centered at: 

10, 30, 60, 120, 240, 480, 920, 1600, 2500 and 3500 meters. 

CALPUFF is run for three years, 2001, 2002 and 2003. A network of discrete receptors 

derived from the list of receptors developed by the National Park Service (NPS) are located 

within the boundaries of the five Class I areas, Great Smoky Mountains National Park, 

Linville Gorge, Shining Rock, Cohutta and Joyce-Kilmer/ Slickrock Wilderness Areas. 

4.3 Meteorological Modeling Options 

Initial Guess Field 

MM5 data are used to define the initial guess field for the CALMET simulations. For 2001 

and 2002 hourly MM5 data with an interval of 12 km and 34 vertical levels are used as the 

initial guess wind field. MM5 data with an interval of 36 km and 34 vertical levels are used 

as the initial guess wind field for 2003. 

Step 1 Field: Terrain Effects 

In developing the Step 1 wind field, CALMET adjusts the initial guess field to reflect 

kinematic effects of the terrain, slope flows and blocking effects. Slope flows are a function 

of the local slope and altitude of the nearest crest. The crest is defined as the highest peak 

within a radius TERRAD around each grid point. A value of TERRAD of 15 km is 

determined based on an analysis of the scale of the terrain and is used in the CALMET 

simulations. The Step 1 field produces a flow field consistent with the fine-scale CALMET 

terrain resolution (1 km). 

Step 2 Field: Objective Analysis 

In Step 2, observations are incorporated into the Step 1 wind field to produce a final wind 

field. Each observation site influences the final wind field within a radius of influence 

(parameters RMAX1 at the surface and RMAX2 aloft). Observations and Step 1 field are 

weighted by means of parameters R1 at the surface and R2 aloft: at a distance R1 from an 

observation site, the Step 1 wind field and the surface observations are weighted equally. 

RMAX1 and RMAX2 are set to large values (40 km), while small values of R1 and R2 

(5km) are used in order to limit the influence of observations on the grid so that important 

terrain effects are not smoothed out. 

4.4 Dispersion Modeling Options 

The CALPUFF simulations is conducted using the following model options: 

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Air Quality Modeling Methodology 4-10 

 - Gaussian near-field distribution 

 - Transitional plume rise 

 - Stack tip downwash 

 - Pasquill-Gifford (PG) dispersion coefficients (rural areas), McElroy-Pooler 

coefficients (urban areas) 

 - Transition of σy to time-dependent (Heffter) growth rates 

 - Partial plume path adjustment for terrain 

 - Wet deposition, dry deposition, and chemical transformation are considered 

The CALPUFF computational grid is the same as the meteorological grid. The modeling 

domain includes a buffer zone of at least 50 km around the source area and beyond the 

borders of the Class I areas. This eliminates edge effects and allows pollutants involved in 

flow reversals to be brought back into the Class I area. 

Two important computational parameters in CALPUFF are XMXLEN (maximum length of 

an emitted puff, in grid units) and XSAMLEN (maximum travel distance of a puff, in grid 

units, during one time step). Both of these variables are set to 1.0 in the CALPUFF 

simulations in order to allow the strong wind channeling effects to be accounted for in the 

puff trajectory calculations. The first parameter ensures that the length of an emitted puff 

does not become so large so that it cannot respond to changes in the wind field on the scale 

of the meteorological grid. The model automatically increases the frequency of puff 

releases to ensure the length of a single puff is not larger than the grid size. The second 

parameter decreases the internal time step to ensure the travel distance during one time step 

does not exceed the grid size. 

The partial plume path adjustment option is used in CALPUFF for this analysis 

(MCTADJ=3). The CALMET wind field incorporates the effect of the terrain on the plume 

trajectories. The plume path coefficient is used to characterize the local effect on groundlevel concentrations. The default plume path coefficients (PPC) used for this analysis are 

listed below: 

 Stability Class A B C D E F 

 PPC 0.5 0.5 0.5 0.5 0.35 0.35 

Deposition and chemical transformation effects are modeled using the default dry 

deposition model, the scavenging coefficient wet removal module, and the default chemical 

transformation mechanism. A total of eleven species are modeled with CALPUFF for this 

analysis: SO2, SO4, NOx, HNO3, NO3, and six subcategories of PM10, (PM800, PM425, PM187, 

PM112, PM081, PM056). Of these eleven species, three are emitted by the Alcoa sources: SO2, 

NOx, PM10, with PM10 being divided into the six subcategories described above. The 

chemical mechanism computes transformation rates of SO2 to SO4 and NOx to NO3/HNO3. 

Hourly measured ozone concentrations are provided in an external OZONE.DAT file for 

use with the chemical transformation module. These ozone concentrations, along with 

radiation intensity, are used as surrogates for the OH concentration during the day when the 

gas phase free radical chemistry is active. 

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Air Quality Modeling Methodology 4-11 

To allow for flexibility each source is modeled by group of same emission rates and their 

source contributions are summed at the end. 

4.5 Visibility Calculations 

Calculations of the impact of the simulated plume particulate matter component 

concentrations on light extinction is carried out in the CALPOST postprocessor. The 

procedures is consistent with the VISTAS modeling protocol (VISTAS, 2005). In this 

analysis, both the original IMPROVE/EPA equation and the new IMPROVE equation are 

applied to determine the change in light extinction due to changes in component 

concentrations. Using the notations of CALPOST, the original formula is the following: 

Bext = 3f(RH)[(NH4)2SO4] + 3f(RH)[NH4NO3] + 4[OC] + 1[Soil] + 0.6[Coarse Mass] 

+10[EC] + bray

The concentrations, in square brackets, are in μg/m3

 and bext is in units of Mm-1. The 

Rayleigh scattering term (bray) has a default value of 10 Mm-1, as recommended in EPA 

guidelines for tracking reasonable progress (EPA, 2003a). Note that organic carbon (OC) 

consists of condensable particulates which are assumed to be split evenly between the 

lowest two particle size categories. Soil is fine particulates which is defined as PM2.5. 

These species are created through scaling and summing of the various CALPUFF output 

files using the POSTUTIL program. 

There are a few important differences in detail and in notation between the CALPOST 

formula for estimating light extinction and that of IMPROVE and EPA. First, the OC in the 

formula above represents organic carbonaceous matter (OMC in IMPROVE’s notation), 

which is 1.4 times the OC (i.e. organic carbon alone) in the IMPROVE formula. The EC 

above in synonymous with LAC in the IMPROVE formula. New implementations were 

added in CALPOST regarding the choice of f(RH) curve. One can now choose from 

IMPROVE f(RH) curve, whose values are documented in the December 2000 FLAG report, 

EPA f(RH) curve, as documented in EPA’s regional haze guidance documents, 2003 and 

IWAQM 1998 f(RH) curve. Also, CALPOST sets the maximum relative humidity at 98 

percent by default (although the user can change it), while the EPA guidance now caps it at 

95 percent. 

