# State of Arizona Exceptional Event Documentation for the

Events of August 25 th 

# through August 28 th 

# 2011, for the

Phoenix PM 10 

# Nonattainment Area

Produced by:

Arizona Department of Environmental Quality

Maricopa County Air Quality Department

Maricopa Association of Governments

Final Report

January 23, 2013

# EXECUTIVE SUMMARY

In 2005, Congress identified a need to account for even ts that result in exceedances of the National

Ambient Air Quality Standards (NAAQS ) that are exceptional in nature 1 

# (e.g., not expected to reoccur or

caused by acts of nature beyond man-made controls). In response, EPA promulgated the Exceptional

Events Rule (EER) to address exceptional events in 40 CFR Pa rts 50 and 51 on March 22, 2007 (72 FR

13560). On May 2, 2011, in an attempt to clarify this rule, EPA released draft guidance documents on the

implementation of the EER to State, tribal and lo cal air agencies for review. Based on numerous

comments EPA received on the May 2011 draft, EPA issu ed a revised draft guidance document in June

2012. The EER allows for states and tribes to “flag” air quality monitoring data as an exceptional event

and exclude those data from use in determinations with respect to exceedances or violations of the

NAAQS, if EPA concurs with the demonstr ation submitted by the flagging agency.

Due to the arid nature of the state, Arizona is high ly susceptible to windblown dust events. These events

are often captured by various air quality monitoring equipment throughout the state, sometimes resulting

in exceedances or violations of the PM10 NAAQS. In the past, the Arizona Department of

Environmental Quality (ADEQ) has submitted exceptiona l event documentation for these events. Due in

part to issues within the EER, obt aining concurrence on these events has been a difficult task. The ADEQ

is now taking a new approach and focusing excepti onal event documentation on ev ents that are believed

to be clear-cut exceptional events that are not controllable by huma n intervention, such as the dust events

which frequently occurred during the monsoon seas on of 2011. This new approach was used for the

exceptional event demonstration submitted in Marc h 2012 by the ADEQ for several PM10 events which

occurred from July 2 – July 8, 2011, in the Phoeni x region. In September 2012, EPA concurred that the

July 2–8, 2011 events were indeed exceptional. As a result, this document is designed to follow the

format used in the July 2–8, 2011 events submission.

This demonstration contains detailed information about the windblown dust events that affected the

Phoenix PM10 nonattainment area during the peri od August 25 – August 28, 2011. During this time

period, 25 exceedances of the PM10 NAAQS occurred within the nonattainment area. Additional

exceedances occurred outside of the Phoenix PM 10 nonattainment area during this time period and

additional documentation may be submitted as a separa te package at a later time. ADEQ contends that

the exceedances that were measured during August 25-28, 2011, within the Phoenix PM10 nonattainment

area were the result of natural events that were not reasonably controllable or preventable. This

assessment report of the August 25-28, 2011 dust events was a collaborative effort involving staff from

the Arizona Department of Envir onmental Quality, Maricopa Associat ion of Governments, Maricopa

County Air Quality Department, and Pinal County Air Quality Control District.

Section I of this assessmen t provides a summary of the exceptional event rules and requirements and lays

out how those rules are met with in this specific assessment.

Section II of this assessment introdu ces the conceptual model of the thu nderstorm events that transpired

during August 25–28, 2011, providing a backgro und narrative of the ex ceptional events.

Section III of this assessment provides data summaries a nd time series graphs which help illustrate that

the events of August 25–28, 2011, produced PM10 concen trations in excess of normal historical

fluctuations.

1 

# Section 319 of the Clear Air Act (CAA), as amended by section 6013 of the Safe Accountable Flexible EfficientTransportation Equity Act: A Legacy for Users (SAFE-TEA-LU of 2005, required EPA to propose the Federal Exceptional

Events Rule (EER) no later than March 1, 2006.



# ii

# Section IV of this assessment details the existing area control measures and demonstrates that despite the

presence and enforcement of these controls, th e events of August 25–28, 2011, were not reasonably

controllable or preventable.

Section V of this assessment establishes a clear causal connection between the natural events of

August 25–28, 2011, and the exceedances of the 24-hour PM10 standard at the monitoring stations. The

evidence in this section (and the prev ious section on historical fluctuati ons) also confirms that the events

in question both affected air quality a nd were the result of natural events.

Section VI of this assessment builds upon the demons tration showing a clear causal connection between

the natural event and the exceedances and concludes there would have been no exceedances during

August 25–28, 2011, but for the presen ce of the natural events.

Section VII contains conclusions that summarize the exceptional events that occurred during the week of

August 25–28, 2011, and relates the requirements in the EER to the information within this document.

iii

# Table of Contents

I. EXCEPTIONAL EVENT RU LE (EER) REQU IREMENTS.....................................1

Procedural Requirements ........................................................................................................ ..........1

Public notification that event wa s occurring (40 CFR 50.14(c)(1(i)) ..................................................1

Place informational flag on data in AQS (40 CFR 50.14(c)(2)(ii)) .....................................................1

Notify EPA of intent to flag through submission of initial event description by July 1 of calendar

year following event (40 CFR 50.14(c)(2)(iii))....................................................................................1

Document that the public comment process was followed for event documentation (40 CFR

50.14(c)(3)(iv))............................................................................................................... ......................2

Submit demonstration suppor ting exceptional event flag (40 CFR 50.14(a)(1-2))..............................2

Documentation Requirements...........................................................................................................3



# II. CONCEPTU AL MODEL..............................................................................................4

Geographic Setting and Climate ................................................................................................. ......4

Geographic Setting of Monitors ................................................................................................. ..........4

Climate ........................................................................................................................ .........................7

Monsoon Season Description and Brief Event Summaries ............................................................8

Conclusions .......................................................................................................................................10



# III. HISTORICAL FLUCTUAT IONS............................................................................18

Regulatory Measures and Control Programs................................................................................22

PM10 Rule Effectiveness..................................................................................................................25

Compliance and Enforcement Activities ........................................................................................26

Conclusions .......................................................................................................................................28



# V. CLEAR CAUSAL RELATION SHIP.........................................................................29

Introduction ......................................................................................................................................29

Event #1 – August 25, 2011:.............................................................................................................29

Event #2 – August 26, 2011:.............................................................................................................38

Event #3 – August 27-28, 2011: .......................................................................................................47

Visibility Cameras ............................................................................................................. ...............63

Conclusion.........................................................................................................................................63



# VI. “BUT FOR” ANALYSIS ...........................................................................................64

VII. CONC LUSIONS .......................................................................................................65

Affects Air Quality ............................................................................................................ ...............65

Not Reasonably Controllable or Preventable ................................................................................65

Natural Event....................................................................................................................................65

Summary ...........................................................................................................................................65

iv

# List of Figures

Figure 2

‐ 1. Phoenix Geographic Setting and PM10 Monitor Locations (source: EPA AQS DataMart, NASA MODIS Satellite,

Google Earth). PM10 monitor locations are indicated by the white markers. .................................................................... 5

Figure 2

‐ 2. Drainage System of Phoenix, Arizona. ........................................................................................................................ 6

Figure 2

‐ 3. Phoenix Monthly Precipitation (top) and Maximum Temperature (bottom) Climatology (source: National Weather

Service)

................................................................................................................................................................................. 7

Figure 2

‐ 4. Cross

‐ section of a thunderstorm creating an outflow boundary and haboob (Source: Desert Meteorology. Thomas

T. Warner. 2004.)

.................................................................................................................................................................. 9

Figure 2

‐ 5. U.S. Drought Monitor analysis released during the time period of the exceedances described in this report. ........ 11

Figure 2

‐ 6. Timeline of PM10 concentrations at monitors throughout the Phoenix Metro area during the period of August 25

‐

28, 2011

............................................................................................................................... ............................................... 12

Figure 3

‐ 1. Plot of daily hourly maximum PM10 concentrations (2007

– 2011) at the Central Phoenix monitoring site. ......... 18

Figure 3

‐ 2. Plot of 24

‐ hour average PM10 concentrations (2007

– 2011) at the Central Phoenix monitoring site. ................... 19

Figure 3

‐ 3. Plot of daily hourly maximum PM10 concentrations (2007

– 2011) at the Higley monitoring site. ......................... 20

Figure 3

‐ 4. Plot of 24

‐ hour average PM10 concentrations (2007

– 2011) at the Higley monitoring site. .................................. 21

Figure 4

‐ 1. Timeline of Maricopa County Fugitive Dust Rules and Ordinances. ......................................................................... 26

Figure 5

‐ 1. Satellite imagery showing strong storms developing and dissipating over northern Mexico. These storms are

believed to have been responsible for the thunderstorm outflow boundary that caused PM10 exceedances throughout

Maricopa and Pinal counties on August 25. ....................................................................................................................... 30

Figure 5

‐ 3. Phoenix nonattainment area PM10 monitor readings and Sky Harbor visibility and wind speed for August 25, 2011.

............................................................................................................................... ............................................................. 31

Figure 5

‐ 2. Pinal County PM10 monitor readings and Casa Grande visibility and wind speed for August 25, 2011. .................. 32

Figure 5

‐ 4. Satellite imagery showing strong storms developing and dissipating over southwestern Arizona. These storms are

believed to have been responsible for the thunderstorm outflow boundary that caused PM10 exceedances in the

eastern portion of the Phoenix PM10 nonattainment area and in Pinal County on August 26. ........................................ 38

Figure 5

‐ 5. Phoenix nonattainment area PM10 monitor readings and Mesa Williams visibility and wind speed for August 26,

2011.

............................................................................................................................... .................................................... 40

Figure 5

‐ 6. Pinal County PM10 monitor readings and Casa Grande visibility and wind speed for August 26, 2011. .................. 41

Figure 5

‐ 7. Satellite imagery showing strong storms developing and dissipating over south

‐ southwestern Arizona. These

storms are believed to have been responsible for the thunderstorm outflow boundary that caused PM10 exceedances

across the Phoenix PM10 nonattainment area and in Pinal County on August 27

‐ 28. ...................................................... 47

Figure 5

‐ 8. Phoenix nonattainment area PM10 monitor readings and Sky Harbor visibility and wind speed for August 27,

2011.

............................................................................................................................... .................................................... 49

Figure 5

‐ 9. Pinal County PM10 monitor readings and Casa Grande visibility and wind speed for August 27, 2011. ................. 50

Figure 5

‐ 10. Phoenix nonattainment area PM10 monitor readings and Mesa Williams visibility and wind speed for August 28,

2011.

............................................................................................................................... .................................................... 51

Figure 5

‐ 11. Pinal County PM10 monitor readings and Casa Grande visibility and wind speed for August 28, 2011. ............... 52



# v

# List of Tables

Table 2

‐ 1. Summary of Statewide PM10 Measurements for August 25, 2011. .......................................................................... 13

Table 2

‐ 2. Summary of Statewide Air Quality Measurements for August 26, 2011. .................................................................. 15

Table 2

‐ 3. Summary of Statewide Air Quality Measurements for August 27, 2011. .................................................................. 16

Table 2

‐ 4. Summary of Statewide Air Quality Measurements for August 28, 2011. .................................................................. 17

Table 4

‐ 1. Rules and Ordinances Regulating Particulate Matter Emissions in Maricopa County ............................................... 23

Table 4

‐ 2. Pinal County Rules Regulating Existing and New Non

‐ point Sources in Pinal County ................................................. 24

Table 4

‐ 3. Pinal County Rules Regulating Fugitive Dust in Pinal County Portion of MC PM10 NAA ............................................ 24



# vi

# vii 

# List of Appendices

Appendix A – 5-year Historical Fluctuation Grap hs for the Phoenix Nonattainment Area PM10 Sites

Appendix B – ADEQ Forecast Products for P hoenix, Maricopa County, and Pinal County

Appendix C – Notice of Public Comment Period

Appendix D – National Weather Servi ce Forecasts, Warnings, and Alerts

# I. EXCEPTIONAL EVENT RU LE (EER) REQUIREMENTS

In addition to the technical requirements that are c ontained within the EER, proc edural requirements must

be met in order for EPA to concur with the flagged ai r quality monitoring data. This section of the report

lays out the requirements of the EER and associated guidance, and disc usses how the Arizona Department

of Environmental Quality (ADEQ) addressed those requirements.

Procedural Requirements

This section presents a review of the procedur al requirements of the EER as required by 40 CFR 50.14

( Treatment of Air Quality Monitoring Data Influenced by Exceptional Events ) and explains how ADEQ

fulfills them. The Federal EER requirements include notifying the public that an event was occurring,

placing informational flags on data in EPA’s Air Qua lity System (AQS), notifying EPA of the intent to

flag through submission of initial event descriptio n, documenting that the public comment process was

followed, and submitting a demonstration supporting th e exceptional events flag. ADEQ has addressed

all of these procedural and documentation requirements.

Public notification that event was occurring (40 CFR 50.14(c)(1(i))

ADEQ issued Dust Control Action Forecasts and En semble Forecasts for the Greater Phoenix area

advising citizens of the potential for high wind / dust events every da y during the period of August 25 –

August 28, 2011. More information on ADEQ’s for ecasting program can be found in Section IV. The

forecast products that were issued during the period August 24 – 28, 2011, are included in Appendix B.

Place informational flag on data in AQS (40 CFR 50.14(c)(2)(ii))

ADEQ and other operating agencies in Arizona subm it da ta into EPA’s AQS. Data from both filter-based

and continuous monitors operated in Arizona are submitted to AQS.

When ADEQ and/or another agency operating monitors in Arizona suspect s that data may be influenced

by an exceptional event, ADEQ and/or the other opera ting agency expedites analysis of the filters

collected from the potentially affected filter-based ai r monitoring instruments, quality assures the results,

and submits the data into AQS. ADEQ and/or other operating agencies also submit data from continuous

monitors into AQS after quality assurance is complete.

If ADEQ and/or the operating agency have determined a potential exists that the monitor reading has been

influenced by an exceptional event, a preliminary fl ag is submitted for the measurement in the AQS. The

data are not official until they unde rgo more thorough quality assurance and quality control, leading to

certification by May 1 of the year following the ca lendar year in which the data were collected

(40 CFR 58.15(a)(2)). The presence of the flag can be confirmed in AQS.

Notify EPA of intent to flag through submission of in itial eve nt description by July 1 of calendar year

following event (40 CFR 50.14(c)(2)(iii))

ADEQ submitted notice to EPA on August 29, 2012, listing all days from calendar year 2011 that ADEQ

intended to analyze under the Exce ptional Events Rule and notifying the EPA of which PM10 data were

flagged in AQS. Exceedances that occurred on August 25, 26, 27, and 28, 2011, within the Phoenix

PM10 nonattainment area were included on that list. This report serv es as the demonstration supporting

the flagging of these data.

