Prepared for: Prepared by:

International Paper AECOM

Mansfield, LA Mill Chelmsford, MA

60485388

March 2016

Environment

Mansfield Mill 

DeSoto Parish, Louisiana 

1-hour SO2 Modeling Report
Prepared for: Prepared by:

International Paper AECOM

Mansfield, LA Mill Chelmsford, MA

60485388

March 2016

Environment

Mansfield Mill 

DeSoto Parish, Louisiana

1-hour SO2 Modeling Report

_________________________________

Prepared By: Brian Stormwind

_________________________________

Reviewed By: Jeffrey Connors
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March 2016

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Contents

1.0 Introduction....................................................................................................................1-1

1.1 Executive Summary.............................................................................................................1-1

1.2 Background..........................................................................................................................1-1

1.3 Overview of Analysis ...........................................................................................................1-2

1.4 Facility Description and Location.........................................................................................1-3

2.0 Model Application and Options....................................................................................2-1

2.1 Source Data .........................................................................................................................2-1

2.1.1 Mansfield Mill ........................................................................................................2-1

2.1.2 Dolet Hills Power Station ......................................................................................2-2

2.2 Receptor Grid.......................................................................................................................2-5

2.3 Dispersion Environment ......................................................................................................2-5

2.4 Meteorological Data for Modeling .......................................................................................2-6

2.5 Background Monitoring Data...............................................................................................2-8

3.0 Modeling Results...........................................................................................................3-1

4.0 References .....................................................................................................................4-1

List of Appendices

Appendix A EPA's Technical Support Document

Appendix B Modeling Protocol Submitted to LDEQ

Appendix C Modeling Archive CD
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List of Tables

Table 2-1 Stack Parameters and Emission Rates – Mansfield Mill ..................................................2-4

Table 2-2 Stack Parameters and Emission Rates – Dolet Hill Main Stack.......................................2-5

Table 2-3 Shreveport Monitor SO2 Design Concentrations (2013-2015) .........................................2-9

Table 2-4 Shreveport Monitor Season and Hour of Day Background Concentrations (2013-2015)2-9

Table 3-1 1-hour SO2 NAAQS Analysis Results - Concentrations (μg/m3) ......................................3-2

Table 3-2 Mansfield Mill Contribution to Modeled NAAQS Exceedances (μg/m3)...........................3-2

List of Figures

Figure 1-1 Location of the Mansfield Mill.............................................................................................1-3

Figure 2-1 Mansfield Mill Sources and Buildings ................................................................................2-3

Figure 2-2 AERMOD Receptor Grid....................................................................................................2-7

Figure 2-3 Location of SO2 Monitor...................................................................................................2-10

Figure 2-4 Shreveport Wind Rose (2012-2014)................................................................................2-11

Figure 3-1 Mansfield Mill Alone Modeling Results (excludes Ambient Background) ........................3-3

Figure 3-2 Receptor Locations of Modeled NAAQS Exceedances....................................................3-4
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1.0 Introduction

1.1 Executive Summary

This document summarizes the results of sulfur dioxide (SO2) air quality modeling analysis for the 

International Paper (IP) Mansfield Mill (Mansfield Mill or the Mill) located in DeSoto Parish, LA. This 

modeling analysis was developed to address questions, uncertainties and data gaps leading to United 

States Environmental Protection Agency’s (EPA) precautionary decision to propose (81 FR 10563) a 

large geographical area surrounding both the Dolet Hills Power Station (Dolet Hills) and IP Mansfield 

Mill as nonattainment with 1-hr SO2 National Ambient Air Quality Standards (NAAQS). This analysis 

considers emissions from both IP and Dolet Hills and provides gap filling information to allow an 

informed SO2 designation decision for DeSoto Parish. 

This analysis shows: 

 Emissions from the IP Mansfield Mill do not cause or significantly contribute (no more than 

0.40% of the total concentration) to any modeled exceedances of the SO2 NAAQS.

 The highest offsite impacts attributed to IP Mansfield Mill sources is 138 g/m3, comfortably

(30%) below the NAAQS (196.5 g/m3).

 Offsite impacts attributed to Mansfield Mill sources are highest within 1 -2 km of the mill 

property boundary. Accordingly, offsite concentrations decrease with increasing distance 

from the mill. At 5-8 kilometers south-south west (in the direction on Dolet Hills), offsite 

impacts from Mansfield Mill sources are reduced to levels close to ambient background 

levels.

 IP Mansfield Mill and Dolet Hills are located approximately 14 km apart. As such, IP’s 

emissions have no significant effect on ambient concentrations near the Dolet Hills site. 

 The highest modeled “combined” impact considering emissions from Dolet Hills, IP Mansfield 

Mill and background levels is 208 g/m3. The Mansfield Mill is conservatively predicted to 

account for 0.23 g/m3(less than 0.50%) of this combined impact.

 Based on these modeling results, the IP Mansfield Mill should be specifically excluded from

and remain outside any SO2 nonattainment area boundary that may result from this 

designation process. 

1.2 Background

On February 11, 2016, the EPA Region 6 issued a letter to the Honorable John Bel Edwards, 

Governor of Louisiana, providing notice that EPA disagreed with Louisiana’s SO2 designation 

recommendation for the area surrounding Dolet Hills Power Station in DeSoto Parish. In short, EPA 

provided notice of its intention to designate a 193 square kilometer (~ 75 sq miles) area in DeSoto 

Parish including the Dolet Hills Power Station and IP’s Mansfield Mill, as nonattainment with the 1-

hour SO2 NAAQS. Shortly thereafter, notice of this proposed designation action was published in the 

Federal Register (81FR 10563, 3/1/16) along with the opening of a 30-day public comment period. 
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The rational for EPA’s proposed action was outlined in a technical support document (TSD; see 

Appendix A). According to the technical support document, EPA ‘s decisions were based solely on air 

quality modeling of emissions from Dolet Hills prepared by the Sierra Club and subsequently 

amended by LADEQ. IP Mansfield Mill’s emissions were not included in this or any subsequent 

modeling evaluations. The work in this document expands the previous modeling effort by 

LDEQ/Sierra Club to include Mansfield Mill sources, and amends the analysis as detailed in 

subsequent sections. . The modeling methodology used in this analysis was originally outlined in the 

letter modeling protocol submitted to LDEQ on March 8, 2016 (provided in Appendix B).

1.3 Overview of Analysis

As described above, modeling in this report was conducted in a manner consistent with the 

LDEQ/Sierra Club analyses with the following exceptions to either refine the analysis or address 

potential deficiencies identified by EPA:

1. All modeling was conducted using AERMOD DEFAULT model options (see Section 2.0).

2. Estimated actual stack exhaust flow rates/exit velocities were used in addition to the actual 

hourly emissions (used in the Sierra Club/LDEQ modeling) for Dolet Hills Power Station (see 

Section 2.1.2). The Sierra Club and LDEQ modeling had used a constant exit velocity based 

on full load operations.

3. Building downwash was incorporated for both Dolet Hills and the Mansfield Mill (see Section 

2.0). No building downwash was included in the modeling performed by Sierra Club or 

LDEQ.

4. Meteorological data was re-processed with the latest version of AERMET, Version 15181

(formerly, data processed with the prior version of AERMET, Version 14134, was used) (see 

Section 2.4).

5. IP Mansfield Mill sources were included in the modeling using their allowable emission rates 

for all SO2 sources except Power Boiler #1 and #2 which were modeled using representative

maximum hourly emission rates (see Section 2.1.1).

6. The modeling was conducted using one comprehensive receptor grid encompassing the area 

surrounding both facilities (see Section 2.2).

7. Ambient background concentrations were updated based on 2013-2015 data for the 

Shreveport Monitor. 2011-2013 was used as part of the TSD, however that data only 

represented 2013 as the monitor was not in operation in 2011 and 2012. For this analysis, 

rather than conservatively adding the modeled design concentration with the monitored 

design concentration for this analysis, as a refinement, the ambient background was

combined with modeled concentrations on a seasonal hour-of-day basis in accordance with 

EPA guidance in their March 1, 2011 clarification memo1and as outlined in EPA’s SO2

Modeling Technical Analysis Document (TAD)2(see Section 2.6). 

Further details on these items and the modeling approach is provided in Section 2 of this report. A 

CD that contains all model input and output files is provided in Appendix C.

 

1

http://www.epa.gov/ttn/scram/guidance/clarification/Additional_Clarifications_AppendixW_Hourly-NO2-NAAQS_FINAL_03-01-

2011.pdf

2 Available at: https://www3.epa.gov/airquality/sulfurdioxide/pdfs/SO2ModelingTAD.pdf
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1.4 Facility Description and Location 

IP's Mansfield Mill is located in a rural area on the northeast side of Mansfield, LA, in the northern 

portion of DeSoto Parish. The facility is a containerboard mill whose sources of SO2 emissions 

include: power boilers that burn a combination of either tire-derived fuel (TDF), gas, bark, and/or oil, 

two recovery furnaces, a lime kiln, an incinerator, a gas turbine, and two smelt dissolving tanks. 

Additional details regarding these sources and their inclusion in the modeling is provided in Section 

2.1.2. The facility location is shown in Figure 1-1. 

Figure 1-1 Location of the Mansfield Mill 

Copyrighted map removed
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2.0 Model Application and Options 

Consistent with the Sierra Club and LDEQ modeling, AERMOD (Version 15181) was used for the 

analysis. AERMOD is the EPA guideline model for short-range transport and has the ability to 

account for the source types and dispersion environment located at, and surrounding, the Mansfield 

Mill and Dolet Hills. AERMOD (USEPA, 2004a) is appropriate for use in many different types of 

dispersion environments including sources subject to building downwash and sources located in flat or 

elevated terrain. 

