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DRAFT Technical Support Document

ARIZONA

Area Designations for the 

2010 Sulfur Dioxide (SO2) Primary National Ambient Air Quality Standard

Summary

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

“unclassifiable”, “attainment”, or “nonattainment” 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 and portions of counties in Arizona that EPA intends to initially 

designate “nonattainment” based on monitored violations.

Table 1. Nonattainment Designations for Arizona

Area (listed alphabetically)

Arizona Recommendation of 

Areas/Counties

EPA’s Intended 

Nonattainment 

Areas/Counties

Hayden

Gila County (partial)

Pinal County (partial)

Nonattainment

Nonattainment

Nonattainment

Nonattainment

Miami

Gila 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 attained when the 3-year average 

of the 99th percentile of the daily maximum 1-hour average concentration at each monitor in an area 

does not exceed 75 ppb. 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 requires that not later than 1 year after promulgation of a new or revised 

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

This deadline was June 3, 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 intend to follow the same process for tribes, pursuant to 

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

designate tribal areas, in consultation with the tribes, on the same schedule as state designations. If a 

state or tribe did not submit designation recommendations, EPA will promulgate the designations that it 

deems appropriate. If a state or tribe disagrees with EPA’s intended area designations, it has an 

opportunity to demonstrate why any proposed modification is 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, metropolitan planning organization), among any other 

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

hour SO2 NAAQS.

As defined at 18 U.S.C. 1151, “Indian country” refers to: “(a) all land within the limits of any Indian 

reservation under the jurisdiction of the United States Government, notwithstanding the issuance of any 

patent, and, including rights-of-way running through the reservation, (b) all dependent Indian 

communities within the borders of the United States whether within the original or subsequently 

acquired territory thereof, and whether within or without the limits of a state, and (c) all Indian 

allotments, the Indian titles to which have not been extinguished, including rights-of-way running 

through the same.” EPA recognizes the sovereignty of tribal governments, and has attempted to take 

the desires of the tribes into account in establishing appropriate unclassifiable and nonattainment area 

boundaries, in accordance with EPA’s December, 2011 Policy for Establishing Separate Air Quality 

Designations for Areas of Indian Country1

.

The March 24, 2011, memo recommended that area boundaries default to the county boundary unless 

additional provided information justifies a larger or smaller boundary than 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, tribes and/or EPA may support a different boundary than a default county 

boundary.

 1 http://www.epa.gov/ttn/caaa/t1/memoranda/20120117indiancountry.pdf
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In this TSD, EPA discusses its review and technical analysis of the nonattainment area 

recommendations submitted by the state of Arizona for designations of the 1-hour SO2 standard. Based 

on our review of information discussed below, EPA intends to agree with the state’s recommendation 

to designate portions of Gila County and Pinal County nonattainment.
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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 a state or tribe has recommended to EPA be 

designated as nonattainment.

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 Hayden, Arizona

Introduction 

This technical analysis for Hayden, Arizona identifies the partial county with a monitor that violates the 

2010 SO2 NAAQS, 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 in 

EPA’s Designation Guidance, issued on March 24, 2011.

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Figure 1 shows the areas in Arizona which EPA intends to designate nonattainment. Figure 2 is a map 

showing the locations of SO2 monitors in Hayden, Arizona and surrounding counties. Violating 

monitors are shown with a red icon; monitors attaining the standard are shown with green icons. 

Design values for each monitor are listed in Figure 2, and in Table 2 below.

 2 http://www.epa.gov/air/sulfurdioxide/guidance.html

Figure 1
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In May 2011, Governor Janice K. Brewer recommended that portions of Gila County and Pinal County

be designated as “nonattainment” and the remaining counties and partial counties be designated 

“unclassifiable” for the 2010 SO2 NAAQS based on monitored air quality data from 2007-2009 (letter 

to EPA Region 9 Administrator Jared Blumenfeld from Governor Janice K. Brewer, May 25, 2011). 

Consistent with the existing Hayden nonattainment area and Miami maintenance area for the 1971 SO2

NAAQS, the state recommended that the same portions of Gila County and Pinal County (except those 

portions in Indian country) be designated as the Hayden and Miami nonattainment areas for the 2010 

SO2 NAAQS. The state recommendation was based primarily on monitoring data and consideration of 

emissions data from the 2005 National Emissions Inventory (NEI). 

Based on EPA's technical analysis described below, EPA intends to concur with the state’s 

recommendation to initially designate Gila County (partial) and Pinal County (partial) as nonattainment 

for the 2010 SO2 NAAQS as part of the Hayden nonattainment area. These counties are listed above in 

Table 1.

Figure 2
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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 Gila County and Pinal County, in the intended Hayden 

nonattainment area and in the surrounding area based on data for the 2009-2011 period.

The Governor’s recommendation was based on data from Federal Reference Method (FRM) or Federal 

Equivalent Method (FEM) monitors located in the state letter to EPA Region 9 Administrator Jared

Blumenfeld from Governor Janice K. Brewer, May 25, 2011.3

The 2011 SO2 NAAQS design values for counties in the intended Hayden nonattainment area and 

surrounding area are shown in Table 2. Design values are calculated using the 3-year average of the 

99th percentile of 1-hour daily maximum SO2 concentrations, and compared to the NAAQS of 75 ppb, 

according to requirements of 40 CFR 50.17.

Table 2. Air Quality Data for Nonattainment Designations in Arizona

County

State

Recommended

Nonattainment?

