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## SO 2 

## Air Dispersion Modeling Report for Independence

Steam

Electric Station

August 2015

ERM Project No. 0268066

www.erm.com

## SO 2 

## Air Dispersion Modeling Report for Independence

Steam

Electric Station

August, 2015

ERM Project No. 0268066

_____________________________________ Peter T. Belmonte

Partner

- in

- Charge

_____________________________________ Rich ard P. Hamel
Project Manager

Environmental Resources Management
One Beacon Street, 5 th Floor
Boston, MA 02108

T: 617

- 646

- 7800

F: 617

- 267

- 6447ii

TABLE OF CONTENTS

INTRODUCTION 1

- 1 1.0

PROJECT OVERVIEW 1

- 1 1.1

OVERVIEW OF METHODOL OGY 1

- 2 1.2

FACILITY DESCRIPTION AND REGULATORY SETTI NG 2

- 1 2.0

FACILIT Y LOCATION 2

- 1 2.1

SO 2 ATTAINMENT STATUS 2

- 1 2.2

SOURCE PARAMETERS AN D EMISSION RATES 2

- 4 2.3

AIR DISPERSION MODEL ING ANALYSIS 3

- 1 3.0

MODEL SELECTION AND APPLICATION 3

- 1 3.1

THE 1

- HOUR SO 2 NAAQS 3

- 1 3.2

METEOROLOGICAL DATA 3

- 1 3.3

RECEPTOR GRID 3

- 3 3.4

GOOD ENGINEERING PRA CTICE STACK HEIGHT A NALYSIS 3

- 4 3.5

AMBIENT SO 2 BACKGROUND DATA FOR CUMULATIVE MODELING 3

- 4 3.6

MODELING RESULTS 4

- 1 4.0

CONCLUSIONS 4

- 1 4.1

REFERENCES 5

- 1 5.0iii LIST OF TABLES

Table 2

- 1 Independence Station Point Sources

– Stack Parameters 2

- 5

Table 3

- 1 Characteristics of the Adams Field

– Little Rock Meteorological Data 3

- 2

Table 3

- 2 Seasonal Diurnal SO 2 Concentrations at Little Rock Monitor (  g/m 3 ) 3

- 5

Table 4

- 1 1

- hour SO 2 Modeling Results for Independence Station 4

- 1

LIST OF FIGURES

Figure 1

- 1 Independence Station Surroundings and Land Use 1

- 4

Figure 2

- 1 Independence Station Site Plan 2

- 2

Figure 2

- 2 Independence Station Local Topography 2

- 3

Figure 3

- 1 Relative Location of Facility, Airport, and Ambien t Monitor 3

- 6

Figure 3

- 2 Three

- year Wind Rose (2012

- 2014): Little Rock

– Adams Field 3

- 7

Figure 3

- 3 Near

- Field Model Receptors 3

- 8

Figure 3

- 4 Far

- Field Model Receptors 3

- 9

Figure 4

- 1 Independence Station 1

- hour SO 2 Impact Contours 4

- 2

LIST OF APPENDICES

APPENDIX A ELECTRONIC MODELING ARCHIVEERM 1

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INTRODUCTION 1.0

ERM Consulting & Engineering, Inc. (ERM), has prepared this report documenting that

maximum model

- predicted SO 2 impacts from Entergy Arkansas Inc.’s (Entergy) Independence Steam Electric Station (Independence) are in attainment with the 1

- hour Sulfur Dioxide (SO 2 ) National Ambient Air Quality Standard (NAAQS) and will fulfill the requirements of the EPA’s 1

- Hour SO 2 Data Requirements Rule (DRR) . This analysis shows that the ambient air quality in the vicinity of Independence, currently undesignated for the 1

- hour SO 2 NAAQS, is within the standard and should be identified as “attainment” in the next cycle of designations.