For this application, AERMOD was applied using all regulatory default options and the modeling 

procedures were consistent with applicable guidance, including the February 2016 “SO2 NAAQS 

Designations Modeling Technical Assistance Document” (TAD) issued by EPA. The current version 

of the TAD references other EPA modeling guidance documents, including the following clarification 

memos (1) the August 23, 2010 “Applicability of Appendix W Modeling Guidance for the 1-hour SO2

NAAQS” and (2) the March 1, 2011 “Additional Clarification Regarding Application W Modeling 

Guidance for the 1-hour NO2 National Ambient Air Quality Standard” (hereafter referred to as the 

“Clarification Memo”). In the March 1, 2011 clarification memo, EPA declares that the memo applies 

equally to the 1-hour SO2 NAAQS even though it was prepared primarily for the 1-hour NO2 NAAQS. 

Based on EPA guidance provided in the TAD, all stacks were modeled with their actual physical stack 

height. In addition, the EPA’s Building Profile Input Program (BPIP-Version 04274) version that is 

appropriate for use with PRIME algorithms in AERMOD were used to incorporate downwash effects in 

the model for all stacks at Dolet Hills and the Mansfield Mill included in the analysis. Figure 2-1 shows 

the Mansfield Mill stacks and building included in the BPIP analysis. The BPIP input and output files 

are provided in the modeling archive in Appendix C. 

2.1 Source Data 

2.1.1 Mansfield Mill 

The Mansfield Mill primary SO2 sources and buildings are shown in Figure 2-1. Source stack 

parameters and emissions are summarized in Table 2-1. 

The EPA TAD allows for use of actual hourly emissions as well as the very conservative approach of 

using maximum potential emission rates. A hybrid approach was used for the Mansfield Mill sources 

by using a conservative constant, representative maximum hourly SO2 emission rate for Power 

Boilers No. 1 and 2 while all other Mill sources were modeled with maximum permitted emission rates. 

Maximum actual SO2 emission factors from the Nos. 1 and 2 Power Boilers were developed from a 

statistical evaluation of the hourly SO2 CEM data (lb/MMBtu) for the period 2012-2014. The resulting 

maximum actual SO2 emission factors are 0.425 lb/MMBtu (No. 1 Power Boiler) and 0.480 lb/MMBtu 

(No. 2 Power Boiler). These maximum actual emission factors were multiplied by the maximum heat 

input of each boiler (760 MMBtu/hr) to obtain the maximum actual SO2 emission rate for the Nos. 1 

and 2 Power Boilers (323.3 and 364.9 lbs/hr, respectively). These rates were then conservatively 

modeled for every hour for the period 2012-2014. 

Comparison of the maximum actual hourly SO2 emission rate to the actual hourly SO2 emission rate 

shows that 99.5% of all actual hourly SO2 rates are below the maximum actual rates modeled. 

Review of the remaining 0.5% of the actual rates determined to be above the modeled maximum 

actual rates shows these periods to be atypical operations. 
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Given the low fraction of time and intermittent nature of the actual emission rates are above the two 

proposed maximum actual emission rates, use of these maximum actual SO2 rates will provide a 

conservative depiction of the modeled concentrations associated with the 1-hour SO2 NAAQS given 

its percentile basis (99th percentile). 

Exhaust parameters were taken from the facility Title V operating permit and were verified by the 

Mansfield Mill.

2.1.2 Dolet Hills Power Station

As discussed in EPA’s TSD, the Sierra Club and LDEQ modeling of Dolet Hills was conducted with 3 

years, 2012-2014, of actual emission data coupled with constant exit flowrate/velocity and 

temperature based on 100% load (the latter was indicated by EPA to be a shortcoming of the 

analysis). 

In order to address EPA’s comment, hourly exit flowrate/velocity data were developed for this 

application to refine the analysis. Direct measurements of actual hourly exit flowrate/velocity and 

temperature for Dolet Hills were not available. However, heat input, MMBtu/hr, was available for Dolet 

Hills from the EPA Air Markets Program Data3. Concurrent with the hourly emission rates, hourly 

values of exit velocity for the Dolet Hills stack were computed based on the product of the full load 

exhaust flowrate (assumed to be 84.78 ft/s according to the LDEQ and Sierra Club modeling) and the 

ratio of the actual hourly heat input/maximum load heat input (7,600 MMBtu/hr). The full load exit 

temperature was not adjusted as significant variability in the temperature as a function of load is not 

expected. The 84.78 ft/s full load exhaust flowrate is also fairly consistent with data available in the 

Tile V Permit renewal for the Dolet Hills available on LDEQ’s website (October 2013, Permit Activity 

No. PER20100002). This Title V Permit renewal was also used as a reference to determine the 

maximum heat input at 7,600 MMBtu/hr to the unit.

The physical stack parameters for the Dolet Hills main stack and full load exhaust parameters are 

summarized in Table 2-2.

 

3

https://ampd.epa.gov/ampd/
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Figure 2-1 Mansfield Mill Sources and Buildings
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Table 2-1 Stack Parameters and Emission Rates – Mansfield Mill

Parameter

Source

No. 1 Power 

Boiler

No. 2 Power 

Boiler Lime Kiln

No. 1 

Recovery 

Boiler

No. 2 

Recovery 

Boiler

No. 1 Smelt 

Dissolving 

Tank

No. 2 Smelt 

Dissolving 

Tank

Gas 

Turbine/HR

SG Stack

HVLC/LVHC 

Incinerator

Stack ID 01-78 02-78 03-78 04-78 05-78 06-78 07-78 13-93 57-99

Base Elevation (ft) 179.8 179.1 179.1 179.1 179.1 179.1 179.1 179.5 179.1

Stack Height (ft) 263.0 263.0 120.0 263.0 263.0 261.0 261.0 113.0 100.0

Stack Diameter (ft) 9.5 9.5 8.0 9.9 9.9 7.0 7.0 11.7 2.5

Exhaust Velocity (ft/sec) 101.5 101.5 23.4 96.2 96.2 30.9 30.9 47.8 33.3

Exhaust Temperature (°F) 426.0 426.0 192.0 400.0 400.0 160.1 160.1 272.0 130.0

SO2 Emission Rate (lb/hr) 323.2 364.9 1.20 217.64 217.64 1.35 1.35 <0.001 10.93
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Table 2-2 Stack Parameters and Emission Rates – Dolet Hill Main Stack

Parameter Main Boiler Stack

Base Elevation (ft) 244.2

Stack Height (ft) 525.0

Stack Diameter (ft) 25.0

Exhaust Velocity (ft/sec) Varied hourly

Exhaust Temperature (°F) 163.0

SO2 Emission Rate (lb/hr) Varied hourly

2.2 Receptor Grid

The modeling was conducted using one comprehensive receptor grid encompassing the area 

surrounding Dolet Hills and the Mansfield Mill. The grid extends out a minimum of 20 kilometers in all 

directions from each facility. The grid was based on the following specifications:

 25-meter spacing around each facility’s ambient air boundary;

 Beyond the ambient air boundary from each facility, 100-meter spaced receptors were used 

out to 3-5 km depending on the direction from the facilities;

 Beyond the 100-meter spaced receptors a 250-meter spaced grid were used out to an 

additional 4-8 kilometers from each facility depending on the direction; 

 Beyond the 250-meter spaced receptors a 500-meter spaced grid will be used out to an 

additional 5 kilometers; and 

 Beyond the 500-meter spaced receptors a 250-meter spaced grid will be used out to an 

additional 10 kilometers. 

The receptor grid is shown in Figure 2-2.

The extent of this grid was sufficient to capture the maximum modeled impacts from each facility as 

well as the combined impacts from both facilities.

The receptor grid was based on Universal Transverse Mercator (UTM) coordinates referenced to NAD 

83 datum and in zone 17. AERMAP (version 11103), the AERMOD terrain preprocessor program, 

was used to calculate terrain elevations and critical hill heights for the modeled receptors (NAD83 

datum and zone 18) using National Elevation Data (NED). The NED dataset was be downloaded 

from the USGS website (http://viewer.nationalmap.gov/viewer/) and consisted of 1 arc second (~30 m 

resolution) NED. As per the AERMAP User’s Guide (USEPA, 2004c), the domain was sufficient to 

ensure all significant nodes are included such that all terrain features exceeding a 10% elevation 

slope from any given receptor, are considered.

2.3 Dispersion Environment

Consistent with modeling performed by the Sierra Club and LDEQ, and EPA’s findings in the TSD, 

AERMOD was applied in rural mode given the predominantly rural land use of the study area.
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2.4 Meteorological Data for Modeling

The same three years of meteorological data used by Sierra Club and LDEQ was used in this 

application of AERMOD; 2012-2014 data from Shreveport, LA. The data were reprocessed with the 

latest version of EPA’s AERMET (USEPA, 2004b), version 15181 (the data were formerly processed 

with version 14134) and AERMINUTE, version 15272. We do note that a comparison of both data 

sets indicated that there were no differences in the meteorological data processed with either version 

of AERMET.
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Figure 2-2 AERMOD Receptor Grid
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2.5 Background Monitoring Data

Ambient air quality data are used to represent the contribution of non-modeled sources to the total 

ambient air pollutant concentrations for the NAAQS analysis.

