1

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Technical Support Document (TSD)

Florida

Area Designations For the 

2010 SO2 Primary National Ambient Air Quality Standard

Summary

Pursuant to section 107(d) of the Clean Air Act (CAA), EPA must designate areas as either 

“nonattainment,” “attainment,” or “unclassifiable” for the 2010 1-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 poor air quality in a nearby area that does not meet the 

NAAQS. Table 1 below identifies the counties or portions of counties (or areas of Indian Country) in 

Florida that EPA is initially designating “nonattainment” based on monitored violations. EPA is not yet 

prepared to designate other areas in Florida.

Table 1. Nonattainment Area Designations for Florida

Area 

Florida Recommended 

Designation of Areas/Counties

EPA’s Designation of 

Areas/Counties

Hillsborough County Area

 Hillsborough County (partial)

Nonattainment Nonattainment

Nassau County Area

 Nassau County (partial)

Nonattainment Nonattainment

Background

On June 2, 2010, EPA revised the primary SO2 NAAQS (75 FR 35520, June 22, 2010) by establishing a 

new 1-hour standard at a level of 75 parts per billion (ppb) which is met at an ambient air quality 

monitoring site when the 3-year average of the annual 99th percentile of the daily maximum 1-hour 

average concentration is less than or equal to 75 ppb, as determined in accordance with Appendix T of 

40 CFR part 50. 40 CFR 50.17(a)-(b). EPA has determined that this is the level necessary to provide 

protection of 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 Agency is revoking the two prior primary standards of 140 ppb evaluated over 24-

hours, and 30 ppb evaluated over an entire year because the standards will not add additional public 

health protection given a 1-hour standard at 75 ppb. Accordingly, EPA is not designating areas in this 

process on the basis of either of these two prior primary standards. Similarly, the secondary standard for 

SO2 has not been revised, so EPA is not designating areas in this process on the basis of the secondary 

standard.
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EPA’s SO2 Designation Approach

Section 107(d) of the CAA provides that not later than 1 year after promulgation of a new or revised 

NAAQS, state Governors may submit their recommendations for designations and boundaries to EPA. 

This deadline was in June 2011. Section 107(d) also requires EPA to provide a notification to states of 

no less than 120-days prior to promulgating an initial area designation that is a modification of a state’s 

recommendation. EPA has reviewed the State’s recommendations and has notified the Governor

through a letter signed by the Regional Administrator of any intended modifications. While language in 

section 107 specifically addresses states, we followed the same process for the tribal governments, 

pursuant to section 301(d) of the CAA and Tribal Authority Rule (40 CFR Part 49). Therefore, we are 

designating tribal areas, in consultation with the tribal governments, on the same schedule as state 

designations. Florida does not have any tribal areas affected by this designation. If a state or tribal 

government does not submit designation recommendations, EPA is promulgating the designations that it 

deems appropriate. If a state or tribal government disagrees with EPA’s intended area designations as 

released on February 7, 2013, it had an opportunity to demonstrate why any proposed modification was 

inappropriate. 

Designations guidance was issued by EPA through a March 24, 2011, memorandum from Stephen D. 

Page, Director, U.S. EPA, Office of Air Quality Planning and Standards, to Air Division Directors, U.S. 

EPA Regions I-X. This memorandum identifies factors EPA intends to evaluate in determining 

boundaries for areas designated nonattainment. These 5 factors include: 1) air quality data; 2) 

emissions and emissions-related data (location of sources and potential contribution to ambient SO2

concentrations); 3) meteorology (weather/transport patterns); 4) geography/topography (mountain 

ranges or other air basin boundaries); and 5) jurisdictional boundaries (e.g., counties, air districts, preexisting nonattainment areas, reservations), among any other information deemed relevant to 

establishing appropriate area designations and boundaries for the 1-hour SO2 NAAQS.

The March 24, 2011, memo recommended that area boundaries be defaulted to the county boundary 

unless additional information justifies a larger or smaller boundary than that of the county. EPA 

believes it is appropriate to evaluate each potential area on a case-by-case basis, and to recognize that 

area-specific analyses conducted by states, tribal governments and/or EPA may support a different 

boundary than a default county boundary.

In this TSD, EPA discusses its review and technical analysis of the recommendations submitted by the 

state for designations of the 1-hour SO2 standard and any modifications from these recommendations.

Definition of important terms used in this document:

1) Designated “nonattainment” area – an area which EPA has determined, based on a state 

recommendation and/or on the technical analysis included in this document, has violated the 2010 SO2

NAAQS, based on the most recent three years of air quality monitoring data, or contributes to a 

violation in a nearby area. 

2) Recommended nonattainment area – an area that a state or tribal government has recommended to 

EPA to be designated as nonattainment.
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3) Violating monitor – an ambient air monitor meeting all methods, quality assurance and citing criteria 

and requirements whose valid design value exceeds 75 ppb, as described in Appendix T of 40 CFR part 

50.

4) 2010 SO2 NAAQS - 75 ppb, national ambient air quality standard for SO2 promulgated in 2010. 

Based on the 3-year average of the 99th percentile of the annual distribution of daily maximum 1-hour 

average concentrations

5) Design Value – a statistic that describes the air quality status of a given area relative to the level of 

the NAAQS.
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Nonattainment Designations

Technical Analysis for Hillsborough County Area

Introduction 

This technical analysis for Hillsborough County Area identifies the partial county with a monitor that 

violates the 2010 SO2 NAAQS based on 2009-2011 data, and evaluates nearby counties for 

contributions to SO2 concentrations in the area. EPA has evaluated this county and nearby counties 

based on the weight of evidence of the factors recommended in the March 24, 2011, issued EPA 

guidance. 

