# BART Modeling Protocol: DSM Chemicals North

America, Inc.

Prepared by: Roy Dean Morris II for DSM Chemicals North America, Inc.



## May 12, 2006Table 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 ammo nia)

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 results1.0 

### Introduction

1.1 Objectives

The Regional Haze Rule requires Best Available Retr ofit 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 visibil ity” 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 dis persion 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 Nor th America, Inc. (DCNA) site, located in Augusta, Georgia, which is owned and ope rated 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 u sed 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 procedure s will be used to evaluate the visibility improvement factor in the BART determina tion step (determination modeling). The modeling procedures are consistent with those o utlined in the updated final VISTAS common BART modeling protocol (dated December 22, 2 005, 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 me et 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 DC NA 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) – 2 81.5 km 8. Cohotta Wilderness Area (GA) – 288.7 km

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

Air Protection Branch on 5/4/06

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

accordance with the referenced VISTAS common BART m odeling protocol and theprocedures described in this source specific BART m odeling protocol. If necessary,

visibility improvement modeling for the BART determ ination step will be performed for those Class I areas where the exemption modeling sh ows a greater than 0.5 deciview (dv) impact.

Section 2 of this protocol describes the source emi ssions 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 model ing including the domain, terrain and land use, and meteorological data. Section 4 descri bes 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 in cluded 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 t o the DCNA site2.0 

### Source Description and Emissions Data

2.1` Unit-specific source data

The emissions data used to assess the visibility im pacts at the Class I areas within 300 km of the DCNA plant site is discussed in this sect ion. VISTAS states intend to follow Option C, which is to determine if the visibility i mpact from individual sources exceeds a

contribution threshold for SO 2 , NO

x and PM emissions (VISTAS common BART protocol Section 4.1).

To determine if a source is BART eligible, VISTAS p lans to use Q/d as a presumptive indicator that a source is subject to BART. Based o n 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 let ter dated March 9, 2006 from the Georgia EPD Air Protection Branch, the DCNA site ha s been offered the opportunity to use the free VISTAS 12-km initial modeling to deter mine (a) if a particular source may be exempted from further BART analyses and (b) if a fi ner 4-km grid CALPUFF analysis

should be undertaken. If the DCNA site does not ex empt out from further BART requirements using the 12-km grid initial modeling then the finer grid CALPUFF modeling analysis using subregional CALMET domain w ill be the definitive test as to whether a source is subject to BART. The baseline d ata for BART eligible sources has been sent via email to the Georgia EPD Air Protecti on Branch which list all of the sources, UTM coordinates, stack heights, diameter, exit gas velocity and temperature, and emissions data from 2002 on VOC, SO 2 , NO

x , NH3, and PM.

### 3.0 Input Data to the CALPUFF Model

3.1 General modeling procedures

VISTAS has developed five subregional 4-km CALMET m eteorological databases for three years (2001-2003) (VISTAS common protocol Sec tion 4.2). The sub-regional modeling domains are strategically designed to cove r all potential BART eligible sources

within VISTAS states and all PSD Class I areas with in 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 _________ (su bdomain name to be added later).

USGS 90-meter Digital Elevation Model (DEM) files w ere used by VISTAS to generate the terrain data at 4-km resolution fore input to t he 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 i nput to the 4-km subregional CALMET

run.

Three years of MM5 data (2001-2003) were used by VI STAS 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 th ese issues.

It is intended that all of the modeling at the DCNA site will use 4-km subdomain ___________ (subdomain name to be added later). How ever, if the results indicate that the modeling could be improved with a CALPUFF run u sing a finer grid, then refinements in the modeling procedures will be cons idered and the Georgia EPD Air Protection Branch will be asked to approve these re finements.

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 ot her relevant settings. The same MM5 data and observations as used for the 4-km subregio nal CALMET simulations would be used. The size of the CALMET output is directly pro portional 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 reso lution, 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 ammo nia

Hourly measurements of ozone from all non-urban mon itors, as generated by VISTAS and available on the VISTAS CALPUFF page on the Ear th 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 V ISTAS will be followed.

3.3 Natural conditions and monthly f(RH) at Class I AreasFor each of the applicable Class I areas, natural b ackground conditions must be

established in order to determine a change in natur al conditions related to a source’s emissions. The modeling described by this protocol document intends to use annual average natural background light extinction (EPA 20 03 values). To determine the input to CALPUFF, it is first necessary to convert the de civiews to extinction using the equation:

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

For example, the EPA guidance document indicates fo r Great Smokey Mountains

National Park that the deciview value for the avera ge of the days is 7.60. This is equivalent to an extinction of 21.38 inverse megame ters (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 provi ded 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 pro cedures outlined in the VISTAS protocol that will be used for the refined C ALPUFF analysis to be

conducted for the DCNA site.