The Sierra Club and LDEQ analysis utilized monitored data from the Caddo Parish monitor in 

Shreveport, approximately 40 kilometers north of the Mansfield Mill (see Figure 2-3). While EPA 

states in the TAD that the Shreveport monitor has “the lowest measured background concentration in 

the state”, the Shreveport monitor is the most representative monitor available for the analysis, if not 

conservative.

The Mansfield Mill and Dolet Hills facilities are surrounded by rural land use generally consisting of 

agricultural and undeveloped forested and grassland areas, whereas the Shreveport monitor is in a 

more urban/developed area consisting of commercial and compact residential land uses. A threeyear (2012-2014) wind rose of the Shreveport met data (see Figure 2-4) indicates winds in the region 

are predominantly from the south. Winds blowing from the south would tend to transport SO2

emissions from both the power station and mill toward the Shreveport monitor and therefore, this 

monitor may be influenced to some degree from the emissions from power station and mill. 

Therefore the use of this monitor may result in some double counting of emissions in the analysis. 

For these reasons, the Shreveport monitor should be conservative to represent background in the 

vicinity of the Mansfield Mill and Dolet Hills.

EPA’s recommends a tiered approach for adding monitored background concentrations (representing 

non-modeled sources) in the NAAQS analysis in the Clarification Memo . The first tier approach is 

conservatively based on adding the monitored design value (3-year average 99th percentile daily 1-

hour maximum concentration) to the modeled design value. The second tier uses a temporally 

varying approach, based on combining the monitored concentrations, by hour of day and season, with 

the hourly modeling results. The total hourly modeled plus monitored concentrations are then used to 

determine the design concentration for comparison to the NAAQS. These computations are all done 

within AERMOD. 

Therefore, rather than conservatively adding the modeled design concentration with the monitored 

design concentration for this analysis, the second tier refinement was used where the ambient 

background concentration was combined with modeled concentrations on a seasonal hour-of-day 

basis in accordance with EPA guidance in the Clarification Memo and as outlined in the TAD. Note 

that for this application, the ambient background concentrations were updated based on 2013-2015 

data for the Shreveport monitor. Data from 2011-2013 were reported to be used by Sierra Club and 

LDEQ as discussed in the TSD, however it appears that data only represented 2013 as the monitor 

was not in operation in 2011 and 2012. Therefore, the more recent data were used.

Table 2-3 shows the three year design concentrations for the Shreveport monitor.

Table 2-4 shows the season and hour of day ambient background concentrations used for the 

modeling. A spreadsheet with the season and hour of day background calculations is provided with 

the modeling archive in Appendix C.
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Table 2-3 Shreveport Monitor SO2 Design Concentrations (2013-2015)

Monitor Year

Annual Data Capture 99th Percentile 

Concentration 

(ppb)

Design 

Concentration

(3-year average)

hours % ppb μg/m3

Shreveport 

Monitor

2013 8588 98% 12

2014 8589 98% 14 12 32.3

2015 8367 96% 11

Table 2-4 Shreveport Monitor Season and Hour of Day Background Concentrations (2013-2015)

Hour

Season (ppb)

Winter Spring Summer Fall

1 2.5 2.6 2.6 2.1

2 2.8 2.6 2.9 1.9

3 3.0 2.5 2.6 2.1

4 2.9 2.4 2.7 2.4

5 2.9 2.4 2.6 2.1

6 2.7 2.5 2.6 2.0

7 2.3 2.7 2.8 1.9

8 2.4 3.2 5.2 2.7

9 3.2 3.8 9.3 3.8

10 2.7 4.4 9.5 5.3

11 5.1 4.3 6.9 7.0

12 6.1 4.5 6.2 4.6

13 6.4 4.1 4.7 3.7

14 5.1 3.7 3.8 4.2

15 4.2 3.3 3.7 3.1

16 4.1 3.0 4.5 3.8

17 3.7 3.2 3.7 3.0

18 3.1 3.1 3.6 3.4

19 3.1 2.9 4.2 3.3

20 2.8 2.7 3.5 2.7

21 3.7 2.7 3.1 2.1

22 3.2 3.1 2.7 2.0

23 3.9 3.5 3.8 2.1

24 3.1 2.9 2.8 2.3
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Figure 2-3 Location of SO2 Monitor 

Copyrighted map removed
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Figure 2-4 Shreveport Wind Rose (2012-2014)
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3.0 Modeling Results

AERMOD was applied for the 3-year meteorological data set to determine the combined 1-hour SO2

modeled concentrations for the Mansfield Mill sources and the Dolet Hills main stack. As noted in 

Section 2.5, AERMOD was also applied with season/hour-of-day ambient background concentrations 

to represent non-modeled sources in the NAAQS analysis. AERMOD computes the total design 

concentrations in the form of the NAAQS which is the highest 3-year average 99th percentile of the 

daily 1-hour maximum concentrations. 

Table 3-1 summarizes the AERMOD modeled concentrations as well as source culpability. The 

following summarizes of the results in Table 3-1:

 Overall highest concentration due to all sources plus monitored background is 207.57 μg/m3.

This maximum total modeled concentration exceeds the NAAQS (196.5 μg/m3) and is 

primarily due to Dolet Hill emissions. The Mansfield Mill sources contribution to this total 

concentration is only 0.23 μg/m3(~0.10% of the total). 

 Maximum modeled concentration due to all soucres (plus monitored background) where 

Mansfield Mill sources have a significant impact (≥ 7.9 μg/m3) is 152.21 μg/m3; the 

contribution from the Mansfield Mill sources is 8.50 μg/m3(5.6% of the total). 

 Highest concentration (plus background) due to Mansfield Mill sources alone is 137.59 μg/m3. 

Figure 3-1 presents an isopleth of the modeling results for the Mansfield Mill sources alone. 

As shown in Figure 3-1, the highest concentrations associated with the Mansfield Mill sources 

are at the facility boundary, are below the NAQQS, and they drop off significantly with 

distance from the Mill. Figure 3-1 also shows that at 5-8 kilometers from the Mill center, the 

modeled concentrations (attributable to the Mill alone) drop to nearly the same concentration 

levels of the ambient background. This distance is well short of the Dolet Hills Power Station 

also shown in Figure 3-1.

In addition, there are a number of other instances and receptor locations where the NAAQS was 

exceeded. The location of these receptors is shown in Figure 3-2. A detailed summary of all modeled 

exceedances is provided in Table 3-2. This summary shows that the Mansfield Mill sources do not 

significantly contribute to any of the modeled exceedances. The maximum modeled contribution to 

any of the modeled exceedances due to the Mansfield Mill sources is 0.79 μg/m3(~0.40% of NAAQS). 

Figure 3-2 also shows how large the proposed NAA made by EPA is relative to the area of actual 

modeled exceedances.

These results demonstrate that the Mansfield Mill does not contribute significantly to any of the 

modeled exceedances which are due to Dolet Hills. The modeling analysis also demonstrates that 

the Mansfield Mill itself does not cause any modeled exceedance of the NAAQs.
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Table 3-1 1-hour SO2 NAAQS Analysis Results - Concentrations (μg/m3)

Case Total 

Concentration(1)

Contribution to Total

NAAQS SIL

Dolet Hills 

Mansfield 

Mill

Monitored 

Background

Overall Maximum 207.57 189.50 0.23 17.85 196 7.9

Maximum where 

Mansfield Significant 152.21 132.29 8.50 11.42 196 7.9

Maximum due to 

Mansfield Mill Alone 137.59 -- 115.70 21.88 196 7.9

1) 1-hour SO2 99

th percentile design concentrations.

Table 3-2 Mansfield Mill Contribution to Modeled NAAQS Exceedances (μg/m3)

Receptor Maximum Design 

Concentration

(with Background)

Mansfield Mill Contribution 

to Maximum Design 

Concentration

X (m) Y (m)

443400.00 3544350.00 207.57 0.23

443300.00 3544350.00 207.25 0.55

443000.00 3544450.00 205.42 0.36

443500.00 3544350.00 204.59 0.23

443200.00 3544350.00 204.32 0.67

442900.00 3544450.00 203.86 0.79

443100.00 3544450.00 202.45 0.36

443100.00 3544350.00 201.29 0.67

443600.00 3544350.00 201.20 0.23

443200.00 3544450.00 200.09 0.34

442800.00 3544450.00 199.35 0.79

442600.00 3544550.00 198.43 0.34

443000.00 3544350.00 198.40 0.79

442700.00 3544550.00 198.18 0.32

443300.00 3544450.00 197.67 0.34

443700.00 3544250.00 197.36 0.55

442800.00 3544550.00 197.31 0.47

442500.00 3544550.00 197.27 0.38

442900.00 3544550.00 197.05 0.36

443800.00 3544250.00 196.27 0.23

443700.00 3544350.00 196.20 0.18
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Figure 3-1 Mansfield Mill Alone Modeling Results (excludes Ambient Background)
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Figure 3-2 Receptor Locations of Modeled NAAQS Exceedances

*Receptor locations with modeled exceedances are shown in blue.

EPA proposed NAA outlined in with bold blue line
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4.0 References

US EPA 1985. Guideline for the Determination of Good Engineering Practice Stack Height (Technical 

Support Document for the Stack Height Regulations) - Revised. EPA-450/4-80-023R, US EPA, 

Research Triangle Park, NC 27711.

