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Technical Support Document

ARIZONA 

Nonattainment 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 

“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 and portions of counties in Arizona that EPA has initially 

designated “nonattainment” based on monitored violations. EPA is not yet prepared to designate other 

areas in Arizona, and will address such areas in a subsequent round of final designations. 

Table 1. Nonattainment Designations for Arizona 

Area (listed alphabetically) 

Arizona’s Recommendation of 

Areas/Counties 

EPA’s Designated 

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 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 concentrations 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 has not designated 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 has not designated 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 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 we are using 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 nonattainment area designation 

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

Designations for Areas of Indian Country1

. 

The March 24, 2011 designation 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
3 

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 agrees with the state’s recommendation to 

designate portions of Gila County and Pinal County nonattainment and has initially designated those 

areas accordingly. The EPA is not yet reaching conclusions concerning areas in Arizona, and their 

sources, that are outside of the nonattainment area designations addressed in this TSD. EPA will make 

final initial designations decisions for the remaining portions of Arizona in the future. 

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.

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. 

 
4 

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 that county and nearby counties for contributions to SO2

concentrations in the area. EPA has evaluated this county and nearby counties based on the weight-ofevidence of the factors in EPA’s Designation Guidance, issued on March 24, 2011.2

 

Figure 1 shows the Hayden area in Arizona which EPA has initially designated 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 
5 

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). 

In February 2013, EPA responded to Governor Brewer’s 2011 recommendation (“120-day” letter to 

Governor Janice K. Brewer from EPA Region 9 Administrator Jared Blumenfeld, February 6, 2013). 

The February 2013 letter notified the Governor of EPA’s intentions regarding designations for the 2010 

SO2 NAAQS. As stated in the letter, EPA intended to agree with the Governor’s recommendations for 

boundaries of the two nonattainment areas the Governor recommended as nonattainment. The Governor 

replied to EPA’s 120-day letter in April 2013 (letter to EPA Region 9 Administrator Jared Blumenfeld 

Figure 2
6 

from Governor Janice K. Brewer, April 2, 2013). In the reply letter, the Governor reaffirmed the 2011 

recommendations for all areas of the state, but noted that there was a discrepancy with the maps the 

state provided in 2011 for the Hayden, Arizona area. The 2011 maps were included in a document titled 

“Arizona Air Quality Designations, Final Proposed Boundary Recommendation for the 2010 Primary 

National Ambient Air Quality Standard for Sulfur Dioxide” (state technical support document or state 

TSD). 

The state TSD was attached to a letter from the state’s environmental agency to the Governor (letter to 

Governor Janice K. Brewer from Henry R. Darwin, Director, Arizona Department of Environmental 

Quality, letter dated May 2, 2011). In her April 2013 letter, Governor Brewer indicated that EPA 

would receive a corrected map. EPA received the corrected map in a letter dated April 5, 2013 (letter 

to EPA Region 9 Administrator Jared Blumenfeld from Eric Massey, Director, Air Quality Division, 

Arizona Department of Environmental Quality). 

Based on EPA's technical analysis described below, EPA concurs with the state’s recommendation to 

initially designate a portion of Gila County and a portion of Pinal County as nonattainment for the 2010 

SO2 NAAQS, as the Hayden nonattainment area. These counties are listed above in Table 1. We note 

here that the state’s corrected map agrees with the maps that are contained in this document. 

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 Hayden nonattainment area and in the 

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

The Governor’s recommendation was based on 2007-2009 data from Federal Reference Method (FRM) 

or Federal Equivalent Method (FEM) monitors provided 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 Hayden nonattainment area and surrounding 

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

 

 

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. 
7 

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. Pinal County, Arizona did not have any 

SO2 monitors collecting data from 2009-2011. 

*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. 