This modeling report describes the modeling methodology that was used to evaluate potential impacts of SO 2 emissions from Independence on ambient air quality. Copies of the modeling files are provided in Appendix A, the Electronic Modeling Archive.

Project Overview 1.1

Unlike previous NAAQS attainment demonstrations, EPA has proposed to make 1

- hour

SO 2 NAAQS attainment determinations using ambient ai r monitoring data and/or air dispersion modeling. In situations where air modeling is used to make this determination, the approach described in EPA’s proposed “Modeling Technical Assistance Document” (TAD) 1 , which sets forth a significantly different tec hnical approach compared to conventional regulatory modeling prescribed by 40 CFR Part 51, Appendix W (EPA’s Guideline on Air Quality Models ) could be used. This approach

would also meet the requirements of the DRR

.

EPA distinguishes the approaches described in the SO 2 Modeling TAD to “reflect a view that designations are intended to address current actual air quality (i.e., modeling

simulates a monitor ), and thus are unlike attainment plan modeling, which must provide assurances that attainment will occur.” EPA’s proposed approach would utilize several distinctive technical approaches, including but not limited to the following:

 Simulating actual emissions and exhaust conditions (e.g., temperature and flowrate) on an hourly basis reflecting actual operations for a specified historical time period;

 Representing actual stack heights, irrespective of the GEP regulations;

 Limiting modeled ambient air receptors to locations where monitoring could actually take place by excluding waterways, roadways, ra ilways, restricted access property, and other locations that would conventionally be considered “ambient air” for regulatory and permitting purposes;

1 http://epa.gov/oaqps001/sulfurdioxide/pdfs/SO2ModelingTAD.pdfERM 1

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 Simulating a three

- year period of meteorological and background monitoring data,

concurrent with the actu al operating conditions and emissions, to meet EPA’s objective that “modeling simulates monitoring” in this context.

ERM performed a modeling analysis evaluating the impacts on ambient air quality

from SO 2 emissions at Independence. As discussed in this report, ERM’s approach to the modeling analysis used those refinements directly addressed in the proposed rule, i.e. the use of actual hourly emissions, actual stack heights, and seasonal diurnal

ambient bac kground concentrations.

As shown in this modeling report, SO 2 impacts from Independence emission sources,

when combined with ambient air concentrations taken from a representative nearby monitor, are below the 1

- hour SO 2 NAAQS.

Th is first section of this report describes the modeling methodology that was followed

. Section 2 provides a description of the facility and the emissions included in the modeling

. Model selection and the methodology used in the modeling are described in

Section 3

. The modeling results are presented in Section 4. References are provided in

Section 5.

Overview of M ethodology 1.2

ERM’s assessments were conducted in a manner consistent with United States Environmental Protection Agency ( EPA ) air quality regulations and modelin g guidelines that are generally adopted by Arkansas Department of Environmental Quality (A DEQ ) , including the following:

 Guideline on Air Quality Models

– 40 CFR Part 51, Appendix W, Revised November 9,

2005.

 AERMOD Implementation Guide , Revised March 1 9, 2009;

 “SO 2 NAAQS Designations Modeling Technical Assistance Document (Draft),”

December 2013 ;

 “SO 2 NAAQS Designations Monitoring Technical Assistance Document (Draft),”

December 2013 ;

 “Data Requirements Rule for the 2010 1

- Hour Sulfur Dioxide (SO 2 ) P rimary National Ambient Air Quality Standard (NAAQS),” Pre

- publication final rule, ( submitted to the Federal Register on August 10, 2015, FRL

- 9928

- 18

- OAR ) ; and

 “Guidance for 1

- hour SO 2 Nonattainment Area SIP Submissions,” April 23, 2014.

The steps that were under taken by ERM to conduct the air dispersion modeling analyses are summarized below:ERM 1

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 Compile d information on the parameters and characteristics for all sources of SO 2 emissions at Independence including the main EGU’s

, the auxiliary boiler, the emergency diesel generator, and the fire pump engine ;

 Develop ed a comprehensive receptor grid to capture the maximum off

- site impacts

from Independence sources using AERMAP (v.11103)

.