Monitor Name Monitor Air 

Quality

System ID

Monitor Location SO2 Design

Value,

2009-2011

(ppb)

Gila, 

Arizona Yes (partial) Miami Ridgeline 04-007-0009 4030 Linden Street 111

Hayden Old Jail 04-007-1001 Jail-Canyon Dr, Hayden 259

Maricopa, 

Arizona No

Central Phoenix 04-013-3002

1645 E. Roosevelt St, Central 

Phoenix 9

South Scottsdale 04-013-3003

2857 N. Miller Road, South 

Scottsdale 8*

Durango Complex 04-013-9812 2702 AC Ester Brook Blvd 8**

JLG Supersite 04-013-9997 4530 N. 17th Ave 7*

Pima, 

Arizona No

22nd and 

Craycroft 04-019-1011 1237 S. Beverly, Tucson 8*

Children’s Park 

NCore 04-019-1028 400 W. River Road 4**

Monitors in Bold have the highest 2009-2011 design value in the respective county.

*Incomplete data, provided for informational purposes only, not relevant for comparison to the NAAQS. These stations 

stopped monitoring for comparison to the SO2 NAAQS after December 2010. The South Scottsdale monitor was moved to 

the Durango Complex station; JLG Supersite started monitoring for trace levels of SO2 instead of for comparison to the 

NAAQS; 22nd and Craycroft SO2 monitoring was moved to the Children’s Park NCore station.

**Incomplete data, provided for informational purposes only, not relevant for comparison to the NAAQS. These stations 

began monitoring for comparison to the SO2 NAAQS in late 2010 or 2011.

 3 Note: Monitors that are eligible for providing design value data generally include State and Local Air Monitoring Stations 

(SLAMS) that are sited in accordance with 40 CFR part 58, Appendix D (Section 4.4) and operating with a FRM or FEM 

monitor that meets the requirements of 40 CFR part 58, Appendix A. All data from a special purpose monitor (SPM) using 

an FRM or FEM which has operated for more than 24 months are eligible for comparison to the NAAQS unless the 

monitoring agency demonstrates that the data came from a particular period during which the requirements of Appendix A 

(quality assurance requirements) or Appendix E (probe and monitoring path siting criteria) were not met.
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Gila County shows violations of the 2010 SO2 NAAQS. No other SO2 monitors in Arizona show 

violations of the 2010 SO2 NAAQS. Therefore, some areas in Gila 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 nonattainment status. 

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

information. 

Two SO2 monitors are violating the standard in Arizona. Both violating monitors are located in Gila 

County. The Hayden Old Jail monitor (Air Quality System (AQS) ID 04-007-1001) is a sourceoriented monitor located approximately 920 meters (0.57 miles) from the ASARCO, LLC – Hayden 

smelter stack (see Figure 2). Nestled in the southern, V-shaped tip of Gila County, the monitor is about 

860 meters (0.54 miles) from the Pinal County border (see Figure 2). The Miami Ridgeline monitor 

(AQS ID 04-007-0009) is also a source-oriented monitor, located approximately 1,390 meters (0.86 

miles) from the Freeport-McMoRan Miami Smelter. The Freeport-McMoRan Miami Smelter is 

roughly 45.5 kilometers (28 miles) northwest of the ASARCO, LLC – Hayden smelter.

Six additional SO2 monitors have been operated in recent years in Maricopa and Pima counties. These 

monitors are not source-oriented and are located in the urban cores of the Phoenix and Tucson 

metropolitan areas, which are over 50 miles away from the violating monitors located in Gila County 

(see Figure 2, above). The low concentrations in these locations suggest that they are not impacted by 

the same sources that are impacting the violating monitors.

Figure 3
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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 emission data for SO2, as well as emissions from nearby point sources.

Emissions

For this analysis, EPA relied on information from the 2008 National Emissions Inventory (NEI) 

emissions database (NEI08V2). Arizona did not provide updated emissions information. Should EPA 

become aware of new or updated emissions inventories, EPA will take the new information into 

consideration for the final designations.

Table 3 shows total emissions of SO2 in 2008 (given in tons) for all 15 counties in Arizona and single 

sources emitting greater than 100 tons per year of SO2 according to the 2008 NEI. The counties that 

contain part of the intended Hayden nonattainment area for the 2010 SO2 NAAQS are shown in bold. 
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Table 3. SO2 Emissions in 2008

County

Facility 

Located in 

State 

Recommended 

Nonattainment 

Area?

Facility > 100 tons per year of SO2

emissions

Facility 

Location

SO2 Air 

Emissions 

(2008 NEIv2) 

(tons)

Total 

County 

2008 SO2

Emissions 

(tons)

Gila

Yes (Hayden) ASARCO, LLC - Hayden Smelter Hayden 21,742

28,940

Yes (Miami) Freeport-McMoRan Miami Smelter Miami 7,091

- Other point, nonpoint, nonroad, onroad - 107

Apache

No Salt River Project (Coronado) St. Johns 15,900

22,574

No Tucson Electric Power Company Springerville 6,562

- Other point, nonpoint, nonroad, onroad - 112

Navajo

No Arizona Public Service (Cholla) Joseph City 16,421

19,201

No Catalyst Paper (Snowflake) Inc. Snowflake 2,556

- Other point, nonpoint, nonroad, onroad - 224

Pima No Tucson Electric Power (Irvington) Tucson 2,884

- Other point, nonpoint, nonroad, onroad - 1,897 4,781

Maricopa No Phoenix Sky Harbor International Airport Phoenix 252

- Other point, nonpoint, nonroad, onroad - 2,886 3,138

Cochise

No AZ Electric Power (Apache) Cochise 1,903

3,105

No Chemical Lime Company - Douglas Douglas 1,013

- Other sources (nonpoint, nonroad, onroad) - 189

Yavapai No Nelson Lime Plant Peach Springs 1,955

- Other point, nonpoint, nonroad, onroad - 368 2,323

Pinal - Other point, nonpoint, nonroad, onroad - 464 464

Mohave - Other point, nonpoint, nonroad, onroad 408 408

Coconino - Other point, nonpoint, nonroad, onroad - 350 350

Yuma - Other point, nonpoint, nonroad, onroad 248 248

La Paz - Other point, nonpoint, nonroad, onroad 75 75

Santa 

Cruz - Other point, nonpoint, nonroad, onroad 71 71

Greenlee - Other point, nonpoint, nonroad, onroad 54 54

Graham - Other point, nonpoint, nonroad, onroad - 38 38

Total emissions of SO2 are highest from Gila County. In 2008, the ASARCO, LLC – Hayden Smelter 

emitted over 20,000 tons of SO2, three times more than the second largest source (Freeport-McMoRan 