US EPA 2004a. User’s Guide for the AMS/EPA Regulatory Model (AERMOD). EPA-454/B-03-001 

(September 2004 – Addendum March 2011). Office of Air Quality Planning and Standards, Research 

Triangle Park, North Carolina.

US EPA 2004b. User’s Guide for the AERMOD Meteorological Preprocessor (AERMET). (EPA454/B-03-002, November 2004 – Addendum February 2011). Office of Air Quality Planning and 

Standards, Research Triangle Park, North Carolina.

US EPA 2004c. User’s Guide for the AERMOD Terrain Preprocessor (AERMAP). (EPA-454/B-03-

003, October 2004 – Addendum March 2011). Office of Air Quality Planning and Standards, Research 

Triangle Park, North Carolina.

US EPA 2011. Additional Clarification Regarding Application of Appendix W Modeling Guidance for 

the 1-hour NO2 NAAQS. (March 1, 2011). Office of Air Quality Planning and Standards, Research 

Triangle Park, North Carolina. Available at: http://www.epa.gov/ttn/scram/Additional_Clarifications_

AppendixW_Hourly-NO2-NAAQS_FINAL_03-01-2011.pdf

US EPA 2015. Docket ID No. EPA–HQ–OAR–2013–0711, August 10, 2015. Available at: 

http://www.epa.gov/oaqps001/sulfurdioxide/pdfs/so2_drr__final_081215.pdf.
AECOM Mansfield Mill SO2 Modeling Report Environment

60432329 March 2016

1

Appendix A

EPA's Technical Support 

Document
Technical Support Document 

Louisiana 

Area Designations for the 2010 SO2 Primary National Ambient Air Quality Standard 

Summary 

Pursuant to section 107(d) of the Clean Air Act (CAA), the U.S. Environmental Protection 

Agency (EPA) must designate areas as either “unclassifiable,” “attainment,” or “nonattainment” 

for the 2010 one-hour sulfur dioxide (SO2) primary national ambient air quality standard 

(NAAQS). The CAA defines a nonattainment area as one that does not meet the NAAQS or that 

contributes to a violation in a nearby area. An attainment area is defined as any area other than a 

nonattainment area that meets the NAAQS. Unclassifiable areas are defined as those that cannot 

be classified on the basis of available information as meeting or not meeting the NAAQS. 

Louisiana submitted updated recommendations on November 17, 2015, ahead of a July 2, 2016, 

deadline for the EPA to designate certain areas established by the U.S. District Court for the 

Northern District of California. This deadline is the first of three deadlines established by the 

court for the EPA to complete area designations for the 2010 SO2 NAAQS. Table 1 below lists 

Louisiana’s recommendations and identifies the counties or portions of counties in Louisiana that 

the EPA intends to designate by July 2, 2016 based on an assessment and characterization of air 

quality through ambient air quality data, air dispersion modeling, other evidence and supporting 

information, or a combination of the above. 

Table 1: Louisiana’s Recommended and EPA’s Intended Designations 

Area 

Louisiana’s 

Recommended 

Area Definition 

Louisiana’s 

Recommended 

Designation 

EPA’s Intended Area 

Definition 

EPA’s Intended 

Designation 

DeSoto Parish, 

Louisiana 

Within the 

Southeast 

Quadrant of 

DeSoto Parish 

Attainment 

Portions of Desoto 

Parish, Louisiana: 

The area bounded by the 

following UTM 

Coordinates* (NAD 83 

Datum, UTM Zone 15): 

X Y 

441287, 3541019 

441287, 3562019 

450500, 3562019 

450500, 3541019 

* Nonattainment area 

excludes portions of Red 

River Parish, Louisiana 

that fall within this 

UTM-based boundary 

Nonattainment 
2

Calcasieu Parish, 

Louisiana 

Within 

Calcasieu Parish 

Borders 

Attainment Same as State’s 

Recommendation Unclassifiable 

Background 

On June 3, 2010, the EPA revised the primary (health based) SO2 NAAQS by establishing a new 

one-hour standard at a level of 75 parts per billion (ppb) which is attained when the three-year 

average of the 99th percentile of one-hour daily maximum concentrations does not exceed 75 

ppb. This NAAQS was published in the Federal Register on June 22, 2010 (75 FR 35520) and is 

codified at 40 CFR 50.17. The EPA determined this is the level necessary to protect public health 

with an adequate margin of safety, especially for children, the elderly and those with asthma. 

These groups are particularly susceptible to the health effects associated with breathing SO2. The 

two prior primary standards of 140 ppb evaluated over 24 hours, and 30 ppb evaluated over an 

entire year, codified at 40 CFR 50.4, remain applicable.1 However, the EPA is not currently 

designating areas on the basis of either of these two primary standards. Similarly, the secondary 

standard for SO2, set at 500 ppb evaluated over 3 hours has not been revised, and the EPA is also 

not currently designating areas on the basis of the secondary standard. 

General Approach and Schedule 

Section 107(d) of the Clean Air Act requires that, no later than one year after promulgation of a 

new or revised NAAQS, state governors must submit their recommendations for designations 

and boundaries to EPA. Section 107(d) also requires the EPA to provide notification to states no 

less than 120 days prior to promulgating an initial area designation that is a modification of a 

state’s recommendation. If a state does not submit designation recommendations, the EPA will 

promulgate the designations that it deems appropriate. If a state or tribe disagrees with the EPA’s 

intended designations, they are given an opportunity within the 120-day period to demonstrate 

why any proposed modification is inappropriate. 

On August 5, 2013, the EPA published a final rule establishing air quality designations for 29 

areas in the United States for the 2010 SO2 NAAQS, based on recorded air quality monitoring 

data from 2009 - 2011 showing violations of the NAAQS (78 FR 47191). In that rulemaking, the 

EPA committed to address, in separate future actions, the designations for all other areas for 

which the Agency was not yet prepared to issue designations. 

Following the initial August 5, 2013 designations, three lawsuits were filed against the EPA in 

different U.S. District Courts, alleging the agency had failed to perform a nondiscretionary duty 

under the CAA by not designating all portions of the country by the June 2013 deadline. In an 

                                                            

1

 40 CFR 50.4(e) provides that the two prior primary NAAQS will no longer apply to an area one year after its 

designation under the 2010 NAAQS, except that for areas designated nonattainment under the prior NAAQS as of 

August 22, 2010, and areas not meeting the requirements of a SIP Call under the prior NAAQS, the prior NAAQS 

will apply until that area submits and EPA approves a SIP providing for attainment of the 2010 NAAQS. 
3

effort intended to resolve the litigation in one of those cases, plaintiffs Sierra Club and the 

Natural Resources Defense Council and the EPA filed a proposed consent decree with the U.S. 

District Court for the Northern District of California. On March 2, 2015, the court entered the 

consent decree and issued an enforceable order for the EPA to complete the area designations 

according to the consent decree schedule. 

According to the consent decree, the EPA must complete the remaining designations on a 

schedule that contains three specific deadlines. By no later than July 2, 2016 (16 months from the 

court’s order), the EPA must designate two groups of areas: (1) areas that have newly monitored 

violations of the 2010 SO2 NAAQS and (2) areas that contain any stationary sources that had not 

been announced as of March 2, 2015 for retirement; and that according to the EPA’s Air Markets 

Database emitted in 2012 either (i) more than 16,000 tons of SO2 or (ii) more than 2,600 tons of 

SO2 with an annual average emission rate of at least 0.45 pounds of SO2 per one million British 

thermal units (lbs SO2/mmBTU). Specifically, a stationary source with a coal-fired unit that as 

of January 1, 2010 had a capacity of over 5 megawatts and otherwise meets the emissions 

criteria, is excluded from the July 2, 2016 deadline if it had announced through a company public 

announcement, public utilities commission filing, consent decree, public legal settlement, final 

state or federal permit filing, or other similar means of communication, by March 2, 2015, that it 

will cease burning coal at that unit. 

The last two deadlines for completing remaining designations are December 31, 2017, and 

December 31, 2020. The EPA has separately promulgated requirements for states and other air 

agencies to provide additional monitoring or modeling information on a timetable consistent with 

these designation deadlines. We expect this information to become available in time to help 

inform these subsequent designations. These requirements were promulgated on August 21, 2015 

(80 FR 51052), in a rule known as the SO2 Data Requirements Rule (DRR). 

 

The EPA through a March 20, 2015 memorandum from Stephen D. Page, Director, U.S. EPA, 

Office of Air Quality Planning and Standards issued updated designations guidance, to Air 

Division Directors, U.S. EPA Regions I-X. This memorandum supersedes earlier designation 

guidance for the 2010 SO2 NAAQS, issued on March 24, 2011, and it identifies factors that the 

EPA intends to evaluate in determining whether areas are in violation of the 2010 SO2 NAAQS. 

The guidance also contains the factors the EPA intends to evaluate in determining the boundaries 

for all remaining areas in the country, consistent with the court’s order and schedule. These 

factors include: 1) Air quality characterization via ambient monitoring or dispersion modeling 

results; 2) Emissions-related data; 3) Meteorology; 4) Geography and topography; and 5) 

Jurisdictional boundaries. This guidance was supplemented by two technical assistance 

documents intended to assist states and other interested parties in their efforts to characterize air 

quality through air dispersion modeling or ambient air quality monitoring for sources that emit 

SO2. Notably, the EPA released its most recent versions of documents titled, “SO2 NAAQS 

Designations Modeling Technical Assistance Document” (Modeling TAD) and “SO2 NAAQS 

Designations Source-Oriented Monitoring Technical Assistance Document” (Monitoring TAD) 

in December 2013. 
4

Based on ambient air quality data collected between 2012 and 2014, no violations of the 2010 

SO2 NAAQS have been recorded in any undesignated part of the state.2

 However, there are 3 

sources in the state meeting the emissions criteria of the consent decree for which the EPA must 

complete designations by July 2, 2016. In this draft technical support document, the EPA 

discusses its review and technical analysis of Louisiana’s recommendations for the areas that we 

must designate. The EPA also discusses any intended modifications from the state’s 

recommendation based on all available data before us. 

