Pinal County Air Quality Control District 

2009 Ambient Monitoring 

Network Plan 

And 

2008 Data Summary

June 30, 2009 - Final 

Pinal County Air Quality 

31 N. Pinal St., Bldg. F 

P.O. Box 987 

Florence AZ, 85232 

(520) 866-6929 

www.pinalcountyaz.gov
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Table of Contents 

1.0 NATIONAL AMBIENT AIR QUALITY STANDARDS (NAAQS) 13 

2.0 MONITORING OBJECTIVES AND SPATIAL SCALES 17 

3.0 NETWORK DESIGN AND MEASUREMENT QUALITY 21 

3.1 NETWORK DESIGN 21 

3.2 AQS REQUIREMENTS 22 

3.3 MINIMUM NETWORK REQUIREMENTS 22 

3.4 MINIMUM SAMPLE FREQUENCY 24 

3.5 MEASUREMENT QUALITY CHECKS 25 

3.6 OZONE SEASON DEFINITION 25 

3.7 QUALITY SYSTEM REQUIREMENTS 27 

3.8 LEAD MONITORING NETWORK DESCRIPTION 27 

4.0 MONITORING SITE DESCRIPTIONS 29 

4.1 APACHE JUNCTION FIRE STATION 29 

4.2 APACHE JUNCTION MAINTENANCE YARD 29 

4.3 CASA GRANDE AIRPORT 30 

4.4 CASA GRANDE DOWNTOWN 31 

4.5 COMBS SCHOOL 31 

4.6 COOLIDGE MAINTENANCE YARD 31 

4.7 COWTOWN 32 

4.8 ELOY COUNTY COMPLEX 34 

4.9 MAMMOTH COUNTY COMPLEX 34 

4.10 MARICOPA COUNTY COMPLEX (CITY OF MARICOPA) 34 

4.11 PINAL AIR PARK 35 

4.12 PINAL COUNTY HOUSING COMPLEX 35 

4.13 RIVERSIDE MAINTENANCE YARD 36 

4.14 STANFIELD COUNTY COMPLEX 36 

4.15 QUEEN VALLEY 37 

5.0 PROPOSED CHANGES TO THE NETWORK 39 

5.1 GILA RIVER BASIN 39 

5.2 CASA GRANDE DOWNTOWN PM2.5 39 

5.3 PINAL COUNTY HOUSING RELOCATION 39 

5.4 MEDIUM VOLUME PRECISION MEASUREMENT 39 

6.0 DATA TRENDS 41 

6.1 CARBON MONOXIDE 42 

6.2 OZONE 43 

6.2.1 ONE-HOUR OZONE 44 

6.2.2 EIGHT-HOUR OZONE 45 

6.3 PARTICULATE MATTER SMALLER THAN 10 MICRONS (PM10) 46 

6.3.1 24-HOUR PM10 TRENDS 48 

6.3.2 ANNUAL PM10 TRENDS 50 

6.4 PARTICULATE MATTER SMALLER THAN 2.5 MICRONS (PM2.5) 53 

6.4.1 PM2.5 24-HOUR TRENDS 54 

6.4.2 PM2.5 ANNUAL TRENDS 55 
6
7

Appendices 

APPENDIX A: ABBREVIATIONS 57 

APPENDIX B: PCAQCD SITE DESCRIPTIONS 61 

 

APPENDIX C: PCAQCD AMBIENT AIR MONITORING DATA 81 

APPENDIX D: PUBLIC COMMENTS 99 

 
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9

Introduction 

This document provides two distinct products: 1) a description of the Pinal County Air Quality 

monitoring system in the form of an Annual Monitoring Network Plan, and 2) a summary of data 

obtained from the network. 

40 Code of Federal Regulations (CFR) Part 58.10 requires an annual monitoring network plan to 

summarize the air quality surveillance system consisting of State and Local Air Monitoring 

Stations (SLAMS) and Special Purpose Monitors (SPM) operated under state and local authority. 

According to the regulation, the Annual Monitoring Network Plan must be submitted to the 

Regional Administrator by July 1 each year. 

The annual monitoring network plan must identify the purpose of each monitor and provide 

evidence that both the siting and the operation of each monitor meet the requirements in 40 CFR 

Part 58 appendices A, C, D, and E below: 

• Appendix A – Quality Assurance Requirements for SLAMS, SPMs, and PSD (Prevention of 

Significant Deterioration) Air Monitoring 

• Appendix C – Ambient Air Quality Monitoring Methodology 

• Appendix D – Network Design Criteria for Ambient Air Quality Monitoring 

• Appendix E – Probe and Monitoring Path Siting Criteria for Ambient Air Quality Monitoring 

Pinal County Air Quality operates air quality monitors that record ambient concentrations of 

several criteria pollutants. Criteria pollutants are those that the United States Environmental 

Protection Agency (EPA) has defined as a potential risk to health, and correspondingly defined a 

National Ambient Air Quality Standard (NAAQS).1

 The standards are intended to protect public 

health and welfare by setting limits on the allowable level of each pollutant in the ambient air. 

The criteria pollutants are particulate matter less than or equal to 10 microns (PM10), particulate 

matter less than or equal to 2.5 microns (PM2.5), ozone (O3), carbon monoxide (CO), sulfur 

dioxide (SO2), nitrogen dioxide (NO2), and lead (Pb). 

Areas in which monitored air quality shows that the NAAQS are violated are defined as 

nonattainment for the offending pollutant. A nonattainment designation requires an area-specific 

curative implementation plan, typically including stricter air quality permitting regulations on 

industrial facilities, mobile source emission controls and additional regulations on development. 

Generally, areas with monitored air quality that meet the standards are defined as attainment. 

Areas without sufficient monitoring data may also be defined as unclassifiable. Although the 

bulk of Pinal County is classified as attainment for all pollutants, Figure 1.1 illustrates the 

current pollutant-specific nonattainment areas in Pinal County. 

This document is arranged with several sections. Each section will address specific requirements 

of 40 CFR Part 58 or provide summary air quality data. The sections are organized accordingly: 

Sections 1 describes 40 CFR Part 58 defined monitoring objectives and scales of representation. 

Section 2 provides Pinal County’s network design, and measure of compliance with minimum 

site requirements, and an overview of how the Pinal County network achieves precision 

 

1

 See Clean Air Act (“CAA”) §§ 108,109, and 40 CFR §50.1 et seq.
10

measurements as required by the monitoring rules. Section 3 describes each site in the network 

and evaluates the sites for compliance with siting requirements set forth by EPA. Section 4 

describes the proposed changes to the monitoring network. Section 5 describes the NAAQS 

standard for each pollutant monitored by Pinal County Air Quality and compares the data 

collected to the standard. 

The appendices of this document presents a list of all the abbreviations used in the document 

(Appendix A), a picture and summary table for each monitoring site operated by Pinal County 

Air Quality (Appendix B), and a tabular summary of the monitoring data (Appendix C). 
 Figure 1.1 

13

1.0 National Ambient Air Quality Standards (NAAQS)

This section provides a brief description of the National Ambient Air Quality Standards 

(NAAQS) for ozone and particulate matter, the pollutants of primary concern in Pinal 

County. 

As background, the Clean Air Act requires EPA to set National Ambient Air Quality 

Standards (NAAQS) for six criteria pollutants; particle pollution (also known as 

particulate matter) is one of these. The Clean Air Act established two types of national air 

quality standards for particle pollution. Primary standards set limits to protect public 

health, including the health of "sensitive" populations such as asthmatics, children, and 

the elderly. Secondary standards set limits to protect public welfare, including protection 

against visibility impairment, damage to animals, crops, vegetation, and buildings. 

Ozone

The one-hour standard was established in 1971 and set at a level of 0.08 parts per million 

(ppm). In 1979, the standard was revised to 0.12ppm and was an exceedance based 

standard, which required that the number of expected exceedance be less than or equal to 

1.0. An exceedance of the one-hour ozone standard occurred if an observed one-hour 

average was greater than 0.120 ppm. Generally, the number of daily exceedances (only 

the daily maximum counts as an exceedance) equals the expected exceedance rate. Thus, 

the standard effectively allows only one exceedance to be recorded per calendar year. 

EPA updated the ozone standard in 1997 and created an 8-hour standard. The 8-hour 

primary ozone standard was 0.08 ppm. The decision to revise the standards was 

challenged in court by a number of parties and ultimately reached the U.S. Supreme 

Court. In 2001, the Court unanimously upheld the constitutionality of the 1970 Clean Air 

Act provision that authorizes EPA to set NAAQS to protect public health and welfare. 

EPA proceeded with implementing the 8-hour standard by making nonattainment 

designations in April 2004 and revoking the 1-hour standard in August 2005. 

The latest revision to the ozone NAAQS was made on March 12, 2008. The 8-hour 

standard was set to a level of 0.075 ppm. In addition to changing the level of the standard, 

EPA specified the level of the standard to the third decimal. An area will meet the revised 

standard if the three-year average of the annual fourth-highest daily maximum 8-hour 

average at every ozone monitor is less than or equal to 0.075 ppm. 

The Clean Air Act requires EPA to designate areas as attainment (meeting the standards), 

nonattainment (not meeting the standards), or unclassifiable (insufficient data to classify) 

after the Agency sets a new standard, or revises an existing standard. 

1. The following schedule will apply to the revised ozone standards: States must 

make recommendations to EPA no later than March 2009 for areas to be 

designated attainment, nonattainment and unclassifiable, 

2. EPA will issue final designations of attainment, nonattainment and unclassifiable 

areas no later than March 2010 unless there is insufficient information to make 

these designation decisions. In that case, EPA will issue designations no later than 

March 2011. 
14

3. States must submit State Implementation Plans outlining how they will reduce 

pollution to meet the standards by a date that EPA will establish in a separate rule. 

That date will be no later than three years after EPA’s final designations. If EPA 

issues designations in 2010, then these plans would be due no later than 2013. 

4. States are required to meet the standards by deadlines that may vary based on the 

severity of the problem in the area. 

EPA will issue a separate rule to address monitoring requirements necessary to 

implement the new standards. EPA intends to propose a monitoring rule in June 2008 and 

issue a final rule by March 2009. 

Table 1.1 

Key 

Year 

Action Level Averaging Period Form 

1979 1-hour standard revised 0.120ppm 1 hour Expected exceedance 

1997 8-hour standard proposed 0.08ppm 8 hour 3year average of the 4th

highest value 

2005 1-hour standard revoked (Applies only in limited areas) 

2008 8-hour standard revised 0.075ppm 8 hour 3year average of the 4th

highest value 

Table 1.2 

Ozone Primary Standards Secondary Standards 

Level Averaging Time Level Averaging Time 

0.075 ppm (2008 std) 8-hour 1 Same as Primary 

0.08 ppm (1997 std) 8-hour 2 Same as Primary 

0.12 ppm 1-hour 3

(Applies only in limited areas) Same as Primary 

1 To attain this standard, the 3-year average of the fourth-highest daily maximum 8-hour average ozone concentrations 

measured at each monitor within an area over each year must not exceed 0.075 ppm. (effective May 27, 2008) 

2 (a) To attain this standard, the 3-year average of the fourth-highest daily maximum 8-hour average ozone concentrations 

measured at each monitor within an area over each year must not exceed 0.08 ppm. (b) The 1997 standard—and the 

implementation rules for that standard—will remain in place for implementation purposes as EPA undertakes rulemaking to 

address the transition from the 1997 ozone standard to the 2008 ozone standard. 

3 (a) The standard is attained when the expected number of days per calendar year with maximum hourly average 

concentrations above 0.12 ppm is < 1. (b) As of June 15, 2005 EPA revoked the 1-hour ozone standard in all areas except 

the 8-hour ozone nonattainment Early Action Compact (EAC) areas. 

Particulate Matter (PM10 and PM2.5) 

The nation's air quality standards for particulate matter were first established in 1971 and 

were not significantly revised until 1987, when EPA changed the indicator of the 

standards to regulate inhalable particles smaller than, or equal to, 10 micrometers in 

diameter (that's about 1/4 the size of a single grain of table salt). 

Ten years later, after a lengthy review, EPA revised the PM standards, setting separate 

standards for fine particles (PM2.5) based on their link to serious health problems ranging 

from increased symptoms, hospital admissions and emergency room visits for people 

with heart and lung disease, to premature death in people with heart or lung disease. 
15

The 1997 standards also retained slightly revised standards for PM10 which were intended 

to regulate "inhalable coarse particles" that ranged from 2.5 to 10 micrometers in 

diameter. PM10 measurements, however, contain both fine and coarse particles. 

EPA revised the air quality standards for particle pollution in 2006. The 2006 standards 

tighten the 24-hour fine particle standard from the current level of 65 micrograms per 

cubic meter (μg/m3

) to 35 μg/m3, and retain the current annual fine particle standard at 15 

μg/m3

. The Agency decided to retain the existing 24-hour PM10 standard of 150 μg/m3. 

The Agency revoked the annual PM10 standard, because available evidence does not 

suggest a link between long-term exposure to PM10 and health problems. 

The Clean Air Act requires EPA to review the latest scientific information and standards 

every five years. Before new standards are established, policy decisions undergo rigorous 

review by the scientific community, industry, public interest groups, the general public 

and the Clean Air Scientific Advisory Committee (CASAC). 

Table 1.3 

National Ambient Air Quality Standards for Particle Pollution 

Pollutant Primary Standard Averaging Times Secondary Standard 

Particulate Matter (PM10) Revoked (1) Annual (1) (Arith. Mean) 

 150 μg/m3 24-hour (2) Same as Primary 

Particulate Matter (PM2.5) 15.0 μg/m3 Annual (3) (Arith. Mean) Same as Primary 

 35 μg/m3 24-hour (4) Same as Primary 

Footnotes: 

(1) - Due to a lack of evidence linking health problems to long-term exposure to coarse particle pollution, the agency 

revoked the annual PM10 standard in 2006 (effective December 17, 2006). 

(2) - Not to be exceeded more than once per year on average over 3 years. 

(3) - To attain this standard, the 3-year average of the weighted annual mean PM2.5 concentrations from single or 

multiple community-oriented monitors must not exceed 15.0 μg/m3

. 

(4) - To attain this standard, the 3-year average of the 98th percentile of 24-hour concentrations at each populationoriented monitor within an area must not exceed 35 μg/m3

 (effective December 17, 2006). 

Lead 

On October 15, 2008, EPA substantially strengthened the national ambient air quality 

standard for lead. The revised standards are 10 times tighter than the previous standards, 

set in 1978. EPA revised the level of the primary (health-based) standard from 1.5 

micrograms per cubic meter (μg/m3), to 0.15 μg/m3, measured as total suspended 

particles (TSP). The secondary (welfare-based) standard is identical in all respects to the 

primary standard. 

The averaging time and form of the lead standard were also revised. The calculation 

method for the averaging time was changed to use to a ‘rolling’ three month period with a 

maximum (not-to-be-exceeded) form, evaluated over a three-year period. This replaces 

the current approach of using calendar quarters. A rolling three month average considers 
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each of the 12 three-month periods associated with a given year, not just the four calendar 

quarters within that year. 

EPA estimates that 236 new or relocated monitoring sites will be necessary to satisfy 

these monitoring requirements. Approximately half of all newly required monitors are to 

be operational by January 1, 2010, with the other half of the monitors operational by 

January 1, 2011. In addition, some existing lead monitors will be left in place and will 

continue to be used as part of the lead monitoring network.

National Ambient Air Quality Standards for Lead 

Pollutant Primary Standard Averaging Times Secondary 

Standard 

Lead (as measured by TSP) 1.5 μg/m3 (old standard) Avg. of Calendar Quarter Same as Primary 

Lead (as measured by TSP) 0.15 μg/m3 Rolling 3-Month Avg.1 Same as Primary 

Footnotes: 

(1) – Form of the standard requires evaluation of data collected over a 3 year period
17

2.0 Monitoring Objectives and Spatial Scales 

The design of an Ambient Air Quality Monitoring Network should meet six basic 

monitoring objectives listed in Appendix D of 40 CFR Part 58. These six objectives are: 

1. Determine the highest concentrations expected to occur in the areas covered by 

the network. 

2. Determine representative concentrations in areas of high population density. 

3. Determine the impact on ambient pollution levels of significant sources or source 

categories. 

4. Determine general background concentration levels. 

5. Determine the extent of regional pollutant transport among populated areas. 

6. Determine the welfare related impacts in more rural and remote areas in support 

of secondary standards. 

A State and Local Air Monitoring Station (SLAMS) network consists of monitoring 

stations that provide data to meet these monitoring objectives. Monitoring stations 

generally correspond to a spatial scale identified in 40 CFR Part 58 Appendix D. Spatial 

scale of representativeness is described in terms of the physical dimension of the air 

parcel nearest to a monitoring station throughout which actual pollutant concentrations 

are reasonably similar. Table 2.1 lists these spatial scales. 

Table 2.1: Spatial Scales 

Spatial Scale Dimension 

Microscale Several meters up to 100 meters 

Middle scale 100 meters up to 0.5 kilometers 

Neighborhood Scale 0.5 kilometers to 4.0 kilometers 

Urban Scale 4 kilometers to 50 kilometers 

Regional Scale Tens to hundreds of kilometers 

40 CFR Part 58 Appendix D also describes the relationship between the monitoring 

objectives and the spatial scales that are generally most appropriate for each objective. 

Table 2.2 summarizes this relationship. 

Table 2.2: Monitoring Objectives 

Monitoring Objective Appropriate Siting Scales 

Highest Concentration Micro, Middle, Neighborhood 

(Sometimes urban) 

Population Neighborhood, Urban 

Source Impact Micro, Middle, Neighborhood 

General / Background Neighborhood, Urban, Regional 

Regional Transport Urban / Regional 

Welfare-related impact Urban / Regional 

A Special Purpose Monitor (SPM) is a monitor that is included in an agency’s monitoring 

network, but not part of the SLAMS network. SPMs are generally used to monitor 

specific sources, although any of the above siting scales may be appropriate. In 

December 2006 the EPA revised 40 CFR 58.20 indicating that where a SPM operates for 

more than 24 months all data collected may be eligible for comparison to the relevant 

NAAQS. 
18

40 CFR Part 50 and 53 define Federal Reference Methods (FRM) and Federal Equivalent 

Methods (FEM), which provide precise methodology for quantifying ambient 

concentrations of air pollutants. FRMs are monitoring methods that are associated with 

the NAAQS for the pollutant described in the appendices to 40 CFR 50 and determined 

by EPA to be FRMs. FEMs are alternative monitoring methods that have been 

designated by EPA as obtaining "equivalent" results when compared to the FRM, as 

determined by 40 CFR 53. An additional option for air monitoring agencies is the 

Approved Regional Method (ARM). This designation requires the applying agency to 

conduct specific field testing and evaluation demonstrating that the method meets Class 

III precision and accuracy requirements listed in Subpart C of 40 CFR Part 53. 