Figure 1 is a map of the area analyzed showing the locations and design values of air quality monitors in 

the area, and the counties surrounding any violating air quality monitors.

Figure 1. Hillsborough Nonattainment Area

In June 2011, Florida Department of Environmental Protection (FDEP) Secretary Herschel T. Vinyard 

Jr. recommended that a partial boundary in Hillsborough County be designated as “nonattainment” for 

the 2010 SO2 NAAQS based on monitored air quality data from 2008-2010. The State of Florida 

recommendation is for a nonattainment area boundary encompassing the area that, based upon air 

dispersion modeling, may be experiencing violations of the standard caused by an identified source.
5

Based on EPA’s technical analysis described below, EPA is initially designating a portion of 

Hillsborough County, Florida as nonattainment for the 2010 SO2 NAAQS as part of the Hillsborough 

County nonattainment area, based upon currently available information. This county is listed above in 

Table 1. EPA is not yet prepared to designate other areas in Florida, apart from the Nassau County Area 

discussed later.

Detailed Assessment

Air Quality Data 

This factor considers the SO2 air quality monitoring data, including the design values (in ppb) calculated 

for all air quality monitors in Hillsborough County and the surrounding area based on data for the 2009-

2011 period. 

Secretary Vinyard’s recommendation was based on data from a Federal Equivalent Method (FEM) 

monitor located in the State (Florida Nonattainment Designation Recommendation Letter, June 13, 

2011), in accordance with 40 CFR Part 53.

The 2011 SO2 NAAQS design values for all monitors in the Hillsborough Area and surrounding area are 

shown in Table 2.

Table 2. Air Quality Data for Nonattainment Designations in Hillsborough County, FL

County

State

Recommended

Nonattainment?

Monitor Name Monitor Air Quality

System ID Monitor Location

SO2 Design Value,

2009-2011

(ppb)

Hillsborough 

County Yes East Bay 

(Gibsonton)

12-057-0109 27.856389,

-82.383667

103

No E.G. Simmons 

Park

12-057-0081 27.740032,

-82.465145

22

No Coast Guard 

Station – Davis 

Island

12-057-1035 27.928056

-82.454722

43

No Sydney 12-057-3002 27.965650,

-82.2304

15

Hillsborough County shows a violation of the 2010 SO2 NAAQS. Therefore, some area in Hillsborough 

County and possibly additional areas in surrounding counties must be designated nonattainment. The 

violating monitor (12-057-0109) near Gibsonton is located approximately 1 kilometer to the southeast of 

the Mosaic Riverview phosphate fertilizer plant, a major source of SO2 emissions. The primary 

emissions units at this facility are three sulfuric acid plants. The absence of a violating monitor alone is 

not a sufficient reason to eliminate nearby counties as candidates for inclusion in a nonattainment area. 

Each area has been evaluated based on the weight of evidence of the five factors and other relevant 

information. 
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Emissions and Emissions-Related Data

Evidence of SO2 emissions sources in the vicinity of a violating monitor is an important factor for 

determining whether a nearby area is contributing to a monitored violation. For this factor, EPA 

evaluated county level emissions data for SO2 and any growth in SO2 emitting activities since the date 

represented by those emissions data.

Emissions 

EPA recognizes that there may be important new information on emissions levels for the period after 

2008, and would consider more recent information if available. Florida did not provide updated 

emissions information, therefore EPA relied on the 2008 National Emissions Inventory (NEI) emissions 

data (NEI08V3). 

Table 3 shows total emissions of SO2 (given in tons per year (tpy)) for violating and potentially 

contributing counties in and around the Hillsborough nonattainment area, including sources emitting 

greater than 100 tpy of SO2 according to the 2008 NEI. The county that contains the Hillsborough

nonattainment area for the 2010 SO2 NAAQS is shown in bold. 

Table 3. Annual SO2 Emissions (NEI08V3)

County Facility >100 tpy 

(EIS or State Facility ID)

Facility Emissions 

(tpy)

Total County SO2

Emissions

(tpy)

Hillsborough County, FL

TAMPA ELECTRIC 

COMPANY - Big Bend 9,615 

18512

CF INDUSTRIES, INC., 

PLANT CITY PHOS 3,430 

MOSAIC FERTILIZER, LLC 3,037 

ENVIROFOCUS 

TECHNOLOGIES, LLC 1,108 

Tampa International Airport 119 

Figure 2 shows the above facility locations in relation to the violating monitor.
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Figure 2: Facility Locations in the Hillsborough County Area 

Emissions Controls

The emissions data used by EPA in this technical analysis and provided in Table 3 represent emissions 

levels taking into account any control strategies implemented on stationary sources in the Hillsborough 

County Area up to and including the year 2008. EPA has not received any additional information on 

emissions reductions resulting from federally enforceable controls put into place after 2008. 

Meteorology (weather/transport patterns)

Evidence of source-receptor relationships between specific emissions sources and high SO2 values at 

violating monitors is another important factor in determining the appropriate contributing areas and the 

appropriate extent of the nonattainment area boundary. For this factor, EPA considered recent hourly 

meteorological data from the National Weather Service (NWS) site nearest to the violating monitor to 

determine which wind vectors were associated with 1-hour SO2 exceedances. For the Hillsborough 

County Area, the meteorological data used in this analysis is for 2009-2011 from the Tampa 

International Airport (ID # 722110-12842). Figure 2 shows a map of the SO2 monitor location, 

meteorological data location, and the major emissions sources in the area. The Tampa International 
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Airport is approximately 19 kilometer west of the violating monitor. The primary SO2 emissions source 

is the Mosaic Riverview facility, which is located less than one kilometer from the violating monitor.