 Obtained ambient background concentration dat a for SO 2 from nearby monitors to represent sources not explicitly included in the modeling runs;

 Developed 3 years (2012

- 2014) of meteorological data using surface observations from Adams Field in Little Rock, AR with upper air data from North Little Rock Airport using the most recent version (v.15181) of AERMET, the meteorological data processor for AERMOD, and its two preprocessors: AERSURFACE (v.13016) and AERMINUTE (v. 14337 ).

 Conducted an air dispersion modeling analysis using the most recent version o f EPA’s regulatory dispersion model, AERMOD (v.15181 ) and 3 years of actual

emissions data from Independence emissions s ources , as well as other major sources

of SO 2 emissions in the region, consistent with the methodology described in the SO 2 Data Require ments Rule and SO 2 Modeling TAD.

 Summarized the results and compared them with the 1

- hour SO 2 NAAQS to
determine a recommended attainment designation for the vicinity of Independence.ERM 1

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Figure 1

- 1 Independence Station Surroundings and Land UseERM 2

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FACILITY DESCRIPTION AND REGU LATORY SETTING 2.0

Facility Location 2.1

The Independence Steam Electric Station is located in the town of Newark

, Arkansas

, in Independence County

. The station is located about 2.5 mile s southeast of downtown

Newark

. The si te is access ed by Arkansas State Route 69

. The station is approximate ly

8 2 miles nor theast of Little Rock, Arkansas and 84 mil es west

- northwest of Memphis,

Tennessee

. App rox imate site coordinates are 35.678 o North Latitude, 91.408 o West Longitude. The Universal Transverse Mercator ( “ UTM ” ) coordinates of the facility are

644,087 Easting and 3

, 949,438 N orthing ( using North American Datum of 1983

- NAD83) in UTM Zone 15

. The base elevation of the facility is 235’ (71.521 m) above sea

level. A full scale site plan of the power block area of Independence is shown in Figure 2.1, and Figure 2.2 shows the site location marked on a United States Geological Survey ( “ U SGS ” ) 7.5

- minute topographic map.

SO 2 Attainment Status 2.2

In July 2013, EPA issued a rule designating 29 counties or partial counties as non

attainment for 1

- hour SO 2 . However, the vast majority of the country was not designated by EPA at that time due to the lack of monitors, or poor siting of existing monitors, for the purpose of capturing source based maximum ambient SO 2 concentrations. None of the counties surrounding Independence, including Independence

, the county in which Independence is located, have been designated as

attainment or non

- attainment for the 1

- hour SO 2 NAAQS.ERM 2

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Figure 2

- 1 Independence Station Site PlanERM 2

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Figure 2

- 2 Independence Station Local TopographyERM 2

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Source Parameters and Emission Rates 2.3

For this 1

- hour SO 2 NAAQS modeling demonstration , all sources o f SO 2 at the f acility were included in the modeling. Per the 1

- hour SO 2 Data Requirements Rule and SO 2 Modeling TAD, the most recent 3 years of actual emissions data were used where available, and the actual stack height s of all sources were used in the modeling

. The following provides a description of all Independence SO 2 emission sources and how they were represented in the model

. Table 2

- 1 summarize s the characteristics of the

emissions sources that were included in the modeling. The actual emissions data used in the modeling are described below :

 Units No. 1 and No. 2 (Source ID: SN01 and SN02)

. There are two boilers in operation at the Independence Station, Unit 1 and Unit 2. Units 1 and 2 are
vented to a common, dual

- flue stack. For the se main units, three years (2012

- 2014 ) of actual hourly emissions, stack temperature, and exhaust flow rate data were input into the model. Th is emissions data w as provided by Entergy from prior submittals to the EPA’s Clean Air Markets Database , w hile temperature and exhaust flow rates were provided by Entergy from the facility CEM system

. As per the 1

- hour SO 2 Data Requirements Rule, the actual 1000 ft. height of the main stack was represented in each case. The two Units at the facility were modeled as separate sources, each emitting from their own flue. This is a conservative representation because it neglects potentially enhanced buoyancy from a combined plume from both flues.

