# Arizona Air Quality Designations Technical Support Document

Boundary Recommendation for the Pinal County

24-hour PM 10 

# Nonattainment Area

Air Quality Division

March 15, 2010

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### i TABLE OF CONTENTS Page

EXECUTIVE SUMMARY......................................................................................................... ES-1

1.0 BACKGROUND ....................................... ......................................................................... 1

2.0 AREA DESIGNATION CRITERIA............... ........................................................................... 2

3.0 AREA DESIGNATION CRITERIA ANALYSIS FOR THOSE AREAS..............................3

RECOMMENDED AS NONATTAINMENT

4.0 AREA DESIGNATION RECOMMENDATIONS ....................................................................... 34

LIST OF FIGURES Page

ES-1 Preliminary PM 10 

### Emissions Inventory for Pinal County – All Sources ................ . ES-4

3-1 Preliminary PM 10 

### Emissions Inventory for Pinal County – Major Features.................. 4

3-2 Preliminary PM 10 

### Monitors in Maricopa, Pinal, and Pima Counties................. ............ 6

3-3 Preliminary PM 10 

### Emissions Inventory for Pinal County – All Sources........................8

3-4 Preliminary PM 10 

### Emissions Inventory for Pinal County – Onroad Sources ..... ............. 11

3-5 Preliminary PM 10 

### Emissions Inventory for Pinal County – Onroad Sources – ... ............ 12

Paved Roads

3-6 Preliminary PM 10 

### Emissions Inventory for Pinal County – Onroad Sources – ............13 Unpaved Roads

3-7 Preliminary Emissions Inventory for Pina l County – Agricultural Tilling and..............14 Harvesting

3-8 Preliminary PM 10 

### Emissions Inventory for Pinal County – Portable Sources...............15

3-9 Preliminary PM 10 

### Emissions Inventory for Pinal County – Industrial Sources.................16

3-10 Preliminary PM 10 

### Emissions Inventory for Pinal County – Concentrated...................17 Animal Feeding Operations

3-11 Preliminary PM 10 

### Emissions Inventory for Pinal County – Construction Sources............18

3-12 Preliminary PM 10 

### Emissions Inventory for Pinal County – Off-highway Vehicles..........19

3-13 Pinal County Population Density 2005............................................................21

3-14 Pinal County Population Density 2030...........................................................21

### ii 3-15 Land Ownership in Pinal County..................................................................22

3-16 Pinal County Employment Density 2005........................................................24

3-17 Pinal County Employment Density 2030........................................................24

3-18 2006-2008 Pinal County PM 10 

### Exceedances....................................................27

3-19 2006-2008 Pinal County PM 10 

### Exceedances Days by Month.................................27

3-20 2006-2008 Pinal County PM 10 

### Annual Exceedance Days.....................................29

4-1 Recommended Pinal County PM 10 

### Nonattainment Area Boundaries...........................35

LIST OF TABLES Page

ES-1 Summary of Nine Criteria Analysis for the Proposed Pinal County PM 10 

### .................. ES-3

Nonattainment Area

1-1 History of EPA’s Particulate Matter National Ambient Air Quality Standards ................. 1

2-1 Criteria for Nonattainment Area Boundary Recommendations.......................................... 2

3-1 2006-2008 Maximum 24-Hour Average PM 10 

### Compliance............................................... 5

3-2 2007 Pinal County PM 10 

### Emissions Inventory .................... ........................................ 7

3-3 Pinal County-Supplied Road Inventory and ADT.................... .................................... 9

3-4 Vehicle Miles Traveled and Emissions for HPMS and Pinal County Roads...............10

3-5 Population Growth and Density within Pinal County..........................................20

3-6 Inter-County Employment Commute Statistics for Maricopa and Pinal ....................23

Counties

3-7 Population and Daily Vehicle Miles Traveled in Pinal County.................................. 25

3-8 Summary of Nine Criteria Analysis for the Proposed Pinal County PM 10 

### ...................33

Nonattainment Area

### 1 EXECUTIVE SUMMARY

In July 1987, the U.S. Environmental Protection Ag ency (EPA) revised the existing National Ambient Air Quality Standard (NAAQS) for particulate matter 10 microns or less (PM 10 

### ) setting a 24-hour average standard of 150μg/m 3 

### . Ambient monitoring data for PM 10 

### collected throughout Pinal County by the Pinal County Air Quality Control District (PCAQCD) documents numerous violations of the PM 10 

### NAAQS in the western portion of Pinal County. In a letter date d October 14, 2009, EPA notified the Governor that Pinal County was being redesignated for nonattainment of the 1987 24-hour PM 10 

### NAAQS and requested

the State to submit PM 10 

### nonattainment area boundary recommendati ons for Pinal County within 120 days. The portion of Pinal County recommended for nona ttainment consists of the western and central regions of the County where violations of the 24-hour PM 10 

### NAAQS have occurred and where emissions sources and activities contributing to those violations are located, as shown in Figure ES-1. The Arizona Department of Environmental Quality (ADEQ) reco mmends the remainder of the County outside of the existing Hayden PM 10 

### Nonattainment Area and the Apache Junction portion of the Phoenix Planning Area

PM 10 

### nonattainment area be designated as attainment/unclassifiable.

This recommendation is based on consideration of the PM 10 

### standard, requirements for designation of nonattainment areas, and options available for implem enting the standard. This document demonstrates the impracticability of and lack of environmenta l benefit from designating the nonattainment area boundary based on EPA’s default defi nition of all of Pinal County.

As a new 24-hour PM 10 

### nonattainment planning area, the State is recommending those portions of Pinal County shown in Figure ES-1 as the nonattainment planning area for the 24-hour PM 10 

### NAAQS. This area excludes Indian Country in the affected portion of Pinal County.

T1S, R8E T2S, R8E T3S, R7E T3S, R8E T4S, R3E-R4E (excluding all lands within the G ila River and Ak-Chin Indian Communities) T4S, R8E (excluding all lands within the Gila River Indian Community) T5S, R3E (excluding all lands within the Ak-Chin Indian Community) T5S, R4E – R8E (excluding all lands within th e Gila River and Ak-Chin Indian Communities) T6S, R3E – R8E T7S, R3E – R8E Sections 1-6

### 1 Table ES-1 Summary of Nine Criteria Analysis for the Proposed Pinal County PM 10 Nonattainment Area

Criteria Factors Supporting the Recommended Nonattainment Area Boundary Factors Supporting the Exclusion of Eastern Portions of Pinal County Air Quality

Data The proposed nonattainment area includes

the locations of the monitors that recorded concentrations exceeding the NAAQS. Ambient air quality monitors located in the eastern and southern region of the County are not violating

the PM 10 NAAQS.

Emissions

Data The preliminary emissions inventory prepared by ADEQ and PCAQD determined that the majority of PM 10 emissions originate in the western and central regions of the County. The preliminary emissions inventory determined that sources in the eastern and southern regions of the County do not significantly contribute to violations in other regions of the County.

Population Density and Degree of

Urbanization The urbanized areas in the western and central regions of the County are where 95 percent of the County’s population resides. The eastern and southern portions of the County are largely undeveloped and have very low population

densities.

Traffic and Commuting

Patterns The recommended nonattainment area includes the rapidly growing urbanized and developed areas, the high-traffic Interstate corridors, and areas with the highest employment densities. The number of employers in the eastern portion of the County is low and is not projected to substantially increase during the potential maintenance period (2011-2031).

Growth Rates

and Patterns Significant growth is projected for communities near I-10 and I-8 during the potential maintenance period (2011-2031). The eastern region of the county has experienced limited growth and is not projected significantly

increase.
Meteorology The recommended nonattainment area includes the agricultural basin region of the County where stagnation conditions are known to impact PM 10 concentrations. There are no known meteorology conditions specific to the eastern por tion of the County known

to affect PM 10 concentrations.

Geography/ Topography The recommended nonattainment area is predominately located in the basin region of the County characterized by open-ended valleys with few topographic barriers. The eastern portion of the County is characterized by rough terrain, steep mountain ranges reaching over 7,000 feet in elevation.

Jurisdictional

Boundaries ADEQ’s recommendation maintains jurisdictional cohesiveness and requires no new institutional arrangements for accomplishing required tasks. The eastern portions of Pinal County recommended as attainment/unclassifiable designation lack significant emission source s or are in the existing Hayden PM 10 nonattainment area. Inclusion of these areas would not help bring the western region of the county into attainment.

Level of

Control of

Emission

Sources The Apache Junction area of the County

included in the Phoenix PM 10 Nonattainment Area is subject to stringent

PM 10 control strategies included in the Maricopa Association of Governments Five

Percent Reduction Plan. The number of PM 10 generating sources in eastern Pinal County is minimal. The largest point source in the area, ASARCO’s Ray Mine, is included in the existing Hayden PM 10 Nonattainment Area. The operating permit issued by PCAQCD for the mine contains control measures sufficient for attaining

the PM 10 NAAQS. Emissions from the mine are highly localized and do not affect the recommended

nonattainment area.



### ES-31Figure ES-1ES-4

### 1 Arizona Air Quality Designations T echnical Support Document Boundary Recommendation for the Pinal County 24-hour PM 10 

### Nonattainment Area

1.0 BACKGROUND

The U.S. Environmental Protection Agency (EPA) is charged with developing air quality standards for the protection of human health and the environment. As required by the Clean Air Act (CAA), EPA sets primary and secondary National Ambient Air Quality Standards (NAAQS) for six common air pollutants,

one of which is PM 10 

### . Maximum pollution levels or limits that are based on human health are called primary standards. Limits intended to prevent e nvironmental and property da mage are called secondary standards. The CAA requires EPA to assess the latest scientific information and review the NAAQS every five years.