1

# On August 25, 2011, 13 monitors at 12 sites within the boundaries of the P hoenix PM10 nonattainm ent

area exceeded the 24-hour PM10 standard during the high wind event that occurred very early in the

morning. The PM10 monitors impact ed were the JLG Supersite TEOM 2 

# and BAM 3 

# operated by ADEQ

and the Buckeye, Central Phoenix, Durango Comp lex, Dysart, Glendale, Greenwood, South Phoenix,

West Chandler, West 43 rd 

# , West Phoenix, and Zuni Hills monitors operated by Maricopa County Air

Quality Department (MCAQD).

On August 26, 2011, one monitor—the Apache Junction m onitor located in Pinal County and operated by

Pinal County Air Quality Control Di strict (PCAQCD), but within th e boundaries of the Phoenix PM10

nonattainment area—exceeded the 24-hour PM10 sta ndard during the high wind event that occurred

during the afternoon/evening hours.

On August 27, 2011, nine monitors within the bounda ries of the Phoenix PM10 nonattainment area

exceeded the 24-hour PM10 standard dur ing the high wind event that occurre d late at night. The monitors

impacted were the Buckeye, Central Phoenix, Durango Complex, Glendale, Greenwood, South Phoenix,

West Chandler, West 43 rd 

# , and West Phoenix monitors operated by MCAQD.

On August 28, 2011, two monitors wi thin the boundaries of the Phoenix PM10 nonattainment area

exceeded the 24-hour PM10 standard during the high wind event that occurred very early in the morning.

The monitors impacted were the Higley monitor in Maricopa County and operated by MCAQD and the

Apache Junction monitor in Pinal County, but within the Phoenix PM10 nonattainment area, and operated

by the PCAQCD.

Document that the public comment proce ss was followed for event docu mentation (40 CFR

50.14(c)(3)(iv))

ADEQ posted this assessment report on the ADEQ webpage and placed a hardcopy of the report in the

ADEQ Records Management Center for public revi ew. ADEQ opened a 30-day public comment period

on December 3, 2012. A copy of the public notice certification, along with any comments received, will

be submitted to EPA, consistent with the requirements of 40 CFR 50.14(c)(3)(iv). See Appendix D for a

copy of the affidavit of public notice.

Submit demonstration supporting exceptional event flag (40 CFR 50.14(a)(1-2))

At the close of the comment period, and after ADEQ has had the opportunity to consider any com ments

submitted on this document, ADEQ will submit this document, the comments received, and ADEQ’s

responses to those comments to EPA Region IX headqua rters in San Francisco, California. The deadline

for the submittal of this demonstration package is September 30, 2014.

2 

# TEOM is an acronym for a Tapered Element Oscillating Monitoring system.

3 

# BAM is an acronym for a Beta Attenuation Monitoring System.



# 2

# Documentation Requirements

Se ction 50.14(c)(3)(iii) of the EER states that in order to jus tify excluding air quali ty monitoring data,

evidence must be provided for the following elements:

a. The event satisfies the criteria se t forth in 40 CFR 501(j) that:

(1) the event affected air quality,

(2) the event was not reasonably cont rollable or preventable, and

(3 ) the event was caused by human activity unlikely to recur in a particul ar location or was a

natural event;

b. There is a clear causal relations hip between the measurement under consideration an d the event;

c. The event is associated with a measured concentr ation in excess of normal historical fluctuations;

and

d. There would have been no exceedance or violation but for the event.

Section II of this assessment introdu ces the conceptual model of the thu nderstorm events that transpired

during August 25-28, 2011, providing a background narrative of the exceptional ev ents and an overall

explanation that “the event affected air quality.” Furt her evidence that ‘the event affected air quality’ is

provided in Section V. Sections II and V also provide evidence that the event was a natural event.

Section IV of this assessment details the existing area control measures and demonstrates that despite the

presence and enforcement of these controls, th e events of August 25-28, 2011 were not reasonably

controllable or preventable.

Section V of this assessment establishes a clear causal connection between the natural events of

August 25-28, 2011 and the exceedances of the 24-hour PM10 standard at the monitoring stations. The

evidence in this section (and the prev ious section on historical fluctuati ons) also confirms that the events

in question both affected air quality a nd were the result of natural events.

Section III of this assessment provides data summaries a nd time series graphs that help illustrate that the

events of August 25-28, 2011 produced PM 10 concentrations in excess of normal historical fluctuations.

Section VI of this assessment builds upon the demons tration showing a clear causal connection between

the natural event and the exceedances and concludes there would have been no exceedances during

August 25-28, 2011, but for the pres ence of the natural events.

3

# II. CONCEPTUAL MODEL

Geographic Setting and Climate

This section describes the geographic and climatic setting of the monitors.

Geographic Setting of Monitors

Phoenix is located in the Salt River Valley in south-central Arizona. It lies at a m ean elevation of 1,090

feet above mean sea level (msl) in the northeastern part of the Sonoran Desert. Other than the mountains

in and around the city, the topography of Phoenix is generally flat. The Phoe nix area is surrounded by the

McDowell Mountains (~4,200 ft msl) to the northeast, the foothills of the Bradshaw (~7,900 ft msl) and

Mazataal (~7,900 ft msl) ranges to th e north, the White Tank Mountains (~4,500 ft msl) to the west, the

Sierra Estrella (~4,450 ft msl) to the southwest, and the Superstition Mountains (~5,000 ft msl) far to the

east. Within the City are the Phoenix Mountains (~2,600 ft msl) and South Mountain (~2,600 ft msl).

Current development is pushing north, west, and sout h into Pinal County. Th e Phoenix metropolitan area

contains a fairly dense network of PM10 monitors th roughout the area, with a much less dense network of

monitors located throughout the rest of the state. Figure 2-1 show s the general geogr aphic setting of

Phoenix, as well as the locations of PM10 monitors thr oughout the state. It shoul d be noted that some of

the monitors shown in Figure 2-1 are filter-based mon itors; therefore, monitoring data from all locations

may be available only for select days (i.e., 1-in-6 run days).

4

# Figure 2-1. Phoenix Geographic Setting and PM10 Monito r Locations (source: EPA AQS DataMart,

NASA MODIS Satellite, Google Eart h). PM10 monitor locations ar e indicated by the white markers.

Figure 2-2 depicts the drainage system s or watersheds for the State of Arizona. Many of the rivers that

form Arizona’s drainage system are dry for most of th e year and, consequently, are sources of silt and fine

soils that become suspended and add to regional PM 10 loadings during high wind events. Much of this

alluvial matter and fine soil is deposited in the lo w lying areas of central a nd southern Arizona, with

larger depositional areas focused in and ar ound the confluences of dry river channels.

5

# Figure 2-2. Drainage System of Phoenix, Arizona.

6

# Climate

Phoenix has an arid climate, with very hot summers and temperate winters. The average summer high

temperature is among the hottest of any populated area in the United States. The temperature reaches or

exceeds 100oF an average of 110 days during the year and highs top 110oF an average of 18 days during

the year. Phoenix receives an average of 7.66 inches of rain per year.

Precipitation is sparse du ring the first part of the summer, but the influx of monsoonal moisture, which

generally begins in early July and lasts until mid-Se ptember, raises humidity levels and can cause heavy

localized precipitation and flooding. Although thundersto rms are possible at any time of the year, they

are most common during the monsoon season from July to mid-September as humid air is advected from

the Gulf of California, Gulf of Mexico, and large thunderstorm co mplexes from the Sierra Madre

Occidental Mountains in Me xico. This influx in moisture, combin ed with intense so lar heating, often

creates a very unstable environment that is ripe fo r thunderstorm development. These thunderstorms can

bring strong winds and blowing dust, large hail, and heavy rain. Dust storms associated with these

thunderstorms typically occur in the early part of th e monsoon season (July/August) before soaking rains

help keep soil particles bound to one another. However, depe nding on the amount of precipitation

received during the monsoon season, extremely hot temperatures act to dry out the surface quickly, and

dust storms can occur at any time. During the December through March period, winter storms moving

inland from the Pacific Ocean can produce signifi cant rains throughout Arizona. This December–March

time period, and July–August time period are typically the wettest parts of the year . Meanwhile, a distinct

dry season occurs during the period Ap ril through June for Phoenix and th e rest of Arizona. While these

weather patterns describe the general climatology for the Phoenix area over a long period of time,

Phoenix and the entire state of Arizona are also prone to a high degree of variability in these weather

patterns from year to year.

Figure 2-3. Phoenix Monthly Precipitati on (top) and Maximum Temper ature (bottom) Climatology

(source: National Weather Service)

7

# Monsoon Season Description and Event Summaries

The week of August 25-28, 2011, was characterized by frequent monsoonal thunderstorm activity

throughout Arizona. The North Amer ican Monsoon is a shift in wind patterns in the summer which

occurs as Mexico and the southwes t U.S. warm under intense solar he ating. As this happens, low level

moisture is transported primarily from the Gulf of California and eastern Paci fic Ocean into the southwestern U.S. The Gulf of California, a narrow body of water surrounded by mount ains, is particularly

important for low-level moisture tran sport into Arizona and Sonora. Mi d and upper level moisture is also

transported into the region, mainly from the Gulf of Mexico by easterly winds aloft. This combination

causes a distinct rainy season over large portions of western North Am erica, which develops rather

quickly and sometimes dramatically. Rainfall during the monsoon is not continuous and varies considerably, depending on a variety of factors. There are usua lly distinct “burst” periods of heavy rain during the

monsoon, and “break” periods with l ittle or no rain. Even during active monsoon periods, some areas can

go without receiving any significant precipitation while other nearby areas expe rience heavy rains and

flooding.

The thunderstorm activity in Arizona during the period of August 25-28 was active in and around the

desert areas of southern Arizona and northern Mexico. These thunde rstorms did not result in much

precipitation for the Phoenix area, but many of the st orms were severe in na ture and caused numerous

significant dust-carrying outflow boundaries that propagated into th e Phoenix area. Downdrafts

associated with heavy precipitation from thunders torms or from collapsing thunderstorms can end up

producing what are called downbursts, or sometimes more concentrated and severe microbursts, which

are rapidly descending bursts of air that come thr ough the thunderstorms. Th ese downward bursts of air

hit the ground and then disperse away from the st orms as areas of outflow. These outflow boundaries

from the thunderstorms can kick up large areas of dust, sometimes ca lled haboobs, and transport that dust

for long distances from the initia ting thunderstorms (see Figure 2-4).

The active monsoon period of Augus t 25-28 led to numerous thundersto rms and thunderstorm outflows

that produced blowing dust in many parts of Arizona, in cluding the Phoenix Metropo litan area. A total of

three separate windblown dust events produced 25 PM10 exceedances in the Phoenix PM10

nonattainment area during the four day span. The ev ents were primarily driven by outflows from large

areas of multiple thunderstorms producing wind gusts fr om one prominent direct ion. Dates experiencing

PM10 exceedances in Maricopa County during this time included August 25, 26, 27, and 28. Two

exceedances in Pinal County at the Apache Juncti on monitoring site on August 26 and 28 were also

included in the documentation because this monitor is located within the eastern boundary of the Phoenix

PM10 nonattainment area. The August 25 th 

# and August 27 th 

# -28 th 

# events were large-scale and widespread

dust events with mostly south-southeasterly and west erly winds, respectively, transporting dust into the

region. The event occurring on August 26 was smaller in scale, but was still related to thunderstorm

activity over southwestern Arizona producing sout hwesterly outflow boundary winds across Maricopa

and Pinal Counties and leading to PM10 exceedances at two sites on the eastern side of the Phoenix

PM10 nonattainment area. Further details on the events can be found in Section V.

8

# Figure 2-4. Cross-section of a thunderstorm creating an outflow boundary and haboob (Source: Desert

Meteorology. Thomas T. Warner. 2004.)

The nature of these monsoonal dust events is such that specific source areas are difficult to determine, as

outflow from thunderstorms can carry dust over vast distances encompassing many source areas. Because

of this, it is more appropriate to speak of general source regions fo r these monsoonal dust storms, which

typically are identified based upon the locations of the thunderstorms that are believed to have created the

dust generating and carrying outflow winds. A vast majority of the PM10 impacting the Phoenix area

from thunderstorm-driven high wind events during the period of August 25-28 orig inated outside of the

Phoenix PM10 nonattainment area. The contributing s ource regions to the dust events were somewhat

widespread, but the majority of the PM that was tran sported into Maricopa County likely came from areas

within Pinal County to the south and southeast of Maricopa County. Other potential s ource contributors

to the PM10 events were areas in northern Pima C ounty and southeastern and southern Maricopa County.

The exact origin of the PM sources is often difficult to determine due to the holes in the spatial coverage

of radar data and less dense monitoring networks in the general source area.

Another important factor that le d to these significant dust storms was the on-going drought across the

region. The most recent U.S. Drought Monitor placed the area between Tucson and Phoenix in D1

(Moderate) to D3 (Extreme) drought (see Figure 2-5). Rainfall sin ce the end of the summer of 2010

leading up to the August 25-28 dust events had b een 52% of normal (see the Drought Information

Statement in Appendix D). In areas to the south of Phoenix, the most common dust source region, rainfall

during the 2011 summer monsoon season (June 15 – Augus t 25) was only 11% of normal in the city of

Maricopa. For additional informa tion pertaining to the 2011 monsoon season in Arizona, a couple news

media web links are included below.

9

# 10 2011 Monsoon Season Summary and Review  http://bcove.me/krh3qk29

This video contains information about the m onsoon season, the formation of dust storms in

Arizona, and the uniqueness of the 2011 monsoon season.

2011 Monsoon Season Review 2  http://bcove.me/tc6otk0h

This video contains information about the 2011 monsoon season, focusing on the large

number of dust storms that occurred, and a discussion of why there were so many dust

storms in 2011.

The abnormally dry conditions that were in place dur ing the early part of the monsoon season (which

persisted throughout the duration of the monsoon season) resulted in a la rge fetch of soils that were

vulnerable to particulate suspension. The repeat ed thunderstorm outflow boundaries that affected

Maricopa and Pinal counties during the August 25-28 period resulted in very little rainfall throughout

south-central Arizona, but the high winds associated with the outfl ows did bring an almost daily

occurrence of moderate to extremel y high levels of particulate concen trations in the ambient air. A

timeline summarizing these events can be seen in Figure 2-6. This figure shows hourly PM10

concentrations during the 24 hours pr ior to the first even t, indicating very low PM10 concentrations

across the Phoenix region prior to the arrival of the thunderstorm outflows; PM10 concentrations during

the three events periods analyzed in this document; and the 24 hours after the events, once again showing

that without the impacts of the t hunderstorm outflows, PM10 concentratio ns at all sites in the Phoenix

PM10 nonattainment area during th e August 25-28, 2011 time period woul d have been well below the 24-

hour average PM10 exceedan ce threshold of 150 μg/m 3



# .

Following Figure 2-6 are a series of tables detailing the PM10 24-hour average concentrations, the daily

maximum hourly concentrations and the time at which they occurred, and the flag given to the data in

EPA’s AQS for all PM10 monitoring sites in Arizona and for each day during the four-day event period.

