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# Introduction

II Objectives The Regional Haze Rule regulations require Best Available RetrofitTechnology (BART) for any BART-eligible source that "emits any air pollutant which may reasonably be anticipated to cause or contribute to any impairmentof visibility" in any mandatory Class I federalarea. Pursuantto federal regulations, states havethe 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 EnvironmentalProtection 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 ImprovementState and TribalAssociation of the Southeast (VISTAS) common BART modeling protocol. This protocol references relevant portionsof the common VISTAS protocol. The protocol, updated March 

### 9, 2006, isavailableat htt~://www.vistas-sesarm.orq/BART/BARTMoelinqProtocol 

### rev2 9Mar2006.rsdf. 

### 1.2 Locationof source

## vs. relevantClass IAreas Figure 1-1 

### shows a 

### plot of the Tronox Facility relativeto 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 wherethe exemption modelingshows 

### a greater than 0.5 deciviews (dv) impact. 

### 1.3 Organizationof protocoldocument Section 2 of this protocoldescribes the source information that will be used as input to the BART exemption modelingand, 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 necessaryat a laterdate, on BARTcontrol option emissions data.

BART Modeling Protocol:Tronox April 2033Mao Location Locationof Class IAreas 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 protocolallowsfor the use of source-specific emissionsand speciation factors. Otherwise,defaultvalues fromAP-42 can be used asthe default. Based on the letter dated March 9, 2006, by Ms. ElisabethMunsey, Tronox Facility cannot be exempted from BART determination requirements as according to the plant emissions and distance criteria. Specifically, the following sources have been identifiedas BART Eligible Sources: Chloride FinishingA SulfuricAcid Plant
The unit-specificemission rates and emissionfactors are under review and will be submitted to GA EPD under separate cover. In addition,Tronox is also considering additionalemission limitsthat could exempt the sources basedon emission levels and distanceto 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 BARToption. 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 modelingas well as the BARTdetermination 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 Iareas within 300 kmof those sources. The BART modeling for Tronox will be completed using the appropriate 4-km sub-domain. USGS 90-meter Digital ElevationModel (DEM)files were used by VISTAS to generate the terrain data at4-km resolutionfor inputto the 4-km sub-regional CALMET run. Likewise, USGS 90-meter CompositeTheme Grid (CTG) files were used by VISTAS to generate the land use data at 4-km resolution for input to the 4-km subregionalCALMET 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 modelingfor Tronox will use the 4-km sub-domain. However, if the results indicate that peak concentrations could be better predictedwith 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 simulationswould be used for this modeling run. The extent of the modeling domain may needto be changed because of disk space restrictions. The size of the CALMET output is directly proportionalto the grid resolution of the run. The domain would be limited to the source and the exclusive Class I area(s) being assessedwith a higher grid resolution,includinga 50-km buffer in all directions. If CALMET needs to be run at even a finer grid resolution, then the appropriate modelsettinglfiles (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 intendsto 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 alternateapproachfor sources to use. Two alternativesthat 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) atClass I Areas There are three Class Iareas within 300 kmof Tronox (as noted in Figure 1-1). For each of the Class I areas, naturalbackgroundconditions must be established in order to determine a change in naturalconditions related

BART ModelingProtocol: Tronox 3-1 April 2006

### to a source's emissions. For the modeling described by this protocol document, it is intended to use the naturalbackground light extinction corresponding to the 20% bestdays (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)

### = 10exp(deciviews/l0). For example, the EPAguidancedocument indicates for Cape RomainWilderness Area that the deciviewvalue 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 equivalentto 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 Romainwould bethe total natural background extinction minus 10(expressed in ~m-'), or 4.44,

### for the 20% best days case. This is mosteasily inputas 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 needswill 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 rightto 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 analysisto be conductedfor Tronox.


### 4.1 Modelselectionand features As noted in theVISTAS protocol,VISTAS will use the BART-specific versions of CALMETand CALPUFFthat 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 (CALPOSTand POSTUTIL) are referenced in Section3 of the VISTAS protocol.


### 4.2 Modelingdomain 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 byVISTAS.


### 4.3 

### Technical options used inthe modeling CALMET modeling for the VISTAS-provided 4-km sub-domains will be pre-determined by the VISTAS contractor, and, therefore, it is assumedthat VISTAS approves of the manner inwhich CALMET has been run for the sub-domain data that they provide. If it is decided to conduct additional modelingwith a finer grid than 4-km, this modeling protocol will be updated to specify the technicaloptions used in the CALMET run, in order to allow for state agency reviewand 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 buildingdownwash 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, buildingdownwasheffects in the CALPUFF modelingwill not be included. The POSTUTIL utility program will be used to repartition HN03and 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 extinctionand haze impactcalculations The CALPOST postprocessorwill 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. Usingthe notationof CALPOST,the formula is thefollowing: 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 recommendedin the VISTAS protocol, for refined4-km grid (orsmaller) CALPUFF runs, the Rayleighscattering term will be modifiedfor 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 befound 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 elementalcarbon)to yield the total hourly source-causedextinction. The BART rule significance thresholdfor the contributionto visibility impairment is 0.5 deciviews. TheVISTAS protocol indicatesthat 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 conditionsdoes not exceed 0.5 deciviewsfor any of the modeledyears. 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. Figure4-1 

### of the VISTAS common BART modeling protocol presents a flow chart showing the components of that modeling protocol for the analysis to determinewhether 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 thefigure. If the exemption modeling demonstrates that the BART-eligibleunits at Tronox do not cause or contributeto 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 manneras has beendescribed 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