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1The 1987 PM10 standard included a 24-hour 

(150 micrograms per cubic meter (μg/m3)) and an 

annual standard (50 μg/m3). In 2006, EPA revoked 

the annual standard. See 71 FR 61144 (October 17, 

2006) and 40 CFR 50.6. 

2While most of Pinal County was designated 

‘‘unclassifiable,’’ two PM10 planning areas that 

extend into Pinal County were designated under the 

CAA, as amended in 1990, as ‘‘nonattainment:’’ The 

Phoenix planning area, which includes the Apache 

Junction area within Pinal County; and the Hayden/ 

Miami planning area, which includes the 

northeastern portion of the county. See 56 FR 11101 

(March 15, 1991); 56 FR 56694 (November 6, 1991); 

and 57 FR 56762 (November 30, 1992). In 2007, we 

approved a redesignation request by the State of 

Arizona to split the Hayden/Miami PM10

nonattainment area into two separate PM10

nonattainment areas. See 72 FR 14422 (March 28, 

2007). Today’s proposed action would not affect 

these pre-existing PM10 nonattainment areas. EPA 

codifies area designations in 40 CFR part 81. The 

area designations for the State of Arizona are 

codified at 40 CFR 81.303. 

ENVIRONMENTAL PROTECTION 

AGENCY 

40 CFR Part 81 

[EPA–R09–OAR–2010–0491; FRL–9209–4] 

Designation of Areas for Air Quality 

Planning Purposes; State of Arizona; 

Pinal County; PM10

AGENCY: Environmental Protection 

Agency (EPA). 

ACTION: Proposed rule. 

SUMMARY: Pursuant to section 107(d)(3) 

of the Clean Air Act, EPA is proposing 

to redesignate from ‘‘unclassifiable’’ to 

‘‘nonattainment’’ an area generally 

covering the western half of Pinal 

County, Arizona, for the 1987 national 

ambient air quality standard for 

particles with an aerodynamic diameter 

less than or equal to a nominal 10 

micrometers (PM10), and therefore also 

proposing to revise the boundaries of 

the existing ‘‘rest of state’’ unclassifiable 

area. EPA’s proposal to establish this 

new PM10 nonattainment area, referred 

to as ‘‘West Pinal,’’ is based on numerous 

recorded violations of the PM10 standard 

at various monitoring sites within the 

county. EPA’s proposed boundaries 

would encompass all land 

geographically located within Pinal 

County west of the north-south line 

defined by the boundary between 

Townships 10E and 11E, but excluding 

the main reservation of the Tohono 

O’odham Nation (TON) and excluding 

the Apache Junction portion of the 

existing Phoenix PM10 nonattainment 

area. San Carlos Apache lands, which 

are located in the eastern quarter of the 

county, would be excluded from the 

proposed nonattainment area along with 

the rest of the eastern half of the county. 

If finalized as proposed, the new ‘‘West 

Pinal’’ PM10 nonattainment area would 

be classified as ‘‘moderate’’ by operation 

of law. The effect of this action would 

be to establish and delineate a new PM10

nonattainment area within Pinal County 

and thereby to impose certain planning 

requirements on the State of Arizona to 

reduce PM10 concentrations within this 

area, including, but not limited to, the 

requirement to submit, within 18 

months of redesignation, a revision to 

the Arizona state implementation plan 

that provides for attainment of the PM10

standard as expeditiously as practicable 

but no later than the end of the sixth 

calendar year after redesignation. Lastly, 

EPA is deferring action on the status of 

certain tribal lands located within this 

area, including the tribal lands of the 

Ak-Chin Indian Community and the 

Gila River Indian Community, as well as 

TON’s Florence Village and San Lucy 

Farm, pending further consultation with 

the affected tribes. 

DATES: Any comments must arrive by 

November 1, 2010. 

ADDRESSES: Submit comments, 

identified by docket number EPA–R09– 

OAR–2010–0491, by one of the 

following methods: 

1. Federal eRulemaking Portal: http:// 

www.regulations.gov. Follow the on-line 

instructions. 

2. E-mail: vagenas.ginger@epa.gov. 

3. Mail or deliver: Ginger Vagenas 

(Air-2), U.S. Environmental Protection 

Agency Region IX, 75 Hawthorne Street, 

San Francisco, CA 94105–3901. 

Instructions: All comments will be 

included in the public docket without 

change and may be made available 

online at http://www.regulations.gov, 

including any personal information 

provided, unless the comment includes 

Confidential Business Information (CBI) 

or other information whose disclosure is 

restricted by statute. Information that 

you consider CBI or otherwise protected 

should be clearly identified as such and 

should not be submitted through http:// 

www.regulations.gov or e-mail. http:// 

www.regulations.gov is an ‘‘anonymous 

access’’ system, and EPA will not know 

your identity or contact information 

unless you provide it in the body of 

your comment. If you send e-mail 

directly to EPA, your e-mail address 

will be automatically captured and 

included as part of the public comment. 

If EPA cannot read your comment due 

to technical difficulties and cannot 

contact you for clarification, EPA may 

not be able to consider your comment. 

Docket: The index to the docket for 

this action is available electronically at 

http://www.regulations.gov and in hard 

copy at EPA Region IX, 75 Hawthorne 

Street, San Francisco, California. While 

all documents in the docket are listed in 

the index, some information may be 

publicly available only at the hard copy 

location (e.g., copyrighted material), and 

some may not be publicly available in 

either location (e.g., CBI). To inspect the 

hard copy materials, please schedule an 

appointment during normal business 

hours with the contact listed in the FOR

FURTHER INFORMATION CONTACT section. 

FOR FURTHER INFORMATION CONTACT: 

Ginger Vagenas, EPA Region IX, (415) 

972–3964, vagenas.ginger@epa.gov. 

SUPPLEMENTARY INFORMATION: 

Throughout this document, ‘‘we,’’ ‘‘us’’ 

and ‘‘our’’ refer to EPA. 

Table of Contents 

I. Background 

II. EPA’s Decision to Address PM10

Violations Monitored in Pinal County 

Through Redesignation 

III. State of Arizona’s Recommendation for 

Boundaries for New Nonattainment Area 

IV. EPA’s Review of the State’s 

Recommendation and Rationale for 

Proposed Boundaries 

V. EPA’s Review of Recommendations From 

Affected Indian Tribes 

VI. Proposed Action and Request for Public 

Comment 

VII. Statutory and Executive Order Reviews 

I. Background 

On July 1, 1987, EPA revised the 

national ambient air quality standards 

(NAAQS or ‘‘standards’’) for particulate 

matter (52 FR 24634), replacing total 

suspended particulates as the indicator 

for particulate matter with a new 

indicator called PM10 that includes only 

those particles with an aerodynamic 

diameter less than or equal to a nominal 

10 micrometers.1 In order to attain the 

NAAQS for 24-hour PM10, an air quality 

monitor cannot measure levels of PM10

greater than 150 micrograms per cubic 

meter (μg/m3) more than once per year 

on average over a consecutive three-year 

period. The rate of expected 

exceedances, therefore, indicates 

whether a monitor attains the air quality 

standard. 

Most of Pinal County, Arizona, 

including the area that is the subject of 

today’s action, was included in the ‘‘rest 

of state’’ area, which was designated 

‘‘unclassifiable’’ for PM10 by operation of 

law upon enactment of the 1990 

amendments to the Clean Air Act (CAA 

or ‘‘Act’’).2 See section 107(d)(4)(B)(iii). 

The PM10 designations established by 

operation of law under the CAA, as 

amended in 1990, are known as ‘‘initial’’ 

designations. The CAA grants EPA the 

authority to change the designation of, 

or ‘‘redesignate,’’ such areas in light of 

changes in circumstances. More 

specifically, CAA section 107(d)(3) 

authorizes EPA to revise the designation 

of areas (or portions thereof) on the 


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3 In a letter dated October 14, 2009, EPA notified 

the State of Arizona that the PM10 designation in 

Pinal County should be revised. EPA notified the 

tribal leaders of the Ak-Chin Indian Community, 

Gila River Indian Community, San Carlos Apache 

Tribe, and Tohono O’odham Nation by letters dated 

December 30, 2009. 

basis of air quality data, planning and 

control considerations, or any other airquality-related considerations that EPA 

deems appropriate. Pursuant to CAA 

section 107(d)(3), EPA in the past has 

redesignated certain areas in Arizona to 

nonattainment for the PM10 NAAQS, 

including the Payson and Bullhead City 

areas. See 56 FR 16274 (April 22, 1991); 

and 58 FR 67334 (December 21, 1993). 