The haze index (HI) is calculated from the extinction coefficient via the following formula: 

HI = 10 ln(bext/10) 

Where HI is in units of deciviews (dv) and bext is in Mm-1. The impact of a source is 

determined by comparing HI for estimated natural background conditions with the impact 

of the source and without the impact of the source. 

CALPOST Method 6 is used to compute the extinction change in deciviews consistent with 

the procedures outlined in the VISTAS modeling protocol. 

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Air Quality Modeling Methodology 4-12 

A monthly background concentration must be entered into the CALPOST input control file. 

This background concentration is entered only for SOIL. The way it is computed makes it 

suitable to represent background light extinction for all particulates (hygroscopic + nonhygroscopic) at the same time when multiplied by an extinction coefficient of 1. 

From the natural background light extinction shown in Table 4-3, taken from Appendix B 

of the Guidance for Estimating Natural Visibility Conditions Under the Regional Haze 

Program (September 2003) and based on the annual average natural background for 

example in Great Smoky Mountains National park, the value of the Haze Index (HI) for the 

annual average is equal to 7.60 dv. It can be converted to the total background light 

extinction bback for the annual average using the following equation: 

10 10

HI

back b = ⋅ e

Where HI is Haze Index expressed in units of deciviews (dv). 

Therefore, total bback for the annual average in Great Smoky Mountains NP, including the 

Rayleigh scattering coefficient is calculated as 

10 1

7.60

10 21.38 − bback = ⋅ e = Mm

bback = bray + bsoil = 10 + bsoil , 

Where 1 10 − bray = Mm and bsoil represents the extinction for all particulates in the 

background (hygroscopic or non-hygroscopic). 

Hence, 

1 11.38 − bsoil = Mm

And since the extinction coefficient for soil Csoil is 1.0, the monthly background 

concentration for soil (BKSOIL) to be put in CALPOST is 11.38μg/m3

 for every month. 

Indeed, 

bsoil = Csoil ⋅ BKSOIL

Table 4-3 provides the background soil values used in the CALPOST processing for the 5 

Class I areas within the 300 km circle around the facility to be analyzed while Table 4-4 

provides the monthly f(rh) values based on the centroid of the Class I area as required for 

application of Method 6. The monthly f(RH) values for each month are extracted from 

Appendix A of Guidance for Estimating Natural Visibility Conditions Under the Regional 

Haze Program (September 2003). 

Pre-Hearing Draft

Regional Haze SIP for TN Class I Areas

Appendix L.8 - 155

January 18, 2008
Air Quality Modeling Methodology 4-13 

While, the highest predicted light extinction change value expressed in deciviews was 

compared to the threshold value of 0.5 deciviews for the screening run, the 8th highest (98th

percentile) predicted light extinction change is now compared to the threshold value of 0.5 

deciview for the refined run. 

CALPOST Method 8 is also used to compute the extinction change in deciviews. This 

method is an implementation of the new IMPROVE algorithm. It provides a better 

correspondence between the measured visibility and that calculated from pollutant 

concentrations simulated by a model. A description of this method is provided in Appendix 

A. For CALPOST Method 8 option, the ratio NO2/NOx is set to 1.0. The extinction due to 

Rayleigh scattering is set to 11Mm-1 for all the Class I areas, except Shining Rock, where it 

is set to 10 Mm-1. The sea salt background concentration for all year is set to 0.03 μg/m3

 for 

Cohutta W, Shining Rock W and Joyce-Kilmer/ Slickrock W and to 0.02 μg/m3

 at Great 

Smoky Mountains NP and Linville Gorge W. The all year background concentration is set 

for every Class I area to 0.23 μg/m3

 for SO4, 0.1 μg/m3 for NO3, 3.0 μg/m3 for PMC, 1.8 

μg/m3

 for OC, 0.5 μg/m3 for SOIL and 0.02 μg/m3 for EC according to the document “A 

postprocessor for Recalculating CALPOST Visibility Outputs with the New IMPROVE 

Algorithm”, October 14, 2006 by Ivar Tombach. 

Pre-Hearing Draft

Regional Haze SIP for TN Class I Areas

Appendix L.8 - 156

January 18, 2008
Air Quality Modeling Methodology 4-14 

Table 4-3. Summary of Natural Background. 

Class I area 

Annual bext 

(Mm-1) 

Annual HI 

(dv) 

Bsoil 

(Mm-1) 

Great Smoky 

Mountains NP 21.38 7.60 11.38 

Linville Gorge W 21.36 7.59 11.36 

Shining Rock W 21.40 7.61 11.40 

Joyce-Kilmer/ 

SlickRock W 21.40 7.61 11.40 

Cohutta W 21.38 7.60 11.38 

Source: Guidance for Estimating Natural Visibility Conditions Under the Regional Haze Program (September 2003), Appendix B. 

Table 4-4. Monthly Site-Specific f(RH) Values Based on the Centroid of the Area, for Visibility 

Methods 6 and 8 Applications.

Class I area Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec 

Great Smoky 

Mountains NP 

3.3 3.0 2.9 2.7 3.2 3.9 3.8 4.0 4.2 3.8 3.3 3.4 

Linville Gorge W 3.3 3.0 3.0 2.7 3.3 3.9 4.1 4.5 4.4 3.7 3.2 3.4 

Shining Rock W 3.3 3.0 2.9 2.7 3.4 3.9 4.1 4.5 4.4 3.8 3.3 3.4 

Joyce Kilmer/ 

SlickRock W 

3.3 3.1 2.9 2.7 3.3 3.8 4.0 4.2 4.2 3.8 3.3 3.5 

Cohutta W 3.3 3.1 3.0 2.8 3.4 3.8 4.0 4.2 4.2 3.8 3.4 3.5 

Source: Guidance for Estimating Natural Visibility Conditions Under the Regional Haze Program (September 2003), Appendix A, 

Table A-3.

Pre-Hearing Draft

Regional Haze SIP for TN Class I Areas

Appendix L.8 - 157

January 18, 2008
Air Quality Modeling Methodology 5-1 

5. RESULTS 

The results of the initial base case visibility impact analysis using CALPOST Method 6 for 

Alcoa South Plant in Tennessee are summarized in the three following tables, Table 5-1 for 

year 2001, Table 5-2 for year 2002 and Table 5-3 for year 2003. Since this is a refined 

analysis run, the 8th highest (98th percentile) simulated light extinction changes are 

compared to the threshold value of 0.5 deciview for all five Class I areas. 

