Air Dispersion Modeling Guidelines 

For Oklahoma Air Quality Permits 

Prepared by the Engineering Section of the Permitting Unit 

Air Quality Division 

Oklahoma Department of Environmental Quality 

January 2008 

This publication is issued by the Oklahoma Department of Environmental Quality as authorized by Steven A. Thompson, 

Executive Director. Copies have not been printed but are available through the agency web site. Two printout copies have 

been deposited with the Publications Clearinghouse of the Oklahoma Department of Libraries.
Table of Contents

1. INTRODUCTION.......................................................................................... 1

1.1 What is Air Dispersion Modeling ............................................................ 1

1.2 State and Federal Regulations Requiring Modeling.............................. 1

1.3 Levels of Modeling .................................................................................... 2

1.3.1 Screen Modeling........................................................................................ 2

1.3.2 Refined Modeling...................................................................................... 2

1.4 Acceptable Models .................................................................................... 2

1.4.1 SCREEN3 .................................................................................................. 2

1.4.2 AERMOD .................................................................................................. 3

1.4.3 CALPUFF.................................................................................................. 3

1.4.4 Scheffe Tables............................................................................................ 3

1.5 Modeling Protocol..................................................................................... 3

2. MODELING ANALYSIS............................................................................... 4

2.1 Source Type ............................................................................................... 4

2.1.1 Point Source............................................................................................... 4

2.1.2 Area Source ............................................................................................... 4

2.1.3 Fugitive Source.......................................................................................... 4

2.1.4 Volume Source .......................................................................................... 4

2.1.5 Road Emissions ......................................................................................... 5

2.1.5.1 Guidance ................................................................................ 5 

2.1.6 Open Pits.................................................................................................... 6

2.1.7 Pseudo-Point Sources................................................................................ 7

2.1.8 Flares ........................................................................................................ 7

2.1.9 Building Vents and Open Doors .............................................................. 8
2.2 Screening Procedures ............................................................................... 8

2.2.1 Emission Rate............................................................................................ 8

2.2.2 Terrain ....................................................................................................... 8

2.2.3 GEP Stack Height ..................................................................................... 8

2.2.4 Building Downwash .................................................................................. 9

2.2.5 Rural/Urban Classification ...................................................................... 9

2.2.5.1 Land Use ................................................................................ 9 

2.2.5.2 Population Density............................................................... 10 

2.3 Refined Analysis...................................................................................... 10

2.3.1 Emission Rate.......................................................................................... 10

2.3.2 Terrain ..................................................................................................... 10

2.3.3 Met Data .................................................................................................. 11 

2.3.3.1 Selection of Surface Characteristics for Met Data Proc 11 

2.3.4 Nearby Sources........................................................................................ 14

2.3.5 Background Monitoring......................................................................... 15

2.3.6 GEP Stack Height ................................................................................... 15

2.3.7 Receptor Grids ........................................................................................ 15

2.3.8 NO2 Modeling.......................................................................................... 16

2.3.9 PM10 Modeling Guidance....................................................................... 16

2.3.10 Ozone Modeling Guidance-Sheffe Tables............................................. 17

2.3.11 Deposition ................................................................................................ 17

3. STATE REQUIRED MODELING ............................................................... 17

3.1 TAC Modeling......................................................................................... 17

3.2 SO2 Modeling........................................................................................... 18

3.3 TV (Major Source/Modification) Modeling ......................................... 18

4. PSD MODELING ....................................................................................... 19
4.1 Significant Impact Analysis ................................................................... 19

4.2 Increment Analysis ................................................................................. 19

4.3 NAAQS Analysis ..................................................................................... 21

4.4 Visibility Analysis.................................................................................... 21 

4.4.1 Class II Area Impact Analysis ............................................................... 21 

4.4.2 Class I Areas Impact Visibility Analysis............................................... 21 

APPENDIX A POINT SOURCE MODEL INPUT DATA (EMISSIONS) ............A-1

APPENDIX B FLARE CALCULATION DERIVATION......................................B-1

APPENDIX C MODELING PROTOCOL SUBMISSION OUTLINE...................C-1

APPENDIX D FINAL SUBMISSION OUTLINE ................................................D-1
Oklahoma Modeling Guidance Document Page 1 

1. Introduction 

This is a guidance document on air dispersion modeling developed by the Air Quality Division 

(AQD) of the Oklahoma Department of Environmental Quality. The guidance provides 

assistance to applicants in demonstrating compliance with modeling requirements. These 

requirements protect the public’s health, general welfare, physical property, and the natural 

environment. 

Air dispersion modeling analyses may be required with an Air Quality permit application under 

Oklahoma Administrative Code (OAC) 252, Chapter 100, Subchapters 8, 31, and 42. This 

guidance clarifies existing practices, aids the modeler in developing an acceptable analysis, and 

assists AQD personnel in expediting the review process. 

This document relies on modeling guidance contained in the Guideline On Air Quality Models as 

codified in 40 CFR Part 51, Appendix W, as well as guidance issued by the EPA Office of Air 

Quality Planning and Standards (OAQPS) and EPA Region VI. 

The remainder of Sections 1 and 2 address general modeling concepts. Sections 3 and 4 address 

specific issues in modeling toxic air contaminates (TAC), per OAC 252:100-42, and modeling 

compliance with the National Ambient Air Quality Standards (NAAQS) and Increment 

consumption for Title V/Part 70, New Source Review (NSR), and Prevention of Significant 

Deterioration (PSD) permit applications. Appendix A contains a table of point source model 

input data (emissions) requirements for PSD and NSR compliance demonstrations. Appendix B 

provides a derivation for flare modeling guidance. Appendix C contains a checklist for modeling 

protocol submission. Appendix D contains a checklist for final modeling data submittal. 

1.1 What is Air Dispersion Modeling 

Air dispersion modeling is a method of predicting the ambient impact of one or more stationary 

sources of air pollutants. The algorithms used in the models are based both on the known 

physics of atmospheric processes and on empirical data. The results of an analysis are used by 

AQD staff to determine if a new or existing source of air pollutants can comply with state and 

federal maximum ambient concentration limits. The models are used to predict the highest 

concentrations expected from a source. For that reason, the models are designed to be 

conservative, i.e., over-predict ambient impacts. Because the models may over-predict the 

impact in an analysis, a modeled prediction alone does not mean that there will be a condition of 

air pollution. This prediction is a flag indicating potential air quality violations. AQD staff may 

require that the source perform more complex modeling or change physical or operational 

parameters of the source to reduce ambient impacts. If modeling continues to predict a violation, 

the AQD may require the source to conduct monitoring. 

1.2 State and Federal Regulations Requiring Modeling 

Various state and federal regulations require modeling. The Oklahoma Administrative Code, 

Title 252, Chapter 100 (OAC 252:100) codifies air regulations for the AQD. OAC 252:100-8 

regulates major sources. Both the federal PSD and NSR construction permit programs and the 

federal Title V/Part 70 permit program are incorporated in Subchapter 8. These programs require 

modeling to demonstrate compliance with and to protect the NAAQS and Increment. 
Oklahoma Modeling Guidance Document Page 2 

OAC 252:100-31 regulates emissions of sulfur (S) compounds from stationary sources in 

Oklahoma. This subchapter also limits the ambient concentrations of hydrogen sulfide (H2S) 

from new and exiting sources and sulfur dioxide (SO2) from existing sources and new petroleum 

and natural gas process facility with equipment subject OAC 252:100-31-26(a)(1). 

OAC 252:100-42 regulates emissions and impacts of TAC and Areas of Concern (AOC). This 

subchapter provides the methodology for developing and promulgating Maximum Acceptable 

Ambient Concentrations (MAAC) for individual TAC. TAC and associated MAAC are listed in 

Appendix O of OAC 252:100. After an AOC has been designated modeling may be required as 

part of the compliance strategy for the AOC. 

1.3 Levels of Modeling 

1.3.1 Screen Modeling 

Screening modeling analyses provide conservative estimates of source impacts with a minimum 

of input. For the EPA model, SCREEN3, worst-case meteorological conditions with respect to 

Pasquill-Gifford stability classes are used to evaluate maximum ground level concentrations. 

Screening programs are generally limited in their ability to evaluate terrain impacts and 

downwash effects from multiple buildings. However, for relatively simple sources, such as a 

single source with little to no elevated terrain and few downwash structures, these models will 

provide conservative estimates of downwind concentrations. 

1.3.2 Refined Modeling 

Refined modeling requires more detailed and precise input data and utilizes more complex 

models in order to provide more accurate estimates of ground level concentrations. Refined 

modeling may be required if the screening analysis results indicate that predicted concentrations 

from the evaluated sources could exceed a standard or a guideline. Refined modeling may also 

be requested if it is determined that a screening analysis will not adequately address the 

modeling scenario. It is usually the applicant’s responsibility to perform refined modeling. 

1.4 Acceptable Models 

In general, AQD defers to the Guideline on Air Quality Models, 40 CFR Part 51, Appendix W on 

the issue of acceptable models. This document provides guidance on appropriate model 

applications. The document is updated as EPA approves new models. However, AQD reserves 

the option to evaluate the use of unapproved models on a case-by-case basis. Depending on 

circumstance, this evaluation may require concurrence by EPA Region VI and/or public review. 

The following models may be used as is appropriate. 

1.4.1 SCREEN3 

SCREEN3 is the primary single-source screening model available from EPA. The model may be 

used for point, area, volume, and flare sources. EPA is currently working on a beta version of 

the code for AERSCREEN which will be released as soon as possible. AERSCREEN is the 

screening model for AERMOD and will replace use of SCREEN3. The model will produce 

estimates of regulatory design concentrations without the need for meteorological data and is 

designed to produce concentrations that are equal to or greater than the estimates produced by 

AERMOD with a fully developed set of meteorological and terrain data. 
Oklahoma Modeling Guidance Document Page 3 

1.4.2 AERMOD 

As of December 9, 2006, the AERMOD modeling system, a steady-state plume dispersion model 

for assessment of pollutant concentrations from a variety of sources, has become the primary 

model used for refined modeling. AERMOD incorporates air dispersion based on planetary 

boundary layer turbulence structure and scaling concepts, including treatment of both surface 

and elevated sources, and both simple and complex terrain. There are two input data processors 

of the regulatory AERMOD modeling system: AERMET, a meteorological data preprocessor 

that incorporates planetary boundary layer turbulence structure and scaling concepts, and 

AERMAP, a terrain data preprocessor that incorporates complex terrain using USGS Digital 

Elevation Data. The model code and supporting documents are not static but evolve to 

accommodate the best available science. Be sure to check the EPA SCRAM website often for 

updates. 

1.4.3 CALPUFF 

CALPUFF is a multi-layer, multi-species non-steady-state puff dispersion model. The 

CALPUFF model should be used for long-range impacts (greater than 50 km), visibility (light 

extinction), and acid deposition in Class I areas. CALPUFF modeling is generally required for 

PSD source impacts on Class I areas. 

1.4.4 Scheffe Tables 

The Scheffe Tables are a screening method for predicting 1-hour ozone impacts from VOC 

dominated sources. Richard Scheffe developed the Scheffe Tables through use of the Reactive 

Plume Model (RPM). Since promulgation of the 8-hour standard, use of the Scheffe Tables has 

become questionable. Until EPA publishes guidelines for compliance for individual sources, 

large sources will be included in available photochemical modeling datasets and will be modeled 

with the Comprehensive Air Quality Model with extensions (CAMx) to assess impacts and 

demonstrate compliance with the standard. 

