Response to Comments 

on the  

Proposed Action to  

Redesignate West Pinal County to Nonattainment  

for the  

1987 24‐hour PM10 National Ambient Air Quality Standard 

Office of Air Planning 

Air Di ision 

Environmental Protection Agency – Region 9 

v

May 2012 
ii

List of Acronyms and Abbreviations 

ADEQ:  Arizona Department of Environmental Quality 

Ak­Chin: Ak‐Chin Indian Community  

APS: Arizona Public Service Company  

AZMET:  Arizona Meteorological Network 

CAA:  Clean Air Act  

EPA:  United States Environmental Protection Agency 

GRIC:  Gila River Indian Community  

NAAQS:  national ambient air quality standard  

NEI:  national emissions inventory 

PCAQ:  Pinal County Air Quality Control District   

PM10:  particulate matter 10 microns and smaller in size  

RTC:  response to comments document  

TON:  Tohono O’odham Nation  

TSD:  technical support document  

 
iii

Response to Comments on the Proposed Action to  

Redesignate West Pinal County to Nonattainment  

for the 1987 24­hour PM10 National Ambient Air Quality Standard

Table of Contents

I.  Introduction and Background 

II.  Response to Comments Received on the Proposed Action 

III.  Final Action 

IV.  List of Comment Letters Received 
1

Response to Comments on the Proposed Action to Redesignate West Pinal County to 

Nonattainment for the 1987 24-hour PM10 National Ambient Air Quality Standard 

I.  INTRODUCTION AND BACKGROUND

Pursuant to section 107(d)(3) of the Clean Air Act (CAA), the Environmental Protection 

Agency (EPA)1 may notify the governor of any state that available information indicates 

that the designation of any area should be revised.  Based on monitoring data that indicated 

persistent violations of the 1987 24‐hour national ambient air quality standard (NAAQS) 

for particulate matter 10 microns and smaller in size (PM10), EPA notified the Governor of 

Arizona and tribal leaders for the Ak‐Chin Indian Community (Ak‐Chin), the Gila River 

Indian Community (GRIC), the San Carlos Apache Tribe, and the Tohono O’odham Nation 

(TON) that it was initiating the process to redesignate to nonattainment areas that were 

violating the standard, along with any nearby areas that could be causing or contributing to 

those violations.2  EPA requested recommendations for the redesignation by February 11, 

2010, consistent with the timelines set out in the CAA.   

The Governor of Arizona responded to EPA’s notification that the PM10 designation of Pinal 

County, and any nearby areas that might be contributing to violations in Pinal County, 

should be revised, with a recommendation for a partial‐county nonattainment area.3  The 

Governor’s letter was followed by a letter from the Arizona Department of Environmental 

Quality (ADEQ)4 transmitting Arizona’s justification for its recommended boundary 

(herein referred to as the “technical report”).

The TON5 and the Ak‐Chin6 responded to EPA’s letter concerning the PM10 designation in 

Pinal County with recommendations that their lands be designated 

attainment/unclassifiable for PM10. The San Carlos Apache Tribe and GRIC did not submit 

recommendations. 

After reviewing the recommendations we received and evaluating air quality data, 

planning, control and other air‐quality‐related considerations, EPA proposed boundaries 

that differed from the State’s recommended boundaries and that we believed better met 

the provisions of  CAA Section 107(d)(3). See 75 FR 60680, October 1, 2010. As explained 

                                                          

1  Throughout this document, the terms “we,” “us,” and “our” mean U.S. EPA.

2  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. 3  Letter from Jan Brewer, Governor of Arizona, to Jared Blumenfeld, Regional Administrator, EPA Region 9, 

dated March 23, 2010.

4  Letter from Benjamin H. Grumbles, Director, Arizona Department of Environmental Quality, to Laura Yoshii, 

Acting Regional Administrator, U.S. EPA Region 9 (March 26, 2010).

5  Letter from Ned Norris Jr., Chairperson, Tohono O’odham Nation to Jared Blumenfeld, Regional 

Administrator, U.S. EPA Region 9 (February 11, 2010).

6   Letter from Louis J. Manuel, Jr., Chairman, Ak‐Chin Indian Community, to Jared Blumenfeld, Regional 

Administrator, U.S. EPA Region 9 (September 2, 2010).
2

                                                           

in our proposal, and more fully in our technical support document7 (TSD), EPA concluded 

that the State’s recommended boundaries do not encompass the full geographic area from 

which emissions‐generating activities contribute to the monitored PM10 violations. EPA 

proposed 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.  We proposed to 

defer designation of the Ak‐Chin and GRIC lands, along with those TON lands located within 

the proposed nonattainment area, pending completion of formal consultation with the 

tribes. See Figure 1 for a comparison of ADEQ’s recommended boundaries for the West 

Pinal PM10 nonattainment area with EPA’s final boundaries for the area. 

This response to comments document (RTC) provides EPA’s full responses to the 

comments received on the October 1, 2010 proposed rulemaking.  EPA received adverse 

comment on the southern and eastern boundaries of our proposed nonattainment area. 

Based on our consideration of the comments, including the building permit data provided 

by Pinal County that documents the extent to which the national recession has slowed 

growth in Pinal County, and on further review of the geographic distribution of sources of 

PM10 , EPA has reduced the size of the nonattainment area relative to the area that EPA 

proposed as nonattainment from approximately 2,060 square miles to approximately 1,325 

square miles, which represents a reduction of approximately 735 square miles (or about 

36%).   

The final boundaries for the nonattainment area encompass all of the area recommended 

by the State of Arizona, but extend farther to the east, west, and south. EPA is modifying its 

proposed boundary to exclude a portion of the Sonoran Desert National Monument 

(including the Table Top Wilderness Area), the Tonto National Forest and Superstition 

Wilderness Area, the Ironwood Forest National Monument, and certain less‐developed 

areas of the eastern and southern portions that we included in the proposed nonattainment 

area.  Table 1 below identifies (by township) the portion of Pinal County, Arizona that EPA 

has designated as not attaining the 1987 24‐hour PM10 NAAQS and compares that area with 

the recommendation submitted by ADEQ. Figure 1 illustrates the information from table 1.  

We were persuaded to revise our proposed boundary by our review of satellite imagery, 

maps of source locations, and ADEQ’s maps illustrating emissions estimates by township, 

which together illuminate land use and emissions. In certain areas (such as Florence, Eloy, 

Picacho Peak, and lands to the south of Interstate 8), the final boundary extends beyond the 

State’s recommended boundary. This was done to include areas that, based on the location 

of sources of PM10 emissions, meteorological data that indicate winds from the southeast 

transport emissions to violating monitors, and topographic information showing a lack of 

geographic barriers, are contributing to air quality at violating monitors. 

Figure 2 compares EPA’s proposed boundaries for the West Pinal PM10 nonattainment area 

with EPA’s final boundaries for the area, and Figure 3 shows EPA’s final boundaries for the 

7 Pinal County, Arizona – Area Redesignation for the 1987 24‐hour PM10 National Ambient Air Quality 

Standard. Technical Support Document, September 21, 2010. 
3

West Pinal PM10 nonattainment area in relation to land use and emissions sources within 

and near the new nonattainment area.  

Table 1. Comparison of Townships Included Within ADEQ’s Recommended Boundaries 

for the West Pinal PM10 Nonattainment Area With Those Included Within EPA’s Final 

Boundaries for the Area8

 

Arizona Recommended 

Nonattainment Area within Pinal 

County 

EPA’s Final Designated 

Nonattainment Area within Pinal 

County – “West Pinal”

T1S, R8E; 

T2S, R8E; 

T3S, R7E – R8E; 

T4S, R3E – R4E (excluding all lands 

within the Gila River Indian and AkChin Indian Communities); 

T4S, R8E (excluding all lands within 

the Gila River Indian Community); 

T5S, R3E – R8E (excluding all lands 

within the Gila River and Ak-Chin 

Indian Communities); 

T6S, R3E – R8E; 

T7S, R3E – R8E, Sections 1-6. 

T1S, R8E; 

T2S, R8E; 

T3S, R7E – R9E; 

T4S, R2E – R4E (excluding all lands 

within the Gila River Indian and 

Ak-Chin Indian Communities); 

T4S, R8E – R10E (excluding all lands 

within the Gila River Indian 

Community); 

T5S, R2E – R10E (excluding all lands 

within the Gila River Indian and 

Ak-Chin Indian Communities); 

T6S, R2E – R8E; 

T7S, R2E – R8E (excluding a portion 

of the Sonoran Desert National 

Monument, including all of the 

Table Top Wilderness Area and all 

lands within the Tohono O’odham 

Nation); 

T8S, R6E – R9E (excluding all lands 

within the Tohono O’odham 

Nation); 

T9S, R7E – R10E (excluding all lands 

within the Tohono O’odham 

Nation). 

