BART Modeling Protocol: DSM Chemicals North 

America, Inc. 

Prepared by: Roy Dean Morris II 

for DSM Chemicals North America, Inc. 

May 12, 2006 
Table of Contents 

1.0 Introduction 

1.1 Objectives 

1.2 Location of sources vs. relevant Class I areas 

1.3 Organization of protocol document 

2.0 Source description and emissions data 

2.1 Unit specific source data 

3.0 Input data for the CALPUFF model 

3.1 General modeling procedures 

3.2 Air quality database (background ozone and ammonia) 

3.3 Natural conditions and monthly f(RH) at Class I Areas 

4.0 Air quality modeling procedures 

4.1 Model selection and features 

4.2 Modeling domain and receptors 

4.3 Technical options used in the modeling 

4.4 Light extinction and haze impact calculations 

5.0 Presentation of modeling results 
1.0 Introduction

1.1 Objectives 

The Regional Haze Rule requires Best Available Retrofit Technology (BART) for any 

BART-eligible source that “emits any air pollutant which may reasonably be anticipated 

to cause or contribute to any impairment of visibility” in any mandatory Class I Federal 

area. Pursuant to federal regulations, states have the option of exempting a BARTeligible source from BART requirements based on dispersion modeling demonstrating 

that the source cannot reasonably be anticipated to cause or contribute to visibility 

impairment in a Class I Federal area. 

There are numerous sources on the DSM Chemicals North America, Inc. (DCNA) site, 

located in Augusta, Georgia, which is owned and operated by DSM Chemicals, which 

have been identified as BART-eligible sources. The purpose of the document is to 

summarize the procedures by which modeling analysis will be conducted for these 

sources. The modeling procedures outlined will be used to determine whether the 

sources are subject to BART requirements (exemption modeling). If it is determined that 

the sources are subject to BART, then the procedures will be used to evaluate the 

visibility improvement factor in the BART determination step (determination modeling). 

The modeling procedures are consistent with those outlined in the updated final VISTAS 

common BART modeling protocol (dated December 22, 2005, revision 2 – 3/9/06), 

available at http://www.vistassesarm.org/BART/BARTModelingProtocol_rev2_9Mar2006.pdf. This source specific 

BART modeling protocol references relevant portions of the common VISTAS modeling 

protocol. DCNA has chosen to use the free VISTAS 12-km modeling as its initial model 

to exempt the BART regulations. If DCNA fails to meet the BART requirements using the 

free VISTAS 12-km modeling, then DCNA will use the refined 4-km determination 

modeling to exempt the BART requirements. 

1.2 Location of sources vs. relevant Class I areas 

The Georgia Environmental Protection Agency (EPD), which is in charge of the state’s 

BART program, has determined that sources in the DCNA plant site are BART-eligible. 

Figure 1-1 shows a plot plan of the DCNA plant site relative to nearby Class I areas. 

There are eight Class I areas within 300 km (1) of the DCNA plant site: 

1. Cape Romain Wilderness (SC) – 219.2 km 

2. Shining Rock Wilderness Area (NC) – 227.6 km 

3. Wolf Island Wilderness Area (GA) – 236.9 km 

4. Great Smokey Mountains national Park (NC) – 259.7 km 

5. Okefenokee Wilderness Area (GA) – 266.0 km 

6. Linville Gorge Wilderness Area (NC) – 266.7 km 

7. Joyce Kilmer-Slickrock Wilderness Area (TN) – 281.5 km 

8. Cohotta Wilderness Area (GA) – 288.7 km 

(1) Distances of Class I areas to DCNA plant site obtained from Pete Courtney, EPD 

Air Protection Branch on 5/4/06 

The BART exemption modeling will be conducted for each of these Class I areas in 

accordance with the referenced VISTAS common BART modeling protocol and the 
procedures described in this source specific BART modeling protocol. If necessary, 

visibility improvement modeling for the BART determination step will be performed for 

those Class I areas where the exemption modeling shows a greater than 0.5 deciview 

(dv) impact. 