Miami Smelter) of SO2 in Gila County. Both smelters in Gila County are primary copper smelters. 

Apache and Navajo counties also contain coal-fired electric utility generating units that are large 

sources of SO2: Coronado Generating Station (15,900 tons in 2008) and Springerville Generating 

Station (6,562 tons in 2008) in Apache County, and Cholla Power Plant (16,421 tons in 2008) in 

Navajo County. Total emissions of SO2 from Pinal County are low (464 tons in 2008) compared to 

Gila, Apache, and Navajo counties. Gila, Apache, and Navajo counties together comprise 82% of total 

SO2 emissions from the state of Arizona. These five largest stationary sources in the three counties 

comprised 79% of total SO2 emissions from Arizona in 2008. See Figure 4 for the geographic 

distribution of these stationary sources.
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The state-recommended Hayden nonattainment area for the 2010 SO2 NAAQS includes the ASARCO, 

LLC – Hayden Smelter. As shown in Figure 4 and Table 3, besides the two largest sources in Gila 

County, both of which EPA intends to include in nonattainment areas, there are no other facilities 

emitting greater than 100 tons per year of SO2 in Gila, Pinal, or Graham County. The San Carlos tribal 

lands to the east of the State’s recommended Hayden nonattainment area, also do not have any facilities 

emitting greater than 100 tons per year of SO2 according to the 2008 NEIV2.

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 Hayden, 

Arizona intended nonattainment area up to and including 2008. Since 2008, the ASARCO, LLC –

Hayden Smelter has completed two projects, one in 2010 involving addition of a revert screen, and one 

in 2012 involving additional ventilation and a baghouse to service three existing anode furnaces.

Figure 4
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Neither of these projects resulted in changes to permitted SO2 emissions limits for the facility. See the 

source’s Title V federal operating permit renewal and two ADEQ permit actions/revisions that occurred 

since 2008 (52397-MPR and 54251-MPR).4

Population

Gila County’s population as of the 2010 census was 53,597. From 2000 to 2010 the county grew by 

4.4% and had a population density of 11.3 persons per square mile. Pinal County’s population as of the 

2010 census was 375,770. From 2000 to 2010 the county grew by 109.1% and had a population 

density of 70.0 persons per square mile.

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 meteorological 

data available for the area. Such data may provide evidence of the potential for SO2 emissions sources 

located upwind of a violating monitor to contribute to ambient SO2 levels at the violation location.

Temperature and precipitation data is available from the nearby Winkelman 6 S station, part of the 

National Weather Service Cooperative Observer Program. This station typically measures only 14 

inches of rain each year, with nearly half of that occurring during the summer months of July through 

September, coinciding with the Arizona “monsoon” season. There is less than an inch of snow each 

year. Daily temperature highs range from 64 to 91 degrees Fahrenheit depending on season, and lows 

range from 31 to 69 degrees Fahrenheit. See Figure 5 for the location of the Winkleman 

meteorological station.

The varied elevations in the area cause complex wind flow locally. Within and adjacent to the Gila 

River and San Pedro River valleys, drainage winds tend to dominate at night under stable conditions. 

To the west of the smelter, drainage flows toward the west, while east of the smelter the drainage flows 

to the south. Given the smelter's elevated location and plume buoyancy, some emissions would be 

expected to rise above these surface flows. However, on sunny days the heated ground warms the air 

and enhances vertical mixing. Under such convective conditions, the plume could nevertheless be 

mixed down to the ground to varying degrees. This vertical mixing also causes the flow to be coupled 

with winds aloft, which generally flow toward the east.

Over the years, wind data has been collected at multiple locations in and around Hayden. Sites include 

the Hayden Maintenance Yard (“Hayden”), Hayden-Winkelman High School (“Winkelman”), and 

Globe Highway (data prepared for “Draft Report, Remedial Investigation Report for the ASARCO, 

LLC Hayden Plant Site, Hayden, Gila County, Arizona”, Prepared for U.S. Environmental Protection 

Agency Region IX, San Francisco, CA., CH2M Hill, August 2008). These stations are shown in Figure 

5. Wind roses from these stations are shown in Figure 6. The Winkelman site is nearest the junction of 

the Gila and San Pedro River valleys, and the Globe Highway site is in the northeastern portion of the 

Gila River valley before it joins the San Pedro. All of the dominant wind directions are consistent with 

 4 Further information about Arizona federal Title V air permits can be found on EPA’s website at:

http://www.epa.gov/region9/air/permit/title-v-permits.html
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the orientation of the valleys. However, when morning and evening wind frequencies are plotted 

separately, not all of the directions are consistent with slope flow, e.g., afternoon flow at Hayden is 

toward the east, but downslope flow in the Gila River valley would be toward the northwest. There is a 

similar evening component toward the east at Winkelman on some days, but more of a downslope flow 

on other days. At Globe Highway, flow directions are consistent with slope flows. The differences 

between sites located relatively close together show the complexity of the flow in the area. Transport 

of pollutants would be expected to occur mainly along the Gila-San Pedro River valleys (northwestsoutheast orientation), somewhat circumscribed by the orientations of the valleys and the surrounding 

mountains. 