For Linville Gorge and Shining Rock Wilderness Areas when using CALPOST Method 6, 

the highest, second or third highest change in light extinction is below the 0.5 deciview 

threshold. For Cohutta wilderness, the 5th highest change in light extinction in 2001 and 

2002 and the 7th highest change in light extinction in 2003 are below the 0.5 deciview 

threshold. The three Class I areas are also below the visibility significance threshold of 0.5 

dv change at the 98th percentile level when CALPOST Method 8 is applied (Tables 5-4 to 5-

6). So, these three Class I areas (Linville Gorge, Shining Rock and Cohutta Wilderness 

Areas) meet the standard threshold for the initial base case run and no further analysis 

implying BART control scenarios need to be applied at these three Class I areas. 

However, Great Smoky Mountains National Park and Joyce-Kilmer/ Slickrock wilderness 

area exceed the 0.5 dv change threshold for all three years. Joyce-Kilmer/ Slickrock is 

below the threshold for 2001 when CALPOST Method 8 is applied (Tables 5-4 to 5-6). For 

these two Class I areas, a BART control scenario analysis is required. An evaluation of the 

effect of BART controls at the facility is analyzed for these two Class I areas. 

An additional scenario is presented to estimate the effect of SO2 controls on the change in 

visibility impact due to this facility. This scenario, described in Section 2.2, is using wet 

scrubbers. The CALPOST Method 6 results for this scenario are summarized in Tables 5-7 

to 5-9 for years 2001, 2002, 2003 respectively. Joyce-Kilmer/ Slickrock Wilderness 

impacts with controls are below the 0.5 dv change threshold for all three years. Impacts at 

the Great Smoky Mountain National Park exceed the threshold when CALPOST Method 6 

is applied. The results using the more refined CALPOST Method 8 for the wet scrubber 

scenario and for all three years are summarized in Tables 5-10 to 5-12. Impacts at the 

Joyce-Kilmer/ Slickrock Wilderness Area are below the 0.5 dv change threshold for all 

three years. The impacts at the Great Smoky Mountain National Park is below the 

threshold for 2002 but above for 2001 and 2003. 

Tables 5-13 and 5-14 summarizes the compliance for the base case scenario and for the wet 

scrubber scenario respectively. Table 5-15 gives the source contribution for the initial run 

at the 98th percentile light extinction change using CALPOST Method 6. 

In conclusion, the impacts at three Class I areas, Linville Gorge Wilderness, Shining Rock 

Wilderness and Cohutta Wilderness are below the significant threshold for the base case 

runs and did not require any more control modeling. The impacts at the Joyce-Kilmer/ 

Slickrock Wilderness are below the 0.5 threshold for the wet scrubber control scenario for 

all three years with both CALPOST Method 6 and Method 8. The impacts at the Great 

Pre-Hearing Draft

Regional Haze SIP for TN Class I Areas

Appendix L.8 - 158

January 18, 2008
Air Quality Modeling Methodology 5-2 

Smoky Mountains National Park are below the 0.5 dv threshold 2002 for the wet scrubber 

control scenario with the use of CALPOST Method 8, but above the threshold for 2001 and 

2003. 

Pre-Hearing Draft

Regional Haze SIP for TN Class I Areas

Appendix L.8 - 159

January 18, 2008
Air Quality Modeling Methodology 5-3 

Table 5-1. Results for Visibility Impact using Method 6 – Base Case Run - Year 2001

Class I area 

Highest 

Extinction 

Change (dv) 

Receptor location day No. of days 

above 0.5dv 

No. of days 

above 1dv 

Great Smoky Mountains 

2.227 

2.121 

1.687 

1.525 

1.424 

1.356 

1.342 

1.273

1175.701; -398.594 

1176.920; -396.551 

1175.435; -396.767 

1179.623; -394.292 

1175.435; -396.767 

1181.107; -394.076 

1170.121; -412.460 

1178.139; -394.509 

365 0h 

360 0h 

231 0h 

221 0h 

192 0h 

226 0h 

224 0h 

33 0h 

58 13

Linville Gorge 0.385 1345.583; -336.544 189 0h 0 0 

Shining Rock 0.462 1272.465; -405.445 257 0h 0 0 

Joyce-Kilmer/ SlickRock 

1.503 

1.109 

0.755 

0.740 

0.711 

0.589 

0.588 

0.511 

1167.847; -423.047 

1167.935; -418.371 

1169.555; -419.071 

1172.400; -417.727 

1170.167; -418.050 

1167.935; -418.371 

1167.935; -418.371 

1172.400; -417.727 

224 0h 

172 0h 

20 0h 

221 0h 

13 0h 

204 0h 

130 0h 

260 0h 

8 2 

Cohutta 

0.809 

0.656 

0.533 

0.509 

0.499 

1132.719; -476.504 

1119.974; -478.260 

1128.844; -476.107 

1119.974, -478.260 

1125.861, -493.304 

224 0h 

346 0h 

161 0h 

11 0h 

261 0h 

4 0 

Pre-Hearing Draft

Regional Haze SIP for TN Class I Areas

Appendix L.8 - 160

January 18, 2008
Air Quality Modeling Methodology 5-4 

Table 5-2. Results for Visibility Impact using Method 6 –Base Case Run - Year 2002 

Class I area 

Highest 

Extinction 

Change (dv) 

Receptor location day No. of days 

above 0.5dv 

No. of days 

above 1dv 

Great Smoky Mountains 

1.959 

1.933 

1.520 

1.518 

1.403 

1.232 

1.224 

1.189

1175.435; -396.767 

1192.709; -390.508 

1192.709; -390.508 

1181.107, -394.076 

1178.139; -394.509 

1178.404; -396.335 

1198.372; -387.805 

1178.139; -394.509

199 0h 

285 0h 

247 0h 

295 0h 

196 0h 

336 0h 

197 0h 

238 0h

47 15

Linville Gorge 0.446 1347.717; -349.286 236 0h 0 0 

Shining Rock 

0.567 

0.530 

0.497 

1265.287; -413.110 

1272.465; -405.445 

1276.416, -416.040 

197 0h 

301.0h 

260 0h 

2 0 

Joyce-Kilmer/ Slickrock 

1.140 

0.982 

0.940 

0.799 

0.723 

0.701 

0.694 

0.677

1167.935; -418.371 

1167.979; -423.961 

1167.935; -418.371 

1167.935; -418.371 

1167.935; -418.371 

1167.935; -418.371 

1170.912; -417.942 

1167.935; -418.371 

297 0h 

198 0h 

321 0h 

298 0h 

197 0h 

248 0h 

54 0h 

183 h0 

17 1 

Cohutta 

0.720 

0.703 

0.633 

0.632 

0.413 

1119.974; -478.260 

1119.974; -478.260 

1119.974; -478.260 

1119.974; -478.260

1119.974; -478.260 

296 0h 

301 0h 

184 0h 

239 0h 

241 0h 

4 0 

Pre-Hearing Draft

Regional Haze SIP for TN Class I Areas

Appendix L.8 - 161

January 18, 2008
Air Quality Modeling Methodology 5-5 

Table 5-3. Results for Visibility Impact using Method 6 – Base Case Run - Year 2003