II. EPA’s Decision to Address PM10

Violations Monitored in Pinal County 

Through Redesignation 

As noted above, EPA has the authority 

under CAA section 107(d)(3) to 

redesignate areas (or portions thereof) 

on the basis of air quality data, planning 

and control considerations, or any other 

air-quality-related considerations. Last 

year, under CAA section 107(d)(3)(A), 

EPA notified the Governor of Arizona 

and tribal leaders of the four Indian 

Tribes (whose Indian country is located 

entirely, or in part, within Pinal County) 

that the designation for Pinal County, 

and any nearby areas that may be 

contributing to the monitored violations 

in Pinal County, should be revised. Our 

decision to initiate the redesignation 

process stemmed from review of 2006– 

2008 ambient PM10 monitoring data 

from PM10 monitoring stations within 

the county that showed widespread, 

frequent, and in some instances, severe, 

violations of the PM10 standard.3

Table 1, below, presents a summary of 

the latest available quality-assured PM10

monitoring data (2007–2009). A map 

showing the location of the monitors is 

included in our Technical Support 

Document (TSD), contained in the 

docket for this rulemaking. 

TABLE 1—PINAL COUNTY—PM10 AIR QUALITY MONITORING DATA, 2007–2009 

Site name AQS* 

ID 

PM10

Expected 

exceedances** 

2007–2009 

Apache Junction*** .......................................................................................................................................... 04–021–3002–1 0 

Casa Grande ................................................................................................................................................... 04–021–0001–1 0 

04–021–0001–3 4.7 

Combs School (Queen Creek) ........................................................................................................................ 04–021–3009–3 17.6 

Coolidge ........................................................................................................................................................... 04–021–3004–1 2 

Cowtown (southeast of Maricopa) ................................................................................................................... 04–021–3013–1 112.9 

04–021–3013–3 139.8 

Eloy .................................................................................................................................................................. 04–021–3014–1 0 

Mammoth ......................................................................................................................................................... 04–021–3006–1 0 

Marana (Pinal Air Park) ................................................................................................................................... 04–021–3007–1 0 

Maricopa .......................................................................................................................................................... 04–021–3010–3 12.6 

Pinal County Housing/PCH (approx. 11 miles east of Casa Grande) ............................................................ 04–021–3011–1 6.5 

04–021–3011–2 5.9 

04–021–3011–3 15.6 

Riverside (Kearny) ........................................................................................................................................... 04–021–3012–1 0 

Stanfield (approx. 15 miles west of Casa Grande) ......................................................................................... 04–021–3008–1 16.4 

04–021–3008–3 17.8 

Bapchule (Gila River Indian Community monitors) ......................................................................................... 04–021–7004–1 6.6 

04–021–7004–2 7.9 

*AQS (Air Quality System) is an EPA database of ambient air quality. 

**The 24-hour PM10 standard is met when the 3-year average of the expected exceedances is equal to or less than one. 

***The Apache Junction site is located in the existing Phoenix PM10 nonattainment area. 

As shown in Table 1, the data from 

2007–2009 reveal violations at the PM10

monitors located in Queen Creek, Casa 

Grande, Coolidge, Cowtown (which is 

southeast of Maricopa), Maricopa, 

Stanfield, at the Pinal County Housing 

Complex (which is east of Casa Grande, 

roughly half-way between Coolidge and 

Eloy), and within the Gila River Indian 

Reservation. Expected annual 

exceedances (of the 150 μg/m3 24-hour 

standard) at these monitoring sites range 

from two (at Coolidge) to more than 100 

(at Cowtown). (For the purposes of 

comparison, the NAAQS is met when 

the 3-year average of the expected 

exceedances is equal to or less than 

one.) Maximum 24-hour concentrations 

measured at a number of these sites 

(such as Cowtown, Maricopa and 

Stanfield) can be more than two to three 

times the level of the standard. In light 

of the widespread, frequent, and severe 

violations of the PM10 standard 

monitored at various monitoring sites in 

Pinal County, EPA continues to believe 

that the SIP planning and control 

requirements that are triggered by 

redesignation of an area to 

nonattainment for the PM10 NAAQS 

would be the most appropriate means to 

ensure that this air quality problem is 

remedied. 

Section III of this document describes 

the State of Arizona’s recommendation 

with respect to the boundaries of this 

new PM10 nonattainment area, and 

section IV of this document summarizes 

EPA’s review of the State’s 

recommendation and rationale for EPA’s 

proposed boundaries. Section V 

describes the Indian Tribes’ 

recommendations and our 

corresponding responses. Section VI 

describes our proposed action and the 

corresponding CAA planning 

requirements that would thereby be 

triggered. 

III. State of Arizona’s Recommendation 

for Boundaries for New Nonattainment 

Area 

Pursuant to section 107(d)(3)(B) of the 

Act, the Governor of Arizona responded 

to EPA’s October 14, 2009 notification 

that the PM10 designation of Pinal 

County, and any nearby areas that may 

be contributing to violations in Pinal 

County, should be revised. The 

Governor responded in a letter dated 


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4Letter from Jan Brewer, Governor of Arizona, to 

Jared Blumenfeld, Regional Administrator, EPA 

Region IX, dated March 23, 2010. 

5The Governor explicitly excludes Indian 

country, which is appropriate given that the State 

of Arizona is not authorized to administer programs 

under the CAA in the affected Indian country. The 

‘‘backwards L’’ shape of the recommended area is 

partly explained by this exclusion because the 

recommended area partially surrounds Indian 

country. 

6The nine factors considered in ADEQ’s technical 

report are air quality data, emissions data, 

population density and degree of urbanization, 

traffic and commuting patterns, growth rates and 

patterns, meteorology, geography/topography, 

jurisdictional boundaries, and level of control of 

emission sources. 

7PM10 SIP Development Guideline, EPA–450/2– 

86–001, June 1987. 

March 23, 2010 in which the Governor 

recommended a partial-county 

nonattainment area.4

The boundaries of the prospective 

PM10 nonattainment area recommended 

by the Governor of Arizona encompass 

a portion of central and western Pinal 

County, and form an area that resembles 

a backwards ‘‘L.’’ 5 See figure 2 of EPA’s 

TSD for a map of both the State’s 

recommended boundaries as well as 

EPA’s proposed boundaries. The staterecommended area includes all or most 

of the cities of Maricopa, Coolidge, Casa 

Grande and the Pinal County portion of 

the town of Queen Creek, as well as the 

western-most portion of the town of 

Florence and the northern-most portion 

of the city of Eloy. It includes an area 

that at its western-most boundary 

includes nearly all of the City of 

Maricopa. The southern boundary is 

defined by a line that coincides 

approximately with Interstate 8. The 

area continues to the east for 

approximately 35 miles where it 

extends to the north, including portions 

of Florence and Coolidge, and the Pinal 

County portion of Queen Creek, and 

terminates just south of Apache 

Junction. The eastern boundary is 

defined by the north-south line between 

Townships 8E and 9E. The northern 

boundary follows the county line south 

from the Apache Junction area and then 

follows the boundary of the Gila River 

Indian Reservation to close back around 

to the recommended western boundary. 

See the Governor’s March 23, 2010 letter 

for the legal description of the State’s 

recommended boundaries by township 

and range and for an enclosed map 

illustrating this area. 

In support of the Governor’s 

recommendation, on March 26, 2010, 

the Arizona Department of 

Environmental Quality (ADEQ) 

submitted to EPA a technical report 

entitled, ‘‘Arizona Air Quality 

Designations, Technical Support 

Document, Boundary Recommendation 

for the Pinal County 24-hour PM10

Nonattainment Area (March 15, 2010),’’ 

(herein referred to as ADEQ’s ‘‘technical 

report’’). ADEQ’s technical report 

compiles and evaluates information 

addressing nine factors 6 derived from 

and discussed in EPA guidance on 

designation criteria; see citation on page 

2 of ADEQ’s technical report to 

Memorandum from Robert J. Meyers, 

EPA Acting Assistant Administrator, 

‘‘Area Designations for the Revised 24- 

Hour Fine Particle National Ambient 

Air Quality Standard,’’ dated June 8, 

2007. 

ADEQ points to a number of elements 

that it believes support the 

recommended boundaries. Specifically, 

ADEQ claims that its recommended area 

would include: all of the violating 

monitors; the majority of PM10

emissions generated within the county; 

the vast majority of the county’s 

population; the rapidly growing 

urbanized and developed areas, hightraffic Interstate corridors and areas 

with the highest employment densities; 

the significant growth areas along 

Interstates 8 and 10; and the agricultural 

basin where stagnation conditions are 

known to impact PM10 concentrations. 