Terrain Around Hayden, Arizona:

with SO2 monitor (red circle), cities (purple circles & labels), 

meteorological stations (blue triangles & labels).

Figure 5
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Hayden a.m. and p.m. wind roses

Winkelman a.m. and p.m. wind roses

Figure 6
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Geography/topography (mountain ranges or other air basin boundaries)

As shown in Figure 5 (above) and Figure 7 (below), Hayden and the ASARCO, LLC - Hayden smelter 

are located in very complex terrain, with the Gila River making a winding semi-circle around the east 

and south of the facility, and intersected by the San Pedro River valley from the south. The facility 

itself is elevated relative to the valleys; there is a 200-foot hill just south of the facility. In all directions 

there is a mountain side. Hayden is at roughly 2,000 feet elevation; the Dripping Springs Mountains to 

the north rise to 4,000 feet; the Tortilla Mountains on the northwest, west, and south rise 3,300 to 4,000 

feet. Terrain rises more gently within the Gila-San Pedro River valleys from the northwest toward the 

southeast. The intended nonattainment area encompasses the Gila River valley from where it narrows 

in the northwest corner of the area, to where it joins with the San Pedro River valley in roughly the 

center of the area, and to a bend in the San Pedro River in the southeast corner. The surrounding 

mountains likely limit the extent of the area exceeding the SO2 standard to a relatively small area 

around the smelter, the main source of SO2 emissions. For the same reason, locations outside the 

particular valleys intersecting at Hayden are not expected to contribute to SO2 NAAQS exceedances 

there. 

Figure 7
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Jurisdictional boundaries 

The Office of Management and Budget (OMB) defines metropolitan (metro) and micropolitan (micro) 

statistical areas based on census information. A metro statistical area contains a core urban area of 

50,000 or more in population, and a micro statistical area contains an urban core of at least 10,000 but 

less than 50,000 in population. A Core Based Statistical Area (CBSA) is a collective term for both 

metro and micro areas. OMB may further define a combined statistical area (CSA) as an aggregate of 

adjacent metro or micro statistical areas that are linked by commuting ties.

The state of Arizona is divided into 15 counties (listed in Table 3). Within the state, OMB has defined 

11 CBSAs comprising six metro statistical areas and five micro statistical areas. OMB has not 

aggregated any metro or micro statistical areas in Arizona into a CSA. Two counties in Arizona, 

Apache and La Paz, are not defined by OMB as a metro or micro statistical area. The Payson 

Micropolitan Statistical Area comprises Gila County, and the Phoenix-Mesa-Glendale Metropolitan 

Statistical Area comprises Maricopa and Pinal counties. The Payson metro area comprises the entirety 

of Gila County, and is named for the most populated city of the county, Payson City. Payson City is 

outside the state’s recommended nonattainment area and there are no other large population centers in 

the area, apart from the town of Hayden itself, which has several hundred residents.

To manage air quality, the state of Arizona has one state agency, the Arizona Department of 

Environmental Quality (ADEQ), and three local agencies: Maricopa County Air Quality Department, 

Pima County Department of Environmental Quality, and Pinal County Air Pollution/Quality Control 

District. Air quality planning for the existing Hayden nonattainment area under the 1971 SO2 NAAQS, 

composed of the same portions of Gila and Pinal counties as the state’s recommended nonattainment 

area for the 2010 SO2 NAAQS, is under the jurisdiction of ADEQ. Originally, for the 1971 NAAQS, 

the Hayden area was split between two county-wide SO2 nonattainment areas for Gila and Pinal 

counties (see 43 FR 8968, March 3, 1978). At the request of the state of Arizona, the boundary for the 

Hayden area was reduced to nine townships in and around the town of Hayden (44 FR 21261, April 10, 

1979). See also, 40 CFR Section 81.303. In addition, six adjacent townships were designated as 

‘‘cannot be classified.’’ Section 107(d)(1)(C) of the 1990 Clean Air Act Amendments (CAAA) brought 

forward, by operation of law, the nonattainment designations for areas, such as the Hayden SO2 area, 

that continued to be designated as nonattainment at the time of enactment of the CAAA, i.e., areas that 

had not been redesignated to ‘‘attainment’’ prior to the CAAA’s November 15, 1990 enactment date.

The then-existing nonattainment area for Hayden under the 1971 SO2 NAAQS included a portion of 

Indian country along the eastern boundary. The intended Hayden nonattainment area for the 2010 SO2

NAAQS is the same area as the existing 1971 SO2 NAAQS brought forward by operation of law 

following the 1990 CAAA, without the portion of Indian country. The existing Hayden nonattainment 

area attained the 1971 SO2 NAAQS such that ADEQ submitted a maintenance plan to EPA in 2002.

EPA has not acted on the redesignation request and maintenance plan.

As defined at 18 U.S.C. 1151, “Indian country” refers to: “(a) all land within the limits of any Indian 

reservation under the jurisdiction of the United States Government, notwithstanding the issuance of any 

patent, and, including rights-of-way running through the reservation, (b) all dependent Indian 

communities within the borders of the United States whether within the original or subsequently 

acquired territory thereof, and whether within or without the limits of a state, and (c) all Indian 

allotments, the Indian titles to which have not been extinguished, including rights-of-way running 
17

through the same.” EPA recognizes the sovereignty of tribal governments, and has attempted to take 

the desires of the tribes into account in establishing appropriate unclassifiable and nonattainment area 

boundaries. No areas of Indian country are included in the intended Hayden, Arizona nonattainment 

area.