Class I area 

Highest 

Extinction 

Change (dv) 

Receptor location day No. of days 

above 0.5dv 

No. of days 

above 1dv 

Great Smoky Mountains 

3.011 

2.420 

2.174 

1.997 

1.972 

1.946 

1.928 

1.620

1175.435; -396.767 

1178.139; -394.509 

1175.435; -396.767 

1178.139; -394.509 

1169.066; -405.151 

1178.139; -394.509 

1171.774; -402.894 

1179.623; -394.292

224 0h 

238 0h 

291 0h 

264 0h 

223 0h 

12 0h 

179 0h 

76 0h

63 24

Linville Gorge 0.747 

0.475 

1347.717; -349.286 

1345.583; -336.544 

60 0h 

182 0h 

1 0 

Shining Rock 0.359 1276.416; -416.040 201 0h 0 0 

Joyce-Kilmer/ Slickrock 

1.457 

1.310 

1.257 

1.248 

1.140 

0.979 

0.932 

0.837

1167.935; -418.371 

1167.935; -418.371 

1170.912; -417.942 

1172.400; -417.727 

1172.400; -417.727 

1167.935; -418.371 

1172.400; -417.727 

1170.167; -418.050

223 0h 

291 0h 

239 0h 

224 0h 

179 0h 

185 0h 

238 0h 

236 0h

23 5

Cohutta 

0.784 

0.709 

0.616 

0.509 

0.507 

0.504 

0.492 

1127.219; -475.399 

1132.719; -476.504 

1119.974; -478.260

1131.482; -484.136 

1132.719, -476.504 

1126.469, -475.503 

1119.974, -478.260 

253 0h 

239 0h 

254 0h 

221 0h 

199 0h 

231 0h 

206 0h 

6 0 

Pre-Hearing Draft

Regional Haze SIP for TN Class I Areas

Appendix L.8 - 162

January 18, 2008
Air Quality Modeling Methodology 5-6 

Table 5-4. Results for visibility impact using Method 8 –Base Case run - year 2001 

Class I area 

Highest 

Extinction 

Change (dv) 

Receptor location day No. of days 

above 0.5dv 

No. of days 

above 1dv 

Great Smoky Mountains 

1.956 

1.745 

1.384 

1.244 

1.157 

1.123 

1.106 

1.092

1175.701; -398.594 

1176.920; -396.551 

1175.435; -396.767 

1179.623; -394.292 

1175.435; -396.767 

1178.139; -394.509 

1181.107; -394.076 

1170.121; -412.460

365 0h 

360 0h 

231 0h 

221 0h 

192 0h 

33 0h 

226 0h 

224 0h

38 8

Linville Gorge 0.301 1345.583; -336.544 189 0h 0 0 

Shining Rock 0.375 1272.465; -405.445 257 0h 0 0 

Joyce-Kilmer/ SlickRock 

1.242 

0.896 

0.605 

0.593 

0.554 

0.474 

1167.847; -423.047 

1167.935; -418.371 

1172.400; -417.727 

1169.555; -419.071 

1170.167; -418.050 

1167.935, -418.371 

224 0h 

172 0h 

221 0h 

20 0h 

13 0h 

204 0h 

5 1 

Cohutta 

0.660 

0.518 

0.427 

1132.719; -476.504 

1119.974; -478.260 

1128.844, -476.107 

224 0h 

346 0h 

161 0h 

2 0 

Pre-Hearing Draft

Regional Haze SIP for TN Class I Areas

Appendix L.8 - 163

January 18, 2008
Air Quality Modeling Methodology 5-7 

Table 5-5. Results for visibility impact using Method 8 –Base Case run - year 2002 

Class I area 

Highest 

Extinction 

Change (dv) 

Receptor location day No. of days 

above 0.5dv 

No. of days 

above 1dv 

Great Smoky Mountains 

1.604 

1.578 

1.256 

1.240 

1.138 

1.092 

0.990 

0.966

1175.435; -396.767 

1192.709; -390.508 

1192.709; -390.508 

1181.107, -394.076 

1178.139; -394.509 

1178.404; -396.335 

1198.372; -387.805 

1178.139; -394.509

199 0h 

285 0h 

247 0h 

295 0h 

196 0h 

336 0h 

197 0h 

238 0h

40 6

Linville Gorge 0.363 1347.717; -349.286 236 0h 0 0 

Shining Rock 0.463 1265.287; -413.110 197 0h 0 0 

Joyce-Kilmer/ SlickRock 

0.921 

0.796 

0.754 

0.643 

0.584 

0.573 

0.567 

0.549 

1167.935; -418.371 

1167.979; -423.961 

1167.935; -418.371 

1167.935; -418.371 

1167.935; -418.371 

1167.935; -418.371 

1170.912; -417.942 

1167.935; -418.371 

297 0h 

198 0h 

321 0h 

298 0h 

197 0h 

248 0h 

54 0h 

245 0h 

10 0 

Cohutta 

0.577 

0.564 

0.514 

0.508 

0.335 

1119.974; -478.260 

1119.974; -478.260 

1119.974; -478.260 

1119.974; -478.260 

1119.974; -478.260 

296 0h 

301 0h 

239 0h 

184 0h 

241 0h 

4 0 

Pre-Hearing Draft

Regional Haze SIP for TN Class I Areas

Appendix L.8 - 164

January 18, 2008
Air Quality Modeling Methodology 5-8 

Table 5-6. Results for visibility impact using Method 8 – Base Case run - year 2003

Class I area 

Highest 

Extinction 

Change (dv) 

Receptor location day No. of days 

above 0.5dv 

No. of days 

above 1dv 

Great Smoky Mountains 

2.508 

1.998 

1.782 

1.706 

1.659 

1.622 

1.550 

1.310

1175.435; -396.767 

1178.139; -394.509 

1175.435; -396.767 

1178.139; -394.509 

1178.139; -394.509 

1169.066; -405.151 

1171.774; -402.894 

1181.107; -394.076

224 0h 

238 0h 

291 0h 

12 0h 

264 0h 

223 0h 

179 0h 

251 0h

49 20

Linville Gorge 0.575 

0.370 

1347.717; -349.286 

1345.583; -336.544 

60 0h 

182 0h 

1 0 

Shining Rock 0.293 1276.416; -416.040 201 0h 0 0 

Joyce-Kilmer/ SlickRock 

1.205 

1.061 

1.035 

1.029 

0.923 

0.793 

0.764 

0.686

1167.935; -418.371 

1167.935; -418.371 

1170.912; -417.942 

1172.400; -417.727 

1172.400; -417.727 

1167.935; -418.371 

1172.400; -417.727 

1170.167; -418.050

223 0h 

291 0h 

239 0h 

224 0h 

179 0h 

185 0h 

238 0h 

236 0h

16 4

Cohutta 

0.639 

0.577 

0.501 

0.414 

1127.219; -475.399 

1132.719; -476.504 

1119.974; -478.260 

1131.482, -484.260 

253 0h 

239 0h 

254 0h 

221 0h 

3 0 

Pre-Hearing Draft

Regional Haze SIP for TN Class I Areas

Appendix L.8 - 165

January 18, 2008
Air Quality Modeling Methodology 5-9 

Table 5-7. Results for visibility impact using Method 6 – Wet Scrubber scenario - year 2001