                                                            8  Table 1 provides general boundary information and was developed for ease of comparison with 

ADEQ’s recommended boundaries. However, the precise delineation of the final West Pinal PM10

nonattainment area boundaries are set forth at the back of EPA’s Final Rule. 
Figure 1 – Comparison of ADEQ’s Recommended Boundaries for the West Pinal PM10 Nonattainment Area with

the Area 

4
Figure 2 – Comparison of EPA’s Proposed Boundaries for the West Pinal PM10 Nonattainment Area with EPA’s Fin

5
Figure 3 – EPA’s Final Boundaries for the West Pinal PM10 Nonattainment Area With Land Use and Emissions So

6
7

as That Do Not Have Violating Monitors

Comment (2):  Most commenters objected to the inclusion in the nonattainment area of 

locations that have monitors that do not themselves show violations of the standard. Pinal 

County and others argued that the current monitoring data do not justify the inclusion of 

the southern portion of the county in the nonattainment area.  Some commenters believe 

II.  RESPONSE TO COMMENTS RECEIVED ON PROPOSED ACTION

General Comment

Comment (1):  EPA received 11 comments on the proposal. No commenters disagreed 

with the need to redesignate a portion of Pinal County nonattainment for the 1987 24‐hour 

PM10 NAAQS. Most commenters, however, believe the nonattainment area should be 

smaller than that proposed by EPA.  ADEQ requested that EPA reconsider its proposed 

boundaries for the Pinal County PM10 nonattainment area, and stated its belief that 

Arizona’s initial boundary recommendation is consistent with EPA guidance and of 

sufficient size to address sources contributing to NAAQS violations measured in northwest 

Pinal County.  ADEQ believes that EPA should give more credence to ADEQ and Pinal 

County in determining the reasonableness of the boundaries. Pinal County believes that 

EPA has not justified an expanded PM10 nonattainment area in southern Pinal County. The 

City of Casa Grande, Arizona Public Service Company (APS), the Arizona Cotton Growers 

Association, the Arizona Farm Bureau Federation, the Pinal County Farm Bureau, and a 

citizen supported the State’s nonattainment area boundary designation for PM10 and 

believe that the State’s boundary meets all of the criteria required under the CAA. The 

Central Arizona Irrigation and Drainage District does not believe that EPA has fully 

considered the adjustments made as a result of Arizona’s public participation process that 

resulted in a more appropriate boundary recommendation. The citizen commented that 

PA’s extension of the boundary south to the county line is not justified. The Sierra Club 

upported EPA

E

s ’s proposed boundaries.

Response (1):  As described in detail below, based on our consideration of the comments, 

EPA has reduced the eastern and southern extent of the proposed nonattainment area.  The 

final boundaries for the new nonattainment area encompass all of the area recommended 

by the State of Arizona, but extend farther to the east and south, though not as far as 

proposed. We are finalizing the western boundary as proposed. The final nonattainment 

area boundary excludes the Superstition and Table Top Wilderness areas, the Ironwood 

Forest National Monument, and certain less‐developed areas of the eastern and southern 

portions of the proposed nonattainment area and reduces the size of the proposed 

nonattainment area by approximately 735 square miles. See Figure 2 herein for a 

omparison of EPA’s final and proposed boundaries for the West Pinal PM10 nonattainment 

rea. See, for example, EPA’s responses to comments 9, 11, 12, 14 and 15. 

c

a

Air Quality Data

Inclusion of Are
8

and should therefore be excluded from the nonattainment area. 

The Arizona Game and Fish Department believes that rural, undeveloped, and largely 

uninhabited portions of the county are not violating the NAAQS or contributing to 

downwind exceedances, and should therefore be excluded from the nonattainment area. 

he Arizona Farm Bureau Federation expressed concern that including areas that have not 

emonstrated compliance issues would dilute efforts to reach attainment in Pinal County. 

that the nonattainment boundary should encompass only those areas where the data show 

a violation of the PM10 NAAQS.  Several commenters asserted that it is unreasonable to

conclude that an area that is not violating the standard is contributing to the PM10 problem 

in an area that is violating the standard.   Commenters observed that Eloy and Pinal Air 

Park monitors, which are located to the south of Arizona’s recommended nonattainment 

area, do not have any recorded violations. They argued that these monitors would 

“register” transport and violate the standard if winds from the southeast were contributing 

to exceedances at the violating monitors.  The Arizona Cotton Growers Association asserted 

hat EPA’s reliance on wind transport for inclusion of the southern and eastern areas is 

a

t

fatally undercut by the record of clean d ta collected at the Eloy monitor. 

APS stated that ADEQ has recorded PM10 violations at six of the twelve monitors located in 

Pinal County using 2006‐2008 monitoring data.  APS noted that the six monitors are 

clustered together in the agricultural basin of western Pinal County. They observed that the 

other monitors located in the eastern and southern portions of Pinal County have no 

recorded violations. APS argued that the aggregation of the violating monitors in the 

agricultural basin (the western region of Pinal County) clearly demonstrates that sources of 

PM10 located in the agricultural basin, not in the eastern or southern region, are leading to 

the violations.  APS concluded that the State’s recommended boundary includes all of the 

emissions sources that significantly contribute to the monitored PM10 violations. 

The Arizona Farm Bureau Federation stated that, based on 2006‐2008 data, there are four 

monitors that have exceeded the PM10 NAAQS in Pinal County (Cowtown, Stanfield, Pinal 

County Housing, Combs School), all of which are located in the western portion of Pinal 

County, and noted that these four monitors, as well as the monitors in Casa Grande and 

Coolidge, are included in the State’s recommended nonattainment area boundary. 

A citizen supported the State’s recommended southern boundary because the Eloy and 

Pinal Air Park monitors, which lie to the south of the State’s nonattainment area boundary, 

have not measured exceedances. This citizen stated that both of these monitors are likely to 

monitor PM10 concentrations higher than those typically occurring in southern Pinal 

County because on‐road sources are the highest emission category, both monitors are 

located next to I‐10, and the Eloy monitor is in a more urban area that has a higher road 

and population density than the rest of the area. From this information, the commenter 

inferred that, since the rest of the southern portion of the County is less traveled, less 

densely populated, and has fewer roads than the areas surrounding the Eloy and Pinal Air 

Park monitors, the southern portion of the County is in compliance with the PM10 NAAQS 

T

d
9

Response (2):  In establishing nonattainment area boundaries, EPA looks to the definition 

of nonattainment found in CAA section 107(d)(1)(A)(i), which states that such areas 

include "any area that does not meet (or that contributes to ambient air quality in a nearby 

area that does not meet)" the NAAQS.  Thus, a location is subject to designation as 

nonattainment if its emissions contribute to a NAAQS violation, even if it is not the main 

cause of violations, and even if it does not contribute to every measured violation.  It is not 

excluded simply because other locations contribute more, or because there are some 

violations to which the location does not contribute. But a contiguous area within a few 

iles having emissions that can travel to a violating monitor should be included, even if its 

e

m

contribution is smaller than that of locations n arer the monitor.  

In order to violate the NAAQS for 24‐hour PM10, an air quality monitor must 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.  If the rate of expected exceedances is 

greater than 1, the monitor violates the air quality standard. The absence of a violation at 

the Eloy monitor does not preclude the possibility of elevated levels of particulate in the 

vicinity of that monitor or the transport of particulate to another area, even if levels are not 

severe enough and frequent enough to cause a violation at the Eloy monitor itself.  For 

example, on August 16, 2008, the Eloy monitor registered a PM10 level of 109 μg/m3. On 

March 26 and October 4, 2009 the Eloy monitor measured 120 and 153 μg/m3, 

respectively.9 As described more fully in our responses to comments 17‐20, prevailing 

winds and the absence of topographic barriers provide evidence that emissions from 

sources located in the south east portion of the nonattainment area, including Eloy, are 

being transported to the violating monitors.  

Finally, it should be noted that inclusion within the nonattainment area does not 

predetermine the State's control strategy for the area; the degree of emission control 

needed for any given location will be decided in the context of the attainment 

demonstration developed by the State.  Further analysis may confirm that future PM10

NAAQS violations can be prevented by application of controls on those sources the State 

believes to be the main causes of the violations.   

Exceptional Events

Comment (3):  Two commenters noted that some of the measured exceedances have been 

flagged as exceptional events10 and suggested that EPA should not consider monitors to be 

                                                            9 EPA’s regulations define an exceedance of the 1987 24‐hour PM10 NAAQS as a daily value that is 

above the level of the 24‐hour standard (150μg/m3) after rounding to the nearest 10 μg/m3, i.e., values 

ending in 5 or greater are to be rounded up and values ending in 4 or less are to be rounded down. See 40 

CFR 50 Ap ing of 153μg/m3 would be rounded to 150μg/m3 p. K, (a).  As a result, the October 4, 2009 read , a d  n

would not be an exceedance of the standard. 10 On March 22, 2007, EPA adopted a final rule, Treatment of Data Influenced by Exceptional Events,

(EER), to govern the review and handling of certain air quality monitoring data for which the normal planning 

and regulatory processes are not appropriate.  Under the rule, EPA may exclude data from use in 

determinations of NAAQS exceedances and violations if a state demonstrates that an “exceptional event” 
10

                                                                                                                    

violating if all of the exceedances have been flagged as exceptional events.  ADEQ stated 

that, based on its analysis of the most recent monitoring data, if flagged exceptional events 

were excluded from the monitoring record, four monitors (Casa Grande, Combs School, 

Coolidge, and Maricopa) would be attaining the standard.  The City of Casa Grande noted 

that the only exceedances measured within its city limits have been flagged by Pinal County 

as exceptional events, and questioned EPA’s listing of monitors located in Casa Grande and 

the surrounding areas as having violated the PM10 standard. 

ADEQ asserted that the purpose of boundary determinations is to enable the selection and 

implementation of control measures to address stagnation‐ and wind‐driven exceedances 

that do not rise to the level of exceptional events because these events are defined as those 

that overwhelm implemented control measures. Focusing on stagnation‐ and wind‐driven 

M10 concentrations that could be reduced through an effective control strategy supports 

pproval of Ari

P

a zona’s recommended boundary.  

Response (3): Based on the most recent certified data, seven monitors in Pinal County are 

violating the 24‐hour PM10 standard.  Even if EPA had concurred on all of the flags in the 

2009‐2011 time frame, three of Pinal County’s monitors (Stanfield, Pinal County Housing, 

and Cowtown) would still violate the 24‐hour PM10 standard, as shown in Table 2, below. 