1.5 Modeling Protocol 

A modeling protocol is required prior to performing any refined modeling analysis for PSD and 

NSR applications. For PSD/NSR applications, the AQD requests that the protocol be available 

for review prior to pre-application meetings. The applicant should allow one to two weeks for 

review. If the applicant proposes to use an unapproved model, four to six weeks should be 

allowed for examination. Upon review, the applicant will receive written notification of 

acceptance of the modeling approach as well as guidance on any outstanding issues. However, 

the applicant should be aware that an approved modeling protocol does not necessarily limit the 

extent of the modeling that will be required to demonstrate compliance with the applicable 

standards. A general outline for a complete modeling protocol is available in Appendix C. The 

outline identifies the expected format and content of the submission. 
Oklahoma Modeling Guidance Document Page 4 

2. Modeling Analysis 

2.1 Source Type 

2.1.1 Point Source 

This is the most common type of source to be modeled. Emissions from point sources are 

released to the atmosphere through well-defined stacks, chimneys, or vents. Point sources are 

usually buoyant and have an upward velocity. The following stack parameters are needed to 

model point sources: emissions, inside diameter, height above ground level, velocity or flow rate, 

and temperature. Other parameters relating to neighboring structures (height, width, length, and 

location with respect to the stack) may also be needed to include effects from building 

downwash. 

2.1.2 Area Source 

The area source algorithms are used to model low level or ground level releases with no plume 

rise (e.g., storage piles, slag dumps, and lagoons). The area source may be used to specify a 

rectangular-shaped area source with arbitrary orientation, an irregularly-shaped polygon of up to 

20 sides, a circular-shaped area source (modeled as an equal-area polygon of up to 20 sides). 

Area sources use an emission rate per unit area instead of total emissions. Emissions for area 

sources should be the annual average emissions. The total emissions are divided by the total area 

in square meters. Detailed guidance for area sources is contained in the User's Guide for the 

AMS/EPA Regulatory Model - AERMOD (EPA-454/B-03-001, 9/2004).

Caution: A 10:1 aspect ratio of length to width must be maintained when developing rectangular 

areas sources. If this ratio is to be exceeded, the area should be subdivided accordingly to 

achieve the target aspect ratio. 

Note: AERMOD has not implemented plume meander for area sources. Please refer to the 

AERMOD Implementation Guide (October 19, 2007) for guidance concerning this issue. 

2.1.3 Fugitive Sources 

Fugitive dust usually refers to dust put into the air by the wind blowing over roads, fields, or 

piles. Reentrained dust is put into the air by vehicles traveling over dirt roads or dusty areas. 

Fugitive emissions include emissions that are not captured and vented through a stack but that 

are vented to the atmosphere through general building vents. These types of fugitive sources can 

be modeled as line, area, or volume sources. Fugitive sources modeled as “area” sources must 

have a significant degree of mechanically generated turbulence (e.g., sand and gravel operations, 

haul roads). 

2.1.4 Volume Source 

The volume source algorithms are used to model releases from a variety of industrial sources, 

such as building roof monitors, multiple vents, and conveyor belts. The following parameters 

are needed to characterize volume sources: emission rate, release height (he), and initial 

horizontal (σYo) and vertical dimensions (σZo). 
Oklahoma Modeling Guidance Document Page 5 

The release height is the center of the volume above ground. Determination of the initial 

horizontal and vertical dimensions (initial sigmas) are based on the geometry and location of the 

source. The actual height, width, and depth of the release are used to calculate the initial 

horizontal and vertical dispersion parameters. Guidance for developing the initial sigmas is 

contained in Table 3-1 of the User's Guide for the AMS/EPA Regulatory Model - AERMOD

(EPA-454/B-03-001, 9/2004) and is reproduced below. 

The base of the volume source must be square. If the source is not square, model the source as a 

series of adjacent volume sources. For relatively uniform sources, determine the “Equivalent 

Square” by taking the square root of the area of the length and width of the volume base. 

Table 3-1. Summary of Suggested Procedures for Estimating Initial Lateral 

Dimensions and Initial Vertical Dimensions for Volume and Line Sources 

Type of Source Procedure for Obtaining Initial Dimension 

Initial Lateral Dimension (σYo) 

Single Volume Source σYo = length of side divided by 4.3 

Line Source Represented by 

Adjacent Volume Sources 

σYo = length of side divided by 2.15 

Line Source Represented by 

Separated Volume Sources 

σYo = center to center distance divided by 2.15 

Initial Vertical Dimension (σZo) 

Surface-based Source (he~0) σZo = vertical dimension of source divided by 2.15 

Elevated Source (he>0) on or 

adjacent to a Building 

σZo = building height divided by 2.15 

Elevated Source (he>0) not on or 

adjacent to a building 

σZo = vertical dimension of source divided by 4.3 

2.1.5 Road Emissions 

The AQD may require fugitive dust from road emissions to be modeled. If modeling is required, 

the emissions should be modeled as a volume source. 

2.1.5.1 Guidance 

The following is some guidance concerning modeling of road emissions. 

• Do not include road emissions in permit modeling analyses for short-term averaging 

periods - periods less than annual. 

• Do not include road emissions in permit modeling analyses for an annual averaging period 

if they will not be generated in association with the transport, storage, or transfer of 

materials (raw, intermediate, and waste), including sand, gravel, caliche, or other road-base 

aggregates at the facility. 
Oklahoma Modeling Guidance Document Page 6 

Volume Source Characterization: Follow the eight steps described in the following paragraphs: 

Step 1: Determine the adjusted width of the road. The adjusted width is the actual width of 

the road plus 6 meters. The additional width represents turbulence caused by the 

vehicle as it moves along the road. This width will represent a side of the base of the 

volume. 

Step 2: Determine the number of volume sources, N. Divide the length of the road by the 

adjusted width. The result is the maximum number of volume sources that could be 

used to represent the road. 

Step 3: Determine the height of the volume. The height will be equal to twice the height of 

the vehicle generating the emissions; rounded to the nearest meter. 

Step 4: Determine the initial horizontal sigma for each volume. 

• If the road is represented by a single volume, divide the adjusted width by 4.3. 

• If the road is represented by adjacent volumes, divide the adjusted width by 

2.15. 

• If the road is represented by alternating volumes, divide twice the adjusted 

width, measured from the center point of the first volume to the center point of 

the next represented volume, by 2.15. Start with the volume nearest to the 

property line. This representation is often used for long roads. 

Step 5: Determine the initial vertical sigma. Divide the height of the volume determined in 

Step 3 by 2.15. 

Step 6: Determine the release point. Divide the height of the volume by two. This point is in 

the center of the volume. 

Step 7: Determine the emission rate for each volume used to calculate the initial horizontal 

sigma in Step 4. Divide the total emission rate equally among the individual volumes 

used to represent the road, unless there is a known spatial variation in emissions. 

Step 8: Determine the UTM coordinate for the release points. The release point location is in 

the center of each of the base of the volume. This location must be at least one meter 

from the nearest receptor. (TNRCC 1999) 

2.1.6 Open Pits 

The open pit source option is used to model particulate emissions from open pits, such as surface 

coal mines and rock quarries. The open pit source option uses an effective area for modeling pit 

emissions, based on meteorological conditions, and then utilizes the numerical integration area 

source algorithm to model the impact of emissions from the effective area sources. The 

AERMOD model accepts rectangular pits with an optional rotation angle specified relative to a 

north-south orientation. The rotation angle is specified relative to the vertex used to define the 

source location (e.g., the southwest corner). Open pit sources have no plume rise. The 

parameters needed are the open pit emission rate, the average release height, the lengths of the 

sides of the open pit, the volume of the open pit, and the orientation angle in degrees from the 

north. Please note the following: 

• As with the area source, an emission rate per unit area is used. 

• The release height parameter cannot exceed the effective depth of the pit, which is 

calculated by the model based on the length, width and volume of the pit. 

• A release height of 0.0 indicates emissions that are released from the base of the pit. 
Oklahoma Modeling Guidance Document Page 7 

• The length-to-width aspect ratio for open pit should be less than 10 to 1. 

• Unlike the area source, the open pit cannot be subdivided. Characterize irregularly shaped 

pit areas by a rectangular shape of equal area. 

2.1.7 Pseudo-Point Sources 

Fugitive sources and non-standard stacks (stacks or vents with rain caps, and stacks or vents that 

release emissions horizontally) may be modeled as pseudo-point sources. Nonstandard point 

sources may have buoyancy or momentum and the modeling parameters used should provide 

representative impacts. Please refer to the AERMOD Implementation Guide (October 19, 2007) 

for guidance concerning this issue. Tilted stacks can take into account the vertical velocity of the 

plume using trigonometric factors where appropriate. 

2.1.8 Flares 

Flares are handled similarly to point sources; however, the heat release is used to calculate plume 

rise and effective stack diameter. For screening purposes, the flare option in SCREEN3 is 

acceptable. A flare option is not available in AERMOD. Therefore, in refined modeling, it is 

necessary to compute equivalent emission parameters to account for the buoyancy of the plume. 

There are several assumptions made in the SCREEN3 flare option, which form the basis of the 

equivalent parameter approach. The following parameters are assumed in SCREEN3: 

An ambient temperature of 293 K, 

55% of the heat lost due to radiation, 

a plume rise calculated from the top of the flame, assuming that the flame is bent 45 degrees 

from the vertical, 

an effective stack exit velocity of 20 meters per second, and 

an effective stack exit temperature of 1,273 K. 

The stack height and inside diameter are adjusted to account for the flame height and the 

buoyancy of the plume by the following equations: 

0.478 0.00128 Hequiv = Hactual + Qc (Eq. 1) 

equiv Qc D x

4 1.758 10− = (Eq. 2) 

Where: 

 Hequiv = equivalent height of the flare, m 

 Hactual = actual height of the stack from the ground, m 

 Qc = flared gas heat release, Btu/hr 

 Dequiv = equivalent diameter of the flare, m 

The derivation for the equations is available in Appendix B. The selection of effective stack 

parameters could influence the building downwash estimates. Therefore, if building downwash 

is of a concern then more realistic stack parameters should be evaluated. For this circumstance, 

please seek individual guidance from AQD. 
Oklahoma Modeling Guidance Document Page 8 

2.1.9 Building Vents and Open Doors 

Vents with a vertical discharge and no impediment to flow may be modeled as point sources. 

Horizontal vents or stacks with rain caps should be modeled as pseudo-point sources. Open 

doors may be modeled as pseudo-point sources with a stack height of two thirds (2⁄3) the total 

height of the opening. The stack height may be adjusted based on the release height within the 

building. Please seek specific guidance from the AQD. 

2.2 Screening Procedures 

2.2.1 Emission Rate 

The maximum short-term emission rate should be used to demonstrate compliance with all short 

term averaging rates. Model emission input data for point sources has been defined by EPA in 

40 CFR Part 51, Appendix W, Tables 8-1 and 8-2 and is reproduced in Appendix A. 

Note: For equipment that may run under a variety of conditions that affect emission rates and 

dispersion modeling estimates, a series of screening analyses should be run to determine the 

worst-case impact. For example, turbines should be evaluated at varying loads and temperatures 

to determine the worst-case scenarios. 

2.2.2 Terrain 

If the terrain within five kilometers of the stack rises to more than 20% of the shortest, nonfugitive, on-site stack being modeled, then the terrain feature elevations should be included for 

the receptor grid. Terrain should be included in all refined modeling. 

2.2.3 Met Data 

When conducting screening using AERMOD, use the most recent (at least 2001-2005) Integrated 

Hourly Surface (ISH) data from the National Climatic Data Center (NCDC) and Upper Air (UA) 

data from the Forecast System Laboratories (FSL) without incorporating data from the 

Oklahoma Mesonet. However, incorporation of Oklahoma Mesonet data will be required for 

refined modeling. 