The original exceedance-based 24-hour PM 10 

### standard was adopted in 1987, along with an annual PM 10 

### standard that compared the PM 10 

### average over 3-calendar years against the numerical standard. The 1987

24-hour PM 10 

### NAAQS is an "exceedance based" standard, which looks to a 3-calendar-year monitoring history and assesses the number of historical exceed ances of the 150 microgram-per-cubic-meter (μg/m 3 

### )

PM 10 

### standard. A monitor that measured three or fe wer exceedances based on daily sampling and over a three-year period complies with the standard, while one that measures four or more exceedances in a 3- year period violates the standard. In 1997, the EPA left the annual PM 10 

### standard unchanged, but revised the approach to assessing compliance with the 24-hour PM 10 

### standard. The EPA adopted a deterministic approach, comparing a 3-year average of the 98th percentile highest 24-hour average from each year against the 150 μg/m 3 

### standard. Subsequent litigation, howev er, resulted in overturning the 1997 PM 10 

### revisions and EPA reverted to assessing complian ce based on the 1987 exceedance-based algorithm.

In September 2006, EPA reviewed the latest scientific information on the health effects of exposure to

PM 10 

### . During the 2006 review period, EPA received comme nts from external scientific advisors and the general public about the science and policy review reports. On September 27, 2006, EPA revised the 1987

PM 10 

### standards by retaining the existing 24-hour PM 10 

### standard and revoking the Annual PM 10 

### standard; accordingly, this nonattainment area bounda ry recommendation addresses EPA’s 24-hour PM 10 

### standard.

Table 1-1 History of EPA’s Particulate Matter NAAQS

Date EPA Action 1971 Established Total Suspended Partic les Standard (45 microns or less)

1987 Established 24-hour and Annual PM 10 

### Standards

1997 Established 24-hour and Annual PM 2.5 

### Standards

2006 Revoked the Annual PM 10 

### Standard, retained the 24-hour PM 10 

### Standard, and

lowered the 24-hour PM 2.5 

### Standard from 65 μg/m 3 

### to 35 μg/m 3



### .

### 2 2.0 AREA DESIGNATION CRITERIA

Section 107(d)(1)(A)(i) of the Clean Air Act (CAA) defines a nonattainment area as “ any area that does not meet (or that contributes to ambient air quality in a nearby area that does not meet) the national primary or secondary ambient air quality standard for the pollutant.”

In a letter dated October 14, 2009, EPA requested that the State of Arizona determine nonattainment area boundaries for a Pinal County PM 10 

### Nonattainment Area. ADEQ conducted a nine factor analysis based on the analytical approach established by EPA’s gui dance pertaining to the 1997 8-hour ozone NAAQS,

the 1997 PM 2.5 

### NAAQS, and the 2006 PM 2.5 

### NAAQS. 1 

### ADEQ assessed these nine factors with respect to Pinal County, the default under EPA guidance. ADEQ di d consider neighboring counties with respect to their potential contribution to nonattainment when evaluating the boundaries of the proposed nonattainment area; ADEQ’s analysis of those counties is discussed in Section 3.0.

To refine nonattainment boundaries to be either larger or smaller boundaries than EPA’s default, the State must perform an area-specific analysis that addr esses the nine criteria discussed in the EPA guidance

cited above and listed below in Table 2-1. In addition, the State should affirm that the nonattainment area analysis demonstrates that: 1) violations are not o ccurring in nearby portions that are excluded from the recommended area, and 2) the excluded nearby portions do not contain emission sources that contribute meaningfully to the observed violations. 2



### Table 2-1 Criteria for Nonattainment Boundary Recommendations 1. Emissions data (location of sources and contribution to PM 10 

### concentrations) 2. Air quality data 3. Population density and degree of urbani zation (including commercial development) 4. Traffic and commuting patterns 5. Growth rates and patterns 6. Meteorology (weather and air movement patterns) 7. Geography/topography (mountain ranges or other air basin boundaries) 8. Jurisdictional boundaries (e.g., counties, air districts, existing nonattainment areas, etc.)

9. Level of control of emission sources

1 Memorandum from Robert J. Meyers , Acting Assistant Administrator, ``Area Designations for the Revised 24Hour Fine Particle National Ambient Air Quality Standard,'' June 8, 2007.

### 3 3.0 ANALYSIS OF FACTORS FOR DETERMINING NONATTAINMENT AREA

BOUNDARIES

According to EPA's guidance, the default nonattain ment area boundary for areas violating the air quality standard or contributing to a violation in a nearby area is the county in which the violating monitor(s) is located or where the contributing sources are located . The central and western portions of Pinal County

recommended as nonattainment are where ambient air monitors have recorded PM 10 

### concentrations that

violate the 24-hour PM 10 

### NAAQS; and emissions sources that contribute to those violations or were contributing to violations in areas without mon itors. No sources within the recommended area were identified as contributing to an external violation, and no external sources were identified as contributing

to violations within the recommended area.

In northern Pinal County, the Apache Junction Township already falls within the Phoenix PM 10 

### planning area. Although ADEQ recommends that the surrounding por tion of Pinal County be newly designated as

nonattainment for PM 10 

### , ADEQ recommends that no change in the designation status for Apache Junction, which will remain regulated as part of the Phoenix urban area.

Eastern Pinal County, however, contains vast expa nses of undeveloped public la nds and isolated rural communities where violations of the NAAQS have not occurred. Those rugged and sparsely populated townships in eastern Pinal County form a buffer be tween the growing urban and exurban areas in the western and central portions of the County that are recommended for PM 10 

### nonattainment, and the existing Hayden PM 10 

### Nonattainment Area. ADEQ therefore recommends that those portions of eastern Pinal County that are not already designated nonattainme nt be designated as attain ment/unclassifiable.

What follows is an explanation of how each criteri on was addressed in Arizona’s recommendation. Figure 3-1 (see page 5) illustrates the major features cons idered when assessing the nine factors for Pinal County.

3.1 Air Quality Data

This factor considers the 24-hour PM 10 

### concentrations recorded by air quality monitors in Pinal County during 2006-2008. The PM 10 

### NAAQS is an exceedance-based standa rd which is attained when the expected number of days per calendar year with a PM 10 

### 24-hour average above 150 μg/m 3 

### is equal to or less than one. The number of expected exceedances at a site is determined by recording the number of exceedances in each calendar year an d then averaging them over the p ast three calendar years; if a monitoring site has 3.1 or more observed or estimated exceedances in a three-year period, the monitor is

in violation of the 24-hour PM 10 

### NAAQS. If PM 10 

### sampling is scheduled less than every day, EPA requires the adjustment of observed exceedances to account for those days when a sample was not collected; the procedure for this pro cess is described in 40 CFR Part 50, Appendix K, Section 3.1. If less than 75 percent valid data completeness occurs in one or more calendar quarters, the monitor can not be classified as violating the NAAQS. In the case where there are collocated monitors and the primary monitor has data completeness below 75 percent, da ta substitution from the secondary monitor can not be done and compliance with the NAAQS can not be determined.

Monitoring data for 2006-2008 show that six Pi nal County monitors were in violation of the PM 10 

### NAAQS, although outstanding requests for EPA concurre nce regarding exceptional events could reduce the number of violating monitors to five for the 2006-2008 reference period. These violating monitors are clustered in the agricultural basin, which includes the urban and exurban high- growth areas contiguous with the Phoenix metropolitan area and along Interstat es 8 and 10. Table 3-1 contains monitor data for 2006-2008; Appendix A contains site summary air quality data record for 2006-2008.4Figure 3-1

### 5 All of the violating monitors are within the portion of Pinal County that the State is recommending as the

nonattainment area for the 24-hour PM 10 

### NAAQS. Figure 3-2 (see page 7) depicts the locations of PM 10 

### monitors in Maricopa, Pinal, and Pima Counties.

Table 3-1

2006-2008 Maximum 24-Hour PM 10 Monitoring Data

Maximum 24-hour Averages in μg/m 3 Expected Number of Exceedances Site Name

2006 2007 2008 2006 2007 2008 3-year Average Apache Junction Fire Station 73 48 57 0 0 0 0

Casa Grande Downtown 81 112 74 0 0 0 0

Casa Grande Downtown b
(opened March 2007) N/A 983 a 203 N/A 7.0 3.0 N/A

Combs School (opened 3/20/2007) N/A 970 a 270 N/A 44.6 4.0 N/A

Coolidge Maintenance Yard 106 82 55 0 0 0 0

Cowtown (opened August 2005) 606 759 465 278.2 166.2 145.5 196.6

Cowtown b 1,079 1,014 609 238.9 190.4 175.3 202.9 Eloy - County Complex 99 136 109 0 0 0 0 Mammoth - County Complex 31 40 35 0 0 0 0 Maricopa - County Complex b 429 724 520 21.2 20.1 6. 1 15.1

Pinal Air Park 77 113 53 0 0 0 0 Pinal County Housing Complex 153 224 141 0 6.5 0 2.2

Pinal County Housing Complex b 913 2,253 285 33.6 19.5 10.3 20.3

Riverside Maintenance Yard 83 65 44 0 0 0 0 Stanfield - County Complex 182 374 201 13.1 39.6 11.8 21.5 Stanfield - County Complex b
(opened February 2006) 727 a 1,062 375 26.5 25.2 14.2 N/A

a indicates the data do not satisfy EPA’s summary criteria, usua lly meaning less than 75 percent valid data recovery available in one or more calendar quarters.

b Indicates every day/continuous monitoring.