Conclusions

This Conceptual Model was created to provide a basic description of the general climate and weather

patterns that led to the active thunderstorm period from August 25-28 and produced frequent dust storms

and 25 PM10 exceedances in the Phoenix PM10 nonattainment area during the four-day episode. A more

detailed analysis of each windblown dust event is in cluded in Section V, wher e a demonstration of the

clear causal connection be tween the uncontrollable natural events and PM10 exceedances is presented.Figure 2-5.U.S. Drought Monitor analysisreleased during thetime period of the exceedances described in this report.11Timeline of Windblown Dust Eventsfor August 25, 2011 - August 28, 2011Figure 2-6.Timeline of PM10 concentrations at monitors throughout the Phoenix Metro area during the period of August 25-28, 201112

# August 25, 2011

Table 2-1. Summary of Statewide PM10 Measurements for August 25, 2011.

Monitor Monitor

Type Operator AQS Monitor ID 24-hr Avg

PM10

(μg/m 3 

# ) 1-hr Max

PM10

(μg/m 3 

# ) Max Time AQS

Qualifier

Flag

Apache County

N/A TEOM WMAT 04-001-1003-81102-1 10 27 1300

Cochise County

Douglas Red Cross FRM ADEQ 04-003-1005-81102-1 16 N/A N/A

Paul Spur Chemical

Lime Plant FRM ADEQ 04-003-0011-81102-1 9 N/A N/A

Paul Spur Chemical

Lime Plant FRM ADEQ 04-003-0011-81102-2 9 N/A N/A

Coconino County

Flagstaff Middle School FRM ADEQ 04-005-1008-81102-1 11 N/A N/A

N/A TEOM NN 04-005-1237-81102-1 17 46 0800

Gila County

Hayden Old Jail TEOM ADEQ 04-007-1001-81102-3 23 62 0000

Payson Well Site FRM ADEQ 04-007-0008-81102-1 7 N/A N/A

Payson Well Site FRM ADEQ 04-007-0008-81102-2 8 N/A N/A

Miami Ridgeline FEM FMMI 04-007-0009-81102-1 12 N/A N/A IT

Miami Golf Course FEM FMMI 04-007-8000-81102-1 16 N/A N/A IT

Miami Golf Course FEM FMMI 04-007-8000-81102-2 17 N/A N/A IT

Maricopa County

Buckeye TEOM MC 04-013-4011-81102-1 235 943 0300 RJ

Central Phoenix TEOM MC 04-013-3002-81102-4 308 2822 0200 RJ

Durango Complex TEOM MC 04-013-9812-81102-1 436 4240 0200 RJ

Dysart TEOM MC 04-013-4010-81102-1 273 2057 0300 RJ

Fort McDowell/Yuma

Frank TEOM FMIR 04-013-5100-8112-1 20 N/A N/A

Glendale TEOM MC 04-013-2001-81102-1 240 2477 0200 RJ

Greenwood TEOM MC 04-013-3010-81102-1 388 4104 0200 RJ

High School Air

Monitoring Station FRM SRP-MIC 04-013-7024-81102-1 90 N/A N/A

Higley TEOM MC 04-013-4006-81102-1 131 379 0700

JLG Supersite BAM ADEQ 04-013-9997-81102-3 173 985 0200 RJ, EH

JLG Supersite TEOM ADEQ 04-013-9997-81102-4 241 2785 0200 RJ

Lehi Air Monitoring

Station FRM SRP-MIC 04-013-7022-81102-1 58 N/A N/A

Mesa FRM MC 04-013-1003-81102-1 N/A N/A N/A

North Phoenix FRM MC 04-013-1004-81102-1 N/A N/A N/A

Senior Center Air

Monitoring Station FRM SRP-MIC 04-013-7020-81102-1 56 N/A N/A

Senior Center Air

Monitoring Station FRM SRP-MIC 04-013-7020-81102-2 63 N/A N/A

South Phoenix TEOM MC 04-013-4003-81102-1 420 3592 0200 RJ

South Scottsdale FRM MC 04-013-3003-81102-1 N/A N/A N/A

West Chandler TEOM MC 04-013-4004-81102-1 278 2116 0100 RJ

West Forty Third TEOM MC 04-013-4009-81102-1 369 2915 0200 RJ

West Phoenix TEOM MC 04-013-0019-81102-1 212 794 0300 RJ

Zuni Hills TEOM MC 04-013-4016-81102-1 212 1749 0300 RJ

Mohave County

Bullhead City ADEQ FRM ADEQ 04-015-1003-81102-1 26 N/A N/A

Navajo County

N/A TEOM WMAT 04-017-1002-81102-1 14 46 2000

Pima County

Ajo TEOM ADEQ 04-019-0001-81102-3 50 157 0100 IJ

Corona de Tucson FRM PCDEQ 04-019-0008-81102-1 9 N/A N/A

Geronimo BAM PCDEQ 04-019-1113-81102-1 16 36 2000

Green Valley BAM PCDEQ 04-019-1030-81102-1 11 35 1600



# 13

# Monitor Monitor

Type Operator AQS Monitor ID 24-hr Avg

PM10

(μg/m 3 

# ) 1-hr Max

PM10

(μg/m 3 

# ) Max Time AQS

Qualifier

Flag

Orange Grove FRM PCDEQ 04-019-0011-81102-2 15 N/A N/A

Prince Road FRM PCDEQ 04-019-1009-81102-1 19 N/A N/A

Rillito TEOM ADEQ 04-019-0020-81102-3 49 438 0000 IJ

Santa Clara FRM PCDEQ 04-019-1026-81102-1 15 N/A N/A

South Tucson FRM PCDEQ 04-019-1001-81102-1 15 N/A N/A

Tangerine FRM PCDEQ 04-019-1018-81102-1 15 N/A N/A

Pinal County

Apache Junction Fire Stn. FRM PCAQCD 04-021-3002-81102-1 23 N/A N/A

Apache Junction Fire Stn. TEOM PCAQCD 04-021-3002-81102-3 25 76 1000

Casa Grande Downtown TEOM PCAQCD 04-021-0001-81102-3 238 1774 0200 RJ

Coolidge FRM PCAQCD 04-021-3004-81102-1 42 N/A N/A

Combs School TEOM PCAQCD 04-021-3009-81102-3 60 395 0100

Cowtown FRM PCAQCD 04-021-3013-81102-1 828 N/A N/A RJ

Cowtown TEOM PCAQCD 04-021-3013-81102-3 1064 15056 0200 RJ

Eloy FRM PCAQCD 04-021-3014-81102-1 127 N/A N/A

Maricopa TEOM PCAQCD 04-021-3010-81102-3 529 3473 0200 RJ

Pinal Air Park N/A PCAQCD 04-021-3007-81102-1 48 N/A N/A

Pinal County Housing FRM PCAQCD 04-021-3011-81102-1 107 N/A N/A

Pinal County Housing FRM PCAQCD 04-021-3011-81102-2 131 N/A N/A

Pinal County Housing TEOM PCAQCD 04-021-3011-81102-3 184 993 0200 RJ

Stanfield TEOM PCAQCD 04-021-3008-81102-3 267 1660 0200 RJ

N/A FRM PCAQCD 04-021-7004-81102-1 171 N/A N/A RJ

N/A FRM PCAQCD 04-021-7004-81102-2 216 N/A N/A

Santa Cruz County

Nogales Post Office FRM ADEQ 04-023-0004-81102-1 21 N/A N/A

Nogales Post Office BAM ADEQ 04-023-0004-81102-3 30 97 2100

Yavapai County

Prescott Valley FRM ADEQ 04-025-2002-81102-1 9 N/A N/A

Yuma County

Yuma Supersite TEOM ADEQ 04-027-8011-81102-3 23 59 1800

Operator Abbreviations: MC – Marico pa County Air Quality Department

PCAQCD – Pinal County Ai r Quality Control District

ADEQ – Arizona Department of Environmental Quality

FMIR – Fort McDowell Indian Reservation

NN – Navajo Nation, AZ, NM, UT

PCDEQ – Pima County Department of Environmental Quality

SRP-MIC – Salt River Pima-Maricopa Indian Community of Salt River Reservation, AZ

WMAT – White Mountain Apache Tribe of Fort Apache Reservation, AZ



# 14

# August 26, 2011

Table 2-2. Summary of Statew ide Air Quality Measurements for August 26, 2011.

Monitor Monitor

Type Operator AQS Monitor ID 24-hr Avg

PM10

(μg/m 3 

# ) 1-hr Max

PM10

(μg/m 3 

# ) Max Time AQS

Qualifier

Flag

Apache County

N/A TEOM WMAT 04-001-1003-81102-1 15 29 1900

Coconino County

N/A TEOM NN 04-005-1237-81102-1 16 47 2000

Gila County

Hayden Old Jail TEOM ADEQ 04-007-1001-81102-3 36 167 1800 IJ

Maricopa County

Buckeye TEOM MC 04-013-4011-81102-1 44 262 1700

Central Phoenix TEOM MC 04-013-3002-81102-4 49 236 1800

Durango Complex TEOM MC 04-013-9812-81102-1 50 290 1700

Dysart TEOM MC 04-013-4010-81102-1 41 299 1700

Fort McDowell/Yuma

Frank TEOM FMIR 04-013-5100-8112-1 22 N/A N/A

Glendale TEOM MC 04-013-2001-81102-1 43 277 1800

Greenwood TEOM MC 04-013-3010-81102-1 45 237 1700

Higley TEOM MC 04-013-4006-81102-1 150 842 1800

JLG Supersite BAM ADEQ 04-013-9997-81102-3 38 142 1800

JLG Supersite TEOM ADEQ 04-013-9997-81102-4 39 203 1800 IJ

South Phoenix TEOM MC 04-013-4003-81102-1 51 210 1700

West Chandler TEOM MC 04-013-4004-81102-1 92 689 1700

West Forty Third TEOM MC 04-013-4009-81102-1 47 349 1700

West Phoenix TEOM MC 04-013-0019-81102-1 55 253 1700

Zuni Hills TEOM MC 04-013-4016-81102-1 38 331 1800

Navajo County

N/A TEOM WMAT 04-017-1002-81102-1 13 51 1600

Pima County

Ajo TEOM ADEQ 04-019-0001-81102-3 213 1224 2200 RJ

Geronimo BAM PCDEQ 04-019-1113-81102-1 29 156 1700

Green Valley BAM PCDEQ 04-019-1030-81102-1 17 112 1900

Orange Grove FRM PCDEQ 04-019-0011-81102-2 31 N/A N/A

Rillito TEOM ADEQ 04-019-0020-81102-3 68 295 1900 IJ

South Tucson FRM PCDEQ 04-019-1001-81102-1 29 N/A N/A

Pinal County

Apache Junction Fire Stn. TEOM PCAQCD 04-021-3002-81102-3 169 799 2000 RJ

Casa Grande Downtown TEOM PCAQCD 04-021-0001-81102-3 211 1947 1800 RJ

Combs School TEOM PCAQCD 04-021-3009-81102-3 206 1569 1400 RJ

Cowtown TEOM PCAQCD 04-021-3013-81102-3 248 1038 2000 RJ

Maricopa TEOM PCAQCD 04-021-3010-81102-3 108 1000 0000

Pinal County Housing TEOM PCAQCD 04-021-3011-81102-3 257 2792 1800 RJ

Stanfield TEOM PCAQCD 04-021-3008-81102-3 170 406 1800 RJ

Santa Cruz County

Nogales Post Office BAM ADEQ 04-023-0004-81102-3 31 74 0700

Yuma County

Yuma Supersite TEOM ADEQ 04-027-8011-81102-3 22 57 1900

Operator Abbreviations: MC – Marico pa County Air Quality Department

PCAQCD – Pinal County Ai r Quality Control District

ADEQ – Arizona Department of Environmental Quality



# FMIR – Fort McDowell Indian Reservation

PCDEQ – Pima County Departme nt of Environmental Quality

WMAT – White Mounta in Apache Tribe of Fort Apache Reservation, AZ



# 15

# August 27, 2011

Table 2-3. Summary of Statew ide Air Quality Measurements for August 27, 2011.

Monitor Monitor

Type Operator AQS Monitor ID 24-hr Avg

PM10

(μg/m 3 

# ) 1-hr Max

PM10

(μg/m 3 

# ) Max Time AQS

Qualifier

Flag

Apache County

N/A TEOM WMAT 04-001-1003-81102-1 18 40 0600

Coconino County

N/A TEOM NN 04-005-1237-81102-1 25 87 2000

Gila County

Hayden Old Jail TEOM ADEQ 04-007-1001-81102-3 60 123 0000

Maricopa County

Buckeye TEOM MC 04-013-4011-81102-1 225 3219 2100 RJ

Central Phoenix TEOM MC 04-013-3002-81102-4 233 1972 2300 RJ

Durango Complex TEOM MC 04-013-9812-81102-1 261 3169 2200 RJ

Dysart TEOM MC 04-013-4010-81102-1 126 1514 2200

Fort McDowell/Yuma

Frank TEOM FMIR 04-013-5100-8112-1 28 N/A N/A

Glendale TEOM MC 04-013-2001-81102-1 219 2908 2200 RJ

Greenwood TEOM MC 04-013-3010-81102-1 207 2064 2200 RJ

Higley TEOM MC 04-013-4006-81102-1 115 712 2300

JLG Supersite BAM ADEQ 04-013-9997-81102-3 127 883 2300 IJ, EH

JLG Supersite TEOM ADEQ 04-013-9997-81102-4 132 1220 2300 IJ

South Phoenix TEOM MC 04-013-4003-81102-1 301 2795 2200 RJ

West Chandler TEOM MC 04-013-4004-81102-1 228 2407 2300 RJ

West Forty Third TEOM MC 04-013-4009-81102-1 292 3633 2200 RJ

West Phoenix TEOM MC 04-013-0019-81102-1 164 1519 2200 RJ

Zuni Hills TEOM MC 04-013-4016-81102-1 112 1308 2300

Navajo County

N/A TEOM WMAT 04-017-1002-81102-1 15 51 1200

Pima County

Ajo TEOM ADEQ 04-019-0001-81102-3 167 400 0000 RJ

Geronimo BAM PCDEQ 04-019-1113-81102-1 52 451 2100

Green Valley BAM PCDEQ 04-019-1030-81102-1 21 51 2300

Orange Grove FRM PCDEQ 04-019-0011-81102-2 51 N/A N/A

Rillito TEOM ADEQ 04-019-0020-81102-3 84 348 1500 IJ

South Tucson FRM PCDEQ 04-019-1001-81102-1 30 N/A N/A

Pinal County

Apache Junction Fire Stn. TEOM PCAQCD 04-021-3002-81102-3 84 424 0000

Casa Grande Downtown TEOM PCAQCD 04-021-0001-81102-3 123 441 2000

Combs School TEOM PCAQCD 04-021-3009-81102-3 157 1242 1900 RJ

Cowtown TEOM PCAQCD 04-021-3013-81102-3 381 2192 2000 RJ

Maricopa TEOM PCAQCD 04-021-3010-81102-3 267 1385 2000 RJ

Pinal County Housing TEOM PCAQCD 04-021-3011-81102-3 187 1479 2000 RJ

Stanfield TEOM PCAQCD 04-021-3008-81102-3 126 531 2000

Santa Cruz County

Nogales Post Office BAM ADEQ 04-023-0004-81102-3 36 67 2100

Yuma County

Yuma Supersite TEOM ADEQ 04-027-8011-81102-3 48 164 1800

Operator Abbreviations: MC – Marico pa County Air Quality Department

PCAQCD – Pinal County Ai r Quality Control District

ADEQ – Arizona Department of Environmental Quality



# FMIR – Fort McDowell Indian Reservation

PCDEQ – Pima County Department of Environmental Quality

WMAT – White Mountain Apache Tribe of Fort Apache Reservation, AZ

*Power failure and/or instrumentation range limitation occurred during expected maximum

concentration hour(s), likely resulting in an underestimate of 24-hour average



# 16

# August 28, 2011

Table 2-4. Summary of Statewide Air Quality Measurements for August 28, 2011.