2.2.4 GEP Stack Height 

Good Engineering Practice (GEP) stack height is the minimum stack height needed to prevent 

the stack exhaust plume from being entrained in the wake of nearby obstructions. If a proposed 

stack is below the GEP height, then the plume entrainment must be taken into account by 

modifying certain dispersion parameters used in air dispersion models. However, if the stack 

height equals or exceeds the calculated GEP stack height, then the stack height is considered the 

GEP stack height. Plume entrainment within the wake of nearby obstructions is unlikely and 

need not be considered when modeling stacks at the GEP stack height. The GEP stack height 

limitation set forth in OAC 252:100-8-1.5 applies in all cases. 
Oklahoma Modeling Guidance Document Page 9 

2.2.5 Building Downwash 

When one or more structures interrupt the wind flow, an area of turbulence called building 

downwash is created. Pollutants emitted from a fairly low level (e.g., a roof, vent or short stack) 

can be caught in this turbulence, affecting their dispersion. Modeling that includes calculations 

for building downwash gives a more accurate representation of pollutant impact than does 

modeling that omits consideration of downwash affects. 

A building is any physical obstruction to airflow at the modeled facility. A structure is a 

building or group of buildings determined to be important in downwash considerations. The 

dominant downwash structure is the structure that renders the highest GEP recommended stack 

height. If a stack is at GEP or higher, then downwash is not a factor. GEP stack height is 

calculated according to the following equation. 

H = h +1.5L

where: H = Recommended stack height. 

 h = The distance from the highest point on a tier or building to ground level. 

 L = The lesser of the height or projected width for a particular tier or structure. 

SCREEN3 calculates the maximum projected width as the greatest crosswind distance between 

two points in a building or structure. There are methods of determining the downwash structures 

and in fact the dominant downwash structure; however, if multiple downwash structures exist, 

the BPIP-Prime program should be used in conjunction with AERMOD. 

2.2.6 Rural/Urban Classification 

Dispersing plumes encounter more turbulence in urban areas than in rural areas, due to building 

wakes as well as the somewhat warmer temperatures in urban areas. For any given set of 

meteorological conditions, the urban plume dispersion coefficients should be larger than the rural 

plume dispersion coefficients. The higher coefficients cause an urban plume to spread more 

rapidly than a rural plume, and hence the maximum ground-level concentration of an urban 

plume occurs closer to the emission source than it does for a rural plume. (Beychok 1994) 

All models allow for the selection of urban or rural dispersion coefficients. Determination of the 

applicability of urban or rural dispersion is based on land use or population density. The land 

use method is preferred. 

2.2.6.1 Land Use 

Circumscribe a 3 km radius circle about the source. If Auer land use types I1, I2, C1, R2, and 

R3 account for 50 percent or more of the area, select the urban option. Otherwise, use the rural 

option. 
Oklahoma Modeling Guidance Document Page 10 

Auer Land Use Categories I1, I2, C1, & R2 (Auer 1978) 

Type Use and Structure Vegetation 

I1 Heavy Industrial 

 Major chemical, steel and fabrication industries; generally 

3-5 story buildings, flat roofs 

Grass and tree growth 

extremely rare; <5% 

vegetation 

I2 Light-moderate industrial 

 Rail yards, truck depots, warehouses, industrial parks, minor 

fabrications; generally 1-3 story buildings, flat roofs 

Very limited grass, trees 

almost totally absent; <5% 

vegetation 

C1 Commercial 

 Office and apartment buildings, hotels;>10 story heights, 

flat roofs 

Limited grass and trees; 

<15% vegetation 

R2 Compact Residential 

 Single, some multiple, family dwelling with close spacing; 

generally <2 story, pitched roof structures; garages (via 

alley), no driveways 

Limited lawn sizes and 

shade trees; <30% 

vegetation 

2.2.6.2 Population Density 

Compute the average population density per square kilometer within the area as defined above. If 

the density is greater than 750 people/km use the urban option. Otherwise, use the rural option. 

2.3 Refined Analysis 

2.3.1 Emission Rate 

The maximum short-term emission rate should be used to demonstrate compliance with all short 

term averaging rates. Model emission input data for point sources has been defined by EPA in 

40 CFR Part 51, Appendix W, Tables 8-1 and 8-2 and is reproduced in Appendix A. 

Note: For equipment that may run under a variety of conditions that may affect emission rates 

and dispersion modeling estimates, a series of screening analyses should be run to determine the 

worst-case impact. For example, turbines should be evaluated at varying loads and temperatures 

to determine the worst-case impact scenario. 

2.3.2 Terrain 

Terrain data should be included in all refined modeling analyses. Terrain data is available from 

United States Geological Survey (USGS) as Digital Elevation Modeling (DEM) data. These data 

are generally available in two resolutions: 1-degree DEM maps and 7.5-minute maps (referred to 

as quadrangles). The 7.5-minute quadrangles are freely available in the new Spatial Data 

Transfer Standard (SDTS) format and will need to be converted to the DEM format. The 7.5-

minute DEM data are the preferred source for elevation data. AQD can provide DEM data via email for small modeling domains. AQD will only accept 1 degree DEM data for use with coarse 

grids with receptor spacing of 1 km and greater, without a specific demonstration or 

determination that another resolution is more appropriate. 
Oklahoma Modeling Guidance Document Page 11 

The 7.5-minute DEM are based on Universal Transverse Mercator (UTM) coordinates and use a 

30 meter spacing. Interpolation of receptor and source heights from the DEM data should be 

based on the current guidance contained in Section 4.4 of the User’s Guide for the AERMOD 

Terrain Preprocessor (AERMAP) (EPA-454/B-03-0003, 10/2004). AERMAP uses a distance 

weighted bilinear interpolation method. 

Oklahoma has three UTM zones (zones 13, 14, and 15). If the modeling domain crosses a UTM 

zone, source and receptor coordinates will need to be translated to a common zone. The UTM 

coordinates on the DEM data may not be consistent with those on paper maps. Though most 

maps and DEM data in Oklahoma are based on the 1927 North American Datum (NAD27), the 

applicant must check for consistency. Therefore, the datum on which source coordinates and 

elevation data are based on must be reported in the application. In some areas multiple DEM 

data may be available for download from USGS, only level 2 DEM files may be used. 

The Army Corps of Engineers has developed a conversion program, which will translate data to 

a common zone and will also convert from one datum to another. The program is called 

Corpscon and may be obtained from the AQD. 

Note: Digital elevation data obtained originally in the SDTS format may be used if obtained 

from the USGS after June 1, 2001. All earlier data in the SDTS format contains a positional 

error that may impact modeling. 

2.3.3 Met Data 

AQD is now requiring use of 2001-2005 Oklahoma Mesonet data, as on-site data, with NCDC 

ISH data, and FSL UA data, with all refined air dispersion modeling. AQD is incorporating use 

of the Oklahoma Mesonet data to help prevent adverse environmental impacts and to promote 

the use of good science by use of more recent, more accurate, and more representative data. 

Oklahoma Mesonet data was provided to the AQD courtesy of the Oklahoma Mesonet, a 

cooperative venture between Oklahoma State University (OSU) and the University of Oklahoma 

(OU) and supported by the taxpayers of Oklahoma. The Oklahoma Mesonet is a world-class 

network of meteorological monitoring stations. The Mesonet is unique in its capability to 

measure a large variety of meteorological conditions at so many sites across an area as large as 

Oklahoma. Standard Mesonet data includes: air temperature and relative humidity at one and a 

half meters, wind speed, wind direction, and the standard deviation of wind speed and wind 

direction at ten meters, the wind speed at two meters, the air temperature at nine meters, rainfall, 

barometric pressure, solar radiation, soil temperatures, and calibrated soil moisture and 

temperatures. At each site, these variables are continuously measured and packaged into 5-

minute observations. The observations were then converted into hourly averages. These hourly 

averages were processed by the AQD into a format that was able to be processed by AERMET. 

Soil measurements were not included in the final data sets developed for use by AERMET. Some 

of the variables are not used by AERMET at this time but were incorporated into the data sets in 

hopes that they could be used in the future. 
Oklahoma Modeling Guidance Document Page 12 

The National Weather Service operates 14 automated weather stations in Oklahoma. These 

stations usually take atmospheric measurements once every hour. The Oklahoma Mesonet 

consists of at least one station in each of Oklahoma’s 77 counties and measures the variables 

once every five minutes providing more frequent and more localized information. Data from the 

Oklahoma Mesonet will help make more accurate forecasts of ambient impacts from stationary 

sources located in Oklahoma. A table of the current Oklahoma Mesonet sites is shown in 

Appendix E. 

The data obtained from the Oklahoma Mesonet came in hourly data files that contained all of the 

standard data from all of the sites for that hour. The first part of formatting the data was to create 

a single file for each of the Mesonet sites that contained all of the data from that site. This was 

done using a Pearl script. Next, the data from each site was imported into Microsoft Excel and 

formatted. Formatting the data in Excel was primarily done using Visual Basic. The individual 

tasks performed on the Mesonet data are listed below: 

1. Import Mesonet data set into Excel (Data not imported: WMAX, TS10, TB10, TS05, 

TB05, TS30, & WVEC). 

2. Change all missing value codes to -999 (Missing Values: -995,-996,-997,-998,-999). 

3. Change the format of the year from YYYY to YY. 

4. Calculate the precipitation for each hour. Mesonet precipitation data is the hourly sum of 

precipitation during the day. To determine the hourly precipitation, the difference between 

that hour and the previous hour was determined unless that hour was the first hour of the 

day. 

5. Convert time from minutes to hours by dividing the minutes by 60. 

6. Change pressure from hPa (mb) to dPa (mb x 10). 

7. Resize all columns to a fixed width of 8. 

8. Format the variables to the correct number of significant digits as floating point numbers. 

TAIR, WSPD, WSSD, WDSD, TA9M, & WS2M each were established with one 

significant digit. PRES, RELH & WDIR each established with zero significant digits. 

PRCP was established with 2 significant digits. 

9. Arrange all the columns in the correct order (single and multi-level variables). 

10. Sort the columns by year, month, day and then hour. 

11. Replace all solar radiation values of -1 with zero. 

After the data was formatted, the data was evaluated for missing data. The hour(s) for which the 

data was/were missing was determined and then replacement values were calculated and 

inserted, if applicable. All missing data was documented so that if there were some issues for a 

particular hour it could be determined if it was due to data substitution. The files documenting 

missing data in the Mesonet data sets are available for review upon request. When a single hour 

of Mesonet observations was missing, the value(s) for that hour was/were interpolated by taking 

the average of the previous hour and the following hour. If more than one hour of Mesonet 

observations were missing, those hours were not changed. AERMET should be set to run so that 

NWS data is used when on-site data is missing so that the most complete data set can be used 

when conducting the modeling. 
Oklahoma Modeling Guidance Document Page 13 

Processed Oklahoma Mesonet data should be combined with NCDC ISH data and FSL UA 

rawinsonde observation (RAOB) data using AERMET to produce the surface and profile files 

used by AERMOD. NCDC ISH data sites and UA rawinsode data sites were assigned to each 

Mesonet site. Generally the closest ISH or UA site was chosen. However, when there were two 

or more sites that were about the same distance from a Mesonet site, climate regions, 

topography, meteorology, and other factors were taken into account when designating the 

applicable ISH or UA data site for the corresponding Mesonet data site. The ISH data sites were 

reviewed for completeness and if there was a significant amount of missing data then those sites 

were not considered when assigning them to Mesonet data sites. All UA data was reviewed for 

missing data, if there was missing data it was replaced using data from a site with similar 

thermodynamic profiles. Each UA site was assigned a primary and a secondary UA site. When 

there was a sounding missing from the data it was replaced with a sounding from the primary 

UA data site. If a sounding was not available from the primary UA data site, then a sounding 

from the secondary UA site was used. 