Class I area 

Highest 

Extinction 

Change (dv) 

Receptor location day No. of days 

above 0.5dv 

No. of days 

above 1dv 

Great Smoky Mountains 

2.053 

1.169 

0.973 

0.923 

0.803 

0.800 

0.740 

0.691 

1175.701; -398.594 

1178.139; -394.509 

1178.139; -394.509 

1178.139; -396.509 

1176.920; -396.551 

1172.995; -400.852 

1176.920; -396.551 

1176.920; -396.551 

365 0h 

33 0h 

360 0h 

66 0h 

9 0h 

82 0h 

1 0h 

54 0h 

16 2 

Joyce-Kilmer/ Slickrock 0.419 1167.935; -418.371 224 0h 0 0 

Table 5-8. Results for visibility impact using Method 6 – Wet Scrubber scenario - year 2002

Class I area 

Highest 

Extinction 

Change (dv) 

Receptor location day No. of days 

above 0.5dv 

No. of days 

above 1dv 

Great Smoky Mountains 

1.108 

0.865 

0.671 

0.666 

0.644 

0.629 

0.530 

0.520 

1176.920; -396.551 

1181.107; -394.076 

1169.066; -405.151 

1169.066; -405.151 

1175.435; -396.767 

1192.709, -390.508 

1174.216, -398.810 

1178.139, -394.509

336 h0 

295 h0 

321 h0 

54 h0 

199 h0 

285 h0 

13 h0 

12 h0

10 1 

Joyce-Kilmer/ Slickrock 0.478 1170.167; -418.050 321 h0 0 0 

Table 5-9. Results for visibility impact using Method 6 – Wet Scrubber scenario - year 2003

Class I area 

Highest 

Extinction 

Change (dv) 

Receptor location day No. of days 

above 0.5dv 

No. of days 

above 1dv 

Great Smoky Mountains 

1.858 

1.089 

1.067 

0.917 

0.849 

0.820 

0.709 

0.702 

1179.889; -396.119 

1174.216; -398.810 

1176.920; -396.551 

1174.216; -398.810 

1175.435; -396.767 

1172.995; -400.852 

1169.066; -405.151 

1175.435; -396.767 

12 h0 

24 h0 

83 h0 

224 h0 

16 h0 

179 h0 

223 h0 

291 h0 

18 3 

Joyce-Kilmer/ Slickrock 0.432 1167.935; -418.371 223 h0 0 0 

Pre-Hearing Draft

Regional Haze SIP for TN Class I Areas

Appendix L.8 - 166

January 18, 2008
Air Quality Modeling Methodology 5-10 

Table 5-10. Results for visibility impact using Method 8 – Wet Scrubber scenario - year 2001

Class I area 

Highest 

Extinction 

Change (dv) 

Receptor location day No. of days 

above 0.5dv 

No. of days 

above 1dv 

Great Smoky Mountains 

1.895 

1.082 

0.872 

0.870 

0.765 

0.743 

0.649 

0.598

1175.701; -398.594 

1178.139; -394.509 

1178.139; -394.509 

1178.139; -394.509 

1176.920; -396.551 

1172.995; -400.852 

1176.920; -396.551 

1178.404; -396.335 

365 0h 

33 0h 

66 0h 

360 0h 

9 0h 

82 0h 

54 0h 

86 0h 

13 2 

Joyce-Kilmer/ Slickrock 0.350 1167.935; -418.371 224 0h 0 0 

Table 5-11. Results for visibility impact using Method 8 – Wet Scrubber scenario - year 2002

Class I area 

Highest 

Extinction 

Change (dv) 

Receptor location day No. of days 

above 0.5dv 

No. of days 

above 1dv 

Great Smoky Mountains 

1.018 

0.722 

0.612 

0.600 

0.548 

0.522 

0.477 

1176.920; -396.551 

1181.107, -394.076 

1169.066, -405.151 

1169.066, -405.151 

1175.435; -396.767 

1192.709, -390.508 

1178.139, -394.509 

336 h0 

295 h0 

54 h0 

321 h0 

199 h0 

285 h0 

12 h0 

6 1 

Joyce-Kilmer/ Slickrock 0.419 1170.167; -418.050 320 h0 0 0 

Table 5-12. Results for visibility impact using Method 8 – Wet Scrubber scenario - year 2003

Class I area 

Highest 

Extinction 

Change (dv) 

Receptor location day No. of days 

above 0.5dv 

No. of days 

above 1dv 

Great Smoky Mountains 

1.739 

1.015 

0.997 

0.790 

0.770 

0.702 

0.596 

0.585 

1179.889, -396.119 

1174.216, -398.810 

1176.920, -396.551 

1175.435, -396.767 

1174.216, -398.810 

1172.995, -400.852 

1169.066, -405.151 

1175.435, -396.767 

12 h0 

24 h0 

83 h0 

16 h0 

224 h0 

179 h0 

223 h0 

291 h0 

13 2 

Joyce-Kilmer/ Slickrock 0.362 1167.935, -418.371 223 h0 0 0 

Pre-Hearing Draft

Regional Haze SIP for TN Class I Areas

Appendix L.8 - 167

January 18, 2008
Air Quality Modeling Methodology 5-11 

Table 5-13. Summary Table of Results at the 98th percentile change in light extinction for the Base 

Case Runs for Method 6 and Method 8

 Values > 0.5 dv 

for Great Smoky 

Mountain NP 

Values > 0.5 dv 

for Linville 

Gorge W. 

Values > 0.5 dv 

for Shining Rock 

W. 

Values > 0.5 for 

Joyce-Kilmer/ 

SlickRock W. 

Values > 0.5 for 

Cohutta W. 

2001 No Yes Yes No Yes 

Initial Run – Method 6 2002 No Yes Yes No Yes 

2003 No Yes Yes No Yes 

2001 No Yes Yes Yes Yes 

Initial Run – Method 8 2002 No Yes Yes No Yes 

2003 No Yes Yes No Yes 

Table 5-14. Summary Table of Results at the 98th percentile change in light extinction for the control 

scenario for Method 6 and Method 8

 Values > 0.5 dv for 

Great Smoky Mountain NP 

Values > 0.5 for 

Joyce-Kilmer/ SlickRock W. 