ADEQ also believes that its 

recommended redesignation would 

maintain jurisdictional cohesiveness. To 

buttress its recommended exclusion of 

eastern Pinal County from the new 

nonattainment area, ADEQ compares 

these factors as they apply to western 

Pinal County with those for eastern 

Pinal County. ADEQ asserts that in 

contrast to the western portion of Pinal 

County, the eastern portion has no 

violating monitors, contains few 

emissions sources (other than certain 

major sources that are already included 

in an existing PM10 nonattainment area), 

is largely undeveloped and has limited 

growth potential. As set forth below in 

more detail, while EPA believes this 

characterization applies to the eastern 

half of Pinal County, EPA also believes 

that the western portion that should be 

redesignated is far more extensive than 

the State’s recommendation. 

IV. EPA’s Review of the State’s 

Recommendation and Rationale for 

Proposed Boundaries 

CAA section 107(d)(1)(A) generally 

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 relevant pollutant. 

Thus, in reviewing the State’s 

recommended boundaries, EPA has 

considered not only areas where 

violations of the relevant NAAQS have 

been monitored, but also that contribute 

to such violations. 

EPA guidance 7 provides for the use of 

‘‘a qualitative analysis of the area of 

representativeness of the monitoring 

station, together with the consideration 

of terrain, meteorology, and sources of 

emissions * * *’’ in defining 

nonattainment area boundaries for 

PM10. Consistent with that guidance, 

EPA generally recommends that States 

identify nonattainment area boundaries 

based on the weight of evidence of the 

following factors and other relevant 

information: 

—Air quality data; 

—Pollutant emissions; 

—Population density and degree of 

urbanization; 

—Traffic and commuting patterns; 

—Growth; 

—Meteorology; 

—Geography and topography; 

—Jurisdictional boundaries; and 

—Level of control of emissions sources. 

See, e.g., Memorandum from Robert J. 

Meyers, EPA Acting Assistant 

Administrator, ‘‘Area Designations for 

the Revised 24-Hour Fine Particle 

National Ambient Air Quality 

Standard,’’ dated June 8, 2007. EPA also 

looks to the same kinds of factors in the 

context of redesignations. See, e.g., 

EPA’s proposed (73 FR 22307, at 22308– 

22310, April 25, 2008) and final 

approval (73 FR 66759, November 12, 

2008) of a state request to redesignate 

the San Joaquin Valley PM10

nonattainment area. In addition, CAA 

section 107(d)(3)(A) allows EPA, in 

redesignating areas to nonattainment, to 

take into consideration ‘‘any other airquality-related considerations.’’ In its 

technical report, ADEQ refers to the 

nine factors in developing the State’s 

recommended boundaries for the new 

PM10 nonattainment area. In the 

following paragraphs, we review and 

evaluate ADEQ’s nine factor analysis. 

Air Quality Data. ADEQ’s technical 

report summarizes 2006–2008 PM10

monitoring data from 12 monitoring 

sites within Pinal County. Most of the 

monitoring sites are located in the west 

central portion of the county (Maricopa, 

Cowtown, Stanfield, Casa Grande, Pinal 

County Housing Complex, and 

Coolidge). Two are located in the 

southern portion (Eloy and Pinal Air 

Park); two are located in the northern 

portion [Apache Junction and Combs 

School (located in Queen Creek)]; and 

two are located in the far eastern portion 

of the county (Riverside and Mammoth). 

The Apache Junction and Riverside 


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monitoring sites are located within 

existing PM10 nonattainment areas. 

Based on 2006–2008 data, ADEQ 

finds six of the monitoring sites to be in 

violation of the PM10 NAAQS. EPA has 

updated this monitoring information by 

reviewing 2007–2009 data. Although we 

find that these data are largely 

consistent with the data presented by 

ADEQ, the more recent data set shows 

seven violating monitors (not counting 

the PM10 monitoring site on the Gila 

River Indian Reservation) rather than 

six. Coolidge is the additional 

monitoring site that is newly violating 

based on the more recent data set. In its 

technical report, ADEQ notes that its 

proposed boundaries include the 

locations of all of the violating monitors 

within Pinal County. While we agree 

that Arizona’s proposed boundaries do 

in fact include all of the violating 

monitors (i.e., other than the monitoring 

site located within the Gila River Indian 

Reservation and those located within 

existing PM10 nonattainment areas), we 

disagree with ADEQ’s contention that 

its proposed boundaries include all 

areas that do not experience violations 

but nonetheless contribute to the 

violations that are recorded at the 

monitoring sites based on an evaluation 

of the other eight factors as discussed in 

the following paragraphs. 

Emissions Data. ADEQ developed an 

annual emissions inventory of PM10

sources in the county for the year 2007 

for the purpose of defining a boundary 

for the new nonattainment area. ADEQ’s 

inventory relies on a number of different 

data sources, assumptions, and methods 

(including EPA’s MOBILE model and 

compilation of emissions factors (AP– 

42)) to calculate annual PM10 emissions 

in the county. ADEQ’s inventory points 

to fugitive emissions from vehicular 

traffic on paved and unpaved roads as 

the single largest source category, 

followed in importance by agricultural 

sources (including concentrated animal 

feeding operations), industrial sources, 

and construction. ADEQ’s technical 

report includes maps that show the 

relative distribution of emissions 

generated within the county using 4- 

kilometer grid cells. See in particular 

the following maps in the State’s 

technical report: Figure 3–3 on page 8 

(all PM10 sources) and figure 3–4 on 

page 11 (paved and unpaved on-road 

sources). The maps show that PM10

emissions in the county are 

concentrated in the western half of the 

county, with the highest emissions 

densities in the west central portion of 

the county. In contrast, the eastern half 

of the county (outside of the existing 

nonattainment areas) is characterized 

predominantly by the lowest category of 

emissions densities (i.e., 0 to 20 tons per 

year per 4-kilometer grid). See page 8 of 

ADEQ’s technical report. 

While EPA finds that the PM10

emissions inventory for Pinal County 

and ADEQ’s corresponding maps are 

helpful in defining the boundaries of the 

new nonattainment area, we do not 

believe that they justify ADEQ’s 

conclusions about its recommended 

boundaries. ADEQ claims that the 

emissions inventory and maps 

demonstrate that sources in the eastern 

and southern regions of the county do 

not ‘‘significantly contribute’’ to 

violations in the other regions of the 

county. See page ES–3 of ADEQ’s 

technical report. EPA notes, however, 

that CAA section 107(d)(1)(A) defines a 

nonattainment area as one that does not 

meet, or that ‘‘contributes to’’ ambient 

air quality in a nearby area that does not 

meet the NAAQS. The definition of 

nonattainment areas is not limited to 

areas that, in ADEQ’s words, 

‘‘significantly’’ contribute to a violating 

area. Moreover, ADEQ’s maps show that 

areas immediately to the east and south 

of the recommended area (but still 

within the western half of the county) 

include the same types of emissions 

sources, with similar emissions 

densities, as those that predominate 

within the recommended area. For 

example, figure 3–3 (page 8 of State’s 

technical report) shows emissions 

densities similar to those estimated 

within the State’s recommended 

boundaries to the east in Coolidge and 

Florence, as well as south to Eloy. In 

addition, figures 3–4, 3–7, and 3–10 (on 

pages 11, 14, and 17, respectively, of the 

State’s technical report) illustrate the 

locations of unpaved roads (with 

average daily traffic volumes greater 

than 100) and show that higher relative 

concentrations of PM10 emissions from 

such sources as vehicle entrainment of 

dust over paved and unpaved roads, 

tilling and harvesting, and concentrated 

animal feeding operations (CAFOs) 

extend to central, and south central 

Pinal County. Thus, the emissions 

inventory data and related maps do not 

support the State’s recommended 

boundaries but rather argue for a larger 

nonattainment area consisting of the 

western half of the county. 

In contrast, EPA’s proposed 

boundaries include all of the areas for 

which emissions data show relatively 

higher PM10 emissions from the types of 

sources contributing the most to the 

overall PM10 emissions inventory. For 

instance, based on the information 

sources described above in the State’s 

technical report, EPA’s proposed 

boundaries include the areas of 

relatively higher emissions densities in 

and around Coolidge, Florence, and 

Eloy that reflect the same types of PM10- 

generating activities (vehicle 

entrainment of dust over paved and 

unpaved roads, tilling and harvesting, 

and CAFOs) as found within the smaller 

nonattainment area boundaries 

recommended by the State. 

Population density, degree of 

urbanization, growth rate and patterns. 