2.3.4 Selection of Surface Characteristics for Met Data Processing 

When using AERMET to prepare the meteorological data for AERMOD, you must input three 

surface characteristics: Albedo, Bowen Ratio, and Surface Roughness Length. These values 

should be determined using the AERSURFACE tool version 08009. The guidelines in the 

AERSURFACE User’s Guide (EPA-454/B-08-001, 1/2008) should be followed when using the 

AERSURFACE tool. For facilities wanting to use different surface characteristics and or met 

data, site-specific surface analysis, sensitivity analysis, and/or meteorological data may be 

required. The following are AQD’s guidance on specific prompts from the AERSURFACE tool: 

• “Enter the type of coordinate used to define the center of the study area. 

‘UTM’ for Universal Transverse Mercator coordinates; 

‘LATLON’ for Latitude and Longitude coordinates. 

(Note: User responses are not case-sensitive.)”

The user should enter “LATLON” for this question. The user will then be prompted to enter the 

Latitude (in decimal degrees) and then the Longitude (in decimal degrees), using a negative 

number for west longitude. The user must also specify the horizontal reference datum (NAD83 

or NAD27). The user should use the latitude and longitude of the applicable Mesonet data site as 

shown in Appendix E. The latitude and longitude for each site is based on the NAD83 horizontal 

reference datum. 

• “Enter the radius (in km) of the study area used for surface roughness (0.1 – 5.0 km). The 

recommended default value is 1 km.” 

The user should enter the default value. If a radius other than the recommended default value of 

1km is used, it should be documented and justified in a modeling protocol prior to conducting 

the modeling. 

• “Do you want to define the surface roughness length for multiple sectors?” 

The user should enter “N” for this question. When determining the surface characteristics for 

each Mesonet site the applicant should only define one sector. 
Oklahoma Modeling Guidance Document Page 14 

• “Define the temporal resolution of surface characteristic outputs (ANNUAL, SEASONAL 

or MONTHLY). ... Enter 'A' for ANNUAL, 'S' for SEASONAL, or 'M' for MONTHLY:” 

The user should enter “S” for this question. The temporal resolution of the surface 

characteristics for each Mesonet site should only be determined on a seasonal basis. 

• “Does the site experience continuous snow cover for most of the winter?” 

The user should enter “N” for this question due intermittent snowfall in Oklahoma. 

• “Is this site at an airport?” 

The user should enter “N” for this question. 

• “Is this site in an arid region?” 

The user should enter “N” for this question. 

• “Characterize the surface moisture condition at the site relative to climatological normals, 

to be applied for all periods. Enter ‘A’ for Average, ‘W’ for Wet, or ‘D’ for Dry.” 

The user should run the program three times one for each of the surface moisture conditions (A, 

W, & D). Then based on the information in Appendix F assign the correct Bowen Ratio based 

on season and condition to the correct temporal period. To determine the surface moisture 

conditions for each Oklahoma Mesonet site during each season, percent of normal precipitation 

graphs for each season were reviewed for the full five years of met data. Based on the 

precipitation data each site was marked as wet or dry, if applicable. If the data indicated average 

conditions the period for that site was left blank. Appendix F also contains the most recent land 

use determination and the call signs of the ISH data sites and the UA data sites to be used with 

each Mesonet data site. 

After the applicant determines the surface characteristics to use for the applicable Mesonet site, 

the applicant should submit all AERSURFACE (.dat) and (.log) files with either the modeling 

protocol or the modeling submittal. 

2.3.5 Nearby Sources 

Existing nearby sources are required to be included in PSD and NSR NAAQS and Increment 

analyses. The AQD allows the use of a modified “10-D Rule” to narrow the list of sources to 

only those that have the potential to significantly impact the modeling domain. The “10-D Rule” 

eliminates sources from the modeling review when the source’s emissions (TPY) are less than 10 

times the distance (in kilometers) from the modeled facility. These sources are designated as 

background sources and should not be modeled. Stated differently, any minor source (100 TPY 

or less), which is 10 km or more from the source in question, may be excluded. 
Oklahoma Modeling Guidance Document Page 15 

Upon request, the AQD will provide a list of sources within a defined radius from a facility that 

should be included in a modeling review. The list will include stack parameters as reported 

annually in emission inventories and potential emissions. If required, actual emissions for use in 

more refined increment consumption modeling will be provided at a later date. All sources and 

emissions provided to the applicant by AQD should be included in the modeling analysis. For 

large inventories, the AQD may request that the applicant provide some assistance in obtaining 

potential and actual emissions for some of the sources to be modeled. This may require the 

applicant to review permits and permit applications for the sources. Permits usually are available 

from the AQD in electronic format. The applicant should submit with the application a final list 

of sources included in the modeling analysis. 

2.3.5 Background Monitoring 

Background concentrations must be added to PSD and NSR NAAQS analyses. If the modeled 

impacts from the facility are less than the monitoring de minims levels, ambient monitoring data 

from the appropriate monitoring sites should be obtained and used by the applicant. Monitoring 

data should be obtained from the EPA air data web site: http://www.epa.gov/air/data/index.html. 

Concurrence of the AQD should be obtained on the appropriate monitor location and 

concentrations. If a monitoring de minimis level is exceeded, the applicant should provide 

justification for use of existing monitoring based on the guidance provided in the Ambient 

Monitoring Guidelines for Prevention of Significant Deterioration (PSD) (EPA-450/4-87-007, 

5/1987). If the facility is unable to meet the guidelines provided, pre-construction ambient 

monitoring to determine the background concentrations may be required depending on the size 

and location of the area where the de minimis level is exceeded. Post construction ambient 

monitoring may also be required or used to show compliance with the NAAQS. 

Background concentrations should be based on the monitoring data available for the most recent 

complete year of data. Background concentrations for short term standards should be based on 

the highest second highest (H2H) value, except for PM10 24-hour standard which should be 

based on the highest fourth highest (H4H) value from the most recent three years of data. 

Background concentrations for annual standards should be based on the annual mean value, 

except for PM10 which should be based on the average of the annual mean from the most recent 

three years of data. 

2.3.6 GEP Stack Height 

The Good Engineering Practice (GEP) stack height limitation of OAC 252:100-8-1.5 applies in 

all cases. The Building Parameter Input Program Plume Rise Model Enhancements (BPIPPRIME) should be used for AERMOD. 

2.3.7 Receptor Grids 

100 meter spacing is usually sufficient for most purposes except preliminary coarse-grid 

modeling. While Cartesian Grids are preferred, polar grids will be acceptable so long as the 

receptor distances do not exceed grid spacing requirements. Before a final receptor grid 

formation may be established, concentrations modeled on an initial coarse grid should be 

evaluated. Areas of maximum concentration should be established and a fine grid (100 meter 

spacing) should be used uniformly throughout those areas and extending to 1 kilometer beyond 
Oklahoma Modeling Guidance Document Page 16 

the areas of maximum concentration. It is the applicant’s responsibility to demonstrate that the 

grid is sufficiently compact to identify the maximum concentration for each averaging period. 

The receptor grid used should extend far enough to determine the maximum impact from all of 

the sources at the facility and all nearby facilities. The receptor grid for each modeling analysis 

is different due to the local meteorology, terrain, and source makeup. The draft New Source 

Review Workshop Manual Prevention of Significant Deterioration and Nonattainment Area 

Permitting (EPA, 10/1990).NSR workshop manual indicates that in general a grid extending out 

to 10 km will be “adequate to identify areas of maximum concentration. However, the total 

number of receptors will vary based on the specific air quality analysis performed.” Appendix 

W to 40 CFR Part 51 indicates that maximum impacts occur on calm days as the plumes 

encounter hills at or near the same height as the stacks. Terrain surrounding a facility should be 

evaluated to determine if there are hills in the area and should be extended to include them. For 

modeling in which a significant impact level (SIL) is exceeded and a radius of impact (ROI) is 

defined, a fine grid (100 meter spacing) should usually extend at least 1 kilometer beyond the 

ROI. The domain for the receptor grid should follow the guidance in Section 2.2.1 of User’s 

Guide for the AERMOD Terrain Preprocessor (AERMAP) (EPA-454/B-03-0003, 10/2004). 

Removal of receptors outside the radius of impact or at which a significant impact level occurs 

when modeling the NAAQS or increment for a project is not acceptable. Since the NAAQS and 

Increment analyses include sources which were not included in the significant impact level 

analyses, modeling using a receptor grid which only includes those receptors at which a 

significant impact occurs may not ensure that the maximum impact from the "facility" or from 

other surrounding sources is determined. If the NAAQS or increment is violated, then the 

facility can show that the modification does not have a significant impact at those receptors and a 

permit may be issued for that modification. If there is a “potential” exceedance of a standard in a 

particular area, whether it is due to the facility or not, AQD can use the modeling to determine 

the potential causes of the potential exceedance and can take measures to mitigate or alleviate 

those issues. 

2.3.8 NO2 Modeling 

Section 5.2.4 of Appendix W, 40 CFR Part 51, implements a tiered screening approach to obtain 

annual average estimates of NO2 from point sources for PSD and NSR analyses. Use of Tier I 

(conversion of all NOX to NO2) and Tier II (Use of the ambient ratio method (ARM)) of this 

multi-tiered approach are approved by AQD for all NO2 modeling. Use of a Tier III analysis by 

an applicant should be approved by AQD prior to modeling submittal and may require EPA 

approval. 

2.3.9 PM10 Modeling Guidance 

The determination of PM10 design values is briefly discussed Appendix W, 40 CFR Part 51 and 

is explained in the PM10 SIP Development Guideline (EPA-450/2-86-001, 1986). Until 

incorporation of the new PM10-2.5, and PM2.5 standards, the modeled design concentration for the 

PM10 24-hour NAAQS is the highest sixth high (H6H) concentration over a 5-year period at any 

receptor. The MULTYEAR keyword in the control (CO) pathway in the AERMOD model can 

be used to obtain the H6H concentration in 5 years. The modeled design concentration for the 

PM10 annual NAAQS is the 5-year average of the highest annual average concentrations. 
Oklahoma Modeling Guidance Document Page 17 

However, compliance with the PM10 24-hour Increment are based on the Highest Second Highest 

(H2H) value and compliance with the PM10 Annual Increment is based on the highest annual 

average. 

2.3.10 Ozone Modeling Guidance-Sheffe Tables 

Previously, under guidance from EPA, AQD has conservatively required the use of the Scheffe 

tables to evaluate ozone impacts from PSD sources with VOC emissions greater than 100 tons 

per year. The Scheffe tables are a tabular result of photochemical modeling conducted with the 

Reactive Plume Model, and VOC speciation assumptions for both rural and urban areas. The 

tables are used as a conservative screening analysis. 

Since promulgation of the 8-hour standard use of the Scheffe Tables has become questionable. 

Until EPA publishes guidelines for compliance for individual sources, large sources will be 

included in available photochemical modeling datasets and will be modeled with CAMx to 

assess impacts and demonstrate compliance with the standard. However, an applicant may be 

required to conduct more extensive modeling using models such as the CAMx, or the 

Community Multiscale Air Quality Modeling System (CMAQ) , which are acceptable for 

determining ozone impacts. 

2.3.11 Deposition 

The Addendum to the User's Guide For The AMS/EPA Regulatory Model – AERMOD (EPA454/B-03-001, 10/2004) explains the deposition algorithms and specifies the source parameters 

for use of deposition. All additional data used for an air dispersion analysis that incorporates 

deposition should be provided to and approved by AQD.