Other Relevant Information

In its May 25, 2011 letter, ADEQ provided additional information to support its assertion that

presumptive use of full county boundaries as the nonattainment area boundary is inappropriate for 

geographically large counties. The state argued that the use of full county boundaries as the 

presumptive nonattainment area boundary for a violating monitor results in disparities in the size of 

nonattainment areas. For example, the state compared the area of Gila County (4,796 square miles) 

with the area of the entire state of Connecticut (4,845 square miles). A violating monitor in Middlesex 

County, Connecticut, would result in a presumptive nonattainment area boundary encompassing 369 

square miles. Applying this presumption in Arizona would result in a nonattainment area (Gila 

County) that is 13 times larger than a full Middlesex County nonattainment area in Connecticut. The 

state further highlighted that the violating monitor in their recommended Hayden nonattainment area is 

less than 0.5 miles from the southwest border of Gila and Pinal counties, and more than 100 miles from 

the northern border of Gila and Coconino counties. Therefore, the state concluded that its consideration 

of partial counties for the Hayden and Miami nonattainment areas was appropriate.

Conclusion

After considering the factors described above, EPA intends to concur with the state’s recommendation 

to initially include Pinal County (partial) and Gila County (partial) as the Hayden, Arizona

nonattainment area for the 2010 SO2 NAAQS, based on the violating monitor. 

The air quality monitor in Hayden, Arizona shows a violation of the 2010 SO2 NAAQS based on 2009-

2011 air quality data. EPA preliminarily concludes that the state’s recommended boundary contains 

the area violating the standard as well as areas causing or contributing to the violation. The monitor is 

source-oriented, and is located in the southernmost tip of Gila County. Due to constraints imposed by 

the complex terrain in the Hayden area (see Geography/Topography discussion above), it is expected 

that the extent of the area exceeding the SO2 standard is confined to a relatively small area around the 

main source of SO2 emissions, the ASARCO, LLC - Hayden smelter. For the same reason, locations 

outside the particular valleys intersecting at Hayden are not expected to contribute to NAAQS 

exceedances at the Hayden monitor. The meteorology factor is not significant in determining a 

boundary for the nonattainment area, but available data confirms the importance of the topography in 

limiting the intended nonattainment area to the nearby river valleys and their surroundings. The state’s 

recommended boundary for the intended Hayden nonattainment area is also consistent with the existing 

Hayden nonattainment boundary for the 1971 SO2 NAAQS, without areas of Indian country. The 

existing (for the 1971 SO2 NAAQS) Hayden SO2 nonattainment area attained the standard prior to 

2002, at which time ADEQ submitted a maintenance plan and request for EPA to redesignate the area 

to attainment for the 1971 NAAQS. All non-Indian country lands are under the jurisdiction of ADEQ.
18

Based on the consideration of all the relevant and available information, as described above, EPA’s 

preliminary conclusion is that the boundaries described herein encompass an area that does not meet (or 

that contributes to ambient air quality in a nearby area that does not meet) the 2010 SO2 NAAQS, based 

on the violating monitor information.
19

Technical Analysis for Miami, Arizona

Introduction 

This technical analysis for Miami, Arizona identifies the partial county with a monitor that violates the 

2010 SO2 NAAQS 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 in 

EPA’s Designation Guidance, issued on March 24, 2011.

5

 

Figure 8 shows the areas in Arizona which EPA intends to designate nonattainment. Figure 9 is a map 

of SO2 monitors in the area and the surrounding counties. Violating monitors are shown with a red 

icon; monitors attaining the standard are shown with green icons. Design values for each monitor are 

listed in Figure 9 and in Table 4, below.

 5 http://www.epa.gov/air/sulfurdioxide/guidance.html

Figure 8
20

In May 2011, Governor Janice K. Brewer recommended that portions of Gila County and Pinal County 

be designated as “nonattainment”, and the remaining counties and partial counties be designated 

“unclassifiable” for the 2010 SO2 NAAQS based on monitored air quality data from 2007-2009 (letter 

to EPA Region 9 Administrator Jared Blumenfeld from Governor Janice K. Brewer, May 25, 2011). 

Consistent with the existing Hayden nonattainment area and Miami maintenance area for the 1971 SO2

NAAQS, the state recommended that the same portions of Gila County and Pinal County be designated 

as the Hayden and Miami nonattainment areas for the 2010 SO2 NAAQS. The state recommendation 

was based primarily on monitoring data and consideration of emissions data from the 2005 National 

Emissions Inventory (NEI). 

Based on EPA's technical analysis described below, EPA intends to concur with the state’s 

recommendation and initially designate Gila County (partial) as nonattainment for the 2010 SO2

NAAQS as the Miami nonattainment area. The county is listed above in Table 1.

Figure 9
21

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 Gila County, in the intended Miami nonattainment area and the 

surrounding area based on data for the 2009-2011 period.

The Governor’s recommendation was based on data from Federal Reference Method (FRM) or Federal 

Equivalent Method (FEM) monitors located in the state (letter to EPA Region 9 Administrator Jared 

Blumenfeld from Governor Janice K. Brewer, May 25, 2011).6

The 2010 SO2 NAAQS design values for counties in the intended Miami nonattainment area and 

surrounding area are shown in Table 4. Design values are calculated using the 3-year average of the 

99th percentile of 1-hour daily maximum SO2 concentrations, and compared to the NAAQS of 75 ppb, 

according to requirements of 40 CFR 50.17.