This factor reflects EPA’s belief that the 

size, density, and location of population 

can be indicative of emissions activity 

that contributes to violations of the 

PM10 NAAQS in an area. ADEQ’s 

technical report presents population 

growth and density figures for 

municipalities in Pinal County. The 

data show that Pinal County has grown 

dramatically over the past decade 

(nearly doubling from a population of 

approximately 180,000 in 2000 to nearly 

360,000 in 2008). EPA independently 

collected and reviewed populationrelated information and notes that the 

populations of the largest cities and 

towns in the western half of the county, 

such as (the city of) Maricopa (2008 

population of approximately 46,000), 

Casa Grande (41,000), Apache Junction 

(33,000), Florence (21,000), and Eloy 

(13,000), contrast sharply with much 

smaller populations in the largest cities 

and towns in the eastern half of the 

county, including Superior (3,000), 

Kearny (3,000), and Mammoth (3,000). 

See page 14 of EPA’s TSD. 

ADEQ also submitted maps showing 

population densities both under current 

conditions and projections for the year 

2030 when the population of Pinal 

County is anticipated to exceed 

1,000,000. Under existing conditions, 

higher population densities are found in 

the west central portion of the county, 

but there are also population centers in 

the northern (Apache Junction and 

Queen Creek) and southern portions 

(Eloy) of the county. ADEQ’s maps show 

that future growth is expected to be 

concentrated in the Interstate 8 and 10 

corridors, which extend through the 

west central and southern portions of 

the county, although a certain amount of 

growth is also expected in the Falcon 

Valley area farther to the east. 

In its technical report, ADEQ 

concludes that the eastern and southern 

portions of the county are largely 

undeveloped and have very low 

population densities, and finds that this 

information provides support for the 

State’s recommended boundaries. 

However, like the emissions data 

discussed above, we believe that the 

data do not justify the restricted nature 

of the State’s recommended boundaries, 

which exclude much of the western half 

of the County. Specifically, EPA 


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8On March 22, 2007, EPA adopted a final rule, 

Treatment of Data Influenced by Exceptional 

Events, to govern the review and handling of certain 

air quality monitoring data for which the normal 

believes that the State’s recommended 

exclusion of areas in the eastern and 

southern sections of the western half of 

the county is contradicted by evidence 

showing that land use development in 

Pinal County extends further east and 

south than the State’s recommended 

boundaries. For example, the State’s 

recommended boundaries fail to include 

the agricultural and more urbanized 

uses in and around Eloy and the future 

growth areas along the two Interstate 

corridors. See figures 3–13 and 3–14 

from the State’s technical report. In 

contrast, EPA’s proposed boundaries 

would include all of the western half of 

Pinal County (excluding TON’s main 

reservation and the Apache Junction 

portion of the Phoenix PM10

nonattainment area) and thereby would 

include the areas with relatively higher 

population densities and most of the 

areas where significant levels of growth 

are expected. 

Traffic and commuting patterns. This 

factor considers the commuting patterns 

of residents in, and commuters to, Pinal 

County. More specifically, this factor 

considers the number of commuters in 

each surrounding county who drive to 

Pinal County, the percent of total 

commuters in each county who 

commute to Pinal County, the percent of 

total commuters in each county who 

commute into the statistical area in 

which Pinal County is located, as well 

as the total vehicle miles traveled (VMT) 

for each county. 

ADEQ’s technical report (page 23) 

presents statistics from the 2000 census 

quantifying the number of commuters 

from each county within the State of 

Arizona to jobs within Pinal County, 

and the number of commuters residing 

in Pinal County to jobs in Maricopa and 

Pima counties. The data from 2000 

indicate that approximately 10,000 

commuters, or roughly 20% of total 

commuters to jobs within Pinal County, 

reside outside of Pinal County. 

Conversely, approximately 36,000 

(roughly 80%) of commuters travel 

solely within Pinal County. Almost 80% 

of the out-of-county commuters reside 

to the north in Maricopa County, and 

nearly all remaining out-of-county 

commuters commuting to Pinal County 

reside to the south in Pima County. 

Moreover, nearly 40% of commuters 

residing in Pinal County work in either 

Maricopa or Pima counties, whereas 

60% of commuters residing in Pinal 

County also work in Pinal County. 

EPA independently reviewed these 

same data and observed that the 

principal route for traffic through Pinal 

County (serving in-county as well as 

out-of-county commuters) is Interstate 

10, which bisects the western half of the 

county and connects metropolitan 

Phoenix (largely in Maricopa County) to 

the north with metropolitan Tucson (in 

Pima County) to the south. ADEQ cites 

traffic and commuting patterns as a 

factor supporting the exclusion of the 

eastern half of the county from the new 

nonattainment area. While EPA agrees 

that it is reasonable to distinguish 

between the eastern and western halves 

of the county, EPA believes that the data 

indicate that the entire western half of 

the county, and not a small portion of 

it, as the State recommends, should be 

redesignated to nonattainment. Thus, 

EPA finds that traffic and commuting 

patterns do not make a case for the 

state’s recommendation, but rather lend 

support to the creation of a larger 

nonattainment area generally 

encompassing the western half of the 

County. See figure 3–17 from the State’s 

technical report, which shows much 

higher employment densities 

projections for year 2030 in the western 

half of the county than those in the 

eastern half but which also show higher 

employment densities east and south of 

the State’s recommended boundaries 

(but still within the western half of the 

county). 

Meteorology. Generally, the analysis 

of meteorology looks to wind data for 

evidence that emissions originating 

from areas in certain locations relative 

to violating monitors may be more 

prone to contribute than emissions 

originating from sources located 

elsewhere. ADEQ’s technical report 

describes the dynamics responsible for 

region-wide weather patterns and the 

associated winds blowing across 

Arizona, as well as the frequent 

occurrence of ‘‘drainage’’ winds, which 

occur when large-scale weather 

influences wane. ADEQ describes how 

steep pressure gradients result from 

strong high pressure building over the 

western United States and low pressure 

to the east. As the high pressure builds, 

a steep pressure differential is created 

that causes strong winds over Arizona to 

entrain and transport dust from incounty and out-of-county sources. These 

can cause elevated PM10 concentrations. 

ADEQ also notes however, that not all 

exceedances of the PM10 standard are 

wind-related and that stagnation 

conditions in the fall and winter occur 

when cold air and the absence of winds 

trap ambient PM10 in the lower 

atmosphere. ADEQ notes that the region 

of the county most impacted by 

stagnation conditions is the western 

agricultural basin. 

The State recommends including the 

agricultural basin region of the county 

where stagnation conditions are known 

to impact PM10 concentrations. While 

we agree that the new nonattainment 

area should include the agricultural 

basin region where stagnation 

conditions occur, we find that the 

State’s recommended boundaries do not 

in fact accomplish this. As shown on 

page 14 of the ADEQ’s technical report, 

the agricultural basin region of the 

county, roughly defined based on tilling 

and harvesting emissions within the 

county, lies in the western half of the 

county, and also extends south of 

Interstate 10 towards the southern 

county line. Moreover, as discussed in 

the following paragraph, a review of 

available wind data supports the 

inclusion of areas to the south and east 

of the violating monitors (i.e., beyond 

the State’s recommended boundaries) 

based on the prevalence of winds from 

the southeast quadrant. 

EPA has considered the information 

provided by ADEQ but also reviewed 

available wind data for Pinal County 

and finds that winds are similar 

throughout central and western Pinal 

County in that the predominant wind 

directions are from the southeast 

quadrant. See figure 10 of EPA’s TSD. 

(We note that winds blow out of the 

north and northwest far less frequently, 

making transport of PM10 from the 

metropolitan Phoenix area unlikely 

under most circumstances.) In this 

instance, the predominance of southeast 

winds support boundaries that extend 

south and east of the violating monitors 

because PM10 sources, including 

agricultural activities and unpaved 

roads, are found in those directions. 

EPA’s recommended boundaries 

encompass the types of sources that are 

believed to cause or contribute to the 

monitored violations and that are 

located east and south of the violating 

monitors, whereas the State’s 

recommended boundaries largely 

exclude these sources. See figure 2 

(PM10 monitors, ADEQ’s recommended 

nonattainment area boundary, and 

EPA’s proposed nonattainment area 

boundary), figure 4 (Pinal County 

agriculture, cattle operations, and 

unpaved roads), and figure 5 (ADEQ’s 

map illustrating the distribution of 

emissions in Pinal County) from EPA’s 

TSD. 

Lastly, EPA recognizes that high wind 

events do occur in Pinal County, and 

that some of these events may result in 

monitored particulate matter 

exceedances that qualify as caused by 

exceptional events under EPA’s 

exceptional events rule.8 However, as 


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planning and regulatory processes are not 

appropriate. Under the rule, EPA may exclude data 

from use in determinations of National Ambient Air 

Quality Standard (NAAQS) exceedances and 

violations if a state demonstrates that an 

‘‘exceptional event’’ caused the exceedances, and 

satisfies other criteria set forth by the rule. See 72 

FR 13560. 