The wet deposition option should not be used for regulatory modeling analysis. Wet deposition 

is not a guideline feature of AERMOD. Per EPA guidance, dry gas deposition is not usually 

required for PM10 evaluations because of negligible settling velocities. However, AQD reserves 

the right to request a dry deposition evaluation for any PM emissions, but most specifically for 

TAC. 

3. State Required Modeling 

3.1 TAC Modeling 

The AQD as part of the compliance strategy for an AOC may require owners or operators of 

applicable stationary sources within an AOC to perform ambient air modeling for the TAC of 

concern to demonstrate compliance with the applicable MAAC established per OAC 252:100-42. 

All applications of air quality modeling shall be based on the applicable models, databases, and 

other requirements specified in Appendix W of 40 CFR Part 51. Modification or substitution of 

approved models will be considered on a case-by-case basis. Owners or operators of facilities 

located in an AOC shall not be required to demonstrate compliance with the TAC MAAC within 

the boundaries of their facilities. 
Oklahoma Modeling Guidance Document Page 18 

3.2 SO2 Modeling 

Subchapter 31 controls emissions of sulfur compounds from stationary sources. Per OAC 

252:100-31-7(a) emissions of SO2 from any existing facility or any new petroleum and natural 

gas process facility with equipment subject to OAC 252:100-31-26(a)(1) shall not impact 

existing ambient air concentrations of SO2 at any given point by more than: 

 Concentrations 

Averaging periods μg/m3 ppmv 

5-minute 1,300 0.50 

1-hour 1,200 0.46 

3-hour 650 0.25 

24-hour 130 0.05 

Annual 80 0.03 

Per OAC 252:100-31-7(b) emissions of hydrogen sulfide (H2S)from any new or existing source 

shall not result in a 24-hour average ambient air concentration H2S at any given point of 0.2 

ppmv or greater. 

Facilities with emissions of SO2 and/or H2S are required to show compliance with the ambient 

standards using EPA approved atmospheric dispersion models. Facilities must demonstrate 

compliance with the ambient air standards taking into account emissions from all the sources at 

the facility. Per OAC 252:100-31(c) the ambient standards do not apply to ambient air 

concentrations or impacts occurring on the property from which such emission occurs, providing 

such property, from the emission point to the point of any such concentration, is controlled by 

the person responsible for such emission. 

3.3 TV (Major Source/Modification) Modeling 

Criteria pollutant modeling to demonstrate NAAQS and Increment compliance may be required 

of any new major source or modification to an existing major source with a net increase of 100 

TPY of a single criteria pollutant. NAAQS modeling should be conducted by evaluating the 

total source impact with an appropriate monitored background concentration added. Concurrence 

from the AQD should be obtained on which monitor will provide adequate background 

concentrations. Increment modeling should be conducted by evaluating the total source impact 

of increment consuming sources. Temporary sources of emissions are not required to be 

included in the modeling analyses as long as they do not impact a Class I area or an area where 

an applicable increment is known to be violated. 

Note: If modeling demonstrates that the source will exceed PSD monitoring thresholds, postconstruction monitoring though not specifically required under the Title V/Part 70 regulations 

may be required under the general authorizations of the DEQ. This decision will be made on a 

case-by-case basis and will depend on the extent of the impact area as well as the extent to which 

the NAAQS or Increment are threatened by the source. 
Oklahoma Modeling Guidance Document Page 19 

4. PSD Modeling 

A checklist for PSD modeling submittals is available in Appendix D. 

4.1 Significant Impact Level (SIL) Analysis 

A significant impact analysis is the first level of modeling performed in a PSD evaluation. For 

each applicable pollutant, the analysis must include all stack emissions and quantifiable fugitive 

emissions resulting from the proposed source. For a proposed modification, the determination 

includes contemporaneous emissions increases and decreases, with emissions decreases input as 

negative emissions in the model. The EPA allows for the exclusion of temporary emissions such 

as those associated with construction. The applicant is required to compare results to the SIL as 

defined in 40 CFR Part 51.165(b)(2). If the highest modeled concentration over five years of 

meteorological data or the Highest First High (H1H) is less than or equal to the SIL, then the 

demonstration is complete. Per EPA guidance, the source is not considered to cause or 

contribute to an exceedance of the NAAQS or consume increment if the modeled impact is at or 

below the SIL. If the highest modeled concentration is greater than the SIL, the applicant is 

required to perform additional refined modeling or reduce the impact to below the SIL. If the 

modeled impacts remain above the SIL, a ROI is defined. The ROI extends from the center of 

the proposed facility to the farthest receptor that shows an impact at or above the significance 

levels. 

4.2 Increment Analysis 

For compliance with the Increment, the design concentration for the short term standards (3-hour 

and 24-hour) is based on the H2H and the highest annual average for the annual standards. The 

AQD maintains a record of county/area baseline dates; however, a database of increment 

consumers is not available. Upon request, the AQD will provide the applicant with a list of 

sources within the ROI plus fifty kilometers. The list will include stack parameters as reported 

annually in emission inventories and potential emissions. Increment consuming sources will be 

indicated in the list. When there are a large number of increment consuming sources, the AQD 

may request assistance from the applicant in determining actual emissions. The applicant should 

always submit a list of sources included in the modeling analysis with the application. 

A Tiered approach is taken towards modeling increment consuming sources. For Tier 1, the 

increment consuming sources should be modeled using their potential emissions. If the applicant 

is unable to show compliance with the increments using potential emissions, the next tier would 

be used. For Tier II, actual emissions may be used to show compliance with the Increment. The 

applicant should make a separate request for actual emissions from sources. Actual emissions 

are generally based on actual operating hours, production rates, and types of materials stored, 

processed, or combusted and will be determined based on a two year average. For short term 

increments, if no hourly data exists for a particular source then actual emissions should be based 

on potential emissions. EPA has recently proposed guidance on calculation of actual emissions 

which will be incorporated as soon as it becomes final. 
Oklahoma Modeling Guidance Document Page 20 

If the proposed site is within 50 kilometers of another state, the applicant must obtain a list of 

sources to be evaluated from that state. If the ROI extends into another state, the applicant must 

confirm whether a baseline has been set in that region or not. If a baseline date has been set, the 

applicant must follow the guidance provided by that state for the evaluation of increment 

consumption within that state. 

The following excerpt is taken directly from the draft New Source Review Workshop Manual 

Prevention of Significant Deterioration and Nonattainment Area Permitting (EPA, 10/1990). 

“For a PSD increment analysis, an estimate of the amount of increment consumed by 

existing point sources generally is based on increases in actual emissions occurring since 

the minor source baseline date. The exception, of course, is for major stationary sources 

whose actual emissions have increased (as a result of construction) before the minor source 

baseline date but on or after the major source baseline date. For any increment-consuming 

(or increment-expanding) emissions unit, the actual emissions limit, operating level, and 

operating factor may all be determined from source records and other information (e.g., 

state emission files), when available, reflecting actual source operation. For the annual 

averaging period, the change in the actual emissions rate should be calculated as the 

difference between: 

• the current average actual emissions rate, and 

• the average actual emissions rate as of the minor source baseline date (or major 

source baseline date for major stationary sources).

In each case, the average rate is calculated as the average over the previous 2-year period 

(unless the permitting agency determines that a different time period is more representative 

of normal source operation). For each short-term averaging period (24 hours and less), the 

change in the actual emissions rate for the particular averaging period is calculated as the 

difference between: 

• the current maximum actual emissions rate, and 

• the maximum actual emissions rate as of the minor source baseline date (or major 

source baseline date for applicable major stationary sources undergoing construction 

before the minor source baseline date). 

In each case, the maximum rate is the highest occurrence for that averaging period during 

the previous 2 years of operation.” 

If an exceedance of the increment is identified and the applicant has a significant impact on that 

receptor, the situation must be rectified. The AQD cannot issue a permit that violates the 

increment. 
Oklahoma Modeling Guidance Document Page 21 

4.3 NAAQS Analysis 

Upon request, the AQD will provide the applicant with a list of sources within the ROI plus fifty 

kilometers. The list will include stack parameters as reported annually in emission inventories 

and potential emissions. All sources and emissions provided to the applicant by AQD should be 

included in the modeling analysis. For large inventories, the AQD may request that the applicant 

provide some assistance in obtaining potential emissions for some of the sources to be modeled. 

This may require the applicant to review permits and permit applications for the sources. Permits 

may be available from the AQD electronically. The applicant should submit with the application 

a list of sources included in the modeling analysis. 

If the proposed site is within 50 kilometers of another state, the applicant must obtain a list of 

sources to be evaluated from that state. If the radius of impact extends into another state, the 

applicant must follow the guidance provided by that state for the evaluation of the NAAQS 

within that state. 

Compliance with short term NAAQS (3-hour, 8-hour, and 24-hour) is based on the H2H for all 

pollutants except for PM10. Compliance with the annual standard is based on the highest annual 

average concentration, except for PM10. For PM10, compliance with the NAAQS 24-hours 

average is based on the H6H over five years of data and compliance with the annual standard is 

based on the five year average of the annual average concentrations. 

4.4 Visibility Analyses 

Visibility impact analyses are required for the area around the affected source and may be 

required for any Class I areas near the affected source. The current EPA guidance document 

Workbook for Plume Visual Impact Screening and Analysis (Revised) (EPA 454/R-92-023, 

10/1992) describes how to evaluate plume visual impacts including use of the visual impact 

screening model (VISCREEN). VISCREEN can be applied in two successive screening modes 

without the need for extensive input. If screening calculations using VISCREEN demonstrate 

that during the worst case meteorological conditions a plume is imperceptible then it will not 

cause an adverse impact on visibility. To determine if a plume is perceptible, the impacts are 

compared to the screening criteria. If impacts exceed the screening criteria, further analysis may 

be required. The screening criteria are a change in relative sensitivity (∆E) value of 2.0 and a 

green absolute contrast value of 0.05. 

4.4.1 Class II Area Impact Analysis 

VISCREEN should be used to address the visibility impacts of a source or modification within a 

Class II area. There are three levels of visibility analyses the first level is using the emissions 

and the default parameters defined by the program. The second level is where the user selects 

certain variables to get a more realistic view of the predicted impacts. The third level is a 

comprehensive analysis using PLUVUE. 

Since VISCREEN was developed to over predict impacts and EPA’s guidance was developed 

mainly for Class I areas, AQD was concerned that the low screening levels would cause 

applicants to be required to perform Level 3 analyses for Class II areas. In an effort to prevent 

potentially time consuming efforts which would not lead to a real improvement in air quality, 
Oklahoma Modeling Guidance Document Page 22 

AQD has determined that the Class II levels should be approximately three times the Class I 

screening levels. Therefore, when comparing visibility impacts in a Class II area the following 

levels should be used: a ∆E value of 6.0 and a green absolute contrast value of 0.15. If a Level 1 

and Level 2 analysis exceeds these levels a comprehensive analysis should be performed. 

There are some sensitive areas located in Class II areas. If your facility is located within 40 km 

of one of these sensitive areas, the boundaries of the sensitive area should be used in the 

visibility analysis. The sensitive areas include but are not limited to the following areas: 

Sensitive Area Nearest Town 

Tall Grass Prairie Preserve Pearson, OK 

Great Salt Plains State Park Jet, OK 

Lake Optima Wildlife Refuge Hardesty, OK 

Rita Blanca National Grassland Felt, OK 

Black Kettle National Grassland Strong City, OK 

Arbuckle’s Lake Recreational Area Sulfur, OK 

Tishomingo Wildlife Refuge Tishomingo, OK 

Deep Fork Wildlife Refuge Okmulgee, OK 

Ouachita National Forest Big Cedar, OK 

McCurtain County Wildlife Refuge Hochatown, OK 

Little River Wildlife Refuge Idabel, OK 

Notes: When using VISCREEN and there are no sensitive receptors located within 40 km of the 

facility; The distance from the source to the observer and the distance from the source to the 

closest Class I area boundary should be set equal to each other and can arbitrarily be set to 1 km; 

and The distance from the source to farthest Class I area boundary may be arbitrarily established 

as 10 km. NO2 emissions can be estimated using the ambient ratio method. 