 Auxiliary Boiler (Source ID: SN05)

. The auxiliary boiler was also modeled using

actua l hourly emissions data. For this source , however, exhaust temperature and velocity were not avail able, so for all hours the exit temperature and velocity

were set to the values located in the ADEQ source regist ration tables for the auxiliary boiler.

 Emergency D iesel Generator (Source ID: SN20 ) and Emergency Fire Pump Engine (Source ID: SN21 ) . The two emergency engines at the facility both have horizontal exhaust releases. This is represented in the modeling by setting the exit velocity of each source to 0.001 m/s to simulate the lack of vertical

momentum out of the stack. Emissions data were only avai lable on a month by

month total emission basis for each engine . To convert that data into an emission rate for modeling, for each engine the total annual emissions for each year was determined and the highest annual total selected. That total was then divi ded by 52 to represent that the engines are tested once per week during the year. The resulting emission rate was then used as the lb/hr emission rate in the modeling. Based on information provided b y facility staff , the emergency generator is

tested weekl y on Wednesdays, while the fire pump is tested on Friday evenings. To simulate this standard practice, the emergency generator was set in theERM 2

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modeling using the HRDOW7 emission factor (i.e., variable by hour of day and 7 days per week) to emit during an 8 hour period on Wednesdays from 8 AM to 4 PM, and the fire pump was set to operate on Friday’s from 4 PM until Midnight. While this significantly overestimates the total emissions of the emergency engines , because the form of the 1

- hour SO 2 standard only considers the hour with the highest concentration each day, at least 7 of these hours are “dropped” and thus only one hour worth of emission is potentially included in the maximum daily impacts.

Data supporting the actual emissions used fo r the 5 sources included in the modeling are provided in the spreadsheets ISES _Hourly Actual Emissions 2012

- 2014 .xlsx , ISES Aux Boiler Data 010112 to 123114 .xlsx, and ISES Em Gen Hours and

Emissions 2012

- 2014 .xlsx included in Appendix A: The Electronic Mod eling

Archive.

Table 2

- 1 Independence Station Point Sources

– Stack Parameters

Description Model

Source Stack Height Exit Temperature Exit Velocity Stack

Diameter
(ft) (m) (F) (K) (ft/sec) (m/s) (ft.) (m)

Unit 1 Boiler 1 SN01 1000 304.80

--- --- --- --- 25.7 7.83

Unit 2 Boiler 1 SN02 1000 304.80

--- --- --- --- 25.7 7.83

Auxiliary Boiler SN05 15 4.57 475 519.26 65.0 19.81 3.0 0.91

Emergency Diesel Engine SN20 1 4 4.27 963 790.54

---- 0.001 2 0.8 0.25

Emergency Fire Pump SN22 14 4.27 700 644.26

---- 0.001 2 0.4 0.13

1. For the 2 main boilers, exit temperature and exit velocity varied on an hourly basis based on actual emissions

data.

2. Emergency Diesel Engine and Emergency Fire Pump stack s are horizontal, so modeled exit velocity was 0.001 m/s for both.ERM 3

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AIR DISPERSION MODEL ING ANALYSIS 3.0

ERM conducted the modeling analysis for Independence to quantify ambient impacts of

SO 2 relative to the 1

- hour NAAQS following the proposed approach described in the

SO 2 Modeling TAD

.