9The township referred to as Apache Junction 

would be unaffected by our proposed action and 

would remain part of the Phoenix planning area, 

which is designated as a ‘‘serious’’ PM10

nonattainment area. 

ADEQ itself acknowledges, even if EPA 

were eventually to determine that all of 

the exceedances that ADEQ has flagged 

are caused by ‘‘exceptional events,’’ the 

area would still clearly be in violation 

of the PM10 NAAQS. 

Geography/Topography. The 

geography/topography factor evaluates 

physical features of the land that might 

have an effect on the airshed, and 

therefore, on the distribution of 

particulate matter over an area. In its 

technical report, ADEQ describes the 

topography of Pinal County in terms of 

a broad basin, low in elevation (roughly 

1,200 feet in elevation), surrounded on 

all sides by mountain ranges. ADEQ 

finds that topographic considerations 

support the State’s inclusion of the 

basin region of the county, which is 

characterized by open-ended valleys 

with few topographic barriers, within 

the recommended boundaries. 

Conversely, ADEQ finds that 

topographic considerations support the 

State’s exclusion from the 

recommended boundaries of the eastern 

portion of the county, which is 

characterized by rough terrain and steep 

mountain ranges reaching over 7,000 

feet in elevation. 

EPA too has considered topography 

and generally agrees with ADEQ’s 

description of the topography of Pinal 

County. We believe that the various 

mountain ranges found on each side of 

the county inhibit transport of PM10

(which is largely crustal in 

composition—see figure 6 of EPA’s 

TSD) from outside the county to the 

violating monitors within the county. 

Within the county itself, we believe that 

the mountains in the eastern quarter of 

the county, which rise to approximately 

6,000 feet near the eastern borders with 

Gila and Graham counties, inhibit intracounty transport from sources located in 

the eastern quarter to the violating 

monitors. See figure 11 of EPA’s TSD. 

(The portion of the San Carlos Apache 

Reservation that lies within Pinal 

County is located in the eastern quarter 

of the county.) 

However, the existence of the steep 

mountain ranges in the eastern quarter 

of the County does not justify ADEQ’s 

recommendation to exclude from 

redesignation a much larger section of 

the western half of the County. EPA 

believes that, taking other factors into 

account, the western half of the County, 

located in the basin region that features 

few topographic barriers, should be 

redesignated to nonattainment. Indeed, 

it is arguable that topography alone 

would lend support to redesignating a 

far larger area than EPA is proposing, 

one that would encompass the entire 

county, excepting only the eastern 

quarter. However, EPA believes that 

topography when evaluated in the 

context of the various other factors, 

supports redesignation of the western 

half of the county, rather than the much 

more restricted boundaries that ADEQ 

suggests. 

Jurisdictional Boundaries. The 

analysis of jurisdictional boundaries 

evaluates the planning and 

organizational structure of an area to 

determine if the implementation of 

controls in a potential nonattainment 

area can be carried out in a cohesive 

manner. ADEQ’s technical report notes 

the absence of any certified 

metropolitan planning organization 

(MPO) for Pinal County and the 

exclusion of Indian country from the 

State’s recommendation. As such, 

ADEQ concludes that the State’s 

recommended boundaries maintain 

jurisdictional cohesiveness requiring no 

new institutional arrangements for 

accomplishing required tasks. 

EPA also considered the planning and 

organizational structure of the State of 

Arizona and Pinal County (cities, towns, 

and unincorporated areas), but also took 

into account Indian country, to ensure 

that the implementation of controls 

within the prospective nonattainment 

area could be carried out in a cohesive 

manner. ADEQ exercises overall 

jurisdiction over environmental 

programs in the State of Arizona (i.e., 

excluding Indian country). Under state 

law, ADEQ has the responsibility for 

preparing air quality attainment and 

maintenance plans in Pinal County. 

With respect to permitting and 

enforcement, the Pinal County Air 

Quality Control District (AQCD or 

‘‘District’’) has jurisdiction over most 

types of stationary sources operating, or 

proposing to locate, within Pinal 

County, but state law retains ADEQ’s 

statewide jurisdiction over certain types 

of stationary sources (smelters, 

refineries, coal-fired power plants, and 

agricultural operations). Neither ADEQ 

nor the District have jurisdiction within 

Indian country. 

In its technical report, ADEQ notes 

that five cities and towns (Casa Grande, 

Coolidge, Eloy, Florence, and City of 

Maricopa), as well as a portion of a sixth 

(Queen Creek) are located in central and 

western Pinal County. ADEQ indicates 

that the incorporated boundaries of 

these municipalities have been taken 

into account in developing the 

nonattainment area boundaries. 

However, EPA’s review of the 

incorporated boundaries of these 

municipalities (see, e.g., figure 2 of 

EPA’s TSD) shows that the State’s 

recommended boundaries omit portions 

of the City of Maricopa and Coolidge, 

and most of Florence and Eloy. In 

contrast, EPA’s proposed nonattainment 

area boundaries encompass all of these 

cities and towns, where most of the 

county’s population resides. Inclusion 

of entire cities and towns within the 

nonattainment area boundaries would 

facilitate attainment planning to the 

extent that such local governments will 

ultimately be relied upon for 

development and/or implementation of 

specific PM10 control measures. 

Level of Control of Emission Sources. 

The level of control factor looks at the 

emissions controls currently 

implemented in each area. As a general 

matter, most existing and proposed 

stationary sources within Pinal County 

(excluding Indian country) are subject to 

the generally applicable prohibitory 

rules and permitting requirements 

established by the Pinal County AQCD, 

or, in the case of certain types of 

stationary sources (smelters, refineries, 

coal-fired power plants, and agricultural 

operations), State prohibitory rules and 

permitting requirements established by 

ADEQ. 

Pinal County AQCD has established 

rules for dust abatement purposes that 

apply within a subarea of Pinal County 

established under state law (Arizona 

Revised Statutes section 49–541) and 

referred to as ‘‘Area A.’’ Within Pinal 

County, ‘‘Area A’’ generally refers to an 

area encompassing the Pinal County 

portions of Apache Junction and Queen 

Creek. Pinal County has also adopted a 

number of ordinances that are also 

intended to reduce dust generated 

within ‘‘Area A.’’ These include 

ordinances placing restrictions on 

residential fireplaces, leaf blowers, open 

burning, vehicle commute trips, and 

vehicle idling. For one township located 

within ‘‘Area A,’’ the township included 

in the Phoenix Area PM10

nonattainment area (i.e., Township 1 

north, range 8 east; referred to as 

‘‘Apache Junction’’), Pinal County AQCD 

has adopted further dust abatement 

rules.9 The State’s recommended 

boundaries include a portion, but not 

all, of ‘‘Area A.’’ In contrast, EPA’s 

proposed boundaries for the new 

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all of ‘‘Area A,’’ thereby facilitating 

review and modification of these 

existing PM10 emissions controls within 

the broader SIP attainment planning 

context. 

Conclusion. CAA section 107(d)(3)(C) 

provides that after notifying the 

Governor of State of its intent to 

redesignate an area, EPA shall 

promulgate the redesignation, if any, of 

the area or portion thereof, submitted by 

the Governor, ‘‘making such 

modifications as EPA may deem 

necessary. * * *’’ Pursuant to CAA 

section 107(d)(3), we have reviewed the 

State’s recommendation (dated March 

23, 2010) and related technical report 

(submitted on March 26, 2010). 

Both EPA and the State agree that 

sources outside of the county do not 

contribute to PM10 violations at the 

violating monitors within the county, 

and that sources in the eastern half of 

the county do not contribute to the 

violating monitors (which are 

concentrated in the central and western 

portions of the county). But while EPA 

and the State both use the nine-factor 

analysis for evaluation of the 

prospective nonattainment area 

boundaries, we reach quite different 

conclusions. 

As explained above, and more fully in 

EPA’s TSD, EPA does not believe that 

the State’s recommended boundaries 

encompass the full geographic area from 

which emissions-generating activities 

contribute to the monitored PM10

violations. More specifically, we believe 

that the Governor’s recommended 

boundaries, which cut through 

municipalities and contiguous expanses 

of agricultural fields, exclude sources 

that have been identified as dominant 

sources of PM10 and that are 

contributing to elevated levels of PM10

at violating monitors. 