Pinal County Air Quality uses FRMs to collect filter based PM10 and PM2.5 samples and 

Automated Equivalent Methods (FEMs) for continuous PM10 and ozone. 

Three types of PM10 monitors are used throughout the monitoring network: 1) the filterbased high-volume sampler, 2) filter based medium volume sampler, and 3) the Tapered 

Element Oscillating Microbalance (TEOM) which measures PM10 on a continuous basis. 

Two types of PM2.5 monitors are used throughout the monitoring network: 1) the filter 

based medium volume sampler equipped with the appropriate size fractioning device, and 

2) the FDMS TEOM (Filter Dynamic Measurement System) which measure PM2.5 on a 

continuous basis. Pinal County Air Quality has not pursued Approved Regional Method 

(ARM) designation for this instrument. 

 The Arizona Department of Environmental Quality (ADEQ) operated a sulfur dioxide 

(SO2) analyzer in San Manuel, Pinal County until December of 2007. The San Manuel 

site was discontinued as proposed in the SIP and Network Plan and subsequent 

attainment finding by EPA for the area. ADEQ retains authority to monitor copper 

smelters in Arizona. 

ADEQ operates ozone and trace level nitrogen oxide (NOx) analyzers at Queen Valley as 

a part of its PAMS network. There are currently no monitors in Pinal County that 

measure lead (Pb) although ADEQ operates samplers in other portions of the state that 

measure lead. Refer to the State of Arizona Monitoring Network Plan for information on 

these criteria pollutants. 

A process for relocating violating PM2.5 monitors is described at 40 CFR Part 58.10 (c). 

The rule requires that the annual monitoring network plan must document how States and 

local agencies provide for the review of changes to a PM2.5 monitoring network that 

impact the location of a violating PM2.5 monitor or the creation/change to a community 

monitoring zone, including a description of the proposed use of spatial averaging for 

purposes of making comparisons to the annual PM2.5 NAAQS as set forth in appendix N 

to 40 CFR Part 50. The affected State or local agency must document the process for 

obtaining public comment and include any comments received through the public 

notification process within their submitted plan. 

Pinal County Air Quality does not intend to establish community monitoring zones as 

described in the rule or utilize spatial averaging for comparison to the PM2.5 NAAQS. For 

the time period covered by this plan, Pinal County Air Quality does not intend to relocate 
19

any violating PM2.5 monitors. In the event that a violating PM2.5 monitor is relocated the 

following process will be utilized to address the required public comment process: 

1. Evaluation of the potential replacement site will include review and comparison 

of available pollutant data, meteorology, climatology, terrain, and siting 

characteristics. This information will be documented in a brief report. 

2. Make notice of such a change in the annual monitoring plan. 

3. If the change must be accomplished prior to annual monitoring plan submittal, 

Pinal County will make appropriate notice via the agency Web page and invite 

participation from the public prior to relocation of the affected site. 

4. Relocation of affected monitor. 
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21

3.0 Network Design and Measurement Quality 

3.1 Network Design 

This section provides a list of monitoring site designations. Table 3.1 and Table 3.2 

identify Pinal County Air Quality’s current SLAMS and SPM designations, respectively. 

The State Implementation Plan (SIP) as it applies to Pinal County does not make any 

SLAMS designations. In 2000 Pinal County compiled its first annual network review 

which included SLAM/SPM site designations. The past annual network reviews have 

been submitted to both ADEQ and EPA for comment. 

Table 3.1: SLAMS Summary 

Site Name AQS ID Classification Scale Objective Pollutant 

Apache Junction Fire Station 040213002 SLAMS Neighborhood Population PM2.5

Apache Junction Fire Station 040213002 SLAMS Neighborhood Population PM10

Apache Junction Maint.Yard 040213001 SLAMS Neighborhood Population O3

Casa Grande Airport 040213003 SLAMS Neighborhood Population O3

Casa Grande Downtown 040210001 SLAMS Neighborhood Population PM2.5

Casa Grande Downtown 040210001 SLAMS Neighborhood Population PM10

Coolidge Maintenance Yard 040213004 SLAMS Neighborhood Population PM10

Eloy City Complex 040213014 SLAMS Neighborhood Population PM10

Mammoth County Complex 040213006 SLAMS Neighborhood Population/ 

Background 

PM10

Pinal Air Park 040213007 SLAMS Regional Background PM10

Pinal County Housing 

Complex (HiVol) 

040213011 SLAMS Neighborhood Population PM10

Riverside Maintenance Yard 040213012 SLAMS Neighborhood SourceImpact PM10

Stanfield County Complex 040213008 SLAMS Neighborhood Population PM10

Table 3.2: SPM Summary 

Site Name AQS ID Classification Scale Objective Pollutant

Casa Grande Downtown 

TEOM 

040210001 SPM Neighborhood Population PM10

Combs School 040213009 SPM Neighborhood Population O3

Combs School TEOM 040213009 SPM Neighborhood Population PM10

Cowtown Road TEOM 040213013 SPM Microscale SourceImpact PM10

Cowtown Road 040213013 SPM Microscale SourceImpact PM10

Cowtown Road 040213013 SPM Microscale SourceImpact PM2.5 

County Complex Maricopa 040213010 SPM Neighborhood Population O3

County Complex Maricopa 

TEOM 

040213010 SPM Neighborhood Population PM10

Pinal Air Park 040213007 SPM Regional Transport O3

Pinal County Housing 

Complex TEOM 

040213011 SPM Neighborhood Population PM10

Stanfield TEOM 040213008 SPM Neighborhood Population PM10

Pinal County Air Quality proposes to retain the SPM designation for the monitors listed 

in Table 3.2. The ozone analyzers at Combs School, County Complex Maricopa, and 

Pinal Air Park will operate from April 1 through October 31, the seasonal schedule. The 

PM10 TEOM analyzers at Maricopa, Stanfield, Combs School, Casa Grande Downtown, 

and Pinal County Housing will also retain SPM designation. The Cowtown medium 
22

volume FRM (47mm) and TEOM samplers are operated to monitor specific sources near 

the site. 

3.2 AQS Requirements 

In 2002 Pinal County Air Quality began entering local monitoring data into the EPA’s 

AQS database. 40 CFR 58.16 requires that all ambient air quality data and associated 

quality assurance checks for all criteria pollutants be submitted to EPA via AQS. 

Additionally, an annual data certification is required by 40 CFR 58.15. The certification 

must be sent to EPA Region IX by July 1 stating that the data has been submitted 

correctly. Pinal County Air Quality will submit an annual data certification for 2008 by 

July 1, 2009. Precision data for 2008 were submitted to AQS as of March 2009. 

3.3 Minimum Network Requirements 

40 CFR Part 58 Appendix D defines minimum monitoring requirements based on the 

population of the Metropolitan Statistical Area (MSA) and the design value for each 

NAAQS. Pinal County is part of the Phoenix-Mesa-Scottsdale MSA, which has a 

population of 4,039,182 (US Census Bureau, Annual Estimates of the Population of 

Metropolitan and Micropolitan Statistical Areas: April 1, 2000 to July 1, 2006 CBSAEST2006-01). The design value is a calculated value based upon the highest recorded 

concentration at a site in the attainment or nonattainment area. The process for computing 

the value for each criteria pollutant is described in the appendices of 40 CFR Part 50. For 

the purpose of this document the design values listed are the highest calculated 

concentrations recorded in Pinal County. Tables 3.3 through 3.5 list the minimum 

monitor requirements for PM2.5, PM10, and Ozone, respectively. 

Table 3.3 PM2.5 Monitoring Requirements (SLAMS) 

Population (MSA) Most recent 3 yr design value 

≥ 85% NAAQS 

Most recent 3 yr design value 

<85% NAAQS 

>1M 3 2 

500K-1M 2 1 

50K-500K 1 0 

Table 3.4 PM10 Monitoring Requirements (SLAMS) 

Population 

(MSA) 

High Concentration 

Exceeds NAAQS by 20% or 

more (>180μg/m3) 

Medium Concentration 

Exceeds 80% of NAAQS 

(>120μg/m3) 

Low Concentration 

Less than 80% 

NAAQS (<120 μg/m3) 

>1M 6-10 4-8 2-4 

500K-1M 4-8 2-4 1-2 

250K-500K 3-4 1-2 0-1 

100K-250K 1-2 0-1 0 
23

Table 3.5 Ozone Monitoring Requirements (SLAMS) 

Population 

(MSA) 

Most recent 3 yr design value 

≥ 85% NAAQS 

Most recent 3 yr design value 

<85% NAAQS 

>10M 4 2 

4-10M 3 1 

350K-4M 2 1 

50K-350K 1 0 

Tables 3.6, 3.7 and 3.8 depict Pinal County’s minimum monitoring requirements for 

PM10, PM2.5 and ozone. The tables below show the minimum monitoring requirements 

are being met. 

These tables only include SLAMS monitors operated in Pinal County, and do not include 

monitors operated in other areas of the MSA. 40 CFR 58.20 states that SPM monitors 

may not be used to show compliance with the minimum monitoring requirements. 

Table 3.6 lists the minimum monitoring requirements for ozone. The highest 8-hour 

ozone concentration site in Pinal County is the Apache Junction ozone site. The 

calculated ozone design value using the Apache Junction 3-year average of the 4th highest 

8-hour average is 0.080 ppm. This value is ≥ 85% of the NAAQS, which requires a 

minimum of three ozone monitors in the MSA. 

Table 3.6: Minimum Monitoring Requirements for Ozone (O3) 

MSA Population 

(US Census 

2006) 

8-hour Design 

Value 

(2006-2008) 

Minimum 

Monitors 

Required 

# of Active 

SLAMS 

Monitors 

Monitors 

Needed 

Phoenix-MesaScottsdale 4,039,182 0.080 3 3 0 

Table 3.7 lists the minimum monitoring requirements for PM10. The highest PM10 

concentration recorded at a SLAMS site over the last years of operation (2006-2008) was 

at 374 μg/m3

 at Stanfield. The value exceeds the NAAQS by 20% or more and is 

considered a high concentration area. The high concentration designation requires six to 

ten monitors in the MSA. 

Table 3.7: Minimum Monitoring Requirements for PM10

MSA Population 

(US Census 

2006) 

Design Value 

(2005-2007) 

Minimum 

Monitors 

Required 

# of 

SLAMS 

Active 

Monitors 

Monitors 

Needed 

Phoenix-MesaScottsdale 4,039,182 374 6 to 10 9 0 

 

Table 3.8 illustrates the minimum monitoring requirements for PM2.5. The highest PM2.5 

3-year average recorded at a Pinal County SLAMS site was at Casa Grande Downtown. 

The calculated PM2.5 design value for the Casa Grande 3-year average of the annual 

means is 9.5 μg/m3

 and the 3-year average of the 98th percentiles is 19.9 μg/m3. Both 

values are < 85% of the NAAQS, which requires two monitors in the MSA. 
24

Table 3.8: Minimum Monitoring Requirements for PM2.5

MSA Population 

(US Census 

2006) 

Design Value 

(2005-2007) 

Minimum 

Monitors 

Required 

# of Active 

SLAMS 

Monitors 

Monitors 

Needed 

Phoenix-MesaScottsdale 4,039,182 9.5 (annual) 

19.9 (24-hour) 

2 2 0 

3.4 Minimum Sample Frequency 

PM2.5 - The monitoring rule at 40CFR 58.12 (d)(1) states that required manual PM2.5 

samplers at SLAMS stations must operate on at least a 1-in-3 day schedule at sites 

without a collocated continuously operating PM2.5 monitor. For SLAMS PM2.5 sites with 

both manual and continuous PM2.5 monitors operating, the monitoring agency may 

request approval from the EPA Regional Administrator for a reduction to 1-in-6 day 

PM2.5 sampling at SLAMS stations or for seasonal sampling. The EPA Regional 

Administrator may grant sampling frequency reductions after consideration of factors 

including, but not limited to, the historical PM2.5 data quality assessments, the location of 

current PM2.5 design value sites, and their regulatory data needs. Sites that have design 

values that are within plus or minus 10 percent of the NAAQS (±10% of 35μg/m3

 is 31.5-

38.5) and sites where the 24-hour values exceed the NAAQS for a period of 3 years are 

required to maintain at least a 1-in-3 day sampling frequency. Sites that have a design 

value within plus or minus 5 percent of the daily PM2.5 NAAQS (±5% of 35μg/m3 is 

33.25-36.75) must have an FRM or FEM operating on a daily schedule. 

In 2008 Pinal County proposed and received approval from EPA Region IX to reduce the 

sample frequency at the Casa Grande site from 1 in 3 to 1 in 6 after the end of the 2008 

sample year. This change was implemented on January 1, 2009. During 2007 samples 

were collected on the 1 in 3 schedule. Prior to 2007 the site operated at a 1 in 6 frequency 

for 8 years. During the time this site has operated the 3 year average of the 98th percentile 

value has not exceeded 21μg/m3. With this change in sample frequency equipment was 

made available to begin collecting a precision PM2.5 measurements at the site. Sample 

frequencies are summarized in Table 3.9. 

The sample frequency at Apache Junction will not change. 

Table 3.9 PM2.5 Sampling Frequencies 

Site Name 3-Year Average of 98th

percentile 2006-2008 

Current Sample 

Frequency 

Required 

Frequency 

Casa Grande 19.9 1 in 61 1 in 3 

Apache Junction 13.1 1 in 3 1 in 3 

1. See description in this regarding precision samples and sample frequency 

PM10 - The monitoring rule at 40 CFR 58.12 (e) states that for PM10 sites, the minimum 

monitoring schedule for the site in the area of expected maximum concentration shall be 

based on the relative level of that monitoring site concentration with respect to the 24-

hour standard. Pinal County currently operates a continuous monitor at its maximum 

PM10 concentration site. Therefore, no change to the PM10 sample frequency is required.
25

3.5 Measurement Quality Checks 

To provide a quality assurance demonstration, Appendix A of 40 CFR Part 58 requires a 

minimum number of collocated sampling sites based on the total number of manual 

(filter-based) particulate monitoring sites in the network. Generally, precision sampling 

involves operating two identical collocated samplers at the same location on the same 

sampling schedule. 

Appendix A of 40 CFR Part 58 Section 3.3.1 requires fifteen percent of the filter based 

PM10 monitoring sites, by collection method, in a network to be collocated. Pinal County 

Air Quality currently operates a total of ten PM10 sites. Seven sites utilize high-volume 

samplers and 2 sites utilize medium-volume samplers (47mm). Table 3.10 summarizes 

the status of collocated sites in the PM10 network. 

The Pinal County Housing site is utilized to collect the required PM10 collocated HighVolume samples. Pinal County Air Quality does not currently operate a precision site for 

comparing medium –volume filter based PM10 monitors (47mm) and, therefore, does not 

meet the required minimum number of collocated sites. The addition of 1 collocated site 

is required. This topic is addressed in Section 5.0, Proposed Changes to the Network. 

Table 3.10: Minimum Collocated Monitoring Requirements for PM10

Sampling Method Total Number 

of Sites

Required 

Collocated Sites Number of Collocated Sites

High-Volume (Wedding or Anderson) 8 1 1 (Pinal County Housing) 

Medium-Volume (Partisol or RAAS) 2 1 0 

Appendix A of 40 CFR Part 58 does not require collocation of continuous PM10

monitors. Measurement quality of continuous TEOM instrument is achieved through 

flow verification checks conducted at least once per month. 

Appendix A of 40 CFR Part 58 Section 3.2.5 requires PM2.5 networks to include 

collocated sampling at fifteen percent of the monitoring sites in a network. Pinal County 

Air Quality operates three PM2.5 sites with one collocated measurement made at Casa 

Grande Downtown. As described above, this was a change made in 2009 to correct a 

deficiency note in the 2007 plan. 

3.6 Ozone Season Definition 

In the 2007-2008 Annual Ambient Monitoring Network Plan Pinal County requested and 

was granted a modification to the area ozone season in accordance with 40 CFR Part 58, 

Appendix D, Paragraph 4.1(i). The modification to the ozone season defined the season 

as April 1 through October 31. 

Pinal County continues to believe the appropriate ozone season for sites under our 

operation to be April 1 through October 31 each year. This is based upon the updated 

data summary below from the Casa Grande and Apache Junction ozone sites for years 

2002 through 2008, which with the exception of 2 days; March 15, 2007 at Apache 

Junction, March 31, 2008 at Apache Junction and Casa Grande, demonstrates that ozone 
26

concentrations have not historically exceeded 75 ppb during the period from October 

through March. See Figure 3.1 below. Additionally, a 1998 EPA guidance document 

entitled, “Guideline for Selecting and Modifying the Ozone Monitoring Season Based on 

an 8-Hour Ozone Standard” supports a shorter ozone season for Arizona based upon data 

collected from 1990 through 1995. 

The modified seasonal schedule is applied to the following sites: Combs School, Pinal 

Air Park, and Maricopa County Complex. The Casa Grande Airport and Apache Junction 

Maintenance Yard would continue to operate on a January to December schedule. With 

the past approval of this modification, Pinal County made appropriate corrections to the 

seasonal definition in the AQS database and annual monitoring plan. 

Number of Days With Ozone Concentration 75ppb or Greater

2002-2008 8-Hour Average

0

5

10

15

20

25

JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC

Days

Casa Grande Apache Junction

Figure 3.1 
27

3.7 Quality System Requirements 

Pinal County Air Quality submitted a Quality Assurance Project Plan (QAPP) to EPA 

Region IX in January 2007. The QAPP covered all aspects of the ambient monitoring 

network operations, filter weighing process, and data quality review. All instrument SOPs 

were completed and included in the QAPP. EPA provided feedback on the QAPP in July 

of 2008. Pinal County Air quality is currently revising appropriate sections of the QAPP 

to address the comments. 

All flow rate standards used by Pinal County are traceable to NIST Standards and are 

recertified annually. The ozone standard is verified by the California Resource Board on 

an annual basis and the ozone transfer standard is verified by Pinal Staff monthly. 

Through ADEQ, Pinal County is a participant in the EPA National Performance audit 

program (NPAP) and the PM Performance Evaluation Program (PEP). Pinal County 

sites are included in the EPA sponsored audit programs. 