Table 4. Air Quality Data for Nonattainment Designations in Arizona

County

State

Recommended

Nonattainment? Monitor Name

Monitor 

Air Quality

System ID Monitor Location

SO2 Design

Value,

2009-2011

(ppb)

Gila, 

Arizona Yes (partial) Miami Ridgeline 04-007-0009 4030 Linden Street 111

Hayden Old Jail 04-007-1001 Jail-Canyon Dr, Hayden 259

Maricopa, 

Arizona No

Central Phoenix 04-013-3002

1645 E. Roosevelt St, 

Central Phoenix 9

South Scottsdale 04-013-3003

2857 N. Miller Road, South 

Scottsdale 8*

Durango 

Complex 04-013-9812 2702 AC Ester Brook Blvd 8**

JLG Supersite 04-013-9997 4530 N. 17th Ave 7*

Pima, 

Arizona No

22nd and 

Craycroft 04-019-1011 1237 S. Beverly, Tucson 8*

Children’s Park 

NCore 04-019-1028 400 W. River Road 4**

Monitors in Bold have the highest 2009-2011 design value in the respective county.

*Incomplete data, provided for informational purposes only, not relevant for comparison to the NAAQS. These stations 

stopped monitoring for comparison to the SO2 NAAQS after December 2010. The South Scottsdale monitor was moved to 

the Durango Complex station; JLG Supersite started monitoring for trace levels of SO2 instead of for comparison to the 

NAAQS; 22nd and Craycroft SO2 monitoring was moved to the Children’s Park NCore station.

**Incomplete data, provided for informational purposes only, not relevant for comparison to the NAAQS. These stations 

began monitoring for comparison to the SO2 NAAQS in late 2010 or 2011.

 6 Note: Monitors that are eligible for providing design value data generally include State and Local Air Monitoring Stations 

(SLAMS) that are sited in accordance with 40 CFR Part 58, Appendix D (Section 4.4) and operating with a FRM or FEM 

monitor that meets the requirements of 40 CFR Part 58, Appendix A. All data from a special purpose monitor (SPM) using 

an FRM or FEM which has operated for more than 24 months are eligible for comparison to the NAAQS unless the 

monitoring agency demonstrates that the data came from a particular period during which the requirements of Appendix A 

(quality assurance requirements) or Appendix E (probe and monitoring path siting criteria) were not met.
22

Gila County shows violations of the 2010 SO2 NAAQS. No other SO2 monitors in Arizona show 

violations of the 2010 SO2 NAAQS. Therefore, some areas in Gila 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 nonattainment status. 

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

information. 

Two SO2 monitors are violating the standard in Arizona. Both violating monitors are located in Gila 

County (see Figure 9). The Miami Ridgeline monitor (AQS ID 04-007-0009) is a source-oriented 

monitor, located approximately 1,390 meters (0.86 miles) from the Freeport-McMoRan Miami Inc. 

(FMMI) copper smelter (see Figure 10). The FMMI smelter is roughly 45.5 kilometers (28 miles) 

northwest of the other violating monitor, Hayden Old Jail, a source-oriented monitor located near the 

ASARCO, LLC – Hayden smelter.

Figure 10
23

Six additional SO2 monitors have been operated in Maricopa and Pima counties in recent years. These 

monitors are not source-oriented and are located in the urban cores of the Phoenix and Tucson 

metropolitan areas, which are over 50 miles away from the violating monitors located in Gila County 

(see Figure 9, above). The low concentrations in these locations suggest that they are not impacted by 

the same sources that are impacting the violating monitors.

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 emission data for SO2, as well as emissions from nearby point sources.

Emissions 

For this analysis, EPA relied on information from the 2008 National Emissions Inventory (NEI) 

emissions database (NEI08V2). Arizona did not provide updated emissions information. Should EPA 

become aware of new or updated emissions inventories, EPA will take the new information into 

consideration for the final designations.

Table 5 shows total emissions of SO2 (given in tons per year) for all 15 counties in Arizona and sources 

emitting greater than 100 tons per year of SO2 according to the 2008 NEI. The county that contains all 

of the Miami nonattainment area for the 2010 SO2 NAAQS is shown in bold. 
24

Table 5. SO2 Emissions in 2008

County

Facility 

Located in 

State 

Recommended 

Nonattainment 

Area?

Facility > 100 tons per year of SO2

emissions

Facility 

Location

SO2 Air 

Emissions 

(2008 NEI v2) 

(tons)

Total 

County 

2008 SO2

Emissions 

(tons)

Gila

Yes (Hayden) ASARCO, LLC - Hayden Smelter Hayden 21,742

28,940

Yes (Miami) Freeport-McMoRan Miami Smelter Miami 7,091

- Other point, nonpoint, nonroad, onroad - 107

Apache

No Salt River Project (Coronado) St. Johns 15,900

22,574

No Tucson Electric Power Company Springerville 6,562

- Other point, nonpoint, nonroad, onroad - 112

Navajo

No Arizona Public Service (Cholla) Joseph City 16,421

19,201

No Catalyst Paper (Snowflake) Inc. Snowflake 2,556

- Other point, nonpoint, nonroad, onroad - 224

Pima No Tucson Electric Power (Irvington) Tucson 2,884

- Other point, nonpoint, nonroad, onroad - 1,897 4,781

Maricopa No Phoenix Sky Harbor International Airport Phoenix 252

- Other point, nonpoint, nonroad, onroad - 2,886 3,138

Cochise

No AZ Electric Power (Apache) Cochise 1,903

3,105

No Chemical Lime Company - Douglas Douglas 1,013

- Other sources (nonpoint, nonroad, onroad) - 189

Yavapai No Nelson Lime Plant 

Peach 

Springs 1,955

- Other point, nonpoint, nonroad, onroad - 368 2,323

Pinal - Other point, nonpoint, nonroad, onroad - 464 464

Mohave - Other point, nonpoint, nonroad, onroad 408 408

Coconino - Other point, nonpoint, nonroad, onroad - 350 350

Yuma - Other point, nonpoint, nonroad, onroad 248 248

La Paz - Other point, nonpoint, nonroad, onroad 75 75

Santa 

Cruz - Other point, nonpoint, nonroad, onroad 71 71

Greenlee - Other point, nonpoint, nonroad, onroad 54 54

Graham - Other point, nonpoint, nonroad, onroad - 38 38

Total emissions of SO2 are highest from Gila County. In 2008, the FMMI copper smelter was the 

second largest source of SO2 in Gila County, and the fourth largest source in Arizona. Both smelters 