N/A Indicates data are not available. Note: exceedances due to exceptional events that have been concurred on by the EPA are excluded from annual

statistics.6Figure 3-2

### 7 3.2 Emissions Data

For this factor, ADEQ developed a preliminary emissi ons inventory for all of Pinal County. Table 3-2, below, contains estimates for each category in tons pe r year. An analysis of the methodologies used to calculate emissions for each category follows in the orde r as they appear below. Figure 3-3 illustrates the distribution of emissions from all sources in Pinal County.

The preliminary annual emission inventory presented in this document was developed for the purpose of defining the boundaries for a proposed nonattainment area. The eventual development of a State Implementation Plan (SIP) will require additional, more detailed, inventory deve lopment, including shortterm inventory data reflecting the 24-hour span of the controlling PM 10 

### standard. ADEQ found making credible estimates for disturbed soils on undevelope d lands and windblown dust difficult to determine for the preliminary emissions inventory. The State will characterize and quantify estimates for this category when developing an emissions inventory for the PM 10 

### SIP.

Table 3-2 Pinal County Preliminary 2007 PM 10 

### Emissions Inventory

Emission Categories Tons

per
Year Addressed

in Section

Onroad 42,130 3.2.1 Tilling, Harvesting, and Agriculture 2,538 3.2.2 Stationary Industrial Sources 2,342 3.2.3 Concentrated Animal Feeding Operations 2,045 3.2.4 Construction Emissions 1,757 3.2.5

Portable Industrial Sources 38 3.2.3 Off-highway Vehicles 23 3.2.6
Total 50,873

Decisions on nonattainment boundaries can not be ma de solely on area wide emissions inventories

because of the influence that localized sources can have on PM 10 

### concentrations. It is possible for source categories that represent a small portion of the area-wide inventory to have a si gnificant impact on either a violating monitor or the ambient air in areas where there are no monitors.8Figure 3-3

### 9 3.2.1 Onroad Emissions

Emissions from onroad sources include three categories 1) emissions from exhaust, tire and brake wear on paved and unpaved roads; 2) fugitive emissions on paved and unpaved roads; and 3) emissions from unpaved shoulders on paved roads. Emission factors for each category and the number of vehicle miles traveled (VMT) for all the roads in Pinal County are required in order to estimate emissions.

The inventory of all the roads in Pinal County come from two sources, Arizona Department of Transportation's (ADOT) Highway Performance Mon itoring System (HPMS) and a road inventory supplied by PCAQCD. The HPMS database provides the annual average daily traffic (AADT) for each road segment, which can be used to calculate VM T. The road inventory compiled by PCAQCD was developed from the County’s internal records, availa ble municipal records, and from inspection of aerial photographs. The unpaved roads covered by that inventor y included private roads, agricultural roads, and

trails.

For County-supplied roads, ADT volumes were assu med as shown in Table 3-3. For example, for County-maintained unpaved roads an average daily vol ume of 100 trips was used to develop estimates. This figure was selected based on traffic counts conducted by PCAQCD on highly-traveled unpaved roads and a study conducted near the violating Pinal County Housing (PCH) monitor in 2009.

For private unpaved roads, an ADT volume of 50 was selected using an estimate of five residential dwellings per private unpaved road; the number of tr ips per dwelling was derived from a study conducted by the Texas Traffic Institute which determined that one residence equals an average of 10 trips per day. The emissions for each category will be described next.

Table 3-3 Pinal County-Supplied Road Inventory and Average Daily Traffic

Surface Type ADT

Paved 100
County-maintained Unpaved 100 Asphalt Rock Dust Palliative 100

Trail 10 Private Unpaved 50
Agricultural 4

1. Emissions from exhaust, tire and brake wear:

EPA's MOBILE6 was used to determin e the appropriate emission factors for this category. The emission factor was calculated for each road segment in th e HPMS database based on the road classification and the vehicle mix. For County-supplied roads, the av erage emission factor of HPMS road segments was

assumed.

The emission factor for each road segment was then multiplied by its VMT to derive exhaust, tire and

brake wear emissions.

2. Fugitive emissions on paved and unpaved roads:

To estimate fugitive PM 10 

### emissions for paved and unpaved road s in the HPMS database, the State utilized the methods described in EPA's AP-42 guid ance to determine the emission factors for this

### 10 category. The emission factor for each paved road se gment in the HPMS database was determined based on silt loading and vehicle weight derived from the vehicle mix. The emission factor for each unpaved road segment in the HPMS database was calcula ted based on silt content and average speed.

The fugitive emission factor for each road segment w as then multiplied by its VMT to derive the fugitive emissions. The silt loading value for paved roads was extracted from the Maricopa Association of Governments' (MAG) 2007 Five Percent Plan for PM 10 

### for the Maricopa County PM 10 

### Nonattainment

Area. The silt content value for unpaved roads was extracted from ADOT's 2006 Final Report: Identification of Emissions Sources for Pinal County

.

For the paved roads data supplied by PCAQCD, the average emission factor of paved HPMS segments was assumed, while the average emission factor of unpaved HPMS segments was assumed for the unpaved roads supplied by PCAQCD.

The emission factor for each road segment was th en multiplied by the VMT to derive the fugitive

emissions.

3. Emissions from unpaved shoulders on paved roads

Fugitive emission estimates for unpaved shoulders on paved roads were calculated based on the percentage of heavy-duty vehicles traveli ng on the road segments and the VMT.

Conclusion

The State's analysis determined that onroad emissions are the largest emission category in Pinal County. Most of the emissions from paved and unpaved roads occur in the western and central regions of the County, as shown in Figures 3-4, 3-5, and 3-6. Emissions for this category in 2007 are estimated to be 41,615 tons per year. Table 3-4 provides a complete summary of emissions estimates for Pinal County.

Table 3-4 Vehicle Miles Traveled and Emissions for HPMS and Pinal County Roads

HPMS Roads Pinal Roads Total No. of Segments 980 30,647 31,627 Total Daily VMT 6,612,409 270,439 6,882,848 Daily Paved VMT 6,591,011 32,359 6,623,370 Daily Unpaved VMT 21,398 238,080 259,478 Exhaust, Tire and Brake Wear (tpy) 158 5 163 Fugitive Emissions - Paved Roads (tpy) 4,600 27 4,627 Fugitive Emissions - Unpaved Roads (tpy) 3,140 33,589 36,729 Fugitive Emissions - Unpaved Shoulders (tpy) 97 97 Total Emissions (tpy) 7,994 33,621 41,61511Figure 3-412Figure 3-513Figure 3-6

### 14 3.2.2 Cultivated Agriculture Emissions

In order to estimate emissions for this category, ADEQ analyzed land use th roughout the County by conducting field surveys and reviewing the most recent ly available satellite images. GIS was employed to calculate the area of agricultural fields. ADEQ used emissions factors developed by the United States Department of Agriculture (USDA); PM 10 

### emissions for tilling and harvesting were based on the data from the USDA National Agriculture Statistics Service. To tal emissions were spatially apportioned to each agricultural field based on area size. As shown below in Figure 3-7, most agricultural emissions are located in the western and central regions of the County. Agri cultural emissions in other regions of the County were less than 20 tons per grid cell. Emissions for this cate gory in 2007 are estimated to total 2,538 tons per year.

Figure 3-7

### 15 3.2.3 Portable and Stationary Industrial Source Emissions

To determine emissions for portable and stationary industrial sources, ADEQ reviewed the Arizona Emissions Inventory System (AEIS) for operating pe rmits issued by ADEQ and PCAQCD. The emissions limits established in the operating permits helped AD EQ determine annual emissions for these categories in 2007. ADEQ was unable to calculate credible process em issions for portable sources. Due to the relatively small quantity of emissions estimated for portable sources, when spatially allocated do not meet the threshold for depiction in Figure 3-8; for that reason the locations of the sources are depicted on the map. Emissions for this category are estimated to total 38 tons per year . The industrial source emitting the greatest volume of PM 10 

### emissions in Pinal County is ASARCO’s Ray Mine located near the County’s eastern border, as shown in Figure 3-9. This source is permitted by PCAQCD and is located within the existing Hayden PM 10 

### Nonattainment Area. Emissions for th is category are estimated to total 2,342 tons

per year , the majority of which are assigned to the ASARCO Ray Mine in eastern Pinal County.

Figure 3-8

### 16 Figure 3-9

### 17 3.2.4 Concentrated Animal Feeding Operations (CAFOs) Emissions

To estimate emissions for this category, ADEQ obtained emission factors from the Western Regional Air Partnership’s Fugitive Dust Handbook. Activity le vels were obtained from ADEQ’s Water Quality Division. An emissions factor of 10.59 pounds per-h ead per-year (lb/head-yr) was used for beef or calf operations; 4.182 lb/head-yr was the emission factor used for dairy, egg layer, and ostrich farm operations. After consultation with PCAQCD staff, the ac tivity levels for some feed lots were adjusted for realistic emissions levels. ADEQ based these adjust ments on field observations and inspections by PCAQCD staff. The CAFOs that emit the greatest quan tity of emissions are located in the western and central regions of the County, as shown in Figure 3-10 . Emissions for this category in 2007 are estimated

to be 2,045 tons per year.

Figure 3-10

### 18 3.2.5 Construction Emissions

Pinal County’s air quality permits database was used to identify 1,148 dust control permits issued during 2007. The size and scope of earthmoving activities were also obtained by reviewing the permits database. ADEQ used aerial photography to verify earthmoving activities. Construction sites were then coded in ADEQ’s GIS database and each site was calculated in total acres. The emissions factors used by ADEQ for this category were derived from a 2005 PM 10 

### emissions inventory completed by the Maricopa County Air Quality Department. 2 

### As shown in Figure 3-11, the majority of construction emissions were located in high growth areas of the County. Emissions for this category in 2007 are estimated to be 1,757 tons per

year

.

