ENSR / AECOM 

I .O Introduction 

I I Objectives 

The Regional Haze Rule regulations require 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 BART-eligible source from the BART requirements based on dispersion modeling by 

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

in a Class I area. This modeling protocol focuses on performing the BART modeling analysis required for 

NO,, SO2, and PMlo. 

Tronox Pigments (Savannah), Inc. (Tronox) has been identified by Georgia Environmental Protection Division 

(GA EPD) as being a source that is eligible for consideration of BART controls for the criteria pollutants 

mentioned above. The purpose of this document is to summarize the procedures by which a modeling 

analysis will be conducted for Tronox emission sources which have been designated as BART-eligible. The 

modeling procedures outlined will be used to determine whether the source is subject to BART requirements 

(exemption modeling). If it is determined that the source is subject to BART, then the procedure will be 

appropriately used to evaluate the visibility impacts factor in the BART determination step (determination 

modeling). The modeling procedures are consistent with those outlined in the updated final Visibility 

Improvement State and Tribal Association of the Southeast (VISTAS) common BART modeling protocol. This 

protocol references relevant portions of the common VISTAS protocol. The protocol, updated March 9, 2006, 

is available at htt~://www.vistas-sesarm.orq/BART/BARTMoelinqProtocol rev2 9Mar2006.rsdf. 

1.2 Location of source vs. relevant Class I Areas 

Figure 1-1 shows a plot of the Tronox Facility relative to nearby Class I Areas. There are three Class I areas 

within 300 km of the facility: Cape Romain, Wolf Island and Okefenokee Wilderness Areas. The BART 

exemption modeling will be conciucied 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, BART determination modeling will be performed for those Class I areas 

where the exemption modeling shows a greater than 0.5 deciviews (dv) impact. 

1.3 Organization of protocol document 

Section 2 of this protocol describes the source information 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 modeling 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 references cited are also included in the VISTAS common BART modeling protocol, no 

additional references section is required in this document. Appendix A is reserved for additional information, if 

necessary at a later date, on BART control option emissions data. 

BART Modeling Protocol: Tronox 

April 2033 
Mao Location Location of Class I Areas near Facility Site 

0 25 50 100 

iiles Prepared ByAmy Uebele 

Reviewed @:Thomas Pritche 

Figure 1-1 

Date: April 2006 
2.0 Source Description 

2.1 Unit-specific source information 

The emission sources used to assess the visibility impacts at the Class I areas within 300 km of Tronox is 

discussed in this section. The VISTAS protocol allows for the use of source-specific emissions and speciation 

factors. Otherwise, default values from AP-42 can be used as the default. 

Based on the letter dated March 9, 2006, by Ms. Elisabeth Munsey, Tronox Facility cannot be exempted from 

BART determination requirements as according to the plant emissions and distance criteria. Specifically, the 

following sources have been identified as BART Eligible Sources: 

Chloride Finishing A 

Sulfuric Acid Plant 

The unit-specific emission rates and emission factors are under review and will be submitted to GA EPD under 

separate cover. In addition, Tronox is also considering additional emission limits that could exempt the sources 

based on emission levels and distance to Class I Areas. 

If the BART exemption modeling indicates that a BART determination is required, then one or more control 

options will be considered for the modeling to determine visibility improvement from the baseline case. 

Appendix A has been reserved for future use as an update to this protocol in the event that a BART 

determination is required for Tronox. Appendix A would provide plant-specific data for each control option 

considered to be operationally feasible, and would discuss any deviations from the default criteria pollutant 

speciation guidance that is appropriate for the controls implemented in each candidate BART option. 

In practice, CALPUFF allows for the user to input certain components of PMlo as separate species and 

separate sizes, which will result in more accurate wet and dry deposition velocity results and also more 

accurate effects on light scattering. Appropriate particle size distribution information will be used for the BART 

exemption modeling as well as the BART determination modeling, if needed. 

The proposed modeling approach is based on the best understanding of the guidance and technical 

considerations known at this time. If additional issues arise during the course of the analysis that requires 

clarification, Tronox will contact GA EPD for further guidance or to request approval for adjustments to this 

proposed approach. 

