Appendix B. 

Technical Support Document for

Arkansas Regional Haze Best Available Retrofit Technology 

(BART) Modeling Protocol Review

Prepared by:

Michael Feldman

March 2015
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Table of Contents

Table of Contents................................................................................................................ ii

Chapter 1: Introduction ....................................................................................................... 3

Chapter 2: BART Guidelines and Modeling Protocols ...................................................... 5

2.1 Background and Introduction ................................................................................... 5

2.2 Calculation of Visibility Impact................................................................................ 7

2.2.1. IMPROVE Equation ......................................................................................... 8

2.2.2 Revised IMPROVE Equation ............................................................................ 8

2.2.3 Deciview Impact Calculation........................................................................... 10

2.3. CALMET/CALPUFF modeling protocol.............................................................. 11

2.4. EPA Conclusion..................................................................................................... 14
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Chapter 1: Introduction

Arkansas submitted a Regional Haze (RH) State Implementation Plan (SIP) to 

address the first regional haze implementation period on September 23, 2008, and August 

3, 2010, and submitted supplemental information on September 27, 2011. On March 12, 

2012, the EPA partially approved and partially disapproved the RH SIP submitted by 

Arkansas (77 FR 14604). This included a disapproval of some of the Best Available 

Retrofit Technology (BART) determinations made by Arkansas. See the Technical 

Support Document (TSD) that accompanied that action for our review of the visibility 

modeling submitted by Arkansas Department of Environmental Quality (ADEQ) to 

support the original BART determinations. Following EPA’s partial disapproval action, 

the ADEQ worked closely with the BART facilities and with EPA Region 6 to revise the 

RH SIP. Trinity Consultants, on behalf of each BART facility, performed five-factor 

analyses to correct the State’s BART decisions that were disapproved by the EPA. As 

part of our proposed Federal Implementation Plan (FIP), we have reviewed the final 

version of each BART analysis performed by Trinity Consultants that has been provided 

to us. ADEQ developed a visibility modeling protocol in support of their 2008 submitted 

RH SIP.1 ADEQ worked with EPA and Trinity to update this modeling protocol in 

2012.2In general, the revisions to the modeling protocol were made to utilize an existing 

meteorological database that incorporated monitored surface and aloft measurements, and 

the use of the revised IMPROVE equation to calculate extinction. This visibility 

modeling protocol was followed in the technical work performed by Trinity Consultants3

for each facility and is described in detail in this document. Modeled emission rates and 

results of visibility modeling for specific BART sources are discussed under the full fivefactor BART analysis in the main Technical Support Document for this proposed 

rulemaking. 

AECC Bailey Unit 1 and McClellan Unit 1, American Electric Power (AEP) Flint 

Creek Unit 1, Entergy White Bluff Power Plant Units 1 and 2, Entergy Lake Catherine 

Unit 4, and Domtar Ashdown Paper Mill No. 1 and No. 2 power boilers have been 

determined to be subject-to-BART. See 77 FR 14604. Revised BART modeling was 

performed by Trinity for all the BART facilities following the same general modeling 

protocol and using the same meteorological data inputs as discussed in the following 

chapter. 

 

1

. Draft Best Available Retrofit Technology (BART) Modeling Protocol June 7, 2006. Available as 

Appendix 9.2A of the 2010 Arkansas Regional Haze SIP revision and in the docket for this proposed 

rulemaking. 

2

July 26, 2012 ADEQ Best Available Retrofit Technology (BART) Modeling Protocol Addendum and 

April 26, 2012 letter from Guy Donaldson, Chief of Air Planning Section at EPA Region 6, to Anthony 

Davis, ADEQ. A copy of this BART Modeling Protocol Addendum and letter can be found in the docket 

for this proposed rulemaking.