2001 No Yes 

Wet Scrubber – Method 6 2002 No Yes 

2003 No Yes 

2001 No Yes 

Wet Scrubber – Method 8 2002 Yes Yes 

2003 No Yes 

Pre-Hearing Draft

Regional Haze SIP for TN Class I Areas

Appendix L.8 - 168

January 18, 2008
Air Quality Modeling Methodology 5-12 

Table 5-15. Base Case Run - Source group and species contributions at the 8th highest light extinction change (98th p

Smoky Mountains National Park using CALPOST Method 6. 

Year Soure Group Contrib. to 

Modeled Ext

Total Bext SO4 NO3 PM_Fine PM_Coarse Organics E. Carbon SO4 

Change(%) 1/Mm 1/Mm 1/Mm 1/Mm 1/Mm 1/Mm 1/Mm % 

Initial run, receptor 541, day ending 33 h0

2001 All Groups 100 2.903 0.648 0.153 0.317 0.146 1.639 0 22.32 2001 Potrooms L01-L04 53.88 1.564 0.009 0 0.297 0.123 1.135 0 0.58 2001 A398 P01-P04 29.90 0.868 0.466 0.007 0.006 0.007 0.382 0 53.69 2001 Bake P05-P10 13.99 0.406 0.173 0.107 0.003 0.003 0.121 0 42.61 22001 Crusher P11 0.10 0.003 0 0 0 0.003 0 0 0.00 2001 Reclamation Delacquering P12 1.17 0.034 0 0.03 0.002 0.002 0 0 0.00 82001 Melting Furnace P13-14 0.96 0.028 0 0.009 0.009 0.009 0.001 0 0.00 3

Initial run, receptor 541, day ending 238 h0

2002 All Groups 100 2.699 2.409 0.004 0.031 0.014 0.24 0 89.26 2002 Potrooms L01-L04 5.45 0.147 0.012 0 0.026 0.01 0.099 0 8.16 2002 A398 P01-P04 80.66 2.177 2.051 0.001 0.002 0.002 0.122 0 94.21 2002 Bake P05-P10 13.56 0.366 0.344 0.002 0.001 0 0.019 0 93.99 2002 Crusher P11 0.04 0.001 0 0 0 0.001 0 0 0.00 2002 Reclamation Delacquering P12 0.15 0.004 0.002 0.001 0 0 0 0 50.00 22002 Melting Furnace P13-14 0.19 0.005 0 0 0.002 0.002 0 0 0.00 

Initial run, receptor 542, day ending 76 h0

2003 All Groups 100 3.76 3.496 0.022 0.024 0.012 0.207 0 92.98 2003 Potrooms L01-L04 2.87 0.108 0.013 0 0.018 0.006 0.071 0 12.04 2003 A398 P01-P04 76.41 2.873 2.765 0.001 0.002 0.001 0.104 0 96.24 2003 Bake P05-P10 20.32 0.764 0.715 0.016 0.001 0.001 0.031 0 93.59 2003 Crusher P11 0.03 0.001 0 0 0 0.001 0 0 0.00 2003 Reclamation Delacquering P12 0.16 0.006 0.002 0.003 0 0 0 0 33.33 52003 Melting Furnace 0.19 0.007 0 0.001 0.003 0.002 0 0 0.00 

Species Contribution to Modeled Extinction Coefficient in 1/Mm Percentage of 

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Table 5-16. Base Case Run - Source group and species contributions at the 8th highest light extinction change (98th p

Smoky Mountains National Park using CALPOST Method 8. 

Year Soure Group Contrib. to 

Modeled Ext

Total Bext SO4 NO3 PM_Fine PM_Coarse Organics NO2 SO4 

Change(%) 1/Mm 1/Mm 1/Mm 1/Mm 1/Mm 1/Mm 1/Mm % 

Initial run, receptor 108, day begining 223 h0

2001 All Groups 100 2.611 2.396 0.004 0.032 0.011 0.167 0.001 91.77 2001 Potrooms L01-L04 5.71 0.149 0.021 0 0.028 0.008 0.092 0 14.09 2001 A398 P01-P04 80.66 2.106 2.038 0 0.001 0.001 0.065 0 96.77 2001 Bake P05-P10 13.18 0.344 0.331 0.002 0 0 0.01 0 96.22 2001 Crusher P11 0.00 0 0 0 0 0 0 0 0.00 2001 Reclamation Delacquering P12 0.11 0.003 0.002 0.001 0 0 0 0 66.67 2001 Melting Furnace P13-14 0.11 0.003 0 0 0.002 0.001 0 0 0.00 

Initial run, receptor 541, day begining 237 h0

2002 All Groups 100 2.296 2.041 0.004 0.031 0.014 0.204 0.002 88.89 2002 Potrooms L01-L04 5.66 0.13 0.01 0 0.026 0.01 0.084 0 7.69 2002 A398 P01-P04 80.31 1.844 1.736 0 0.002 0.002 0.103 0 94.14 2002 Bake P05-P10 13.50 0.31 0.29 0.002 0.001 0 0.016 0.001 93.55 2002 Crusher P11 0.04 0.001 0 0 0 0.001 0 0 0.00 2002 Reclamation Delacquering P12 0.17 0.004 0.001 0.001 0 0 0 0.001 25.00 2002 Melting Furnace P13-14 0.22 0.005 0 0 0.002 0.002 0 0 0.00 

Initial run, receptor 543, day begining 250 h0

2003 All Groups 100 3.209 2.782 0.022 0.052 0.026 0.317 0.009 86.69 2003 Potrooms L01-L04 6.86 0.22 0.014 0 0.044 0.018 0.144 0 6.36 2003 A398 P01-P04 74.60 2.394 2.239 0.002 0.003 0.003 0.146 0.001 93.53 2003 Bake P05-P10 17.61 0.565 0.52 0.013 0.001 0.001 0.026 0.005 92.04 2003 Crusher P11 0.03 0.001 0 0 0 0.001 0 0 0.00 2003 Reclamation Delacquering P12 0.37 0.012 0.002 0.006 0.001 0.001 0 0.003 16.67 2003 Melting Furnace 0.31 0.01 0 0.002 0.004 0.003 0 0.001 0.00 

Species Contribution to Modeled Extinction Coefficient in 1/Mm Percentage 

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References 6-1 

6. REFERENCES 

Allwine, K.J. and C.D. Whiteman, 1985: MELSAR: A mesoscale air quality model for 

complex terrain: Volume 1--Overview, technical description and user's guide. 

Pacific Northwest Laboratory, Richland, Washington. 