Monitor Monitor

Type Operator AQS Monitor ID 24-hr Avg

PM10

(μg/m 3 

# ) 1-hr Max

PM10

(μg/m 3 

# ) Max Time AQS

Qualifier

Flag

Apache County

N/A TEOM WMAT 04-001-1003-81102-1 21 83 1700

Coconino County

N/A TEOM NN 04-005-1237-81102-1 20 58 1900

Gila County

Hayden Old Jail TEOM ADEQ 04-007-1001-81102-3 82 223 1000 IJ

Maricopa County

Buckeye TEOM MC 04-013-4011-81102-1 44 87 0000

Central Phoenix TEOM MC 04-013-3002-81102-4 79 192 0400

Durango Complex TEOM MC 04-013-9812-81102-1 61 134 0300

Dysart TEOM MC 04-013-4010-81102-1 55 179 0000

Fort McDowell/Yuma

Frank TEOM FMIR 04-013-5100-8112-1 305 N/A N/A

Glendale TEOM MC 04-013-2001-81102-1 67 227 0000

Greenwood TEOM MC 04-013-3010-81102-1 58 132 0300

Higley TEOM MC 04-013-4006-81102-1 175 1716 0000 RJ

JLG Supersite BAM ADEQ 04-013-9997-81102-3 77 180 0300 IJ

JLG Supersite TEOM ADEQ 04-013-9997-81102-4 72 201 0100 IJ

South Phoenix TEOM MC 04-013-4003-81102-1 71 145 0000

West Chandler TEOM MC 04-013-4004-81102-1 123 1107 0000

West Forty Third TEOM MC 04-013-4009-81102-1 58 160 0000

West Phoenix TEOM MC 04-013-0019-81102-1 71 170 0300

Zuni Hills TEOM MC 04-013-4016-81102-1 62 183 0200

Navajo County

N/A TEOM WMAT 04-017-1002-81102-1 13 37 2000

Pima County

Ajo TEOM ADEQ 04-019-0001-81102-3 25 57 0000 VB

Geronimo BAM PCDEQ 04-019-1113-81102-1 85 130 1400

Green Valley BAM PCDEQ 04-019-1030-81102-1 70 131 1000

Orange Grove FRM PCDEQ 04-019-0011-81102-2 89 N/A N/A

Rillito TEOM ADEQ 04-019-0020-81102-3 121 207 1000 IJ

South Tucson FRM PCDEQ 04-019-1001-81102-1 86 N/A N/A

Pinal County

Apache Junction Fire Stn. TEOM PCAQCD 04-021-3002-81102-3 283 767 0200 RJ

Casa Grande Downtown TEOM PCAQCD 04-021-0001-81102-3 216 625 0200 RJ

Combs School TEOM PCAQCD 04-021-3009-81102-3 165 801 0100 RJ

Cowtown TEOM PCAQCD 04-021-3013-81102-3 183 738 0200 RJ

Maricopa TEOM PCAQCD 04-021-3010-81102-3 119 793 0000

Pinal County Housing TEOM PCAQCD 04-021-3011-81102-3 177 564 0400 RJ

Stanfield TEOM PCAQCD 04-021-3008-81102-3 97 542 0200

Santa Cruz County

Nogales Post Office BAM ADEQ 04-023-0004-81102-3 65 141 1900

Yuma County

Yuma Supersite TEOM ADEQ 04-027-8011-81102-3 178 825 0600 RJ

Operator Abbreviations: MC – Marico pa County Air Quality Department

PCAQCD – Pinal County Ai r Quality Control District

ADEQ – Arizona Department of Environmental Quality

FMIR – Fort McDowell Indian Reservation

PCDEQ – Pima County Depart ment of Environmental Quality



# WMAT – White Mountain Apache Tribe of Fort Apache Reservation, AZ



# 17

# III. HISTORICAL FLUCTUATIONS

The PM10 concentrations measured throughout Ma ricopa County during the period August 25-28, 2011,

were some of the highest hourly and 24-hour averages measured over the last five years. Time series

plots of the 24-hour PM10 concentrations for the period January 1, 2007, through December 31, 2011,

were created for all PM10 monitors in Maricopa C ounty. Additionally, time se ries plots of the daily

maximum hourly average PM10 concentrations were created for two monitors in Maricopa County.

These two additional plots were created to provide a deeper understanding of the magnitude of short-term

particulate concentrations and their contri bution to PM10 exceedances in the Phoenix PM10

nonattainment area. Time series plots for two monito ring sites (Higley and Cent ral Phoenix) are included

within this section, while the remaining plots are av ailable in Appendix A. Th e Central Phoenix monitor

was selected because of its central location in relation to all monitors in Maricopa County and the Higley

monitor was selected because it is representative of southeastern Ma ricopa County, an area of the region

frequently impacted by dust storms caused by thundersto rm outflow events. The graphs below and in

Appendix A show that the August 25th event was the most extreme event of the last five years for several

sites and that the other events during the August 25-28 period were also significan t compared to previous

data.

Figure 3-1. Plot of daily hourly m aximum PM10 concentr ations (2007 – 2011) at the Central Phoenix

monitoring site.

18

# The plot above shows the daily m aximum hourly averages from the Central Phoenix PM10 monitor. The

plot shows that the August 25th hourly average of 2822 μ g/m 3 

# and August 27 th 

# hourly average of

1972 μ g/m 3 

# were among the highest hourly PM10 concentrations recorded in th e last five years. The plot

also shows that the maximum hourly averages were co mparable to those observe d during the July 3 and 5,

2011 haboob events recently concurred upon by the EPA. The hourly average concentrations from these

two events were surpassed by additional dust storms that occurred a week ear lier in August and in

September, another indication of the uniqueness of the 2011 monsoon season. It is also clear that the

most significant hourly average PM10 concentrations at the Central Phoenix monitor typically occur

during the July through September time frame, a pe riod during which the mons oon season is most active

and the Phoenix region is frequently impacted by ha boob events. The plot below shows the daily 24-hour

averages from the Central Phoenix PM10 monitor and indicates that the August 25th event produced the

highest 24-hour average PM10 conc entration measured in the last five years and the August 27 th 

# event

was the fifth-highest during the same time period. Th ese events experienced concentrations similar to

haboob events that occurred on July 19, 2007, and in the first week of July 2011.

Figure 3-2. Plot of 24-hour average PM10 concentrati ons (2007 – 2011) at the Central Phoenix

monitoring site.

The two plots below provide a hist orical look at the daily m aximum hourly averages and daily 24-hour

averaged PM10 concentrations from the Higley monito r. The plots also show that the maximum hourly

concentration and exceedance measured at the Higley monitor on August 28 th 

# were amongst the 12

19

# highest PM10 concentrations m easured over the last five years. As was the case for the Central Phoenix,

the most significant hourly average PM10 concentrations at the Higley monitor typically occur during the

July through September time frame, a period duri ng which the monsoon season is most active and the

Phoenix region is frequently impacted by haboob events.

Figure 3-3. Plot of daily hourly m aximum PM10 concentr ations (2007 – 2011) at the Higley monitoring

site.

20

# Figure 3-4. Plot of 24-hour average PM10 concentrations (2007 – 2011) at the Higley monitoring site.

The plots within this section provi de a historical perspective of PM 10 concentrations since 2007. These

plots, along with those in Appendix A, show th at the haboob events which occurred during the

August 25 th 

# -28 th 

# period resulted in some of the highest PM10 concentrations seen in the last five years. In

the case of the Central Phoenix, Greenwood, West 43 rd 

# , South Phoenix, Durango, Glendale, and Dysart

monitoring sites, the highest 24-hour averaged PM10 c oncentrations measured in the last five years

occurred on August 25. While the August 25 th 

# event contained the greatest PM10 concentrations, the

other events in the August 25 th 

# -28 th 

# period were generally among the top 12 events in the last five years.

This equates to PM10 concentrations in the 99.3 th 

# percentile when compared to historic data. While the

PM10 concentrations that were measured during the August 25 th 

# -28 th 

# period were extreme in many cases,

the plots also show that similar events are not uncommon during the monsoon season. As documented in

several published journals and academic text books, haboobs generated fro m thunderstorm outflow

boundaries are phenomena that Arizonans deal with ever y year, some years more so than others, namely

in 2007 and 2011.

21

# IV. NOT REASONABLY CONT ROLLABLE OR PREVENTABLE

Section 50.1(j) of Title 40 CFR Part 50 requires that an event must be “not reasonably controllable or

preventable” in order to be define d as an exceptional event. This requirement is met by demonstrating

that despite reasonable control measures in pl ace within Maricopa County and the Phoenix PM10

nonattainment area, high wind conditions overwhelmed all reasonably available controls. The events

occurring from August 25-28 were dire ctly related to strong and gusty winds generated by thunderstorm

outflow boundaries. The strong winds overwhelmed a ll reasonably available co ntrols, and were also

responsible for transporting PM into the Phoenix PM10 nonattainment area from areas outside of the

nonattainment area. As explained in the conceptu al model, downdrafts from collapsing thunderstorms

produce outflow boundaries that contai n gusty, turbulent wakes that rais e dust from the desert surfaces

that can be as wide as 100 miles in severe cases. As shown in Section V, the source region for all of the

dominant thunderstorm outflows a nd associated transported dust dur ing the period of August 25-28, 2011,

generally came from areas outside of the Phoeni x PM10 nonattainment area—primarily from the deserts

of Pinal, Pima, and southern Marico pa counties. While it is likely th at some dust was generated within

the PM10 nonattainment area as gusts from the thunde rstorm outflows passed through the area, the

amount of dust generated locally was easily overwhe lmed by, and largely unnoticeable as compared to,

the dust transported in from the s ource regions of the thunderstorm outfl ows. Strict controls on local

sources of fugitive dust were in place and enforced during all of the events of August 25-28, 2011, but

were not capable of controlling tr ansported dust and PM10 raised by th e gusty and turbulent thunderstorm

outflows on these dates.

The following sections describe the BACM- and MSM- level PM10 control measures in place during the

period of August 25-28, 2011, and the robustness of the programs designed to enforce these measures.

Pro-active response and analysis of each event as it is occurring verify the uncontrollable nature of each

event, while inspections of local sources performe d before, during, and after the events of August 25-28,

2011, confirmed that no unusual anthropogenic PM10-produc ing activities occurred in Maricopa County,

the Phoenix PM10 nonattainment area, or the local areas surrounding the exceeding monitors.

Regulatory Measures and Control Programs

ADEQ) and MCAQD are responsible for implementing regulatory measures to control emissions from

agricultural sources, stationary sources, fugitive dus t sources, and open burning within Maricopa County.

Three major programs provide or contribute to air pollution control measures for the Greater Phoenix

area:

1) ADEQ’s Agricultural Best Management Program (AgBMP)

2) Maricopa County’s Inspecti on and Compliance Program

3) ADEQ’s Air Quality Forecasting Program

Specifically, ADEQ is responsible for compliance assi stance and enforcement of Agricultural Best

Management Practices developed by the Governor’s Ag ricultural Best Management Practices Committee,

while MCAQD is responsible for compliance assura nce for all other significant sources of PM10

emissions. In addition to routine inspections and in spections driven by complaints, inspections are often

increased when (1) ADEQ forecasters issue a High Risk for the Maricopa County Dust Control Forecast,

(2) ADEQ forecasters issue a High Pollution Advisory, or (3) near-real time monitoring data indicate

unique activity via high PM concentrations. Th e forecasting program a nd inspection/compliance

programs work together so that reso urces can be best utili zed during days that are of greatest risk for

elevated PM emissions.

22

# On July 25, 2002, EPA took initial action to finalize approval of the Best Av ailable Control Measure

(BACM) and the Most S tringent Measure (MSM) demons trations in the Serious Area PM10 plan for the

Maricopa County portion of the metropolitan Phoe nix PM10 nonattainment area (67 FR 48718). These

BACM and MSM demonstrations were again ap proved by EPA on July 14, 2006 (71 FR 43979). The

Agricultural Best Management Practices General Perm it rule and related definitions have been approved

into the Arizona Administrative Co de as R18-2-610 and R18-2-611 pursu ant to Arizona Revised Statutes

§ 49-457 4 

# . Maricopa County regulations of PM10 emissions are listed in Table 4-1.

Table 4-1. Rules and Ordinances Regulating Pa rticulate Matter Emissions in Maricopa County

Rule/Ordinance Number & Title Description

Rule 300: Visible Emissions Establishes standa rds for visible emissions and opacity.