Model Selection and A pplication 3.1

The latest version of USEPA ’s AERMOD mo del (v. 15181 ) was used for predicting ambient impacts for 1

- hour SO 2

. Re gulatory default options were used in the analysis

. Model predicted impacts from Independence were combined with those of other large

sources in the area and an ambient background concentration to represent emissions not explicitly modeled and compared to the 1

- hour SO 2 NAAQS to determine the recommended attainment status of the area in the vicinity of the facility

.

The 1

- hour SO 2 NAAQS 3.2

This study focuses on the maximum model

- predi cted 1

- hour SO 2 impacts of Independence and compares them to the 1

- hour SO 2 NAAQS. The new standard came into effect in August, 2010. The form of the standard is the 99 th percentile of the 3

- year average 1

- hour daily maximum concentration, and the standard was set to 75 ppb (196.5  g/m 3 )

.

Meteorological Data 3.3

Guidance for regulatory air quality modeling recommends the use of one year of on

- site meteorological data or five years of representative off

- site meteorological data

. The SO 2 Modeling TAD however, specifies that 3 years of meteorological data concurrent to the actual emissions data being input into the model be used. Since on

- site data are not

available for the Independence site, meteorological data available from the Nation al Weather Service (NWS) w ere used in this analysis.

Three years (2012

- 2014) of surface observations from the NWS tower at Adams Field Airport in Little Rock, AR (WBAN No. 13963) and concurrent upper air data from North Little Rock Municipal Airport in North Little Rock, AR (WBAN No. 03952) were processed with the most recent version of AERMET (v.15181) the meteorolo gical preprocessor for AERMOD, along with the two pre

- processors to AERMET: AERSURFACE (v.13016) and AERMINUTE (v. 14337 ). AERMET was applied to create the two meteorological data files required for input to AERMOD

.

AERMET requires specification of site characteristics including surface roughness (z

o ), albedo (r), and Bowen ratio (B

o ). These parameters were developed according to the guidance provided by EPA in the AERMOD Implementation Guide (AIG ) (EPA, 2008a) using AERSURFACE. The area within 1 km of t he meteorological tower at Adams FieldERM 3

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was broken into 12 sectors of 30 degrees each to analyze the surface characteristics in each 30 deg ree arc around the tower. AERMET uses the surface characteristics in the

sector from which the wind approaches the tow er as part of the meteorological data processing for each hour.

In AERSURFACE, the various land cover categories are linked to a set of seasonal surface characteristics. As such, AERSURFACE requires specification of the seasonal category for each month of the year. The following five seasonal categories are offered by AERSURFACE:

1. Midsummer with lush vegetation;

2. Autumn with unharvested cropland;

3. Late autumn after frost and harvest, or winter with no snow;

4. Winter with continuous snow on ground; and

5. Trans itional spring with partial green coverage or short annuals.

The AERS URFACE run was performed using the seasonal temporal resolution option. The default seasonal distribution was used: December, January, and February were categorized as winter with no sno w, March, April, and May as spring, June, July, and August as summer, and September, October, a nd November as fall. The precipitation was assumed to be average over the 3

- year period

.

Additionally, 1

- minute ASOS wind data, collected at the Adams Field me teorological tower, were processed using the AERMINUTE pre

- processor for AERMET. The data

characteristics of Adams Field are shown in Table 3

- 1. Figure 3

- 1 shows the relative

location of Adams Field and Independence Station, and Figure 3

- 2 shows the 3

- year wind rose for Adams Field.

Table 3

- 1 Characteristics of the Adams Field

– Little Rock Meteorological Data

Distance from Independence Station 80.1 miles

Average Wind Speed 3.42 m/s

Percent Calm Hours 1.10%

Data Completeness 99.95%

All files associated with the meteorological data processing are included in Appendix A: The Electronic Modeling Archive.ERM 3

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Receptor Grid 3.4

A comprehensive Cartesian receptor grid extending out to approximately 20 kilometers (km) from Independence was used in the AERMOD modeling analysis to assess maximum ground

- level 1

- hour SO 2 concentrations. The Modeling TAD states that the receptor grid mu st be sufficient to determine ambient air quality in the vicinity of the source being studied. The 20

- kilometer receptor grid is more than sufficient to resolve

the maximum 1

- hour SO 2 impacts in the area around Independence , and it clearly

illustrates decreasing SO 2 concentration gradients in relation to the plant.