3 A copy of the final version of each BART analysis performed by Trinity Consultants on behalf of the 

BART sources, upon which our analysis is largely based, can be found in the docket for this proposed 

rulemaking. 
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Table 1-1. Subject-to-BART sources

FACILITY NAME UNIT ID

American Electric Power – Flint 

Creek Plant

SN-01 - Boiler

AR Electric Cooperative – Bailey 

Generating Station

SN-01 – Boiler

AR Electric Cooperative – John 

L. McClellan Generating Station

SN-01 - Boiler

Entergy – Lake Catherine SN-02 – Unit 4 Boiler

Entergy – White Bluff

SN-01 – Unit 1

SN-02 – Unit 2

SN-05 – Auxiliary Boiler

Domtar – Ashdown SN-03 – #1 Power Boiler

SN-05 - #2 Power Boiler
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Chapter 2: BART Guidelines and Modeling Protocols

2.1 Background and Introduction

The BART analysis includes engineering and modeling methods and procedures 

used to determine the appropriate controls for the subject-to-BART units to reduce the 

source’s contribution to pollutant concentrations that result in visibility impairment in the 

surrounding Class I areas. The final factor to consider under EPA’s BART Guidelines is 

the degree of visibility improvement from the BART control options4. The BART 

guidelines recommend use of the CALPUFF air quality dispersion model to estimate the 

visibility improvements at each Class I area, typically within roughly a 300 km (186 

mile) radius of the source, of alternative control technologies, and to compare these to 

each other and to the impact of the baseline, or current, source configuration. The four

Class I Areas within approximately 300 km of the facilities were included in the

modeling analyses. These Class I areas are listed in Table 2-1. The location of the 

facilities and Class I areas are shown in the map in Figure 2-1. We note that, as shown in 

Figure 2-1, Sipsey Wilderness is more than 300 km from any of the evaluated sources 

and was not included in the revised visibility impact modeling evaluations.

Table 2-1. Class I Areas

Class I Area State Agency IMPROVE 

monitor

Caney Creek Wilderness Area AR USFS CACR

Hercules Glades Wilderness Area MO USFS HEGL

Upper Buffalo Wilderness Area AR USFS UPBU

Mingo Wilderness Area MO FWS MING

 

4 59 FR 39104, 39170 (July 6, 2005).
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Figure 2-1. Location of Sources and Class I Areas

Trinity Consultants conducted the updated visibility modeling for all the subjectto-BART sources and this modeling was reviewed by EPA as part of our BART 

determination. The revised modeling performed by Trinity Consultants and described in 

this document utilized an updated modeling protocol developed by ADEQ and Trinity 

after discussions with EPA.5 The modeling protocol is discussed here. See the TSD and 

the Federal Register notice for this proposed rulemaking for discussion of modeled 

emissions and visibility modeling results.

Under the BART guidelines6, the measure of the visibility improvement to be 

used in comparisons between various control scenarios is the 98th percentile of impacts 

expressed as 24-hour averages of delta deciviews relative to natural background, as 

estimated using the CALPUFF air quality modeling system. The meaning of this is 

 

5

July 26, 2012 ADEQ Best Available Retrofit Technology (BART) Modeling Protocol Addendum and 

April 26, 2012 letter from Guy Donaldson, Chief of Air Planning Section at EPA Region 6, to Anthony 

Davis, ADEQ. A copy of this BART Modeling Protocol Addendum and letter can be found in the docket 

for this proposed rulemaking.

6 Appendix Y to 40 CFR 51.
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described next, followed by particulars of the application of CALPUFF to the individual

BART determinations.

Table 2-2. CALPUFF system modeling components utilized by Trinity

Processor Version Level

TERREL 3.3 030402

CTGCOMP 2.21 030402

CTGPROC 2.63 050128

MAKEGEO 2.2 030402

CALMET 5.53a 040716

CALPUFF 5.8 070623

POSTUTIL 1.3 030402

CALPOST 6.221 080724

2.2 Calculation of Visibility Impact

Under the RHR, visibility is measured in deciviews. Visibility is traditionally 

described in terms of visual range in kilometers or miles. However, the visual range 

scale does not correspond to how people perceive visibility: a given increase in visual 

range is perceived differently depending on how good the original visibility was (that is, 

it is not on a linear scale). The deciview scale is designed to address this problem. It is 

linear with respect to perceived visual changes over its entire range, analogous to the 

decibel scale for sound: a given change in deciviews will be perceived as the same 

amount of visibility change, whatever the original visibility was. The defining equation 

is: 

deciviews = 10*ln(bext / 10) (1)

where ln is the natural logarithm, and extinction bext is the fraction of light scattered out 

of a viewing path. Extinction increases with the amount of pollution (bext is in units of 

1/Mm, “inverse megameters”). Lower deciview values represent better visibility, more 

pristine atmospheres, and greater visual range, while increasing deciview values represent 

increasingly poor visibility. An increase of 1 deciview corresponds to about a 10% 

increase in extinction. (Deciviews are related to the more traditional visual range 

according to dv = 10*ln(391 / visual range)). An eligible BART source with a predicted 

impact of 0.5 dv or more of impairment in a Class I area “contributes” to visibility 

impairment and is subject to BART. 70 FR 39104, 39121 (July 6, 2005).