Rule 310: Fugitive Dust from

Dust-Generating Operations Establishes limits for the emissions of particulate matter into the

ambient air from any property, operations, or activity that may

serve as a fugitive dust source

Rule 310.01: Fugitive Dust from

Non-Traditional Sources of

Fugitive Dust Establishes limits for the emissions of particulate matter into the

ambient air from open areas, vacant lots, unpaved parking lots,

and unpaved roadways which are not regulated by Rule 310 and

which are not required to have either a permit or a dust control

plan

Rule 311: Particulate Matter from

Process Industries Establishes emission rates based on process weight applicable to

any affected operations not subject to Rule 316.

Rule 312: Abrasive Blasting Establishes limits fo r particulate emissions from abrasive

blasting operations

Rule 314: Open Outdoor Fires and

Indoor Fireplaces at Commercial

and Institutional Establishments Establishes limits for the emissions of air contaminants

produced from open burning

Rule 316: Nonmetallic Mineral

Processing Establishes limits for the emissions of particulate matter into the

ambient air from any nonmetallic mining operation or rock

product processing plant

Rule 317: Hospital/Medical/

Infectious Waste Incinerators Establishes limits for the emi ssions of air pollutants from

medical waste incinerators

Rule 322: Power Plant Operations Establishes limits for the emissions of nitrogen oxides, sulfur

oxides, carbon monoxide and par ticulate matter from existing

power plants and cogeneration plants

Rule 323: Fuel Burning

Equipment from

Industrial/Commercial/

Institutional (ICI) Sources Establishes limits for the emissi ons of nitrogen oxides, sulfur

oxides, carbon monoxide and pa rticulate matter from ICI

sources

Rule 324: Stationary Internal

Combustion (IC) Engines Establishes limits for the emissions of carbon monoxide,

nitrogen oxides, sulfur oxides , volatile organic compounds, and

particulate matter from stationary internal combustion engines,

including stationary IC e ngines used in cogeneration

4 

# Updates to the AgBMP program in Decem ber, 2011, clarified BMPs for crop and added BMPs for animal operations.

Effective 12/29/2011, R18-2-611 was renumbered to R18-2-610.01 Agricultural PM10 Gen eral Permit for Crop

Operations and R18-2-611.01 Animal Operations PM10 General Permit was added. Definitions for Crop Operations were

revised at R18-2-610 and new definitions for Animal Operations were added at R18-2-611.



# 23

# Rule/Ordinance Number & Title Description

Rule 325: Brick and Structural

Clay Products (BSCP)

Manufacturing Establishes limits for particulate matter emissions from the use

of tunnel kilns for curing in the brick and structural clay product

(BSCP) manufacturing processes

Ordinance P-25: Leaf Blower

Restriction Establishes restrictions for leaf blowers in incorporated and

unincorporated sections of Area A in Maricopa County

Ordinance P-26: Residential

Woodburning Restriction Establishes restrictions for residential woodburning

Ordinance P-27: Vehicle Parking

and Use on Unstabilized Vacant

Lots Establishes restrictions fo r vehicle parking and use on

unstabilized vacant lots in unincor porated sections of Area A in

Maricopa County

Ordinance P-28: Off-Road

Vehicle Use in Unincorporated

Areas of Maricopa County Establishes restrictions fo r operating vehicles on unpaved

property in unincorporated areas of Maricopa County

Arizona Administrative Code

R18-2-611 & 610: Agricultural

PM10 General permit Establishes a requirement for co mmercial farmers to implement

best management practices and maintain a record demonstrating

compliance

In addition to the rules and regula tions listed in the above table, ot her PM10 reducing control measures

(e.g., paving of unpaved roads, PM10 certified str eet sweepers, controlling unpaved parking lots, etc.)

have been committed to, and implemented by, local jurisdictions throughout the PM10 nonattainment

area, and incorporated into the Arizona SIP thro ugh PM10 plans such as th e Revised MAG 1999 Serious

Area Particulate Plan for PM10 for the Maricopa County Nonattainment Area. The Pinal County Air

Quality Control District (PCAQCD) also implements regulatory control measures on emissions from

existing and new non-point sources within Pinal C ounty (see Table 4-2). Additionally, the PCAQCD

implements specific nonattainment rules for that part of the Phoenix PM10 nonattainment area that resides

in Pinal County (see Table 4-3).

Table 4-2. Pinal County Rules Regulating Existi ng and New Non-point Sources in Pinal County

Article Number & Title Description

Chapter 4, Article 2: Fugitive

Dust Provides a mechanism to reasona bly regulate operations which

periodically may cause fugitive dust emissions into the

atmosphere

Chapter 4, Article 3:

Construction Sites – Fugitive Dust Improves the control of excessive fugitive dust emissions that

have been traditionally associated with construction, earthwork,

and land development, and thereby minimize nuisance impacts

Table 4-3. Pinal County Rules Regulating Fugitive Dust in Pinal County Portion of MC PM10 NAA

Article Number & Title Description

Chapter 4, Article 4:

Nonattainment Area Rules;

Dustproofing for Commercial

Parking, Drives and Yards Establishes rules to avoid viol ations of the prevailing PM10

standard and addi tionally minimize nuisance impacts by

improving control of excessive fugitive dust emissions from

unpaved parking lots

Chapter 4, Article 5:

Nonattainment Area Rules;

Stabilization for Residential

Parking and Drives Establishes rules for stabilizing residential properties

24

# Article Number & Title Description

Chapter 4, Article 6: Restrictions

on Vehicle Parking and Use on

Vacant Lots Establishes rules for unpaved or unstabilized vacant lots (valid

in Pinal County portion of Area A)

Chapter 4, Article 7:

Construction Sites in

Nonattainment Areas – Fugitive

Dust Establishes rules to avoid viol ations of the prevailing PM10

standard and addi tionally minimize nuisance impacts by

improving control of excessive fugitive dust emissions from

activities associated with construction, earthwork, or land

development

Chapter 4, Article 8:

Nonattainment Area Rules,

Requirement for Stabilization of

Disturbed Areas at Vacant Lots Establishes rules for stabilizing disturbed areas at vacant lots

PM10 Rule Effectiveness

MCAQD analyzed the effectivenes s of its fugitive dust rules (Rul es 310, 310.01 and 316) in terms of

permit compliance rates. This ru le effectiveness (RE) study was de signed to assess how many sources

regulated by MCAQD during the subj ect time period received no PM10 emi ssions-related violations. As

a basis for comparison, the percentage of permitted s ources in compliance during calendar year 2007 was

76% for sources subject to Rule 310, 85% for Rule 310.01 sources, and 40% for Rule 316 sources. In

early 2008, Rules 310, 310.01, and 316 were strengthene d, and new ordinances (covering additional

source categories such as leaf blowers, vacant lots, and off-road vehicles) were adopted. These

enhancements resulted from MCAQD department’s obligations under such agreements as the 2005

Revised PM10 State Implementation Plan for the Sa lt River Area and the Maricopa Association of

Governments (MAG) 2007 Five Percent Plan for PM10 for the Maricopa County Nonattainment Area to

reduce PM10 emissions throughout the county. Thr ee major areas that contributed to increased

compliance were an increase in departmental staffing (especially inspectors), a robust training program,

and regulatory changes that broa dened and strengthened control measures under Rules 310, 310.01, and

316.

Source compliance rates were re-assessed for FY 2009 (July 2008–June 2009), a period that allowed time

for the new and revised regulations to take effect. The results showed significant increases in compliance

compared with the earlier period : to 90% (from 76%) for Rule 310 sources, to 95% compliance (from

85%) for Rule 310.01 sources, and to 65% (from 40 %) for Rule 316 sources. These improvements

continued into calendar year 2010 with compliance rates of 94% fo r Rule 310 sources, 96% for Rule

310.01, and 73% for Rule 316 sources. The timeline belo w illustrates the improvements in RE over the

last several years, and also points out significant revisions to previous rules, as well as newly adopted

rules and ordinances.

25

# 0 1 / 27

/ 2 01

0

Rules 3 1 0 &

3 10.

0 1

R ev i s ed 0 1 / 1 2/

2 011

O rdinances

P ‐ 27

&

P

‐ 28

Revised 06/01/2005

06/08/20 0 5

Rule 3 1 6 Rev

is ed

04/

0 7/2004

R u le

3 10

Revised

0 2 /1

7 / 2 005

Rul

e 31

0 .01

Revised

0 3/26/200 8

R u les

31

0 &

3 10

.0 1 Revised

M arc h 20 08 S e p tem b er 200 6



# 0 2/

2 0/20 08

O rdina n ces

P ‐ 25,

P

‐ 27

&

P ‐ 2 8

Adopted

0 3/12/20 0 8

R u le

3 16

Revised



# Figure 4-1. Timeline of Maricopa County Fugitive Dust Rules and Ordinances.

Compliance and Enforcement Activities

MCAQD is proactively prepared to respond to high wind events and to protect human health and wellbeing. MCAQD’s approach consists of two primary co mponents: routine proactive inspections, as well

as surveillance inspections, conducted both during a nd after significant events. MCAQD proactively

inspects dust control-permitted sites, and increases the frequency for larger sites of 10 acres or more.

Rule 316 sources are also proactively inspected mu ltiple times every year. Maricopa County also

responds to the majority of complaints within 24 hours.

Maricopa County monitors the ADEQ Five-Day Dust Control Forecast to iden tify the potential for

elevated PM10 pollution levels due to high winds or stagnant c onditions. When a High Pollution

Advisory (HPA) is issued for Maricopa County, MC AQD conducts additional surveillance before, during,

and after the forecast event(s). MCAQD also conduc ts event surveillance a nd post-event activities on

exceedance days that had not been forecast (i.e., thos e instances in which an HPA had not been issued).

Pre-event surveillance consists of surveying high-risk areas for any dust generating activ ities; educating

sources of the impending HPA event; a nd issuing violations for failure to comply with local, state, or

federal regulations. During the event, MCAQD inspector s survey high-risk areas to confirm that control

measures are in place, document any violations, and contact other regulatory agen cies if necessary. Postevent activities include continued surv eys of high-risk areas, re-inspect ion of sources that had received

violations within two business days, and an internal MCAQD debriefing of event activities.

Recently, a total of 12 MCAQD air monitoring sites have been updated with new equipment that allows

the monitoring sites to report automatically monitored re adings at five-minute intervals, where previously

only hourly data were available. The real-time monitoring data progr amming includes threshold triggers

that cause the system to send al erts to MCAQD staff that the PM concentrations are elevated. The system

allows MC AQD responders to review concentrations at the monitor and to cons ult the National Weather

Service website to check for weathe r event activity. This capability allows the responder to identify

regional events and monitor specifi c issues. If necessary, the MC AQD responders can inform nearby

stakeholders and local governments of the elevated PM10 concentrations.

26

# For August 25th and 28th, Maricop a County Dust Contro l Forecasts were issued indicating a moderate

risk level for unhealthy PM10. On August 26th, a Ma ricopa County Dust Control Forecast was issued

indicating a high risk level for unheal thy PM10. The Dust Control Forecast s also indicated a potential for

blowing dust. For the events from August 25-28, 2011, included in this analysis, MCAQD responders

evaluated each situation when conc entrations were elevated. During most of the alerts MCAQD observed

weather system activity and noted that many monitors were simultaneously impacted by the high winds.

In instances where strong winds were not present, or only a single monitor was affected, MCAQD issued

broadcast alerts to nearby stakeholders and loca l governments, and also deployed MCAQD inspectors to

investigate possible causes of the elevated readings.

An evaluation of inspection reports and comp liance records indicate no evidence of unusual

anthropogenic-based PM10 emissions. During th e time period of August 22 through August 31, 2011,

MCAQD inspectors conducted a tota l of 197 inspections on permitted f acilities, of which 142 were at

fugitive dust sources. Additionally, MCAQD conduc ted 114 inspections on vacant lots and unpaved

parking lots.

During this 10-day period, a total of 21 violations were issued county-wide for PM10- and non-PM10-

related violations. Only two violatio ns were issued for PM10 emissions at a single source within 4 miles

of the exceeding West Chandler monitor. On A ugust 25, 2011, two violations were issued to an

earthmoving site: for failure to stabilize surface areas using one of the standards in Rule 310, Section

304.3, and for failure to implement control measures on unpaved staging areas, unp aved parking areas and

unpaved storage areas. The total unst abilized area was small and measured 0.21 acres. The site operators

stabilized the area after the in spector notified the general c ontractor of the violations.

MCAQD was prepared for any complaints received due to the high wind events. MCAQD received 57

complaints, of which 33 were windblown dust-re lated between August 22 and August 31. Each

complaint was assigned to and investigated by a MCAQ D inspector. A review of all records during this

period reveals that MCAQD inspectors observed one violation of local, st ate, or federal regulations for

control of PM10 within 4 miles of an exceeding monitor during their investigations. On August 31, 2011,

MCAQD received a dust complaint concerning an ear thmoving source within 4 miles of the Central

Phoenix Monitor. On September 1, 2011, an inspector investigated the compliant and issued a violation

for failure to maintain complete re cords. The source only kept records of the amount of water applied but

did not maintain subcontractor registration numbers or maintenance of trackout control devices. The

Central Phoenix Monitor previously exceeded on August 27, 2011.

In addition to MCAQD’s efforts in pre-event surveillance and proact ive inspections, ADEQ’s

Agricultural Best Management Practice Program (Ag BMP) inspector monitors the ADEQ Five-Day Dust

Control Forecast and the MCAQD air monitoring sites that include real-time data. The ADEQ Ag BMP

inspector uses specific knowledge of seasonal activities and associa tions with the local growers and

dairymen to communicate the importance of limiting dust-generating activities, especially during highwind events. Additional outreach is conducted with facility representati ves prior to for ecasted high-wind

alert days. Should the PM10 readings at a MCAQD ai r monitoring site show notable increases, the

ADEQ Ag BMP inspector is dispatched to contact the owners and operators of ag riculture fields in the

area to discern if their activities ar e causing negative impacts. The Ag BMP inspector is prepared to

respond to most agriculture complaints within 24 hours.

Based on a review of the inspection reports and site visit documentation, there is no evidence to suggest

that agricultural activities produced unusual PM10 emissions. From August 22 through August 26, 2011,

the ADEQ Ag BMP inspector received five complain ts, performed site visits at three agricultural

27

# operations, and conducted outreach via telephone with se veral facility representa tives. The agriculture

fields visited were undergoing norm al agricultural practice.

Conclusions

The thunderstorm outflow events of August 25-28, 2011 produced strong gusts and turbulent wakes that

transported dust and PM10 into the Phoenix PM10 nona ttainment area. The sour ce region of the outflows

that caused the exceedances was largely located in areas outside the Phoenix PM10 nonattainment area,

primarily the deserts of Pinal, Pima, and southern Maricopa County. The Phoenix area is designated as a

serious nonattainment area for PM10 and is required to have BACM for all si gnificant sources of PM10.