Carson, D.J., 1973: The development of a dry, inversion-capped, convectively unstable 

boundary layer. Quart. J. Roy. Meteor. Soc., 99, 450-467. 

Douglas, S. and R. Kessler, 1988: User's guide to the diagnostic wind model. California 

Air Resources Board, Sacramento, CA. 

Earth Tech, 2001. Mustang Energy Company, L. L. C. Mustang Electric Generating Station, 

Unit # 1, McKinley County, New Mexico. Class I Air Quality Modeling Protocol, 

Concord, MA. 

FLAG, 2000. Federal Land Manager' Air Quality Related Values Workgroup (FLAG). 

Phase I Report. U.S. Forest Service, National Park Service, U.S. Fish and Wildlife 

Service. 

Holtslag, A.A.M. and A.P. van Ulden, 1983: A simple scheme for daytime estimates of the 

surface fluxes from routine weather data. J. Clim. and Appl. Meteor., 22, 517-529. 

Liu, M.K. and M. A. Yocke, 1980: Siting of wind turbine generators in complex terrain. J. 

Energy, 4, 10:16. 

Mahrt, L., 1982: Momentum Balance of Gravity Flows. Journal of Atmos. Sci., 39, 2701-

2711. 

Maul, P.R., 1980: Atmospheric transport of sulfur compound pollutants. Central 

Electricity Generating Bureau MID/SSD/80/0026/R. Nottingham, England. 

O'Brien, J.J., 1970: A note on the vertical structure of the eddy exchange coefficient in the 

planetary boundary layer. J. Atmos. Sci., 27, 1213-1215. 

Perry, S.G., D.J. Burns, L.H. Adams, R.J. Paine, M.G. Dennis, M.T. Mills, D.G. Strimaitis, 

R.J. Yamartino, E.M. Insley, 1989: User's Guide to the Complex Terrain Dispersion Model 

Plus Algorithms for Unstable Situations (CTDMPLUS) Volume 1: Model 

Description and User Instructions. EPA/600/8-89/041, U.S. Environmental 

Protection Agency, Research Triangle Park, NC. 

Scire, J.S. and F.R. Robe, 1997: Fine-Scale Application of the CALMET Meteorological 

Model to a Complex Terrain Site. Paper 97-A1313. Air & Waste Management 

Association 90th Annual Meeting & Exhibition, Toronto, Ontario, Canada. 8-13 

June 1997. 

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References 6-2 

Scire, J.S., D.G. Strimaitis, and R.J. Yamartino, 2000a: A User’s Guide for the CALPUFF 

Dispersion Model (Version 5). Earth Tech, Inc., Concord, MA 

Scire, J.S., F.R. Robe, M.E. Fernau, and R.J. Yamartino, 2000b: A User’s Guide for the 

CALMET Meteorological Model (Version 5). Earth Tech, Inc., Concord, MA. 

Smrz, R., 1998: Updated Class I Receptor List and SLVs. Tennessee Department of 

Environment and Conservation, Division of Air Pollution Control, Nashville, TN. 

April 6, 1998. 

Stelson, A. W. and J. H. Seinfeld, 1982: Relative humidity and temperature dependence of 

the ammonium nitrate dissociation constant. Atmos. Environ., 16, 983-992. 

U.S. Department of Agriculture (USDA) Forest Service, Screening Methodology for 

Calculating ANC Change to High Elevation Lakes, User’s Guide dated January 

2000. 

U.S. Environmental Protection Agency (EPA), 1998: Interagency Workgroup on Air 

Quality Modeling (IWAQM), Phase 2 Report: Summary Report and 

Recommendation for Modeling Long Range Transport and Impacts on Regional 

Visibility. EPA-454/R-98-019. 

U.S. Environmental Protection Agency (EPA), 2000: Federal Register Notice dated April 

21, 2001. 

U.S., Environmental Protection Agency (EPA), 2003: Guidance for Estimating Natural 

Visibility Conditions Under the Regional Haze Program. EPA-454/B-03-005, 

September 2003. 

VISTAS, 2005: Protocol for the Application of the CALPUFF Model for Analysis of Best 

Available Retrofit Technology (BART). 

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Appendix A 

CALPOST Visibility Method 8 

The revised visibility algorithm developed for the IMPROVE Steering Committee 

(IMPROVE 2005) has been implemented in CALPOST. It differs from the previous 

IMPROVE algorithm in 6 areas: 

1. Extinction efficiencies of sulfates, nitrates, and organics vary with concentration, 

as there are distinct efficiencies for "small" and "large" particles and the ratio of 

small-to-large particle fraction decreases as the concentration increases. 

Furthermore, the extinction efficiency for sulfates no longer equals that for 

nitrates. 

2. A separate hygroscopic humidity enhancement factor curve is prescribed for 

"small" and "large" particles, fS(RH) and fL(RH). These curves apply to sulfates 

and nitrates. 

3. Light extinction due to scattering by sea salt (with its own hygroscopic humidity 

enhancement factor fSS(RH)) is included. 

4. Light absorption by NO2 gas is included in the extinction. 

5. Background particulate organic matter concentration is taken to be 1.8 times 

measured organic carbon concentrations. 

6. Rayleigh scattering extinction varies with site elevation and mean temperature. 

Items 5 and 6 remain direct inputs to CALPOST, and require no structural changes to the 

postprocessor. The user must confirm that appropriate values are provided. 

Item 4, the introduction of light extinction due to NO2 gas absorption, has been added to 

CALPOST as a discrete component independent of the visibility method chosen. New 

control file inputs associated with NO2 are: 

 Modeled species to be included in computing the light extinction 

 Include NO2 absorption? (LVNO2) -- Default: F ! LVNO2 = T ! 

 With Visibility Method 8 -- Default: T 

 Source of NO2 (when LVNO2=T) may be from CALPUFF NO2 concentrations 

 and from a fraction of CALPUFF NOx concentrations. Specify the 

 fraction of NOx that is treated as NO2. 

 (FNO2NOX) -- Default: 1.0 ! FNO2NOX = 0.75 ! 

Extinction Efficiency (1/Mm per ug/m**3) 

---------------------------------------- 

 NO2 GAS (EENO2) -- Default: .17 ! EENO2 = .17 ! 

Items 1 through 3 are implemented as visibility method 8 in CALPOST, along with the 

specific choice of the new f(RH) curves. Selection of the revised IMPROVE algorithm 

requires the following new control file selections: 

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 Particle growth curve f(RH) for hygroscopic species 

 (MFRH) -- Default: 2 ! MFRH = 4 ! 

 1 = IWAQM (1998) f(RH) curve (originally used with MVISBK=1) 

 2 = FLAG (2000) f(RH) tabulation 

 3 = EPA (2003) f(RH) tabulation 

 4 = IMPROVE (2006) f(RH) tabulations for sea salt, and for 

 small and large SULFATE and NITRATE particles; 

 Used with Visibility Method 8 (MVISBK = 8) 

 Method used for background light extinction 

 (MVISBK) -- Default: 2 ! MVISBK = 8 ! 