Figure 3 shows a wind rose of the hours exceeding the 1-hr SO2 NAAQS (75 ppb) at the violating 

monitor. The wind rose was developed using wind data from the Tampa International Airport. 

Figure 3 shows that the majority of the exceeding hours have winds blowing from the northwest with 

moderate to high wind speeds. As can be seen in Figure 2, the Mosaic Riverview facility is located less 

than 1 km to the northwest of the monitor. No other major sources are located near the violating 

monitor in the northwest direction. Therefore, the Mosaic Riverview facility is likely the major 

contributor to the monitor’s design value.

FDEP performed an in-depth analysis of wind direction data to identify the wind directions associated 

with elevated SO2 monitored concentrations. This information is based on “on-site” wind data collected 

Figure 3. Wind Rose of 2009-2011 hours exceeding the 1-hr 

SO2 NAAQS at the violating monitor.

WRPLOT View - Lakes Environmental Software

WIND ROSE PLOT:

Hillsborough County, Florida - Tampa Intl Airport

2009-2011 Exceedance Hours - Monitor AQS ID# 12-057-0109

COMMENTS: COMPANY NAME:

U.S. EPA Region 4

MODELER:

Rick Gillam, 

APTMD/APB/AQMTS

DATE:

8/3/2012

PROJECT NO.:

NORTH

SOUTH

WEST EAST

5%

10%

15%

20%

25%

WIND SPEED 

(m/s)

 >= 11.1

 8.8 - 11.1

 5.7 - 8.8

 3.6 - 5.7

 2.1 - 3.6

 0.5 - 2.1

Calms: 0.00%

TOTAL COUNT:

54 hrs.

CALM WINDS:

0.00%

DATA PERIOD:

Start Date: 3/1/2009 - 23:00

End Date: 12/28/2011 - 01:00

AVG. WIND SPEED:

5.78 m/s

DISPLAY:

 Wind Speed

Direction (blowing from)
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at the violating SO2 monitor location and is provided in the “Meteorology” section of Appendix A of 

this TSD. The result of this analysis agrees with EPA’s analysis and indicates that winds blow from the 

northwest during times of high SO2 concentrations recorded at the violating monitor. This analysis 

shows that the Mosaic Riverview Facility is upwind of the monitor and is the most likely contributor to 

the monitor’s design value. This hypothesis was further evaluated by the State using dispersion 

modeling, although we are not at this time prepared to rely upon such modeling for this initial 

designation based on monitoring data. See the discussion in the “Modeling Analysis” section for further 

information about the modeling. 

Geography/Topography (mountain ranges or other air basin boundaries)

The Hillsborough County Area does not have any geographical or topographical barriers significantly 

limiting air-pollution transport within its air shed. Therefore, this factor did not play a significant role in 

determining the nonattainment boundary.

Jurisdictional Boundaries 

Once EPA identified the general areas that the Agency anticipated would be included in the 

nonattainment area, EPA then considered existing jurisdictional boundaries for the purposes of 

providing a clearly defined legal boundary and to help identify the areas appropriate for carrying out the 

air quality planning and enforcement functions for nonattainment areas. With regard to the 2010 SO2

NAAQS, EPA believes that the appropriate jurisdictional boundaries to be considered to include

counties, air districts, pre-existing nonattainment areas, reservations, among any other information 

deemed relevant to establishing appropriate area designations and boundaries for the 1-hour SO2

NAAQS.

No area in Hillsborough County has been or is currently nonattainment for a prior SO2 NAAQS, so EPA 

had no boundary related to a previous nonattainment designation to consider for this area. Additionally, 

this area does not include Indian Country. Therefore, this factor did not play a significant role in 

determining the nonattainment boundary.

Modeling Analysis for Nonattainment Area Boundaries

The violating monitor is located within Hillsborough County, roughly in the center of the county, 

approximately one kilometer to the southeast of the Mosaic Riverview phosphate fertilizer plant. The

violating area associated with the primary source of SO2 at this monitor is well within the county

boundary. The State’s recommended nonattainment boundary encompasses this violating area as 

informed by air dispersion modeling. Although EPA is not prepared at this time to rely upon modeling 

for the initial nonattainment designations based on monitoring, we note that the State’s modeling-based 

boundary recommendation is consistent with the boundary supported by the wind rose analysis 

discussed above. See Appendix A of this document for modeling results for nonattainment area 

boundaries. FDEP used air dispersion modeling to help delineate the boundary of the recommended 

nonattainment area. In completing this modeling, the Department generally followed the guidance

provided in the March 24, 2011, EPA memorandum, “Area Designations for the 2010 Revised Primary 

Sulfur Dioxide National Ambient Air Quality Standards.”
10

Specifically, the State’s recommendation letter provides modeling results to inform a nonattainment area 

boundary for this area. The AERMOD model results were used to determine the areal extent with which 

the Mosaic Riverview facility would be potentially violating the standard. The recommended 

nonattainment area encompasses the receptors having modeled violations of the ambient standard 

associated with the Mosaic Riverview facility (see Figure 4). Florida used its model results in an 

exacting manner to describe the recommended nonattainment boundaries. The nonattainment area is 

defined as the area where the model predicts that the SO2 concentration (using the five-year average of 

the 4th high value as the metric) is greater than the ambient SO2 standard. A polygon with six vertices is 

used to define the areal extent of the nonattainment area (see the discussion and figure below). 