BACM-approved control measures on significant anthropogenic sources were in place and enforced

during the events, and pro-active tr acking and response to the events by regulatory agencies and local

governments confirmed the uncontrollabl e nature of the dust emissions; th erefore, these pr e-existing/prior

approved required controls are adequate for meeting th e requirements of an ex ceptional event and should

be considered “reasonable” for these purposes.

Despite the deployment of comprehensive control m easures and sophisticated response programs and a

few localized, low-impact violati ons of the dust control rules, hi gh wind conditions associated with

thunderstorms and thunderstorm outflows brought high concentrations of PM10 emissions into, and also

overwhelmed controls within, th e Phoenix PM10 nonattainment area. Numerous strong thunderstorm

outflows with sustained winds t ypically ranging from 20-30 mph, and even greater n earest the source

regions, were enough to overwhelm all available efforts to limit PM10 c oncentrations from the events.

The fact that these were natura l events involving strong thunderstorm outflow wi nds that transported

PM10 emissions into Maricopa County, with a majo rity of the PM10 emissions recorded by Maricopa

County area monitors coming from s ources outside of the Phoenix PM 10 nonattainment area, provides

strong evidence that the events and exceedances of August 25-28, 2011, recorded within the Phoenix

PM10 nonattainment area, were not reasona bly controllable or preventable.

28

# V. CLEAR CAUSAL RELATIONSHIP

Introduction

A demonstration of the clear causa l connection between uncontrollable natural events or uncontrollable

emissions associated with thunderstorm outflows and PM10 exceedance days during the time period of

August 25–28, 2011 is presented in the following time series graphs, infrared satellite imagery, and

National Weather Service (NWS) data tables for selecte d, representative airports. These various pieces of

information contain data on sustai ned wind speed, wind speed gusts, PM 10 concentrations, visibility,

weather observations, and thundersto rm development areas and provide the causal connection between

the uncontrollable emissions associated with thunderstorm outflows and elevated PM10 concentrations.

Additional NWS text products issued during the August 25-28 period co ntaining forecasts and warnings

of blowing dust due to thunderstorms outflows are included for referen ce in Appendix D. A summary of

each event day is provided below.

Event #1 – August 25, 2011:

On August 24, the day prior to the first event, the Phoenix region experi enced typical summertime

weather conditions (Phoenix Sky Ha rbor International Ai rport: maximum temperature of 111°F, relative

humidity of 10-30%, winds at 5-12 miles per hour (mph) mainly out of the west, visibility at 10 miles all

day) and PM10 concentrations ( 24-hour averages in the 30-70 μg/m 3 

# range). Between 8 p.m. Mountain

Standard Time (MST) and 11 p.m. MST, severe t hunderstorms developed over the southeastern Arizona

and northern Mexico (as shown in Figure 5-1) and by 1 a.m. on August 25, outflows from the

thunderstorms entrained dust from de sert areas of Pinal County and ge nerated a “haboob” that progressed

northwestward into Maricopa County, transporting large amounts of PM10. As shown in Figure 5-2, the

“haboob” had the following impacts in the Phoenix area: southeasterly winds increased to 18-26 mph,

with gusts up to 34 mph; visibility dropped from 10 miles to 2 miles; we ather conditions were reported as

“haze”; and hourly PM10 concentrations increased from about 30-50 μg/m 3 

# to 2000+ μg/m 3 

# at five sites

and over 4000 μg/m 3 

# at the Greenwood site in central Phoeni x. Once the winds subsided, visibility

remained below 10 miles and PM10 concentrations rema ined high for several hours, resulting in 24-hour

average concentratio ns between 200–450 μg/m 3 

# at more than 10 monitoring sites on August 25. In total,

12 monitoring sites in the region ex ceeded the PM10 NAAQS and, as was mentioned in the Historical

Fluctuation section, 7 sites out of the 16 PM10 mon itoring in the Phoenix nonattainment area saw their

highest 24-hour average PM10 concentr ation measured in the past five years. Without the existence of

the emissions generated by these thu nderstorm outflows, there would not have been any exceedances of

the 24-hour PM10 standard in the Phoenix PM10 nonattainment area.

29

# 12:00 p.m. 2:00 p.m. 4:00 p.m. 6:00 p.m.

1900z Aug 24 2100z Aug 24 2300z Aug 24 0100z Aug 25

8:00 p.m. 10:00 p.m. 12:00 a.m. 3:00 a.m.

0300z Aug 25 0500z Aug 25 0700z Aug 25 1000z Aug 25

Figure 5-1. Satellite im agery showing strong storms de veloping and dissipating over northern Mexico.

These storms are believed to have been responsible for the thunderstorm outflow boundary that caused

PM10 exceedances throughout Maricopa and Pinal counties on August 25.

Figure 5-2 depicts the first dust event that occurr ed in Maricopa County impacting the Phoenix area

during the August 25-28 period. Hourly averaged PM10 concentrations at monitors throughout Maricopa

County are shown along with visibility readings (blue diamonds) and wind speeds reported at the Phoenix

Sky Harbor Airport. Sky Harbor measurements were used due to its central lo cation amongst a number of

the monitors that experienced exceedances on August 25. As can be seen in the graph, visibility was

reduced down to two miles at the Sky Harbor Airport during the wi ndblown dust event and this visibility

reduction coincided with increased wind speeds in the 20-30 mph range and PM10 concentrations across

Phoenix.

As shown in Figure 5-3, several monitoring sites in the upwind, dust source region of Pinal County

measured 24-hour average PM10 exceedances with th e peak site, Cowtown, having a 24-hour average of

1,064 μg/m 3 

# and an astonishing maximum 1-hour aver age during the 2 a.m. hour of 15,056 μg/m 3 

# . Only

monitoring sites in Mari copa and Pinal counties exceeded the NAAQS due to thunderstorm outflows on

this day, but the broad range of sites and the extreme hourly- and da ily-averaged PM10 concentrations

reflect the magnitude of the “haboob.” Additionally, the NWS airport meteorologi cal data tables after

Figure 5-3 show that the strongest winds associated with the haboob were out of the southeast. These

winds combined with the high PM10 concentrations in Pinal County indicat e that PM10 was already

entrained in the atmosphere outside of the Phoenix PM10 nonattainment area and th en transported into the

region by the strong winds.

30

# Figure 5-3. Phoenix nonattainm ent area PM10 monitor readi ngs and Sky Harbor visibility and wind

speed for August 25, 2011.

31

# Figure 5-2. Pinal County PM10 monitor readin gs and Casa Grande visibility and wind speed for August

25, 2011.

32U.S. Department of CommerceNational Oceanic & Atmospheric AdministrationQUALITY CONTROLLED LOCALCLIMATOLOGICAL DATA(final)HOURLY OBSERVATIONS TABLEPHOENIX SKY HARBORINTL AIRPORT (23183)PHOENIX, AZ(08/2011)National Climatic Data CenterFederal Building151 Patton AvenueAsheville, North Carolina 28801Elevation: 1107 ft. above sea levelLatitude: 33.427Longitude: -112.003Data Version: VER3DryBulbTempWetBulbTempDewPointTempDateTime(LST)StationTypeSkyConditionsVisibility(SM)WeatherType(F)(C)(F)(C)(F)(C)RelHumd%WindSpeed(MPH)WindDirWindGusts(MPH)StationPressure(in. hg)PressTendNet3-hrChg(mb)SeaLevelPressure(in. hg)ReportTypePrecip.Total(in)Altimeter(in. hg)12345678910111213141516171819202122232525252525252525252525252525252525252525252525252525252525005101490151015902080216022302510351045105510651075108510951105111511251135114511551165117511851195120512151225123511111111111111111111111111111111111111111111111111111111111SCT170 SCT210 SCT250SCT017 SCT170 SCT210SCT015 SCT170 SCT210BKN015 BKN170 BKN210BKN015 BKN170 BKN210BKN015 BKN170 BKN210SCT170 SCT210FEW170 SCT210FEW170 SCT210SCT200 BKN250SCT200 BKN250SCT170 BKN220SCT170 BKN220SCT170 BKN200SCT170 BKN200FEW095 SCT170 BKN210FEW120 SCT170 BKN210FEW120 SCT170 SCT210FEW120 SCT170 SCT210FEW120 SCT170 SCT210FEW120 SCT170 SCT210FEW120 SCT170 SCT210FEW120 SCT170 SCT210FEW120 SCT170 SCT210FEW120 SCT170 SCT210SCT150 SCT200 BKN250BKN210BKN160 BKN210FEW120 BKN160 BKN21010.002.502.001.752.507.007.007.006.007.007.007.008.009.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.00HZHZHZHZHZ10199999999979795939392939497100100105108109113110110110108107103102999938.337.037.237.037.036.036.035.033.933.933.333.934.436.137.837.840.642.242.845.043.343.343.342.241.739.438.937.237.2706970707070707070706970707071717171727271717169697171707021.220.720.921.121.121.121.121.020.920.920.820.921.121.321.521.821.621.622.022.421.521.721.720.420.721.721.421.120.9535253545455555657575757575655565250515048494944465453545311.711.011.712.012.013.013.013.313.913.913.913.913.913.312.813.311.110.010.610.08.99.49.46.77.812.211.712.211.72021212222242427303031302925222317141512131313121320192221102426161821151060355360337113575515141516140150160160120130130140140000230220220VR160000VRVR080190VRVR300200110060080050060223333322428282128.6028.6228.6228.6328.6328.6328.6328.6328.6228.6228.6128.6428.6628.6628.6628.6628.6528.6228.6028.5628.5228.5128.5128.5328.5528.5828.6028.6028.613830763101800201300402402801301729.70M29.72MMMM29.7229.7229.7129.7129.7429.7529.7629.7729.7729.7429.7229.6929.6529.6229.6129.6129.6229.6529.6829.7029.7029.71AASPAASPSPSPSPAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA29.7729.7929.7929.8029.8029.8029.8029.8029.7929.7929.7829.8129.8329.8429.8429.8429.8229.7929.7729.7329.6929.6829.6829.7029.7229.7529.7729.7729.7833U.S. Department of CommerceNational Oceanic & Atmospheric AdministrationQUALITY CONTROLLED LOCALCLIMATOLOGICAL DATA(final)HOURLY OBSERVATIONS TABLEWILLIAMS GATEWAY AIRPORT (23104)PHOENIX, AZ(08/2011)National Climatic Data CenterFederal Building151 Patton AvenueAsheville, North Carolina 28801Elevation: 1382 ft. above sea levelLatitude: 33.3Longitude: -111.666Data Version: VER2DryBulbTempWetBulbTempDewPointTempDateTime(LST)StationTypeSkyConditionsVisibility(SM)WeatherType(F)(C)(F)(C)(F)(C)RelHumd%WindSpeed(MPH)WindDirWindGusts(MPH)StationPressure(in. hg)PressTendNet3-hrChg(mb)SeaLevelPressure(in. hg)ReportTypePrecip.Total(in)Altimeter(in. hg)12345678910111213141516171819202122232525252525252525252525252525252525252525252525252525252525252525252500150035005501150135015502150235025503150335035504150435045505150535055306470747085009461049114712481348145015541750184719471955201520350000000000000000000000000000000000CLRCLRCLRCLRVV007CLRCLRCLRCLRCLRCLRCLRCLRCLRCLRCLRCLRSCT150 BKN200SCT140 BKN200BKN140 BKN200BKN140 BKN200BKN140 BKN200BKN140 BKN200SCT120 SCT200FEW120 SCT120FEW120 SCT200FEW120 SCT200FEW120 SCT200FEW120 SCT200FEW120 SCT200SCTCLRCLRCLR10.0010.007.0010.001.7510.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0020.0015.0015.0015.0015.0015.0035.0035.0035.0035.0035.0035.0020.0020.0010.0010.0010.00HZ99999997979797939791919393939190919391939710210210610910910911110910910610410410437.037.037.036.036.036.036.034.036.033.033.034.034.034.033.032.033.034.033.034.036.039.039.041.043.043.043.044.043.043.041.040.040.040.0707070707070727072696971707169696971707171737272737371727070M71717221.121.121.121.021.021.022.120.922.120.620.621.420.921.420.620.420.621.421.121.521.522.822.322.422.622.621.722.420.920.9M21.421.422.15454545555555957595757595759575757595959575957555454505246465452525512.012.012.013.013.013.015.014.015.014.014.015.014.015.014.014.014.015.015.015.014.015.014.013.012.012.010.011.08.08.012.011.011.013.0222222242424283028323232303232333232343226242319161614141212M1818209921202515107530056675676375077599713367140140130120120130140120120160000000280310320320310290210210240270290000VR13017024027027006006013016024332328.3628.3728.3828.3928.4028.4028.3928.3828.3728.3728.3728.3728.3628.3628.3628.3628.3628.3628.4028.4128.4228.4328.4228.3928.3728.3428.3128.2828.2728.29M28.3228.3328.34MMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA29.8229.8329.8429.8529.8629.8629.8529.8429.8329.8329.8329.8329.8229.8229.8229.8229.8229.8229.8629.8729.8829.8929.8829.8529.8329.8029.7729.7429.7329.7529.7829.7829.7929.80342525252525252525252520552115213521552215223522552315233523550000000000CLRCLRCLRCLRCLRCLRCLRCLRCLRCLR10.007.0010.0010.0010.0010.0010.0010.0010.0010.0010010010010210010010010010010038.038.038.039.038.038.038.038.038.038.07070707169697070707021.221.221.321.620.820.321.321.321.321.35454545452505454545412.012.012.012.011.010.012.012.012.012.0212121202019212121216066613161514141700000400403600300300500400401623211828.3528.3528.3628.3628.3628.3628.3628.3628.3628.37MMMMMMMMMMAAAAAAAAAAAAAAAAAAAA29.8129.8129.8229.8229.8229.8229.8229.8229.8229.8335U.S. Department of CommerceNational Oceanic & Atmospheric AdministrationQUALITY CONTROLLED LOCALCLIMATOLOGICAL DATA(final)HOURLY OBSERVATIONS TABLECASA GRANDE MUNICIPAL ARPT (03914)CASA GRANDE, AZ(08/2011)National Climatic Data CenterFederal Building151 Patton AvenueAsheville, North Carolina 28801Elevation: 1462 ft. above sea levelLatitude: 32.95Longitude: -111.766Data Version: VER2DryBulbTempWetBulbTempDewPointTempDateTime(LST)StationTypeSkyConditionsVisibility(SM)WeatherType(F)(C)(F)(C)(F)(C)RelHumd%WindSpeed(MPH)WindDirWindGusts(MPH)StationPressure(in. hg)PressTendNet3-hrChg(mb)SeaLevelPressure(in. hg)ReportTypePrecip.Total(in)Altimeter(in. hg)12345678910111213141516171819202122232525252525252525252525252525252525252525252525252525252525252500150035005501150135015502150235025503150335035504150435045505150535055506150635065507150735075508150835085509150935095510150000000000000000000000000000000CLRFEW065 SCT080 BKN110FEW015 FEW065 SCT080SCT015 SCT020FEW013CLRCLRCLRCLRCLRCLRCLRCLRCLRCLRCLRCLRCLRCLRCLRCLRCLRCLRCLRCLRCLRCLRCLRCLRCLRCLR10.0010.005.002.505.004.003.004.005.007.006.007.007.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.00TS99979791919191919190909088888888909090908688909193959799999910037.036.036.033.033.033.033.033.033.032.032.032.031.031.031.031.032.032.032.032.030.031.032.033.034.035.036.037.037.037.038.06970696969696868686868686767676869696869696869696969707071717220.621.020.820.620.620.620.020.020.019.919.919.919.519.519.520.120.420.419.920.420.320.120.420.620.420.721.021.321.821.822.05255545757575555555555555555555757575557595757575555555557575711.013.012.014.014.014.013.013.013.013.013.013.013.013.013.014.014.014.013.014.015.014.014.014.013.013.013.013.014.014.014.0212424323232303030313131333333353333313340353332282624232525248026s22171309500000000537005710101317161490800001101201501500001301800000000000000000000000000400801200000000300300800600800700600700802334292322181828.2928.3028.3228.3128.3028.3028.3028.2928.2828.2728.2728.2728.2728.2728.2728.2728.2828.2828.2928.3028.3028.3128.3128.3228.3228.3228.3328.3328.3328.3328.34272017014020MMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA29.8429.8529.8729.8629.8529.8529.8529.8429.8329.8229.8229.8129.8229.8129.8129.8129.8329.8329.8429.8529.8529.8629.8629.8729.8729.8729.8829.8829.8829.8829.89363725252525252525252525252525252525252525252525252525252525252525252525252525252525251035105511151135115512151235125513151335135514151435145515151535155516151635165517151735175518151835185519151935195520152035205521152135215522152235225523152335235500000000000000000000000000000000000000000CLRCLRCLRCLRCLRCLRCLRCLRCLRCLRCLRCLRCLRCLRCLRCLRCLRCLRCLRCLRCLRCLRCLRCLRCLRCLRCLRCLRBKN004SCT004 BKN120FEW070 SCT100FEW043 FEW100CLRCLRCLRFEW032 FEW045 SCT065CLRCLRCLRCLRCLR10.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.001.009.005.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.00VCTSVCTSTSTS10010010210210210410410610810610610610810810610610610610610610610610610610410410210299100999999979797999795919138.038.039.039.039.040.040.041.042.041.041.041.042.042.041.041.041.041.041.041.041.041.041.041.040.040.039.039.037.038.037.037.037.036.036.036.037.036.035.033.033.0727272717173727272727272727272717171717171717171717169697070707072747371717070717022.022.022.321.821.822.622.122.422.422.122.122.122.422.422.121.721.721.721.721.721.721.721.721.721.421.420.620.621.321.221.121.322.323.222.621.521.821.021.221.721.1575757555557555554545454545454525252525252525252525250505554545559636157575557615914.014.014.013.013.014.013.013.012.012.012.012.012.012.012.011.011.011.011.011.011.011.011.011.011.011.010.010.013.012.012.013.015.017.016.014.014.013.014.016.015.0242423212121201917181818171718171717171717171717181817172321222327333026252428373413811663706071091089777705000006212026137531016108500900900801000601601400001900002402101902102302302202302402400002000000000000000000800900501100300200903600100700801102300001716303126202328.3328.3228.3228.3128.3028.2928.2928.2828.2828.2728.2728.2528.2528.2428.2328.2228.2128.2028.2028.2028.2028.2028.2028.2028.2128.2128.2228.2328.2428.2428.2528.2428.2428.2528.2528.2528.2528.2728.2728.2828.2847722000020024014010MMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA0.020.020.0229.8829.8729.8729.8629.8529.8429.8429.8329.8329.8229.8129.8029.8029.7829.7729.7629.7529.7429.7429.7429.7429.7429.7429.7429.7529.7529.7629.7729.7829.7829.7929.7829.7829.7929.7929.7929.8029.8129.8229.8329.83