Furthermore, as explained above in response to comment (2), 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.  Thus, even if EPA had concurred 

on all the exceptional event flags, and thereby reduced the number of violating monitors, 

the boundaries for the nonattainment area would be the same as finalized today because 

emission sources in the areas surrounding the monitors (Casa Grande, Coolidge, Combs 

School, and Maricopa) that would no longer be violating (i.e., assuming EPA concurrence of 

all of the flagged data) contribute to elevated PM10 levels at the remaining violating 

monitors.  

                                                                           

caused the exceedances.  See 72 FR 13560.
11

Table 2. Expected Exceedances at Selected PM10 Monitoring Sites Within Pinal Cou

Site Name AQS ID 

PM10

Expected Exceedances 

2007-2009 

PM10

Expected Exceedances 

2008-2010 

Expect

All 

Exceedances 

Included 

Excluding 

Flagged 

Events

All 

Exceedances 

Included 

Excluding 

Flagged 

Events

All 

Exceeda

Includ

Casa Grandea 04-021-0001-1 

04-021-0001-3 

0 

4.7 

0 0 

0 

2.7 

0 0 

- 

6.4 

Apache Junctionb 04-021-3002-1 

04-021-3002-3 

0 

- 

0 

- 

0 

- 

0 

- 

1.9 3.4 

Coolidge 04-021-3004-1 2 0 2 0 2 Mammothc 04-021-3006-1 0 0 0 0 - Marana (Pinal Air Park) 04-021-3007-1 0 0 0 0 0 Stanfieldd 04-021-3008-1 

04-021-3008-3 

16.4 17.8 

4.0 4.0 

3.0 9.7 

0 2 

- 

12.7 

Combs School 04-021-3009-3 17.6 3.1 3.1 0 5.8 Maricopa 04-021-3010-3 12.6 1.7 6.5 1 9.9 Pinal County Housing (PCH) 

04-021-3011-1 04-021-3011-2 04-021-3011-3 

6.5 5.9 

15.6 

0 0 

2.7 

4.4 3.9 

11.2 

0 0 

2.7 

10.5 

8 

14.8 

Riversidee 04-021-3012-1 0 0 0 0 - Cowtown 04-021-3013-1 

04-021-3013-3 

112.9 139.8 

112.9 134.7 

65 

86.1 

63 

78.7 

43.2 60.7 

Eloy 04-021-3014-1 0 0 0 0 0 

a Casa Grande monitor 04‐021‐0001‐1 (POC 1) was discontinued in December 2010. Monitor 04‐021‐0001‐3 (POC 3) has been des

quality monitoring station (SLAMS) and serves as the primary monitor for the site.

b Monitor 04‐021‐3002‐3 (POC 3), a continuous monitor (TEOM), was installed at the Apache Junction monitoring site in August 2

monitor (SPM). All PM10 SPMs in Pinal County are R & P TEOM 1400a (A/B) continuous analyzers, EPA designation number EQPM‐1090‐07

Quality‐assured SPMs are comparable to the NAAQS. 40 CFR 58.20 (c) states that “[a]ll data from a SPM using an FRM, FEM, or ARM which 

months is eligible for comparison to the relevant NAAQS...” subject to certain conditions. Except for the Apache Junction SPM, which has n

more than 24 months, all SPM monitors in Pinal County are comparable to the 24‐hour PM10 NAAQS. Also see the Air Quality Data section 

c The Mammoth monitoring site was shutdown in May 2011; therefore, a full year of data is not available for 2011. EPA approved 

February 10, 2012.

d Stanfield monitor 04‐021‐3008‐1 (POC 1) was discontinued in December 2009. Monitor 04‐021‐3008‐1 (POC 3) has been design

the primary monitor for the site.

e The Riverside monitoring site was shutdown in May 2011; therefore, a full year of data is not available for 2011. EPA approved t

10, 2012.
12

Improved Air Quality

Comment (4):  ADEQ observed that the most recent air quality monitoring data show 

considerable progress in reducing 24‐hour PM10 concentrations in Pinal County and that 

there has been a marked decrease in the frequency of exceedances at all monitors in the 

ounty, most notably at the Cowtown monitor.  ADEQ requested that EPA consider these 

mprovements

C

i  when making its final boundary determinations. 

Response (4):  EPA recognizes the improvement in air quality illustrated by the declining 

numbers of exceedances of the PM10 NAAQS as compared to years past.  Recently certified 

data for 2011, however, show that while the Cowtown monitors continue to record this 

downward trend, the number of expected exceedances (not taking into account flagged 

data) has slightly increased at most other monitors. As noted above, the certified data 

indicate that seven monitors continue to violate the standard. Also see Response 3, above.  

Emissions Data

Inventory

Comment (5):  ADEQ stated that the 2007 emissions inventory developed by ADEQ and 

Pinal County Air Quality Control District (PCAQ) is more accurate than the 2005 national 

emissions inventory (NEI) because the 2005 NEI includes emissions from several large‐

scale wildfires that occurred in 2002.  Accordingly, ADEQ believes EPA should have relied 

n Arizona’s inventory for the purpose of developing nonattainment area boundaries in 

inal County. 

o

P

Response (5):  Wildfires accounted for only 2% of the primary PM10 emissions in Pinal 

County, according to the 2005 NEI version 2.  As shown in Table 3 of EPA's TSD, the 2005 

NEI version 2 indicates that the main sources of primary PM10 are paved and unpaved 

roads (collectively referred to as “on‐road” emissions), agriculture, and construction 

activities.  When reviewing emissions, EPA additionally considered ADEQ's preliminary 

2007 PM10 emissions inventory, which ADEQ used in its technical report.  While the NEI 

and ADEQ’s preliminary PM10 emissions inventory disagree on the magnitude of the 

contribution of certain source categories, there is general agreement between the two 

regarding the source categories that contribute the most to the PM10 levels in Pinal County.  

See Tables 3 and 4 of EPA’s TSD. 

These emissions inventories, together with results from speciation analyses projects 

conducted in 2003 and 2009, support EPA's conclusion that unpaved and paved roads, 

construction, agriculture, concentrated animal feeding operations, livestock dust, and some 

stationary sources are responsible for the elevated PM10 levels in Pinal County. 
13

                                                           

Undeveloped lands

Comment (6):  The Arizona Game and Fish Department commented that only areas where 

credible emissions estimates are available should be included in the nonattainment area.  

Because ADEQ had found it difficult to make credible emissions estimates for disturbed 

soils on undeveloped lands and windblown dust in its preliminary inventory, the 

commenter believes that undeveloped lands should be excluded from the nonattainment 

area.  The Sierra Club observed that undisturbed desert areas generate limited dust, but 

ointed out that once the soil is disturbed, and often repeatedly disturbed, it can generate 

nhealthful an

p

u d dangerous levels of particulates. 

Response (6):  Based on the available data, and consistent with our guidance, EPA has 

established a nonattainment area that we believe encompasses the areas in which PM10

violations are being monitored, as well as the areas that contribute to the monitored 

violations, consistent with the definition of nonattainment areas in CAA section 

107(d)(1)(A). We have drawn the boundary to include sources of emissions that are 

contributing to the nonattainment problem and have revised our proposed boundary to 

better exclude areas with relatively low levels of emissions.  The final boundary traces the 

county line in the west, the boundary between State lands and Indian Country along the 

northern edge and in parts of the south. In areas to the east and south, where following a 

jurisdictional boundary would result in the exclusion of areas that are contributing to 

violations or the inclusion of areas that are not contributing to the violations, we have used 

township and range lines to define the boundary. Using this approach, we minimize the 

inclusion of undeveloped lands. We also note that inclusion of an area within the boundary 

does not prejudge the need for controls or regulations that apply to those lands. Arizona 

will be required to develop a plan that results in the attainment of the air quality standard 

for PM10, and the relative contribution of various sources and options for control will be 

considered in that process.  That attainment plan will be subject to public review and 

omment, both at the state level and again when EPA evaluates the plan for approval or 

isapproval as a revision to the Arizona state implementation plan (SIP). 

c

d

Geographic Distribution of Emissions Sources

Comment (7):  A number of commenters objected to EPA’s previously proposed boundary 

because, in their view, sources of PM10 emissions leading to monitored violations are in the 

western regions of Pinal County, not the east or south [of the Governor’s recommended 

nonattainment area16]. They argued that Governor Brewer’s boundary includes all of the 

missions sources that contribute significantly to the PM10 violations plus an adequate 

uffer to the south and east. 

e

b

16 Commenters referring to the “eastern” and “southern” portions of Pinal County appear to be referring to 

the areas to the east and south of the Governor’s recommended nonattainment boundary.  In our TSD and in 

this RTC, EPA’s references to the eastern and western portions of Pinal County mean those portions of Pinal 

County that lie to the east and west of the eastern boundary of EPA’s proposed nonattainment area.
14

 see Response 2. 

Comment (8):  APS argued that the location of the violating monitors and the PM10

concentration readings show that the activities occurring in the agricultural basin are the 

main cause of the violations. APS observed that ADEQ’s 2007 PM10 Emission Inventory 

shows that 95% of PM10 emissions in Pinal County are associated with on‐road vehicle 

travel, agriculture (tilling, harvesting, and animal feeding operations), and construction. 