(FMMI and ASARCO, LLC) in Gila County are primary copper smelters. Apache and Navajo counties 

also contain coal-fired electric utility generating units that are large sources of SO2: Coronado 

Generating Station (15,900 tons in 2008) and Springerville Generating Station (6,562 tons in 2008) in 

Apache County, and Cholla Power Plant (16,421 tons in 2008) in Navajo County. Total emissions of 

SO2 from Pinal County are low (464 tons in 2008) compared to Gila, Apache, and Navajo counties. 

Gila, Apache, and Navajo counties together comprise 83% of total SO2 emissions from the state of 

Arizona. The five largest stationary sources in those three counties comprised 79% of total SO2

emissions from Arizona in 2008. The existing Miami maintenance area for the 1971 SO2 NAAQS is 
25

identical to the state’s recommended Miami nonattainment area for the 2010 SO2 NAAQS and includes 

the FMMI smelter. See Figure 11.

Emissions Controls

The emissions data used by EPA in this technical analysis and provided in Table 5 represent emissions 

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

Arizona intended nonattainment area up to and including 2008. Since 2008, FMMI has had several 

permit revisions, including: installation of a coal injection system with a dust collector system, 

clarification and/or correction to existing permit conditions, revision to allow additional use of an 

existing screening machine, update of the sulfur balance methodology to include a gravimetric method, 

and addition of small internal combustion engines. None of the permit revisions resulted in changes to 

permitted SO2 emission limits. See seven ADEQ permit actions/revisions from 2008 to the present: 

43398-SPR, 45593-MPR, 48448-MPR, 49986-MPR, 54218-MPR, 55226-MPR, and 55691-MPR.

These seven permit actions/revisions were included in the Title V Renewal Operating Permit 53592 

issued November 26, 2012.7

 7 Further information about Arizona federal Title V air permits can be found on EPA’s website at:

Figure 11
26

Population

Gila County’s population as of the 2010 census was 53,597. From 2000 to 2010 the county grew by 

4.4% and had a population density of 11.3 persons per square mile. 

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 meteorological 

data available for the area. The data may provide evidence of the potential for SO2 emissions sources 

located upwind of a violating monitor to contribute to ambient SO2 levels at the violation location.

Temperature and precipitation data are available from the Miami station, part of the National Weather 

Service Cooperative Observer Program. Around 20 inches of rain fall each year at the Miami station, 

roughly evenly distributed between the months, except in April, May, and June, when less than a half 

inch of rain falls per month. Normal daily temperature highs range from 96 degrees Fahrenheit (°F) in 

summer to 62 °F in winter, while normal lows are 65 °F in summer to 34 °F in winter.

The closest meteorological station to the violating Miami monitor is Globe station CW1546, part of the 

National Weather Service Cooperative Observer Program. The city of Globe is about five miles from

Miami, roughly to the east. Globe is in the Pinal Creek Valley, oriented at right angles to the valley 

where Miami is located, with a more west-east orientation. The 2010 wind data shows flows consistent 

with the valley orientation (see Figure 12). Flow toward the west is the most frequent, but flow toward 

the east-southeast also occurs. Some, but not all of the flows are consistent with diurnal slope flows; 

the complexity of the surrounding terrain means there are multiple influences controlling the flow. 

Because of the complex terrain, and the spatial separation from Miami, this data is of limited usefulness

for drawing conclusions about the Miami nonattainment area boundary, except to illustrate that flows 

largely conform to valley orientation, with slope flow being an important phenomenon. 

 

http://www.epa.gov/region9/air/permit/title-v-permits.html
27

Globe CW1546 Wind Rose, 2010; A.M. hours

Globe CW1546 Wind Rose, 2010; P.M. hours

Globe a.m. and p.m wind roses

Figure 12
28

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

As shown in Figures 13 and 14, Miami and the FMMI smelter are located in complex terrain. Miami is 

at roughly 3,500 feet elevation, located in the southwest-northeast tending river valley of the Bloody 

Tanks Wash. To the northeast, this valley joins the Pinal Wash at a right angle; the Wash then tends 

northwest and merges with the Pinal Creek Valley. Northeast beyond this juncture, the Apache Peaks 

rise to 4,300 feet, and to 6,200 feet a bit outside of the intended nonattainment area. To the northwest, 

Webster Mountain rises to 5,000 feet; the Pinal and other mountain ranges to the south and southwest 

rise to 6,500 feet; there are various other ridges to the southeast. Thus, Miami is essentially surrounded 

by mountains in all directions; its immediate valley makes a right-angle turn into the Pinal Creek 

Valley, which is all within the intended nonattainment area except for a short narrow portion in the 

north. The existing nonattainment boundaries contain all the areas topographically connected with 

Miami.

Terrain Around Miami, Arizona SO2 Intended Nonattainment Area:

with SO2 monitor (red circle), cities (purple circles & labels), 

meteorological stations (blue triangles & labels).