# Event #2 – August 26, 2011:

A single exceedance at the Apache Junction monitor in Pinal County, but locat ed within the eastern

boundary of the Phoenix PM10 nonattainment area , occurred on August 26, 2011, and was caused by

emissions generated from thunderstorm outflows originat ing in the southwestern deserts of the state (see

Figure 5-4). The exceedance was limited to the eas tern-most Apache Junction monitor due to the

presence of moderate westerly winds in most of Maricopa County, but str ong southwesterly winds in

Pinal County. Without the dust gene rated by the thunderstorm outflows, there would not have been an

exceedance of the 24-hour PM10 standard in the Phoenix PM10 nonattainment area.

1:00 p.m. 2:00 p.m. 4:00 p.m. 6:00 p.m.

1900z Aug 26 2100z Aug 26 2300z Aug 26 0100z Aug 27

8:00 p.m. 10:00 p.m. 12:00 a.m. 3:00 a.m.

0300z Aug 27 0500z Aug 27 0700z Aug 27 1000z Aug 27

Figure 5-4. Satellite im agery showing strong storms de veloping and dissipating over southwestern

Arizona. These storms are believed to have been responsible for the thunderstorm outflow boundary that

caused PM10 exceedances in the eastern portion of the Phoenix PM10 nonattainment area and in Pinal

County on August 26.

Thunderstorms developed over southwestern Arizona during the mid-afternoon hours and, by the early

evening hours, winds out of the west-southwest reach ed sustained speeds up to 30 mph at the Phoenix

Mesa Williams Airport (also called the Williams Gate way Airport) in southeastern Maricopa County,

visibility rapidly decreased from 35 miles to 2 miles, and PM10 concen trations simultaneously increased

from around 50 μg/m 3 

# to over 500 μg/m 3 

# at multiple monitoring sites (see Figure 5-5) as dust was

transported into the region. The Mesa Williams data we re used for this event due to the proximity of that

station to the monitors that were most impacted by the dust event. Considering the amount of deposition

of dust from the event on August 25 th 

# , very loose soils were also easily re-entrained back into the

atmosphere, contributing to the ri se in PM10 concentrations. The thunderstorm outflow winds produced

broad areas of windblown dust that impacted most of the Phoenix PM10 nonattainment area monitoring

sites (Figure 5-5 shows peak 1-hour concentrations on the 26 th 

# ranging from 200 μg/m 3 

# to 850 μg/m 3 

# ), but

due to the short duration of the strong winds in the Phoenix area and the southwesterl y direction of the

winds allowing the Estrella Mountain and South Mount ain ranges to limit some of the PM10 transport,

none of the Maricopa County monitoring sites exceeded the standard. It should be noted, though, that the

38

# Higley m onitor in far southeastern Maricopa County did record a 24-hour aver age PM10 concentration of

150 μg/m 3 

# , which was one microgram shy of an exceedance . However, to the south in Pinal County,

where the winds were not obstructed by terrai n, hourly PM10 concentrations exceeded 1,500 μg/m 3 

# at

three sites (see Figure 5-6) and six of the seven PM 10 monitoring sites in the county exceeded the PM10

standard. Because of the southwesterly wind flow direction, PM10 was transported through Pinal County

and southeastern Maricopa County and toward the Apache Junction monitor. The peak PM10

concentrations at this monitoring site occurred a couple hours later than most of the other sites and

because the winds weakened by the time they reached the Apache Junc tion area, the dust remained over

the Apache Junction monitoring site for several hours, causing it to measure the only 24-hour average

exceedance within the Phoenix PM10 nonattainment area on this day.

A visualization of this dust event wa s created using Phoenix visibility camera images and can be found at:

www.phoenixvis.net/videos/ m peg4/SOMT_08262011.mp4

The video clearly shows the dust blowing across the Phoenix region, but the dust cloud was not as dense

as it was in videos of the windblow n dust events in early July 2011. Videos showing other views across

the Valley on this date are also ava ilable (see Visibility Cameras section).

39

# Figure 5-5. Phoenix nonattainm ent area PM10 monitor readi ngs and Mesa Williams visibility and wind

speed for August 26, 2011.

40

# Figure 5-6. Pinal County PM10 monitor readin gs and Casa Grande visibility and wind speed for August

26, 2011.

41U.S. Department of CommerceNational Oceanic & Atmospheric AdministrationQUALITY CONTROLLED LOCALCLIMATOLOGICAL DATA(final)HOURLY OBSERVATIONS TABLEPHOENIX SKY HARBORINTL AIRPORT (23183)PHOENIX, AZ(08/2011)National Climatic Data CenterFederal Building151 Patton AvenueAsheville, North Carolina 28801Elevation: 1107 ft. above sea levelLatitude: 33.427Longitude: -112.003Data Version: VER3DryBulbTempWetBulbTempDewPointTempDateTime(LST)StationTypeSkyConditionsVisibility(SM)WeatherType(F)(C)(F)(C)(F)(C)RelHumd%WindSpeed(MPH)WindDirWindGusts(MPH)StationPressure(in. hg)PressTendNet3-hrChg(mb)SeaLevelPressure(in. hg)ReportTypePrecip.Total(in)Altimeter(in. hg)1234567891011121314151617181920212223262626262626262626262626262626262626262626262626005101510251035104510551065107510851095110511151125113511451155116511751185119512051215122512351111111111111111111111111111111111111111111111111FEW120 SCT160 BKN210FEW120 SCT160 BKN210CLRFEW250SCT150 BKN250FEW100 SCT150 SCT250FEW150 SCT180 SCT210FEW150 SCT180 SCT210FEW150 SCT180 SCT210FEW150 SCT180 SCT210FEW120TCU SCT150 SCT210FEW120 SCT150 SCT210FEW120 SCT180 SCT210FEW120 SCT180 SCT250FEW120 SCT180 SCT250SCT120 SCT180 BKN250SCT120 SCT180 BKN250SCT120 SCT180 BKN250SCT120 SCT180 BKN250SCT120 SCT180 SCT250FEW120 SCT180 SCT250FEW120 SCT180 SCT250FEW120 SCT250FEW120 SCT25010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.009897959494949496101105108109111115113113113110105105102100999636.736.135.034.434.434.434.435.638.340.642.242.843.946.145.045.045.043.340.640.638.937.837.235.670706969696970707171727273737272727272727373727221.020.820.720.620.320.620.821.221.721.822.322.222.722.822.222.222.022.322.322.322.622.622.422.254545555545556565553535253514949485255555859596012.212.212.812.812.212.813.313.312.811.711.711.111.710.69.49.48.911.112.812.814.415.015.015.62324262726272826221816151512121212151919232627309666101111810878778118111177339080130130080080070080080100100150080VRVR1501901802002502701001601601501828.6228.6128.6128.6028.6128.6328.6528.6628.6628.6828.6628.6528.6328.6028.5728.5628.5628.5728.5928.6128.6528.6528.6628.660310853100200201600302301401501829.7129.7029.7029.7029.7129.7329.7529.7629.7729.7729.7729.7529.7329.7029.6729.6529.6629.6729.6829.7029.7529.7529.7629.76AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA29.7929.7829.7829.7729.7829.8029.8229.8329.8429.8529.8429.8229.8029.7729.7429.7329.7329.7429.7629.7829.8229.8229.8329.8342U.S. Department of CommerceNational Oceanic & Atmospheric AdministrationQUALITY CONTROLLED LOCALCLIMATOLOGICAL DATA(final)HOURLY OBSERVATIONS TABLEWILLIAMS GATEWAY AIRPORT (23104)PHOENIX, AZ(08/2011)National Climatic Data CenterFederal Building151 Patton AvenueAsheville, North Carolina 28801Elevation: 1382 ft. above sea levelLatitude: 33.3Longitude: -111.666Data Version: VER2DryBulbTempWetBulbTempDewPointTempDateTime(LST)StationTypeSkyConditionsVisibility(SM)WeatherType(F)(C)(F)(C)(F)(C)RelHumd%WindSpeed(MPH)WindDirWindGusts(MPH)StationPressure(in. hg)PressTendNet3-hrChg(mb)SeaLevelPressure(in. hg)ReportTypePrecip.Total(in)Altimeter(in. hg)12345678910111213141516171819202122232626262626262626262626262626262626262626262626262626262626262626262600150035005501150135015502150235025503150335035504150435045505150535054706470747094710481147124713471447154716471747175718351847193119470000000000000000000000000000000000CLRCLRCLRCLRCLRCLRCLRCLRCLRCLRCLRCLRCLRCLRCLRCLRCLRFEW150 SCT200FEW120 FEW200FEW200FEW120 SCT200FEW120 SCT200FEW120 SCT200SCT120 SCT200SCT120TCU BKN200SCT120TCU BKN200SCT120TCU BKN200SCT120 BKN250SCT120 BKN200SCT120 BKN200SCT120 BKN200SCT120 BKN200SCT120 BKN200BKN10.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0020.0045.0045.0045.0045.0045.0045.0045.00s35.0035.0035.0020.002.005.005.005.005.00BLDUBLDUBLDUsBLDUBLDU999999999797979797919190909088888688909710610910911111710911511511110910210210210237.037.037.037.036.036.036.036.036.033.033.032.032.032.031.031.030.031.032.036.041.043.043.044.047.043.046.046.044.043.039.039.039.039.0707070706969696969686968686869696969697373737373757374737272727375M21.121.121.121.120.820.820.820.820.820.120.619.919.919.920.620.620.320.620.422.622.922.622.622.923.722.623.422.622.022.122.322.823.9M5454545454545454545557555555595959595761575454545454545050525759636112.012.012.012.012.012.012.012.012.013.014.013.013.013.015.015.015.015.014.016.014.012.012.012.012.012.012.010.010.011.014.015.017.016.0222222222424242424303231313138384038333020161615131614121315232428M15141085500035000000553611168151177530s9s11219040030030030360050000000000260270000000000000000000090110120VR15018019019016018017012022021024013017028.3628.3628.3628.3728.3728.3628.3628.3628.3628.3628.3628.3628.3628.3628.3728.3828.3828.3928.4028.4128.4328.4228.4128.3928.3628.3428.3228.3228.3228.3428.3528.3628.38MMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA29.8229.8229.8229.8329.8329.8229.8229.8229.8229.8229.8229.8229.8229.8229.8329.8429.8429.8529.8629.8729.8929.8829.8729.8529.8229.8029.7829.7829.7829.8029.8129.8229.8429.85432626262626262626262626262619552015203520552115213521552215223522552315233523550000000000000CLRCLRCLRCLRCLRCLRCLRCLRCLRCLRCLRCLRCLR7.007.005.005.005.005.005.005.005.007.0010.0010.0010.00HZHZHZHZHZHZHZ10010010010099999997979797979338.038.038.038.037.037.037.036.036.036.036.036.034.07473747472727272727271737123.122.523.123.122.422.422.422.122.122.121.522.621.56159616159595959595957615916.015.016.016.015.015.015.015.015.015.014.016.015.0282628282727272828282630321090303055855016011000006000003000012013018016016000028.3928.4028.4028.4128.4128.4128.4228.4228.4228.4328.4228.4328.43MMMMMMMMMMMMMAAAAAAAAAAAAAAAAAAAAAAAAAA29.8529.8629.8629.8729.8729.8729.8829.8829.8829.8929.8829.8929.8944U.S. Department of CommerceNational Oceanic & Atmospheric AdministrationQUALITY CONTROLLED LOCALCLIMATOLOGICAL DATA(final)HOURLY OBSERVATIONS TABLECASA GRANDE MUNICIPAL ARPT (03914)CASA GRANDE, AZ(08/2011)National Climatic Data CenterFederal Building151 Patton AvenueAsheville, North Carolina 28801Elevation: 1462 ft. above sea levelLatitude: 32.95Longitude: -111.766Data Version: VER2DryBulbTempWetBulbTempDewPointTempDateTime(LST)StationTypeSkyConditionsVisibility(SM)WeatherType(F)(C)(F)(C)(F)(C)RelHumd%WindSpeed(MPH)WindDirWindGusts(MPH)StationPressure(in. hg)PressTendNet3-hrChg(mb)SeaLevelPressure(in. hg)ReportTypePrecip.Total(in)Altimeter(in. hg)12345678910111213141516171819202122232626262626262626262626262626262626262626262626262626262626262600150035005501150135015502150235025503150335035504150435045505150535055506150635065507150735075508150835085509150935095510150000000000000000000000000000000CLRCLRCLRCLRCLRCLRCLRCLRCLRCLRCLRCLRCLRCLRCLRCLRCLRCLRCLRCLRCLRCLRCLRCLRCLRCLRCLRCLRCLRCLRCLR10.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.009088909086868888848686848684848484848484868888909091919395979932.031.032.032.030.030.031.031.029.030.030.029.030.029.029.029.029.029.029.029.030.031.031.032.032.033.033.034.035.036.037.07070706970706867676868676867676767676769697069707171717272747321.021.221.020.420.920.920.119.519.419.719.719.419.719.419.419.419.419.419.420.520.321.220.621.021.521.721.722.022.323.222.95961595761615755575757575757575757575761596159596161616161636115.016.015.014.016.016.014.013.014.014.014.014.014.014.014.014.014.014.014.016.015.016.015.015.016.016.016.016.016.017.016.035403533434335334037374037404040404040464040383538373734323329005035656666788885556556575638600000029000033001001002035033035001036035035036035001013011011010008008011011012013011011009028.2828.2828.2928.2928.2828.2828.2728.2728.2728.2728.2728.2728.2728.2728.2728.2828.2828.2928.3028.3128.3128.3228.3228.3328.3328.3328.3428.3428.3428.3428.34272007003020MMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA29.8329.8329.8429.8429.8329.8329.8229.8229.8229.8229.8229.8229.8229.8229.8229.8329.8329.8429.8529.8629.8629.8729.8729.8829.8829.8829.8929.8929.8929.8929.89454626262626262626262626262626262626262626262626262626262626262626262626262626262626261035105511151135115512151235125513151335135514151435145515151535155516151635165517151735175518151835185519151935195520152035205521152135215522152235225523152335235500000000000000000000000000000000000000000CLRCLRCLRCLRCLRCLRCLRCLRCLRCLRCLRCLRCLRCLRCLRCLRCLRCLRCLRCLRCLRSCT005FEW005OVC005BKN003 BKN007CLRCLRCLRCLRCLRCLRCLRCLRCLRCLRCLRCLRCLRCLRCLRCLR10.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.009.0010.0010.0010.0010.008.0010.0010.001.252.500.751.0010.0010.004.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.00100100102102104106106108109108108108106102104106109108106108102999997979797979797979595939391919090908838.038.039.039.040.041.041.042.043.042.042.042.041.039.040.041.043.042.041.042.039.037.037.036.036.036.036.036.036.036.036.035.035.034.034.033.033.032.032.032.031.0747474747474747474737373727172727372727473737474737373727272727070707070706971717023.023.023.323.323.123.423.423.123.322.722.722.722.421.822.122.422.822.422.423.122.822.923.523.222.622.622.622.122.122.122.121.221.220.920.921.121.120.421.521.521.2616161615959595757555555555555555554555759616363616161595959595757575759595761616116.016.016.016.015.015.015.014.014.013.013.013.013.013.013.013.013.012.013.014.015.016.017.017.016.016.016.015.015.015.015.014.014.014.014.015.015.014.016.016.016.02828262623212119181717171921201917171919242931333030302828282828283030343433383840870655858989181481090132120181613765141356556663303010013000018009013013010018007008004009009008008007000024025023021021021024022013011010010031026022013016019021027000026000023252328.3428.3428.3328.3328.3228.3228.3128.3028.2928.2828.2728.2728.2528.2528.2428.2428.2428.2428.2428.2528.2728.2728.2728.2728.2728.2728.2828.3028.3028.3028.3028.3028.3028.3328.3428.3428.3428.3428.3328.3328.3227722003024010020014MMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA29.8929.8929.8829.8829.8729.8729.8629.8529.8429.8329.8229.8129.8029.7929.7829.7829.7829.7829.7829.7929.8229.8229.8129.8129.8129.8229.8329.8529.8529.8529.8529.8529.8529.8829.8929.8929.8929.8929.8829.8829.87