On‐road vehicle emissions (i.e., vehicle use on paved and unpaved roads) represent 83% of 

the total PM10 emissions. ADEQ’s analysis shows that a significant portion of on‐road 

vehicle travel is in Western Pinal County where most of the county agricultural activities 

are located. In addition, commuting pattern data along the I‐10 corridor in the Case Grande 

area shows that the majority of commuter traffic is to the north toward the Phoenix 

metropolitan area rather than south toward Tucson. From these data, APS concluded that 

Commenters pointed to differences in activity levels and the degree of urbanization in 

areas within and outside the Governor’s recommended boundary and argued that the 

preliminary emissions inventory determined that sources in the eastern and/or southern 

regions of the county do not significantly contribute to violations in other regions of the 

county.    

APS maintained that the State’s recommended boundary designation includes all of the 

emissions sources that significantly contribute to the monitored PM10 violations. It noted 

that ADEQ concluded that the eastern and southern portions of the county are largely 

undeveloped, have a lower population, and thus do not represent major sources of PM10. 

APS concurred with ADEQ’s conclusion and believes that the southern and eastern areas, 

including the areas around Coolidge, Florence, and Eloy, should not be included within the 

onattainment area boundary. They contend that these areas clearly do not contribute the 

M10 nonattain

n

P ment issues in the west. 

Response (7):  Arizona’s preliminary PM10 inventory and the 2005 NEI version 2, along 

with source apportionment studies, identify the sources that contribute to elevated 

concentrations of PM10. These sources include on‐road emissions, cattle operations, 

agriculture and construction. According to ADEQ’s technical report, these sources of PM10

are distributed throughout the western portion of Pinal County, including areas to the east 

and south of the Governor’s recommended boundary. See Figures 3‐3 and 3‐4 of ADEQ’s 

technical report. EPA’s review of meteorological data and topography indicates emissions 

from these areas are sometimes transported to the violating monitors.  The CAA requires 

that nonattainment areas encompass nearby areas that contribute to air quality in the area 

where violations are measured. The statute does not set any “significant contribution” 

threshold for excluding nearby areas that contribute to violations, nor has any commenter 

provided one.  EPA does not believe that the areas to the southeast have a negligible 

contribution to violations. 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 

ontribute to the monitored violations and that are located east and south of the violating 

onitors. Also

c

m
15

the main sources of PM10 emissions are on‐road vehicle travel and agricultural activities, in 

the western/ west central and northern parts of the county where the monitored violations 

have occurred.  

The Farm Bureau contended that the ADEQ inventory data, which it characterized as 

identifying on‐road sources as the major contributor to PM10 emissions in Pinal County, is 

upported by the observation that violating monitors are located in the more densely 

opulated area

s

p s in the western portion of the county.  

Response (8):  As noted in our TSD, the 2003 Source Apportionment Study17 concluded 

that the dominant PM10 source in Pinal County was soil, with the exception of the Cowtown 

monitor, which was significantly influenced by cattle feedlot emissions.  These findings 

were reinforced by information gathered in 2009 during an EPA‐funded RARE project.18

ADEQ’s preliminary inventory and the NEI agree that main sources of primary PM10 are 

paved and unpaved roads (collectively referred to as “on‐road” emissions), agriculture, and 

construction activities. 

APS did not define the geographic extent of the “agricultural basin;” however, we note that 

agricultural operations are widely distributed in the western half of Pinal County and are 

not limited to the area within the Governor’s recommended boundary.  See Figure 3 for a 

map showing EPA’s final boundaries for the West Pinal PM10 nonattainment area and the 

generalized land uses found therein and in the vicinity.  

EPA’s final nonattainment area encompasses the area recommended by the State of 

Arizona, but extends farther to the south and west. The eastern boundary now partially 

coincides with the State’s recommended boundary (the north‐south line defined by the 

boundary between townships 8E and 9E) but extends farther to the east to include the 

Florence area and several nearby townships in order to include significant sources of PM10

emissions19, and, in the southern part of the nonattainment area, to include the Picacho 

eak area where severe dust storms have caused impaired visibility leading to traffic 

ccidents and, 

P

a in some cases, fatalities. 

Comment (9):  A citizen argued that the area to the south of the Governor’s recommended 

boundary, which coincides roughly with Interstate 8 (I‐8), should not be included because 

it is predominantly farmland with almost no residential or industrial areas, and, according 

to Arizona’s preliminary emissions inventory, tilling, harvesting, and agriculture constitute 

4.9% of the inventory. The commenter also asserted that the southern portion of the Pinal 

County should not be included in the nonattainment area because the area has no roads, 

other than I‐10, that lead to any major urban centers, and the monitors near I‐10 in the 

                                                           

17 Pinal County Air Quality Control District Source Apportionment Study: July 29, 2005, page 43. 18 “Chemical Analysis for Source Attribution of Fine and Coarse Particulate Matter in Pinal County, Arizona” 

Andrea L.Clements, Yuling Jia, Matthew P. Fraser, Pierre Herkes, Michael Sundblom, and Paul A. Solomon, 

presentation to American Aerosol Researech Association (AARA) 28 i   th Annual Conference, M nneapolis,

Minnesota, October 26 – 30, 2009.

19 See Figure 3 of this RTC and Appendix B of Arizona’s technical report– ADEQ Maps of PM10 Sources.  
16

southern portion of the county (at Eloy and Pinal Air Park) are not in violation of the PM10

NAAQS. The commenter suggested that EPA has assumed that southern Pinal County 

should be included since it is the same as the area surrounding the Pinal County Housing 

monitor, but noted the conditions at the latter are influenced by significant local sources, 

uch as a dirt race track, county fairgrounds, and concentrated vehicle traffic, that are not 

epresentative

s

r  of conditions in the southern portion of the county. 

Response (9): Based on our review of the comments and the data, including the 

geographic distribution of sources of PM10 and the building permit data provided by Pinal 

County that document the extent to which the national recession has slowed growth in 

Pinal County, we have adopted a more limited expansion of the State‐recommended 

southern boundary than we had proposed. EPA’s inclusion of some area south of Arizona’s 

recommended boundary is rooted in the CAA’s definition of nonattainment area in 

107(d)(A)(1) to include areas that are contributing to air quality at a nearby area that is 

violating. EPA has concluded that there are sources south of I‐8 that are contributing to the 

levels of PM10 measured at the violating monitors. Our conclusion is based in part on the 

presence and proximity of sources in categories shown to contribute to air quality in the 

violating area, as well as on meteorological data indicating transport to those areas where 

violations are being measured. Further, the history of dust storms and resulting traffic 

accidents in the Picacho Peak area, which lies to the southeast of the State’s recommended 

boundary, provides evidence that the disturbed land surface in this area is likely a larger 

contributor to downwind violations than might otherwise be suggested by the aggregate 

emissions and land use data. The CAA does not require a nearby area’s contribution to be 

“significant” to warrant inclusion in the nonattainment area boundaries. See CAA section 

107(d)(1)(A)(i). We also note that recent revisions to emissions factors20 could result in 

reductions to the amount of emissions attributed to on‐road sources. If this is the case, the 

relative percentage contribution of other source categories, including tilling, harvesting 

and agriculture will increase.  

Off­Highway Vehicles

Comment (10):  The Arizona Game and Fish Department argued that because ADEQ’s TSD 

states that off‐highway vehicle emissions are relatively low and there were no grid cells 

ver the 20 ton per year threshold, the nonattainment area boundary should not include 

ndeveloped lan

o

u ds where this type of recreation occurs.

Response (10):  Upon consideration of public comment and further review of the 

geographic distribution of source of emissions, EPA has revised our proposed 

nonattainment area boundary. We have established a final nonattainment area that we 

believe encompasses the areas in which PM10 violations are being monitored, as well as the 

                                                           

oads, Measurement Policy Group, Office of  20 Emission Factor Determination for AP‐42, Section 13.2.1 Paved R

Air Quality Planning and Standards, U.S EPA (January 2011)  

http://www.epa.gov/ttn/chief/ap42/ch13/bgdocs/b13s0201.pdf 
17

areas that contribute to the monitored violations, consistent with the definition of 

nonattainment areas in CAA section 107(d)(1)(A). While this might result in the inclusion 

of some lands where off‐highway vehicle recreation occurs, it does not dictate controls or 

the regulation of emissions generated by such activities. Arizona will be required to 

develop a plan that results in the attainment of the air quality standard for PM10, it will be 

the State’s role to determine the relative contribution of various sources and to consider 

and decide upon options for control.   The State’s attainment plan will be subject to public 

eview and comment, both at the state level and again when EPA evaluates the plan for 

pproval or disapproval as a revision to the Arizona state implementation plan (SIP). 

r

a

Wilderness Areas

Comment (11):  Four commenters objected to the inclusion of the Table Top and 

Superstition Wilderness areas within the nonattainment area, noting that such areas are 

generally closed to mechanized equipment and do not include sources that could be 

contributing to exceedances at the violating monitors. The Arizona Game and Fish 

Department and ADEQ also contended that EPA had not justified its decision to include the 

wilderness areas and the Tonto National Forest in the nonattainment area. The Arizona 

ame and Fish Department requested that EPA remove these areas and other largely 

ndeveloped, ru

G

u ral areas from the nonattainment boundary.  

Response (11):  EPA agrees that, because the wilderness areas and the Tonto National 

Forest are generally closed to mechanized equipment and lack emissions sources, the areas 

do not contribute to violations at monitors elsewhere in Pinal County. As a result, we have 

inalized boundaries that do not include either of the subject wilderness areas or any 

ortion of the Tonto National Forest and that minimize the inclusion of undeveloped land.  

f

p

Population Density and Degree of Urbanization

Comment (12):  Several commenters noted that the area south of Arizona’s recommended 

boundary is sparsely populated.  ADEQ stated that the level of urbanization in the Eloy area 

differs from that in the areas surrounding the violating monitors. ADEQ further argues that 

its position is supported by the 2007 satellite imagery that shows most of Eloy is sparsely 

populated and that the “urbanized” area of the city consists of approximately 1,130 acres. 