 1 = Supply single light extinction and hygroscopic fraction 

 2 = Compute extinction from speciated PM measurements (A) 

 3 = Compute extinction from speciated PM measurements (B) 

 4 = Read hourly transmissometer background extinction measurements 

 5 = Read hourly nephelometer background extinction measurements 

 6 = Compute extinction from speciated PM measurements 

 7 = Use observed weather or prognostic weather information for 

 background extinction during weather events; otherwise, Method 2 

 8 = Compute extinction from speciated PM measurements using the 

 IMPROVE (2006) variable extinction efficiency formulation 

 (MFRH must be set to 4) 

 - Split between small and large particle concentrations of 

 SULFATES, NITRATES, and ORGANICS is a function of concentration 

 and different extinction efficiencies are used for each 

 - Source-induced change in visibility includes the increase in 

 extinction of the background aerosol due to the change in the 

 extinction efficiency that now depends on total concentration. 

 - Fsmall(RH) and Flarge(RH) adjustments for small and large 

 particles are applied to observed and modeled sulfate and 

 nitrate concentrations 

 - Fsalt(RH) adjustment for sea salt is applied to background 

 sea salt concentrations 

 - F(RH) factors are capped at F(RHMAX) 

 - RH for F(RH) may be obtained from hourly data as in Method 2 

 or from the FLAG monthly RH adjustment factor as in Method 6 

 where EPA F(RH) tabulation is used to infer RH. Furthermore, 

 the monthly RH factor may be applied to hourly concentrations 

 or daily concentrations to obtain the 24-hour extinction. 

 These choices are made using the M8_MODE selection. 

 Additional inputs used for MVISBK = 8: 

 -------------------------------------- 

 Extinction coefficients for hygroscopic species (modeled and 

 background) may be computed using hourly RH values and hourly 

 modeled concentrations, or using monthly RH values inferred from 

 the RHFAC adjustment factors and either hourly or daily modeled 

 concentrations. 

 

 (M8_MODE) -- Default: 3 ! M8_MODE= 3 ! 

 

 1 = Use hourly RH values from VISB.DAT file with hourly 

 modeled and monthly background concentrations. 

 2 = Use monthly RHFAC with EPA (2003) f(RH) tabulation 

 with hourly modeled and monthly background concentrations. 

 (VISB.DAT file is NOT needed). 

 3 = Use monthly RHFAC with EPA (2003) f(RH) tabulation 

 with daily modeled and monthly background concentrations. 

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 (VISB.DAT file is NOT needed). 

 Background extinction coefficients are computed from monthly 

 CONCENTRATIONS of sea salt (BKSALT). Month 1 is January. 

 (ug/m**3) 

 (BKSALT) -- No default ! BKSALT= 0.0, 0.0, 0.0, 0.0, 

 0.0, 0.0, 0.0, 0.0, 

 0.0, 0.0, 0.0, 0.0 ! 

 

The last of these selections, M8_MODE, provides options for how concentrations are 

averaged, and how the relative humidity enhancement factors for hygroscopic species are 

determined. M8_MODE has a default value of 3, selecting the use of monthly relative 

humidity factors (RHFAC), and using these with daily modeled concentration averages 

and monthly background concentrations. This default is consistent with an 

implementation of the revised IMPROVE algorithm in the form of a spreadsheet 

processor (Tombach, 2006). 

The revised IMPROVE algorithm models the extinction (1/Mm) as: 

0.17 [ ]

( )

0.6 [ ]

1.7 ( ) [ ]

1 [ ]

10 [ ]

2.8 [ ] 6.1 [ arg ]

2.4 ( ) [ ] 5.1 ( ) [ arg ]

2.2 ( ) [ ] 4.8 ( ) [ arg ]

NO2

Rayleigh scattering site specific

coarse matter

f RH sea salt

fine soil

elemental carbon

small organics l e organics

f RH small nitrate f RH l e nitrate

b f RH small sulfate f RH l e sulfate

SS

S L

ext S L

+ •

+ −

+ •

+ •

+ •

+ •

+ • + •

+ • + •

= • + •

 (1) 

All of the brackets [] denote concentrations in μg/m3

. Note that Tombach (2006) uses an 

extinction efficiency for NO2 of 0.33 (1/Mm)/(ppb), and requires NO2 concentrations in 

ppb. This efficiency is equivalent to 0.17 (1/Mm)/( μg/m3

) at standard pressure and 

20°C. 

Curves of f(RH) for both "small" and "large" particles, and sea salt particles are 

compared to the f(RH) for the EPA(2003) tabulation in Figure 1. 

For sulfates, nitrates, and organics, "small" particles dominate the size distribution at 

small concentrations, and "large" particles dominate the size distribution at large 

concentrations. This is modeled as a simple linear relation from zero to the concentration 

at which the "small" particles essentially vanish, [CV]. Denoting the fraction of the 

concentration [C] (sulfates, nitrates, or organics) made up of "large" particles as FL, and 

the fraction made up of "small" particles as FS, 

 

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S L

V

L

F F

C

C F MIN

= −

=

1.0

) [ ]

[ ] (1.0, (2) 

The vanishing-point concentration [CV] is 20 μg/m3

 for each of these species. The 

corresponding concentrations to be used in Eqn. 1 are 

[ arg ] [ ]

[ ] [ ]

l e F C

small F C

L

S

= •

= • (3) 

Because the extinction efficiency for sulfates, nitrates, or organics depends on the total 

concentration of each, the total light extinction cannot be calculated as the sum of the 

background extinction (without the source contribution) and the source-related extinction 

(without the background contribution). It is not a linear relationship. When source 

emissions increase the concentration at a receptor, the resulting total concentration 

changes the extinction efficiency, which applies to both the source-related concentration 

and the background concentration. The source impact on visibility is computed as the 

difference between the total extinction due to both the source emissions and background 

concentration, bext,T , and the extinction due to background concentrations alone, bext,B. 

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Figure 1. Comparison of the f(RH) extinction enhancement factors for hygroscopic 

particles. The revised IMPROVE visibility algorithm replaces the EPA(2003) 

curve with individual curves for small and large particles, and it introduces a 

curve for fine sea salt particles. 

f(RH) Curves

0

1

2

3

4

5

6

7

8

9

10

0 10 20 30 40 50 60 70 80 90 100

RH

f(RH)

EPA(2003)

Small Particles

Large Particles

Sea Salt

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Appendix C 

WET SCRUBBER ECONOMIC AND ENERGY IMPACT

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Appendix D 

BUSINESS CONFIDENTIAL INFORMATION 

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