Under the BART guidelines, deciviews are estimated using the CALPUFF air 

quality model. CALPUFF predicts 24-hour average pollutant concentrations based on 

source emissions and how they disperse in the atmosphere. The CALPUFF modeling 

includes source emissions of the following visibility-impairing pollutants: SO2, SO4, 

NOx, secondary organic aerosol (SOA), fine particulate matter (PMF), coarse particulate 

matter (PMC), and elemental carbon (EC). CALPUFF incorporates a semi-empirical 
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chemical module that simulates the conversion of SO2 to particulate sulfate and NOx to 

particulate nitrate, at a rate dependent on meteorological conditions and background 

ozone concentration. These concentrations are converted to deciviews by the CALPOST 

post-processor in two steps.

2.2.1. IMPROVE Equation

Under the original IMPROVE7equation, extinction (bext) is estimated from the 

predicted concentrations of various pollutants: 

bext = 3 * f(RH) * [sulfate] 

+ 3 * f(RH) * [nitrate] 

+ 4 * [organic mass] 

+ 10 * [elemental carbon] 

+ 1 * [fine soil] 

+ 0.6 * [coarse mass] 

+ 10

The 10 is for Rayleigh scattering, which is due to the interaction of light with molecules 

of air itself with no pollutants. The f(RH) is a water growth factor for sulfate and nitrate; 

its value depends on relative humidity (RH), ranging from 1 at low humidity to 18 at 98% 

humidity.

2.2.2 Revised IMPROVE Equation

The Trinity revised modeling used the “revised” IMPROVE equation8to calculate 

light extinction. Sometimes the revised IMPROVE equation is called the “New” 

Improve equation. The revised IMPROVE equation is used to convert measured or 

modeled concentrations into extinction for each pollutant chemical species, and then total 

them up, accounting for the effect of relative humidity.

Revised IMPROVE equation:

bext = 2.2 * fs(RH) * [small sulfate] + 4.8 * fL(RH) * [large sulfate] 

+ 2.4 * fs(RH) * [small nitrate] + 5.1 * fL(RH) * [large nitrate]

+ 2.8 * [small organic mass] + 6.1 * [large organic mass]

+ 10 * [elemental carbon]

+ 1 * [fine soil]

 

7

Interagency Monitoring of Protected Visual Environments (IMPROVE) is a network of monitors in 

various Class I Areas, established to assess visibility impairment and its causes. The IMPROVE equation 

is used to converted monitored concentrations into extinction, a measure of visibility. See: 

http://vista.cira.colostate.edu/improve/

8 Pitchford, M. L., W. C. Malm, B. A. Schichtel, N. Kumar, D. Lowenthal and J. L. Hand, Revised 

algorithm for estimating light extinction from IMPROVE particle speciation data, Journal of the Air & 

Waste Management Association, 57, 1326-1336, 2007.
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+ 1.7 * fss(RH) * [sea salt]

+ 0.6 * [coarse mass]

+ Rayleigh scattering (site-specific)

+ 0.33 * [NO2(ppb)]

Sulfate is assumed to be all “large sulfate” if total sulfate is over 20 μg/m3, otherwise its 

fraction of the total is assumed to increase uniformly between 0 and 1 when the total is in 

the range between 0 and 20 (i.e. large sulfate = (total sulfate/20)*total). A similar 

definition applies for nitrate and for organic mass. The organic mass is assumed to be 1.8 

times the organic carbon mass that is measured by IMPROVE monitors, an increase over 

the old 1.4. Sea salt is estimated as 1.8 * [chloride] (or chlorine if chloride not available). 

The fs, fL, fss are water growth factors for small (“S”) and large (“L”) fractions of sulfate 

and nitrate, and for sea salt (“SS”). Their values depend on relative humidity, ranging 

from 1 at low humidity to over 5 at 95% humidity. Rayleigh scattering is due to the 

interaction of light with molecules of air itself with no pollutants.