4.4.2 Class I Area Impact Analysis 

Sources seeking PSD permits in the state of Oklahoma may be required to perform an impact 

analysis on a Class I area. Contact information for the federal land managers (FLM) for a Class I 

area may be obtained from the AQD. There is one Class I area in the state of Oklahoma: The 

Wichita Mountain Wildlife Preserve managed by the U.S. Fish and Wildlife Service (FWS). Two 

Class I areas are located in the state of Arkansas (these areas may require evaluations from 

sources locating in eastern Oklahoma): The Caney Creek Wilderness Preserve and The Upper 

Buffalo Wilderness Preserve managed by the Forest Service (FS). Another Class I area is 

located in the state of Missouri (this area may require evaluations from sources locating in 

northeastern Oklahoma): The Hercules-Glade Wilderness Preserve managed by the FS. 

Visibility analyses for Class I areas located more than 50 km from a facility must be performed 

using CALPUFF. 

The National Parks Service (NPS) - Air Resources Division, FWS - Air Quality Branch and FS - 

Air Quality Program have produced a guidance document entitled Federal Land Managers’ Air 

Quality Related Values Workgroup (Flag) Phase I Report (December 2000). The guidance set 

forth in this document is followed in PSD review for Class I area impacts. This document may 

be obtained electronically from the AQD or the participating agencies. 
Appendix A 

Oklahoma Modeling Guidance Document 

Point Source Model Input Data For NAAQS Compliance in PSD Demon

40 CFR Part 51, Appendix W, Table 8-2 

Averaging Time Emission Limit X (#/MMBTU)1 Operating Level X (MMBTU/hr)1 Operating 

(e.g., hr/yr, 

Proposed Major New or Modified Source 

Annual & Quarterly 

Maximum allowable emission limit or federally enforceable permit limit. 

Design capacity or federally enforceable permit condition. 

Continuous (i.e., 8,760 h

Short term (≤ 24 hours) 

Maximum allowable emission limit or federally enforceable permit limit. 

Design capacity or federally enforceable permit condition.3

Continuous hours of eacconsideratiometeorologi

Nearby Source(s)4, 6

Annual & Quarterly 

Maximum allowable emission limit or federally enforceable permit limit.5

Actual or design capacity (whichever is greater), or federally enforceable permit condition. 

Actual opeover the mo

Short term (≤ 24 hours) 

Maximum allowable emission limit or federally enforceable permit limit.5

Actual or design capacity (whichever is greater), or federally enforceable permit condition.3

Continuous hours of eaconsideratiometeorologi

Other Source(s)6, 9Annual & Quarterly 

Maximum allowable emission limit or federally enforceable permit limit.5

Annual level when actually operating, averaged over the most recent 2 years.7

Actual opeover the mo

Short term (≤ 24 hours) 

Maximum allowable emission limit or federally enforceable permit limit.5

Annual level when actually operating, averaged over the most recent 2 years.7

Continuous hours of eaconsideratio

meteorologi

1 Terminology applicable to fuel burning sources; analogous terminology (e.g., #/throughput) may be used for ot2 If operation does not occur for all hours of the time period of consideration (e.g., 3 or 24 hours) and th

constrained by a federally enforceable permit condition, an appropriate adjustment to the modeled emission ra
Appendix A 

Oklahoma Modeling Guidance Document 

if operation is only 8:00 a.m. to 4:00 p.m. each day, only these hours will be modeled with emissions from 

emissions should not be averaged across non-operating time periods. 

3 Operating levels such as 50 percent and 75 percent of capacity should be modeled to determine the loa

concentration. 

4 Includes existing facility to which modification is proposed if the emissions from the existing facility will n

modification. Otherwise use the same parameters as for major modification. 

5 See paragraph 9.2.3(c) 6 See paragraph 9.2.3(d) 7 Unless it is determined that this period is not representative. 8 For those permitted sources not yet in operation or that have not established an appropriate factor, continuous 

hours) should be used. 

9 Generally, the ambient impacts from non-nearby background sources can be represented by air quality data 

does not exist. 
Appendix B 

Oklahoma Modeling Guidance Document B-1 

Flare Calculation Derivation 

An American Petroleum Institute (API) publication (API 1969) provides a correlation for flame 

length as a function of the flared gas heat release. This equation was republished and modified 

for a flame tilted at a 45° angle from the vertical in Fundamentals of Stack Gas Dispersion 

(Beychok 1994). The resulting equation provides the vertical height of a flare stack flame. 

0.478 0.00128 H fv = Qc (Eq. 1) 

Where: Hfv = flare stack flame vertical height vector, m 

 Qc = flared gas heat release, Btu/hr 

The equivalent height is then found by summing the height of the flare with the vertical height 

vector of the flame. 

0.478 0.00128 Hequiv = Hactual + Qc (Eq. 2) 

Where: Hequiv = The equivalent height of the flare, m 

 Hactual = The actual height of the stack from the ground, m 

The total plume rise is derived from the initial vertical velocity momentum and the initial 

buoyancy momentum. The buoyancy momentum is essentially a measure of the sensible heat 

emissions from the stack. However, the AERMOD program does not allow the user to directly 

input the heat release. The flux parameter is instead calculated from the temperature differential 

between the stack and ambient air. This is a problem for a flare analysis because the heat release 

is diminished due to radiant heat losses. Therefore, an equivalent diameter is chosen, which 

when combined with the temperature assumption will force the program to calculate a buoyancy 

flux that accounts for the radiant heat loss. This equivalent diameter is back calculated from the 

Briggs’ buoyancy flux parameter, which is derived from the sensible heat emissions. 

The Briggs’ buoyancy flux parameter may be expressed by the following equivalent expressions, 

with the reasonable assumption that combusted stack gas has essentially the same molecular 

weight and specific heat as ambient air. 

( )

s

s s a

T

gv d T T

F

4

2

2 − = (Eq. 3) 

and 

( ) aTa a cp

gQ F

π 1ρ = (Eq. 4) 

Where: g = 9.807 m/sec2

 vs = stack exit velocity, m/sec 

 d = stack exit diameter, m 
Appendix B 

Oklahoma Modeling Guidance Document B-2 

 Q = stack sensible heat emission, cal/sec 

 cpa= specific heat of ambient air, cal/(g-°C) 

 ρa = ambient air density, g/m3

 Ta1 = ambient air temperature, K 

 Ta2 = ambient air temperature, °C 

 Ts = stack gas temperature, K 

 F = buoyancy flux parameter, m4

/sec3

Since g and π are constants and since cpa, Ta, and ρa are essentially constants, it may be inferred 

that the buoyancy flux parameter is a measure of the sensible heat emissions from the stack. So, 

assuming an average annual temperature of 68°F or 20°C, the equation 4 may be restated as 

follows: 

(3.686 10 ) ( ) cal/sec 5 F x Q − = (Eq. 5) 

and 

(2.580 10 ) ( ) BTU/hr 6 F x Q − = (Eq. 6) 

where: F = buoyancy flux parameter, m4

/sec3

Because 55% of the heat is assumed to be lost due to radiation, equation 6 is adjusted specifically 

for flares. 

(1.161 10 ) ( ) BTU/hr 6 F x Q − = (Eq. 7) 

The equivalent diameter may now be found as a function of Q by setting equal equations 7 and 3 

and solving for the radius (r). 

1.758 10 ( ) BTU/hr 4 Dequiv x Q − = (Eq. 8) 

where: Dequiv = the equivalent diameter of the flare, m 

The above guidance is consistent with guidance issued by the Ohio EPA. It differs from EPA 

Region V and Louisiana DEQ guidance with the inclusion of the stack height adjustment; 

however, this adjustment is made within the SCREEN3 flare option and is appropriate for the 

AERMOD point source option. It differs from Texas guidance with the inclusion of the stack 

height adjustment and an ambient temperature assumption. Texas guidance is based on an 

ambient temperature of 35°C. Because the ambient temperature is important in both the heat 

release calculation and the equivalent diameter calculation, care should be exercised in modeling 

specific events. Rather than using the standard guidance above, specific events should be 

modeled with equivalent parameters based on the actual ambient conditions. 
Appendix C 

Oklahoma Modeling Guidance Document C-1 

Modeling Protocol Submission Outline

1. Project Overview 

1.1. Discussion of Plant Processes

1.2. References to Regulatory Applicability

2. Emission Sources 

2.1. Source Description

2.2. Location of Emissions 

2.3. Pollutants

3. Impact Assessment Tools and Techniques 

3.1. Description of Models to Be Used 

3.1.1. Version 

3.1.2. Circumstance of use, i.e., SCREEN3 for initial toxic MAAC screening

3.2. Discussion on Use of Ratio method

3.3. Discussion on Merging Stacks 

3.4. For PSD Analysis 

3.4.1. Discussion on Use of “10 D Rule”

3.4.2. Discussion on method relied upon for Ozone impact assessment

3.4.3. Discussion on Use of Visibility Screening Tools for Class I Areas

4. Area Maps and Facility Plot Plans (if available) 

4.1. Clearly Marked Scale

4.2. Property Lines

4.3. Fence Lines 

4.4. Downwash Structures

4.5. True-north Arrow

4.6. UTM Coordinates for Vertical and Horizontal Borders

4.7. Reference UTM Coordinates and Locations of All Emission Points

4.8. Identification of Sensitive Receptors and Nearest Residents (Area Map Only)

4.9. For NAAQS Analysis Identification of Any State/Local/On-site Ambient Air Monitoring 

Sites Used for Background Concentrations 

4.10. For PSD Applications, identification of PSD Class I areas within 300 km (186.4 

miles) or within 10D of emissions.

4.11. Provide an Accompanying List of Structures with UTM Locations, Heights, and 

Model Labels or ID Numbers 

5. Modeling Emission Inventory 

5.1. On-Site Sources 

5.1.1. Assumptions 

5.1.2. Table of Source Input Data (if available) 

5.2. Discussion of Methodology for Obtaining Off-property Modeling Parameters 

6. Air Quality Monitoring Data For NAAQS Compliance 

6.1. Discussion on the Issue of Pre-construction Monitoring

6.2. Proposed Monitoring Sites

6.3. Discussion on How Concentrations will be Adjusted for Background Sources 

Specifically Modeled.