ADEQ conducts performance audits of Pinal County monitors according to frequencies 

described in 40 CFR Part 58. All flow rate standards used by ADEQ are traceable to 

NIST Standards and a recertified annually. The ozone standard used by ADEQ is 

checked twice per year. 

Currently, EPA does not consider Pinal County Air Quality a primary quality assurance 

organization as defined by 40 CFR Part 58 Appendix A, paragraph 3.1.1. During 2009 

Pinal County will work with EPA Region IX gain this designation. 

3.8 Lead Monitoring Network Description 

The strengthening of the Lead NAAQS resulted in a revision to 40CFR Part 58.10. The 

revision requires state and local agencies to describe required lead monitoring networks 

in the annual monitoring network plan and submit the description to the Regional 

Administrator by July 1, 2009. 

Appendix D to Part 58 entitled, “Network Design Criteria for Ambient Air Quality 

Monitoring”, requires states and local agencies to establish ambient lead monitoring 

under two specific conditions: 

1) Source-oriented SLAMS level monitoring located to measure the maximum 

lead concentration in ambient air resulting from each lead source which emits 1.0 

or more tons per year based on either the most recent National Emission 

Inventory (NEI) (http://www.epa.gov/ttn/chief/ eiinformation.html) or other 

scientifically justifiable methods and data (such as improved emissions factors or 

site-specific data), and 

2) Lead monitoring in each CBSA with a population equal to or greater than 

500,000 people as determined by the latest available census figures. At a 

minimum, there must be one non-source-oriented SLAMS site located to measure 

neighborhood scale lead concentrations in urban areas impacted by re-entrained 

dust from roadways, closed industrial sources which previously were significant 
28

sources of lead, hazardous waste sites, construction and demolition projects, or 

other fugitive dust sources of lead. 

To assess a potential point-source triggered requirement for ambient lead monitoring in 

Pinal County the 2005 NEI and internal emission inventory reports were reviewed by 

Pinal County Air Quality Staff. Table 3.11 summarizes lead emission calculated by NEI 

or reported through the Toxics Release Inventory (TRI) in 2005. As reported to NIE in 

2005 only one source in Pinal County exceeded the 1 ton per year threshold. A review of 

the ASARCO LLC Ray Operations Mine 2007 emission inventory report, which is 

required through air quality operating permit, shows a revision to the annual lead 

emission rate from 1.27tpy to 0.014tpy. The revision was described in a May 12, 2008 

letter accompanying the annual emission inventory submittal. Air Quality permit 

management reviewed and accepted the revised emission rate. 

The second pathway for required ambient lead monitoring arises through CMSA/MSA 

population. Pinal County is included in the Phoenix-Mesa-Scottsdale, AZ MSA with a 

2006 population of approximately 4.1 million people. This is above the 500,000 person 

population threshold described above. Although Pinal County is included in the MSA the 

majority of the population resides in Maricopa County. 

After review of the inventory and MSA population, Pinal County Air Quality has 

concluded that monitoring for ambient lead in the county will not be conducted. This 

conclusion is based upon the following; 1) no point source in the county emits lead above 

the 1 ton per year threshold or the possible revised threshold of 0.5 ton per year and, 2) 

Pinal County assumes that the MSA required monitoring will be conducted in Maricopa 

County. Pinal County Air Quality will revisit the need and feasibility of lead monitoring 

as source emissions and economic conditions change. 

Table 3.11: NEI 2005 Point Source Lead Emissions in Pinal County 

Facility Name 2005 NEI v 2 Emissions (tpy) TRI2005 TRI Emissions (tpy)

FABRICATED PRODUCTS INC. 

DBA S EAFAB METALS CO. 0.00555 0.00555 

ASARCO LLC RAY OPERATIONS 

MINE 0.00025 1.27275 

OWENS CORNING ELOY PLANT 0.0411 0.0542 

WESTILE INC. 0.00005 0.00005 
29

4.0 Monitoring Site Descriptions 

This section describes the purpose and classification of each monitoring site operated by 

Pinal County Air Quality. Appendix B contains images and summary tables for each site. 

The changes that have occurred or are planned at each site are detailed within each 

subsection. Each site has been evaluated for compliance with the siting criteria listed in 

40 CFR Part 58 Appendix D (Network Design) and Appendix E (Probe and Path Siting). 

4.1 Apache Junction Fire Station 

This site is located behind Apache Junction Fire Station #2 on Bureau of Land 

Management (BLM) property. Apache Junction lies at the fringe of the Phoenix 

metropolitan area, where urban development meets the Tonto National Forest and 

Superstition Wilderness. The site sits on the eastern boundary of the City of Apache 

Junction with residential homes to the east. Undisturbed desert immediately surrounds the 

site to the north, south and west with residential homes beyond that. The Superstition 

Mountain Range is located approximately one mile east of the site. The purpose of the 

site is to quantify PM2.5 and PM10 concentrations affecting the surrounding population on 

a neighborhood scale. This site is included in the statewide PM2.5 network. 

The site consists of a High-Volume PM10 sampler and a FRM sequential PM2.5 sampler. 

The PM10 sampler operates on a one in six day schedule and the PM2.5 sampler operates 

on a one in three day schedule. 

The site historically consisted of two Andersen FRM PM2.5 monitors, one of which 

operated every third day. The samplers did not take precision samples; instead their 

operation alternated. One sampler was operated on each run day so that the number of 

site visits was reduced. In June 2004 a sequential R&P FRM PM2.5 sampler was installed 

in replace of the Andersen PM2.5 monitors. 

One High-Volume PM10 sampler from the Apache Junction Maintenance Yard (described 

in section 3.2) was moved to this site on July 1, 2003. Samples were collected at both 

sites until January 1, 2004 to develop a correlation between the two sites. The correlation 

is discussed further in section 5.3.1. As of January 1, 2004 the Apache Junction Fire 

Station site is the only PM10 site in Apache Junction. 

The site meets 40 CFR Part 58 Appendix D and E criteria. 

4.2 Apache Junction Maintenance Yard 

This site is located within the Pinal County Public Works Yard and is in the center of 

Apache Junction. Three major roads surround the site: State Highway 88, Idaho Road, 

and Superstition Boulevard. The maintenance yard area is graveled, well maintained, and 

historically activity in the yard has not adversely affected the samplers. The historical 

purpose of this site was to quantify PM10 concentrations affecting the surrounding 

population on a neighborhood scale, quantify carbon monoxide concentrations near a 

major intersection on a middle scale, and quantify ozone concentrations on the eastern 
30

boundary of the Phoenix metropolitan area. The ozone concentration at this site reflects 

both regional transport and neighborhood scale population exposure. 

Historically, the site consisted of two Wedding High-Volume PM10 monitors that 

collected precision samples on a one in six-day schedule, an ozone monitor, a carbon 

monoxide monitor, a wind system, a barometric pressure sensor and a temperature and 

relative humidity sensor. The inlet funnel on the ozone monitor was changed from 

stainless steel to Pyrex glass in 2001. The site has met 40 CFR Part 58 Appendix D and E 

criteria since then. 

In an effort to better utilize the resources available to Pinal County Air Quality, the 

District removed the carbon monoxide monitor located at this site on May 28th, 2002. The 

reasoning behind this is discussed in detail in section 5.1 of this document. 

One of the PM10 High-Volume monitors located at this site was moved to the Apache 

Junction Fire Station site on July 1, 2003. PM10 monitoring took place at both sites until 

January 1, 2004, so that a correlation between the two sites could be developed. On 

January 1, 2004 the remaining PM10 High Volume monitor was moved to the Pinal 

County Housing site in order to create a co-located PM10 site. Refer to section 4.12 of this 

document for details on the Pinal County Housing site. 

The existing tower at the Apache Junction Maintenance Yard site, on which the wind 

system is mounted, historically was not stable enough to produce accurate wind direction. 

The mounting of the meteorological equipment was reconfigured in May 2007 so that 

accurate measurements could be taken. 

4.3 Casa Grande Airport 

This site is located within the Casa Grande Municipal Airport. Casa Grande lies about 

twenty miles south of the Phoenix urban area, in a broad desert plain largely dominated 

by open field agriculture. A small industrial park is located within the airport complex 

and there are residential subdivisions to the north, south, and east of the airport. The 

airport is on the north edge of Casa Grande, although the entire surrounding area is 

growing rapidly. To the east of the airport approximately a quarter of a mile is a major 

thoroughfare, Pinal Avenue. 

The objective of this site is to quantify ozone concentrations south of the Phoenix 

metropolitan area. The ozone concentration at this site reflects both regional transport and 

neighborhood scale population exposure. 

In the past carbon monoxide was also monitored at this site. In an effort to better utilize 

the resources available to Pinal County Air Quality, the District removed the carbon 

monoxide monitor located at this site on October 11, 2002. 

The site currently consists of an ozone analyzer, a wind system, a barometric pressure 

sensor and a temperature and relative humidity sensor. In August 2006 a new site shelter 

was installed. The site meets 40 CFR Part 58 Appendix D and E criteria. 
31

4.4 Casa Grande Downtown 

This site is located on the roof of an Arizona Department of Economic Security building 

in the downtown area of Casa Grande. A core business district surrounds the site 

followed by residential areas in all directions. The purpose of the site is to quantify PM2.5

and PM10 concentrations affecting the surrounding population on a neighborhood scale. 

Historically, the site consisted of a High-Volume PM10 sampler and a PM2.5 FRM 

sampler. The samplers were moved further away from a nearby furnace flue in 

September of 2001. The High-Volume PM10 sampler operates on a one in six-day 

schedule. The PM2.5 monitor at this site was upgraded from an Andersen PM2.5 FRM 

sampler to a single channel R&P PM2.5 FRM sampler in March 2004. The PM2.5 FRM 

sampler had operated on a one in six day schedule since 1999. On January 1, 2007 the 

sample frequency was changed to one in three days to meet new monitoring 

requirements. In March of 2007 a second PM2.5 FRM sampler was installed so that 

operation could alternate between the two and reduce trips to the site. A continuous PM10

TEOM was installed in March of 2007. 

For the first sample of 2009, the sample frequency of the two PM2.5 samplers was change 

from a frequency of 1 in 3 to 1 in 6 to allow for precision measurement. This change was 

proposed in the 2007 network plan. 

On December 31, 2008 the HiVolume sampler was moved from Casa Grande Downtown 

to Stanfield and replaced with a PM10 Thermo Partisol. 

The site meets 40 CFR Part 58 Appendix D and E criteria.

4.5 Combs School 

This site is located within the J.O. Combs Elementary School District campus and is 

approximately ten miles south of Apache Junction in an area that is rapidly being 

developed for residential use. The area has historically been dominated by open field 

agriculture, although residential developments have been built or are being planned to the 

north, south, east and west of the site. This site is used to quantify ozone and PM10

concentrations southeast of the Phoenix metropolitan area. The ozone concentration at 

this site reflects regional transport and neighborhood population exposure. The PM10

concentration at this site reflects neighborhood scale population exposure. 

This site was installed in June of 2002 and ozone data recording began in July 2002, thus 

data for a portion of the 2002 ozone season are missing. In March of 2007 a continuous 

PM10 TEOM was added at the site. 

The site meets 40 CFR Part 58 Appendix D and E criteria. 

4.6 Coolidge Maintenance Yard 

This site is located within the Pinal County Public Works Yard on the east side of 

Coolidge. Coolidge lies about thirty miles southeast of the Phoenix urban area in a desert 

basin largely dominated by open field agriculture. Residential homes surround the site to 

the north, south, and east. West of the site is a railroad track with a business district on 
32

the other side. The purpose of this site is to quantify PM10 concentrations affecting the 

surrounding population on a neighborhood scale. 

The site consists of a High-Volume PM10 sampler, which collects samples on a one in 

six-day schedule. Due to a scheduled demolition, the monitor was moved from the roof of 

a cargo trailer to a ground level stand in June of 2002. The monitor was moved 

approximately fifteen meters to the south and the inlet height was reduced from 5.6 

meters to 3.4 meters. 

The site meets 40 CFR Part 58 Appendix D and E criteria. 

4.7 Cowtown Road 

This site is located approximately four miles southeast of the City of Maricopa. The site 

also lies within an irrigated agricultural plain, with active and retired agricultural 

operations to the north, northwest and east. Feedlots, a grain processing complex, and a 

commercial composting facility operate to the south, southwest and southeast. This site 

is used to look at several PM10 sources in the area, including agriculture, the grainprocessing complex, the feedlots and county dirt roads. 

The site was installed and data recording began in November of 2001. Since neither a 

quarterly nor annual average can be obtained from the two months of 2001 data this 

document will contain 2002 and subsequent data from this site. The site first consisted of 

a TEOM that collected continuous PM10 data, a wind system, and a temperature and 

relative humidity sensor. The area immediately surrounding the site was fenced off (at 

least 100 feet in all directions) in September of 2003 in order to stabilize the surrounding 

soil. The surrounding soil has subsequently been stabilized relatively well with the 

exception of the area to the south of the samplers. This area is a right of way that runs 

along the Casa Grande – Maricopa Highway and it was regularly disturbed by farm 

machinery (for instance a tractor and disc) in order to control weeds. In December of 

2006 the right of way area adjacent to the site was fenced off to prevent this activity. 

Since December 2006 this site meets 40 CFR Part 58 Appendix D and E criteria. 

A new shelter was installed at this site in August 2003 to accommodate additional 

equipment. A time-lapse video system was installed at this time and was operated until 

July 2006. The TEOM at this site was upgraded to a new unit in June 2004. The new unit 

still sampled PM10 and had the filter dynamics measurement system (FDMS) installed as 

an option. This option is designed to better account for particles that are in a gaseous 

form. The FDMS unit had difficultly operating in the harsh environment at this site from 

the beginning. Due to the maintenance problems with the FDMS unit, a TEOM unit 

without the FDMS option was set up as the primary monitor in January 2005. 

The FDMS TEOM was operated periodically during 2005 in an effort to find ways to 

maintain the sampler in this harsh environment. During May and June of 2005 the FDMS 

TEOM was operated along with the collocated regular TEOM unit, both collecting PM10. 

During this time it was found that the regular TEOM unit was reading approximately 

30% higher than the FDMS TEOM unit. District staff worked with representatives from 

the manufacturer of the units, R&P, to determine the cause of this discrepancy. 
33

Two issues were identified with the regular TEOM unit. First, it was found that the fiveminute averages of this unit often recorded a large negative number directly after an 

extremely large positive number (1000 μg/m3 or more). The manufacturer of the unit 

concluded that the flow controllers were over correcting for the extremely large 

particulate matter concentrations and correspondingly creating the negative numbers. The 

second issue identified was that the unit often recorded elevated noise vibrations when 

extremely large concentrations were recorded. This was a result of a large amount of 

particulate matter being deposited on the oscillating microbalance in a short amount of 

time. In order to correct both of these discrepancies the main inlet flow on the regular 

TEOM unit was reduced to 1 liter per minute (from 3 liters per minute) in August 2005. 

The manufacturer has used this alternate setting in other areas with extremely high 

particulate matter concentrations. The main flow setting of 1 liter per minute still retains 

the FEM status of the unit. 

A filter based Andersen FRM PM10 unit and a filter based Andersen FRM PM2.5 unit 

were installed at this site in August of 2005. The units are both operated on a one in six 

day schedule. This allows PM10, PM2.5 and surrogate coarse data to be collected. Coarse 

material refers to particulate matter that is between 2.5 microns and 10 microns in size. 

The surrogate coarse data is extrapolated by subtracting the PM10 concentration from the 

PM2.5 concentration. 

Comparing the regular PM10 TEOM data (with the main flow set at 1 liter per minute) to 

the FRM filter based PM10 data yields an excellent correlation. The average percent 

difference between the two is 6.4% for the time period of August 2005 to June 2006. This 

demonstrates that setting the main flow to 1 liter per minute on a regular PM10 TEOM is 

an appropriate operating method in this harsh environment. 

Subsequent attempts during 2005 to build a suitable correlation between the regular PM10

TEOM and the FDMS PM10 TEOM unit were not successful. The FDMS PM10 TEOM 

continued to read approximately 15% below the regular PM10 TEOM. This does not 

appear to be a logical relationship since the FDMS unit is designed to better account for 

particles that are in a gaseous form and thus should be slightly higher than the regular 

PM10 TEOM. Further conversations with the manufacturer of the unit suggest the dryer 

that is built into the FDMS unit is scavenging coarse material. At this time Pinal County 

Air Quality has concluded that the FDMS TEOM unit is not suitable for measuring PM10

in this harsh environment that has a large coarse fraction. (The manufacturer may have a 

second-generation drier available in the future that would prevent the scavenging of 

coarse material in situations like this.) 

Due to the difficulty and expense of operating the FDMS TEOM in this environment, the 

instrument was shut down in May of 2007. 

The time-lapse video system was relocated to the Stanfield site in July of 2006. The 

Cowtown site was several hundred yards from the feedlots being observed and did not 

allow the camera to record an overall view of the dust events. 

On January 15, 2009 the PM10 and PM2.5 Anderson samplers were replaced with Thermo 

PM10 and PM2.5 Partisol samplers. 
34

4.8 Eloy County Complex 

This site is located on the roof of the Pinal County Justice Court building. Eloy also lies 

in the agricultural basin of the County. A small business district to the north and south 

and residential homes to the east and west surround the site. The purpose of this site is to 

quantify PM10 concentrations affecting the surrounding population on a neighborhood 

scale. 

This site replaced the Eloy City Complex site, which was approximately 300 yards to the 

south, in March 2007. The site consists of a High-Volume PM10 sampler, which collects 

samples on a one in six-day schedule. 

The site meets 40 CFR Part 58 Appendix D and E criteria. 

4.9 Mammoth County Complex 

This site is located on the roof of the Mammoth County Complex. Mammoth lies near the 

southeast corner of the County, approximately thirty miles northeast of Tucson and 

eighty-five miles southeast of Phoenix. Residential homes surround the site on all sides. 

The purpose of this site is to quantify PM10 concentrations affecting the surrounding 

population on a neighborhood scale. This site also serves as a background site for the 

eastern portion of the county, which historically has been economically dominated by 

copper mining. The surrounding elevations range from 2000 to 5500 feet. Aside from the 

mining operations, the landscape is dominated by native vegetation. 

The site consists of a High-Volume PM10 sampler, which collects samples on a one in 

six-day schedule. 

The site meets 40 CFR Part 58 Appendix D and E criteria. 