The following are definitions of important terms used in this document: 

1) 2010 SO2 NAAQS – The primary NAAQS for SO2 promulgated in 2010. This NAAQS is 

75 ppb, based on the three-year average of the 99th percentile of the annual distribution 

of daily maximum one-hour average concentrations. See 40 CFR 50.17. 

2) Design Value - a statistic computed according to the data handling procedures of the 

NAAQS (in 40 CFR part 50 Appendix T) that, by comparison to the level of the NAAQS, 

indicates whether the area is violating the NAAQS. 

3) Designated nonattainment area – an area which the EPA has determined has violated the 

2010 SO2 NAAQS or contributed to a violation in a nearby area. A nonattainment 

designation would reflect considerations of state recommendations and all of the 

information discussed in this document. The EPA’s decision would be based on all 

available information including the most recent 3 years of air quality monitoring data, 

available modeling analysis, and any other relevant information. 

4) Designated unclassifiable area – an area which the EPA cannot determine based on all 

available information whether or not it meets the 2010 SO2 NAAQS. 

5) Designated unclassifiable/attainment area – an area which the EPA has determined to 

have sufficient evidence to find either is attaining or is likely to be attaining the NAAQS. 

The EPA’s decision would be based on all available information including the most 

recent 3 years of air quality monitoring data, available modeling analysis, and any other 

relevant information. 

6) Modeled violation – a violation based on air dispersion modeling. 

7) Recommended attainment area – an area a state or tribe has recommended that the EPA 

designate as attainment. 

8) Recommended nonattainment area – an area a state or tribe has recommended that the 

EPA designate as nonattainment. 

9) Recommended unclassifiable area – an area a state or tribe has recommended that the 

EPA designate as unclassifiable. 

                                                            

2

 For designations based on ambient air quality monitoring data that violates the 2010 SO2 NAAQS, the consent 

decree directs the EPA to evaluate data collected between 2013 and 2015. Absent complete, quality assured and 

certified data for 2015, the analyses of applicable areas for the EPA’s intended designations will be informed by data 

collected between 2012 and 2014. States with monitors that have recorded a violation of the 2010 SO2 NAAQS 

during these years have the option of submitting complete, quality assured and certified data for calendar year 2015 

by April 19, 2016 to the EPA for evaluation. If after our review, the ambient air quality data for the area indicates 

that no violation of the NAAQS occurred between 2013 and 2015, the consent decree does not obligate the EPA to 

complete the designation. Instead, we may designate the area and all other previously undesignated areas in the state 

on a schedule consistent with the prescribed timing of the consent decree, i.e., by December 31, 2017, or December 

31, 2020. 
5

10) Recommended unclassifiable/attainment area – an area a state or tribe has recommended 

that the EPA designate as unclassifiable/attainment. 

11) Violating monitor – an ambient air monitor meeting all methods, quality assurance and 

siting criteria and requirements whose valid design value exceeds 75 ppb, based on data 

analysis conducted in accordance with Appendix T of 40 CFR part 50. 

 
6

Technical Analysis for the DeSoto Parish, Louisiana Area 

Introduction 

The Dolet Hills Power Station contains a stationary source that according to the EPA’s Air 

Markets Database, emitted in 2012 either more than 16,000 tons of SO2 or more than 2,600 tons 

of SO2 and had an annual average emission rate of at least 0.45 pounds of SO2 per one million 

British thermal units (lbs SO2/mmBTU). As of March 2, 2015, this stationary source has not met 

the specific requirements for being “announced for retirement.” Specifically, in 2012, the Dolet 

Hills Power Station (Dolet Hills) emitted 20,887 tons of SO2, and had an emissions rate of 0.80 

lbs SO2/mmBTU. Pursuant to the March 2, 2015 consent decree, the EPA must designate the 

area surrounding the facility by July 2, 2016. 

In its November 17, 2015 recommendation, Louisiana through its state environmental agency, 

the Louisiana Department of Environmental Quality (LDEQ), recommended that the area 

surrounding Dolet Hills, specifically the southeast quadrant of DeSoto Parish, be designated as 

unclassifiable based on information included in a monitoring siting report. The report assessed 

and characterized air quality for the facility and other nearby sources. Our review and analysis 

indicated that this initial modeling intended to justify the siting of monitors did not follow either 

the monitoring TAD or modeling TAD in certain respects and only provided normalized 

estimates of impacts rather than absolute results. 

The EPA also received air modeling performed by Sierra Club (initially in September 2015 and 

updated in December 2015), asserting that the area around Dolet Hills experiences impacts in 

exceedance of the NAAQS. The state reviewed this modeling, and subsequently performed its 

own revised modeling using the input parameters provided by Sierra Club. These assessments 

and characterization were performed using air dispersion modeling software, i.e., AERMOD, 

analyzing actual emissions. However, the state factored and used the currently non-default beta 

option low wind speed modification (LOWWIND3). This revised modeling using LOWWIND3 

predicted peak concentrations slightly below the NAAQS. As a result, the state changed its 

unclassifiable recommendation to attainment. 

 

The EPA notes that the use of beta options, such as ADJ_U* and LOWWIND3, in AERMOD for 

any regulatory applications requires adherence with Appendix W, Section 3.2.2. This is further 

explained in the EPA’s December 10, 2015 Memorandum titled, “Clarification on the Approval 

Process for Regulatory Application of the AERMOD Modeling System Beta Options.” Among 

other conditions, the use of beta options requires consultation with the appropriate EPA Regional 

Offices. Upon concurrence by the EPA’s Modeling Clearinghouse, EPA Regional Offices may 

approve the use of these beta options for regulatory applications as an alternative model. 

However, LDEQ performed air dispersion modeling intended to characterize air quality as a 

result of SO2 emissions from Dolet Hills without prior consultation with and approval from an 

EPA Regional Office, and therefore has not met the applicable regulatory requirements 

contained in Appendix W, Section 3.2.2. As a result, the EPA does not believe that the air quality 

modeling results obtained from the use of these beta options can be used as a reliable indicator of 

attainment status in the area around Dolet Hills until appropriate alternative model approval is 
7

granted or these beta options are promulgated as regulatory options in AERMOD through EPA 

rulemaking. 

After careful review of the state’s assessment, supporting documentation, and all available data, 

the EPA does not agree with the state’s recommendation for the area, and intends to designate 

the area as non-attainment. Specifically, the boundaries for our intended nonattainment area 

consist of the portions of DeSoto Parish bound by the following Universal Transverse Mercator 

(UTM) Coordinates (NAD 83 Datum, UTM Zone 15): 

X Y 

441287 3541019

441287 3562019

450500 3562019

450500 3541019

However, this intended nonattainment area excludes portions of Red River Parish, Louisiana that 

fall within this UTM-based boundary. The modeling analyses indicates that there were no 

violating receptors in Red River Parish. Also, Figures 3 and 4 show that the impact area based on 

actual emissions did not extend past DeSoto Parish borders and, therefore, the defined 

nonattainment area should be contained within. 

Dolet Hills is located in northwestern Louisiana in the eastern portion of DeSoto Parish. As seen 

in Figure 1 below, the facility is located approximately 12.5 km directly east of the center of 

Mansfield. Also included in the figure are major nearby emitters of SO2, and the DeSoto Parish 

boundary. EPA’s intended nonattainment designation area is the area within DeSoto Parish that 

lies within a rectangular area defined by UTM coordinates (See Figure 1 below). The 

nonattainment area excludes portions of Red River Parish, Louisiana that fall within this UTMbased boundary. 
8

Figure 1: SO2 Nonattainment Area Designation for Dolet Hills 

The discussion and analysis that follows below will reference the state’s use of the Modeling 

TAD in its revised modeling analysis, Sierra Club’s use of the Modeling TAD, the EPA’s 

assessment of the competing modeling in accordance with the Modeling TAD, and the factors 

for evaluation contained in the EPA’s March 20, 2015 guidance, as appropriate. 

Detailed Assessment 

Air Quality Data 

There are no SO2 air quality monitors in DeSoto Parish. There are no SO2 air quality monitors in 

surrounding parishes that are representative of the maximum or higher elevated levels of SO2

around Dolet Hills. 
9

Model Selection and Modeling Components 

The EPA’s Modeling TAD notes that for area designations under the 2010 SO2 NAAQS, the 

AERMOD modeling system should be used, unless use of an alternative model can be justified. 

In some instances, the recommended model may be a model other than AERMOD, such as the 

BLP model for buoyant line sources. The AERMOD modeling system contains the following 

components: 

- AERMOD: the dispersion model 

- AERMAP: the terrain processor for AERMOD 

- AERMET: the meteorological data processor for AERMOD 

- BPIPPRIME: the building input processor 

- AERMINUTE: a pre-processor to AERMET incorporating 1-minute automated surface 

observation system (ASOS) wind data 

- AERSURFACE: the surface characteristics processor for AERMET 

- AERSCREEN: a screening version of AERMOD 

The Sierra Club initial modeling (Sept. 2015) was conducted with the previous regulatory 

version of AERMOD (v14134). The state reviewed Sierra Club’s modeling and found that the 

inputs for the actual emissions were acceptable. The state reran the Sierra Club modeling on the 

most recent version of AERMOD version 15181, using LOWWIND3 as the only altered model 

option. A discussion of the individual components will be referenced in the corresponding 

discussion that follows as appropriate. Sierra Club submitted updated modeling in December 

2015 and used the most recent version of AERMOD that was released in July 2015 (v15181).