Figure 13
29

Jurisdictional boundaries 

The Office of Management and Budget (OMB) defines metropolitan (metro) and micropolitan (micro) 

statistical areas based on census information. A metro statistical area contains a core urban area of 

50,000 or more in population, and a micro statistical area contains an urban core of at least 10,000 but 

less than 50,000 in population. A Core Based Statistical Area (CBSA) is a collective term for both 

metro and micro areas. OMB may further define a combined statistical area (CSA) as an aggregate of 

adjacent metro or micro statistical areas that are linked by commuting ties.

The state of Arizona is divided into 15 counties (listed in Table 5). Within the state, OMB has defined 

11 CBSAs: six metro statistical areas and five micro statistical areas. OMB has not aggregated any 

metro or micro statistical areas in Arizona into a CSA. Two counties in Arizona, Apache and La Paz, 

are not defined by OMB as a metro or micro statistical area. 

The intended Miami nonattainment area represents a portion of Gila County, located close to the 

borders of Maricopa and Pinal counties. Gila County comprises the entirety of the Payson Micropolitan 

Figure 14
30

Statistical Area. Although Gila County is adjacent to the Phoenix-Mesa-Glendale Metropolitan 

Statistical Area (composed of Maricopa and Pinal counties), the degree of socio-economic integration 

between the Payson and the Phoenix-Mesa-Scottsdale CBSAs is not sufficient to meet the OMB 

definition of a CSA.

As discussed in the technical analysis for the intended Hayden nonattainment area, for air quality 

management purposes, Gila County falls under the jurisdiction of ADEQ. Originally, the currently 

intended Miami SO2 nonattainment area was not separately defined but rather was included in a 

county-wide SO2 nonattainment area (see 43 FR 8968, March 3, 1978). At the request of the state of 

Arizona, the boundaries were reduced to nine townships in and around the city of Miami (44 FR 21261, 

April 10, 1979). See also, 40 CFR section 81.303. In addition, six adjacent townships were designated 

as ‘‘cannot be classified.’’ Section 107(d)(1)(C) of the 1990 Clean Air Act Amendments (CAAA) 

brought forward, by operation of law, the nonattainment designations for areas, such as the Miami SO2

area, that continued to be designated as nonattainment at the time of enactment of the CAAA, i.e., areas 

that had not been redesignated to ‘‘attainment’’ prior to the CAAAs’ November 15, 1990 enactment 

date. The area achieved attainment with the 1971 SO2 NAAQS in 1984, and ADEQ submitted a 

maintenance plan to EPA in 2002. In January 2007, EPA redesignated the Miami nonattainment area to 

attainment (72 FR 3061, January 24, 2007). In this redesignation and maintenance plan approval, EPA 

also corrected the boundary of the Miami SO2 nonattainment area to exclude a noncontiguous township 

that was erroneously included in the description of the area and to fix a transcription error in the listing 

of one of the other townships (see 72 FR 3061, January 24, 2007 and 40 CFR section 81.303). The 

intended Miami nonattainment area for the 2010 SO2 NAAQS is the same area as the 1971 SO2

NAAQS maintenance area.

Other Relevant Information

In its May 25, 2011 letter, ADEQ provided additional information to support its assertion that

presumptive use of full county boundaries as the nonattainment area boundary is inappropriate for 

geographically large counties. The state argued that the use of full county boundaries as the 

presumptive nonattainment area boundary for a violating monitor results in regional disparities in the 

size of nonattainment areas. For example, the state compared the area of Gila County (4,796 square 

miles) with the area of the entire state of Connecticut (4,845 square miles). A violating monitor in 

Middlesex County, Connecticut, would result in a presumptive nonattainment area boundary 

encompassing 369 square miles. Applying this presumption in Arizona would result in a nonattainment 

area (Gila County) that is 13 times larger than a full-county nonattainment area in Connecticut. 

Therefore, the state concluded that its consideration of partial counties for the Hayden and Miami 

nonattainment areas was appropriate.

Conclusion

After considering the factors described above, EPA intends to concur with the state’s recommendation

to initially include the portion of Gila County listed in Table 1 as the Miami nonattainment area for the 

2010 SO2 NAAQS, based on the violating monitor.

The air quality monitor in Gila County shows a violation of the 2010 SO2 NAAQS, based on 2009-

2011 air quality data. The Freeport-McMoRan Miami Inc. (FMMI) copper smelter located less than 
31

1,400 meters (less than 0.86 mile) away from the violating monitor is expected to be the source of the 

emissions causing the violation. Miami is essentially surrounded by mountains in all directions. Due 

to the constraints imposed by the complex terrain in the Miami area (see Geography/Topography 

discussion above), the extent of the area exceeding the SO2 standard is expected to be confined to a 

relatively small area around the main source of SO2 emissions, the FMMI copper smelter. For the same 

reason, locations outside the particular valley containing Miami are not expected to contribute to Miami 

monitor’s exceedances. The meteorology factor did not play a significant role in determining a 

boundary for the nonattainment area, but available data confirms the relevance of the topography in 

limiting the intended nonattainment area to the nearby river valleys and their surroundings. The 

nonattainment boundaries recommended by the state are therefore expected to contain all the areas 

topographically connected with Miami and causing or contributing to the violation. 

Based on the consideration of all the relevant and available information, as described above, EPA’s 

preliminary conclusion is that the boundaries described herein for the intended Miami, Arizona 

nonattainment area encompass an area that does not meet (or that contributes to ambient air quality in a 

nearby area that does not meet) the 2010 SO2 NAAQS, based on the violating monitor information. No 

areas of Indian country are included in the intended Miami, Arizona nonattainment area.