The IMPROVE program revised the IMPROVE equation after a scientific 

assessment of its implications for regional haze planning to reduce biases in light 

extinction estimates compared to the old algorithm9. In particular, when compared to 

nephelometer direct measurements of visibility extinction, the original IMPROVE 

equation over-predicts for low extinction conditions and under-predicts for high 

extinction. These biases have direct relevance for estimates for the worst 20% visibility 

days that are used to assess visibility impact. The new equation shows broader scatter 

overall, but less bias in matching visibility measurements under high and low visibility 

conditions. The split between small and large particles was the main factor in reducing 

the biases. The revised IMPROVE equation has less bias, is more refined, accounts for 

more pollutants and pollutant sizes, incorporates more recent data, and is based on 

considerations of relevance for the calculations needed for assessing progress under the 

Regional Haze Rule.

EPA 2007 guidance10 states that the use of either the IMPROVE or the revised 

IMPROVE equation is acceptable provided that the same algorithm is utilized for both 

the base and future extinction calculations. EPA believes it is appropriate to use the 

revised IMPROVE equation and that this is the preferred method. 

 

9 Revised IMPROVE algorithm for Estimating Light Extinction from Particle Speciation Data, IMPROVE, 

January 2006 (http://vista.cira.colostate.edu/improve/Publications/GrayLit/gray_literature.htm) ; Hand, 

J.L., Douglas, S.G., 2006, Review of the IMPROVE Equation for Estimating Ambient Light Extinction

Coefficients – Final Report 

(http://vista.cira.colostate.edu/improve/Publications/GrayLit/016_IMPROVEEeqReview/IMPROVEeqRevi

ew.htm)

10 Guidance on the Use of Models and Other Analyses for Demonstrating Attainment of Air Quality Goals 

for Ozone, PM2.5, and Regional Haze, EPA-454/B-07-002, April 2007, EPA OAQPS; 

(http://www.epa.gov/ttn/scram/guidance/guide/final-03-pm-rh-guidance.pdf)
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2.2.3 Deciview Impact Calculation

In the second CALPOST step this extinction is converted to deciviews, using the 

defining equation (equation 1) for deciviews. The delta deciviews (Δdv) represents the 

impact on visibility in deciviews of the source being evaluated, and is also provided by 

CALPUFF. It is the change, or “delta”, between deciviews with and without the source. 

Under the BART guidelines, delta deciviews is the difference between deciviews 

including the impact of the source and natural background, and deciviews of the natural 

background alone. Each modeled day and location in the Class I area will have an 

associated delta deciview. For each day, the model finds the maximum visibility impact 

of all locations (receptors) in the Class I area. From among these daily values, the BART 

guidelines recommend use of the 98th percentile, roughly equivalent to the 8th highest 

day, visibility impacts expressed as 24-hour averages of delta deciviews relative to 

natural background, as estimated using the CALPUFF air quality modeling system for 

comparing the base case and the effects of various controls. The 98th percentile is 

recommended rather than the maximum value to avoid undue influence from unusual 

meteorological conditions when CALPUFF is executed according to EPA’s guideline on 

Air Quality Models (40 CFR Part 51 Appendix W).

11

The BART guidelines recommend that impacts of sources be estimated in deciviews 

relative to natural background. The Trinity evaluations used average background 

concentrations (Table 2-3) and relative humidity adjustment factors (Tables 2-4, 2-5, and 

2-6) from the Federal Land Managers’ Air Quality Related Values Work Group (FLAG) 

Phase I Report12 for use with the revised IMPROVE equation (“Method 8”).

Table 2-3. Natural Background Concentrations used for “Method 8”

Class I Area CALPOST control input parameters (μg/m3)

BKSO4 BKNO3 BKOC BKEC BKSOIL BKCM BKSALT

Ammonium 

sulfate

Ammonium 

nitrate

Organic 

carbon

Elemental 

carbon

Soil Coarse 

mass

Sea salt

Caney Creek 0.23 0.10 1.80 0.02 0.50 3.00 0.03

Upper Buffalo 0.23 0.10 1.80 0.02 0.50 3.00 0.03

HerculesGlades0.23 0.10 1.80 0.02 0.50 3.00 0.02

Mingo 0.23 0.10 1.83 0.02 0.51 3.05 0.04

 

11 In our March 12, 2012, final action on the 2010 Arkansas RH SIP revision we noted that the original 

meteorological databases generated by CENRAP and used by Arkansas to conduct its modeling analyses 

did not include observations as EPA guidance recommends. Thus, in its visibility modeling evaluations

Arkansas used the maximum value (i.e. 1

st high value) of modeled visibility impacts instead of the 98th

percentile value (i.e. 8

th high value). The use of the maximum modeled values was agreed to by EPA, 

representatives of the Federal Land Managers, and CENRAP stakeholders.