4.1 Model selection and features

As noted in the VISTAS protocol (Summary, Recommend ations Section II.), VISTAS will use CALPUFF Version 5.754 and CALMET Version 5.7, w hich can be obtained at http://www.src.com/verio/download/download.htm#VIST AS_VERSION . These versions contain enhancements funded by the Mineral Manageme nt Service (MMS) and VISTAS. They were developed by Earth Tech, Inc. and they ar e maintained on Earth Tech’s Atmospheric Studies Group CALPUFF website for publi c access. This release includes CALMET, CALPUFF, CALPOST, CALSUM, and POSTUTIL as w ell as CALVIEW.

The major features of the CALPUFF modeling system, including those of CALMET and the post processors (CALPOST and POSTUTIL), are ref erenced 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-do main _________________ (subdomain name to be added later), 4-km CALMET dat a to be supplied by VISTAS, as

discussed above. This domain includes all Class I a reas within 300 km of the source, plus a 50-km buffer. If there is a need for a refin ed analysis with a finer grid, a supplement to this modeling protocol will be provid ed 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 subdom ains will be performed per the procedures specified in the VISTAS common BART mode ling 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 VIS TAS common BART modeling protocol (Section 4.4.1), which states that we shou ld 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 th e source to include those effects. Since

the DCNA site is tens of kilometers from the neares t Class I area, building downwash effects will not be include in the CALPUFF modeling

.

The POSTUTIL utility program (VISTAS common BART pr otocol Section 4.4.2) will be used to repartition HNO3 and NO3 using VISTAS-provi ded ammonia concentrations derived from previous 2002 CMAQ modeling conducted by EPA or the alternate ammonia concentrations approach recommended by VIST AS, if the CMAQ data is

unavailable.

4.4 Light extinction and haze impact calculations

The CALPOST postprocessor will be used as prescribe d 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 form ula use is the existing (not the November 2005 revised) IMPROVE/EPA formula, which i s 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:

B ext = 3 f(RH) [(NH4)2SO4] + 3 f(RH) [NH4NO3] + 4[OC] + 1[Soil] + 0.6[Coarse Mass] + 10[EC] + b Ray

The concentration, in square brackets, are in ug/m3 and b ext is in units of Mm -1 . The Rayleigh scattering term (b Ray ) has a default value of 10 Mm -1 , as recommended in EPA guidance for tracking reasonable progress (EPA, 200 3a). 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 t he 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 contri bution to visibility impairment is 0.5 deciviews. The VISTAS protocol (Section 4.3.2) indi cates that with the use of the 4-km subregional CALMET database, a source does not caus e or contribute to visibility impairment if the 98 th percentile (or 8 th 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 22 nd highest prediction over the three years modeled sh ould nopt exceed 0.5 deciviews for a source to be exempted from a BART d etermination).

The haze index (HI) is calculated from the extincti on coefficient via the following formula:HI = 10 ln (b ext /10)

where HI is in units of deciviews (dv) and b ext is in Mm -1 . The impact of a source is determined by comparing HI for estimated natural ba ckground conditions with the impact of the source and without the impact of the source.

If the exemption modeling demonstrates that the DCN A 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 wil l proceed to perform BART determination modeling for the baseline each contro l 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 dete rmination 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 pro duced that includes the following elements (as suggested in the VISTAS protocol):

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

• For the CALPUFF modeling domain, a table listing al l Class I areas in the VISTAS domain and those in neighboring states and i mpacts from the BART 4- km grid exemption modeling at those Class I areas w ithin 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 vi sibility impairment due to

source emissions for the 98 th percentile days each year (and the 98 th percentile over all three years modeled) greater than 0.5dv.

• For the Class I area with the maximum impact, a dis cussion of the number of days beyond those excluded (e.g., the 98 th 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 maxim um impact.

• For any finer grid CALPUFF exemption modeling, resu lts 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 f or 4-km exemption modeling.

• For control option modeling, each control option te sted 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 p ollutant emissions and the change in visibility impact from the source as a re sult of the control option. The effectiveness of candidate control options are to b e compared to each other, not to a specific target improvement.