BART Modeling Protocol: Tronox 

April 2006 
3.0 Input data to the CALPUFF model 

3.1 General modeling procedures: 

VISTAS has developed five sub-regional 4-km CALMET meteorological databases for three years (2001- 

2003). 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. The BART modeling 

for Tronox will be completed using the appropriate 4-km sub-domain. 

USGS 90-meter Digital Elevation Model (DEM) files were used by VISTAS to generate the terrain data at 4-km 

resolution for input to the 4-km sub-regional 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 sub-regional 

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 the modeling for Tronox will use the 4-km sub-domain. However, if the results indicate that 

peak concentrations could be better predicted with a CALPUFF run using a finer grid, due to terrain, shoreline 

resolution, or other factors, then refinements in the modeling procedures will be considered and GA EPD 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 that were used for the 4-km sub-regional 

CALMET simulations would be used for this modeling run. The extent of the modeling domain may need to be 

changed because of disk space restrictions. 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 settinglfiles (specifically 

the GEO.DAT file) will be modified. A summary of these modifications would be provided to GA EPD for 

review and approval. 

3.2 Air quality database (background ozone and ammonia) 

Hourly measurements of ozone from non-urban monitors, as generated by VISTAS and available on the 

VISTAS CALPUFF page on the Earth Tech web site (htt~:l/www.src.com/verio/downloadlsam~le files.htm), 

will be used as input to CALPUFF. As for ammonia, it is intended to follow the approach recommended by 

VISTAS. Currently, VISTAS intends to provide hourly ammonia data, derived from CMAQ runs, for the 4-km 

sub-regional domain runs. If for some reason the CMAQ data are unavailable, then it is anticipated that 

VISTAS will recommend an alternate approach for sources to use. Two alternatives that could be considered 

are to use average, single-value ammonia background concentrations derived from existing references such 

as the 1998 IWAQM Phase 2 report (see page 14 of that report) or to use monthly-varying ammonia 

background values. 

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

There are three Class I areas within 300 km of Tronox (as noted in Figure 1-1). For each of the Class I areas, 

natural background conditions must be established in order to determine a change in natural conditions related 

BART Modeling Protocol: Tronox 3-1 April 2006 
to a source's emissions. For the modeling described by this protocol document, it is intended to use the 

natural background light extinction corresponding to the 20% best days (EPA 2003 values), consistent with the 

VISTAS BART protocol. However, the BART rule has an inconsistency on whether the natural background 

should be reflective of the average conditions rather than the 20% best days' conditions. If EPA determines 

that the average conditions are appropriate and GA EPD adopts this position, then the CALPUFF exemption 

modeling will use the average background conditions for the 0.5 deciview test of contributing to visibility 

impairment. 

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

equation: 

Extinction (Mm-I) = 10 exp(deciviews/l0). 

For example, the EPA guidance document indicates for Cape Romain Wilderness Area that the deciview value 

for the best 20% of days is 3.68. This is equivalent to an extinction of 14.44 inverse megameters (Mm-'). In 

the case of average conditions, the deciview value is 7.52, which is equivalent to an extinction of 21.21 Mm-I. 

This extinction includes the default 10 Mm-I 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 Cape Romain would be the total natural background extinction minus 10 (expressed 

in ~m-'), or 4.44, for the 20% best days case. This is most easily input as fine soil concentrations (4.44 Clg/m3) 

in CALPOST, since the extinction efficiency of soil (PM-fine) is 1.0 and there is no f(RH) component. The 

concentration entries for all other particle constituents would be set to zero, and the fine soil concentration 

would be kept the same for each month of the year. The monthly values for f(RH) that CALPOST needs will 

be taken from "Guidance for Tracking Progress Under the Regional Haze Rule" (EPA, 2003) Appendix A, 

Table A-3. However, it should be noted that these values correspond to the annual average background 

conditions, not the 20% best conditions, which would intuitively be expected to be associated with drier days 

than average. Therefore, Tronox reserves the right to adjust the f(RH) values for the 20% best days' humidity 

conditions if this refinement is needed. 