Figure 3-11

2 http://www.maricopa.gov/aq/divisions/plannin g_analysis/docs/2005_PM 10/05_PM_CH_3_Area.pdf

### 19 3.2.6 Off-highway Vehicle Emissions

To estimate emissions for this category, ADEQ obt ained the number of titled off-highway vehicles (OHVs) in Pinal County from the Arizona Departme nt of Transportation’s Motor Vehicles Division.

Emission factors were obtained from EPA’s NONROAD model for 2007. Due to the relatively low volume of emissions for this category, when spatially allocated there were no grid cells over the 20 tons per year threshold; accordingly, ADEQ chose to depi ct the locations of designated OHV recreation areas, as shown below in Figure 3-12. Emissions for this category in 2007 are estimated to be 23 tons per year

.

Figure 3-12

3.2.7 Conclusion

After completing the preliminary emissions inve ntory, ADEQ determined that most ambient PM 10 

### emissions are concentrated in the more developed ar eas of western Pinal County - with the exception of the Ray Mine, which is already included in the Hayden PM 10 

### Nonattainment Area. ADEQ’s determination is supported by ambi ent monitoring data collected by air quality monitors violating the NAAQS in the western region of the county.

### 20 3.3 Population Density and Degree of Urbanization

Table 3-5 features population estimates for munici palities within Pinal County for 2000 and 2008. 3 

### The population of the County has grown dramatically – 95.1 percent – in the intervening years. Development in Pinal County is limited to privately owned areas; most of the land available for development is located along the I-8 and I-10 corridors, as shown in Figure 3-15. Approximately 95 percent of the Pinal County population lives within this region. Figure 3-13 depi cts the population density of Pinal County in 2005; Figure 3-14 depicts the County’s projected population de nsity in 2030. It must be noted that the residential housing market in Pinal County has been particularly affected by the national economic recession, with 1 in 35 homes in foreclosure in 2009. 4 

### Construction of new homes and commercial buildings has slowed considerably.

Sources: Arizona Department of Economic Se curity – Population Statistics Unit.

3 Population estimates were obtained from the Arizona Department of Commerce, Arizona Populat ion Estimates 1980 thru 2009, because all State agencies are required to use them pursuant to the Governor’s Executive Order 2009-01, superseding Executive

Order 95-2.

4 Josh Brodesky. “Foreclosure Filings Show No Letup.” Arizona Daily Star 16 October 2009, morning ed.: A17.

5 Square mileages for 2009/2010 were obt ained from municipality websites.

6 Queen Creek straddles the Maricopa/Pinal County border; approximately 23.4 percent of the city’s square miles are within Pinal County. To estimate a population for the Pinal County porti on of Queen Creek, ADEQ divided the 2000 and 2008 population estimates by 23.4 percent. 

### Table 3-5 Population Growth and Density within Pinal County
Entity Area in Square

Miles

2000 Area in Square

Miles

2009/2010 5 2000 Population

Density 2008 Population

Density 2000 Population 2008 Population



### Pinal County Total 5,369.6 5,369.6 33.5 65.3 179,727 350,558 Apache Junction 34.2 34.2 930.2 1,08.7 31,814 37,917 Casa Grande 53.1 109 475.0 433 25,224 45,116 Coolidge 5.03 65 1,548.5 189.4 7,789 12,311 Eloy 71.7 110 144.7 146.9 10,375 16,163 Florence 8.3 50 1,742.9 481.9 14,466 24,096 City of Maricopa 31.9 43 46.5 831.9 1,482 35,770 Queen Creek 6 

### n/a 26 n/a 214.5 1,010 5,576

### 21 Figure 3-13 Pinal County Population Density 2005

Source: Arizona Departme nt of Transportation



### .

Figure 3-14 Pinal County Population Density 2030

Ibid.22Figure 3-15Source: PCAQCD.

### 23 3.4 Traffic and Commuting Patterns

This factor considers commuting patterns of residents and commuters to Pinal County. Nearly 80 percent of those commuting to work in Pinal County are residents. For the 2006-2008 period, the U.S. Census Bureau estimated that Pinal County had a work force population of 101,887. As of July 2008, 226,208 vehicles were registered in Pinal County; this figure represents an increase of 7 percent from 2007. Table

3-6 contains data on the number a nd percentage of those commuting to and within Pinal, Pima, and Maricopa Counties; these statistics may be dramatica lly higher in the 2010 decennial census. Figure 3-16 depicts Pinal County employment density in 2005; Fi gure 3-17 depicts projected employment density for Pinal County in 2030. The highest employment densiti es are located in the western region of the county.

Table 3-6 Inter-County Employment Commute Statis tics for Maricopa and Pinal Counties from U.S. Census Bureau, April, 2000 Census
Employment County Residence County Number of Commuters Maricopa Pinal 19,918 Apache 7

Cochise 43

Coconino 0

Gila 333

Graham 3

Greenlee 6

La Paz 0 Maricopa 7,751

Mohave 7 Navajo 7

Pima 1,974

Pinal 35,961

Santa Cruz 11

Yavapai 25

Yuma 13 Pinal

Total 46,141

Pima Pinal 2,601

### 24 Source: ADOT.



### Figure 3-17 Pinal County Employment Density 2030

Ibid. 

### Figure 3-16 Pinal County Employment Density 2005

### 25 3.5 Growth Rates and Patterns

Most of the population growth in Pinal County since the year 2000 occurred in the central and western region of the County. The catalyst for the explosive gr owth can be attributed to reasonably priced housing

near the I-10 corridor between the Phoenix and Tucson MSAs. With explosive growth came an increase in the number of vehicles and vehicle miles traveled (VMT) in Pinal County. Figure 3-2 (page 7) depicts onroad emissions throughout the County; the map demons trates that the highest concentrations of onroad emissions occur in the proposed nonattainment area. Th e majority of the increase in VMT has occurred in the western half of the County where an estimated 95 percent of the County’s population lives. Table 3-7 below contains population and VMT growth for Pinal County.

Sources: Census Bureau and ADOT. Table 3-7 Population Growth and Daily Vehicl e Miles Traveled in Pinal County

2000 Population 2007 Population

Estimate Population

% chan g e (2000 - 2007) 2000

VMT (1000s mi) 2007

VMT (1000s mi) % Change

Pinal County 179,727 350,558 95.1% 6,917 10,259 48%

### 26 3.6 Meteorology

Central Arizona experiences periods of significant wi nds associated with frontal passages, troughs of low pressure, summer monsoon storms, and occasional strong pressure gradients. The meteorology associated with winds in Pinal County ranges from synoptic scal e systems such as frontal passages, strong pressure gradients, Mesoscale Convective System (MCS) 7 

### and regional monsoon storms to micro scale storm cells that form locally.

The frontal passages are typically associated with strong Pacific Northwest low pressure systems that develop over the northern Pacific Ocean and move sout heast into the western United States. Strong winds in advance of cold fronts can reach speeds over 30 mi les per hour (mph) which cause significant areas of blowing dust in central Arizona. The duration of the strong, gusty winds can last up to eight hours and result in elevated hourly PM 10 

### concentrations. The hourly PM 10 

### concentrations associated with frontal passages may not reach those precipitated by mons oonal thunderstorms – however – their temporal

duration can create 24-hr PM 10 

### concentrations which reach the 99 th 

### percentile of historical PM 10 

### 24-hr average data.

Pressure gradient exceptional/natural events result from strong high pressure building over the western United States and low pressure to the east. As the hi gh pressure builds, a pressure differential is created that causes strong winds over Arizona. The result is locally-developed blowing dust and dust transported from areas surrounding Pinal County. As with frontal passages, duration of strong, gusty winds can last several hours. The combination of the long durati on of transported dust and locally derived dust

overwhelm the PM 10 

### monitors.

The monsoon is a seasonal wind that takes place in the southwestern United States and Northern Mexico during the summer months. The typical diurnal winds in central Arizona are ‘drain age’ in nature; in the morning, easterly winds that originate in the mountains switch direction to westerly winds in the afternoon due to the heating of the desert floor. Du ring a monsoon, however, winds will shift to an easterly to southeasterly direction. This is due to a ridge of high pressure that sets up over the Four Corners region in northeastern Arizona. The result is an influx of atmospheric moisture from the south and east, and storm development, which can be synoptic in nature as large lines of storms form either over

the northern Arizona or northern Mexico/southern Arizona and move into the central area of Pinal County.

Monsoon thunderstorms can also be local in nature , with the formation of localized monsoon supported storm cells. Both monsoon setups can pack significant winds (reaching gusts over 60 mph) that cause dust storms to develop, transporting a wall of dust (Haboob) up to hundreds of miles. These storms have dustcausing effects similar to frontal passages and st rong pressure gradients. The monsoon “season”, as defined by the National Weather Service, starts on June 15 th 

### and lasts through September 30 th 

### . Haboobs are frequent at the beginning of the monsoon and subside as the storm progresses, when measurable rainfall normally occurs. Monsoon storm cell(s), howev er, can create strong enough wind gusts to cause blowing dust even after recent precipitation.

Not all exceedances in Pinal County are wind related: stagnation conditions in the fall and winter occur when cold air and the absence of winds trap ambient PM 10 

### in the lower atmosphere. The region of the county most impacted by stagnation conditions is th e western agricultural basin area of the county. Stagnation exceedances tend to have lower PM 10 

### concentrations than exceedances caused by wind events, as shown in Figure 3-18. Figure 3-19 illustrates the number of exceedances by month in Pinal County during 2006-2008. A complete history of exceedances during 2006-2008 is included in Appendix B.