Modeling Parameter: Rural or Urban Dispersion 

The EPA’s recommended procedure for characterizing an area by prevalent land use is based on 

evaluating the dispersion environment within 3 km of the facility. According to the EPA’s 

modeling guidelines, urban dispersion coefficients are to be used in the dispersion modeling 

analysis if more than 50% of the area within a 3 km radius of the facility is classified as urban. 

Otherwise, the source is considered a rural source. 

When performing the modeling for the area of analysis, the state agreed with Sierra Club’s 

analysis to use rural mode. Sierra Club used a Geographic Information System (GIS) to 

determine whether rural or urban dispersion coefficients applied. Land use within a threekilometer radius circle surrounding the facility was considered. USEPA’s AERSURFACE v. 

13016 was used to develop the meteorological data for the modeling analysis. This model was 

also used to evaluate surrounding land use within 3 kilometers. Based on the output from the 

AERSURFACE, approximately 0.02% of surrounding land use around the modeled facility was 

of urban land use types including Type 21 – Low Intensity Residential, Type 22 – High Intensity 

Residential and Type 23 – Commercial / Industrial / Transportation. This is less than the 50% 

value considered appropriate for the use of urban dispersion coefficients. Based on the 

AERSURFACE analysis, it was concluded that the rural option would be used for the modeling 

summarized in this report. 
10

Modeling Parameter: Area of Analysis (Receptor Grid) 

The EPA believes that a reasonable first step toward characterization of air quality in the area 

surrounding Dolet Hills is to determine the extent of the area of analysis, i.e., receptor grid. 

Considerations presented in the Modeling TAD include but are not limited to: the location of the 

SO2 emission sources or facilities considered for modeling; the extent of significant 

concentration gradients of nearby sources; and sufficient receptor coverage and density to 

adequately capture and resolve the model predicted maximum SO2 concentrations. 

For the DeSoto Parish area, the state recognized in its monitoring siting report 519 permitted 

facilities in the parish, with 10 Title V facilities, and only one that represented a major SO2

emitter within 20 kilometers (km) in any direction of Dolet Hills. The state determined that this 

was the appropriate distance as described in the 2013 Monitoring TAD. In addition to Dolet 

Hills, one other major emitter of SO2 is located within the area of analysis, International Paper 

Company (IP), is 14 km to the north of Dolet Hills. Neither Sierra Club nor the state’s modeling 

included emissions from IP. The state asserted that emissions from this facility are represented 

by the background monitor data; however, the EPA does not agree that the background monitor 

data used adequately represents any potential concentration gradients that may occur in the area 

of concern from IP’s emissions. Based on the modeling provided by Sierra Club and LDEQ, 

industry modeling for siting a monitor, one of the higher areas with near modeled exceedances 

was to the south of the facility. When winds are out of the north and resulting in some of the 

highest values modeled around Dolet Hills, the IP source would be upwind and could contribute 

to concentration gradients around Dolet Hills and to the south of Dolet Hills. Coupling this with 

the proximity to Dolet Hills (approx. 14km), and size of IP emissions warrant consideration for 

explicit modeling, as suggested by Appendix W, because it is likely that the source causes 

concentration gradients that extend to area impacted by Dolet Hills with some of the higher 

modeled values that are near the standard. 

The grid receptor spacing by Sierra Club was retained by the state in their modeling analysis 

along with all associated elevations and processing information that could potentially impact the 

area of analysis where maximum SO2 concentrations are expected. The receptor network 

contained 21201 receptors (no graphical representation of the receptor grid was provided): 

- A 100-meter Cartesian receptor grid centered on Dolet Hills and extending out 5 km. 

- A 500-meter Cartesian receptor grid centered on Dolet Hills and extending out 10 

kilometers. 

- A 1,000-meter Cartesian receptor grid centered on Dolet Hills and extending out 50 

kilometers. 50 kilometers is the maximum distance accepted by USEPA for the use of the 

AERMOD dispersion model. 

- A flagpole height of 1.5 meters was used for all these receptors. 

This is a larger grid than we might normally recommend but this grid is acceptable for this 

analysis. Sierra Club modeling used a slightly elevated flagpole receptor height, but if this was 

corrected to EPA’s recommended height we would expect only a slight change in the modeled 
11

numbers and the area of exceedances and magnitude of the values would be basically the 

equivalent and not change our proposed action. 

Figure 2 shows the area surrounding Dolet Hills originally provided in the state’s monitoring 

siting report provided to the EPA showing the location of all minor and major sources of SO2 in 

DeSoto Parish. The state originally recommended that the area designated unclassifiable should 

be limited to the southeast quadrant of the parish bounded by United States Highway 84 on the 

north, United States Highway 171 on the west, and the parish boundary on the east and south. As 

discussed elsewhere, the state revised their recommendation that all of DeSoto Parish should be 

designated attainment/unclassifiable. EPA’s intended nonattainment designation area is the area 

within DeSoto Parish that lies within a rectangular area defined by UTM coordinates (See Figure 

1 above). The nonattainment area excludes portions of Red River Parish, Louisiana that fall 

within this UTM-based boundary. 

Figure 2: Dolet Hills Area of Analysis by the State 

Sierra Club’s elevations for stacks and receptors were obtained from National Elevation Dataset 

(NED) GeoTiff data. GeoTiff is a binary file that includes data descriptors and geo-referencing 

information necessary for extracting terrain elevations. The elevations were extracted from 1 arcsecond (30 meter) resolution NED files. The USEPA software program AERMAP v. 11103 was 

used for these tasks. 

Modeling Parameter: Source Characterization 

Sierra Club modeled constant exit flowrate and temperature based on 100% load. No 

consideration was given of facility operation at less than 100% load. Stack parameters such as 

exit flow rate and temperature are typically lower at less than full load, having the effect of 

reducing pollutant dispersion and increasing predicted air quality impacts. In addition, no 
12

consideration was given to building or structure downwash. Downwash effects typically increase 

predicted concentrations near the facility. The state identified International Paper located 14 km 

north of the Dolet Hills facility with annual emissions exceeding 1,300 tpy as the only other 

large nearby emission source. However, no sources other than Dolet Hills were included in the 

modeling performed by the Sierra Club or the state. 

Modeling Parameter: Emissions 

The EPA’s Modeling TAD notes that for the purposes of modeling to characterize air quality for 

use in designations, the recommended approach is to use the most recent 3 years of actual 

emissions data and concurrent meteorological data. However, the TAD does provide for the 

flexibility of using allowable emissions in the form of the most recently permitted, (referred to as 

PTE or allowable) emissions rate. 

The EPA believes that continuous emissions monitoring systems (CEMS) data provide 

acceptable historical emissions information when it is available, and that these data are available 

for many electric generating units. In the absence of CEMS data, the EPA’s Modeling TAD 

highly encourages the use of AERMOD’s hourly varying emissions keyword HOUREMIS, or 

through the use of AERMOD’s variable emissions factors keyword EMISFACT. When choosing 

one of these methods, the EPA believes that detailed throughput, operating schedules, and 

emissions information from the impacted source(s) should be used. 

In certain instances, states and other interested parties may find that it is more advantageous or 

simpler to use PTE rates as part of their modeling runs. Specifically, a facility may have recently 

adopted a new federally enforceable emissions limit, been subject to a federally enforceable 

consent decree, or implemented other federally enforceable mechanisms and control 

technologies to limit SO2 emissions to a level that indicates compliance with the NAAQS. These 

new limits or conditions may be used in the application of AERMOD. In these cases, the 

Modeling TAD notes that the existing SO2 emissions inventories used for permitting or SIP 

planning demonstrations should contain the necessary emissions information for designationsrelated modeling. In the event that these short-term emissions are not readily available, they may 

be calculated using the methodology in Table 8-1 of Appendix W to 40 CFR Part 51 titled, 

“Guideline on Air Quality Models.” 

 

As previously noted, the state included only Dolet Hills in its modeling but identified one other 

large emitter of SO2 within 20 km in the area of analysis. The associated annual actual SO2

emissions between 2012 and 2014 are summarized below. 

Table 2: Actual SO2 Emissions (2012 – 2014) from Facilities in the DeSoto Parish Area 

Company ID Facility Name SO2 Emissions (tons per year) 

2012 2013 2014 

CLECO Power LLC Dolet Hills 20,887 14,612 14,177 

International Paper Co. Mansfield Mill 1,569 1,296 1,557 

Total Emissions All Facilities 22,456 15,908 15,734 
13

Initial state modeling for the purpose of monitor siting used normalized hourly emissions and 

actual stack temperature and exit velocity from the CEMS for 2012-2014. Sierra Club modeling 

utilized hourly emissions data measured by the CEMS from CAMD (2012-2014) and constant 

stack temperature and exit velocity. The state’s revised modeling utilized the Sierra Club model 

inputs for emissions and stack parameters, but the EPA reiterates that the emissions from IP were 

not included in the modeling analysis. 