Figure 4. Aerial photo with nonattainment area boundary.

As indicated above, the June 13, 2011, Florida submittal recommends a nonattainment area boundary 

encompassing the area that, based upon air dispersion modeling, is experiencing violations of the SO2

standard caused by the identified source. The State’s recommended nonattainment boundary is 

described by a polygon encompassing the predicted area having a design value greater than the 1-hour 

ambient SO2 standard of 75 ppb (see Figure 4). The following aerial photo below shows the bounds of 

the area having modeled concentrations greater than the ambient air quality standard. The annotated 

polygon (white line) outlines the area recommended for nonattainment classification. The red shaded 

area outlines the modeled area greater than the ambient standard. The whited-out area describes the 

property boundary of the Mosaic Riverview facility, with buildings and structures in blue. The Area 

includes the location of the violating monitor. In summary, the State’s recommendation letter provides 
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the following vertices of the polygon using Universal Transverse Mercator (UTM) coordinates in UTM 

zone 17 with datum NAD83 (see Table 4) :

Table 4. Universal Transverse Mercator (UTM) Coordinates

Vertices UTM Easting (m) UTM Northing (m)

1 358581 3076066

2 355673 3079275

3 360300 3086380

4 366850 3086692

5 368364 3083760

6 365708 3079121

Other Relevant Information

EPA did not receive additional information relevant to establishing a nonattainment area boundary for 

this Area.

Conclusion

After considering the factors described above, EPA finds that it is appropriate to agree with the State of 

Florida’s partial boundary recommendation for the Hillsborough County Nonattainment Area. EPA’s 

conclusion is premised on that fact that the air quality monitor in Hillsborough County shows a violation 

of the 2010 SO2 NAAQS, based on 2009-2011 air quality data. Additionally, the boundary captures the 

violating monitor, the source contributing to the violation, and encompasses the appropriate initial area 

that does not meet (or that contributes to ambient air quality in a nearby area that does not meet) the 

2010 SO2 NAAQS. Areas and sources that we are not yet prepared to conclude are contributing to the 

monitored violation are not included in this initial nonattainment area. In a subsequent round of 

designations we will further address such areas and sources and make final designations decisions for 

areas that are not currently included in the nonattainment area designation addressed in this TSD.

Technical analysis for Nassau County

Introduction 

This technical analysis for Nassau County identifies the partial county with a monitor that violates the 

2010 SO2 NAAQS based on 2009-2011 data, and evaluates nearby counties for contributions to SO2

concentrations in the area. EPA has evaluated this county and nearby counties based on the weight of 

evidence of the factors recommended in the March 24, 2011, issued EPA guidance. 

Figure 5 is a map of the area analyzed showing the locations and design values of air quality monitors in 

the area, and the counties surrounding any violating air quality monitors.
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Figure 5. Nassau Nonattainment Area

In June 2011, FDEP Secretary Herschel T. Vinyard Jr. recommended that most of the State, as a whole, 

be designated “unclassifiable” or “unclassifiable/attainment” for the 75 ppb 1-hour SO2 standard. This 

was intended to include the area surrounding the monitoring site in Nassau County. The State submitted 

a revised recommendation letter on November 28, 2011. In that letter, FDEP recommended that a 

portion of Nassau County also be designated “nonattainment.” The State of Florida recommendation is 

for a nonattainment area boundary encompassing the area that, based upon air dispersion modeling, may 

be experiencing violations of the standard caused by the identified source.

Based on EPA’s technical analysis described below, EPA is designating a portion of Nassau County, 

Florida as nonattainment for the 2010 SO2 NAAQS as part of the Nassau County nonattainment area, 

based upon currently available information. This county is listed above in Table 1. EPA is not prepared 

to designate other areas in Florida, apart from the Hillsborough County Area discussed previously.

Detailed Assessment

Air Quality Data 

This factor considers the SO2 air quality monitoring data, including the design values (in ppb) calculated 

for all air quality monitors in Nassau County and the surrounding area based on data for the 2009-2011 

period. 
13

Florida’s recommendation was based on data from a FEM monitor located in the State (Florida 

Nonattainment Designation Recommendation Letter, November 28, 2011), in accordance with 40 CFR 

Part 53.

The 2011 SO2 NAAQS design values for all monitors in the Nassau County and surrounding area are 

shown in Table 5.

Table 5. Air Quality Data for Nonattainment Designations in Nassau County, Florida

County

State

Recommended

Nonattainment?

Monitor Name Monitor Air Quality

System ID Monitor Location

SO2 Design Value,

2009-2011

(ppb)

Nassau County, 

FL Yes FBHWWTP 12-089-0005 30.3583, 

-81.4633 129

Nassau County shows a violation of the 2010 SO2 NAAQS. Therefore, some area in this county and 

possibly additional areas in surrounding counties must be designated nonattainment. The absence of a 

violating monitor alone is not a sufficient reason to eliminate nearby counties as candidates for inclusion 

in a nonattainment area. Each area has been evaluated based on the weight of evidence of the five 

factors and other relevant information. 

The violating monitor (12-089-0005) in Fernandina Beach is located less than one kilometer to the 

southeast of the Rayonier Performance Fibers plant, a major source of SO2. No other SO2 monitors in 

the northeast Florida area have recorded violations of the ambient standard.