Both the Arizona Farm Bureau Federation and the Pinal County Farm Bureau (collectively 

referred to as the Farm Bureau) challenged EPA’s proposed redesignation to 

nonattainment the area surrounding Eloy and running south to Pima County.  The Farm 

Bureau stated that that the population densities in this area are among the lowest in the 

county, and reflect far less human activity than other more populated portions in western 

Pinal County.  The Farm Bureau also asserted that reduced economic activity in this area is 

ndicated by the monitors located in these areas that have recorded attainment with 

AAQS. 

i

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18

                                                        

A citizen stated that the southern portion of the county has the lowest population density 

and degree of urbanization of any of the areas included in EPA’s proposed nonattainment 

area. In support of this assertion, the commenter contrasted Eloy’s density of 225 persons 

per square mile with the next highest settlement density of 929 persons per square mile 

(based on information in ADEQ’s TSD). The commenter contended that including the 

outhern portion of the county in the nonattainment area would serve no practical or 

ublic policy pu

s

p rpose given the small population and clean data. 

Response (12): As noted in our TSD, population density can give an indication of whether 

it is likely that an area is causing or contributing to violations of the 24‐hour PM10 standard, 

particularly in situations where activities correlated with population contribute to overall 

emissions.  In this case, population density was among the factors considered because on‐

road emissions are a significant contributor to PM10 emissions in Pinal County.  

Because on‐road emissions are distributed throughout the western half of Pinal County21, 

and because other sources in the County, including agriculture and cattle operations, which 

are not typically correlated with high population density, are responsible for PM10

emissions, it would be inappropriate to rely on population density alone to determine 

whether an area should be included within the nonattainment boundary.  

Upon further consideration, EPA has determined that certain areas that had been included 

in the proposed nonattainment area, including some areas in the southern portion of Pinal 

County, are unlikely to be causing or contributing to violations of the PM10 NAAQS.  As a 

result, EPA is modifying its proposed boundary to exclude those areas.  See Figure 2, which 

compares EPA’s proposed and final nonattainment area boundaries. Our decision is based 

on the low level or absence of the types of activities that contribute to elevated PM10 levels 

in Pinal County.  However, because of the presence of emissions generating activities in the 

loy area and meteorological data that provide evidence of transport from the south, we 

ave not exclude

E

h d this area. 

Comment (13):  ADEQ argued that population and population density in Florence and Eloy 

is overstated because the numbers include the prison population.

22 According to 

population data from 2008, when the prison population is excluded, the population density 

in Eloy drops from 146.9 to 102.6, and in Florence from 481.9 to 71.9. They argued that 

incarcerated prisoners do not engage in activities that contribute to elevated 

concentrations of PM10. ADEQ asked EPA to reconsider the population densities and 

projections included in its initial boundary recommendation. ADEQ noted that, when the 

population densities are adjusted to exclude prisoners, a comparison of the revised 

population density to those in more urbanized areas of Pinal County with violating 

onitors demonstrates that population‐driven activity levels in the areas of Florence and 

loy are less intense and have not resulted in violations of the PM10 NAAQS. 

m

E

21 See Figure 3‐4 of ADEQ’s technical report, also reproduced in EPA’s TSD as Figure 9. 22 In 2008, 4,868 people were incarcerated in Eloy, and 17,186 people were incarcerated in Florence. 
19

Response (13): EPA agrees that inclusion of prisoners in the calculation of population 

density might skew the results of efforts to draw nonattainment boundaries based solely 

on population density.  However, in this particular case, population density was only one of 

many factors considered.  Because some sources of PM10 in Pinal County (e.g., on‐road 

emissions) may be correlated to a degree with population density, a high population 

density in a locale could weigh in favor of its inclusion in the nonattainment area.    On the 

other hand the emissions inventories and source apportionment studies of Pinal County 

also show that other contributing sources are typically correlated with lower population 

density (agricultural operations, cattle operations). Therefore, while population density 

can be considered in determining the appropriate boundary, low population density alone 

should not in this case be a deciding factor in determining whether to exclude an area from 

the nonattainment area.   

As noted above (response to comment 12), EPA has revised the boundary to exclude 

certain areas that, based on our evaluation of comments and review of satellite imagery, 

are not likely to be contributing to the violations measured in Pinal County.  However, 

because both Florence and Eloy are located in areas that include sources of PM10 that are 

ontributing to elevated emissions levels at violating monitors, we have included them in 

he final nonattainment area. 

c

t

Traffic and Commuting Patterns

Comment (14): Several commenters stated their belief that including the eastern and 

southern portions of the county in the nonattainment area is not justified based on the 

traffic patterns and relatively low concentration of roads in this area. Commenters stated 

that the largest category of PM10 emissions in Pinal County is on‐road sources, and asserted 

that current traffic and commuter–related emissions are centered in the western portions 

of the county, in the more populated regions of Casa Grande and Maricopa.  Another 

commenter noted that the number of commuters traveling between Pima and Pinal 

counties is significantly less than the number traveling between Maricopa and Pinal 

counties, and further contended that the area south of the Governor’s recommended 

nonattainment area is generally not affected by commuting between Pima and Pinal 

counties.  One commenter stated that the area south of I‐8 does not have any roads that 

lead to major urban centers, except for I‐10, and the commenter contended that proximity 

to I‐10 does not cause violations at the Pinal Air Park or Eloy monitors. 

ADEQ cited statistics that indicate the number of commuters traveling between Pima and 

Pinal counties is significantly less than the number traveling between Maricopa and Pinal 

counties, as support for excluding the southern portion of Pinal County from the 

nonattainment area boundary.  ADEQ argued that the area south of Arizona’s 

recommended boundary is sparsely populated, generally unaffected by commuting 

between Pinal and Pima counties, and is not likely to become a major employment center. 

DEQ concluded that the original southern boundary in Arizona’s recommendation is 

ustifiable under these factors. 

A

j
20

APS observed that commuting pattern data along the I‐10 corridor in the Case Grande area 

show that the majority of commuter traffic is to the north toward the Phoenix metropolitan 

area rather than south toward Tucson. It contended that this lends support to the 

conclusion that the main sources of PM10 emissions are on‐road vehicle travel and 

agricultural activities in the western/west central and northern parts of the county where 

the monitored violations have occurred. 

The Farm Bureau pointed to EPA’s data, arguing that they show the majority of commuters 

travel north to the Phoenix Metropolitan area and that far fewer commuters travel through 

the southern part of the county for employment purposes. The Farm Bureau contends this 

supports its argument against including the southern portion of the County in the 

nonattainment area. In addition, the Farm Bureau claimed that the data support Arizona’s 

recommended boundaries, since they show traffic and commuting–related emissions and  

the violating monitors are concentrated in the more populated regions of Casa Grande and 

Maricopa in the western portions of the County. The Farm Bureau contrasted this with the 

ess‐ traveled southern portion of Pinal County, which contains the I‐10 corridor and where 

he monitors (El

l

t oy and Pinal Air Park) located along that corridor do not show violations. 

Response (14):  Although EPA and ADEQ inventories differed with respect to the quantity 

of emissions generated by on‐road sources, there is agreement that this constitutes the 

largest category of PM10 emissions in Pinal County. EPA TSD Figure 8 and ADEQ technical

report Figure 3‐5 illustrate the distribution of commuter traffic and emissions generated by 

traffic on paved roads. Taken together with the overall distribution of on‐road emissions 

shown in ADEQ’s technical report (Figure 3‐4), it is evident that on‐road traffic (including 

paved and unpaved roads) is a significant source of emissions in the western half of Pinal 

County, including areas to the south and east of the Governor’s recommended boundary.   

EPA believes that the distribution of emissions from on‐road traffic requires an expansion 

of Arizona’s recommended boundary; however, upon further review, we have concluded 

that the available data support a modification of our proposed boundary. The final 

nonattainment boundary therefore removes some of the eastern and southern townships 

that had been included in the proposed nonattainment area.  

We were persuaded to revise our proposed boundary by our review of satellite imagery, 

maps of source locations, and ADEQ’s maps illustrating emissions estimates by township, 

which together illuminate land use and emissions. In certain areas (such as Florence, Eloy, 

Picacho Peak, and lands to the south of Interstate 8), the final boundary extends beyond the 

State’s recommended boundary. This was done to include areas that, based on the location 

of sources of PM10 emissions, meteorological data that indicate winds from the southeast 

ransport emissions to violating monitors, and topographic information showing a lack of 

eographic barriers, are contributing to air quality at violating monitors. 

t

g
21

n is justifiable under these factors. 

Response (15):  In weighing growth rates and patterns, EPA considered information 

presented in ADEQ’s technical report, including projected growth in population density and 

employment density.  Figures 3‐14 and 3‐17 of ADEQ’s technical report illustrate the 

southward and eastward expansion of relatively high population and employment 

densities that are expected to occur in the future. While this information provides 

additional justification for EPA’s decision to exclude the eastern half of Pinal County from 

Growth Rates and Patterns

Comment (15):  Several commenters argued that growth forecasts made prior to the 

economic downturn are no longer reliable given current economic conditions, and pointed 

to the uncertainty of future growth. Others noted that actual growth in the area south of the 

Governor’s recommended boundary has been modest, and that it is unlikely to become a 

major employment center.  These commenters questioned EPA’s analysis that future 

employment and population growth in Pinal County justifies including the southern 

portion of the county in the nonattainment area.   