Modeling Parameter: Meteorology and Surface Characteristics 

The most recent 3 years of meteorological data (concurrent with the most recent 3 years of 

emissions data) should be used in designations efforts. As noted in the Modeling TAD, the 

selection of data should be based on spatial and climatological (temporal) representativeness. 

The representativeness of the data are based on: 1) the proximity of the meteorological 

monitoring site to the area under consideration, 2) the complexity of terrain, 3) the exposure of 

the meteorological site, and 4) the period of time during which data are collected. Sources of 

meteorological data include National Weather Service (NWS) stations, site-specific or onsite 

data, and other sources such as universities, Federal Aviation Administration (FAA), and 

military stations. 

For the Dolet Hills area of analysis, surface meteorology was obtained for Shreveport Regional 

Airport located near Dolet Hills. Integrated Surface Hourly (ISH) data for the 2012-2014 period 

were obtained from the National Climatic Data Center (NCDC). 

The state and Sierra Club used AERSURFACE version 13016 to develop surface roughness, 

albedo, and daytime Bowen ratio values in a region surrounding the meteorological data 

collection site. AERSURFACE was used to develop surface roughness in a one kilometer radius 

surrounding the data collection site. Bowen ratio and albedo was developed for a 10 kilometer by 

10 kilometer area centered on the meteorological data collection site. These micrometeorological 

data were processed for seasonal periods using 30-degree sectors. Seasonal moisture conditions 

were considered average with winter months having no continuous snow cover. 

Upper-air data are collected by a “weather balloon” that is released twice per day at selected 

locations. As the balloon is released, it rises through the atmosphere, and radios the data back to 

the surface. The measuring and transmitting device is known as either a radiosonde, or 

rawindsonde. Data collected and radioed back include: air pressure, height, temperature, dew 

point, wind speed, and wind direction. The upper air data were processed through AERMET 

Stage 1, which performs data extraction and quality control checks. 

For Dolet Hills, the concurrent 2012-2014 upper air data from twice-daily radiosonde 

measurements obtained at the most representative location were used. This location was the 

Shreveport, Louisiana measurement station. These data are in Forecast Systems Laboratory 

(FSL) format and were downloaded in ASCII text format from NOAA’s FSL website. All 

reporting levels were downloaded and processed with AERMET (v14134). 
14

Modeling Parameter: Geography and Terrain 

The UTM NAD83 coordinate system (Zone 15) was used for identifying the easting (x) and 

northing (y) coordinates of the modeled sources and receptors. Stack locations were obtained 

from facility permits and prior modeling files provided by the state regulatory agency. The stack 

locations were then verified using aerial photographs and confirmed with GIS. 

The facility was evaluated to determine if it should be modeled using the rural or urban 

dispersion coefficient option in AERMOD. A Geographic Information System (GIS) was used to 

determine whether rural or urban dispersion coefficients apply to a site. Based on the 

AERSURFACE analysis, it was concluded that the rural option would be used for the modeling 

summarized in this report. Please refer to Section 4.5.3 of the Sierra Club modeling report for a 

discussion of the AERSURFACE analysis. 

Modeling Parameter: Background Concentrations of SO2 

The Modeling TAD offers two mechanisms for characterizing background concentrations of SO2

that are ultimately added to the modeled design values: 1) a “first tier” approach, based on 

monitored design values, or 2) a temporally varying approach, based on the 99th percentile 

monitored concentrations by hour of day and season or month. For the Dolet Hills area of 

analysis, consistent with the background concentration identified by the Sierra Club in their 

analysis, the state chose the 99th percentile of the annual distribution of daily maximum 1-hour 

concentrations averaged across 2011-2013 for the Bossier Parish monitor – the lowest measured 

background concentration in the state. The background SO2 concentration was added to the 

modeled fourth-highest daily maximum 1-hour SO2 concentration. The background 

concentration for this area of analysis was determined by the state to be 31.4 micrograms per 

cubic meter (μg/m3), or 12.0 ppb,3 and that value was incorporated into the final AERMOD 

results. 

Summary of Modeling Results 

The AERMOD modeling parameters for the DeSoto Parish area of analysis are summarized 

below in table 3: 

Table 3: AERMOD Modeling Parameters for the DeSoto Parish Area of Analysis 

DeSoto Parish Area of Analysis 

AERMOD Version 15181 

Dispersion Characteristics Rural 

Modeled Sources 1 

Modeled Stacks 1 

                                                            

3

 The conversion factor for SO2 (at the standard conditions applied in the ambient SO2 reference method) is 1ppb 

SO2 = approximately 2.62μg/m3 SO2 at 25C and 1 atm.
15

Modeled Structures No 

Modeled Fence lines - 

Total receptors 21201 

Emissions Type Actual - CEM 

Emissions Years 2012-2014 

Meteorology Years 2012-2014 

Surface Meteorology Station Shreveport Regional Airport 

(Shreveport, LA) 

Upper Air Meteorology Station Shreveport, LA measurement 

station 

Methodology for Calculating 

Background SO2 Concentration 

99th percentile of the annual 

distribution of daily maximum 

1-hour concentrations averaged 

across 2011-2013 for Bossier 

Parish 

Calculated Background SO2

Concentration 12 ppb (31.4 μg/m3

) 

 

The results presented below in table 4 show the magnitude and geographic location of the 

highest predicted modeled concentration based on actual emissions. 

Table 4: Max 99th Percentile 1-Hr SO2 Conc.in DeSoto Parish Area Based on Actual Emissions 

Averaging 

Period 

Data 

Period 

Receptor Location SO2 Concentration 

(μg/m3) 

UTM 

Latitude 

UTM 

Longitude

Modeled 

(including 

background) 

NAAQS

LDEQ 

revised 

modeling 

99th Percentile 

1-Hour Avg. 2012-2014 Not provided

Not 

provided 194.5 196.5* 

Sierra 

Club 

modeling 

99th Percentile 

1-Hour Avg. 2012-2014 Not provided

Not 

provided 218.7 196.5* 

 

The state’s modeling4

 (with the LOWWIND3 non-default option) indicates that the predicted 

99th percentile 1-hour average concentration within the chosen modeling domain is 194.5 μg/m3, 

or 74.31 ppb. This modeled concentration included the background concentration of SO2. This 

predicted value is graphically represented along with all the other receptors below in Figure 3. 

Sierra Club December modeling predicted 99th percentile 1-hour average concentration within 

the chosen modeling domain is 218.7 μg/m3, or 83.55 ppb. This modeled concentration included 

                                                            

4

 State modeling based on Sierra Club files and not the state’s normalized emission modeling. 
16

the same background concentration of SO2. This predicted concentrations are graphically 

represented along with all other receptors with values above the NAAQS below in Figure 4. 

Figure 3: Maximum Predicted 99th Percentile 1-Hour SO2 Concentrations in the 

Dolet Hills Area of Analysis Based on Actual Emissions 

 (LDEQ’s modeling using Sierra Club’s inputs) 
17

Figure 4: Maximum Predicted 99th Percentile 1-Hour SO2 Concentrations in the 

Dolet Hills Area of Analysis Based on Actual Emissions (Sierra Club) 

As discussed previously, the state reran Sierra Club’s initial modeling factoring in a low wind 

non-default modification (beta option) to the model. The Sierra Club modeling provided a peak 

value of 218.7 μg/m3

, above the standard of 196.5 μg/m3. The state reran that modeling using the 

proposed LOWWIND3 option, resulting in a peak value of 194.5 μg/m3

, just below the standard 

(see Figure 4 above). As previously discussed, the EPA notes that the use of beta options, such as 

ADJ_U* and LOWWIND3, in AERMOD for any regulatory applications requires adherence 

with Appendix W, Section 3.2.2. This is further explained in the EPA’s December 10, 2015 

Memorandum titled, “Clarification on the Approval Process for Regulatory Application of the 

AERMOD Modeling System Beta Options.” Among other conditions, the use of beta options 

requires consultation with the appropriate EPA Regional Offices. Upon concurrence by the 
18

EPA’s Modeling Clearinghouse, EPA Regional Offices may approve the use of these beta 

options for regulatory applications as an alternative model. However, LDEQ performed air 

dispersion modeling intended to characterize air quality as a result of SO2 emissions from Dolet 

Hills without prior consultation with and approval from an EPA Regional Office, and therefore 

has not met the applicable regulatory requirements contained in Appendix W, Section 3.2.2. As a 

result, the EPA does not believe that the air quality modeling results obtained from the use of 

these beta options can be used as a reliable indicator of attainment status in the area around Dolet 

Hills until appropriate alternative model approval is granted or these beta options are 

promulgated as regulatory options in AERMOD through EPA rulemaking. 

The Sierra Club modeling, and the state’s revised modeling using LOWWIND3, only included 

constant stack velocity and temperature and did not include building downwash or the nearby 

International Paper causing some uncertainty in the modeling results. The lack of downwash and 

variable temperature/velocity, with the non-inclusion of IP, however, generally bias the results of 

Sierra Club’s modeling low. As a result, we believe that Sierra Club’s modeling provides 

sufficient information to determine that the area is not meeting the standard, and therefore we 

intend to designate it as nonattainment. 

Jurisdictional Boundaries: 

After the geographic area of analysis associated with the immediate area surrounding Dolet Hills, 

nearby sources which may potentially be contributing to elevated levels of SO2, and background 

concentration was determined, existing jurisdictional boundaries were considered for the purpose 

of informing our intended nonattainment area, specifically with respect to clearly defined legal 

boundaries. The EPA believes that while there are no clear jurisdictional boundaries that 

encompass our intended nonattainment area, UTM coordinates result in clearly defined 

boundaries. 