7 http://www.weather.gov/glossary/index.php?letter=m

### 27 2006-2008 Pinal County PM10 Exceedances Average Concentration by Meteorology Type

(Excluding Cowtown)

296

173

0 50 100 150 200 250 300 350

Avg Wind Avg Stagnation

Meteorology TypePM10 Concentration (ug/m3)

NAAQS 

### Figure 3-18

Figure 3-19

2006 through 2008 Pinal County PM10 Exceedance Days by Month
Excluding the Cowtown Monitor

0 1 2 3 4 5 6 7 8

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

2006 2007 2008Exceedance Days

### 28 Handling of Exceptional Meteorological Events

EPA’s 2007 Final Rule, Treatment of Data Influenced by Exceptional Events established guidelines for the review and handling of air quality monitoring data influenced by exceptional ev ents. In this rule, the

demonstration to exclude data includes a clear causal relationship between the measurement under

consideration and the event that is claimed to have affected air quality in the area and the exceedance

would not have occurred “but for” the event.

EPA notes in the Final Rule that natural events (one form of exceptional events according to the definition) may recur, sometimes frequently (e.g. w estern wildfires). For the purpose of this rule, EPA

defines “natural event” as an even t in which human activity plays little or no direct causal role to the event in question. The EPA recognizes that over time, certain human activities may have had some impact on the conditions which later give rise to a "natural '' air pollution event. However, EPA does not believe that small historical human contributions should pr eclude an event from being deemed "natural.''. The March 22, 2007, EPA-adopted rule supersedes all previous documentation regarding flagging and excluding data.

According to the final rule, excepti onal events are events for which the normal planning and regulatory process established by the CAA is not appropriate. The rule gives authority to exclude air quality monitoring data from regulatory determinations rela ted to exceedances or violations of the NAAQS and avoid designating an area as nonattainment, redesign ating an area as nonattainment, or reclassifying an existing nonattainment area to a higher classification if a State adequately demonstrates than an exceptional event has caused an ex ceedance or violation of a NAAQS.

The EPA requires States to take reasonable measures to mitigate the impacts of an exceptional event. In accordance with the language in the ru le, EPA defines the term "exceptiona l event'' to mean an event that:

(i) Affects air quality; (ii) Is not reasonably controllable or preventable; (iii) Is an event caused by human activity that is unlikely to recur at a particular location or a natural event; and (iv) Is determined by EPA through the process established in the regulations to be an exceptional event.

The PCAQCD reviews of PM 10 

### data, meteorology records, the implem entation of local fugitive dust rules, and the impact of potential local and regional sources when determining whether a PM 10 

### exceedance(s) is covered under exceptional/natural event classification.

In June 2008, PCAQCD s ubmitted documentation for PM 10 

### exceedances that occurred in 2007 that the County considered exceptional events. EPA subse quently informed PCAQCD that the submitted

documentation needed additional information in accord ance with the existing rule. In response, PCAQCD is currently coordinating with EPA to develop more robust exceptional event demonstrations for events that occurred in Pinal County during 2007 and 2008. If EPA concurs with the revised demonstrations, the monitoring data flagged in AQS will be excluded fro m regulatory determinations related to exceedances

or violations of the 24-hour PM 10 

### NAAQS. PCAQCD is currently reviewing the PM 10 

### exceedances flagged in AQS to determine if the events from 2007 and 2008 meet EPA’s criteria for exclusion under

the 2007 Final Rule.

The number of exceedance days in Pinal County attributed to high winds in 2007 was 35; the total for 2008 was 17. Of those wind events, PCAQCD has or will be submitting technical demonstrations for 30 exceedance dates in 2007 and 15 in 2008. It is important to note that even if EPA were to concur with

### 29 every exceptional event demonstration submitted by PCAQCD, Pinal County would still qualify as nonattainment for violating the 1987 PM 10 

### NAAQS. Exceedances of the NAAQS attributed to stagnation conditions do not qualify for exclusion under the ex ceptional events final rule. Figure 3-20 shows the number of exceedance days in Pinal County during 2 006-2008; Figure 3-20 also exhibits the number of exceedance days that PCAQCD flagged for exclusio n in AQS and the number of stagnation exceedances for each year.

Figure 3-20

2006 through 2008 Pinal County PM10 Annual Exceedance Days
Classified by Meteorology, Excluding the Cowtown Monitor

0 5 10 15 20 25 30 35 40 45 50 55

2006 2007 2008

Flagged Wind Event Unflagged Wind Event StagnationExceedance Day



### 3.7 Geography/Topography (Mountain Ranges or other Air Basin Boundaries)

The topography of Pinal County can best be described as a broad basin, low in elevation, surrounded in each direction by mountain ranges. Open-ended valle ys characterize the topography of western Pinal County. The area does not have geographical or t opographical barriers limiting air-pollution transport

within its airshed. Because PM 10 

### is primarily crustal, transport from outside the valleys is unlikely, excluding occasional exceptional events. The elevation of the basin area of Pinal County is approximately 1,200 feet above sea level.

The mountain ranges that surround the basin area create complex mountain-valley wind patterns. The Estrella Mountains in the northwest portion of the County reach 4,125 feet in elevation and provide a buffer between Pinal and Maricopa Counties. In th e northern portion of Pinal County, the Superstition and San Tan Mountains rise to a height of 5,036 and 3,054 feet, respectively. Near the western border of the County, the Table Top Mountains reach 3,392 feet in elevation. To the south, the Black Mountains reach 5,577 feet. The Pinal Mountains in western Gila County, near Pinal County’s eastern border, reach 7,848 feet in elevation.

### 30 3.8 Jurisdictional Boundaries (e.g., existing PM 10 

### non-attainment areas)

When recommending PM 10 

### nonattainment area boundaries, EPA re commends that the State consider sources contributing emissions from a broad geographic ar ea. Accordingly, the State chose all of Pinal County as a starting point for evaluating boundaries of the proposed nonattainment area. In evaluating the jurisdictional boundary factor, the State gave special consideration to nearby areas that are already designated as nonattainment for violating the 1987 PM 10 

### NAAQS: the Hayden Moderate PM 10 

### Nonattainment Area and the metropolitan Phoenix Serious PM 10 

### Nonattainment Area. The State also considered the authorities of PCAQCD and its re sponsibilities to facilitate air quality planning and implement control measures to attain the standard. It is also important to note that neither the Pima Association of Governments (PAG) nor MAG has jurisdiction in Pinal County. Those metropolitan planning organizations (MPOs) have been certified to develop air quality plans within those counties only.

Five cities and towns are located in central and w estern Pinal County: Casa Grande, Coolidge, Eloy, Florence and Maricopa. In addition, the Town of Queen Creek straddles Maricopa and Pinal Counties. Since all the violating monitors are located in or n ear all of these towns, the incorporated boundaries of these municipalities were taken into account.

Three Indian Reservations occupy portions of Pina l County: Gila River Indian Community, covering 372,000 acres, 280,000 acres of which are located in the northwestern part of the County; the nearly 22,000 acre Ak Chin Indian Community, all of which is located near the Town of Maricopa in western Pinal County; and the 2.7 million acre Tohono O’odham I ndian Nation, most of which is in Pima County, with approximately 275,000 acres in southwestern Pi nal County. The State has no jurisdiction over Indian Country, and, as such, no recommendation is be ing made for designations relating to these three

Indian Reservations.

3.9 Level of Control of Emission Sources

Pinal County

The expansion of “Area A” in 1999 and subsequent legislation adopted by the Arizona Legislature required State, County, and regional air quality planni ng agencies to implement measures for dealing with particulate pollution.

Pinal County is authorized under the Clean Air Act an d Arizona Revised Statutes as one of three Arizona counties with designated authority for air qualit y monitoring and permitting. The County manages a permitting program that requires stringent control me asures. Prior to issuing a permit, PCAQCD uses computer modeling to assess the impact of emissions on local ambient air quality. PCAQCD issues permits for industrial sources, open burning, dust producing activities, and has an approved Title V permitting program. The County also has an approved program in place for the prevention of significant deterioration (PSD). The County conducts routine fiel d inspections to verify compliance with permit conditions and operates a Countywide monitoring network to determine if the ambient air is meeting the

24-hour PM 10 

### NAAQS.

Those areas of Pinal County recommended by the St ate for designation as attainment/unclassifiable include the portions of the County where attainment of NAAQS has been demonstrated. For its analysis, ADEQ reviewed available ambient monitoring data and statistics for population density, degree of urbanization, traffic volume, commuting patterns, and jurisdictional boundaries. After analyzing these criteria, ADEQ concluded these areas of the County ar e not experiencing or likely causing or contributing

### 31 to an exceedance of the PM 10 

### NAAQS. Including these portions of the County in the nonattainment area would not help the area reach attainment of th e NAAQS. This recommendation for eastern Pinal County does not affect the status of the existing Hayden PM 10 

### nonattainment area in that portion of the County; 8


### nor does the recommendation for northern Pinal County aff ect the status of the portion of the County that is included in the existing Phoenix Planning Area for PM 10, 

### which includes only the 36 square mile Apache Junction Township commonly identifie d as Township 1 North, Range 8 East.