Section 2 of this protocol describes the source emissions that will be used as input to the 

BART exemption modeling and, if necessary, the BART determination modeling. Section 

3 describes the input data to be used for the modeling including the domain, terrain and 

land use, and meteorological data. Section 4 describes the air quality modeling 

procedures and Section 5 discusses the presentation of modeling results. Since all of 

the reference sites are also included in the VISTAS common BART modeling protocol 

(Section 7.), no additional reference section is included in the document other than the in 

Section 1.2. (distance of Class I areas to the DCNA site). 

Figure 1-1 Location of Class I Areas in relation to the DCNA site 
2.0 Source Description and Emissions Data

2.1` Unit-specific source data 

The emissions data used to assess the visibility impacts at the Class I areas within 300 

km of the DCNA plant site is discussed in this section. VISTAS states intend to follow 

Option C, which is to determine if the visibility impact from individual sources exceeds a 

contribution threshold for SO2, NOx and PM emissions (VISTAS common BART protocol 

Section 4.1). 

To determine if a source is BART eligible, VISTAS plans to use Q/d as a presumptive 

indicator that a source is subject to BART. Based on actual 2002 SO2 emissions 

provided to the Georgia EPD Air Protection Branch, the Q/d value for the DCNA site is 

0.17 (which is less than 10). As indicated in a letter dated March 9, 2006 from the 

Georgia EPD Air Protection Branch, the DCNA site has been offered the opportunity to 

use the free VISTAS 12-km initial modeling to determine (a) if a particular source may be 

exempted from further BART analyses and (b) if a finer 4-km grid CALPUFF analysis 

should be undertaken. If the DCNA site does not exempt out from further BART 

requirements using the 12-km grid initial modeling then the finer grid CALPUFF 

modeling analysis using subregional CALMET domain will be the definitive test as to 

whether a source is subject to BART. The baseline data for BART eligible sources has 

been sent via email to the Georgia EPD Air Protection Branch which list all of the 

sources, UTM coordinates, stack heights, diameter, exit gas velocity and temperature, 

and emissions data from 2002 on VOC, SO2, NOx, NH3, and PM. 
3.0 Input Data to the CALPUFF Model 

3.1 General modeling procedures 

VISTAS has developed five subregional 4-km CALMET meteorological databases for 

three years (2001-2003) (VISTAS common protocol Section 4.2). The sub-regional 

modeling domains are strategically designed to cover all potential BART eligible sources 

within VISTAS states and all PSD Class I areas within 300 km of those sources (to the 

nearest edge). The extents of the 4-km subregional domains are shown in Figure 4-4 of 

the VISTAS common BART modeling protocol. The BART modeling for the DCNA site 

will be done using the 4-km subdomain _________ (subdomain name to be added later). 

USGS 90-meter Digital Elevation Model (DEM) files were used by VISTAS to generate 

the terrain data at 4-km resolution fore input to the 4-km subregional CALMET run. 

Likewise, USGS 90-meter Composite Theme Grid (CTG) files were used by VISTAS to 

generate the land use data at 4-km resolution for input to the 4-km subregional CALMET 

run. 

Three years of MM5 data (2001-2003) were used by VISTAS to generate the 4-km 

subregional meteorological datasets. See Sections 4.3.2 and 4.4.2 in the VISTAS 

common BART modeling protocol for more detail on these issues. 

It is intended that all of the modeling at the DCNA site will use 4-km subdomain 

___________ (subdomain name to be added later). However, if the results indicate that 

the modeling could be improved with a CALPUFF run using a finer grid, then 

refinements in the modeling procedures will be considered and the Georgia EPD Air 

Protection Branch will be asked to approve these refinements. 

In the event that a finer grid resolution is used, CALMET must be rerun. Other 

modifications to inputs of CALMET would include the extent of the modeling domain, the 

resolution of the terrain and land use data, and other relevant settings. The same MM5 

data and observations as used for the 4-km subregional CALMET simulations would be 

used. The size of the CALMET output is directly proportional to the grid resolution of the 

run. The domain would be limited to the source and the exclusive Class I area(s) being 

assessed with a higher grid resolution, including a 50-km buffer in all directions. 