PCAQ stated that foreseeable growth patterns do not justify an expanded PM10

nonattainment area. The Farm Bureau disagreed with EPA’s analysis that future 

employment and population growth in Pinal County justifies including the southern 

portion of Pinal County, and they asserted that a severe economic downturn occurred after 

the growth projections were developed. A citizen characterized the growth projections for 

the southern portion of the county as grossly inadequate, due to the recession, which she 

argued has hit Pinal County harder than the nation as a whole. The commenter believes 

that the population growth in the southern portion of the county will be significantly lower 

than that relied upon by EPA. 

ADEQ argued that population estimates from the ADOT anticipated explosive growth in 

Pinal County starting shortly after 2000 and continuing through 2030, while in fact actual 

population growth in Pinal County has slowed considerably during the current economic 

downturn.  ADEQ also stated that the CAAG Employment Center Adjustment Strategy 

(March 31, 2010) identifies Maricopa, Casa Grande, Coolidge, Florence, Queen Creek and 

Apache Junction, but not Eloy, as the principal employment centers in the County.  It 

concluded that the employment density projections ADEQ included in its “strawman” 

boundary recommendation represented an optimistic view of the future developed at the 

height of the housing bubble that are now in serious doubt. ADEQ cited the uncertainty of 

growth forecasts in the midst of an economic recession and recommended collaboration 

with stakeholders and EPA to address growth‐related emissions on an as‐needed basis, 

noting that the regulatory timeframe allows the State several opportunities to address any 

additional control measures that may be necessary to reach attainment. ADEQ urged EPA 

to reconsider the southern boundary of the proposed nonattainment area. It noted that the 

area south of Arizona’s recommended boundary is sparsely populated, generally unaffected 

by commuting between Pinal and Pima counties, and is not likely to become a major 

mployment center.  ADEQ concluded that the original southern boundary in Arizona’s 

ecommendatio

e

r
22

the nonattainment area (while expanding the area to the south and east of the Governor’s 

recommended boundary), it is not the sole, or even the most important reason for doing so.   

We included the southern portion of Pinal County in the proposed nonattainment area 

based on a determination that the areas in the southern portion on Pinal County contribute 

to the violations monitored farther north.  Our determination in this regard stemmed from 

our consideration of the nine pertinent factors, which are discussed in detail in the TSD and 

the proposed rule itself. In short, we determined that the southern portion contributed to 

nonattainment, especially considering source mix and meteorology.  

In our final action, in due consideration of the comments submitted on our proposal, we are 

reducing the nonattainment area (relative to what we proposed on October 1, 2010) and 

we are not including the southern‐most portion of Pinal County, the Table Top Wilderness 

area, and certain largely undisturbed desert areas that lie east of Township 8 East. The 

Pinal Air Park monitor therefore is not included in the final boundary.  We have 

determined, however to include the Eloy monitor, because we continue to believe that the 

sources in the Eloy area contribute to violations of the PM10 NAAQS farther north, although 

we recognize that sources in and around Eloy do not contribute to every violation. We are 

persuaded to shrink the boundary in part based on the building permit data provided by 

Pinal County that documents the extent to which the national recession has slowed growth 

generally in Pinal County, but in the I‐8 and I‐10 corridors in particular. We agree that the 

recession and overabundance in homes already in foreclosure will likely delay significant 

growth in the corridors beyond the five‐year horizon for reaching attainment of the 

standard. Also see our responses to Comment 6, 8, and 9, above.  

We were persuaded to revise our proposed boundary by our review of satellite imagery, 

maps of source locations, and ADEQ’s maps illustrating emissions estimates by township, 

which together illuminate land use and emissions. In certain areas (such as Florence, Eloy, 

Picacho Peak, and lands to the south of Interstate 8), the final boundary extends beyond the 

State’s recommended boundary. This was done to include areas that, based on the location 

of sources of PM10 emissions, meteorological data that indicate winds from the southeast 

ransport emissions to violating monitors, and topographic information showing a lack of 

eographic barri

t

g ers, are contributing to air quality at violating monitors. 

Comment (16): ADEQ disagreed with what it characterized as EPA’s contention that 

growth‐related activity in the I‐10 corridor could lead to violations at the Eloy monitor. It 

argued that emissions from construction generally decrease following the first phase of a 

project, and that the Pinal County Air Quality Control District enforces a suite of fugitive 

dust rules requiring control measures and technology at construction sites. It contended 

that these activities, while associated with increased growth, can and would be controlled 

by existing rules implemented in areas outside of Arizona’s recommended boundary.  

DEQ also asserted that general conformity in and around the nonattainment area will 

urther mitigate emissions from federally‐funded construction projects. 

A

f
23

Response (17): EPA agrees that monitored concentrations at Eloy are not in themselves a 

sufficient reason for including Eloy and locations to the southeast in the nonattainment 

area.  However, EPA included the southeast portion because of the contribution of 

southeast emissions to violations at the Casa Grande and Pinal County Housing monitors.  

EPA does not agree with the commenters' implicit assumption that the southeast portion 

Response (16):  EPA did not in its TSD, nor do we now contend that growth‐related 

activity in the I‐10 corridor may lead to violations at the Eloy monitor. Rather, we took into 

consideration projected growth in the I‐10 corridor as one factor weighing in support of 

inclusion of the I‐10 corridor as contributing to violations at those monitors farther north 

that currently experience violations, EPA believes that emissions from sources in the Eloy 

area are currently contributing to air quality at violating monitors. As a result, this area 

must be included in the nonattainment area.  

Pinal County AQCD has established rules to reduce dust emissions at construction sites. 

The more restrictive rules apply only within existing nonattainment areas and do not apply 

in or around Eloy. General conformity does not apply outside of nonattainment or 

aintenance areas and thus would not mitigate emissions from federally‐funded 

onstruction projects in the Eloy vicinity if it is not included within the nonattainment area. 

m

c

Meteorology and Transport

Comment (17):  Both ADEQ (p.4) and PCAQ (p.2) commented that Eloy should not be 

included in the nonattainment area, since it does not have monitored violations.  ADEQ 

criticized EPA's use of wind roses to establish a predominantly southeastern wind 

direction, and added that "If winds from the southeast were contributing to exceedances at 

the violating monitors, the Eloy monitor would be violating as well," since Eloy is between 

the violating monitors and the presumed contributing areas to the southeast.   

ADEQ concluded that EPA’s assertion that prevailing winds from the southeast and long‐

range transport are contributing to exceedances at the violating monitors is unfounded. 

ADEQ argued that the Eloy monitor is south, southeast of these violating monitors and does 

not show any expected exceedances based on the 2006‐2008, 2007‐2009, and 2010 

monitoring data. If winds from the southeast were contributing to exceedances at the 

violating monitors, ADEQ asserted that the Eloy monitor would be violating as well. 

The Farm Bureau expressed concern that EPA has chosen to include areas that may

contribute to PM10 emissions without scientific justification for its assumption. 

A citizen contended that EPA has assumed that the PM10 emissions from sources in 

southern Pinal County are transported by “predominantly southeasterly winds” to the 

violating monitors in the central portion of the county, and that EPA relied upon the county 

line as a “default” boundary. The commenter argued that EPA’s use of this “default” 

boundary line  is wrong, based on the fact that the Eloy and Pinal Air Park monitors have 

ever shown a violation in the area from which the emissions are supposedly being 

ransported. 

n

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24

rized by a combination of changes in wind direction and spikes in PM10 

                                                           

must be the sole or main cause of violations in order for it to be included in the 

nonattainment area.  Emissions from the southeast may not be sufficient to cause a 

violation at Eloy , yet could still contribute to violations farther northwest.  EPA believes 

there is such a southeast area contribution, and it contributes sufficiently to violations to 

rovide a basis for including  Eloy and a portion of the southeast  in the nonattainment 

rea. 

p

a

Comment (18):  PCAQ commented (p.3) that meteorological data is sparse in the 25‐mile 

orth‐south expanse of the portion of EPA's proposed nonattainment area, and is not 

ufficient to war

n

s rant including that portion.   

Response (18):  EPA agrees that additional meteorological data in the area is desirable.  

However, a decision on the nonattainment area boundary must be made with the data 

currently available.  As discussed in EPA's proposal and TSD, EPA believes that there is 

sufficient meteorological data from the AZMET (Arizona Meteorological Network) stations 

within and around the proposed area to show that flow from the southeast toward the 

violating monitors occurs often.  EPA believes that this applies even during the exceedance 

days discounted by ADEQ and PCAQ (see response to comment 19). The available 

meteorological data provide evidence that emissions sources in the southeast contribute to 

AAQS violations and therefore provide justification for including  the southeast  in the 

onattainment a

N

n rea. 

Comment (19):  Both ADEQ (pp.4‐6) and PCAQ (p.3 and attached memo) examined 

HYSPLIT back‐trajectories for several high‐wind exceedance days, along with hourly 

concentrations and wind data.  From the abrupt changes in wind direction and increases in 

wind speed that often coincided with large increases in PM10 concentrations, they 

concluded that the PM10 is due to near‐field impacts rather than to long‐range transport. 