7. Land Use 
Appendix C 

Oklahoma Modeling Guidance Document C-2 

7.1. Auer Land-use Analysis 

7.2. Copy of USGS map (if used in analysis) 

8. Receptor Grid 

8.1. Discussion on Grid Type 

8.2. Discussion on Receptor Placement 

8.3. Diagram of Each Grid Type w/Labels 

9. Meteorological Data 

9.1. Surface Station

9.2. Upper-air Station

9.3. Period of Record

10. Discussion on Method of Evaluation Additional Impacts Analysis (PSD) 

11. Class I Area Impacts Analysis (PSD) 

11.1. Discussion of Method of Analysis

11.2. AQRV of concern
Appendix D 

Oklahoma Modeling Guidance Document D-1 

Final Submission Outline

12. Project Overview 

12.1. Discussion of Plant Processes

12.2. References to Regulatory Applicability

13. Emission Sources 

13.1. Source Description

13.2. Location of Emissions 

13.3. Table of Emissions by Source and Pollutants

14. Impact Assessment Tools and Techniques 

14.1. Description of Models Used 

14.1.1. Version 

14.1.2. Circumstance of use, i.e., SCREEN3 for initial toxic MAAC screening

14.2. Discussion on Use of Ratio method

14.3. Discussion on Collocating Sources

14.4. For PSD Analysis 

14.4.1. Discussion on Use of “10 D Rule”

14.4.2. Discussion on method relied upon for Ozone impact assessment

14.4.3. Discussion on Use of Visibility Screening Tools for Class I Areas

15. Area Maps and Facility Plot Plans 

15.1. Clearly Marked Scale

15.2. Property Lines

15.3. Fence Lines

15.4. Downwash Structures

15.5. True-north Arrow

15.6. UTM Coordinates for Vertical and Horizontal Borders

15.7. Reference UTM Coordinates and Locations of All Emission Points

15.8. Identification of Sensitive Receptors and Nearest Residents (Area Map Only)

15.9. Identification of Any State/Local/On-site Ambient Air Monitoring Sites Used for 

Background Concentrations 

15.10. For PSD Applications, identification of PSD Class I areas within 300 km (186.4 

miles) or within 10D of emissions.

15.11. Provide an Accompanying List of Structures with UTM Locations, Heights, and 

Model Labels or ID Numbers 

16. Air Quality Monitoring Data 

16.1. Discussion on the Issue of Pre-construction Monitoring

16.2. Summary Information for Monitoring Sites

16.2.1. Year of Observation

16.2.2. Location

16.2.3. First, Second, and Fourth High Concentrations

16.2.4. Annual Arithmetic Mean Concentration

16.3. Discussion on How Concentrations will be Adjusted for Background Sources 

Specifically Modeled.

17. Modeling Emission Inventory 

17.1. On-Site Sources 
Appendix D 

Oklahoma Modeling Guidance Document D-2 

17.1.1. Assumptions 

17.1.2. Table of Source Input Data 

17.2. Background Sources for NAAQS and Increment Modeling 

17.2.1. Discussion of Methodology for Obtaining Off-property Modeling Parameters 

17.2.2. “10 D Rule” Table 

17.2.2.1. All Sources Within 50 km 

17.2.2.2. UTM Coordinates 

17.2.2.3. Distance from Significant Impact Radius 

17.2.2.4. Total Emissions 

17.2.3. Table of Source Modeling Parameters 

18. Land Use 

18.1. Auer Land-use Analysis 

18.2. Copy of USGS map (if used in analysis) 

19. Receptor Grid 

19.1. Terrain 

19.1.1. Discussion on Terrain for Individual Receptors 

19.1.2. For PSD Applications Attach Contour Plots 

19.2. Design 

19.2.1. Discussion on Grid Type 

19.2.2. Diagram of Each Grid Type w/Labels 

20. Meteorological Data 

20.1. Surface Station

20.2. Upper-air Station

20.3. Period of Record

21. Modeling Results 

21.1. Summary Table for Each Pollutant 

21.1.1. Listing Standard, (NAAQS, Increment, or MAAC) 

21.1.2. Listing Monitored Background Concentrations 

21.2. For Each Standard, Receptor Grid Plots w/Appropriate Concentration 

21.3. For PSD Applications, Area Plot w/Concentration Contour Plot 

22. Additional Impacts Analysis (PSD) 

22.1. Discussion on Method of Evaluation

22.2. Evaluation Results on Growth, Soils and Vegetation

23. Class I Area Impacts Analysis (PSD) 

23.1. Discussion of Method of Analysis

23.2. Results of Analysis on effect on AQRV

24. Attached Disks of All Model Input and Output files 
Appendix E – Mesonet Site Information 

Oklahoma Modeling Guidance Document E-1 

Station Identifiers Elev. 

# ID Name CITY County Lat. Long. (m) 

110 ACME Acme Rush Springs Grady 34.8083 -98.0233 397 

1 ADAX Ada Ada Pontotoc 34.7985 -96.6691 295 

2 ALTU Altus Altus Jackson 34.5872 -99.3381 416 

116 ALV2 Alva Alva Woods 36.7082 -98.7097 439 

4 ANTL Antlers Antlers Pushmataha 34.2244 -95.7006 179 

111 APAC Apache Apache Caddo 34.9142 -98.2922 440 

126 ARD2 Ardmore Ardmore Carter 34.1926 -97.0857 266 

6 ARNE Arnett Arnett Ellis 36.0720 -99.9031 719 

8 BEAV Beaver Beaver Beaver 36.8025 -100.5300 758 

9 BESS Bessie Bessie Washita 35.4019 -99.0585 511 

10 BIXB Bixby Bixby Tulsa 35.9631 -95.8662 184 

11 BLAC Blackwell Blackwell Kay 36.7544 -97.2545 304 

12 BOIS Boise City Boise City Cimarron 36.6926 -102.4970 1267 

13 BOWL Bowlegs Bowlegs Seminole 35.1716 -96.6312 281 

14 BREC Breckinridge Breckinridge Garfield 36.4120 -97.6939 352 

15 BRIS Bristow Bristow Creek 35.7805 -96.3540 239 

124 BROK Broken Bow Broken Bow McCurtain 34.0433 -94.6244 113 

16 BUFF Buffalo Buffalo Harper 36.8313 -99.6410 559 

17 BURB Burbank Burbank Osage 36.6346 -96.8105 301 

18 BURN Burneyville Burneyville Love 33.8938 -97.2692 228 

19 BUTL Butler Butler Custer 35.5915 -99.2706 520 

20 BYAR Byars Byars Garvin 34.8497 -97.0033 345 

21 CALV Calvin Calvin Hughes 34.9924 -96.3342 234 

22 CAMA Camargo Camargo Dewey 36.0287 -99.3465 589 

23 CENT Centrahoma Centrahoma Coal 34.6090 -96.3331 208 

24 CHAN Chandler Sparks Lincoln 35.6528 -96.8041 291 

25 CHER Cherokee Cherokee Alfalfa 36.7481 -98.3627 362 

26 CHEY Cheyenne Cheyenne Roger Mills 35.5462 -99.7279 694 

27 CHIC Chickasha Chickasha Grady 35.0324 -97.9145 328 

29 CLAY Clayton Clayton Pushmataha 34.6566 -95.3260 186 

30 CLOU Cloudy Cloudy Pushmataha 34.2232 -95.2487 221 

122 CLRM Claremore Claremore Rogers 36.3211 -95.6462 207 

31 COOK Cookson Marble City Cherokee 35.6800 -94.8490 299 

32 COPA Copan Copan Washington 36.9099 -95.8855 250 

33 DURA Durant Durant Bryan 33.9208 -96.3203 197 

34 ELRE El Reno El Reno Canadian 35.5485 -98.0365 419 

35 ERIC Erick Erick Beckham 35.2049 -99.8034 603 

36 EUFA Eufaula Eufaula McIntosh 35.3032 -95.6571 200 

37 FAIR Fairview Fairview Major 36.2635 -98.4977 405 

38 FORA Foraker Foraker Osage 36.8405 -96.4278 330 

39 FREE Freedom Freedom Woodward 36.7256 -99.1423 530 

40 FTCB Fort Cobb Fort Cobb Caddo 35.1489 -98.4661 422 

41 GOOD Goodwell Goodwell Texas 36.6018 -101.6010 997 

117 GRA2 Grandfield Grandfield Tillman 34.2392 -98.7444 341 

43 GUTH Guthrie Guthrie Logan 35.8489 -97.4798 330 

44 HASK Haskell Haskell Muskogee 35.7480 -95.6405 183 
Appendix E – Mesonet Site Information 

Oklahoma Modeling Guidance Document E-2 

Station Identifiers Elev. 

# ID Name CITY County Lat. Long. (m) 

113 HECT Hectorville Hectorville Okmulgee 35.8416 -96.0024 243 

45 HINT Hinton Hinton Caddo 35.4844 -98.4815 493 

46 HOBA Hobart Hobart Kiowa 34.9897 -99.0528 478 

47 HOLL Hollis Gould Harmon 34.6855 -99.8333 497 

48 HOOK Hooker Hooker Texas 36.8552 -101.225 912 

49 HUGO Hugo Hugo Choctaw 34.0308 -95.5401 175 

50 IDAB Idabel Idabel McCurtain 33.8301 -94.8803 110 

120 INOL Inola Inola Rogers 36.1425 -95.4507 190 

51 JAYX Jay Jay Delaware 36.4821 -94.7829 304 

52 KENT Kenton Kenton Cimarron 36.8294 -102.8780 1322 

53 KETC Ketchum Ranch Velma Stephens 34.5289 -97.7648 341 

54 KING Kingfisher Kingfisher Kingfisher 35.8805 -97.9112 319 

55 LAHO Lahoma Lahoma Major 36.3844 -98.1114 396 

56 LANE Lane Lane Atoka 34.3088 -95.9972 181 

57 MADI Madill Lebanon Marshall 34.0358 -96.9439 232 

58 MANG Mangum Mangum Greer 34.8359 -99.4240 460 

59 MARE Marena Coyle Payne 36.0643 -97.2127 327 

61 MAYR May Ranch Freedom Woods 36.9871 -99.0111 555 

62 MCAL McAlester McAlester Pittsburg 34.8823 -95.7810 230 

63 MEDF Medford Medford Grant 36.7924 -97.7458 332 

64 MEDI Medicine Park Med. Park Comanche 34.7292 -98.5694 487 

65 MIAM Miami Miami Ottawa 36.8883 -94.8444 247 

66 MINC Minco Minco Grady 35.2723 -97.9555 430 

125 MRSH Marshall Marshall Logan 36.1169 -97.6069 311 

67 MTHE Mt Herman Smithville McCurtain 34.3107 -94.8228 285 

68 NEWK Newkirk Newkirk Kay 36.8981 -96.9104 366 

109 NINN Ninnekah Ninnekah Grady 34.9677 -97.9520 356 

70 NOWA Nowata Delaware Nowata 36.7437 -95.6080 206 

121 NRMN Norman Norman Cleveland 35.2361 -97.4649 357 

71 OILT Oilton Oilton Creek 36.0313 -96.4975 255 

72 OKEM Okemah Okemah Okfuskee 35.4317 -96.2627 263 

73 OKMU Okmulgee Morris Okmulgee 35.5821 -95.9147 205 

74 PAUL Pauls Valley Pauls Valley Garvin 34.7155 -97.2292 291 

75 PAWN Pawnee Pawnee Pawnee 36.3611 -96.7699 283 

76 PERK Perkins Perkins Payne 35.9987 -97.0483 292 

118 PORT Porter Clarksville Wagoner 35.8257 -95.5598 193 

77 PRYO Pryor Adair Mayes 36.3691 -95.2714 201 

78 PUTN Putnam Putnam Dewey 35.8990 -98.9604 589 

79 REDR Red Rock Red Rock Noble 36.3559 -97.1531 293 

80 RETR Retrop Willow Washita 35.1228 -99.3600 538 

81 RING Ringling Ringling Jefferson 34.1937 -97.5881 283 

82 SALL Sallisaw Sallisaw Sequoyah 35.4382 -94.7981 157 

83 SEIL Seiling Seiling Woodward 36.1903 -99.0403 545 

84 SHAW Shawnee Shawnee Pottawatomie 35.3649 -96.9482 328 

85 SKIA Skiatook Skiatook Osage 36.4153 -96.0371 282 

86 SLAP Slapout Slapout Beaver 36.5975 -100.2620 774 
Appendix E – Mesonet Site Information 

Oklahoma Modeling Guidance Document E-3 

Station Identifiers Elev. 