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

show violations of the 2010 SO2 NAAQS. Therefore, as an analytical starting point, some areas in Gila 

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

that the absence of a violating monitor alone is not a sufficient reason to eliminate nearby counties as 

candidates for nonattainment status. This is because the Clean Air Act defines a nonattainment area as 

any area that violates a NAAQS or contributes to a nearby violation.4

 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 2 and Table 2, above). The Hayden Old Jail monitor (Air Quality System (AQS) 

ID 04-007-1001) is a source-oriented 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 FreeportMcMoRan Miami Smelter is roughly 45.5 kilometers (28 miles) northwest of the ASARCO, LLC – 

Hayden smelter. 

 

4

 Section 107(d)(1)(A)(i) of the Clean Air Act defines a nonattainment area as " ... any area that does not meet (or that 

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

standard for the pollutant... " 
8 

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 recorded in these locations suggest that their design 

values 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 (NEI08V3). Arizona did not provide updated emissions information. 

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 Hayden nonattainment area for the 2010 SO2 NAAQS are shown in bold. 

Figure 3 
9 

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 

NEIV3) 

(tons) 

Total 

County 

2008 SO2

Emissions 

(tons) 

Gila 

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

29,176 

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

- Other point, nonpoint, nonroad, onroad - 343 

Apache 

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

22,583 

No Tucson Electric Power Company Springerville 6,562 

- Other point, nonpoint, nonroad, onroad - 122 

Navajo 

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

19,163 

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

- Other point, nonpoint, nonroad, onroad - 186 

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

- Other point, nonpoint, nonroad, onroad - 1,834 4,718 

Maricopa No Phoenix Sky Harbor International Airport Phoenix 252 

- Other point, nonpoint, nonroad, onroad - 1,389 1,641 

Cochise 

No AZ Electric Power (Apache) Cochise 1,903 

3,081 

No Chemical Lime Company - Douglas Douglas 1,013 

- Other sources (nonpoint, nonroad, onroad) - 165 

Yavapai No Nelson Lime Plant Peach Springs 1,955 

- Other point, nonpoint, nonroad, onroad - 375 2,330 

Pinal - Other point, nonpoint, nonroad, onroad - 381 381 

Mohave - Other point, nonpoint, nonroad, onroad 345 345 

Coconino - Other point, nonpoint, nonroad, onroad - 786 786 

Yuma - Other point, nonpoint, nonroad, onroad 215 215 

La Paz - Other point, nonpoint, nonroad, onroad 41 41 

Santa 

Cruz - Other point, nonpoint, nonroad, onroad 105 105 

Greenlee - Other point, nonpoint, nonroad, onroad 212 212 

Graham - Other point, nonpoint, nonroad, onroad - 48 48 

Total emissions of SO2 are highest in 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 emissions 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 (381 tons in 2008) compared to 

Gila, Apache, and Navajo counties. Gila, Apache, and Navajo counties together comprise 84% of total 

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

comprised 80% of total SO2 emissions from state lands in Arizona in 2008. See Figure 4 for the 

geographic distribution of these stationary sources. One additional source emitted over 100 tons per 
10 

year - the Navajo Generating Station (3,816 tons in 2008) located on tribal lands near the city of Page 

in northern Coconino County, Arizona. The Navajo Generating Station is approximately 240 miles 

north of Freeport-McMoRan Miami Smelter and 270 miles north of the ASARCO LLC – Hayden 

Smelter. 

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 is including 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 NEIV3. 

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

Figure 4 
11 

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. 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).5

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 

 

5

 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 
12 

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 

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 
13 

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

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

 

Figure 6 
14 

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 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. In light of this, we are not yet prepared to conclude whether 

locations outside the particular valleys intersecting at Hayden contribute to the violating monitor’s 

design value. 

Figure 7 
15 

Jurisdictional boundaries 

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 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). 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 Hayden nonattainment area for the 2010 SO2 NAAQS includes the same 

geographic area as the existing nonattainment area for the 1971 SO2 NAAQS without the portion of 

Indian country. 

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 nonattainment area boundaries. No 

areas of Indian country are included in the initial Hayden, Arizona nonattainment area. Figures 

depicting areas of Indian country in this document are intended for illustrative purposes only and are 

not an EPA determination of Indian country status or of any Indian country boundary. 