The Cartesian receptor grid consist ed of the following receptor spacing :

 50

- meter spacing along the facility fence line ;

 100

- meter spacing extending from the fence line to 5 k ilometers ;

 50 0

- mete r spac ing extending from 5 to 10 k ilometers ; and

 1

, 00 0

- meter spacing extending from 10 to 2 0 k ilometers

.

The above receptor data was used without modification in the modeling. Per the 1

- hour

SO 2 Modeling TAD, a number of receptors located over the White River could be excluded from the modeling domain because ambient monitors could not reasonably be placed at these locations, but these receptors were retained in this analysis as a measure

of conservatism.

Terrain elevations from National Elevation Data (“NED”) from USGS were processed using the most recent version of AERMAP (v.11103) to develop the receptor terrain elevations required by AERMOD. NED data files contain profiles of terrain ele vations, which in conjunction with receptor locations are used to generate receptor height scales. The height scale is the terrain elevation in the vicinity of a receptor that has the greatest influence on dispersion at that location and is used for model computations in complex

terrain areas. The near

- field (within 5 kilometers) and far

- field (full grid) receptor grids are shown in Figures 3

- 3 and 3

- 4, respectively.ERM 3

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Good Engineering Practice Stack Height Analysis 3.5

As described in the SO 2 Modeling TAD, when modeling actual emissions from a facility

in order to evaluate the attainment status of an area with regard to the 1

- hour SO 2 NAAQS, the full height of all stacks is allowed in the modeling regardless of their GEP Formula Heights. Therefore, no GEP stack height analysis is necessary for this study.

E ach source was model ed with its actual stack height in the analysis

, and downwash effects were considered through the use of EPA’s buildi ng profile input program (BPIP)

.

Ambient SO 2 Background Data for Cumulative Modeling 3.6

It was assumed, after initial modeling, that impacts from Independence sources would

exceed the 1

- hour SO 2 Significant Impact Level (SIL) of 7.9  g/m 3 . As a result, ambient background data from the closest, most representative SO 2 monitor to Independence was downloaded from the ADEQ ambient monitoring website to represent other

sources of SO 2 in the area . A review of the data showed that the most representative monitor for use in the modeling is located in Little Rock (Monitor ID# 05

- 119

- 0007).

EPA guid ance allows simulation of background values that vary by season and hour of day that could simulate a lower value than the 99th percentile. The modeling was performed with a set of seasonal diurnal values developed using the methodology

described in the U SEPA March 1st, 2011 Clarification Memorandum for 1

- hour NO 2 Modeling. Though this memorandum primarily addresses NO 2 modeling, page 20 describes the process for developing seasonal diurnal background values for SO 2 as well.

The location of the selected ambient monitor relative to Independence is shown in Figure 3

- 1. The seasonal diurnal values used are shown in Table 3

- 2

.ERM 3

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Table 3

- 2 Seasonal Diurnal SO 2 Concentrations at Little Rock Monitor (  g/m 3 )