4.10 Maricopa County Complex (City of Maricopa) 

This site is located behind the County Complex in city of Maricopa. Maricopa lies about 

fifteen miles south of the Phoenix urban area. Historically the area was a small residential 

area surrounded by pecan orchards, cattle feedlots, and open-field agriculture. Recently, 

development has added a substantial number of houses near the monitoring site and 

additional subdivisions are planned in every direction. This site is used to quantify ozone 

concentrations and PM10 concentrations in the area. The ozone concentration at this site 

reflects both regional transport and neighborhood scale population exposure. The PM10

concentration at this site reflects neighborhood scale population exposure. 

 

This site was installed in June of 2002 and an ozone sampling began in July 2002, thus 

data for a portion of the 2002 ozone season are missing. The ozone monitor is operated 

seasonally. In December 2004 a PM10 TEOM unit was installed. Therefore, only data 

beginning January 2005 are included in the document. 

The site meets 40 CFR Part 58 Appendix D and E criteria. 
35

4.11 Pinal Air Park 

This site is located at water well number two within the Pinal Air Park complex. Pinal 

Air Park lies about twenty miles northwest of Tucson, at the Pinal/Pima County line. The 

site is immediately surrounded by undisturbed desert on all sides with an industrial park 

and airport lying to the west. The purpose of this site is to quantify background PM10

concentrations and transport ozone concentrations on a regional scale. This site serves as 

a background particulate matter site for the central and western portion of the county, 

which is dominated by agriculture and low elevations (generally around 1500 feet). 

The site includes a High-Volume PM10 sampler, which collects samples on a one in sixday schedule and an ozone monitor that is operated seasonally. An ozone analyzer was 

installed in June of 2002 to assess regional transport from the Tucson metropolitan area. 

Data collection from this ozone monitor did not begin until July of 2002, thus the data set 

for 2002 only includes a portion of the ozone season. The ozone concentration at this site 

reflects both regional transport and neighborhood scale population exposure. 

The site meets 40 CFR Part 58 Appendix D and E criteria. 

4.12 Pinal County Housing Complex 

This site is located within the Pinal County Housing Complex and is approximately 

eleven miles east of Casa Grande in the heart of the agricultural basin of the County. The 

site was installed in July of 2002 to replace the Eleven Mile Corner site, which was 

approximately 1 mile to the south. The Pinal County Housing site better represents the 

particulate matter impact on the surrounding population since the site is adjacent to a 

subdivision. The site is located within a fenced area that houses the sewer lift station for 

the subdivision. The enclosure is immediately surrounded by native desert growth with 

active and retired agricultural areas beyond that in all directions. The County Housing 

subdivision lies just to the southeast of the enclosure. A small dairy, two cotton gins, and 

the Pinal County Fairgrounds are approximately one mile to the south of the Pinal County 

Housing Complex site. This site is used to evaluate several PM10 sources in the area, 

including cotton gins, fairground activity, and agricultural activity. 

The site originally consisted of a High-Volume PM10 sampler running on a one in six day 

schedule, a continuous PM10 TEOM, a wind system, and a relative humidity and 

temperature sensor. On January 1, 2004 a second High-Volume PM10 sampler was 

installed to collect precision samples. This replaced the Apache Junction Maintenance 

Yard as the precision site in the network. 

During 2005 it was discovered that one of the High-Volume PM10 samplers, PCH West, 

was not operating properly; the second High-Volume sampler, PCH East, has operated 

within specifications throughout this time period. The malfunctioning Anderson HighVolume PM10 sampler was removed from service in July 2006. This particular unit had a 

quick connect device to secure the inlet that none of the other Andersen High-Volume 

units operated by the District have. It appears this quick connect device has deteriorated 

over time and was causing the unit to operate outside of the required specifications. Since 

one of the Anderson High-Volume units was retired, two Wedding High-Volume units 

were installed at this site in July 2006 to collect precision samples. 
36

In 2008 the site will be moved approximately 20 yards to the south. A new shelter and 

10 meter wind tower will be added (see section 4.2 for additional detail). 

The site meets 40 CFR Part 58 Appendix D and E criteria. 

4.13 Riverside Maintenance Yard 

This site is located at the Pinal County Public Works Yard in Riverside. The site is 

approximately thirteen miles southeast of Superior and four miles northwest of Kearny. 

The Ray Mine, an active open pit copper mine, is approximately two miles east of the 

monitoring site. The monitor is located in the Mineral Creek valley, down slope from the 

mine operations. The purpose of this site is to analyze off-site source impacts of the 

mine’s tailing impoundments (neighborhood scale). 

This site was installed in March of 2003 and consists of an Andersen High-Volume PM10

sampler collecting samples on a one in six-day schedule. In early 2006, Pinal County 

Public Works Department moved a mobile office building onto the site. The addition of 

this building did not affect the siting of the sampler. 

The site meets 40 CFR Part 58 Appendix D and E criteria. 

4.14 Stanfield County Complex 

This site is located behind the Stanfield County Complex. Stanfield lies about fifteen 

miles west of Casa Grande, and about thirty miles south of the Phoenix urban area. 

Residential homes surround the site on all sides, but the surrounding landscape is 

dominated by open-field agriculture. Sizeable feedlot and dairy operations lie about three 

miles to the north, east and west. The purpose of this site is to quantify PM10

concentrations affecting the surrounding population on a neighborhood scale. Over the 

last several years this site may have been impacted by increased activity at existing cattle 

feedlots and new dairies located east, west and north of the site. 

Historically, the site consisted of a High-Volume PM10 sampler, which collected samples 

on a one in six-day schedule. In February 2006 a PM10 TEOM was installed at this site to 

collect continuous data. In April 2006 the Wedding High-Volume sampler was replaced 

with a medium volume Anderson FRM sampler. The Anderson sampler was replaced 

with an FRM Partisol medium volume sampler in November 2007. 

A time-lapse video system which was previously installed at the Cowtown site (described 

in section 3.9) was added to this site in July 2006. The new location will allow the 

camera to record an overall view of the dust events observed at the feedlots that are 

approximately three miles west of the site. 

On December 31, 2008 the PM10 Partisol sampler at Stanfield was replaced with the 

High-Volume sampler from Casa Grande Downtown. Pinal County Air Quality is 

proposing to discontinue filter based PM10 sampling at this site and designate the PM10

TEOM located here as a SLAMS (see section 5.3 for additional detail). 

The site meets 40 CFR Part 58 Appendix D and E criteria. 
37

4.15 Queen Valley 

This site is located at the Queen Valley water tank. Queen Valley is approximately 

sixteen miles southeast of Apache Junction and just south of the Superstition Wilderness 

Class I area. The site is on the south edge of Queen Valley and is surrounded by rugged 

terrain and native vegetation. The equipment at the site is owned and operated by ADEQ. 

This is an ADEQ SLAMS site which is part of the Photochemical Assessment 

Monitoring Station (PAMS) network that provides data regarding ozone transport from 

the Phoenix urban area. ADEQ operates instruments at this site to measure ozone, 

reactive nitrogen oxides (NOy), and PAMS volatile organic compounds. ADEQ also 

operates a nephelometer, temperature and relative humidity sensors at the site. The ozone 

data from this site is included in Appendix B of this document because the site 

demonstrates ozone transport into Pinal County. Please refer to the State of Arizona 

Monitoring Network Plan for additional information. 

Pinal County Air Quality serves as the operator for the Interagency Monitoring of 

Protected Visual Environments (IMPROVE) sampler located at this site. This sampler 

provides particulate matter data and speciation data for assessing the impact of 

particulates on visibility at the nearby Superstition Wilderness Class I area. Please refer 

to the IMPROVE web site at http://improve.cnl.ucdavis.edu/ for the data from this 

monitor. 
38
39

5.0 Proposed Changes to the Network 

This section describes any new sites that Pinal County Air Quality plans to install and 

summarizes recent changes to the network. 

5.1 Stanfield 

At the conclusion of the 2009 monitoring year the Hi Volume filter-based PM10 sampler 

will be discontinued at the Stanfield site. The filter-based measurement is currently 

categorized as SLAMS and collects samples on a 1 in 6 schedule. Upon the removal of 

the Hi Volume sampler the continuous PM10 TEOM SPM will be designated the SLAMS. 

After reviewing concurrent data it was determined that both PM10 measurements were no 

longer needed at the site. Daily data will continue to be available at this site. 

5.2 Casa Grande Downtown PM2.5 

Section 3.5 Measurement Quality Checks described the shortage of a PM2.5 precision 

measurement site in the network. This shortage was corrected at the beginning of the 

2009 sample year with the move from 1 in 3 sample frequency to 1 in 6 using the existing 

samplers. If in future years additional equipment is available, a return to the 1 in 3 

schedule will be made. 

5.3 Pinal County Housing Relocation 

During 2008-2009 a portion of the Pinal County Housing site will be moved from its 

current location to a new area approximately 20 Yards to the south. The purpose of the 

relocation is to gain additional space to accommodate a monitoring shelter and equipment 

needed for the planned EPA/Pinal County 2008-2009 Rural Coarse Particulate Speciation 

Study. The move will not result in a substantial change in the site exposures or pollutant 

concentrations. 

Additionally, a PSD level meteorological site is begin evaluated for the Pinal County 

Housing site. If funding is available the 10 meter tower and appropriate equipment will 

be added during 2009. 

5.4 Medium Volume Precision Measurement 

As discussed in Section 3.5, the PM10 network currently lacks a precision measurement 

for medium volume samplers. This precision measurement first became necessary with 

the addition of a Thermo PM10 Partisol 2000H to the network in November of 2007. If 

funding is available, Pinal County will procure the required equipment during the 2009-

2010 monitoring year and begin measurement site in the 2010 sample year. 
40
41

6.0 Data Trends 

This section provides an overall description of the pollutants currently collected and 

provides trends for O3, PM10 and PM2.5 in Pinal County. Appendix C of the document 

includes a complete data set for each pollutant. 

In order to discuss this information, it is necessary to clarify the dual meanings for the 

word “exceedance”. The common understanding, an exceedance occurs whenever a value 

exceeds a reference value. However, for purposes of defining what constitutes a violation 

of several of the ambient air quality standards, relevant EPA regulations define 

“exceedances” as discrete events, and the various standards define a violation as 

respectively occurring when either the actual or the expected number of exceedances is 

greater than one per year. 

In contrast, all other ambient air quality standards rely on numerical averaging to define 

what complies with or violates the standard. For those standards, a monitored value 

above the defined standard may contribute toward an average that violates the standard, 

but that monitored value does not constitute an “exceedance” in a regulatory sense. 

In the case of the eight-hour ozone standard, the first three observed eight-hour 

concentrations above the standard reference value are not even considered for purposes of 

determining compliance, and only the fourth high value counts towards the calculated 

average that may violate the standard. This document will use the term excursion to 

denote values that are greater than a numerical averaging standard. 
42

6.1 Carbon Monoxide 

Carbon monoxide is a tasteless, odorless, colorless gas that competes with oxygen in the 

bloodstream. Carbon monoxide binds to hemoglobin in the bloodstream and thereby 

impairs oxygen transport. This decrease in oxygen transport can result in a reduction of 

exercise tolerance, an increase in the visual threshold for light awareness, headaches, and 

dizziness. 

The largest source of carbon monoxide is vehicles, which produce the pollutant through 

the incomplete combustion of fuels. Elevated levels generally occur near major 

intersections where large numbers of vehicles pass through at a slow rate. Peak 

concentrations are generally recorded between November and February. This is caused 

by vehicles producing more carbon monoxide in cold weather and the inversion 

conditions at this time of year trapping a stable and stagnate layer of air near the earth’s 

surface. 

The carbon monoxide NAAQS has two forms, a one-hour standard of 35 ppm, and an 

eight-hour standard of 9 ppm. 

Carbon Monoxide monitoring was discontinued at the Apache Junction and Casa Grande 

sites as of May of 2002 and October of 2002, respectively. 

Between 1996 and 2002, the highest one-hour average recorded at either monitoring site 

was approximately 10% of the standard and the highest eight-hour average recorded was 

approximately 15% of the standard. Considering the relatively low levels and to better 

utilize resources, the carbon monoxide monitors were discontinued. If the NAAQS or 

conditions change and carbon monoxide monitoring is potentially required, Pinal County 

will evaluate the possibility of resuming data collection. 

Carbon Monoxide data summaries are presented in Appendix C. 
43

6.2 Ozone 

Ozone can be found both as a natural component of the atmosphere and as a pollutant. 

The ozone layer located in the stratosphere, approximately eight to thirty miles above the 

earth’s surface, absorbs harmful ultraviolet radiation before it can reach the earth’s 

surface. The ozone found at the earth’s surface is a pollutant produced through chemical 

reactions that involve volatile organic compounds, nitrogen oxides, and sunlight. Sources 

of volatile organic compounds include vehicles and other gasoline powered motors, 

industrial processes, and biogenic emissions from plants. Sources of nitrogen oxides 

include vehicles, construction equipment, trains, electric power plants, industrial sources, 

and biogenic emissions from soil. Exposure to elevated ozone concentrations leads to 

impaired lung function in humans and plant damage by impairing plant respiration. 

The official ozone season in Arizona, as defined by EPA, is January through December. 

Many ozone monitors in Arizona operate year round, however when reviewing historic 

ozone data it can be seen that the highest concentrations generally occur during the 

months of April through October when temperatures are highest. In Section 2.5, Ozone 

Season Definition, a request and justification are presented to designate the Pinal County 

ozone season to be April through October. 

Refer to Section 1.0 for a detailed description of the ozone standards and Appendix C for 

1-hour and 8-hour data summaries. 

The following subsections discuss the ozone trends in Pinal County. Generally, Pinal 

County easily meets the former one-hour standard, but some areas approach the revised 

eight-hour standard. Refer to Appendix C for county-wide one-hour and eight-hour ozone 

data. 
44

6.2.1 One-Hour Ozone 

Pinal County met the former one-hour ozone standard. Even though this standard has 

been revoked, one-hour ozone data will continue to be reported in this document to assess 

trends. A single exceedance of the one-hour standard was recorded in Apache Junction in 

1995 but was not a violation because the standard allowed one exceedance per calendar 

year. No exceedances of the 1-hour standard were recorded at Casa Grande, Queen 

Valley, Combs, Maricopa, or Pinal Air Park. 

Given the still modest level of urban and industrial development in most of Pinal County, 

conjecture supports a conclusion that a large portion of the ozone recorded at these six 

sites is a result of transport from the Phoenix urban area or elsewhere. Daily maximum 

one-hour averages at Apache junction and Queen Valley in 2008 were among the highest 

downwind of the Phoenix metropolitan area, The sites recorded concentrations of 98 and 

99 PPB, respectively. In other locations the 1 hour average ozone concentrations have 

generally decreased over time. Several sites show an increase in 2008 over the previous 

year. In general, the long term trend is downward as evident with Casa Grande and 

Apache Junction, the two long term sites. 

Figure 6-1 shows the one-hour maximum readings recorded at Apache Junction, Casa 

Grande, Queen Valley, Combs, Maricopa, and Pinal Air Park. 

Figure 6-1: One-Hour Ozone Trends – Maximum Concentration 

60

75

90

105

120

135

1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008

Year

ppb

1 Hour Standard - revoked Apache Junction 1 Hour Max Casa Grande

Combs Maricopa Pinal Air Park

Queen Valley
45

6.2.2 Eight-Hour Ozone 

As with the 1-hour averages shown above, conjecture supports a conclusion that a large 

portion of the ozone recorded at these six sites is a result of transport from the Phoenix 

urban area or elsewhere. Daily maximum 8-hour averages remain elevated at Apache 

Junction and Queen Valley. In general, the 8-hour average ozone concentrations have 

decreased over time at the two long term sites, Apache Junction and Casa Grande. Many 

of the sites show an increase in 2008 which is also reflected in the 1-hour average 

concentrations. Overall, 2006 was a high ozone year across all networks in Arizona with 

2008 very close at most Pinal County sites. 

Figure 6-2 shows the fourth highest eight-hour average recorded at Apache Junction, 

Casa Grande, Queen Valley, Combs, Maricopa, and Pinal Air Park. 

Figure 6-2: Eight-Hour Ozone Trends – 4th Highest Concentration 

50

55

60

65

70

75

80

85

90

95

1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008

Year

ppb

8 Hour Standard 1997-2007 8 Hour Standard 2008 Apache Junction

Casa Grande Combs Maricopa

Pinal Air Park Queen Valley
46

6.3 Particulate Matter smaller than 10 microns (PM10) 

PM10 is airborne particles less than or equal to ten microns (1 micron = 10-4 centimeters) 

in diameter. PM10 can result from many sources, such as re-entrained dust from vehicles 

traveling on paved roads, vehicles traveling on unpaved roads, earth moving activities, 

bulk material handling, wind blown dust, and combustion processes, notably power 

plants and diesel engines. 

When particulate matter is inhaled into the respiratory tract the health effects depend on 

the size of the particle. Particles larger than ten microns are generally removed from the 

respiratory system by sneezing. Particles between five microns and ten microns in size 

can either be removed from the respiratory system by sneezing or moved up the 

respiratory tract by cilia (hair like projections) in the lung. Once the particulates have 

been moved back up the respiratory tract they may be swallowed and absorbed in the 

gastrointestinal tract, where they may be excreted. Particles ranging from two microns to 

five microns are generally deposited deeper into the respiratory tract. Still, cilia action 

has the potential to move the particles back up the respiratory tract, where they may be 

swallowed and absorbed in the gastrointestinal track. Particulates smaller than two 

microns may reach an area of the lung called the alveolar region. This is the region of the 

lung where absorption into the bloodstream is most likely. 

Refer to section 1.0 for a detailed description of the PM10 standards and Appendix C for a 

summary of PM10 data collected throughout Pinal County. 

The following subsections discuss the values, trends and contributing sources for each 

PM10 monitoring site. The data presented here reflects the application of Pinal County’s 

Natural Events Action Plan (NEAP). Generally, the Pinal County NEAP allowed for 

exclusion of data where the elevated particulate concentrations resulted from certain 

defined high wind conditions. 

An initial Pinal County NEAP was adopted in 1997. Underlying EPA guidance calls for a 

five-year review of such a plan. In 2002 Pinal County Air Quality proposed to renew the 

existing NEAP. Although EPA did not comment on the 1997 Pinal County NEAP, the 

EPA expressed a number of concerns as part of the review process in 2002. As a result of 

the review, the EPA informed Pinal County Air Quality that it would not approve a 

NEAP for the area at this time. The data included in this document invokes the 1997 

NEAP in reporting data through the five-year anniversary date of December 5, 2002. 

However, none of the data collected after this date has been subjected to the 1997 NEAP. 