Emissions and Emissions-Related Data

Evidence of SO2 emissions sources in the vicinity of a violating monitor is an important factor for 

determining whether a nearby area is contributing to a monitored violation. For this factor, EPA 

evaluated county level emissions data for SO2 and any growth in SO2 emitting activities since the date 

represented by those emissions data.

Emissions 

EPA recognizes that there may be important new information on emissions levels for the period after 

2008, and would consider more recent information if available. Florida did not provide updated 

emissions information, therefore EPA relied on the 2008 NEI emissions data (NEI08V3). 

Table 6 shows total emissions of SO2 (given in tpy) for violating and potentially contributing counties in 

and around Nassau County, including sources emitting greater than 100 tpy of SO2 according to the 

2008 NEI. The County that contains all or part of the Nassau County nonattainment area for the 2010 

SO2 NAAQS is shown in bold. 
14

Table 6. Annual SO2 Emissions (NEI08V3)

County Facility >100 tpy 

(EIS or State Facility ID) Facility Emissions (tpy)

Total County SO2

Emissions

(tpy)

Nassau County, FL

SMURFIT-STONE 

CONTAINER 

CORPORATION

 4,340 

5,288 RAYONIER 

PERFORMANCE FIBERS 

LLC

 887 

Figure 6: Facility Locations in the Nassau County Area 

Emissions Controls

The emissions data used by EPA in this technical analysis and provided in Table 6 represent emissions 

levels taking into account any control strategies implemented on stationary sources in Nassau County up 

to and including the year 2008. EPA has not received any additional information on emissions 

reductions resulting from federally enforceable controls put into place after 2008.
15

Meteorology (weather/transport patterns)

Evidence of source-receptor relationships between specific emissions sources and high SO2 values at 

violating monitors is another important factor in determining the appropriate contributing areas and the 

appropriate extent of the nonattainment area boundary. For this factor, EPA considered recent hourly 

meteorological data from the NWS site nearest to the violating monitor to determine which wind vectors 

were associated with 1-hour SO2 exceedances. For the Nassau Area, the meteorological data used in this 

analysis is for 2009-2011 from the Fernandina Beach site (ID # 997347-99999). Figure 6 shows a map 

of the SO2 monitor location, meteorological data location, and the major emissions sources in the area. 

The Fernandina Beach site is less that one kilometer northeast of the violating monitor. The primary SO2

emissions sources nearby are the Rayonier Performance Fibers facility, located approximately one

kilometer northwest from the violating monitor, and the Smurfit-Stone Container Corporation facility, 

located approximately 2.5 kilometer north-northeast from the violating monitor.

Figure 7 shows a wind rose of the hours exceeding the 1-hr SO2 NAAQS (75 ppb) at the violating 

monitor. The wind rose was developed using wind data from the Fernandina Beach site. 

Figure 7. Wind Rose of 2009-2011 hours exceeding the 1-hr 

SO2 NAAQS at the violating monitor.

WRPLOT View - Lakes Environmental Software

WIND ROSE PLOT:

Nassau County, Florida - Fernandina Beach NWS Site

2009-2011 Exceedance Hours - Monitor AQS ID# 12-089-0005

COMMENTS: COMPANY NAME:

U.S. EPA Region 4

MODELER:

Rick Gillam, 

APTMD/APB/AQMTS

DATE:

8/3/2012

PROJECT NO.:

NORTH

SOUTH

WEST EAST

5%

10%

15%

20%

25%

WIND SPEED 

(m/s)

 >= 11.1

 8.8 - 11.1

 5.7 - 8.8

 3.6 - 5.7

 2.1 - 3.6

 0.5 - 2.1

Calms: 0.00%

TOTAL COUNT:

47 hrs.

CALM WINDS:

0.00%

DATA PERIOD:

Start Date: 3/2/2009 - 08:00

End Date: 11/10/2011 - 07:00

AVG. WIND SPEED:

3.55 m/s

DISPLAY:

 Wind Speed

Direction (blowing from)
16

Figure 7 shows that the majority of the exceeding hours have winds blowing from the west-northwest 

direction with low to moderate wind speeds. As can be seen in Figure 6, the Rayonier Performance 

Fibers facility is located approximately 1 kilometer northwest of the monitor. No other major sources 

are located near the violating monitor in the west-northwest direction. Therefore, the Rayonier 

Performance Fibers facility is likely the major contributor to the violating monitor’s design value.

FDEP performed an in-depth analysis of wind direction data to identify the wind directions associated 

with elevated SO2 monitored concentrations. This information is provided in the “Meteorology” section 

of Appendix B of this TSD. The results of this analysis agree with EPA’s analysis above which 

indicates that winds blow from the northwest during times of high SO2 concentrations at the violating 

monitor. This analysis shows that the Rayonier Facility is upwind of the monitor and is the most likely 

contributor to the monitor’s design value. Although we are not yet prepared to rely upon modeling for 

these initial designations based on monitored violations, this hypothesis was further evaluated by the 

State using dispersion modeling. See the discussion in the “Modeling Analysis” section for further 

information about the modeling. 

Geography/Topography (mountain ranges or other air basin boundaries)

Nassau County does not have any geographical or topographical barriers significantly limiting airpollution transport within its air shed. Therefore, this factor did not play a significant role in 

determining the nonattainment boundary.