Pima County

Although Pima County has a larger population a nd higher population density, significantly more commuters and a greater number vehicle miles travel ed than Pinal County, no monitors in the County

violate the 1987 24-hour PM 10 

### NAAQS. 9



### If PM 10 

### emissions originating in Pima County were cont ributing to violations in Pinal County, the monitors closest to the County border would be the most likely to be affected; however, the Pinal monitors closest to Pima County are not violating the 24-hour PM 10 

### NAAQS. The Pinal Air Park monitor is located directly on the border with Pima County and is not violating; the Mammoth monitor 20 miles north of the County border is not violating; and the Eloy monitor, 20 miles north of the County border is not violating; however, the Eloy monitor is located in a well developed area and does not appear to be affected by sources such as cultivated agri culture and unpaved roads in south Eloy.

Based on this information, ADEQ recommends leav ing unchanged the designation of Pima County as attainment/unclassifiable. Including Pima County woul d not help Pinal County reach attainment of the NAAQS and could pose jurisdictional boundary complic ations. In addition, there are no topographical features or meteorological patterns affecting airflow that would support including Pima County in the proposed nonattainment area.

Maricopa County

One PM 10 

### ambient air quality monitor near the border Mari copa/Pinal County border (the Combs School Monitor) has violated the 24-hour PM 10 

### NAAQS, as shown in the major features map on Page ES-2. Emissions from Maricopa County ma y be contributing to violations at that monitor; however, the adjoining portion of Maricopa County lies within the Phoenix PM 10 

### Planning Area, which was designated

as serious nonattainment for PM 10 

### in 1996 based on urbanized area emissions [61 FR 21372]. 10



### The Maricopa Association of Governments (MAG) submitted a PM 10 

### SIP for the Phoenix area in July 1999, and a revision of that plan in February 2000 . At EPA’s request, MAG submitted another revision,

the Salt River PM 10 

### SIP Revision, in 2002 that focused on achieving attainment in the Salt River bed area of Phoenix. After failing to achieve attainment of the PM 10 

### NAAQS, in December 2007, MAG submitted

the Five Percent Plan for PM 10 

### for the Maricopa County Nonattainment Area . The Five Percent Plan contains 46 control measures designed to reduce PM 10 

### emissions in Area A each successive year by five percent, in addition to the best available contro l measures (BACM) and most stringent measures (MSM) already in the serious area plan. In combinati on, these requirements impose the most stringent

8 The Hayden PM 10 nonattainment area was most recently defined in 72 FR 14422 (3/28/07).

9 The Rillito portion of Pima County was designated as nonattainment for PM 10 by operation of law following the CAA amendments of 1990. In October 2006, EPA gave the Rillito Nonattai nment Area (RNA) a clean data finding based on several years of attaining the PM 10 NAAQS. ADEQ submitted a Limited Maintenance Plan for the RNA in June 2008.

10 The 36-square-mile Apache Junction area in the northernmost portion of Pinal County c onstitutes part of the Phoenix Planning Area and was designated with the Phoenix metro area as serious nonattainment for the 24-hour PM 10 NAAQS in 1996. As with the urban areas of Maricopa County, inclusion of Apache Juncti on in a greater-Pinal nonattainmen t area would be redundant and would complicate jurisdictional boundaries.

### 32 combination of State implementation plan ("SIP") mandates that can be required under the CAA. The inclusion of Maricopa County in a Pinal C ounty nonattainment area would be unnecessary, would complicate jurisdictional boundaries, and would not help Pinal County reach attainment of the PM 10 

### NAAQS.

3.10 Nonattainment Area Summary of Criteria Analysis

ADEQ reviewed the nine criteria outlined in EPA's gui dance and determined that the portions of Pinal County discussed in this section meet the criteria for inclusion in a PM 10 

### nonattainment area. Table 3-8 summarizes the data and information supportin g the nonattainment area recommendation.

### 33 Table 3-8 Summary of Nine Criteria Analysis for the Proposed Pinal County PM 10 Nonattainment Area

Criteria Factors Supporting the Recommended Nonattainment Area Boundary Factors Supporting the Exclusion of Eastern Portions of Pinal County Air Quality

Data The proposed nonattainment area includes

the locations of the monitors that recorded concentrations exceeding the NAAQS. Ambient air quality monitors located in the eastern and southern region of the County are not violating

the PM 10 NAAQS.

Emissions

Data The preliminary emissions inventory prepared by ADEQ and PCAQD determined that the majority of PM 10 emissions originate in the western and central regions of the County. The preliminary emissions inventory determined that sources in the eastern and southern regions of the County do not significantly contribute to violations in other regions of the County.

Population Density and Degree of

Urbanization The urbanized areas in the western and central regions of the County are where 95 percent of the County’s population resides. The eastern and southern portions of the County are largely undeveloped and have very low population

densities.

Traffic and Commuting

Patterns The recommended nonattainment area includes the rapidly growing urbanized and developed areas, the high-traffic Interstate corridors, and areas with the highest employment densities. The number of employers in the eastern portion of the County is low and is not projected to substantially increase during the potential maintenance period (2011-2031).

Growth Rates

and Patterns Significant growth is projected for communities near I-10 and I-8 during the potential maintenance period (2011-2031). The eastern region of the county has experienced limited growth and is not projected significantly

increase.
Meteorology The recommended nonattainment area includes the agricultural basin region of the County where stagnation conditions are known to impact PM 10 concentrations. There are no known meteorology conditions specific to the eastern por tion of the County known

to affect PM 10 concentrations.

Geography/ Topography The recommended nonattainment area is predominately located in the basin region of the County characterized by open-ended valleys with few topographic barriers. The eastern portion of the County is characterized by rough terrain, steep mountain ranges reaching over 7,000 feet in elevation.

Jurisdictional

Boundaries ADEQ’s recommendation maintains jurisdictional cohesiveness and requires no new institutional arrangements for accomplishing required tasks. The eastern portions of Pinal County recommended as attainment/unclassifiable designation lack significant emission source s or are in the existing Hayden PM 10 nonattainment area. Inclusion of these areas would not help bring the western region of the county into attainment.

Level of

Control of

Emission

Sources The Apache Junction area of the County

included in the Phoenix PM 10 Nonattainment Area is subject to stringent

PM 10 control strategies included in the Maricopa Association of Governments Five

Percent Reduction Plan. The number of PM 10 generating sources in eastern Pinal County is minimal. The largest point source in the area, ASARCO’s Ray Mine, is included in the existing Hayden PM 10 Nonattainment Area. The operating permit issued by PCAQCD for the mine contains control measures sufficient for attaining

the PM 10 NAAQS. Emissions from the mine are highly localized and do not affect the recommended

nonattainment area.

### 34 4.0 AREA DESIGNATION RECOMMENDATIONS

ADEQ demonstrated in the preceding analysis that th e western and central regions of Pinal County should be designated as nonattainment for the 1987 24-hour PM 10 

### NAAQS. The proposed Pinal County PM 10 

### nonattainment area encompasses all or part of those townships listed below. Those sections of Pinal County not listed are recommended as attainment/unclassifiable.

As a new 24-hour PM 10 

### nonattainment planning area, the State is recommending those portions of Pinal County shown in Figure 4-1 as the nonattainment planning area for the 24-hour PM 10 

### NAAQS. This area excludes Indian Country in the affected portion of Pinal County.

T1S, R8E T2S, R8E T3S, R7E T3S, R8E T4S, R3E-R4E (excluding all lands within the G ila River and Ak-Chin Indian Communities) T4S, R8E (excluding all lands within the Gila River Indian Community) T5S, R3E (excluding all lands within the Ak-Chin Indian Community) T5S, R4E – R8E (excluding all lands within th e Gila River and Ak-Chin Indian Communities) T6S, R3E – R8E T7S, R3E – R8E Sections 1-635Figure 4-1

### Appendix A 2006-2008 Summary of Pinal County Ambient PM 10 

### Monitoring Data

### 37 This page is intentionally blank38Appendix A – 2006-2008 Summary Pinal County PM10Monitoring Data ( inμg/m3)YearMonitor# ofObservationsMax 24-hourConcentration2ndHighestConcentration3rdHighestConcentration4thHighestConcentration# ofExceedances2006Apache Jct. Fire Station 59 73 53 43 42 0Casa Grande 60 81 81 81 72 0Coolidge 58 106 84 83 80 0Cowtown 57 606 531 510 460 39Eloy 55 99 96 94 79 0Mammoth 55 31 28 26 26 0Maricopa 361 429 389 330 329 21Pinal Air Park 57 77 67 67 62 0Pinal County Housing 58 153 152 141 126 0Pinal County Housing E. 58 210 170 158 138 3Pinal County Housing TEOM 356 913 763 552 432 33Riverside 56 83 45 43 38 0Stanfield 58 182 161 148 140 2Stanfield TEOM 327 727 469 353 251 252007Apache Jct. Fire Station54484039290Casa Grande571128069640Combs School28297086752138531Coolidge57827674730Cowtown5575949039638324Eloy (620 N. Main St.)10463633330Eloy (801 N. Main St.)5013612796950Mammoth56402926260Maricopa36372452533232920Pinal Air Park571136160570Pinal County Housing59224113110991Pinal County Housing E.603411451401201Pinal County Housing TEOM3542,2531,83944843419Riverside56655349490Stanfield583743502922496Stanfield TEOM3581,062482360357252008Apache Jct. Fire Station 45 57 32 32 31 0Casa Grande 44 74 54 42 40 0Combs School 366 270 195 192 171 4Coolidge 45 55 53 52 50 0Cowtown 60 465 373 354 339 24Eloy 40 109 63 61 58 0Mammoth 44 35 32 27 27 0Maricopa 361 520 317 213 170 6Pinal Air Park 46 53 42 42 42 0Pinal County Housing 44 141 75 69 68 0Pinal County Housing E.46 245 99 83 82 1Pinal County Housing TEOM357 285 274 265 221 10Riverside 44 44 37 36 36 0Stanfield 61 201 185 149 128 2Stanfield TEOM 363 375 364 323 264 1439This page is intentionally blank.