In 2006 ADEQ initiated a NEAP program to identify regional wind blown events, or 

natural events that resulted in elevated PM10 concentrations. Pinal County continuous 

PM10 TEOM data was reviewed as part of this process. When a regional wind blown 

event was identified as a contributor to elevated PM10 concentrations or exceedances, the 

continuous TEOM data was submitted to the EPA Region IX office for concurrence. The 

EPA did not concur that the 2006 Pinal County data should be flagged as a natural event 

since Best Available Control Measures (BACM) were not implemented in Pinal County 

during this time period. The data presented in this document includes all PM10

concentrations recorded in 2006; the natural events have not been removed. 
47

In March of 2007 EPA replaced the Natural Events Action Plan with the Treatment of 

Data Influenced by Exceptional Events Rule. This new rule allows monitoring agencies 

to submit documentation to EPA that shows an exceedance would not have occurred “but 

for” the exceptional event. Pinal County Air Quality submitted an Exceptional Events 

package to EPA asking that thirty two events be excluded from the 2007 PM10 data set 

and will submit a 2008 package consisting of sixteen events. The 2007 and 2008 

Exceptional Events package asserts that the exceedances listed in the package would not 

have occurred “but for” the exceptional events (namely elevated wind speeds). If EPA 

concurs with Pinal County Air Quality’s conclusion that these are exceptional events the 

exceedances listed in the package will be excluded from the data set used for determining 

compliance with the NAAQS. This document does not exclude any of the 2007 or 2008 

PM10 exceedances since EPA has yet to concur with our assertions.
48

6.3.1 24-Hour PM10 Trends 

Figure 6-3, 6-4a, and 6-4b illustrate maximum 24-hour average PM10 values collected 

throughout Pinal County. To better illustrate the range in concentrations the figures are 

separated into two categories, highest and lowest concentration sites. Maximum PM10

concentrations typically vary from year to year because they result from local sources or 

events. 

Figure 6-3 shows trends at the highest concentration sites; Stanfield, City of Maricopa, 

Pinal County Housing, and Cowtown. It is evident from the illustration that the each of 

the sites has recorded 24-hour average concentrations in excess of the PM10 standard of 

150μg/m3

.. In this figure Stanfield has the longest record and a general trend towards 

higher concentrations over time, particularly in recent years. 

Note that for 2007 and 2008 days flagged as exceptional event by Pinal County were not 

removed from the data set. The events are pending concurrence from EPA Region IX. 

The Casa Grande continuous PM10 TEOM sampler is included in this group since 

inclusion of the natural event data results in the monitoring exceeding the standard. 

Figure 6-3: Maximum 24-Hour PM10 Concentration at Highest Sites 

0

250

500

750

1000

1250

1500

1750

2000

2250

2500

1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008

ug/m3

Standard City of Maricopa (TEOM)

Stanfield (HiVol) Stanfield (47mm) Stanfield (TEOM) Pinal County Housing East (HiVol)

Pinal County Housing (TEOM) Cowtown (47mm)

Cowtown (TEOM) Casa Grande (TEOM) Combs (TEOM)

Figures 6-4a and 6-4b show 24-hour trends for sites with concentrations less than the 

standard. Apache Junction and the Casa Grande filter based data, shown in figure 6-4a, 

are below the standard for the period of record. Eloy and Mammoth filter based data, 

shown in figure 6-4b, show rather large reductions in 2004. 
49

Figure 6-4a: Maximum 24-Hour PM10 Concentration - Lowest Sites Group A 

0

25

50

75

100

125

150

175

200

1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008

ug/m3

Standard Apache Junction Fire Station (HiVol)

Apache Junction North (HiVol) Apache Junction South (HiVol)

Casa Grande (HiVol)

Figure 6-4b: Maximum 24-Hour PM10 Concentration - Lowest Sites Group B 

0

25

50

75

100

125

150

175

200

1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008

ug/m3

Standard Coolidge (HiVol) Eloy (HiVol)

Mammoth (HiVol) Pinal Air Park (HiVol) Riverside (HiVol)
50

6.3.2 Annual PM10 Trends 

Figure 6-5, 6-6a, and 6-6b illustrate annual average PM10 values collected throughout 

Pinal County. To better illustrate the range in concentrations the figures are separated 

into regional categories, Western sites, Central and Southern sites, and Eastern sites. 

Annual averages are no longer comparable to a Federal standard, but offer a valuable 

measure for trend analysis. Before being revoked the annual standard was 50μg/m3. 

Figure 6-5 shows trends at the highest western sites; Stanfield and City of Maricopa. Of 

these sites Stanfield has the longest data record. Although the collection method changed 

in 2006, the increasing trend at Stanfield is evident. Annual averages in the mid-1990s 

were between 30 and 40μg/m3 compared to values ranging from 80 to 90 μg/m3 in 2006 

and 2007. The trend during 2008 showed a slight decrease over 2007. Annual averages at 

Maricopa are comparable to Stanfield, but lack a longer term record. 

Figure 6-5: Annual PM10 Average at Western Sites 

10

20

30

40

50

60

70

80

90

100

1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008

ug/m3

Annual Standard City of Maricopa (TEOM) Stanfield (HiVol)

Stanfield (47mm) Stanfield (TEOM)

The Central and Southern sites, shown in Figure 6-6, include Casa Grande, Coolidge, 

Eloy, Pinal County Housing, and Pinal Air Park. Among these sites Pinal County 

Housing records the highest concentrations, above the revoked annual standard. All sites 

in this group show a generally increasing trend from a rather low year in 2004 through 

2007. In 2008 a slight reduction in annual average is observed across all monitors. 
51

Figure 6-6: Annual PM10 Average at Central and Southern Sites

10

20

30

40

50

60

70

80

90

100

1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008

ug/m3

Annual Standard Casa Grande (HiVol) Casa Grande (TEOM) Coolidge (HiVol)

Eloy (HiVol) Pinal Air Park(HiVol) Pinal County Housing West ( HiVol) Pinal County Housing East ( HiVol) Pinal County Housing (TEOM)

The Eastern sites, shown in Figure 6-7, include Apache Junction, Combs, Mammoth and 

Riverside. PM10 measurement at Combs was added during the spring of 2007 therefore 

the first complete year of data is for 2008. During the first full year of data collection, the 

average concentration was 56.4μg/m3at Combs School Apache Junction, Mammoth and 

Riverside are all well below the revoked annual standard. A longer term trend is apparent 

with Apache Junction and Mammoth both showing decreasing values since 2000. 

Figure 6-7: Annual PM10 Average at Northern and Eastern Sites 

10

20

30

40

50

60

70

80

90

100

1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008

ug/m3

Annual Standard Apache Junction North Apache Junction South

Apache Junction Fire Station Combs (TEOM) Riverside

Mammoth
52

Because the values at Cowtown are a factor of 2 to 3 higher than other sites, the site is 

shown alone in Figure 6-8. Annual concentrations are 4 to 5 times higher than the 

revoked standard. The 5 year trend at Cowtown shows a slight decrease in 2004 followed 

by a gradual increase in 2005 and 2006. The 2007 and 2008 averages show a moderate 

decrease in concentration. 

Figure 6-8: Annual PM10 Average at Cowtown 

0

50

100

150

200

250

300

350

2002 2003 2004 2005 2006 2007 2008

ug/m3

Annual Standard Cowtown (47mm) Cowtown (TEOM)
53

6.4 Particulate Matter smaller than 2.5 microns (PM2.5) 

PM2.5 is airborne particles less than or equal to 2.5 microns (1 micron = 10-4 centimeters) 

in diameter. PM2.5 can result from the combustion of fuels in motor vehicles, power 

generation, industrial processes, and from burning wood in residential fireplaces. As 

explained in Section 6.3, the health effects of inhaling particulate matter depends on the 

size of the particle. PM2.5 particles are small enough to reach an area of the lung called 

the alveolar region. This is the region of the lung where absorption into the bloodstream 

is most likely. Elevated PM2.5 levels may aggravate respiratory and cardiopulmonary 

problems. 

Refer to section 1.0 for a detailed description of the PM2.5 standards and Appendix C for 

a summary of PM2.5 data collected throughout Pinal County. 

Special considerations for comparing PM2.5 data to the standard are described at 40 CFR 

Subpart D (58.30). The subpart states that PM2.5 sites with unique-middle scale or microscale representation and hot-spot sites are only eligible for comparison to the 24-hour 

PM2.5 standard. The Cowtown site is characterized as a “local hot spot” site according to 

this definition and can only be used for comparison to the 24-hour PM2.5 standard.
54

6.4.1 PM2.5 24-Hour Trends

Figure 6-9 illustrates 98th percentile PM2.5 values collected at Apache Junction, Casa 

Grande, and Cowtown. It is evident from the illustration that the Apache Junction and 

Casa Grande sites are below the standard over the period of record. Both sites show a 

concentration general range between 15 and 20μg/m3

 with the exception of 2003 when 

values were slightly higher. A slight increase is also apparent in 2007. The 2008 values 

are inline with those recorded in 2007. The 24-Hour values at Casa Grande are typically 

higher than Apache Junction by approximately 25%. 

The Cowtown site shows values above 35μg/m3

 over the 3 years it has been in operation. 

The three year average of the 98th percentile value dropped from 60μg/m3

 in 2007 to 48 

in μg/m3 in 2008. The site violates the PM2.5 24-hour NAAQS even after the decrease in 

concentration. 

Figure 6-9: Network-Wide 24-Hour Average PM2.5 Trends 

0

10

20

30

40

50

60

70

80

90

1999 2000 2001 2002 2003 2004 2005 2006 2007 2008

ug/m3

Standard 1999-2006 Standard 2007 Apache Junction

Casa Grande Cowtown
55

6.4.2 PM2.5 Annual Trends 

Figure 6-10 illustrates annual average PM2.5 values collected at Apache Junction and 

Casa Grande. Both sites show concentrations with a range between 5 and 10μg/m3 with 

the exception of 2003 when values were slightly higher. A slight increase is also apparent 

in 2007 and 2008. As with seen in the 24-Hour averages, the values at Casa Grande are 

typically higher than Apache Junction by approximately 25%. 

As described in the introduction to this section, Cowtown is not compared to the annual 

standard. 

Figure 6-10: Network-Wide Annual Average PM2.5 Trends 

0

2

4

6

8

10

12

14

16

1999 2000 2001 2002 2003 2004 2005 2006 2007 2008

ug/m3

Standard Apache Junction Casa Grande
56
57

Appendix A 

Acronyms & Abbreviations 
58
59

Acronyms & Abbreviations used in this document 

ADT Average Daily Traffic 

AQS Air Quality System 

ADEQ Arizona Department of Environmental Quality 

ARM Approved Regional Method 

BACM Best Available Control Measures 

CAA Clean Air Act 

CASAC Clean Air Scientific Advisory Committee 

CFR Code of Federal Regulations 

CO Carbon Monoxide 

EPA Environmental Protection Agency 

FDMS Filter Dynamics Measurement System 

FEM Federal Equivalent Methods

FRM Federal Reference Methods 

HiVol High Volume PM10 sampler 

IMPROVE Interagency Monitoring of Protected Visual Environments 

MET Meteorological 

MSA Metropolitan Statistical Area 

N/A Not Applicable 

NAAQS National Ambient Air Quality Standards 

NEAP Natural Events Action Plan 

NO2 Nitrogen Dioxide 

O3 Ozone 

PAMS Photochemical Assessment Monitoring Station 

PCAQCD Pinal County Air Quality Control District 

Pb Lead 

PM10 Particulate Matter less than or equal to 10 microns 

PM2.5 Particulate Matter less than or equal to 2.5 microns 

ppm Parts Per Million 

ppb Parts Per Billion 

PSD Prevention of Significant Deterioration 

QAPP Quality Assurance Project Plan 

R&P Rupprecht and Patashnick 

SLAMS State and Local Air Monitoring Stations 

SO2 Sulfur Dioxide 

SPM Special Purpose Monitor 

TEOM Tapered Element Oscillating Microbalance 

μg/m3 Micrograms per Cubic Meter 
60
61

Appendix B 

PCAQCD Monitoring Site Descriptions 
62
63

Apache Junction Fire Station – AJFS AQS Site ID: 04-021-3002 

3955 E. Superstition Blvd. TE, Apache Junction, Arizona 

Latitude: 33.421194° Longitude: -111.503222o Map Datum: WGS 84 

Table B-1 Apache Junction Fire Station (AJFS)

Parameter Instrument #1 Instrument #2 Instrument #3 

Pollutant Type PM10 PM2.5 PM2.5

Date Established 2003 1999 1999 

County ID AJ AJE AJW 

Sampler Make & Model Wedding HiVol R&P 2025 Andersen RAAS2.5-100 

Classification SLAMS SLAMS SPM 

Scale Neighborhood Neighborhood Neighborhood 

Objective Population Population Population 

Inlet Height 3.5 meters 3.7 meters 3.5 meters 

Distance from Tree Dripline 21.2 meters 25.7 meters 24.2 meters 

Obstacle Description None None None 

 Height of Obstacle N/A N/A N/A 

 Distance and Direction N/A N/A N/A 

Airflow Arch 360o 360o 360o

Furnace or Incinerator Flue None None None 

 Distance and Direction N/A N/A N/A 

Distance between Collocated 

Samplers 

5.9 meters 1.5 meters 1.5 meters 

Nearest Road Arroya Arroya Arroya 

 Distance and Direction to Road 43.6 meters - NE 38.1 meters - NE 39.6 meters - NE 

 Traffic Count (ADT) 17 cars per day 17 cars per day 17 cars per day 

Schedule 1 in 6 days 1 in 3 days Backup only 

Surrounding Area Residential / Desert Residential / Desert Residential / Desert 

Site Groundcover Gravel / Vegetative Gravel / Vegetative Gravel / Vegetative 

Frequency of flow rate verifications Quarterly Monthly Monthly 

Last two flow rate audits current current N/A 

Does Site Meet App D&E Criteria Yes Yes Yes 

Notes: The photo was taken while facing west. 
64

Apache Junction Maintenance Yard -AJ AQS Site ID: 04-021-3001 

305 E. Superstition Blvd., Apache Junction, Arizona 

Latitude: 33.4214o Longitude: -111.5436o' Map Datum: WGS 84 

Table B-2 Apache Junction Maintenance Yard (AJ) 

Parameter Instrument #1 Instrument #2 Instrument #3 

Pollutant Type O3 Wind Temp & RH / Pressure 

Date Established 1992 1993 1994 

County ID AJ O3 AJ MET AJ MET 

Sampler Make & Model API 400 RM Young 05305 AQ Vaisala HMP 45C/CS105 

Classification SLAMS N/A N/A 

Scale Neighborhood / Urban N/A N/A 

Objective Population / Transport N/A N/A 

Inlet Height 3 meters 10 meters 3 meters 

Distance from Tree Dripline 12 meters 20 meters 12 meters 

Obstacle Description Building None Building 

 Height of Obstacle 4 meters N/A 4 meters 

 Distance and Direction 5meters –SW N/A 5 meters-SW 

Airflow Arch 280o 360 o 280 o

Furnace or Incinerator Flue None None None 

 Distance and Direction N/A N/A N/A 

Distance between Collocated Samplers N/A N/A N/A 

Nearest Road Hwy 88 Hwy 88 Hwy 88 

 Distance and Direction to Road 35 meters - E 27meters - E 35 meters - E 

 Traffic Count (ADT) 3848 cars per day 3848 cars per day 3848 cars per day 

Schedule Continuous Continuous Continuous 

Probe Material Glass N/A N/A 

Residence Time > 20 sec N/A N/A 

Surrounding Area Gravel lot Gravel lot Gravel lot 

Site Groundcover Gravel Gravel Gravel 

Frequency of one point QC check Bi-weekly N/A N/A 

Last annual performance evaluation current N/A N/A 

Does Site Meet App D&E Criteria Yes N/A N/A 

Notes: The photo was taken while facing west. 
65

Casa Grande Airport - CGA AQS Site ID: 04-021-3003 

660 W. Aero Dr., Casa Grande, Arizona 

Latitude: 32.954361o Longitude: -111.76225o Map Datum: WGS 84 

Table B-3 Casa Grande Airport 

(CGA) 

Parameter Instrument #1 Instrument #2 Instrument #3 

Pollutant Type O3 Wind Temp & RH/Pressure 

Date Established 1991 1991 1994 

County ID CG O3 CG MET CG MET 

Sampler Make & Model API 400E RM Young 05305AQ Vaisala HMP 45C/CS105 

Classification SLAMS N/A N/A 

Scale Neighborhood/Regional N/A N/A 

Objective Population/Transport N/A N/A 

Inlet Height 4.1 meters 11.8 meters 3.2 meters 

Distance from Tree Dripline 8.1 meters None None 

Obstacle Description Tower Tower Tower 

 Height of Obstacle 14 meters 14 meters 14 meters 

 Distance and Direction 6 meters - N Adjacent 6 meters - N 

Airflow Arch 360o 360o 360o

Furnace or Incinerator Flue None None None 

 Distance and Direction N/A N/A N/A 

Distance between Collocated Samplers N/A N/A N/A 

Nearest Road Aero Dr. Aero Dr. Aero Dr. 

 Distance and Direction to Road 22 meters - W 22 meters - W 22 meters - W 

 Traffic Count (ADT) Not Available Not Available Not Available 

Schedule Continuous Continuous Continuous 

Probe Material Glass N/A N/A 

Residence Time > 20 sec N/A N/A 

Surrounding Area Parking Lot / Tarmac Parking Lot / Tarmac Parking Lot / Tarmac 

Site Groundcover Pavement Pavement Pavement 

Frequency of one point QC check Bi-weekly N/A N/A 

Last annual performance evaluation current N/A N/A 

Does Site Meet App D&E Criteria Yes N/A N/A 

Notes: The photo was taken while facing northeast. 
66

Casa Grande Downtown – CGD AQS Site ID: 04-021-0001 

401 Marshall St., Casa Grande, Arizona 

Latitude: 32.877583o Longitude: -111.752222o Map Datum: WGS 84 

Table B-4 Casa Grande Downtown (CGD) 

Parameter Instrument #1 Instrument#2 Instrument #3 Instrument #4 

Pollutant Type PM10 PM2.5 PM2.5 PM10

Date Established 1989 1999 2007 2007 

County ID CG PM10 CG (N) PM2.5 CG (S) PM2.5 CG Downtown 

PM10

Sampler Make & Model R&P 2000-H R&P 2000-H R&P 2000-H R&P 1400a (A/B) 

Classification SLAMS SLAMS SLAMS SPM 

Scale Neighborhood Neighborhood Neighborhood Neighborhood 

Objective Population Population Population Population 

Inlet Height 6.0 meters 6.1 meters 6.0 meters 6.0 meters 

Distance from Tree Dripline 19.6 meters 16.4 meters 19.0 meters 24.8 meters 

Obstacle Description None None None None 

 Height of Obstacle N/A N/A N/A N/A 

 Distance and Direction N/A N/A N/A N/A 

Airflow Arch 360 o 360o 360o 360o 

Furnace or Incinerator Flue Furnace Flue Furnace Flue Furnace Flue Furnace Flue 

 Distance and Direction 5.6 meters - S 7.6 meters - S 4.8 meters - S 9.8 meters - S 

Distance between Collocated 

Samplers 

3.3 meters 2.8 meters 2.8 meters 2.8 meters 

Nearest Road Marshall St. Marshall St. Marshall St. Marshall St. 