12 Federal Land Managers’ Air Quality Related Values Work Group (FLAG) Phase I Report—Revised 

(2010) Natural Resource Report NPS/NRPC/NRR—2010/232

(http://www.nature.nps.gov/air/Pubs/pdf/flag/FLAG_2010.pdf)
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Table 2-4. fL(RH) Large RH Adjustment Factors

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

Caney Creek 2.77 2.53 2.37 2.43 2.68 2.71 2.59 2.6 2.71 2.69 2.67 2.79

Upper Buffalo 2.71 2.48 2.31 2.33 2.61 2.64 2.57 2.59 2.71 2.58 2.59 2.72

HerculesGlades2.7 2.48 2.3 2.3 2.57 2.59 2.56 2.6 2.69 2.54 2.57 2.72

Mingo 2.73 2.52 2.34 2.28 2.53 2.6 2.64 2.67 2.71 2.56 2.56 2.73

Table 2-5. fS(RH) Small RH Adjustment Factors

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

Caney Creek 3.85 3.44 3.14 3.24 3.66 3.71 3.49 3.51 3.73 3.72 3.68 3.88

Upper Buffalo 3.73 3.33 3.03 3.07 3.54 3.57 3.43 3.5 3.71 3.51 3.52 3.74

HerculesGlades3.7 3.33 3.01 3.01 3.47 3.48 3.41 3.51 3.67 3.43 3.46 3.73

Mingo 3.74 3.38 3.07 2.97 3.39 3.52 3.57 3.64 3.72 3.47 3.43 3.74

Table 2-6. fSS(RH) Sea Salt RH Adjustment Factors

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

Caney Creek 3.9 3.52 3.31 3.41 3.83 3.88 3.69 3.68 3.82 3.76 3.77 3.93

Upper Buffalo 3.85 3.47 3.23 3.27 3.72 3.78 3.69 3.7 3.84 3.64 3.67 3.86

HerculesGlades3.86 3.51 3.23 3.22 3.66 3.72 3.69 3.73 3.81 3.57 3.65 3.88

Mingo 3.92 3.58 3.3 3.19 3.58 3.72 3.8 3.82 3.85 3.61 3.66 3.9

2.3. CALMET/CALPUFF modeling protocol

Trinity Consultants conducted modeling for each of the facilities of interest 

according to modeling protocols submitted and reviewed by EPA.13 The modeling 

analyses generally followed the BART protocol developed by CENRAP.

14

 However, 

unlike previous modeling conducted for these sources, surface and upper air observations 

were utilized (NO OBS = 0) for the revised source-specific modeling, consistent with 

EPA and FLM recommendations. Trinity Consultants used an existing CALMET data 

set that utilized CALMET v5.53a which is an earlier regulatory version and compatible 

with the regulatory version of CALPUFF (v5.8). In discussions with ADEQ to develop a 

revised BART modeling protocol, EPA identified the availability of this existing 

dataset.15 This data set was generated by Trinity Consultants for use in BART analyses 

 

13 A copy of the final version of each BART analysis performed by Trinity Consultants on behalf of the 

BART sources, upon which our analysis is largely based, can be found in the docket for our proposed 

rulemaking. 

14

 CENRAP BART Modeling Guidelines, T. W. Tesche, D. E. McNally, and G. J. Schewe (Alpine 

Geophysics LLC), December 15, 2005 

(http://www.deq.state.ok.us/aqdnew/RulesAndPlanning/Regional_Haze/SIP/Appendices/index.htm)

15 April 26, 2012 letter from Guy Donaldson, Chief of Air Planning Section at EPA Region 6, to Anthony 

Davis, ADEQ.
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of sources in Oklahoma.16 The modeling protocol for this CALMET data set is available 

in the docket for this action and describes in full the modeling domain and input data 

utilized in developing the meteorological dataset. We note that because this CALMET 

data was prepared using both surface and upper air observations (NO OBS = 0), 

consistent with our guidance, we recommend the use of the 98th percentile or 8th highest 

value in analyzing the visibility benefits anticipated due to the use of controls, rather than 

the maximum value utilized in the previous modeling analysis.