### 40 Appendix B 2006-2008 Summary of Pinal County PM 10 

### Exceedances

### 41 This page is intentionally blank.12006 Pinal County PM10Exceedances48 Exceedance days(19 – stagnation, 28 – wind, combo – 1)DateDay of WeekSiteAQS # (POC)PM1024-hr AverageConcentration (ug/m3)Weather Type(Wind, Stagnation, Monsoon)1/5/06 Thursday PCH (TEOM)04-021-3011 (3) 187.5 Wind1/7/06 Saturday PCH (TEOM)04-021-3011 (3) 158.2 Stagnation1/12/06 Thursday PCH (TEOM)04-021-3011 (3) 164.3 Stagnation1/13/06 Friday Maricopa 04-021-3010 (3) 174.6 Stagnation1/18/06 Wednesday PCH (TEOM) 04-021-3011 (3) 172.8 StagnationMaricopa 04-021-3010 (3) 191.11/19/06 ThursdayPCH (TEOM)04-021-3011 (3) 171.9Wind1/25/06 Wednesday PCH (TEOM)04-021-3011 (3) 177.6 WindPCH (TEOM)04-021-3011 (3) 204.62/4/06 SaturdayPCH east 04-021-3011 (2) 158StagnationPCH (TEOM) 04-021-3011 (3) 366.22/6/06 MondayStanfield 04-021-3008 (3) 198.7Wind2/8/06 Wednesday PCH (TEOM)04-021-3011 (3) 157.7 Wind2/9/06 Thursday PCH (TEOM)04-021-3011 (3) 222.3 StagnationPCH (TEOM)04-021-3011 (3) 432.1Maricopa 04-021-3010 (3) 3892/15/06 WednesdayStanfield 04-021-3008 (3) 248.4Wind2/17/06 Friday PCH (TEOM)04-021-3011 (3) 164.3 Stagnation2/18/06 Saturday PCH (TEOM)04-021-3011 (3) 164.1 StagnationMaricopa 04-021-3010 (3) 190.43/8/06 WednesdayPCH (TEOM) 04-021-3011 (3) 173.1Wind3/10/06▲Friday Maricopa 04-021-3010 (3) 289.6 WindPCH (TEOM) 04-021-3011 (3) 552.4Maricopa 04-021-3010 (3) 329.6▲Included with ADEQ NEAP to EPA22006 Pinal County PM10ExceedancesDateDay of WeekSiteAQS # (POC)PM1024-hr AverageConcentration (ug/m3)Weather Type(Wind, Stagnation, Monsoon)PCH (TEOM) 04-021-3011 (3) 336.9Stanfield 04-021-3008 (3) 205.95/16/06 TuesdayMaricopa 04-021-3010 (3) 187.1Wind5/17/06 Wednesday PCH (TEOM) 04-021-3011 (3) 203.3 Wind5/22/06▲Monday Maricopa 04-021-3010 (3) 173.2 Wind6/1/06 Thursday Stanfield 04-021-3008 (3) 160.6 Stagnation6/2/06▲Friday Maricopa 04-021-3010 (3) 231.7 Combo6/4/06 Sunday Stanfield 04-021-3008 (3) 164.9 Wind6/6/06▲Tuesday Stanfield 04-021-3008 (3) 237.5 Wind6/24/06 Saturday Maricopa 04-021-3010 (3) 208.4 WindPCH (TEOM) 04-021-3011 (3) 762.8Stanfield 04-021-3008 (3) 468.86/25/06▲SundayMaricopa 04-021-3010 (3) 329.1WindMaricopa 04-021-3010 (3) 4296/26/06 MondayStanfield 04-021-3008 (3) 167.3WindPCH (TEOM) 04-021-3011 (3) 393.77/4/06 TuesdayPCH east 04-021-3011 (2) 210WindStanfield 04-021-3008 (3) 237.47/15/06 SaturdayMaricopa 04-021-3010 (3) 204.5WindPCH (TEOM) 04-021-3011 (3) 268.77/16/06 SundayPCH east 04-021-3011 (2) 170Wind7/18/06 Tuesday PCH (TEOM)04-021-3011 (3) 186.7 Wind7/25/06 Tuesday PCH (TEOM)04-021-3011 (3) 237.7 Wind8/21/06 Monday Maricopa 04-021-3010 (3) 218 Wind10/5/06 Thursday Maricopa04-021-3010 (3) 159.5 Stagnation10/19/06 Thursday Stanfield 04-021-3008 (3) 162.5 Stagnation11/6/06 Monday Stanfield 04-021-3008 (3) 164.9 Stagnation11/13/06 Monday PCH (TEOM)04-021-3011 (3) 158.1 Stagnation11/17/06 Friday PCH (TEOM)04-021-3011 (3) 246.5 Stagnation▲Included with ADEQ NEAP to EPA32006 Pinal County PM10ExceedancesDateDay of WeekSiteAQS # (POC)PM1024-hr AverageConcentration (ug/m3)Weather Type(Wind, Stagnation, Monsoon)11/18/06 Saturday Maricopa04-021-3010 (3) 155 StagnationPCH (TEOM) 04-021-3011 (3) 257.611/29/06 WednesdayMaricopa 04-021-3010 (3) 250.1Wind12/3/06 Sunday PCH (TEOM) 04-021-3011 (3) 294.3 Wind12/4/06 Monday Stanfield 04-021-3008 (3) 224.4 Wind12/12/06 Tuesday PCH (TEOM)04-021-3011 (3) 167.4 Stagnation12/13/06 Wednesday PCH (TEOM)04-021-3011 (3) 155.7 StagnationPCH (TEOM)04-021-3011 (3) 175.312/14/06 ThursdayStanfield 04-021-3008 (3) 155.6StagnationPCH (TEOM) 04-021-3011 (3) 182.9Stanfield 04-021-3008 (3) 162.212/15/06 FridayMaricopa 04-021-3010 (3) 156.7StagnationMaricopa 04-021-3010 (3) 202.6PCH (TEOM) 04-021-3011 (3) 202.512/16/06 SaturdayStanfield 04-021-3008 (3) 194.1Wind12/27/06 Wednesday Stanfield 04-021-3008 (3) 170.8 Wind▲Included with ADEQ NEAP to EPA42007 Pinal County PM10Exceedances52 Exceedance days(17 – stagnation, 34 – wind, combo – 1)DateDay ofWeekSiteAQS # (POC)PM1024-hr AverageConcentration (ug/m3)Weather Type(Wind, Stagnation, Monsoon)Stanfield 04-021-3008 (3) 260Stanfield 04-021-3008 (1) 248.32/23/07*FridayPCH (TEOM) 04-021-3011 (3) 189.4Wind3/4/07*Sunday PCH (TEOM) 04-021-3011 (3) 241.7 WindCombs 04-021-3009 (3) 273.23/21/07*WednesdayPCH (TEOM) 04-021-3011 (3) 184.3WindStanfield 04-021-3008 (3) 482.3Maricopa 04-021-3010 (3) 268.73/27/07*†TuesdayCombs 04-021-3009 (3) 170.1WindPCH (TEOM) 04-021-3011 (3) 447.7PCHeast04-021-3011 (2) 341PCH 04-021-3011 (1) 224.1Stanfield 04-021-3008 (2) 349.9Stanfield 04-021-3008 (3) 347.7Maricopa 04-021-3010 (3) 259.9Casa Grande 04-021-0001 (3) 221.14/12/07*†ThursdayCombs 04-021-3009 (3) 160.2Wind4/15/07*Sunday PCH (TEOM) 04-021-3011 (3) 221.4 WindMaricopa 04-021-3010 (3) 525.14/28/07*SaturdayStanfield 04-021-3008 (3) 360.1WindPCH (TEOM) 04-021-3011 (3) 2,252.85/1/07*TuesdayCombs 04-021-3009 (3) 214.6WindPCH (TEOM) 04-021-3011 (3) 434Combs 04-021-3009 (3) 326.25/8/07*TuesdayStanfield 04-021-3008 (3) 206.1Wind*PCAQCD flagged exceptional/natural event†ADEQ flagged exceptional/natural event52007 Pinal County PM10ExceedancesDateDay ofWeekSiteAQS # (POC)PM1024-hr AverageConcentration (ug/m3)Weather Type(Wind, Stagnation, Monsoon)5/12/07 Saturday PCH (TEOM) 04-021-3011 (3) 205.1 Wind?5/16/07 Wednesday Combs 04-021-3009 (3) 167.8 WindPCH (TEOM) 04-021-3011 (3) 414.2Combs 04-021-3009 (3) 360.5Stanfield 04-021-3008 (3) 273.46/6/07*†WednesdayMaricopa 04-021-3010 (3) 213.4WindStanfield 04-021-3008 (2) 291.8Stanfield 04-021-3008 (3) 285.5Combs 04-021-3009 (3) 237.46/11/07*MondayMaricopa 04-021-3010 (3) 158.3Wind6/14/07 Thursday Stanfield 04-021-3008 (3) 170.3 Stagnation6/15/07 Friday Combs 04-021-3009 (3) 171.8 Stagnation6/17/07 Sunday Stanfield 04-021-3008 (2) 182.9 Combo (wind & stagnation)6/18/07 Monday Combs 04-021-3009 (3) 208.7 StagnationCombs 04-021-3009 (3) 211.67/5/07*ThursdayPCH (TEOM) 04-021-3011 (3) 196.7WindCombs 04-021-3009 (3) 521.4Stanfield 04-021-3008 (3) 347.6Casa Grande 04-021-0001 (3) 255.77/6/07*FridayMaricopa 04-021-3010 (3) 232WindStanfield 04-021-3008 (3) 251Combs 04-021-3009 (3) 223.87/16/07*MondayPCH (TEOM)04-021-3011 (3) 199.3WindPCH (TEOM)04-021-3011 (3) 1,838.6Stanfield 04-021-3008 (3) 1,062.2Casa Grande 04-021-0001 (3) 983.4Combs 04-021-3009 (3) 866.97/19/07*†ThursdayMaricopa 04-021-3010 (3) 724.4Wind7/23/07*Monday Combs 04-021-3009 (3) 160.9 Wind* PCAQCD flagged exceptional/natural event†ADEQ flagged exceptional/natural event62007 Pinal County PM10ExceedancesDateDay ofWeekSiteAQS # (POC)PM1024-hr AverageConcentration (ug/m3)Weather Type(Wind, Stagnation, Monsoon)Maricopa 04-021-3010 (3) 331.7Combs 04-021-3009 (3) 248.48/13/07*†MondayPCH (TEOM) 04-021-3011 (3) 202.6WindCombs 04-021-3009 (3) 969.5Maricopa 04-021-3010 (3) 249.4Stanfield 04-021-3008 (2) 247.9PCH (TEOM) 04-021-3011 (3) 184.48/16/07*†ThursdayCasa Grande 04-021-0001 (3) 163.6WindCombs 04-021-3009 (3) 230.9Stanfield 04-021-3008 (3) 216.28/23/07*†ThursdayMaricopa 04-021-3010 (3) 203.8WindCombs 04-021-3009 (3) 197.78/24/07*FridayCasa Grande 04-021-0001 (3) 188.2Carryover/windPCH (TEOM) 04-021-3011 (3) 253.98/29/07*WednesdayStanfield 04-021-3008 (3) 159.4WindCombs 04-021-3009 (3) 2838/30/07*ThursdayMaricopa 04-021-3010 (3) 158.5Wind9/1/07*Saturday Maricopa 04-021-3010 (3) 197.5 WindCombs 04-021-3009 (3) 296.9Stanfield 04-021-3008 (3) 177.410/5/07*†FridayMaricopa 04-021-3010 (3) 157.5Wind10/8/07 Monday Combs 04-021-3009 (3) 167 Stagnation10/9/07 Tuesday Combs 04-021-3009 (3) 166 Stagnation10/10/07 Wednesday Combs 04-021-3009 (3) 187.7 Stagnation10/11/07Thursday Maricopa 04-021-3010 (3) 189.3 Stagnation10/12/07 Friday Maricopa 04-021-3010 (3) 170.6 Stagnation (PM10hourly peak of 1,055 ug/m3 & peakwind was only 13 mph (both at 3 p.m.).10/16/07 Tuesday Maricopa 04-021-3010 (3) 213 Carryover/Wind*PCAQCD flagged exceptional/natural event†ADEQ flagged exceptional/natural event72007 Pinal County PM10ExceedancesDateDay ofWeekSiteAQS # (POC)PM1024-hr AverageConcentration (ug/m3)Weather Type(Wind, Stagnation, Monsoon)Stanfield 04-021-3008 (3) 186.610/16/07*TuesdayCombs 04-021-3009 (3) 164.8WindCombs 04-021-3009 (3) 207.8 Combo10/19/07 FridayMaricopa 04-021-3010 (3) 166.6 StagnationStanfield 04-021-3008 (2) 397.1Stanfield 04-021-3008 (3) 356.8Maricopa 04-021-3010 (3) 328.910/21/07*†SundayCombs 04-021-3009 (3) 166.2Wind10/23/07*Tuesday Stanfield 04-021-3008 (3) 184 Wind10/24/07*†Wednesday Combs 04-021-3009 (3) 385.2 Wind10/26/07 Friday Combs 04-021-3009 (3) 157.3 Stagnation10/29/07*Monday Maricopa 04-021-3010 (3) 156.2 Wind11/3/07 Saturday Stanfield 04-021-3008 (3) 176.9 Stagnation11/5/07 Monday Stanfield 04-021-3008 (3) 159.1 Stagnation11/6/07 Tuesday PCH (TEOM) 04-021-3011 (3) 164.8 StagnationStanfield 04-021-3008 (3) 246.6PCH (TEOM) 04-021-3011 (3) 217.2Combs 04-021-3009 (3) 190.6Casa Grande 04-021-0001 (3) 17211/15/07*ThursdayMaricopa 04-021-3010 (3) 162.6Wind11/21/07 Wednesday PCH (TEOM)04-021-3011 (3) 181.4 Stagnation11/28/07 Wednesday Combs 04-021-3009 (3) 170.2 StagnationPCH (TEOM) 04-021-3011 (3) 272Stanfield 04-021-3008 (3) 257.112/7/07*FridayCasa Grande 04-021-0001 (3) 156.5Wind12/25/07*Tuesday Stanfield 04-021-3008 (3) 298.2 Wind* PCAQCD flagged exceptional/natural event†ADEQ flagged exceptional/natural event82008 Pinal County PM10Exceedances21 Exceedance days [5 stagnation, 16 wind]DateDay of WeekSiteAQS # (POC)PM1024-hr AverageConcentration (ug/m3)Weather Type(Wind, Stagnation, Monsoon)PCH (TEOM) 04-021-3011 (3) 264.9PCHEast04-021-3011 (2) 245Stanfield 04-021-3008 (3) 255.31/1/08*TuesdayStanfield 04-021-3008 (1) 185Wind from Strong Pressure Gradient(Max. wind speed 31 mph)4/26/08 Saturday Stanfield 04-021-3008 (3) 207.5 Stagnation5/10/08 Saturday Stanfield 04-021-3008 (3) 161.7 Stagnation5/15/08*Thursday PCH (TEOM) 04-021-3011 (3) 221.1 Storm Outflow Winds (Max. wind speed 32 mph)Stanfield 04-021-3008 (3) 323.0Maricopa 04-021-3010 (3) 317.7PCH (TEOM) 04-021-3011 (3) 273.8Combs 04-021-3009 (3) 170.75/21/08*†WednesdayCasa Grande 04-021-0001 (3) 164.2Cold Frontal Passage (Max. wind speed 39 mph)7/1/08*†Tuesday PCH (TEOM) 04-021-3011 (3) 159.2 Monsoon Storm Outflow (Max. wind speed 31 mph)7/3/08*Thursday Stanfield 04-021-3008 (3) 157.8 Monsoon Storm Outflow (Max. wind speed 27 mph)Stanfield 04-021-3008 (3) 364.38/7/08*ThursdayMaricopa 04-021-3010 (3) 213.3Monsoon Storm Outflow (Max. wind speed 41 mph)8/15/08*Friday PCH (TEOM) 04-021-3011 (3) 204.1 Monsoon Storm Outflow (Max. wind speed 40 mph)9/8/08*Monday Stanfield 04-021-3008 (3) 264.2 Monsoon Storm Outflow (Max. wind speed 40 mph)PCH (TEOM) 04-021-3011 (3) 217.1Casa Grande 04-021-0001 (3) 202.5Combs 04-021-3009 (3) 194.7Stanfield 04-021-3008 (3) 178.29/11/08*ThursdayMaricopa 04-021-3010 (3) 170.4Monsoon Storms Outflow (Max. wind speed 43 mph)9/29/08*Monday Combs 04-021-3009 (3) 192.1Wind from Strong Pressure Gradient(Max. wind speed 28 mph)10/11/08*Saturday Maricopa 04-021-3010 (3) 157.0Strong low pressure systemMax. wind speed 23 mph*PCAQCD flagged exceptional/natural event†ADEQ flagged exceptional/natural event (ADEQ flagging up to 7/4/08)92008 Pinal County PM10ExceedancesDateDay of WeekSiteAQS # (POC)PM1024-hr AverageConcentration (ug/m3)Weather Type(Wind, Stagnation, Monsoon)Stanfield 04-021-3008 (3) 212.6Stanfield 04-021-3008 (1) 20110/27/08*MondayMaricopa 04-021-3010 (3) 159.4Pressure gradient/back door cold front(Max. wind speed 28 mph)PCH (TEOM) 04-021-3011 (3) 178.010/29/08 WednesdayStanfield 04-021-3008 (3) 162.1Stagnation10/31/08 Friday PCH (TEOM) 04-021-3011 (3) 159.3 StagnationMaricopa 04-021-3010 (3) 520.3Stanfield 04-021-3008 (3) 375.1PCH (TEOM) 04-021-3011 (3) 285.2Combs 04-021-3009 (3) 270.011/9/08*SundayCasa Grande 04-021-0001 (3) 182.9Wind from strong cold front(Max. wind speed 38 mph)11/15/08*Saturday Stanfield 04-021-3008 (3) 240.7Wind from strong pressure gradient(Max. wind speed 30 mph)11/20/08 Thursday PCH (TEOM)04-021-3011 (3) 160.6 Stagnation11/21/08*Friday Stanfield 04-021-3008 (3) 178.6Wind from strong pressure gradient(Max. wind speed 29 mph)12/13/08*Saturday Stanfield 04-021-3008 (3) 178.2Wind from strong cold front(Max. wind speed 26 mph)* PCAQCD flagged exceptional/natural event†ADEQ flagged exceptional/natural event (ADEQ flagging up to 7/4/08)10This page is intentionally blank.