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 its recommended Hayden nonattainment area is 
16 

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 concurs with the state’s recommendation to initially 

designate a portion of Pinal County and a portion of Gila County as the Hayden, Arizona nonattainment 

area for the 2010 SO2 NAAQS, based on the violating monitor in Hayden, Arizona. No areas of Indian 

country are included in the initial Hayden, Arizona nonattainment area. Areas of Indian country in the 

state of Arizona will be further addressed in a subsequent round of final initial designations. 

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

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

violating the standard as well as areas causing or contributing to the monitored violation, as assessed 

using our five-factor methodology. 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. In light of this, we are not yet prepared to conclude whether locations outside 

the particular valleys intersecting at Hayden contribute to NAAQS exceedances recorded 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 extent of the 

nonattainment area to the nearby river valleys and their surroundings. Based on this information, we 

are not yet prepared to conclude that the emissions from sources located outside the state’s 

recommended boundary contribute to the monitored violation or to other possible violations. We will 

further address such sources and their areas in a subsequent round of final initial designations. The 

state’s recommended boundary for the Hayden nonattainment area is also consistent with the existing 

Hayden nonattainment boundary for the 1971 SO2 NAAQS, without areas of Indian country. All nonIndian country lands in the nonattainment area are under the jurisdiction of ADEQ. 

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

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 in the Hayden, Arizona area. Areas and sources that EPA is not yet 

prepared to conclude are contributing to the monitored violation or to other possible violations are not 

included in this initial nonattainment area. In the future, we will make final initial designation decisions 

for areas in Arizona not included in the nonattainment area designations addressed in this TSD. 

 
17 

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, 2011.6

 

Figure 8 shows the Miami area in Arizona which EPA has initially designated 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. 

 

 

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

Figure 8 
18 

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). 

In February 2013, EPA responded to Governor Brewer’s 2011 recommendation (“120-day” letter to 

Governor Janice K. Brewer from EPA Region 9 Administrator Jared Blumenfeld, February 6, 2013). 

The February 2013 letter notified the Governor of EPA’s intentions regarding designations for the 2010 

SO2 NAAQS. As stated in the letter, EPA intended to agree with the Governor’s recommendations for 

boundaries of the two nonattainment areas the Governor recommended as nonattainment. The Governor 

replied to EPA’s 120-day letter in April 2013 (letter to EPA Region 9 Administrator Jared Blumenfeld 

Figure 9 
19 

from Governor Janice K. Brewer, April 2, 2013). In the reply letter, the Governor reaffirmed the 2011 

recommendations for all areas of the state. 

Based on EPA's technical analysis described below, EPA concurs with the state’s recommendation to 

initially designate a portion of Gila County as nonattainment for the 2010 SO2 NAAQS, as the Miami 

nonattainment area. The county is listed above in Table 1. 

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 Miami nonattainment area and the 

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

The Governor’s recommendation was based on 2007-2009 data from Federal Reference Method (FRM) 

or Federal Equivalent Method (FEM) monitors provided in the state letter to EPA Region 9 

Administrator Jared Blumenfeld from Governor Janice K. Brewer, May 25, 2011.7

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

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

 

 

7

 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. 
20 

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. 

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

show violations of the 2010 SO2 NAAQS. Therefore, as an analytical starting point, some areas in Gila 

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

that the absence of a violating monitor alone is not a sufficient reason to eliminate nearby counties as 

candidates for nonattainment status. This is because the Clean Air Act defines a nonattainment area as 

any area that violates a NAAQS or contributes to a nearby violation.8 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 Table 4 and Figure 9, above). 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. 

 

8

 Section 107(d)(1)(A)(i) of the Clean Air Act defines a nonattainment area as " ... any area that does not meet (or that 

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

standard for the pollutant... " 
21 

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 recorded concentrations in these locations suggest that their design 

values 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 (NEI08V3). Arizona did not provide updated emissions information. 

Figure 10 
22 

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. 