Jurisdictional Boundaries 

Once EPA identified the general areas that the Agency anticipated would be included in the 

nonattainment area, EPA then considered existing jurisdictional boundaries for the purposes of 

providing a clearly defined legal boundary and to help identify the areas appropriate for carrying out the 

air quality planning and enforcement functions for nonattainment areas. With regard to the 2010 SO2

NAAQS, EPA has determined that the appropriate jurisdictional boundaries to be considered to include

counties, air districts, pre-existing nonattainment areas, reservations, among any other information 

deemed relevant to establishing appropriate area designations and boundaries for the 1-hour SO2

NAAQS.

No area in Nassau County has been or is currently designated nonattainment for a prior SO2 NAAQS, so 

EPA had no boundary related to a previous nonattainment designation to consider for this area. 

Additionally, this area does not include Indian Country. Therefore, this factor did not play a significant 

role in determining the nonattainment boundary.

Modeling Analysis for Nonattainment Area Boundaries

The violating monitor is located in the northeastern part of Nassau County, less than 1 kilometer to the 

southeast of the Rayonier Performance Fibers plant. The violating area associated with the primary 

source of SO2 at this monitor is well within the county boundary. The State’s recommended 

nonattainment boundary encompasses this violating monitor as informed by air dispersion modeling.

Although EPA is not prepared at this time to rely upon modeling for the initial nonattainment 

designations based on monitoring, we note that the State’s modeling-based boundary recommendation is 
17

consistent with the boundary supported by the wind rose analysis discussed above. See Appendix B of 

this document for modeling results for nonattainment area boundaries. FDEP used air dispersion 

modeling to help delineate the boundary of the recommended nonattainment area. In completing this 

modeling, the Department generally followed the guidance provided in the March 24, 2011, EPA 

memorandum, “Area Designations for the 2010 Revised Primary Sulfur Dioxide National Ambient Air 

Quality Standards.”

Specifically, the State’s updated recommendation letter dated November 28, 2011, (in Appendix B) 

provides modeling results to inform a nonattainment area boundary for this area. The AERMOD model 

results were used to determine the areal extent with which the Rayonier facility would be potentially 

violating the standard. The recommended nonattainment area encompasses the receptors having 

modeled violations of the ambient standard associated with the Rayonier facility. Florida used its model 

results in an exacting manner to describe the recommended nonattainment boundaries. The 

nonattainment area is defined as the area where the model predicts that the SO2 concentration (using the 

five-year average of the 4th high value as the metric) is greater than the ambient SO2 standard. A 

circular area is used to define the areal extent of the nonattainment area (see the discussion and figure 

below). 

Figure 8. Aerial photo with nonattainment area boundary.

As indicated above, the November 28, 2011, Florida submittal recommends a nonattainment area 

boundary encompassing the area that, based upon air dispersion modeling, is experiencing violations of 

the SO2 standard caused by the identified source. The State’s recommended nonattainment boundary is 

centered on the violating monitor and encompasses the area having a modeled violation of the ambient 

standard associated with the Rayonier facility. The State’s recommendation letter (in Appendix B) 

provides a circular boundary of the area recommended for nonattainment classification, with the center 

being the location of the violating ambient monitor and the radius being 2.4 kilometers. Figure 8

illustrates an aerial photo of the modeled nonattainment area boundary.
18

Other Relevant Information

EPA did not receive additional information relevant to establishing a nonattainment area boundary for 

this Area.

Conclusion

After considering the factors described above, EPA finds that it is appropriate to agree with the State of 

Florida’s partial boundary recommendation for the Nassau County Nonattainment Area. EPA’s 

conclusion is premised on that fact that the air quality monitor in Nassau County shows a violation of 

the 2010 SO2 NAAQS, based on 2009-2011 air quality data. Additionally, the boundary captures the 

violating monitor, the source contributing to the violation, and encompasses the appropriate initial area 

that does not meet (or that contributes to ambient air quality in a nearby area that does not meet) the 

2010 SO2 NAAQS. Areas and sources that we are not yet prepared to conclude are contributing to the 

monitored violation are not included in this initial nonattainment area. In a subsequent round of 

designations we will further address such areas and sources and make final designations decisions for 

areas that are not currently included in the nonattainment area designation addressed in this TSD.
19

Appendix A

Modeling Results Used to Inform Florida’s Recommended Area Boundaries

Hillsborough County Area Modeling Discussion (Appendix 2 of the 6/13/11 submittal)

Meteorology

A review of the monitoring data in relation to the wind direction at the time of maximum concentrations 

revealed that all recorded occurrences of SO2 above the level of the standard (75 ppb) were associated 

with winds coming from the Mosaic Riverview facility. The following aerial photo shows the direction 

of the Mosaic Riverview facility from the SO2 monitor. The distance from the primary SO2 sources 

(three sulfuric acid plants) to the monitor is 1 kilometer, with the direction of the entire facility ranging 

from 295oto 350o. The following tables list each of the hours in which a concentration was greater than 

the ambient SO2 standard (75 ppb) along with its associated wind direction. The wind direction data 

come from the wind instrument located at the monitoring site (wind data from the nearby Simmons Park 

monitoring site are substituted when data at the Gibsonton site are missing). The tables show that for 

some hours of high SO2 concentration the wind appears to be coming from a direction of about 56o. 