 Distance and Direction to Road 20.6 meters – E 18.4 meters – E 19.5 meters - E 20.1 meters - E 

 Traffic Count (ADT) Not available Not available Not available Not available 

Schedule 1 in 6 days 1 in 6 days 1 in 6 days Continuous 

Surrounding Area Business District Business District Business District Business District 

Site Groundcover Pavement Pavement Pavement Pavement 

Frequency of flow rate verifications Quarterly Monthly Monthly Bi-weekly 

Last two flow rate audits current current current current 

Does Site Meet App D&E Criteria Yes Yes Yes Yes 

Notes: The photo was taken while facing northeast. 
67

Combs School – CB AQS Site ID: 04-021-3009 

301 E. Combs Rd., Queen Creek, Arizona 

Latitude: 33.219111o Longitude: -111.561111o Map Datum: WGS 84 

 Table B-5 Combs School (CB) 

Parameter Instrument #1 Instrument #2 

Pollutant Type O3 PM10

Date Established 2002 2007 

County ID CB COMBS PM10

Sampler Make & Model API 400E R&P 1400a (A/B) 

Classification SPM SPM 

Scale Neighborhood / Regional Neighborhood / Regional 

Objective Population / Transport Population / Transport 

Inlet Height 4.9 meters 4.5 meters 

Distance from Tree Dripline 22.9 meters 22.9 meters 

Obstacle Description Playground Canopy School Building 

 Height of Obstacle 4.5 meters 4.0 meters 

 Distance and Direction 4.3 meters - S 7.2 meters - N 

Airflow Arch 360o 360o

Furnace or Incinerator Flue None None 

 Distance and Direction N/A N/A 

Distance between Collocated Samplers N/A N/A 

Nearest Road Combs Rd. Combs Rd. 

 Distance and Direction to Road 89.5 meters - N 89.5 meters - N 

 Traffic Count (ADT) 2459 cars per day 2459 cars per day 

Schedule Continuous / Seasonal Continuous 

Probe Material Glass N/A 

Residence Time > 20 sec N/A 

Surrounding Area School Grounds / Residential School Grounds / Residential 

Site Groundcover Concrete / Dirt Road Concrete / Dirt Road 

Frequency of flow rate verifications N/A Bi-weekly 

Last two flow rate audits N/A Recently Installed 

Frequency of one point QC check Bi-weekly N/A 

Last annual performance evaluation current current 

Does Site Meet App D&E Criteria Yes Yes 

Notes: The picture was taken facing southwest. 
68

Coolidge Maintenance Yard – CLDG AQS Site ID: 04-021-3004 

212 E. Broadway, Coolidge, Arizona 

Latitude: 32.978556o Longitude: -111.514833o Map Datum: WGS 84 

Table B-6 Coolidge Maintenance Yard (CLDG) 

Parameter Instrument #1 

Pollutant Type PM10

Date Established 1992 

County ID CLDG 

Sampler Make & Model Wedding HiVol 

Classification SLAMS 

Scale Neighborhood 

Objective Population 

Inlet Height 3.4 meters 

Distance from Tree Dripline None 

Obstacle Description Building 

 Height of Obstacle 3.2 meters 

 Distance and Direction 5.7 meters - NE 

Airflow Arch 360o

Furnace or Incinerator Flue None 

 Distance and Direction N/A 

Distance between Collocated 

Samplers 

N/A 

Nearest Road Pacific St. 

 Distance and Direction to Road 7.9 meters – W 

 Traffic Count (ADT) 164 cars per day 

Schedule 1 in 6 days 

Surrounding Area Residential 

Site Groundcover Gravel / Vegetative 

Frequency of flow rate verifications Quarterly 

Last two flow rate audits current

Does Site Meet App D&E Criteria Yes 

 Notes: The photo was taken facing north. 
69

Cowtown Road – CWTN AQS ID: 04-021-3013 

1.1 37580 W. Maricopa-Casa Grande Highway, Maricopa, Arizona 

Latitude: 33.01053 Longitude: -111.97205o Map Datum: WGS 84 

 Table B-7 Cowtown Road (CWTN) 

Parameter Instrument #1 Instrument #2 Instrument #3 

Pollutant Type PM10 PM10 PM2.5

Date Established 2001 2005 2005 

County ID CWTN TEOM CWTN PM10 CWTN PM2.5 

Sampler Make & Model R&P 1400a (A/B) R&P 2000-H R&P 2000-H 

Classification SPM SPM SPM 

Scale Microscale Microscale Microscale

Objective Population/Source Impact Population/Source Impact Population/Source Impact 

Inlet Height 3.2 meters 3.4 meters 3.4 meters 

Distance from Tree Dripline None None None 

Obstacle Description None None None 

 Height of Obstacle N/A N/A N/A 

 Distance and Direction N/A N/A N/A 

Airflow Arch 360o 360o 360o 

Furnace or Incinerator Flue None None None 

 Distance and Direction N/A N/A N/A 

Distance between Collocated 

Samplers 

0.7 meters 1.6 meters 1.6 meters 

Nearest Road Casa Grande-Maricopa 

Hwy 

Casa Grande-Maricopa 

Hwy 

Casa Grande-Maricopa 

Hwy 

 Distance and Direction to Road 53.6 meters - S 65.5 meters - S 65.5 meters - S 

 Traffic Count (ADT) 2717 cars per day 2717 cars per day 2717 cars per day 

Schedule Continuous 1 in 6 days 1 in 6 days 

Surrounding Area Agricultural / Feedlots Agricultural / Feedlots Agricultural / Feedlots 

Site Groundcover Vegetative Vegetative Vegetative 

Frequency of flow rate verifications Bi-weekly Monthly Monthly 

Last two flow rate audits current current current

Does Site Meet App D&E Criteria Yes Yes Yes 

Notes: The picture was taken facing east. 
70

Table B-7 continued Cowtown Road (CWTN)

Parameter Instrument #4 Instrument #5 

Pollutant Type Wind Temp&RH/Pressure 

Date Established 2002 2002 

County ID CWTN MET CWTN MET 

Sampler Make & Model RM Young 05305 AQ Viasala HMP35C/PTA427 

Classification N/A N/A 

Scale N/A N/A 

Objective N/A N/A 

Inlet Height 3.5 meters 2.9 meters 

Distance from Tree Dripline None None 

Obstacle Description None None 

 Height of Obstacle N/A N/A 

 Distance and Direction N/A N/A 

Airflow Arch 360o 360o

Furnace or Incinerator Flue None None 

 Distance and Direction N/A N/A 

Distance between Collocated 

Samplers 

N/A N/A 

Nearest Road Casa Grande-Maricopa Hwy Casa Grande-Maricopa Hwy 

 Distance and Direction to 

Road 

53.6 meters - S 53.6 meters - S 

 Traffic Count (ADT) 2717 cars per day 2717 cars per day 

Schedule Continuous Continuous 

Surrounding Area Agricultural / Feedlots Agricultural / Feedlots 

Site Groundcover Vegetative Vegetative 

Frequency of flow rate 

verifications 

N/A N/A 

Last two flow rate audits N/A N/A 

Does Site Meet App D&E 

Criteria 

N/A N/A 
71

Eloy County Complex - ELY AQS Site ID: 04-021-3014 

801 N. Main St, Eloy, Arizona 

Latitude: 32.757639o Longitude: -111.554861o Map Datum: WGS 84 

Table B-8 Eloy County Complex (ELY) 

Parameter Instrument #1 

Pollutant Type PM10

Date Established 2007 

County ID ELY 

Sampler Make & Model Andersen HiVol 

Classification SLAMS 

Scale Neighborhood 

Objective Population 

Inlet Height 5.2 meters 

Distance from Tree Dripline N/A 

Obstacle Description None 

 Height of Obstacle N/A 

 Distance and Direction N/A 

Airflow Arch 360o

Furnace or Incinerator Flue None 

 Distance and Direction N/A 

Distance between Collocated Samplers N/A 

Nearest Road Main St. 

 Distance and Direction to Road 31.0 meters – W 

 Traffic Count (ADT) Not available 

Schedule 1 in 6 days 

Surrounding Area Residential / Business 

Site Groundcover Pavement 

Frequency of flow rate verifications Quarterly 

Last two flow rate audits current 

Does Site Meet App D&E Criteria Yes 

 Notes: The picture was taking facing east. 
72

Mammoth County Complex -MAM AQS Site ID: 04-021-3006 

118 S. Catalina, Mammoth, Arizona 

Latitude: 32.719639o Longitude: -110.643o Map Datum: WGS 84 

Table B-9 Mammoth County Complex (MAM) 

Parameter Instrument #1 

Pollutant Type PM10

Date Established 1995 

County ID MAM 

Sampler Make & Model Andersen HiVol 

Classification SLAMS 

Scale Neighborhood 

Objective Population / Background 

Inlet Height 5.0 meters 

Distance from Tree Dripline 10.8 meters 

Obstacle Description None 

 Height of Obstacle N/A 

 Distance and Direction N/A 

Airflow Arch 360o

Furnace or Incinerator Flue Furnace 

 Distance and Direction 5 meters – W 

Distance between Collocated Samplers N/A 

Nearest Road Catalina St. 

 Distance and Direction to Road 18.9 meters – SE 

 Traffic Count (ADT) Not available 

Schedule 1 in 6 days 

Surrounding Area Residential 

Site Groundcover Pavement 

Frequency of flow rate verifications Quarterly 

Last two flow rate audits current 

Does Site Meet App D&E Criteria Yes 

 Notes: The picture was taken facing north. 
73

(City of) Maricopa County Complex - MCPA AQS Site ID: 04-021-3010 

44625 W. Garvey Rd., Maricopa, Arizona 

Latitude: 33.058972o Longitude: -112.046917o Map Datum: WGS 84 

Table B-10 (City of) Maricopa County Complex (MCPA) 

Parameter Instrument #1 Instrument #2 

Pollutant Type O3 PM10

Date Established 2002 2005 

County ID MCPA O3 MCPA PM10

Sampler Make & Model API 400 R&P 1400a (A/B) 

Classification SPM SPM 

Scale Neighborhood / Regional Neighborhood 

Objective Population / Transport Population 

Inlet Height 3.9 meters 3.1 meters 

Distance from Tree Dripline None None 

Obstacle Description Building Building 

 Height of Obstacle 3.4 meters 3.4 meters 

 Distance and Direction 6.3 meters - W 6.3 meters – W 

Airflow Arch 360o 360o 

Furnace or Incinerator Flue Furnace Flue Furnace Flue 

 Distance and Direction 8.2 meters - SW 6.7 meters – SW 

Distance between Collocated Samplers 1.4 meters 1.4 meters 

Nearest Road Garvey Rd. Garvey Rd. 

 Distance and Direction to Road 65 meters - W 65 meters - W 

 Traffic Count (ADT) 6787 cars per day 6787 cars per day 

Schedule Continuous / Seasonal Continuous 

Probe Material Glass N/A 

Residence Time > 20 sec N/A 

Surrounding Area Vacant Lot / Business Vacant Lot / Business 

Site Groundcover Gravel / Vegetative Gravel / Vegetative 

Frequency of flow rate verifications N/A Bi-weekly 

Last two flow rate audits N/A 4/26/05, 8/15/06 

Frequency of one point QC check Bi-weekly N/A 

Last annual performance evaluation current current

Does Site Meet App D&E Criteria Yes Yes 

Notes: The picture was taken facing north. 
74

 Pinal Air Park – PP AQS Site ID: 04-021-3007

Water Well #2, Pinal Air Park Rd., Marana, Arizona 

Latitude: 32.508306o Longitude: -111.308056o Map Datum: WGS 84 

 Table B-11 Pinal Air Park (PP) 

Parameter Instrument #1 Instrument #2 

Pollutant Type PM10 O3

Date Established 1993 2002 

County ID PP PM10 PP O3

Sampler Make & Model Andersen HiVol API 400 

Classification SLAMS SPM 

Scale Regional Regional 

Objective Background Transport 

Inlet Height 4 meters 4.1 meters 

Distance from Tree Dripline None None 

Obstacle Description None None 

 Height of Obstacle N/A N/A 

 Distance and Direction N/A N/A 

Airflow Arch 360o 360o

Furnace or Incinerator Flue None None 

 Distance and Direction N/A N/A 

Distance between Collocated Samplers 16.1 meters 16.1 meters 

Nearest Road Service blacktop Service blacktop 

 Distance and Direction to Road 65 meters – E 54.2 meters – E 

 Traffic Count (ADT) Not available Not available 

Schedule 1 in 6 days Continuous / Seasonal 

Probe Material N/A Glass 

Residence Time N/A > 20 sec 

Surrounding Area Desert Desert 

Site Groundcover Vegetative Vegetative 

Frequency of flow rate verifications Quarterly N/A 

Last two flow rate audits current current

Frequency of one point QC check N/A Bi-weekly 

Last annual performance evaluation N/A 7/20/06 

Does Site Meet App D&E Criteria Yes Yes 

Notes: The picture was taken facing southwest. 
75

Pinal County Housing Complex - PCH AQS Site ID: 04-021-3011 

970 N. Eleven Mile Corner Rd., Casa Grande, Arizona 

Latitude: 32.891056o Longitude: -111.5705o Map Datum: WGS 84 

 

Table B-12 Pinal County Housing Complex (PCH) 

Parameter Instrument #1 Instrument #2 Instrument #3 

Pollutant Type PM10 PM10 PM10

Date Established 2002 2002 2004 

County ID PCH TEOM PCHE PM10 PCHW PM10

Sampler Make and Model R&P 1400a (A/B) Wedding HiVol Wedding HiVol 

Classification SPM SLAMS SLAMS 

Scale Neighborhood Neighborhood Neighborhood 

Objective Population Population Population 

Inlet Height 2.8 meters 3.0 meters 3.0 meters 

Distance from Tree Dripline 13.7 meters 11.6 meters 12.1 meters 

Obstacle Description Shed Shed Shed 

Height of Obstacle 2.6 meters 2.6 meters 2.6 meters 

Distance & Direction 10.2 meters – W 5.9 meters – SW 8.1 meters – SW 

Airflow Arch 360o 360 o 360 o

Furnace or Incinerator Flue None None None 

Distance & Direction N/A N/A N/A 

Distance between Collocated Samplers 3.5 meters 2.3 meters 2.3 meters 

Nearest Road Eleven Mile Corner 

Rd. 

Eleven Mile Corner Rd. Eleven Mile Corner 

Rd. 

Distance & Direction to Road 400 meters – E 400 meters – E 400 meters – E 

Traffic Count (ADT) 653 cars per day 653 cars per day 653 cars per day 

Schedule Continuous 1 in 6 days 1 in 6 days 

Surrounding Area Agricultural / 

Residential 

Agricultural / Residential Agricultural / 

Residential 

Site Groundcover Gravel / Vegetative Gravel / Vegetative Gravel / Vegetative 

Frequency of flow rate verifications Bi-weekly Quarterly Quarterly 

Last two flow rate audits current current current

Does Site Meet App D&E Criteria Yes Yes Yes 

Notes: The picture was taken facing north. 
76

Table B-12 Pinal County Housing Complex (PCH) cont. 

Parameter Instrument#4 Instrument #5 

Pollutant Type Wind Temp & RH/Pressure 

Date Established 2002 2002 

County ID PCH MET PCH MET 

Sampler Make and Model RM Young 05305 AQ Viasala HMP35C/PTA427 

Classification N/A N/A 

Scale N/A N/A 

Objective N/A N/A 

Inlet Height 3.2 meters 2.8 meters 

Distance from Tree Dripline 13.7 meters 13.7 meters 

Obstacle Description Shed Shed 

Height of Obstacle 2.6 meters 2.6 meters 

Distance & Direction 11.1 meters – W 10.6 meters – W 

Airflow Arch 360o 360o

Furnace or Incinerator Flue None None 

Distance & Direction N/A N/A 

Distance between Collocated Samplers N/A N/A 

Nearest Road Eleven Mile Corner Rd. Eleven Mile Corner Rd. 

Distance & Direction to Road 400 meters – E 400 meters – E 

Traffic Count (ADT) 653 cars per day 653 cars per day 

Schedule Continuous Continuous 

Surrounding Area Agricultural / 

Residential 

Agricultural / Residential 

Site Groundcover Gravel / Vegetative Gravel / Vegetative 

Frequency of flow rate verifications N/A N/A 

Last two flow rate audits current current

Does Site Meet App D&E Criteria N/A N/A 
77

Queen Valley - QV AQS Site ID: 04-021-8001 

10 S. Queen Anne Dr., Queen Valley, Arizona 

Latitude: 33.293465o Longitude: -111.285594o Map Datum: WGS 84 

Table B-13 QueenValley (QV) 

Parameter Instrument #1 Instrument #2 

Pollutant Type O3 PM2.5, PM10

Date Established 2001 2001 

County ID QV QVA 

Sampler Make & Model TEI 49C Version II IMPROVE 

Classification SPM SPM 

Scale Urban Urban 

Objective Highest Concentration Visibility 

Inlet Height 4.7 meters 5.4 meters 

Distance from Tree Dripline 2.3 meters 6.0 meters 

Obstacle Description None None 

 Height of Obstacle N/A N/A 

 Distance and Direction N/A N/A 

Airflow Arch 360o 360o

Furnace or Incinerator Flue None None 

 Distance and Direction N/A N/A 

Distance between Collocated Samplers 2.1 meters 2.1 meters 

Nearest Road Queen Anne Dr. Queen Anne Dr. 