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 V3) 

(tons) 

Total 

County 

2008 SO2

Emissions 

(tons) 

Gila 

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

29,176 

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

- Other point, nonpoint, nonroad, onroad - 343 

Apache 

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

22,583 

No Tucson Electric Power Company Springerville 6,562 

- Other point, nonpoint, nonroad, onroad - 122 

Navajo 

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

19,163 

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

- Other point, nonpoint, nonroad, onroad - 186 

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

- Other point, nonpoint, nonroad, onroad - 1,834 4,718 

Maricopa No Phoenix Sky Harbor International Airport Phoenix 252 

- Other point, nonpoint, nonroad, onroad - 1,389 1,641 

Cochise 

No AZ Electric Power (Apache) Cochise 1,903 

3,081 

No Chemical Lime Company - Douglas Douglas 1,013 

- Other sources (nonpoint, nonroad, onroad) - 165 

Yavapai No Nelson Lime Plant 

Peach 

Springs 1,955 

- Other point, nonpoint, nonroad, onroad - 375 2,330 

Pinal - Other point, nonpoint, nonroad, onroad - 381 381 

Mohave - Other point, nonpoint, nonroad, onroad 345 345 

Coconino - Other point, nonpoint, nonroad, onroad - 786 786 

Yuma - Other point, nonpoint, nonroad, onroad 215 215 

La Paz - Other point, nonpoint, nonroad, onroad 41 41 

Santa 

Cruz - Other point, nonpoint, nonroad, onroad 105 105 

Greenlee - Other point, nonpoint, nonroad, onroad 212 212 

Graham - Other point, nonpoint, nonroad, onroad - 48 48 

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

largest source of SO2 emissions 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 
23 

SO2 from Pinal County are low (381 tons in 2008) compared to Gila, Apache, and Navajo counties. 

Gila, Apache, and Navajo counties together comprise 84% of total SO2 emissions from the state of 

Arizona. The five largest stationary sources in those three counties comprised 80% of total SO2

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

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 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, 

Figure 11 
24 

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, 2012.9

 

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. 

 

9

 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 
25 

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 
26 

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 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 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 Nonattainment Area: 

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

meteorological stations (blue triangles & labels). 

Figure 13 
27 

Jurisdictional boundaries 

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

management purposes, Gila County falls under the jurisdiction of ADEQ. For the 1971 SO2 NAAQS, 

the Miami SO2 nonattainment area was not separately defined but rather that geographic area was 

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

the state of Arizona, EPA reduced the area’s boundaries to include nine townships in and around the 

city of Miami (44 FR 21261, April 10, 1979). See also, 40 CFR section 81.303. 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 nonattainment 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 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 

Figure 14 
28 

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 Miami 

nonattainment area for the 2010 SO2 NAAQS has the same boundaries 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 concurs with the state’s recommendation to initially 

designate a portion of Gila County listed in Table 1 as the Miami, Arizona nonattainment area for the 

2010 SO2 NAAQS, based on the violating monitor in Miami, Arizona. 

The air quality monitor in Miami, Arizona 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 

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

emissions causing the monitored 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. In light of this, we are not yet prepared to conclude whether locations outside the 

particular valley containing Miami contribute to the Miami monitor’s recorded 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 extent of the nonattainment 

area to the nearby river valleys and their surroundings. The nonattainment boundaries recommended by 

the state are therefore expected to contain areas topographically connected with Miami and causing or 

contributing to the monitored violation. We are not yet prepared to conclude that the emissions from 

sources located outside the state’s recommended boundary contribute to the monitored violation or to 

other possible violations, and will further address such sources and their areas in a subsequent round of 

final initial designations. 

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

conclusion is that the boundaries described herein for the Miami, Arizona nonattainment area 

encompass an area that does not meet (or that contributes to ambient air quality in a nearby area that 
29 

does not meet) the 2010 SO2 NAAQS, based on the violating monitor information. No areas of Indian 

country are included in the Miami, Arizona nonattainment area. Areas and sources that EPA is not yet 

prepared to conclude are contributing to the monitored violation or to other possible violations are not 

included in this initial nonattainment area. In the future, we will make final designation decisions for 

areas in Arizona not included in the nonattainment area designations addressed in this TSD.