We believe that our proposed 

boundaries, which are defined as all 

land geographically located within Pinal 

County west of the north-south line 

defined by the boundary between 

Townships 10E and 11E, but excluding 

TON’s main reservation and excluding 

the existing Apache Junction portion of 

the existing Phoenix PM10

nonattainment area, encompass the 

areas in which PM10 violations are being 

monitored, as well as the areas that 

contribute to the monitored violations, 

and that they are thus consistent with 

the definition of nonattainment areas in 

CAA section 107(d)(1)(A). Our 

conclusion is based on EPA’s analysis of 

the factors as set forth in the body of this 

document and in further detail in the 

TSD. In sum, we base our proposed 

boundaries on the following 

considerations: (1) Monitored violations 

occur in the west, central and northern 

portions of the western half of the 

county, not in the eastern half (i.e., 

outside of existing PM10 nonattainment 

areas); (2) the emissions from 

agricultural operations, feedlots, dairies, 

and other cattle operations, as well as 

roads, are concentrated in the western 

half of the county; (3) population 

densities are much greater in the 

western half of the county than in the 

eastern half and growth is expected to 

be concentrated primarily along the 

Interstate corridors that extend through 

the western half of the county; (4) 

Interstate 10, which connects Pinal 

County with the employment centers in 

metropolitan Phoenix and Tucson, 

bisects the western half of Pinal County; 

(5) predominant southeasterly winds 

support inclusion of PM10 sources in 

areas to the south and east of the 

violating monitors; (6) the western half 

of Pinal County encompasses the 

incorporated boundaries of all of the 

cities in Pinal County (Apache Junction, 

Casa Grande, Coolidge, Eloy, Maricopa), 

as well as the larger towns (Florence 

and Queen Creek) thereby potentially 

facilitating implementation of future 

control measures; and (7) dust 

abatement measures already in effect in 

‘‘Area A’’ (within Pinal County) can 

readily be applied, as necessary and 

appropriate, throughout the other 

portions of the western half of Pinal 

County. A map comparing the State’s 

recommended boundaries to EPA’s 

proposed boundaries is included as 

figure 2 in our TSD. 

EPA therefore deems it necessary and 

appropriate to propose boundaries that 

differ from the State’s recommended 

boundaries and that we believe better 

satisfy air quality data, planning, control 

and other air-quality-related 

considerations. CAA Section 107(d)(3). 

Under CAA section 107(d)(3)(C), EPA 

must notify the State whenever EPA 

intends to modify State 

recommendations concerning 

boundaries for areas to be redesignated, 

at least 60 days prior to EPA 

promulgation of final redesignations. 

EPA intends to notify the State of 

Arizona of our proposed action soon 

after this notice is signed. 

V. EPA’s Review of Recommendations 

From Affected Indian Tribes 

Ak-Chin Indian Community. The AkChin Indian Community is located in 

western Pinal County, and is included 

in the existing ‘‘rest of state’’ 

unclassifiable area for PM10. The AkChin Indian Community does not 

operate a PM10 monitoring site, but lies 

in proximity to several PM10 monitoring 

sites that do monitor violations of the 

PM10 NAAQS (e.g., the Maricopa and 

Cowtown sites). In a letter dated 

September 2, 2010 the Ak-Chin Indian 

Community responded to EPA’s 

December 30, 2009 letter concerning the 

PM10 designation of Pinal County with 

a recommendation that the Ak-Chin 

lands be designated attainment/ 

unclassifiable. We have offered formal 

consultation to the Ak-Chin Indian 

Community and have decided to defer 

action on redesignation of the Ak-Chin 

Indian Community for PM10 to allow 

time for formal consultation to occur 

and for further consideration of this 

issue as part of that process. If in the 

future EPA decides to take action to 

redesignate the Ak-Chin Indian 

Community, the Agency will do so in a 

separate rulemaking. 

Gila River Indian Community. The 

Gila River Indian Community (GRIC) is 

a community located on 374,000 acres 

in south central Arizona. Approximately 

one-third of GRIC lies within Maricopa 

County and two-thirds lies within Pinal 

County. The Maricopa County portion 

of GRIC is included in the Phoenix Area 

PM10 nonattainment area. The Pinal 

County portion of GRIC is included in 

the existing ‘‘rest of state’’ unclassifiable 

area for PM10. GRIC operates a PM10

monitoring site in the Pinal County 

portion of its lands and GRIC’s monitor 

has recorded a number of PM10

exceedances. See table 1 above in this 

document. However, GRIC has flagged a 

significant number of these exceedances 

as caused by ‘‘exceptional events’’ under 

EPA’s exceptional event rule (50 CFR 

50.14), and EPA has not yet taken action 

to determine whether any of these data 

should be excluded on that basis from 

consideration in a redesignation action. 

In October 2009, EPA approved GRIC’s 

application for treatment in the same 

manner as a state for the purposes of 

CAA section 107(d) air quality 

designations. More recently, we 

proposed approval of GRIC’s submitted 

tribal implementation plan. See 75 FR 

48880, August 12, 2010. 

As noted above, on December 30, 

2009, EPA notified GRIC that the PM10

designation for Pinal County should be 

revised. GRIC first indicated orally, and 

later confirmed in a letter dated May 27, 

2010, that the community would not be 

making a recommendation for PM10

until formal consultation is conducted. 

By letter dated April 30, 2010, EPA 

responded to GRIC’s oral request with 

an offer of formal consultation. As with 

the Ak-Chin Indian Community, we 

have decided to defer action on a 

decision whether to redesignate GRIC to 

allow time for formal consultation to 

occur and for further consideration of 

this issue as part of that process. In 


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addition, the deferral for GRIC will 

provide EPA with the time necessary to 

address the exceptional events issues. If 

in the future EPA decides to undertake 

redesignation of the Pinal County 

portion of the Gila River Indian 

Community, the Agency will do so in a 

separate rulemaking. 

San Carlos Apache Tribe. The San 

Carlos Apache Reservation extends over 

a portion of eastern Pinal County, as 

well as portions of Gila and Graham 

counties. A section of the Pinal County 

portion of the San Carlos Apache 

Reservation lies in the existing Hayden 

PM10 nonattainment area. The rest of the 

Pinal County portion of the reservation 

is located within the ‘‘rest of state’’ 

unclassifiable area for PM10. The San 

Carlos Apache Tribe did not respond to 

EPA’s December 30, 2009 letter 

concerning the PM10 designation in 

Pinal County. 

For the reasons discussed in section 

IV of this document, we believe that 

emissions sources in the eastern half of 

Pinal County do not contribute to 

violations monitored in the western half 

of the county, and thus are proposing 

only that the western half of the county 

(excluding TON’s main reservation and 

the Apache Junction portion of the 

existing Phoenix PM10 nonattainment 

area) be redesignated to nonattainment. 

Given that the San Carlos Tribe’s Indian 

country extends only into far eastern 

Pinal County, we propose to retain the 

Tribe’s current designations for the 

PM10 standard (i.e., a portion remains in 

the existing Hayden PM10

nonattainment area, and a portion 

remains in the existing ‘‘rest of state’’ 

unclassifiable area). 

Tohono O’odham Nation. The 

Tohono O’odham Nation (TON) extends 

over portions of Pima, Maricopa and 

Pinal counties. TON’s main reservation 

covers much of southwestern Pinal 

County and extends over portions of 

Pima and Maricopa counties. TON’s 

lands also include a small area 

(approximately 25 acres), known as 

Florence Village, which is located 

approximately two miles west of the 

town of Florence in central Pinal 

County, and a 3,200-acre parcel east of 

the main reservation called San Lucy 

Farm. With the exception of a small 

portion of TON included within the 

existing Rillito PM10 nonattainment area 

(which is located in Pima County), TON 

is included in the ‘‘rest of state’’ 

unclassifiable area for PM10. 

In a letter dated February 11, 2010, 

TON responded to EPA’s December 30, 

2009 letter concerning the PM10

designation in Pinal County with a 

recommendation that the TON land 

within Pinal County be designated 

attainment/unclassifiable for PM10. With 

respect to the main reservation in 

southwestern Pinal County, we agree 

with TON’s recommendation and are 

proposing a nonattainment area with 

boundaries that exclude TON’s main 

reservation. We agree with TON’s 

recommendation in this regard because 

(1) the closest violating monitors 

(Stanfield and Casa Grande) are located 

in the midst of the county’s agricultural 

basin, well north of TON’s main 

reservation; (2) the types of emissions 

sources believed to be responsible for 

the PM10 violations, such as agricultural 

operations, feedlots, and dairies (see 

figure 4 of EPA’s TSD), as well as roads, 

are largely absent from TON; (3) the 

population density of TON is very low, 

and is an order of magnitude less than 

the average population density of Pinal 

County (see table 5 of EPA’s TSD); and 

(4) TON is a separate sovereign not 

subject to state or county jurisdiction 

thereby complicating planning and 

implementation issues. We conclude 

therefore that TON’s main reservation is 

not contributing to the PM10 violations 

monitored elsewhere in Pinal County 

and propose to exclude TON from the 

new nonattainment area. Under this 

proposal, the designation of TON’s main 

reservation would remain unchanged, 

i.e., it would remain part of the ‘‘rest of 

state’’ unclassifiable area for PM10.