 Distance and Direction to Road 93 meters – E 93 meters – E 

 Traffic Count (ADT) 785 cars per day 785 cars per day 

Schedule Continuous / Seasonal 1 in 3 days 

Surrounding Area Desert / Residential Desert / Residential 

Site Groundcover Vegetative Vegetative 

Frequency of one point QC check Bi-weekly N/A 

Last annual performance evaluation Unknown* N/A 

Does Site Meet App D&E Criteria Yes N/A 

Notes: The picture was taken facing east. *For additional detail refer to ADEQ’s State of Arizona 

Monitoring Network Plan for 2009. 
78

Riverside Maintenance Yard - RVSD AQS Site ID: 04-021-3012 

54964 E. Florence-Kelvin Hwy., Kearny, Arizona 

Latitude: 33.105806o Longitude: -110.974194o Map Datum: WGS 84 

 Table B-14 Riverside Maintenance Yard (RS) 

Parameter Instrument #1 

Pollutant Type PM10

Date Established 2003 

County ID RVSD 

Sampler Make & Model Anderson HiVol 

Classification SLAMS 

Scale Neighborhood 

Objective Source Impact 

Inlet Height 3.0 meters 

Distance from Tree Dripline 10.2 meters 

Obstacle Description Building 

 Height of Obstacle 3.8 meters 

 Distance and Direction 8.5 meters - NE 

Airflow Arch 360o

Furnace or Incinerator Flue None 

 Distance and Direction N/A 

Distance between Collocated Samplers N/A 

Nearest Road Florence-Kelvin Hwy. 

 Distance and Direction to Road 24.7 meters - E 

 Traffic Count (ADT) 75 cars per day 

Schedule 1 in 6 days 

Surrounding Area Residential / Desert 

Site Groundcover Gravel 

Frequency of flow rate verifications Quarterly 

Last two flow rate audits current 

Does Site Meet App D&E Criteria Yes 

Notes: The picture was taken facing north. 
79

Stanfield County Complex - STNF AQS Site ID: 04-021-3008 

36697 W. Papago Dr., Stanfield, Arizona 

Latitude: 32.881194o Longitude: -111.962o Map Datum: WGS 84 

 Table B-15 Stanfield County Complex (STNF) 

Parameter Instrument#1 Instrument#2 Instrument#3 

Pollutant Type PM10 PM10 Video 

Date Established 1988 2006 2003 

County ID STNF STNF STNF Video 

Sampler Make & Model Wedding HiVol R&P 1400a (A/B) Panasonic 

Classification SLAMS SPM AG-6740 

Scale Neighborhood Neighborhood N/A 

Objective Population Population N/A 

Inlet Height 4.3 meters 4.7 meters 8.2 meters 

Distance from Tree Dripline None None None 

Obstacle Description FD Engine Carport FD Engine 

Carport 

None 

 Height of Obstacle 4.0 meters 4.0 meters N/A 

 Distance and Direction 5.9 meters – N 3.1 meters – S N/A 

Airflow Arch 360o 360o 360o

Furnace or Incinerator Flue None None None 

 Distance and Direction N/A N/A N/A 

Distance between Collocated Samplers N/A 2.3 meters N/A 

Nearest Road Navajo Way Navajo Way Navajo Way 

 Distance and Direction to Road 19 meters – W 21.2 meters – W 21.2 meters – W 

 Traffic Count (ADT) 91 cars per day 91 cars per day 91 cars per day 

Schedule 1 in 6 days 1 in 6 days 1 in 6 days 

Surrounding Area Residential Residential Residential 

Site Groundcover Gravel / Vegetative Gravel / 

Vegetative 

Gravel / 

Vegetative 

Frequency of flow rate verifications Quarterly Bi-weekly N/A 

Last two flow rate audits current current N/A 

Does Site Meet App D&E Criteria Yes Yes Yes 
80
81

Appendix C 

PCAQCD Ambient Air Monitoring Data 

Please refer to Section 1.0 for a detailed description of the NAAQS for ozone, 

PM10 and PM2.5. 
82
83

APACHE JUNCTION CARBON MONOXIDE DATA (in ppm) 

1 HOUR AVERAGES 

STANDARD: In order to meet the standard the second highest reading must be less than 

or equal to 35 ppm. 

Table C-1 

Year Maximum 

Reading

2nd Highest 

Reading

Number of Daily 

Exceedances

Number of Sample Hours

1996 2.60 2.60 0 4884 

1997 2.20 2.00 0 8675 

1998 2.00 2.00 0 8609 

1999 1.90 1.70 0 8057 

2000 1.48 1.39 0 8543 

2001 3.74 3.54 0 6610 

2002a 1.28 1.21 0 3533 

APACHE JUNCTION CARBON MONOXIDE DATA (in ppm) 

8 HOUR AVERAGES 

STANDARD: In order to meet the standard the second highest reading must be less than 

or equal to 9 ppm. 

Table C-2 

Year Maximum 

Reading

2nd Highest 

Reading

Number of Daily 

Exceedances

Number of Sample Hours

1996 1.08 1.00 0 4873 

1997 1.16 1.01 0 8680 

1998 1.28 1.08 0 8613 

1999 0.91 0.86 0 8017 

2000 0.69 0.69 0 8549 

2001 1.06 0.90 0 6633 

2002 a 0.79 0.75 0 3552 

Footnotes: 

a - Carbon Monoxide monitoring was discontinued at the Apache Junction site on 5/28/2002. The 2002 

readings only represent part of the 2002 carbon monoxide season. 
84

CASA GRANDE CARBON MONOXIDE DATA (in ppm) 

1 HOUR AVERAGES 

STANDARD: In order to meet the standard the second highest reading must be less than 

or equal to 35 ppm. 

Table C-3

Year Maximum 

Reading

2nd Highest 

Reading

Number of Daily 

Exceedances

Number of Sample Hours

1996 1.60 1.50 0 8728 

1997 1.50 1.50 0 8595 

1998 3.90 3.60 0 8513 

1999 2.10 1.50 0 7625 

2000 2.45 2.25 0 8416 

2001 1.53 1.10 0 8326 

2002a 1.23 1.22 0 6715 

CASA GRANDE CARBON MONOXIDE DATA (in ppm) 

8 HOUR AVERAGES 

STANDARD: In order to meet the standard the second highest reading must be less than 

or equal to 9 ppm. 

Table C-4 

Year Maximum 

Reading

2nd Highest 

Reading

Number of Daily 

Exceedances

Number of Sample Hours

1996 1.19 1.16 0 8734 

1997 1.29 1.11 0 8634 

1998 1.46 1.46 0 8525 

1999 0.86 0.80 0 7621 

2000 0.95 0.84 0 8420 

2001 0.77 0.76 0 8355 

2002a 0.81 0.76 0 6745 

Footnotes:

a - Carbon Monoxide monitoring was discontinued at the Casa Grande site on 10/11/2002. The 2002 

readings only represent part of the 2002 carbon monoxide season. 
85

APACHE JUNCTION OZONE DATA (in ppm) 

1 HOUR AVERAGES 

Table C-5 

Year Maximum 

Reading

2nd

Highest 

Reading

3rd

Highest 

Reading

4th

Highest 

Reading

Number of 

Daily 

Exceedances

Expected 

Exceedance 

Rate 

Number of 

Sample Hours

1993 0.121 0.110 0.106 0.103 0 0 7654 

1994 0.114 0.110 0.108 0.108 0 0 8123 

1995 0.136 0.122 0.121 0.114 1 1 7776 

1996 0.121 0.115 0.114 0.114 0 0 7832 

1997 0.106 0.097 0.096 0.096 0 0 8731 

1998 0.112 0.112 0.111 0.106 0 0 8377 

1999 0.112 0.111 0.109 0.105 0 0 8447 

2000 0.101 0.101 0.098 0.096 0 0 8579 

2001 0.101 0.096 0.095 0.092 0 0 8050 

2002 0.109 0.097 0.095 0.095 0 0 8199 

2003 0.105 0.096 0.094 0.091 0 0 8721 

2004 0.084 0.079 0.079 0.079 0 0 8592 

2005 0.097 0.089 0.085 0.083 0 0 8694 

2006a 0.106 0.105 0.104 0.095 N/A N/A 8596 

2007a 0.098 0.096 0.095 0.094 N/A N/A 8636 

2008a 0.098 0.094 0.092 0.091 N/A N/A 8724 

Footnotes:

a - The 1-hour ozone standard was revoked in August 2005. One-hour averages are listed here for trend analysis. 

APACHE JUNCTION OZONE DATA (in ppm) 

8 HOUR AVERAGES 

Table C-6 

Year Maximum 

Reading

2nd

Highest 

Reading

3rd

Highest 

Reading

4th

Highest 

Reading

3 Year Avg 

of the 4th 

Highest

Number of 

Daily 

Excursions

Number of 

Sample 

Hours

1993 0.086 0.082 0.080 0.080 N/A 1 7654 

1994 0.089 0.087 0.085 0.085 N/A 5 8116 

1995 0.095 0.093 0.093 0.091 0.085 8 7744 

1996 0.092 0.086 0.085 0.085 0.087 6 7801 

1997 0.084 0.083 0.082 0.082 0.086 0 8727 

1998 0.091 0.089 0.082 0.082 0.083 2 8384 

1999 0.091 0.089 0.081 0.080 0.081 2 8459 

2000 0.087 0.084 0.082 0.082 0.081 1 8592 

2001 0.081 0.081 0.078 0.077 0.079 0 8068 

2002 0.081 0.081 0.080 0.079 0.079 0 8220 

2003 0.090 0.074 0.072 0.072 0.076 1 8743 

2004 0.070 0.070 0.070 0.069 0.073 0 8613 

2005 0.076 0.074 0.071 0.068 0.069 0 8724 

2006 0.094 0.090 0.087 0.084 0.074 4 8618 

2007 0.083 0.080 0.079 0.077 0.076 0 8667 

2008b 0.082 0.081 0.081 0.079 0.080 7 8752 

Footnotes:

b - The 8-hour ozone standard was revised effective May 27, 2008. The previous eight-hour average of 0.080 ppm was 

lowered to 0.075 ppm. 
86

CASA GRANDE OZONE DATA (in ppm) 

1 HOUR AVERAGES 

Table C-7 

Year Maximum 

Reading

2nd 

Highest 

Reading

3rd

Highest 

Reading

4th

Highest 

Reading

Number of 

Daily 

Exceedances

Expected 

Exceedance 

Rate 

Number of 

Sample Hours

1993 0.092 0.090 0.084 0.082 0 0 8720 

1994 0.091 0.091 0.090 0.088 0 0 7894 

1995 0.083 0.083 0.081 0.080 0 0 8638 

1996 0.104 0.091 0.085 0.084 0 0 8708 

1997 0.082 0.082 0.080 0.079 0 0 8653 

1998 0.093 0.079 0.076 0.075 0 0 8478 

1999 0.090 0.087 0.084 0.084 0 0 8436 

2000 0.105 0.094 0.090 0.089 0 0 8262 

2001 0.084 0.084 0.083 0.083 0 0 8561 

2002 0.088 0.088 0.083 0.083 0 0 8687 

2003 0.090 0.089 0.086 0.083 0 0 8203 

2004 0.077 0.077 0.076 0.074 0 0 8643 

2005 0.089 0.088 0.081 0.080 0 0 8580 

2006a 0.083 0.083 0.082 0.080 N/A N/A 8364 

2007a 0.079 0.078 0.075 0.074 N/A N/A 8623 

2008a 0.082 0.080 0.080 0.079 N/A N/A 8681 

Footnotes:

a - The 1-hour ozone standard was revoked in August 2005. One-hour averages are listed here for trend analysis. 

CASA GRANDE OZONE DATA (in ppm) 

8 HOUR AVERAGES 

Table C-8 

Year Maximum 

Reading

2nd 

Highest 

Reading

3rd

Highest 

Reading

4th

Highest 

Reading

3 Year Avg 

of the 4th 

Highest

Number of 

Daily 

Excursions

Number 

of Sample 

Hours

1993 0.081 0.074 0.073 0.072 N/A 0 8718 

1994 0.079 0.077 0.076 0.076 N/A 0 7885 

1995 0.077 0.074 0.073 0.071 0.073 0 8632 

1996 0.086 0.081 0.080 0.079 0.075 1 8703 

1997 0.075 0.074 0.073 0.072 0.074 0 8704 

1998 0.070 0.069 0.069 0.068 0.073 0 8480 

1999 0.083 0.083 0.079 0.078 0.072 0 8424 

2000 0.087 0.086 0.086 0.085 0.077 5 8257 

2001 0.078 0.078 0.074 0.074 0.079 0 8599 

2002 0.080 0.079 0.079 0.077 0.078 0 8715 

2003 0.077 0.074 0.073 0.073 0.074 0 8227 

2004 0.072 0.070 0.070 0.070 0.073 0 8667 

2005 0.081 0.075 0.073 0.072 0.071 0 8594 

2006 0.076 0.077 0.074 0.073 0.071 0 8369 

2007 0.071 0.071 0.071 0.070 0.071 0 8616 

2008b 0.077 0.077 0.074 0.073 0.072 2 8698 

 Footnotes:

 b - The 8-hour ozone standard was revised effective May 27, 2008. The previous eight-hour average of 0.080 ppm 

was lowered to 0.075 ppm. 

 
87

COMBS OZONE DATA (in ppm) 

1 HOUR AVERAGES 

Table C-9 

Year Maximum 

Reading

2nd 

Highest 

Reading

3rd

Highest 

Reading

4th

Highest 

Reading

Number of 

Daily 

Exceedances

Expected 

Exceedance 

Rate 

Number of 

Sample Hours

2002 0.085 0.080 0.080 0.078 0 0 2709 (seasonal) 

2003 0.101 0.096 0.090 0.086 0 0 5059 (seasonal) 

2004 0.080 0.069 0.068 0.067 0 0 4868 (seasonal) 

2005 0.093 0.091 0.088 0.087 0 0 5123 (seasonal) 

2006a 0.095 0.091 0.089 0.086 N/A N/A 5102 (seasonal) 

2007a 0.075 0.072 0.071 0.070 N/A N/A 5100 (seasonal) 

2008a 0.093 0.092 0.086 0.085 N/A N/A 5117 (seasonal) 

Footnotes:

a - The 1-hour ozone standard was revoked in August 2005. One-hour averages are listed here for trend analysis. 

COMBS OZONE DATA (in ppm) 

8 HOUR AVERAGES 

Table C-10 

Year Maximum 

Reading

2nd

Highest 

Reading

3rd

Highest 

Reading

4th

Highest 

Reading

3 Year Avg 

of the 4th 

Highest

Number of 

Daily 

Excursions

Number of 

Sample Hours

2002 0.075 0.074 0.071 0.068 N/A 0 2712 (seasonal) 

2003 0.081 0.073 0.073 0.072 N/A 0 5091 (seasonal) 

2004 0.064 0.062 0.060 0.059 0.066 0 4880 (seasonal) 

2005 0.080 0.077 0.069 0.067 0.066 0 5141 (seasonal) 

2006 0.079 0.073 0.072 0.071 0.066 0 5510 (seasonal) 

2007 0.063 0.062 0.061 0.057 0.065 0 5113 (seasonal) 

2008b 0.074 0.072 0.071 0.071 0.066 0 5133 (seasonal) 

Footnotes:

b - The 8-hour ozone standard was revised effective May 27, 2008. The previous eight-hour average of 0.080 ppm was 

lowered to 0.075 ppm. 

CITY OF MARICOPA OZONE DATA (in ppm) 

1 HOUR AVERAGES 

Table C-11 

Year Maximum 

Reading

2nd 

Highest 

Reading

3rd

Highest 

Reading

4th

Highest 

Reading

Number of 

Daily 

Exceedances

Expected 

Exceedance 

Rate 

Number of 

Sample Hours

2002 0.089 0.086 0.077 0.075 0 0 2805 (seasonal) 

2003 0.093 0.092 0.085 0.085 0 0 5103 (seasonal) 

2004 0.078 0.072 0.072 0.071 0 0 5112 (seasonal) 

2005 0.079 0.078 0.075 0.069 0 0 5080 (seasonal) 

2006a 0.087 0.080 0.0074 0.074 N/A N/A 4893 (seasonal) 

2007a 0.067 0.065 0.064 0.063 N/A N/A 5053 (seasonal) 

2008a 0.085 0.078 0.076 0.075 N/A N/A 5098 (seasonal) 

Footnotes:

a - The 1-hour ozone standard was revoked in August 2005. One-hour averages are listed here for trend analysis. 
88

CITY OF MARICOPA OZONE DATA (in ppm) 

8 HOUR AVERAGES

Table C-12

Year Maximum 

Reading

2nd 

Highest 

Reading

3rd

Highest 

Reading

4th

Highest 

Reading

3 Year Avg 

of the 4th 

Highest

Number of 

Daily 

Excursions

Number of 

Sample Hours

2002 0.083 0.080 0.073 0.068 N/A 0 2811 (seasonal) 

2003 0.082 0.077 0.075 0.075 N/A 0 5110 (seasonal) 

2004 0.072 0.067 0.065 0.064 0.069 0 5136 (seasonal) 

2005 0.070 0.069 0.067 0.062 0.067 0 5082 (seasonal) 

2006 0.082 0.077 0.068 0.068 0.065 0 4889 (seasonal) 

2007 0.061 0.060 0.059 0.059 0.063 0 5068 (seasonal) 

2008b 0.073 0.070 0.070 0.069 0.065 0 5108 (seasonal) 

Footnotes:

b - The 8-hour ozone standard was revised effective May 27, 2008. The previous eight-hour average of 0.080 ppm was 

lowered to 0.075 ppm. 

PINAL AIR PARK OZONE DATA (in ppm) 

1 HOUR AVERAGES 

Table C-13 

Year Maximum 

Reading

2nd 

Highest 

Reading

3rd

Highest 

Reading

4th

Highest 

Reading

Number of 

Daily 

Exceedances

Expected 

Exceedance 

Rate 

Number of 

Sample Hours

2002 0.087 0.085 0.079 0.078 0 0 2789 (seasonal) 

2003 0.083 0.080 0.080 0.079 0 0 5080 (seasonal) 

2004 0.074 0.073 0.072 0.072 0 0 5103 (seasonal) 

2005 0.088 0.085 0.084 0.084 0 0 4984 (seasonal) 

2006a 0.083 0.079 0.077 0.076 N/A N/A 5084 (seasonal) 

2007a 0.078 0.073 0.070 0.070 N/A N/A 5108 (seasonal) 

2008a 0.077 0.077 0.075 0.074 N/A N/A 5080 (seasonal) 

Footnotes:

a - The 1-hour ozone standard was revoked in August 2005. One-hour averages are listed here for trend analysis. 