There are no SO2 sources from that direction, so the department reviewed the wind direction data for 

regional consistency. A review of these data shows that winds measured at other wind instruments in the 

area during these hours are consistent with a wind flow from the Mosaic Riverview facility. The wind 

direction data from the nearby Simmons Park site, located to the south of the Gibsonton monitor, are 

shown as a truer representation of the winds during these hours. Florida has not identified the reason 

why the Gibsonton wind instrument displays this behavior; however, it appears to be confined to the 

period from November 19, 2009, through February 17, 2010. Both before and after this period, SO2

concentrations remain near zero when the winds are out of this direction. 
20

SO2 Concentration and Associated Wind Direction (2008) (for hours greater than 75 ppb)
21

SO2 Concentration and Associated Wind Direction (2009) (for hours greater than 75 ppb)
22

SO2 Concentration and Associated Wind Direction (2010) (for hours greater than 75 ppb)

Air Dispersion Modeling

Florida used air dispersion modeling to help delineate the boundary of the State’s recommended

nonattainment area. In completing this modeling, Florida generally followed the guidance provided in 

the March 24, 2011, EPA memorandum, “Area Designations for the 2010 Revised Primary Sulfur 

Dioxide National Ambient Air Quality Standards.”

a) Model Selection – The department used the AERMOD modeling system.

a. AERMOD ver11103

b. AERMAP ver11103

c. AERMET ver06341

d. AERSURFACE ver08009

b) Modeling Domain – The focus of the nonattainment designation is on the monitor having the

violation. As noted above, wind data at the monitoring site indicate that all of the monitored high

concentrations (greater than the standard of 75 ppb) occur within a small wind direction sector that 

implicates the nearby Mosaic Riverview phosphate processing facility. Modeling of this source alone 

suggests that the predicated concentrations at the location of the monitor are almost completely 

explained by this single source. As a result, the modeling domain is centered on the Mosaic Riverview 

facility, which is located only 1000 meters from the monitoring location and the domain extends to a 15 

by 15 kilometer area around this facility.
23

c) Determining the Sources to Model – Because the Mosaic Riverside facility is the overwhelming

source of the monitored violation, it is the only source that Florida modeled for the purpose of informing 

the extent of the recommended nonattainment area. Florida recognizes that other SO2 sources in the

multi-county area could interact with the Mosaic facility for certain wind directions. Florida believes for 

the purpose of simply determining the initial area of nonattainment encompassing the violating monitor, 

it is sufficient to focus on the Mosaic Riverside facility. 

d) Receptor Grid – The receptor grid follows EPA’s March 2011 guidance: a nested grid with 50 meter 

spacing within one kilometer of the source, 100 meter spacing from one to two kilometers, 250 meters

from two to ten kilometers, and 500 kilometers outside of ten kilometers.

e) Source Inputs – Maximum allowable short-term limits on SO2 emissions or potential-to-emit levels 

were used for all sources. Stack and emission information were obtained from the Florida’s Air 

Resource Management System, Title V operating permits, and previous air construction permit 

applications. These data were reviewed by Mosaic, resulting in changes in refinement of the inputs 

related to geographic location of buildings and stacks. Where stack heights are less than good 

engineering practices (GEP), building downwash effects are included. No stacks at this facility exceed 

GEP limits. The ground surface characteristic of the area is rural as determined through land-use data 

consistent with the guidance.

f) Meteorological Data – Five years (2005-2009) of meteorological data from the National Weather

Service site at Tampa International Airport were used in this analysis. These data were processed 

through AERMET version 06341. The Tampa airport is located approximately 20 kilometer from the 

Mosaic facility, also along Tampa Bay. These data are deemed representative of the area in which 

Mosaic Riverview is located.

g) Background Concentration – The background concentration at the Gibsonton monitor was determined

based on the 99th percentile maximum daily 1-hour value on hours that were not impacted by the 

Mosaic Riverview facility. A 90-degree sector of wind directions centered on the Mosaic facility was 

excluded from the calculation to avoid double counting. The 99th percentile of the remaining 

concentrations associated with winds not from the direction of the Mosaic facility was calculated for 

each year and averaged. Based on this calculation, the background concentration is 25.8 ppb.

Modeling Results

The AERMOD model results were used to determine the areal extent with which this facility would be

potentially violating the standard. The State’s recommended nonattainment area encompasses the 

receptors having modeled violations of the ambient standard associated with the Mosaic Riverview 

facility. A review of the modeled impact at the location of the monitor provides an indication of the 

general performance of the model in describing the SO2 concentrations. The table below compares the 

model results with those at the monitor.
24

Year Modeled 

Maximum at 

Monitor 

Location (ppb)

Actual 1st High 

Maximum 1 hour 

value at Monitor 

(ppb)

Modeled 4th High at 

Monitor Location 

(ppb)

Actual 4th High 

(99th Percentile) at 

Monitor (ppb)

2005 163.0 151 133.5 135

2006 166.7 130 130.5 96

2007 163.3 143 137.6 126

2008 187.3 189 140.1 123

2009 153.7 136 130.1 104

These results indicate that the model is performing very well in replicating the SO2 concentration at the

monitoring location, and that the Mosaic Riverview facility explains virtually all of the elevated

concentrations that occur at this monitor. The design value concentrations in the area due to the Mosaic 

Riverview facility show that there are potentially higher concentrations in other locations. 

The maximum modeled design values associated with the Mosaic facility for 2005-2009 are as follows.

Year Date (MMDDHH) 4

th High Concentration (ppb) 

2005 010411 506.7

2006 031211 494.8

2007 120811 486.7

2008 090110 462.6

2009 022617 442.1

5-Year Average 478.5

It should be noted that the location of the design value concentration is on the Mosaic plant property.