Hour 1 Winter Spring Summer Fall

1 6.89 5.67 4.80 5.50

2 7.85 5.32 4.28 6.19

3 7.33 6.19 4.45 6.02

4 6.89 5.76 4.19 4.71

5 8.55 4.97 4.19 5.15

6 9.60 4.80 5.41 5.85

7 9.60 6.28 5.50 6.63

8 8.99 5.24 6.11 6.54

9 7.50 6.46 7.68 7.85

10 8.38 8.20 7.42 9.07

11 9.16 8.46 9.95 8.20

12 10.73 15.09 10.38 9.34

13 9.69 11.08 10.91 11.17

14 10.56 9.34 9.86 9.51

15 10.03 8.20 13.18 9.95

16 9.42 7.94 9.34 10.47

17 7.15 9.86 11.08 9.16

18 7.50 7.42 9.69 7.24

19 9.25 6.37 9.86 6.98

20 12.30 6.54 8.73 5.93

21 9.07 6.02 6.19 6.28

22 6.11 8.99 5.76 5.67

23 6.46 7.07 5.67 5.85

24 7.24 6.81 5.41 6.11

1. Hours in AERMOD are defined as hour

- ending. i.e., Hour 1 is the period from midnight through 1 AM, etc.ERM 3

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Figure 3

- 1 Relative Location of Facility, Airport, and Ambient MonitorERM 3

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Figure 3

- 2 Three

- year Wind R ose (2012

- 2014 ): Little Rock

– Adams FieldERM 3

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Figure 3

- 3 Near

- Field Model ReceptorsERM 3

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Figure 3

- 4 F ar

- Field Model ReceptorsERM 4

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MODEL ING RESULTS 4.0

The modeling results are shown in Table 4

- 1 below. The modeled design value represents the modeled 3

- year average of the 99th percentile, maximum daily 1

- hour average impact for Independence, which is then added to the ambient background concentration and the total impact compared to the NAAQS to demonstrate attainment.

Contours of the predicted impacts, as well as the location of the maximum predicted impact of 131.3  g/m 3 , are shown in Figure 4

- 1. The table shows that model predicted impacts from Independence, when modeled using the most recent three years of actual emissions data and added to a representative ambient background concentration, are

below the level of the 1

- hour SO 2 NAAQS.

Table 4

- 1 1

- hour SO 2 Modeling Results for Independence Station

Source Independence
Only Independence and

Background 1

- hr. SO 2

NAAQS Below

NAAQS?

Independence Station 122.2 131.3 196.5 Yes

Conclusions 4.1

The air dispersion modeling performed as described in this report shows that the SO 2 emissions from Independence Station result in maximum predicted impacts below

the 1

- hour SO 2 National Ambient Air Quality Standard. T herefore

, an attainment designation for Independence County is recommended.ERM 4

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Figure 4

- 1 Independence Station 1

- hour SO 2 Impact ContoursERM 5

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REFERENCES 5.0

U.S. Environmental Protection Agency

. (USEPA 2005) Guideline on Air Quality Models (GAQM, 40CFR Appendix W), November, 2005

U.S. Environmental Protection Agency

. (USEPA 2009) AERMOD Implementation Guide, AERMOD Implementation Workgroup. March 19, 2009.

U.S. Environmental Protection Agency

. ( USEPA 2011) USEPA memo entitled “Additional Clarification Regarding Application of Appendix W Modeling Guidance

for the 1

- hour NO 2 National Ambient Air Quality Standard”, USEPA , Office of Air Quality Planning and Standards , Raleigh, NC

. March 1, 2011

.

U.S. Environmental P rotection Agency. (USEPA 2014) “SO 2 NAAQS Designations Modeling Technical Assistance Do cument (Draft),” December 2013 ;

U.S. Environmental Protection Agency. (USEPA 2014) “SO 2 NAAQS Designations Monitoring Technical Assistance Document (Draft),” Decembe r 2013 ;

U.S. Environmental Protection Agency. (USEPA 2014) “Data Requirements Rule for the

2010 1

- Hour Sulfur Dioxide (SO 2 ) Primary National Ambient Air Quality Standard (NAAQS),” Final rule submitted August 10, 2015 ; and

U.S. Environmental Protection Agency. (USEPA 2014) “Guidance for 1

- hour SO 2 Nonattainment Area SIP Submissions,” April 23, 2014.

## Appendix A

Electronic Modeling Archive