 

Table 2-7 shows selected CALMET settings used in the Trinity evaluation for 

modeling visibility impacts from these facilities. R1MAX and R2MAX represent the 

radius of influence of surface and upper air observations, respectively. R1 (R2) defines 

the distance from an observation at which the surface (upper air) observation and the 

initial wind field are equally weighted and is typically set to half the value of R1MAX

(R2MAX). EPA and FLMs recommend the use of higher values for R1MAX (100 km) 

and R2MAX (200 km) based on tracer evaluations and testing.

17

 EPA is aware of these 

deviations and weighed the potential differences that may occur due to these deviations 

with the additional work and computing resources that would be required to redo the 

analyses. Given the time and resource constraints, EPA concluded that these deviations 

were acceptable and offered to share this dataset with ADEQ and Trinity Consultants for 

the purpose of evaluating visibility benefits due to the use of controls as part of a full 

five-factor BART analysis for subject-to-BART sources in Arkansas. 

 

16 The modeling protocol for this CALMET data set was included as an appendix to each BART analysis 

prepared by Trinity Consultants and can be found as: CALMET DATA Processing Protocol BART 

Determination Oklahoma Gas and Electric, Prepared by Trinity Consultants, January 23, 2008.

17 Memorandum from Tyler Fox (EPA OAQPS) “Clarification on EPA-FLM Recommended Settings for 

CALMET,” August 31, 2009
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Table 2-7. Selected CALMET Settings Used

Option Description EPA default Trinity Consultants

version CALMET version 5.8.4, level 130731 5.53a, level 040716

NOOBS No Observation Mode 0 0

ICLOUD gridded cloud fields 0 0

IWFCOD diagnostic winds 1 1

IFRADJ Froude wind adj. 1 1

IKINE kinematic effects 0 0

IOBR O'Brien vertical wind adj. 0 0

ISLOPE slope flows 1 1

IEXTRP extrapolate wind to upper air -4 -4

ICALM extrapolate calm to upper air 0 0

BIAS layer biases sfc vs. UA NZ*0 NZ*0

IPROG gridded initial prognostic 0 14

RMAX1 max surface radius of influence NA 20

RMAX2 max aloft radius of influence NA 50

RMAX3 max over-water radius of influence. NA 100

RMIN min wind radius of influence. 0.1 0.1

RMIN2 min dist sfc winds extrap 4 4

TERRAD terrain radius of in influence NA 10

R1 weight surface Step 1 vs. obs NA 10

R2 weight aloft Step 1 vs. obs NA 25

ITPROG 3D T from obs or prognostic 0 0

TRADKM radius of influ. for T interp. 500 500

IAVET spatial T averaging 1 1

JWAT1 starting land use for T interp. over water 999 55

JWAT2 ending land use for T interp. over water 999 55

The Trinity evaluation used the regulatory version of CALPUFF (v5.8)18 and 

CALPOST (v6.221). For visibility calculations, the pollution concentration predictions 

of CALPUFF are used in post-processing. First, POSTUTIL considers ammonia 

background concentrations, temperature, and humidity to determine how much nitrate 

ends up as particulate ammonium nitrate; this is to reflect the competition between sulfate 

and nitrate for available ammonia and is referred to as “Nitrate Repartitioning.”

CALPOST then converts the predicted pollutant concentrations into extinction using the 

revised IMPROVE equation followed by converting the estimated total extinction into 

deciviews.

The refined source-specific modeling used a constant value of 3 ppb background 

concentration of ammonia for the domain during the modeling period. Hourly ozone 

observational data provided by ADEQ to Trinity over the 2001-2003 timeframe were 

used to define background ozone concentrations.

 

18 CALPUFF v5.8 was the regulatory version at the time the modeling protocol was developed. On 

December 4, 2013, EPA approved an update to v5.8.4 that contains bug fixes to the previous version. See 

December 3, 2013 CALPUFF Update Memo for a discussion of model changes.
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2.4. EPA Conclusion

We find the modeling protocol to be consistent with EPA and FLM guidance and 

acceptable for the purposes of evaluating the anticipated visibility benefit due to the use 

of controls at the subject-to-BART facilities in Arkansas.