# ID Name CITY County Lat. Long. (m) 

87 SPEN Spencer Spencer Oklahoma 35.5421 -97.3415 373 

88 STIG Stigler Stigler Haskell 35.2653 -95.1812 173 

89 STIL Stillwater Stillwater Payne 36.1209 -97.0953 272 

90 STUA Stuart Stuart Pittsburg 34.8764 -96.0698 256 

91 SULP Sulphur Sulphur Murray 34.5661 -96.9505 320 

92 TAHL Tahlequah Tahlequah Cherokee 35.9724 -94.9867 290 

93 TALI Talihina Talihina LeFlore 34.7107 -95.0115 204 

94 TIPT Tipton Tipton Tillman 34.4397 -99.1376 387 

95 TISH Tishomingo Tishomingo Johnston 34.3326 -96.6790 268 

115 VANO Vanoss Vanoss Pontotoc 34.7915 -96.8438 320 

97 VINI Vinita Centralia Craig 36.7754 -95.2209 236 

98 WALT Walters Walters Cotton 34.3647 -98.3203 308 

99 WASH Washington Washington McClain 34.9822 -97.5211 345 

100 WATO Watonga Watonga Blaine 35.8419 -98.5262 517 

101 WAUR Waurika Waurika Jefferson 34.1678 -97.9882 283 

102 WEAT Weatherford Weatherford Custer 35.5083 -98.7751 538 

103 WEBB Webbers Falls Webbers Falls Muskogee 35.4730 -95.1321 145 

104 WEST Westville Westville Adair 36.0110 -94.6450 348 

105 WILB Wilburton Wilburton Latimer 34.9009 -95.3481 199 

106 WIST Wister Wister LeFlore 34.9843 -94.6878 143 

107 WOOD Woodward Woodward Woodward 36.4233 -99.4168 625 

108 WYNO Wynona Wynona Osage 36.5181 -96.3422 269 
Appendix F – ISH and FLS Sites for each Mesonet Site 

 & Surface Moisture Conditions for each Season 

Oklahoma Modeling Guidance Document F-1 

STID UAS SFCS 

W

N

0

1 

S

P

0

1 

S

M

0

1 

F

L

0

1 

W

N

0

2 

S

P

0

2 

S

M

0

2 

F

L

0

2 

W

N

0

3 

S

P

0

3 

S

M

0

3 

F

L

0

3 

W

N

0

4 

S

P

0

4 

S

M

0

4 

F

L

0

4 

W

N

0

5 

S

P

0

5 

S

M

0

5 

F

L

0

5 

ACME OUN KLAW D D D

ADAX OUN KMLC D D

ALTU OUN KFDR D D D

ALV2 OUN KP28 W W D W D

ANTL FWD KPRX D D

APAC OUN KLAW D D D

ARD2 FWD K1FO W W D D

ARNE AMA KGAG W D D W D W D

BEAV DDC KLBL W D W W D D

BESS OUN KCSM D D D

BIXB OUN KRVS D D D

BLAC OUN KPNC D D

BOIS AMA KDHT D D D D D W D D

BOWL OUN KTIK D D

BREC OUN KGOK D D D

BRIS OUN KRVS D D

BROK SHV KTXK D D

BUFF DDC KGAG W D W D W D

BURB OUN KPNC D D

BURN FWD K1FO W W D D

BUTL OUN KCSM W D D D

BYAR OUN KOUN W D D

CALV OUN KMLC D D

CAMA OUN KCSM W D D D D

CENT OUN KMLC D D

CHAN OUN KSWO D D

CHER OUN KP28 D D

CHEY AMA KCSM W D D D D

CHIC OUN KOUN D D D

CLAY OUN KMLC D D

CLOU SHV KPRX D D D

CLRM OUN KTUL D D D

COOK SGF KMKO D D D

COPA SGF KBVO D D

DURA FWD K1FO W D D D

ELRE OUN KOKC D D D

ERIC AMA KCSM W D D D

EUFA OUN KMLC D D D

FAIR OUN KCSM W D D D
Appendix F – ISH and FLS Sites for each Mesonet Site 

 & Surface Moisture Conditions for each Season 

Oklahoma Modeling Guidance Document F-2 

STID UAS SFCS 

W

N

0

1 

S

P

0

1 

S

M

0

1 

F

L

0

1 

W

N

0

2 

S

P

0

2 

S

M

0

2 

F

L

0

2 

W

N

0

3 

S

P

0

3 

S

M

0

3 

F

L

0

3 

W

N

0

4 

S

P

0

4 

S

M

0

4 

F

L

0

4 

W

N

0

5 

S

P

0

5 

S

M

0

5 

F

L

0

5 

FORA OUN KBVO D D

FREE DDC KGAG W D D W D W D

FTCB OUN KHBR D D D

GOOD AMA KLBL D D W W D D

GRA2 OUN KFDR D D D D

GUTH OUN KGOK D D

HASK OUN KMKO D D D

HECT OUN KRVS D D D

HINT OUN KCSM D D D

HOBA OUN KHBR D D D

HOLL AMA KCDS D D D

HOOK DDC KLBL W D D W W D D

HUGO SHV KPRX D D D

IDAB SHV KPRX D D

INOL SGF KTUL D D D

JAYX SGF KSLG D D D

KENT AMA KCAO W D D D D W W D D

KETC OUN KLAW W D W D D

KING OUN KPWA D D D

LAHO OUN KGOK W D D D

LANE FWD KMLC D D

MADI FWD K1FO W D D

MANG OUN KHBR D D D

MARE OUN KSWO D D

MAYR DDC KP28 W W D W D

MCAL OUN KMLC D D

MEDF OUN KPNC D D D

MEDI OUN KLAW D D D

MIAM SGF KJLN D D D

MINC OUN KOKC D D D

MRSH OUN KGOK D D

MTHE SHV KMWT D D

NEWK OUN KPNC D D

NINN OUN KOUN D D D

NOWA SGF KBVO D D D

NRMN OUN KOUN D D

OILT OUN KRVS D D

OKEM OUN KRVS D D

OKMU OUN KRVS D D D
Appendix F – ISH and FLS Sites for each Mesonet Site 

 & Surface Moisture Conditions for each Season 

Oklahoma Modeling Guidance Document F-3 

STID UAS SFCS 

W

N

0

1 

S

P

0

1 

S

M

0

1 

F

L

0

1 

W

N

0

2 

S

P

0

2 

S

M

0

2 

F

L

0

2 

W

N

0

3 

S

P

0

3 

S

M

0

3 

F

L

0

3 

W

N

0

4 

S

P

0

4 

S

M

0

4 

F

L

0

4 

W

N

0

5 

S

P

0

5 

S

M

0

5 

F

L

0

5 

PAUL OUN K1FO W D D

PAWN OUN KSWO D D

PERK OUN KSWO D D

PORT OUN KMKO D D D

PRYO SGF KTUL D D D

PUTN OUN KCSM W D D D

REDR OUN KSWO D D

RETR OUN KHBR D D D

RING FWD K1FO W D W D D

SALL LZK KFSM D D D

SEIL OUN KGAG W D D W D W D

SHAW OUN KTIK D D

SKIA OUN KTUL D D

SLAP DDC KGAG W D W D D

SPEN OUN KTIK D D

STIG LZK KFSM D D D

STIL OUN KSWO D D

STUA OUN KMLC D D

SULP OUN K1FO W W D D

TAHL SGF KMKO D D D

TALI LZK KMLC D D

TIPT OUN KFDR D D D D

TISH FWD K1FO W D D

VANO OUN KOUN D D

VINI SGF KBVO D D D

WALT OUN KLAW D D D

WASH OUN KOUN D D

WATO OUN KPWA D D D

WAUR FWD KSPS W D W D D

WEAT OUN KCSM W D D D

WEBB OUN KFSM D D D

WEST SGF KSLG D D D

WILB OUN KMLC D D

WIST LZK KFSM D D

WOOD DDC KGAG W D D W D W D

WYNO OUN KBVO D D

STID – Mesonet Station ID; UAS - Upper Air Station Call Identifier; SFCS - ISH Surface 

Station Call Identifier; WN - Winter; SP - Spring; SM - Summer; FL - Fall; D – Dry; W - Wet. 

If no value is assigned to the time period then it is considered average surface moisture. 
References

Oklahoma Modeling Guidance Document R-1 

American Petroleum Institute (API). 1969. Guide for pressure relief and depressurizing 

systems. API RP 521, First Edition. 

Auer, A. H. 1978. Correlation of Land Use and Cover with Meteorological Anomalies, Journal 

of Applied Meteorology, 17:636-643. 

Beychok, Milton R. 1994. Fundamentals of Stack Gas Dispersion. 3rd ed. Irvine, California: 

Milton Beychok 

Davies, M. J. E., and D. M. Leahey. 1984. Observation of Plume Rise from Sour Gas Flares. 

Atmospheric Environment Volume 18, No. 5: 917-922. 

Koerber, Michael, Regional Meteorologist, EPA Region V. Letter to Regions I-IV, VI-X, 28 July 

1986. 

Louisiana Department of Environmental Quality (LDEQ). 1999. Air Quality Modeling 

Procedures. Baton Rouge, Louisiana: LDEQ 

Ohio Environmental Protection Agency (Ohio EPA). Air Dispersion Modeling Guidance, 

Engineering Guide No. 69. Columbus, Ohio: Ohio EPA. 

Scheffe, Richard D. 1988. VOC/NOX Point Source Screening Tables, draft. 

Texas Natural Resource Conservation Commission (TNRCC). 1999. Air Quality Modeling 

Guidelines. Austin, Texas: TNRCC. 

United States Environmental Protection Agency (EPA). 1990. Draft New Source Review 

Workshop Manual. Research Triangle Park, North Carolina: EPA 
Index

Oklahoma Modeling Guidance Document I-1 

1

10-D Rule 15 

A

AERMAP 12 

AERMET 3 

AERMOD 3 

AERSCREEN 3 

Appendix A 1 

Appendix W 2 

Area Source 5 

ARM 17 

Auer Land Use 11 

B

BPIP-Prime 10 

C

CALPUFF 3 

CAMx 3 

Class I 23 

Class II 22 

D

DEM 11, 12 

Deposition 18 

Doors 9 

downwash 2, 5, 9, 10 

F

Flares 8, 1 

Fugitive Source 5 

G

GEP 9, 16 

H

hydrogen sulfide 2 

I

Increment 20 

ISC3 8, 18 

ISC-PRIME 16 

L

Land Use 10 

M

MAAC 2, 18 

Mesonet 13 

Met Data 9, 12 

Monitoring 16 

N

NAAQS 1, 2, 19, 20, 22 

NO2 17 

NWS 13 

O

Open pit 7 

Ozone 18 

P

Pasquill Gifford 2 

plume rise 8, 1 

PM10 17 

Point Source 5 

Population Density 11 

PSD 1, 3, 16, 18, 19, 20 

Pseudo-Point Sources 8 

R

rain caps 8, 9 

Receptor 16 

Refined 2, 11 

Region VI 1, 2 

release height 5, 6, 7 

Road Emissions 6 

RPM 3 

Rural 10 

S

Scheffe Tables 3 

SCREEN3 2, 3, 8, 10, 2 

Sensitive Area 23 

SIL 20 

SO2 19 

T

TAC 2, 18 

terrain 2, 9 

Terrain 11 

Texas 6, 2 

Tilted stacks 8 

Title V 1 

TV 19 
Index

Oklahoma Modeling Guidance Document I-2 

U

Urban 10 

USGS 11, 12 

UTM 7, 12 

V

Vents 9 

VISCREEN 23 

Visibility 22 

Volume Source 5, 7