ADEQ noted that the statistically dominant wind direction for high wind events is typically 

from the west and southwest, and conducted a review to determine the extent to which 

PM10 exceedances occurred when winds were from the southeast. The evaluation utilized  

PM10 monitoring data collected at the Pinal County Housing, Casa Grande Downtown and 

Stanfield monitors during 2007 through the 3rd quarter of 2010. The data set was first 

screened to identify exceedance days where winds and stagnation were noted as the 

preliminary contributor. The NOAA HYSPLIT23  model was run for each identified day and 

the result was reviewed to provide a general wind direction. This process identified 56 

wind exceedance days. In order to evaluate potential contribution areas from the SE or SSE, 

a second screen was applied to remove any day on which the wind was not from those 

directions. The result identified five wind event days: August 16, 2007, August 29, 2007, 

August 8, 2008, October 27, 2008, and September 3, 2009. The HYSPIT data were 

characte

23 HYSPLIT is the Hybrid Single Particle Lagrangian Integrated Trajectory Model, Air Resources 

Laboratory of the National Oceanic and Atmospheric Administration (NOAA), web site 

http://ready.arl.noaa.gov/HYSPLIT.php.  Using weather data, it can show the paths (trajectories) along which 

air parcels arrived at a given time and place. 
25

                                                           

concentrations. ADEQ contended that this demonstrates near‐field impacts, rather than 

long‐range transport, as the major contributor. They also concluded that the analysis 

showed that wind‐transport from the southeast is not a dominant contributing factor for 

PM10 exceedances at the monitors in other portions of the county and noted that each of 

the referenced days has been flagged as an exceptional event.  The same type of analysis 

was completed for stagnation days. During the period 2007 through the 3rd quarter of 

2010, 13 stagnation days were identified. When the data set was screened for those days 

when the wind direction was from the SE or SSE, only one date was identified, November 4, 

2009. ADEQ asserted that the comparison of the back trajectory and the hourly particulate 

evels indicates that the PM10 contribution to the ambient monitors was from the 

mmediate vicin

l

i ity and not from long‐range transport from the southeast. 

Response (19): EPA agrees that the analyses performed by ADEQ and PCAQ provide useful 

information for evaluating the PM10 exceedances.  However, as discussed above, in setting 

nonattainment area boundaries one has to distinguish between the sole or main cause of an 

exceedance, and a contribution to the exceedance.  Even if the commenters are correct that 

"wind‐transport from the southeast is not a dominant contributing factor" (ADEQ p.4) and 

that the data "suggest a typical monsoon storm where local weather contributed to local 

impacts" (PCAQ p.3), transported emissions from the southeast nonattainment area 

portion nevertheless contribute sufficiently to exceedances at violating monitors to provide 

a basis for including the southest portion in the nonattainment area. As discussed in the 

TSD for EPA's proposal, and also below, EPA believes that the meteorological data provides 

evidence for such a contribution. 

Both ADEQ and PCAQ examined exceedance days for which HYSPLIT back‐trajectories 

approached monitors from the southeast.  PCAQ mentioned that there are relatively few 

such days, only 5 (or 9%) out of 56 total high wind exceedance days in 2007‐2009: August 

16, 2007, August 29, 2007, August 7, 2008, October 27, 2008, and September 3, 2009 (p.3).  

ADEQ examined the same days, except August 8 was used instead of August 7, 2008.  Even 

if there are relatively few days with transport from the southeast, EPA must consider them 

in setting the nonattainment area boundary.  In any case, there may be additional days with 

southeast transport that are not found by the HYSPLIT screening procedure used by the 

commenters.  They looked for days with the trajectory's ending hour oriented from the 

southeast, but this does not consider other hours during the day that may have flow from 

the southeast.  In addition, while HYSPLIT trajectories are a very useful tool, it is not clear 

they have adequate spatial resolution to draw conclusions about source contributions or 

specific nonattainment area boundaries on the scale of 10‐20 miles, which is  

approximately  how far the EPA nonattainment area extends beyond the ADEQ 

recommendation.  Some of the trajectories are hundreds of miles long.  The underlying 

GDAS24 meteorological data used by ADEQ and PCAQ with HYSPLIT has a resolution of one 

degree of latitude or longitude, or roughly 60 miles.  Thus EPA does not believe that the 

24 GDAS is the Global Data Assimilation System, a weather model incorporating data from weather 

stations around the world. Web site http://ready.arl.noaa.gov/gdas1.php 
26

                                                           

commenters' analyses can be definitive about transport from the southeast portion of the 

proposed nonattainment area. 

Even for the days selected by the commenters, the meteorological data suggest a 

contribution from the southeast.  AZMET data show wind from the southeast for at least a 

quarter of the day (6 or more hours) on August 16, 2007, August 29, 2007, and August 7, 

2008.  This is true for the Queen Creek AZMET station, which is near the Combs School 

PM10 monitor; the Coolidge AZMET station, north of the Pinal County Housing monitor; and 

for the Marana AZMET station, southeast of the southeast corner of EPA's proposed 

nonattainment area.  While for some of the hours the southeasterly wind direction does not 

coincide with the PM10 concentration spike noted by PCAQ, still there are enough hours 

with southeast winds to suggest some contribution from the southeast to the 24‐hour PM10

concentrations.  For October 27, 2008, as was stated by PCAQ, there were sustained winds 

from the southeast during much of the day at the Queen Creek and Marana AZMET stations, 

consistent with transport from the southeast portion of the proposed nonattainment area.  

Winds at the Coolidge AZMET station were from the east‐northeast; this is consistent with 

transport from the eastern portion of the proposed nonattainment area (the inclusion of 

which has also been opposed by ADEQ).  Thus, for at least four of the five days examined by 

ADEQ and PCAQ, EPA believes that the southeastern and eastern portions of the proposed 

nonattainment area do contribute to NAAQS exceedances. These relationships are 

illustrated in the wind roses in Figure 4.25 These wind roses were created by EPA using 

wind data from the Cowtown and AZMET meteorological stations on days when nearest 

PM10 monitor has a NAAQS exceedance during 2006‐2008.  Although 2009 meteorological 

ata were not available at the time of this analysis, the wind roses generally show that on 

xceedance days, winds are frequently from the southeast. 

d

e

25 Wind roses show the percentage of the time that wind blows from the various compass directions in 

various wind speed ranges.
27

The commenters' analyses do provide some evidence that local sources are more 

important for monitored exceedances than long range ones.  The main contributors to PM10

exceedances may indeed be relatively near the monitors (though as already discussed,  

other contributions to NAAQS exceedances should be included in the nonattainment area).  

Figure 4.  Pinal County Wind Roses
28

oundaries

Comment (21): One commenter stated that jurisdictional boundaries alone should not 

decide whether an area is included within the boundary of a nonattainment area. The 

commenter believes that EPA assumed that the PM10 emissions from sources in southern 

Pinal County are transported by “predominantly southeasterly winds” to the violating 

monitors in the central portion of the county, and relied upon the county line as a “default” 

boundary. The commenter found EPA’s assumption and use of the “default” to be 

However, a fundamental problem with the analyses is that the terms "local" and "long 

range transport" are subjective unless specifically defined.  Such qualitative terms are 

useful for thinking about the PM10 exceedances, but they do not provide a nonattainment 

area boundary: any particular distance of the nonattainment area boundary from the 

monitor could be considered by someone to be too far away to be considered “local.” In any 

event, EPA does not believe that emissions traveling 10‐20 miles can be dismissed as “long 

range transport.”  The southeast corner of EPA’s final nonattainment area boundary is 

about 22 miles from the violating Pinal County Housing monitor.  Dust from locations in the 

southeast portion of the nonattainment area could be transported to that monitor by a 

single hour of 20 mph wind, or by multiple hours of lower wind speeds, such as were 

observed on the days described above.   

EPA believes that areas southeast of the violating monitors contribute to NAAQS violations 

and can be considered “nearby areas” and so should be included in the nonattainment area. 

However, as noted above, EPA has reduced the size of its proposed nonattainment area.  In 

this final action, EPA has established the nonattainment area boundary to include a 

contiguous area in the east and southeast from which the wind transports emissions from 

roads, construction, disturbed land, and agricultural activities toward monitors violating 

the PM10 NAAQS.  The degree of emission control needed for such sources would be 

etermined by a more detailed analysis of particular days and sources as part of the State's 

orthcoming atta

d

f inment demonstration.  

Comment (20):  PCAQ identified October 27, 2008 as a day with wind‐driven PM10

exceedances that had sustained wind from the southeast (p.3 and attached memo p.2), but 

commented that this single day of apparent transport from the southeast is not a robust 

basis for including this portion of the County in the nonattainment area.  The commenter 

oncluded that available data does not support characterizing southern Pinal County as a 

ource of PM10 tr

c

s ansport that consistently affects the violating monitors to the north. 

Response (20):  EPA does not agree that this is the only day for which there is significant 

wind from the southeast (see response 19 above).  As described in our TSD and above, 

there is meteorological evidence that emissions from the southeast are transported to the 

exceeding monitor.   For the reasons set forth in the TSD and elsewhere in these responses, 

PA believes that the southeast contributes to violations and so should be included in the 

onattainment area. 

E

n

Jurisdictional B
29

lations of the secondary PM10 NAAQS could be occurring.

Response (22):  In determining the final boundary for the West Pinal PM10 nonattainment 

area, EPA took into account the history of dust storms and resulting traffic accidents in the 

erroneous, based on the fact that the Eloy and Pinal Air Park monitors have never sho

violation in the area from which the emissions are supposedly being transported. 

The commenter acknowledged that EPA has indicated that it would be inequitable to 

include less than an entire city within a nonattainment area, but pointed to the relatively 

more extensive size of city limits in Arizona (compared to elsewhere in the country), and 

sserted that  city  jurisdictional boundaries alone should not be determinative of the 

oundary for the

wed a 

a

b  nonattainment area. 