Because the model performance is very good, the department has used the model results in an exacting

manner to describe the State’s recommended nonattainment boundaries. The State’s recommended 

nonattainment area is defined as the area where the model predicts that the SO2 concentration (using the 

five-year average of the 4th high value as the metric) is greater than the ambient SO2 standard. A 

polygon with six vertices is used to define the areal extent of the nonattainment area. The following 

aerial photo below shows the bounds of the area having modeled concentrations greater than the ambient 

air quality standard. The annotated polygon (white line) outlines the State’s recommended area for 

nonattainment classification. The red shaded area outlines the modeled area greater than the ambient 

standard. The whited-out area describes the property boundary of the Mosaic Riverview facility, with 

buildings and structures in blue.
25
26

Appendix B

Nassau County Area Modeling Discussion (Appendix of the 11/28/11 submittal)

Meteorology

A review of the monitoring data in relation to the wind direction at the time of maximum concentrations 

revealed that all monitored occurrences of SO2 above the level of the standard (75 ppb) were associated 

with winds coming from the Rayonier facility. The following aerial photo shows the direction of the 

Rayonier facility from the SO2 monitor. The distance from the facility to the monitor is 1 kilometer, with 

the direction of the entire facility ranging from 290oto 320o. The following tables list all of the hours in 

which a concentration was greater than the ambient SO2 standard (75 ppb) along with its associated 

wind direction. The wind direction data come from the wind instrument located at the monitoring site. 

When the winds come from the direction of the nearby Rock Tenn pulp mill, the monitor typically 

registers single digit SO2 concentrations with highest value in the upper 30’s ppb. It is clear that the 

Rayonier facility is contributing to the violation.
27

SO2 Concentration and Associated Wind Direction (2008) (for hours greater than 75 ppb)

SO2 Concentration and Associated Wind Direction (2009) (for hours greater than 75 ppb)
28

SO2 Concentration and Associated Wind Direction (2010) (for hours greater than 75 ppb)
29

Air Dispersion Modeling 

Florida used air dispersion modeling to help delineate the boundary of the State’s recommended 

nonattainment area. In completing this modeling, Florida generally followed the guidance provided in 

the March 24, 2011, EPA memorandum, “Area Designations for the 2010 Revised Primary Sulfur 

Dioxide National Ambient Air Quality Standards.” 

a) Model Selection – The department used the AERMOD modeling system. 

a. AERMOD ver11103 

b. AERMAP ver11103 

c. AERMET ver11059 

d. AERMINUTE ver11059 

e. AERSURFACE ver08009 

b) Modeling Domain – The focus of the nonattainment designation is on the monitor having the 

violation. As noted above, wind data at the monitoring site indicate that all of the monitored high 

concentrations (greater than the standard of 75 ppb) occur within a small wind direction sector that 

implicates the nearby Rayonier facility. As a result, the modeling domain is centered on the Rayonier 

facility, which is located only 1 kilometer from the monitoring location and the domain extends to a 10 

by 10 kilometer area around this facility. 

c) Determining the Sources to Model – Because the Rayonier facility is the overwhelming source for the 

violation, this is the only source modeled for the purpose of determining the extent of the initial 

nonattainment area. 

d) Receptor Grid – The receptor grid used follows the March 2011 EPA guidance. A nested grid with 

50 meter spacing within one kilometer of the source, 100 meter spacing from one to two kilometers, and 

250 meters from two to ten kilometers. 

e) Source Inputs – Maximum allowable short-term limits on SO2 emissions or potential to emit levels 

were used for all sources. Stack and emission information were obtained from the department’s Air 

Resource Management System, Title V operating permit, and previous air construction permit 

applications. These data were reviewed by Rayonier to verify the correct geographic location of 

buildings and stacks. Where stack heights are less than GEP, building downwash effects are included. 

No stacks at this facility exceed GEP limits. The Rayonier facility is rural as determined through landuse data consistent with the guidance. 

f) Meteorological Data – Five years (2006-2010) of meteorological data from the NWS site at 

Jacksonville International Airport were used in this analysis. These data were processed through 

AERMET version 11059, using 1-minute data from the same site processed through AERMINUTE 

version 11059. The Jacksonville airport is located approximately 28.5 kilometers to the south of the 

violating monitor. 

g) Background concentration – The background concentration at the Fernandina Beach monitor was 

determined based on the 99th percentile maximum daily 1-hour value on hours that were not impacted 

by the Rayonier facility. A 90-degree sector of wind directions centered on the Rayonier facility was 
30

excluded from the calculation to avoid contribution from the Rayonier facility. The 99th percentile of 

the remaining concentrations associated with winds not from the direction of the Rayonier facility were 

calculated for each year and averaged. Based on this calculation, the background concentration is 26.0 

ppb. 

Modeling Results 

The AERMOD model results were used to determine the areal extent to which this facility would be 

potentially violating the standard. The State’s recommended nonattainment area is centered on the 

violating monitor and encompasses the area having a modeled violation of the ambient standard 

associated with the Rayonier facility. 

The maximum modeled design values associated with the Rayonier facility for the 2006 – 2010 are as 

follows.

Year Date (MMDDHH) 4

th High Concentration (ppb) 

2006 082909 230.7

2007 081709 267.0

2008 072214 274.7

2009 072812 276.6

2010 071812 284.5

5-Year Average 266.7

The aerial photo below shows the bounds of the area having modeled concentrations greater than the 

ambient air quality standard. The red annotation circle outlines the area recommended for 

nonattainment classification, with the center being the location of the violating ambient monitor and the 

radius being 2.4 kilometers. Inside the shaded pink area outlines the modeled area greater than the 

ambient standard.