BART Modeling Protocol: Tronox 

April 2006 
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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 Tronox. 

4.1 Model selection and features 

As noted in the VISTAS protocol, VISTAS will use the BART-specific versions of CALMET and CALPUFF that 

have been posted at htt~://www.src.com/verio/download/download.htm#VISTAS VERSION. These versions 

contain enhancements funded by the Minerals Management Service (MMS) and VISTAS. They were 

developed by Earth Tech, Inc. and 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 protocol. 

4.2 Modeling domain and receptors 

The initial Tronox BART runs will use the sub-domain 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 the 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 of the Class I areas are based on the NPS database of Class I receptors, as 

recommended by VISTAS. 

4.3 Technical options used in the modeling 

CALMET modeling for the VISTAS-provided 4-km sub-domains will be pre-determined by the VISTAS 

contractor, and, therefore, it is assumed that VISTAS approves of the manner in which CALMET has been run 

for the sub-domain data that they provide. 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 used in the CALMET run, in order 

to allow for state agency review and approval. 

For CALPUFF model options, Tronox will follow the VISTAS common BART modeling protocol, which states 

that IWAQM (EPA, 1998) guidance should be used. The VISTAS protocol also notes that building downwash 

effects are not required to be included unless the state directs the source to include these effects. Since 

Tronox is several tens of kilometers from the nearest Class I area, building downwash effects in the CALPUFF 

modeling will not be included. 

The POSTUTIL utility program will be used to repartition HN03 and NO3 using VISTAS-provided ammonia 

concentrations derived from previous 2002 CMAQ modeling conducted by EPA, or an 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 criteria pollutants' concentrations on light extinction. 

The formula that is used is the existing (not the November 2005 revised) IMPROVEIEPA formula, which is 

BART Modeling Protocol: Tronox 4-1 April 2006 
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applied to determine a change in light extinction due to increases in the particulate matter component 

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

be, = 3 f(RH) [(NH4)2S04] + 3 f(RH) [NH4N03] + 4[OC] + 1 [Soil] + O.G[Coarse Mass] + 10[EC] + bRay 

The concentrations, in square brackets, are in units of micrograms per cubic meter @g/rn3) and be, is in units 

of ~m-I. The Rayleigh scattering term (bRay) has a default value of 10 ~m-', as recommended in EPA 

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

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. For near sea-level sites, this value is generally between 11 and 12 

~m-'. Specific values can be found at: 

The assessment of visibility impacts at the Class I areas will use CALPOST Method 6. Each hour's sourcecaused extinction is calculated by first using the hygroscopic components of the source-caused 

concentrations, due to ammonium sulfate and nitrate, and monthly Class I area-specific f(RH) values. The 

contribution to the total source-caused extinction from ammonium sulfate and nitrate is then added to the 

other, non-hygroscopic components of the particulate concentration (from coarse and fine soil, secondary 

organic aerosols, and from elemental carbon) to yield the total hourly source-caused extinction. 

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

protocol indicates that with the use of the 4-km sub-regional 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. As an added check, the 22nd highest 

prediction over the three years modeled should also not exceed 0.5 deciviews for a source to be exempted 

from a BART determination. 

Figure 4-1 of the VISTAS common BART modeling protocol presents a flow chart showing the components of 

that modeling protocol for the analysis to determine whether a source is subject to BART. Again, it should be 

noted that the modeling for Tronox will focus on Sub-Regional Fine-Scale modeling as depicted in the lower 

half of the figure. 

If the exemption modeling demonstrates that the BART-eligible units at Tronox do not cause or contribute to 

visibility impairment, then Tronox will not be subject to BART requirements, and no further analysis is needed. 

Otherwise, Tronox will proceed to perform BART determination modeling for the baseline and each control 

option in a similar manner as has been described in this document. 

BART Modeling Protocol: Tronox 

April 2006 
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Appendix A (Reserved) 

Source-Specific Emissions Data for BART Determination Options 

BART Modeling Protocol: Tronox April 2006