Response (21): Based on the available data, EPA continues to believe there is

meteorological evidence that emissions from the southeast are transported to the violating 

monitors, and that areas to the southeast of the State’s recommended boundary contribute 

to violations and so should be included in the nonattainment area. See EPA’s responses to 

comments 18 – 20. However, as noted above, EPA has reduced the size of its proposed 

nonattainment area to exclude wilderness areas and national forest lands and certain less‐

developed areas with relatively low levels of emissions.  See Figure 3 of this RTC, which 

illustrates the final boundary along with the distribution of sources of emissions, and 

Appendix B of Arizona’s technical report, which includes several maps illustrating the 

distribution of PM10 sources in Pinal County. The final nonattainment area does not extend 

as far to the east and south as the proposed boundary, and no longer coincides with the 

southern county boundary.   

We were persuaded to revise our proposed boundary by our review of satellite imagery, 

maps of source locations, and ADEQ’s maps illustrating emissions estimates by township, 

which together illuminate land use and emissions. In certain areas (such as Florence, Eloy. 

Picacho Peak, and lands to the south of Interstate 8), the final boundary extends beyond the 

State’s recommended boundary. This was done to include areas that, based on the location 

of sources of PM10 emissions, meteorological data that indicate winds from the southeast 

transport emissions to violating monitors, and topographic information showing a lack of 

geographic barriers, are contributing to air quality at violating monitors. 

Jurisdiction is one of many factors EPA considers in its creation of a nonattainment area 

boundary.  The weight given to any particular factor depends on the circumstances that 

xist in the area under consideration.  In this particular case, no portion of the proposed 

oundary was drawn solely to ensure that an entire city would be included.  

e

b

Secondary Standard

Comment (22): The Sierra Club stated its position that a conservative approach to the 

nonattainment boundaries is warranted in light of the exceedances of the public health‐

based primary PM10 NAAQS, and also in light of anecdotal evidence and news reports 

oncerning instances of unsafe driving conditions along I‐10 caused by blowing dust, 

uring which vio

c

d
30

                                                           

P

p

icacho Peak area.26  We note that the secondary standard for PM10 is the same as the 

rimary standard. 

Economic Impact

Comment (23):  The Arizona Game and Fish Department, which described its primary 

interest as maintaining lawful, reasonable public access for the use of motor vehicles in 

Pinal County for outdoor‐related recreation, expressed concern over the inclusion of 

portions of four game management units within the nonattainment area.  The commenter 

anticipated that motor vehicle travel on those lands would be restricted in an effort to meet 

the NAAQS, which could result in a loss of hunting and fishing opportunities. Because 

funding to manage and restore wildlife habitat and populations comes from the sale of 

hunting licenses and big game tags, a subsequent loss of funding to the AGFD could occur.  

he commenter also noted that hunters and anglers contribute significantly to the local 

conomy. 

T

e

Response (23):  To respond to this comment, EPA reviewed the maps of game 

management units that are available from the Arizona Game and Fish Department’s 

website and identified seven game management units that overlap portions of EPA’s 

proposed nonattainment area: 24B, 25M, 37A, 37B, 39, 40A, and 47M. The final 

nonattainment area boundaries do not overlap with two of the seven game management 

units that had been included in part within the proposed nonattainment area boundaries: 

24B and 47M. For two other units (37B and 40A), the overlap of the final nonattainment 

area boundaries and the game management units has been reduced to a small fraction of 

the overall size of the management units. For unit 37A, the overlap has been reduced 

significantly and now hews more closely to the agricultural areas in and around Eloy. For 

unit 39, the final boundaries overlap with the unit boundaries to the extent the unit extends 

into Pinal County, but the vast majority of unit 39 lies within Maricopa County and would 

not be affected by the redesignation of a portion of Pinal County for the PM10 standard.  

The greatest overlap between the final nonattainment area boundaries and the boundaries 

of the various game management units would occur with unit 25M. However, much of this 

unit has been developed by residential, commercial or agricultural uses and hunting 

opportunities there are quite limited. As to unit 25M, Arizona Game and Fish Department 

states on its website: “For 25M only – the majority of the unit has either been converted to 

residential/agricultural uses or lies within the jurisdiction of the Gila River Indian 

Reservation. Discharge of firearms in the incorporated parts of the unit may be limited by 

local city ordinance. Hunters will need to take great care to make sure they are not in city 

imits and more then 1⁄4 mi from residences. Hunting on the Gila Rivers Indian Reservation, 

f allowed, is governed by the Tribe.” 

l

i

26See pages 12 and 13 of ADEQ’s February 9, 2012 presentation entitled, “Pinal County PM10 and PM2.5

Nonattainment Areas,” available at http://www.azdeq.gov/environ/air/plan/download/020912adeqpp.pdf. 
31

Thus, EPA acknowledges that the final boundaries would overlap portions of certain game 

management units but notes that the extent of overlap has been reduced significantly 

(relative to the nonattainment area boundaries, as proposed) and that the unit most 

affected is also the unit (25M) where hunting opportunities are the most limited for 

reasons other than those related to air quality. Moreover, inclusion of portions of game 

management units within the nonattainment area boundaries does not prejudge the need 

for controls or regulation of emissions generated by motor vehicle travel on those lands. As 

noted above, Arizona will be required to develop a plan that results in the attainment of the 

air quality standard for PM10, and the relative contribution of various sources and options 

for control will be considered in that process.  That plan will be subject to public review 

nd comment, both at the state level and again when EPA evaluates the sufficiency of the 

lan. 

a

p

Scientific Justification

Comment (24): The Arizona Cotton Growers Association asserted that, without scientific 

justification, EPA simply assumed that the PM10 sources (agricultural operations, feedlots, 

dairies, CAFO’s, and road emissions) in the eastern and southern areas of Pinal County are 

transported by predominantly southeasterly winds to the violating monitors in the central 

portion of the county.  The Farm Bureau expressed concern that EPA has chosen to include 

reas that may contribute to PM10 emissions with no scientific justification for its 

ssumption. 

a

a

Response (24): Based on the available data, EPA continues to believe there is 

meteorological evidence that emissions from the southeast are transported to the 

exceeding monitors and that areas to the southeast of the State’s recommended boundary 

contribute to violations. See EPA’s TSD and the responses to comments 17 – 20, above. 

However, as noted above, based on our review of comments, we have reduced the size of 

the proposed nonattainment area. See responses to comments 9, 11, 12, 14, 15 and 21. 

The final nonattainment area does not extend as far to the east and south as the proposed 

boundary.  

   
32

exceptional events flags. The existing Phoenix PM10 nona

Apache Junction portion of western Pinal County) is unaf

   

III.  FINAL ACTION

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 submitted recommendations, EPA is redesignating 

from “unclassifiable” to “nonattainment” an area generally covering the western half of 

Pinal County, Arizona, for the 1987 PM10 NAAQS and therefore revising the boundaries of 

the existing “rest of state” unclassifiable area. EPA’s decision 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 the proposal and in the TSD.  

EPA’s final nonattainment area encompasses the area recommended by the State of 

Arizona, but extends farther to the south, east, and west.  The eastern boundary now 

partially coincides with the State’s recommended boundary (the north‐south line defined 

by the boundary between townships 8E and 9E) but extends farther to the east to include 

the Florence area and several nearby townships and, in the southern part of the 

nonattainment area, to include the Picacho Peak area. Based on the comments received on 

the proposed rule, as well as further evaluation, EPA is modifying its proposed boundary to 

exclude a portion of the Sonoran Desert National Monument (including the Table Top 

Wilderness Area), the Tonto National Forest and Superstition Wilderness Area, the 

Ironwood Forest National Monument, and certain undeveloped lands. The revision to our 

proposed boundary is based on our review of satellite imagery, maps of source locations, 

and ADEQ’s maps illustrating emissions estimates by township, which together illuminate 

land use and emissions. In certain areas (such as Florence, Eloy, Picacho Peak, and lands to 

the south of Interstate 8), the final boundary extends beyond the State’s recommended 

boundary. This was done to include areas that, based on the location of sources of PM10

emissions, meteorological data that indicate winds from the southeast transport emissions 

to violating monitors, and topographic information showing a lack of geographic barriers, 

are contributing to air quality at violating monitors. The West Pinal PM10 nonattainment 

area will be classified as “moderate” by operation of law.  

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 finalizing our proposal 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, are 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 Farms, pending consideration of issues unique to tribal lands, completion of formal 

consultation with the tribal governments, and (in the case of GRIC) consideration of 

ttainment area (including the 

fected by this action.  
33

IV.  LIST OF COMMENT LETTERS RECEIVED

• Benjamin Grumbles, Director, Arizona Department of Environmental Quality 

•

(October 28, 2010). 

•

Jim Thompson, City Manager, City of Casa Grande (October 28, 2010). 

Tiffany Shedd, Esq. (October 28, 2010). 

• Ron McEachern, General Manager, Central Arizona Irrigation and Drainage District 

•

(October 29, 2010). 

Mike Norris, President, Pinal County Farm Bureau (November 1, 2010). 

• Scott Davis, Director, Environmental Policy and Programs, Arizona Public Service 

•

Company (November 1, 2010).

Donald P. Gabrielson, Director, Pinal County Air Quality (November 1, 2010). 

• Sandy Bahr, Chapter Director, Sierra Club – Grand Canyon Chapter (November 1, 

•

2010). 

Kevin Rogers, President, Arizona Farm Bureau Federation (November 1, 2010). 

• Rod Lucas, Regional Manager, Mesa, Arizona Game and Fish Department (November 

1, 2010 – transmitted to EPA via email on November 3, 2010). 

• C. Lewis, Executive Vice President, Arizona Cotton Growers Association (October 27, 

2010).