If CALMET needs to be run at even a finer grid resolution, then the appropriate model 

settings/files (specifically the GEO.DAT file) will be modified. A summary of the se 

modifications would be provided to the Georgia EPD Air Protection Branch for review 

and approval. 

3.2 Air quality database (background ozone and ammonia 

Hourly measurements of ozone from all non-urban monitors, as generated by VISTAS 

and available on the VISTAS CALPUFF page on the Earth Tech web site 

(http://www.src.com/verio/download/sample_files.htm), will be used as input to 

CALPUFF. For ammonia, the approach recommended by VISTAS will be followed. 

3.3 Natural conditions and monthly f(RH) at Class I Areas 
For each of the applicable Class I areas, natural background conditions must be 

established in order to determine a change in natural conditions related to a source’s 

emissions. The modeling described by this protocol document intends to use annual 

average natural background light extinction (EPA 2003 values). To determine the input 

to CALPUFF, it is first necessary to convert the deciviews to extinction using the 

equation: 

Extinction (Mm1) = 10 exp (deciviews/10) 

For example, the EPA guidance document indicates for Great Smokey Mountains 

National Park that the deciview value for the average of the days is 7.60. This is 

equivalent to an extinction of 21.38 inverse megameters (Mm-1). 

This extinction includes the default 10 Mm-1 for Rayleigh scattering. The remaining 

extinction is due to naturally occurring particles, and should be held constant for the 

entire year’s simulation. Therefore, the data provided to CALPOST for Great Smokey 

Mountains National Park would be the total natural background extinction minus 10 

(expressed in Mm-1), or 11.38. 

4.0 Air Quality Modeling Procedures 

This section provides a summary of the modeling procedures outlined in the 

VISTAS protocol that will be used for the refined CALPUFF analysis to be 

conducted for the DCNA site. 

4.1 Model selection and features 

As noted in the VISTAS protocol (Summary, Recommendations Section II.), VISTAS will 

use CALPUFF Version 5.754 and CALMET Version 5.7, which can be obtained at 

http://www.src.com/verio/download/download.htm#VISTAS_VERSION. These versions 

contain enhancements funded by the Mineral Management Service (MMS) and VISTAS. 

They were developed by Earth Tech, Inc. and they are maintained on Earth Tech’s 

Atmospheric Studies Group CALPUFF website for public access. This release includes 

CALMET, CALPUFF, CALPOST, CALSUM, and POSTUTIL as well as CALVIEW. 

The major features of the CALPUFF modeling system, including those of CALMET and 

the post processors (CALPOST and POSTUTIL), are referenced in Section 3 of the 

VISTAS common BART protocol. 

4.2 Modeling domain and receptors 

The initial DCNA site BART runs will use the sub-domain _________________ 

(subdomain name to be added later), 4-km CALMET data to be supplied by VISTAS, as 

discussed above. This domain includes all Class I areas within 300 km of the source, 

plus a 50-km buffer. If there is a need for a refined analysis with a finer grid, a 

supplement to this modeling protocol will be provided describing the proposed 

procedures. 

The receptors used for each Class I areas are based on the NPS database of Class I 

receptors, as recommended by the VISTAS common BART protocol (Section 4.3.3). 
4.3 Technical options used in the modeling 

CALMET modeling for the VISTAS-provided 4-km subdomains will be performed per the 

procedures specified in the VISTAS common BART modeling protocol. If it is decided to 

conduct additional modeling with a finer grid than 4-km, this modeling protocol will be 

updated to specify the technical options to be used in the CALMET run, in order to allow 

state agency review and approval. 

For CALPUFF model options, DCNA will follow the VISTAS common BART modeling 

protocol (Section 4.4.1), which states that we should use IWAQM (EPA, 1998) guidance. 

The VISTAS protocol (Section 4.3.3) also notes that building downwash effects are not 

required to be included unless the state directs the source to include those effects. Since 

the DCNA site is tens of kilometers from the nearest Class I area, building downwash 

effects will not be include in the CALPUFF modeling. 