As to Florence Village and San Lucy 

Farm, EPA is deferring redesignation to 

allow for further consultation with 

TON. If in the future EPA decides to 

take action to redesignate TON’s 

Florence Village and San Lucy Farm, 

the Agency will do so in a separate 

rulemaking. 

VI. Proposed Action and Request for 

Public Comment 

Pursuant to section 107(d)(3) of the 

Clean Air Act and based on our 

evaluation of air quality data, planning, 

control and other air-quality-related 

information and considerations, and our 

review of the Governor’s 

recommendation, EPA is proposing to 

redesignate from ‘‘unclassifiable’’ to 

‘‘nonattainment’’ an area generally 

covering the western half of Pinal 

County, Arizona, for the 1987 PM10

NAAQS and therefore to revise the 

boundaries of the existing ‘‘rest of state’’ 

unclassifiable area. EPA’s proposal to 

establish this new PM10 nonattainment 

area, referred to as ‘‘West Pinal,’’ is based 

on numerous recorded violations of the 

PM10 standard at various monitoring 

sites within the county, and on the other 

grounds set forth in this document and 

in the TSD. 

EPA’s proposed boundaries for the 

nonattainment area would encompass 

all of the area recommended by the 

State of Arizona, but would extend 

further to the east and south, and to a 

lesser degree, to the north and west. 

EPA’s proposed boundaries would 

encompass all land geographically 

located within Pinal County west of the 

north-south line defined by the 

boundary between Townships 10E and 

11E, but excluding TON’s main 

reservation and excluding the Apache 

Junction portion of the existing Phoenix 

PM10 nonattainment area. If finalized as 

proposed, the new ‘‘West Pinal’’ PM10

nonattainment area would be classified 

as ‘‘moderate’’ by operation of law. See 

figure 2 of EPA’s TSD for a map 

showing EPA’s proposed boundaries. 

We believe that our proposed 

boundaries as described above 

encompass the areas in which PM10

violations are being monitored, as well 

as the areas that contributes to the 

monitored violations, and that they are 

thus consistent with the definition of 

nonattainment areas in CAA section 

107(d)(1)(A). Our conclusion is based on 

EPA’s analysis of the factors as set forth 

in the body of this document and in 

further detail in the TSD. We find 

support for our proposed boundaries 

based on the following considerations: 

(1) Monitored violations occur in the 

west, central and northern portions of 

the western half of the county, not in 

the eastern half (i.e., outside of existing 

PM10 nonattainment areas); (2) the 

emissions from agricultural operations, 

feedlots, dairies, and other cattle 

operations, as well as roads, are 

concentrated in the western half of the 

county; (3) population densities are 

much greater in the western half of the 

county than in the eastern half and 

growth is expected to be concentrated 

primarily along the Interstate corridors 

that extend through the western half of 

the county; (4) Interstate 10, which 

connects Pinal County with the 

employment centers in metropolitan 

Phoenix and Tucson, bisects the 

western half of Pinal County; (5) 

predominant southeasterly winds 

support inclusion of PM10 sources in 

areas to the south and east of the 

violating monitors; (6) the western half 

of Pinal County encompasses the 

incorporated boundaries of all of the 

cities in Pinal County (Apache Junction, 

Casa Grande, Coolidge, Eloy, Maricopa), 

as well as the larger towns (Florence 

and Queen Creek) thereby potentially 

facilitating implementation of future 

control measures; and (7) dust 

abatement measures already in effect in 

‘‘Area A’’ (within Pinal County) can 

readily be applied, as necessary and 

appropriate, throughout the other 


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portions of the western half of Pinal 

County. 

EPA has determined that activities 

occurring on the main Tohono O’odham 

Nation (TON) reservation are not 

causing or contributing to violations 

occurring in Pinal County and we are 

therefore proposing to exclude the main 

TON reservation from the new 

nonattainment area. San Carlos Apache 

lands, which are located in the eastern 

quarter of the county, would be 

excluded from the proposed 

nonattainment area along with the rest 

of the eastern half of the county. EPA is 

deferring its decision regarding 

redesignation of the Ak-Chin and Gila 

River Indian Community lands, as well 

as TON’s Florence Village and San Lucy 

Farm, pending consideration of issues 

unique to tribal lands, completion of 

formal consultation with the tribal 

governments, and (in the case of GRIC) 

consideration of exceptional events 

flags. The existing Phoenix PM10

nonattainment area (including the 

Apache Junction portion of western 

Pinal County) would be unaffected by 

this action. 

Areas redesignated as nonattainment, 

as proposed herein, are subject to the 

applicable requirements of part D, title 

I of the Act and will be classified as 

moderate by operation of law (see 

section 188(a) of the Act). Within 18 

months of the redesignation, the State is 

required to submit to EPA an 

implementation plan for the area 

containing, among other things, the 

following requirements: (1) Provisions 

to assure that reasonably available 

control measures (including reasonably 

available control technology) are 

implemented within 4 years of the 

redesignation; (2) a permit program 

meeting the requirements of section 173 

governing the construction and 

operation of new and modified major 

stationary sources of PM10; (3) 

quantitative milestones which are to be 

achieved every 3 years until the area is 

redesignated attainment and which 

demonstrates reasonable further 

progress, as defined in section 171(1), 

toward timely attainment; and (4) either 

a demonstration (including air quality 

modeling) that the plan will provide for 

attainment of the PM10 NAAQS as 

expeditiously as practicable, but no later 

than the end of the sixth calendar year 

after the area’s designation as 

nonattainment, or a demonstration that 

attainment by such date is impracticable 

(see, e.g., section 188(c), 189(a), 189(c), 

and 172(c) of the Act). We have issued 

detailed guidance on the statutory 

requirements applicable to moderate 

PM10 nonattainment areas [see 57 FR 

13498 (April 16, 1992), and 57 FR 18070 

(April 28, 1992)]. 

If we finalize the proposed 

redesignation, the State would also be 

required to submit contingency 

measures (for the new PM10

nonattainment area), pursuant to section 

172(c)(9) of the Act, which are to take 

effect without further action by the State 

or EPA, upon a determination by EPA 

that an area has failed to make 

reasonable further progress or attain the 

PM10 NAAQS by the applicable 

attainment date (see 57 FR 13510– 

13512, 13543–13544). The EPA is 

proposing to establish a deadline for 

submission of contingency measures as 

called for in section 172(b) of the Act to 

coincide with the submittal date 

requirement for the other SIP elements 

discussed above, i.e., 18 months after 

redesignation. Lastly, any new PM10

nonattainment area would be subject to 

EPA’s general and transportation 

conformity regulations (40 CFR part 93, 

subparts A and B) upon the effective 

date of redesignation. See section 176(c) 

of the Act. 

We will accept comments from the 

public on this proposal for thirty days 

from the date of publication of this 

notice, and will consider any relevant 

comments in taking final action on 

today’s proposal. 

VII. Statutory and Executive Order 

Reviews 

A. Executive Order 12866, Regulatory 

Planning and Review 

Under Executive Order 12866 (58 FR 

51735, October 4, 1993), EPA has 

determined that the redesignation to 

nonattainment proposed today, as well 

as the establishment of SIP submittal 

schedules, would result in none of the 

effects identified in Executive Order 

12866, section 3(f). Under section 

107(d)(3) of the Act, redesignations to 

nonattainment are based upon air 

quality considerations. The proposed 

redesignation, based upon air quality 

data showing that West Pinal is not 

attaining the PM10 standard and upon 

other air-quality-related considerations, 

does not, in and of itself, impose any 

new requirements on any sectors of the 

economy. Similarly, the establishment 

of new SIP submittal schedules would 

merely establish the dates by which 

SIPs must be submitted, and would not 

adversely affect entities. 

B. Paperwork Reduction Act 

This action does not impose an 

information collection burden under the 

provisions of the Paperwork Reduction 

Act, 44 U.S.C. 3501 et seq. Burden is 

defined at 5 CFR 1320.3(b). 

C. Regulatory Flexibility Act 

Under the Regulatory Flexibility Act 

(RFA), 5 U.S.C. 601 et. seq., a 

redesignation to nonattainment under 

section 107(d)(3), and the establishment 

of a SIP submittal schedule for a 

redesignated area, do not, in and of 

themselves, directly impose any new 

requirements on small entities. See MidTex Electric Cooperative, Inc. v. FERC, 

773 F.2d 327 (DC Cir. 1985) (agency’s 

certification need only consider the 

rule’s impact on entities subject to the 

requirements of the rule). Instead, this 

rulemaking simply proposes to make a 

factual determination and to establish a 

schedule to require the State to submit 

SIP revisions, and does not propose to 

directly regulate any entities. Therefore, 

pursuant to 5 U.S.C. 605(b), EPA 

certifies that today’s proposed action 

does not have a significant impact on a 

substantial number of small entities 

within the meaning of those terms for 

RFA purposes. 