The state originally recommended an area in the Southeastern quadrant as unclassifiable and then 

revised that recommendation to attainment for all of DeSoto Parish. Based on our analysis and 

consideration of modeling results provided by Sierra Club and the state, as well as other nearby 

sources such as IP, the EPA intends to designate portions of DeSoto Parish as nonattainment. As 

discussed above when winds are from the north IP is a background source that could contribute 

significantly to some of the higher modeled values that are on the south side of Dolet Hills and 

very near the standard. Modeling results for monitor siting indicated the west side and south side 

were the two primary areas with high frequency of maximum values using normalized emissions. 

The EPA believes that the IP facility has reported emissions that are large enough such that if 

they were explicitly modeled in accordance with the Modeling TAD would likely be shown to 

contribute to the ambient concentrations that have already been modeled to show violations, or 

near violation, of the NAAQS. Inclusion of IP emissions may likely increase modeled values just 

below the standard to exceedance levels. Therefore, our intended area includes portions of 

DeSoto Parish that include the area of modeled exceedances and near exceedances as well as the 

IP facility because of its likely contribution to the modeled ambient concentrations resulting in 

additional potential NAAQS violations if IP were included in the modeling. 
19

The EPA believes that our intended nonattainment area, consisting of the area around Dolet Hills 

and including International Paper, is comprised of clearly defined boundaries, and we find these 

boundaries to be a suitably clear basis for defining our intended nonattainment area. 

Conclusion 

After careful evaluation of the state’s recommendation and supporting information, as well as all 

available relevant information, the EPA intends to designate the area around Dolet Hills in 

DeSoto Parish, Louisiana as nonattainment for the 2010 SO2 NAAQS. Specifically, the intended 

nonattainment area is comprised of the portion of DeSoto Parish bounded by the following UTM 

Coordinates in meters (NAD83 Datum, Zone 15): 

X Y 

441287 3541019

441287 3562019

450500 3562019

450500 3541019

The nonattainment area excludes the portion of Red River Parish, Louisiana that falls within the 

area bounded by the listed UTM coordinates. Figure 1 above graphically illustrates our intended 

nonattainment area. 

In its original submission, the state recommended that the area surrounding Dolet Hills, 

specifically the southeast quadrant of DeSoto Parish, be designated as unclassifiable based on a 

monitoring siting report. The state reran modeling using the input parameters provided by Sierra 

Club and additionally factored in a low wind speed modification. Based on this modeling, the 

state changed their recommended designation from unclassifiable to attainment. After careful 

review of the state’s assessment, supporting documentation, and all available data, the EPA does 

not agree with the state’s recommendation for the area and cannot rely upon the modeling 

provided by the state, and intends to designate the area as nonattainment. 

At this time, our intended designations for the state only apply to this area and the other area 

presented in this technical support document. Consistent with the conditions in the March 2, 

2015 consent decree, the EPA will evaluate and designate all remaining undesignated areas in 

Louisiana by either December 31, 2017, or December 31, 2020. 
AECOM Mansfield Mill SO2 Modeling Report Environment

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Appendix B

Modeling Protocol 

Submitted to LDEQ
AECOM 978.905.2100 tel

250 Apollo Drive 978.905.2101 fax

Chelmsford, MA 01824

J:\AQES\Projects\International Paper 6890\Mansfield, LA\500-

Deliverables\LDEQ Protocol Letter-final.docx

March 8, 2016

Ms. Vennetta Hayes

Louisiana Department of Environmental Quality

Air Permits

P.O. Box 4313

Baton Rouge, LA 70821-4313

Subject: Proposed Modeling Methodologies for SO2 DeSoto Parish, Louisiana Area 

Designations

Dear Ms. Hayes,

On February 11, 2016, the United States Environmental Protection Agency (EPA) Region 6 issued 

a letter to the Honorable John Bel Edwards, Governor of Louisiana. This letter was intended to 

inform Governor Edwards on the latest round of EPA’s area designations as they relate to the 1-

hour SO2 National Ambient Air Quality Standards (NAAQS). This first round of designations was

targeted based on the consent decree entered into by EPA and the Sierra Club which was the result 

of the March 2, 2015 court ruling (Sierra Club vs. McCarthy, No. 3-13-cv-3953). According to this 

ruling, the first round of designations must be made by EPA by July 2, 2016. This letter indicated 

that parts of DeSoto Parish in Louisiana (among other locations) were intended to be designated as 

non-attainment.

Attached to the letter was EPA’s technical support document (TSD) describing the analyses that 

were performed to define the boundary of the area designations. The non-attainment area 

proposed by EPA was extended much further to the north (see Figure 1 of the EPA TSD) compared 

to that proposed by Louisiana Department of Environmental Quality (LDEQ) in their November 17, 

2015 recommendations. LDEQ recommended that the non-attainment area for DeSoto Parish be 

limited to the southeast quadrant of the parish (shown in Figure 2 of EPA’s TSD). 

The primary (and only) source modeled to determine this area designation was the Dolet Hills 

Power Station. EPA’s proposed non-attainment area was extended approximately 10-15 kilometers 

to the north to include the International Paper’s (IP) Mansfield Mill (a much smaller SO2 emission 

source) even though the modeling presented by the Sierra Club and LDEQ indicated the highest 

modeled impacts were to the west of Dolet Hills Power Station. 

None of the technical analyses performed by EPA, the Sierra Club, or LDEQ included the IP 

Mansfield Mill. Based on the Sierra Club modeling (which only shows predicted impacts above the 

NAAQS to the west of the Dolet Hills Power Station), it is highly unlikely that IP Mansfield Mill’s 
AECOM

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2

modeled impacts would significantly overlap the modeled exceedances due to the Dolet Hills Power 

Station (i.e., modeled contribution less than the 1-hour SO2 interim Significant Impact Level (SIL) of 

7.9 g/m3).

Therefore, the intention of this letter is to inform the LDEQ on proposed modeling procedures that 

will differ from those outlined in EPA’s TSD provided with the February 11, 2016 area designation 

letter. IP proposes to perform additional modeling to determine the impact, if any, on the modeled

exceedances of the 1-hour SO2 NAAQS that are predicted in the vicinity of the Dolet Hills Power 

Station.

The modeling will be performed in accordance with the approaches outlined in the EPA’s TSD and 

utilized by the Sierra Club and LDEQ with the following exceptions to either refine the analysis or 

address potential deficiencies identified by EPA in their TSD:

1. All modeling will be conducted using DEFAULT model options.

2. Updates will be made to account for actual flow rates and/or temperatures in the hourly 

estimates of the Dolet Hills Power Station emissions and stack parameters.

3. Updates will be made to include building downwash for the Dolet Hills Power Station.

4. AERMET Version 15181 will be used in the updated modeling.

5. IP Mansfield Mill sources will be included using their allowable emission rates for all SO2

sources except Power Boiler #1 and #2 which will be modeled using representative actual 

maximum hourly emission rates. The representative actual maximum hourly emission rates

will be determined by using the 99th percentile (or greater) emission rate for each Power 

Boiler based on operations during the 2012-2014 period. Overall, this approach is 

conservative in that it utilizes a representative maximum hourly emission rate for every hour 

of the year as opposed to actual hourly emissions.

6. The IP Mansfield Mill will include building downwash.

7. The modeling will be conducted using one comprehensive receptor grid encompassing the 

area surrounding both facilities. The grid will extends out a minimum of 20 kilometers in all 

directions from each facility. The grid will be based on the following specifications:

a. 25-meter spacing around each facility’s ambient air boundary;

b. Beyond the ambient air boundary from each facility, 100-meter spaced receptors 

will be used out to 3-5 km depending on the direction from the facilities;

c. Beyond the 100-meter spaced receptors a 250-meter spaced grid will be used out 

and additional 4-8 kilometers from each facility depending on the direction; 

d. Beyond the 250-meter spaced receptors a 500-meter spaced grid will be used out 

and additional 5 kilometers; and 

e. Beyond the 500-meter spaced receptors a 250-meter spaced grid will be used out 

and additional 10 kilometers. 
AECOM

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8. Ambient background concentrations will be updated based on 2013-2015 data for the 

Shreveport Monitor. 2011-2013 was used as part of the TSD, however that data only 

represented 2013 as the monitor was shut down in 2011 and 2012. In addition, rather than 

conservatively adding the modeled design concentration with the monitored design 

concentration for this analysis, as a refinement, the ambient background will be combined 

with modeled concentrations on a seasonal hour-of-day basis in accordance with EPA 

guidance in their March 1, 2011 clarification memo1and as outlined in the SO2 Modeling 

Technical Analysis Document (TAD)2.

IP looks forward to receiving any comments that LDEQ has on these proposed modeling 

procedures. 

Yours sincerely,

Jeffrey Connors

Air Quality Meteorologist

jeffrey.connors@aecom.com

cc\ Tegan Treadaway (LDEQ)

Louis Derose (IP)

Chris Gann (IP)

Brian E Heim (IP)

Sheryl Watkins (AECOM)

 

1

http://www.epa.gov/ttn/scram/guidance/clarification/Additional_Clarifications_AppendixW_Hourly-NO2-NAAQS_FINAL_03-01-

2011.pdf

2 Available at: https://www3.epa.gov/airquality/sulfurdioxide/pdfs/SO2ModelingTAD.pdf
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Appendix C

Modeling Archive CD