The POSTUTIL utility program (VISTAS common BART protocol Section 4.4.2) will be 

used to repartition HNO3 and NO3 using VISTAS-provided ammonia concentrations 

derived from previous 2002 CMAQ modeling conducted by EPA or the alternate 

ammonia concentrations approach recommended by VISTAS, if the CMAQ data is 

unavailable. 

4.4 Light extinction and haze impact calculations 

The CALPOST postprocessor will be used as prescribed in the VISTAS protocol for the 

calculation of the impact from the modeled source’s primary and secondary particulate 

matter concentrations on light extinction. The formula use is the existing (not the 

November 2005 revised) IMPROVE/EPA formula, which is applied to determine the 

change in light extinction due to increases in the particulate matter component 

concentrations. Using the notation of CALPOST, the formula is the following: 

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

10[EC] + bRay 

The concentration, in square brackets, are in ug/m3 and bext is in units of Mm-1. The 

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

guidance for tracking reasonable progress (EPA, 2003a). However, as recommended in 

the VISTAS protocol (Section 6.2.4), for refined 4-km grid (or smaller) CALPUFF runs, 

the Rayleigh scattering term will be modified for the specific elevation of the Class I area 

receptors. The Rayleigh term for estimating natural background will also be adjusted to 

be consistent with this approach. 

The BART rule significance threshold for the contribution to visibility impairment is 0.5 

deciviews. The VISTAS protocol (Section 4.3.2) indicates that with the use of the 4-km 

subregional CALMET database, a source does not cause or contribute to visibility 

impairment if the 98th percentile (or 8th highest) day’s change in extinction from natural 

conditions does not exceed 0.5 deciviews for any of the modeled years (an added check 

is: the 22nd highest prediction over the three years modeled should nopt exceed 0.5 

deciviews for a source to be exempted from a BART determination). 

The haze index (HI) is calculated from the extinction coefficient via the following formula: 
HI = 10 ln (bext/10) 

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

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

of the source and without the impact of the source.

If the exemption modeling demonstrates that the DCNA site does not cause or contribute 

to visibility impairment, then the source will not be subject to BART requirements, and no 

further analysis is needed. Otherwise, the DCNA will proceed to perform BART 

determination modeling for the baseline each control option in a similar manner as has 

been described in this document. 

5.0 Presentation of Modeling Results 

The BART exemption and, if necessary, the BART determination modeling results for 

the DCNA site will be provided to the state agency in a manner as described in the 

VISTAS protocol (Section 4.5). A report will be produced that includes the following 

elements (as suggested in the VISTAS protocol): 

• A map of the source location and Class I areas within 300 km of the source. 

• For the CALPUFF modeling domain, a table listing all Class I areas in the 

VISTAS domain and those in neighboring states and impacts from the BART 4-

km grid exemption modeling at those Class I areas within 300 km of the source, 

as illustrated in Table 4.3 of the VISTAS protocol.

• A discussion of the number of Class I areas with visibility impairment due to 

source emissions for the 98th percentile days each year (and the 98th percentile 

over all three years modeled) greater than 0.5dv. 

• For the Class I area with the maximum impact, a discussion of the number of 

days beyond those excluded (e.g., the 98th percentile for refined analyses) that 

the impact of the source exceeds 0.5 dv, the number of receptors in the Class I 

area where the impact exceeds 0.5 dv, and the maximum impact. 

• For any finer grid CALPUFF exemption modeling, results for those Class I areas 

for which impacts of the source exceeded 0.5 dv in the 4-km initial modeling. We 

would report the same type of results as provided for 4-km exemption modeling. 

• For control option modeling, each control option tested will be listed in tabular 

format. For each control option and for each Class I area where the impact of the 

source exceeded 0.5 dv, a report in the change in pollutant emissions and the 

change in visibility impact from the source as a result of the control option. The 

effectiveness of candidate control options are to be compared to each other, not 

to a specific target improvement.