PINAL AIR PARK OZONE DATA (in ppm) 

8 HOUR AVERAGES

Table C-14

Year Maximum 

Reading

2nd 

Highest 

Reading

3rd

Highest 

Reading

4th

Highest 

Reading

3 Year Avg 

of the 4th 

Highest

Number of 

Daily 

Excursions

Number of 

Sample Hours

2002 0.080 0.074 0.072 0.070 N/A 0 2823 (seasonal) 

2003 0.076 0.075 0.075 0.074 N/A 0 5087 (seasonal) 

2004 0.069 0.069 0.068 0.067 0.070 0 5120 (seasonal) 

2005 0.079 0.079 0.078 0.077 0.072 0 5001 (seasonal) 

2006 0.075 0.072 0.071 0.070 0.071 0 5091 (seasonal) 

2007 0.072 0.071 0.068 0.066 0.071 0 5120 (seasonal) 

2008b 0.071 0.071 0.071 0.070 0.068 0 5091 (seasonal) 

b - The 8-hour ozone standard was revised effective May 27, 2008. The previous eight-hour average of 0.080 ppm was 

lowered to 0.075 ppm. 
89

QUEEN VALLEY OZONE DATA (in ppm) 

1 HOUR AVERAGES 

Table C-15 

Year Maximum 

Reading

2nd 

Highest 

Reading

3rd

Highest 

Reading

4th

Highest 

Reading

Number of 

Daily 

Exceedances

Expected 

Exceedance 

Rate 

Number of 

Sample Hours

2001 0.103 0.103 0.098 0.093 0 0 3651 (seasonal) 

2002 0.112 0.110 0.106 0.099 0 0 5225 (seasonal) 

2003 0.110 0.110 0.107 0.107 0 0 5357 (seasonal) 

2004 0.093 0.092 0.092 0.087 0 0 5081 (seasonal) 

2005 0.117 0.113 0.110 0.105 0 0 5125 (seasonal) 

2006a 0.110 0.109 0.103 0.102 N/A N/A 5360 (seasonal) 

2007a 0.089 0.088 0.088 0.087 N/A N/A 5112 (seasonal) 

2008a 0.099 0.095 0.093 0.091 N/A N/A 5084 (seasonal) 

Footnotes:

a - The 1-hour ozone standard was revoked in August 2005. One-hour averages are listed here for trend analysis. 

QUEEN VALLEY OZONE DATA (IN ppm) 

8 HOUR AVERAGES 

Table C-16 

Year Maximum 

Reading

2nd 

Highest 

Reading

3rd

Highest 

Reading

4th

Highest 

Reading

3 Year 

Avg of the 

4th 

Highest

Number of 

Daily 

Excursions

Number of 

Sample Hours

2001 0.084 0.084 0.080 0.079 N/A 0 3651 (seasonal) 

2002 0.085 0.083 0.083 0.083 N/A 1 5196 (seasonal) 

2003 0.094 0.091 0.090 0.087 0.083 4 5365 (seasonal) 

2004 0.077 0.076 0.074 0.073 0.081 0 5095 (seasonal) 

2005 0.097 0.096 0.086 0.084 0.081 3 5142 (seasonal) 

2006 0.091 0.087 0.080 0.080 0.079 2 5379 (seasonal) 

2007 0.077 0.077 0.076 0.076 0.080 0 5133 (seasonal) 

2008b 0.085 0.082 0.082 0.080 0.078 9 5094 (seasonal) 

b - The 8-hour ozone standard was revised effective May 27, 2008. The previous eight-hour average of 0.080 ppm was 

lowered to 0.075 ppm. 
90

24 HOUR PM10 AVERAGES (IN μg/m3) 

Table C-17 

Year Reading 

Maximum 

Number of Daily 

Exceedances 

Expected 

Exceedance Rate 

3 Year Average of the 

Expected Exceedance Rate 

Apache Junction North (HiVol) 

1995 67.72 0 0 N/A 

1996 34.05 0 0 N/A 

1997 81.0 0 0 0 

1998 61.45 0 0 0 

1999 64.0 0 0 0 

2000 111.4 0 0 0 

2001 49.1 0 0 0 

2002 b 61.5 0 0 0 

2003 j 94.5 0 0 0 

Apache Junction South (HiVol) 

1995 67.91 0 0 N/A 

1996 36.93 0 0 N/A 

1997 81.33 0 0 0 

1998 62.73 0 0 0 

1999 63.5 0 0 0 

2000 107.3 0 0 0 

2001 93.5 0 0 0 

2002 b 62.4 0 0 0 

2003 b,g 91.3 0 0 0 

Apache Junction Fire Station (HiVol) 

2003 b,h 103.3 0 0 N/A 

2004 35.7 0 0 N/A 

2005 47.0 0 0 0 

2006 73.0 0 0 0 

2007 48.0 0 0 0 

2008 57.0 0 0 0 

Casa Grande (HiVol) 

1995 77.39 0 0 N/A 

1996 73.48 0 0 N/A 

1997 a 76.4 0 0 0 

1998 b 75.52 0 0 0 

1999 64.3 0 0 0 

2000 82.5 0 0 0 

2001 104.2 0 0 0 

2002 b 68.5 0 0 0 

2003 98.7 0 0 0 

2004 52.8 0 0 0 

2005 79.2 0 0 0 

2006 81.2 0 0 0 

2007 112.4 0 0 0 

2008 74.0 0 0 0 

Casa Grande (TEOM) 

2007 983.4 7 7 N/A 

2008 203.0 3 3 N/A 

Combs (TEOM) 

2007 969.5 31 44.6 N/A 

2008 270.0 4 4 N/A 

Coolidge (HiVol) 

1995 94.54 0 0 N/A 
91

Year Reading 

Maximum 

Number of Daily 

Exceedances 

Expected 

Exceedance Rate 

3 Year Average of the 

Expected Exceedance Rate 

1996 98.07 0 0 N/A 

1997 a 102.32 0 0 0 

1998 143.79 0 0 0 

1999 83.6 0 0 0 

2000 76.5 0 0 0 

2001 73.4 0 0 0 

2002 b 106.4 0 0 0 

2003 105.7 0 0 0 

2004 57.5 0 0 0 

2005 81.4 0 0 0 

2006 105.5 0 0 0 

2007 82.0 0 0 0 

2008 91.0 0 0 0 

Cowtown (47mm) 

2005 b,k 787.9 8 N/A Avg. > 1.0 

2006 606.0 39 278 Avg. > 1.0 

2007 759.0 24 167 Avg. > 1.0 

2008 465.0 24 146 197 

Cowtown (TEOM) 

2002 a,b 1390.6 209 209 Avg. > 1.0 

2003 718.5 150 150 Avg. > 1.0 

2004 b 600.1 105 105 155 

2005 b 769.6 163 163 139 

2006 1078.9 228 238 169 

2007 1014.0 189 190 197 

2008 609.0 173 175 201 

Eloy (HiVol) 

1995 130.23 0 0 N/A 

1996 80.83 0 0 N/A 

1997 a 81.84 0 0 0 

1998 b 110.48 0 0 0 

1999 141.6 0 0 0 

2000 102.1 0 0 0 

2001 142.2 0 0 0 

2002 b 146.3 0 0 0 

2003 153.9 0 0 0 

2004 46.8 0 0 0 

2005 72.9 0 0 0 

2006 98.7 0 0 0 

2007 o 135.5 0 0 0 

2008 109.0 0 0 0 

Mammoth (HiVol) 

1995 81.3 0 0 N/A 

1996 32.8 0 0 N/A 

1997 46.4 0 0 0 

1998 49.2 0 0 0 

1999 b 50.0 0 0 0 

2000 63.5 0 0 0 

2001 99.2 0 0 0 

2002 b 52.5 0 0 0 

2003 89.4 0 0 0 

2004 30.8 0 0 0 

2005 32.5 0 0 0 

2006 30.7 0 0 0 

2007 39.8 0 0 0 
92

Year Reading 

Maximum 

Number of Daily 

Exceedances 

Expected 

Exceedance Rate 

3 Year Average of the 

Expected Exceedance Rate 

2008 35.0 0 0 0 

City of Maricopa (TEOM) 

2005 l 239.1 18 18 Avg. > 1.0 

2006 429.0 21 21 Avg. > 1.0 

2007 724.0 20 20 21 

2008 520.0 6 6 16 

Pinal Air Park (HiVol) 

1995 65.29 0 0 N/A 

1996 48.31 0 0 N/A 

1997 64.99 0 0 0 

1998 b 67.21 0 0 0 

1999 60.4 0 0 0 

2000 74.2 0 0 0 

2001 b 103.3 0 0 0 

2002 b 62.0 0 0 0 

2003 107.8 0 0 0 

2004 38.8 0 0 0 

2005 122.4 0 0 0 

2006 76.8 0 0 0 

2007 113.0 0 0 0 

2008 55.0 0 0 0 

Pinal County Housing West (HiVol) 

2002 b,f 166.1 1 N/A Avg. > 1.0 

2003 288.6 2 11.5 Avg. > 1.0 

2004 155.1 1 5.8 Avg. > 1.0 

2005 b 157.7 1 6.1 7.8 

2006 152.5 0 0 4.0 

2007 224.0 1 6.5 4.2 

2008 141.0 0 0 3.3 

Pinal County Housing East (HiVol)

2004 113.6 0 0 0 

2005 179.4 2 11.9 Avg. > 1.0 

2006 209.7 3 20.2 10.7 

2007 341.0 1 6.1 12.7 

2008 245.0 1 5.7 10.7 

Pinal County Housing (TEOM)

2002 b,f 394.5 9 9 Avg. > 1.0 

2003 357.8 11 11 Avg. > 1.0 

2004 490.7 7 7 9 

2005 326.0 17 17 11.7 

2006 913.0 33 33.6 19.2 

2007 2253 19 20 23.5 

2008 285.0 10 10 21.2 

Riverside (HiVol) 

2003 b,i 100.7 0 0 N/A 

2004 34.4 0 0 N/A 

2005 35.2 0 0 0 

2006 82.7 0 0 0 

2007 65.0 0 0 0 

2008 52.0 0 0 0 

Stanfield (HiVol) 

1995 85.57 0 0 N/A 

1996 100.33 0 0 N/A 

1997 a 135.34 0 0 0 

1998 112.56 0 0 0 
93

Year Reading 

Maximum 

Number of Daily 

Exceedances 

Expected 

Exceedance Rate 

3 Year Average of the 

Expected Exceedance Rate 

1999 106.6 0 0 0 

2000 148.7 0 0 0 

2001 134.2 0 0 0 

2002 b 351.5 2 13.0 4.0 

2003 b 170.5 1 6.1 6.1 

2004 80.9 0 0 6.1 

2005 172.5 1 5.8 4.0 

Stanfield (47mm) 

2006 m 182.0 2 13.1 Avg. > 1.0 

2007 374.0 6 39.6 Avg. > 1.0 

2008 201.0 2 11.8 21.5 

Stanfield (TEOM) 

2006 b,n 727.4 25 26.5 Avg. > 1.0 

2007 1062.0 25 25.2 Avg. > 1.0 

2008 375.0 14 14 21.9 

Footnotes: 

a - At least one data point during this year was flagged due to an exceptional event and 

excluded from calculation. 

b - At least one quarter during this year had less than 75% data recovery 

c - The Edwards site was located on private property and discontinued on 7/16/1998 at the 

land owners request. 

d - The Miller site was located on private property and discontinued on 11/27/1999 

following the paving of the dirt road being monitored. 

e - The Eleven Mile Corner site was closed on 7/22/2002 due to improper siting 

conditions. 

f - Monitoring began at the Pinal County Housing site on 8/1/2002. The Pinal County 

Housing site replaced the Eleven Mile Corner site. 

g - The Apache Junction South monitor was discontinued on 7/1/2003, and relocated to 

Apache Junction Fire Station. 

h - Monitoring began at the Apache Junction Fire Station site on 7/2/2003. 

i - Monitoring began at the Riverside site on 3/10/2003. 

j - The Apache Junction North monitor was discontinued on 1/1/2004, and relocated to 

Pinal County Housing. 

k - 47mm filter based monitoring began at the Cowtown site on 8/14/05, and data reporting began as of 10/1/05. 

l - Monitoring began at the (City of) Maricopa site on 12/4/04, and data reporting began as of 1/1/05. 

m - The Wedding HiVol sampler was replaced on 4/12/06 with an Andersen RAAS10- 

100 sampler at the Stanfield site. 

n - Beginning in February of 2006 a R&P TEOM 1400a sampler was installed at the 

 Stanfield site. 

o – On 3/2/07 the Andersen HiVol was relocated from a City of Eloy building to a Pinal 

 County building approximately 650 feet to the north-northeast. 
ANNUAL PM10 AVERAGES (IN 

μg/m3) 

Table C-18 

1998 1999 2000 2001 2002 2003 2004 2005 2006 

Apache Junction North (HiVol) 24.6 25.8 27.4 22.7 21.3 b 20.3 hApache Junction South (HiVol) 25.6 27.5 28.4 23.4 21.5 b 20.4 b,eApache Junction Fire Station (HiVol) 26.7 b,f 18.4 19.9 23.6 Casa Grande (HiVol) 30.6 b 35.3 34.7 29.2 30.4 b 31.5 24.4 30.8 35.9 Casa Grande (TEOM) Combs School (TEOM) Coolidge (HiVol) 37.2 39.6 37.4 32.0 32.8 b 35.3 24.5 36.0 44.0 Cowtown (47mm) 294.4 b,i 220.1 Cowtown (TEOM) 261.7 a,b 170.1 132.2 b 200.4 b 230.4 Eloy (HiVol) 43.7 b 45.9 41.7 35.1 46.5 b 41.5 27.8 33.5 38.3 Mammoth (HiVol) 21.8 22.5 b 22.0 22.6 18.8 b 16.4 11.8 13.5 14.8 City of Maricopa (TEOM) 70.1 j 78.6 Pinal Air Park(HiVol) 27.1 b 30.3 30.9 26.7 b 30.2 b 28.6 20.3 22.4 29.5 Pinal County Housing West ( HiVol) 56.6 b,d 61.0 47.1 56.7 b 64.3 Pinal County Housing East ( HiVol) 45.1 58.5 62.8 Pinal County Housing (TEOM) 75.9 b,d 66.6 55.9 68.7 87.1 Riverside (HiVol) 23.9 b,g 15.2 18.1 23.3 Stanfield (HiVol) 41.3 56.6 45.7 41.9 59.7 b 46.1 b 33.9 52.1 Stanfield (47mm) 81.4 k Stanfield (TEOM) 82.6 b,l 

Footnotes: 

a - At least one data point during this year was flagged due to an exceptional event and excluded from calculation. b - At least one quarter during this year had less than 75% data recovery. d - Monitoring began at the Pinal County Housing site on 8/1/2002. The Pinal County Housing site replaced the Eleven Mile Corner site. 

e - The Apache Junction South monitor was discontinued on 7/1/2003, and relocated to Apache Junction Fire Station. f - Monitoring began at the Apache Junction Fire Station site on 7/2/2003. g - Monitoring began at the Riverside site on 3/10/2003. h - The Apache Junction North monitor was discontinued on 1/1/2004, and relocated to Pinal County Housing. 

i - Filter-based sampling began at the Cowtown site on 8/14/05, and data reporting began 10/1/05. j - Monitoring began at the (City of) Maricopa site on 12/4/04, and data reporting began 1/1/05. k - The Wedding HiVol sampler was replaced on 4/12/06 with an Andersen RAAS10-100 sampler at the Stanfield site. l - In February of 2006 a R&P TEOM 1400a sampler was installed at Stanfield. m - On 3/2/07 the Andersen HiVol was relocated from a City of Eloy building to a Pinal County building approximately 650 feet to the  north-northeast. The annual average is from the three quarters at the new location. 
95 

24 HOUR PM2.5 AVERAGES (in μg/m3) 

Table C-19 

Year Maximum Reading 98th Percentile 3 year average of the 98th percentile 

Apache Junction 

1999 18.7 15.5 N/A 

2000 44.5 18.0 N/A 

2001 14.0 13.1 16 

2002 23.5 13.1 15 

2003 a 38.0 21.1 16 

2004 17.0 10.3 15 

2005 12.7 10.6 14 

2006 10.7 9.3 10 

2007 15.9 14.6 12 

2008 23.3 15.4 13 

Casa Grande 

1999 19.5 18.1 N/A 

2000 22.2 18.9 N/A 

2001 18.1 16.7 18 

2002 23.5 20.8 19 

2003 32.2 26.7 21 

2004 16.6 13.7 20 

2005 19.3 16.9 19 

2006 16.1 15.4 15 

2007 26.6 22.4 18 

2008 23.5 22.0 20 

Cowtown 

2005 a,b 144.8 78.9 N/A 

2006 69.4 48.9 N/A 

2007 59.7 53.9 61 

2008 41.7 40.7 48 

Footnotes: 

a – At least one quarter during this year had less than 75% data recovery 

b - 47mm filter based monitoring began at the Cowtown site on 8/14/05, and data reporting began as of 

10/1/05. 
96 

ANNUAL PM2.5 AVERAGES (IN μg/m3) 

Table C-20 

Year Annual Average 3 year average of the annual means 

Apache Junction 

1999 7.41 N/A 

2000 7.28 N/A 

2001 6.26 7.0 

2002 6.39 6.6 

2003 a 6.30 6.3 

2004 a 5.51 6.1 

2005 5.51 5.8 

2006 5.31 5.4 

2007 6.96 5.9 

2008 7.52 6.6 

Casa Grande 

1999 9.53 N/A 

2000 8.48 N/A 

2001 7.73 8.5 

2002 8.46 8.2 

2003 8.42 8.2 

2004 7.13 8.0 

2005 7.33 7.6 

2006 7.55 7.3 

2007 10.25 8.4 

2008 10.61 9.5 

Cowtown 

2005 a,b 33.1 N/A 

2006 22.7 N/A 

2007 22.5 26 

2008 19.6 21.6 

Footnotes: 

a

 - At least one quarter during this year had less than 75% data recovery 

b

 - 47mm filter based monitoring began at the Cowtown site on 8/14/05, and data reporting began as of 

10/1/05. 
97 

Appendix D 

Public Comments 
98 
99 

Appendix D 

This appendix summarizes the public comment period and hearing conducted in relation 

to this document. 

D.1 Public Comment Period 

Pinal County Air Quality will post the draft 2008 Ambient Monitoring Network Review 

and Data Summary on the department’s website for the period of May 1, 2009 to June 1, 

2009. 

D.2 Public Hearing 

Pinal County Air Quality will conduct a public hearing concerning the draft 2008 

Ambient Monitoring Network Review and Data Summary on June 1, 2009. The sign in 

sheet from this meeting will be included in this appendix. 
100 
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104 
105 
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108 
109 
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111 
112 
113