D. Unfunded Mandates Reform Act 

Under Title II of the Unfunded 

Mandates Reform Act of 1995 (UMRA), 

Public Law 104–4, EPA has concluded 

that this proposed rule is not likely to 

result in the promulgation of any 

Federal mandate that may result in 

expenditures of $100 million or more 

for State, local or tribal governments in 

the aggregate, or for the private sector, 

in any one year. It is questionable 

whether a redesignation would 

constitute a Federal mandate in any 

case. The obligation for the state to 

revise its State Implementation Plan that 

arises out of a redesignation is not 

legally enforceable and at most is a 

condition for continued receipt of 

federal highway funds. Therefore, it 

does not appear that such an action 

creates any enforceable duty within the 

meaning of section 421(5)(a)(i) of UMRA 

(2 U.S.C. 658(5)(a)(i)), and if it does the 

duty would appear to fall within the 

exception for a condition of Federal 

assistance under section 421(5)(a)(i)(I) of 

UMRA (2 U.S.C. 658(5)(a)(i)(I). 

Even if a redesignation were 

considered a Federal mandate, the 

anticipated costs resulting from the 

mandate would not exceed $100 million 

to either the private sector or State, local 

and tribal governments. Redesignation 

of an area to nonattainment does not, in 

itself, impose any mandates or costs on 

the private sector, and thus, there is no 

private sector mandate within the 

meaning of section 421(7) of UMRA (2 

U.S.C. 658(7)). The only cost resulting 

from the redesignation itself is the cost 

to the State of Arizona of developing, 

adopting, and submitting any necessary 


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SIP revision. Because that cost will not 

exceed $100 million, this proposal (if it 

is a federal mandate at all) is not subject 

to the requirements of sections 202 and 

205 of UMRA (2 U.S.C. 1532 and 1535). 

EPA has also determined that this 

proposal would not result in regulatory 

requirements that might significantly or 

uniquely affect small governments 

because only the State would take any 

action as result of today’s rule, and thus 

the requirements of section 203 (2 

U.S.C. 1533) do not apply. 

E. Executive Order 13132, Federalism 

Executive Order 13132 requires EPA 

to develop an accountable process to 

ensure ‘‘meaningful and timely input by 

State and local officials in the 

development of regulatory policies that 

have federalism implications.’’ This rule 

will not have substantial direct effects 

on the States, on the relationship 

between the national government and 

the States, or on the distribution of 

power and responsibilities among the 

various levels of government, as 

specified in Executive Order 13132, 

because it merely proposes to 

redesignate an area for Clean Air Act 

planning purposes and does not alter 

the relationship or the distribution of 

power and responsibilities established 

in the Clean Air Act. Thus, the 

requirements of section 6 of the 

Executive Order do not apply to this 

rule. 

F. Executive Order 13175, Coordination 

With Indian Tribal Governments 

Executive Order 13175, entitled 

‘‘Consultation and Coordination with 

Indian Tribal Governments’’ (65 FR 

67249, November 9, 2000), requires EPA 

to develop an accountable process to 

ensure ‘‘meaningful and timely input by 

tribal officials in the development of 

regulatory policies that have tribal 

implications.’’ The area proposed for 

redesignation does not yet include, and 

EPA is deferring action on the Ak-Chin 

Indian Reservation, the Pinal County 

portion of the Gila River Indian 

Reservation, and TON’s Florence Village 

and San Lucy Farm. In formulating its 

further action on these areas, EPA has 

been communicating with and plans to 

continue to consult with representatives 

of the Tribes, as provided in Executive 

Order 13175. Accordingly, EPA has 

addressed Executive Order 13175 to the 

extent that it applies to this action. 

G. Executive Order 13045, Protection of 

Children From Environmental Health 

Risks and Safety Risks 

This proposed rule is not subject to 

Executive Order 13045 (‘‘Protection of 

Children from Environmental Health 

Risks’’) (62 FR 19885, April 23, 1997), 

because it is not an economically 

significant regulatory action based on 

health or safety risks. 

H. Executive Order 13211, Actions That 

Significantly Affect Energy Supply, 

Distribution, or Use 

This rule is not subject to Executive 

Order 13211, ‘‘Actions Concerning 

Regulations That Significantly Affect 

Energy Supply, Distribution, or Use’’ (66 

FR 28355, May 22, 2001) because it is 

not a significant regulatory action under 

Executive Order 12866. 

I. National Technology Transfer and 

Advancement Act 

Section 12 of the National Technology 

Transfer and Advancement Act 

(NTTAA) of 1995 requires Federal 

agencies to evaluate existing technical 

standards when developing a new 

regulation. The EPA believes that the 

requirements of NTTAA are 

inapplicable to this action because they 

would be inconsistent with the Clean 

Air Act. 

J. Executive Order 12898, Federal 

Actions To Address Environmental 

Justice in Minority Populations and 

Low-Income Populations 

Today’s action proposes to 

redesignate an area to nonattainment for 

an ambient air quality standard. It will 

not have disproportionately high and 

adverse effects on any communities in 

the area, including minority and lowincome communities. 

List of Subjects in 40 CFR Part 81 

Environmental protection, Air 

pollution control, Intergovernmental 

relations, National parks, Particulate 

Matter, Wilderness areas. 

Authority: 42 U.S.C. 7401 et seq. 

Dated: September 21, 2010. 

Jared Blumenfeld, 

Regional Administrator, Region IX. 

[FR Doc. 2010–24683 Filed 9–30–10; 8:45 am] 

BILLING CODE 6560–50–P 

ENVIRONMENTAL PROTECTION 

AGENCY 

40 CFR Part 261 

[EPA–R06–RCRA–2010–0066; SW FRL– 

9208–6] 

Hazardous Waste Management 

System; Identification and Listing of 

Hazardous Waste; Proposed Rule 

AGENCY: Environmental Protection 

Agency (EPA). 

ACTION: Proposed rule. 

SUMMARY: EPA is proposing to grant a 

petition submitted by Exxon Mobil 

Beaumont Refining and Supply 

Company—Beaumont Refinery 

(Beaumont Refinery) to exclude (or 

delist) a certain solid waste generated by 

its Beaumont, Texas, facility from the 

lists of hazardous wastes. EPA used the 

Delisting Risk Assessment Software 

(DRAS) Version 3.0 in the evaluation of 

the impact of the petitioned waste on 

human health and the environment. 

DATES: Comments must be received on 

or before November 1, 2010. 

ADDRESSES: Submit your comments, 

identified by Docket ID No. EPA–R06– 

RCRA–2010–0066 by one of the 

following methods: 

1. Federal eRulemaking Portal: 

http://www.regulations.gov: Follow the 

on-line instructions for submitting 

comments. 

2. E-mail: peace.michelle@epa.gov. 

3. Mail: Michelle Peace, 

Environmental Protection Agency, 

Multimedia Planning and Permitting 

Division, RCRA Branch, Mail Code: 

6PD–C, 1445 Ross Avenue, Dallas, TX 

75202. 

4. Hand Delivery or Courier. Deliver 

your comments to: Michelle Peace, 

Environmental Protection Agency, 

Multimedia Planning and Permitting 

Division, RCRA Branch, Mail Code: 

6PD–C, 1445 Ross Avenue, Dallas, TX 

75202. The Regional Office official 

hours of business are Monday through 

Friday, 8:30 a.m. to 4:30 p.m. excluding 

Federal holidays. 

Please see the direct final rule which 

is located in the Rules section of this 

Federal Register for detailed 

instructions on how to submit 

comments. 

FOR FURTHER INFORMATION CONTACT: For 

further technical information 

concerning this document or for 

appointments to view the docket or the 

Beaumont Refinery facility petition, 

contact Michelle Peace, Environmental 

Protection Agency, Multimedia 

Planning and Permitting Division, 

RCRA Branch, Mail Code: 6PD–C, 1445 

Ross Avenue, Dallas, TX 75202, by 

calling (214) 665–7430 or by e-mail at 

peace.michelle@epa.gov. 

SUPPLEMENTARY INFORMATION: In the 

Final Rules section of this Federal 

Register, EPA is approving Exxon 

Mobil’s delisting petition as a direct 

final rule without prior proposal 

because the Agency views this as a 

noncontroversial submittal and 

anticipates no adverse comments. A 

detailed rationale for the approval is set 

forth in the direct final rule. If no 

adverse comments are received in 


jlentini on DSKJ8SOYB1PROD with PROPOSALS