# Event #3 – August 27-28, 2011:

On August 27, 2011, weather conditions were nearly identical to those on August 24, and once again

severe thunderstorms developed in the evening hours (see Figure 5-7) over southwestern Arizona, and

thunderstorm outflows produced a “ha boob.” This resulted in the follo wing impacts in the Phoenix area:

winds increased to 20-25 mph, with gus ts up to 32 mph; visibility dropp ed from 10 miles to as low as 1

mile; and weather conditions were reported as “blowi ng dust” and “haze” at multiple airports in the

region. Due to two previous days with dust even ts leading up to this one, broad, ambient PM10

concentrations were elevated from those e xpected this time of year, roughly 50-100 μg/m 3 

# prior to the

arrival of the “haboob,” but during the hour s of peak wind gusts late on August 27 th 

# , hourly PM10

concentrations exceeded 2400+ μg/m 3 

# at six sites and over 3600 μg/m 3 

# at the West 43rd site in Phoenix.

Eleven sites total in the Phoeni x PM10 nonattainment area exceeded the PM10 standard on August 27 and

August 28. Without the existence of the PM10 emissions generated by the thunderstorm outflows and the

transport of dust from western Arizona into the Phoenix region, there would not have been any

exceedances of the 24-hour PM10 standard in the Phoenix PM10 nonattainment area.

12:00 p.m. 2:00 p.m. 4:00 p.m. 6:00 p.m.

1900z Aug 27 2100z Aug 27 2300z Aug 27 0100z Aug 28

8:00 p.m. 10:00 p.m. 12:00 a.m. 3:00 a.m.

0300z Aug 28 0500z Aug 28 0700z Aug 28 1000z Aug 28

Figure 5-7. Satellite im agery showing strong storms deve loping and dissipating ove r south-southwestern

Arizona. These storms are believed to have been responsible for the thunderstorm outflow boundary that

caused PM10 exceedances across the Phoenix PM 10 nonattainment area and in Pinal County on

August 27-28.

47

# Figures 5-8 and 5-10 show the hourly PM10 concentr ations at m onitors throughout the Phoenix PM10

nonattainment area as well as visibility readings a nd sustained wind speeds reported at the Phoenix Sky

Harbor Airport for August 27 th 

# and 28 th 

# . Most of the monitors show large PM10 concentration increases,

along with corresponding visibility decreases at the airport, between 8:00 p.m. on the August 27 and 1:00

a.m. on August 28 as light southeasterly winds abruptly shifted to strong westerly winds with the arrival

of the thunderstorm outflow winds. These PM10 spikes and reductions in visibility also coincided with

reports of blowing dust and haze at the Sky Harbor Air port. Due to the west-to-east flow of the winds,

the transport of dust impacted the PM10 monitoring si tes sequentially from Buckeye in the west, to the

central Phoenix area, to West Cha ndler, and then lastly to the Higl ey and Apache Junction sites on the

eastern side of the Phoenix PM10 nonattainment area. Th e timing of winds resulted in the majority of the

sites experiencing peak 1-hour PM10 c oncentrations very late on August 27 th 

# , causing their 24-hour

averages and PM10 exceedances to occur on the 27 th 

# . However, the dust storms did not reach the eastern

side of the region until after midnight, causing the Higley and Apache Junction monitors to experience

their peak 1-hour concentrations and lingering elevated PM10 concentr ations for several hours on August

28 (as shown in Figure 5-10); therefore, the exce edances for those two sites occurred on the 28 th 

# . While

the monitoring sites in Pinal County also experienced PM10 exceedances on August 27 th 

# and 28 th 

# (see

Figures 5-9 and 5-11), the we sterly wind direction during this event meant that desert areas to the west of

the Phoenix PM10 nonattainment area were the primary dus t source region, rather th an the desert areas of

Pinal County, as was the case with the firs t two events during th e August 25-28 period.

48

# Figure 5-8. Phoenix nonattainm ent area PM10 monitor readi ngs and Sky Harbor visibility and wind

speed for August 27, 2011.

49

# Figure 5-9. Pinal County PM10 monitor readin gs and Casa Grande visibility and wind speed for August

27, 2011.

50

# Figure 5-10. Phoenix nonattainm ent area PM10 monitor readi ngs and Mesa Williams visibility and wind

speed for August 28, 2011.

51

# Figure 5-11. Pinal County PM10 monitor readings and Casa Grande visibility and wind speed for August

28, 2011.

52U.S. Department of CommerceNational Oceanic & Atmospheric AdministrationQUALITY CONTROLLED LOCALCLIMATOLOGICAL DATA(final)HOURLY OBSERVATIONS TABLEPHOENIX SKY HARBORINTL AIRPORT (23183)PHOENIX, AZ(08/2011)National Climatic Data CenterFederal Building151 Patton AvenueAsheville, North Carolina 28801Elevation: 1107 ft. above sea levelLatitude: 33.427Longitude: -112.003Data Version: VER3DryBulbTempWetBulbTempDewPointTempDateTime(LST)StationTypeSkyConditionsVisibility(SM)WeatherType(F)(C)(F)(C)(F)(C)RelHumd%WindSpeed(MPH)WindDirWindGusts(MPH)StationPressure(in. hg)PressTendNet3-hrChg(mb)SeaLevelPressure(in. hg)ReportTypePrecip.Total(in)Altimeter(in. hg)123456789101112131415161718192021222327272727272727272727272727272727272727272727272727272727272727005101510251035104510551065107510851095110511151125113511451155116511751185119512000205121512233224822512259231823292342235111111111111111111111111111111111111111111111111111111111111111FEW120 SCT250FEW120 SCT250FEW120 SCT250FEW120 SCT250FEW120 SCT250FEW120 SCT250FEW100 SCT150 SCT200FEW110 SCT160 SCT250FEW110 SCT160 SCT250FEW110 SCT160 SCT250FEW110 SCT160 SCT250FEW110 SCT160 SCT250FEW110 SCT160 SCT250FEW110 SCT250FEW110 SCT180 SCT250FEW110 SCT180 SCT250FEW110 SCT180 SCT250FEW110 SCT180 SCT250SCT110 BKN180 BKN250SCT110 BKN180 BKN250SCT110 BKN180 BKN250SCT130 BKN190 BKN230SCT130 BKN190 BKN250SCT130 BKN190 BKN250SCT130 BKN190 BKN250BKN010 BKN130 BKN190VV008BKN009 BKN130 BKN190BKN009 BKN130 BKN190BKN015 BKN130 BKN190BKN017 BKN130 BKN19010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.006.009.001.751.251.002.004.005.009.00BLDUHZ94949392919191949710110510510711011011011111110310210210199979392919090909034.434.433.933.332.832.832.834.436.138.340.640.641.743.343.343.343.943.939.438.939.038.337.236.034.033.333.032.032.032.032.27372727171717171717272727374737373727169696972737373727373727122.521.922.321.921.721.421.421.621.621.922.322.322.823.023.022.822.522.321.520.520.320.822.122.722.622.522.322.522.522.221.66260626161606059575655555655555452515349485158616363636464636116.715.616.716.116.115.615.615.013.913.312.812.813.312.812.812.211.110.611.79.49.010.614.416.017.017.217.018.018.017.016.135323636373535312622191919161616141419171619263037383942424138768505736735311875516138662223222318181816140140120120000100100130070070VR220290290280VRVR0200600300401301402802802902902903003003001817263228.6628.6628.6528.6628.6628.6628.6928.6928.7028.7028.6928.6828.6628.6428.6028.5828.5728.5628.5828.6028.6028.6228.6428.6628.6628.6628.6628.6628.6828.6928.697330863100100401100002202301002029.7529.7529.7529.7629.7729.7729.8029.8029.8129.8129.8029.7829.7729.7429.7029.6829.6729.6629.6829.70M29.7229.74MM29.76MMMM29.80AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAASPAAAASPSPAASPSPSPSPAA29.8329.8329.8229.8329.8429.8429.8629.8729.8829.8829.8729.8529.8429.8129.7729.7529.7429.7329.7529.7729.7729.7929.8129.8429.8329.8329.8329.8429.8529.8629.8753U.S. Department of CommerceNational Oceanic & Atmospheric AdministrationQUALITY CONTROLLED LOCALCLIMATOLOGICAL DATA(final)HOURLY OBSERVATIONS TABLEPHOENIX SKY HARBORINTL AIRPORT (23183)PHOENIX, AZ(08/2011)National Climatic Data CenterFederal Building151 Patton AvenueAsheville, North Carolina 28801Elevation: 1107 ft. above sea levelLatitude: 33.427Longitude: -112.003Data Version: VER3DryBulbTempWetBulbTempDewPointTempDateTime(LST)StationTypeSkyConditionsVisibility(SM)WeatherType(F)(C)(F)(C)(F)(C)RelHumd%WindSpeed(MPH)WindDirWindGusts(MPH)StationPressure(in. hg)PressTendNet3-hrChg(mb)SeaLevelPressure(in. hg)ReportTypePrecip.Total(in)Altimeter(in. hg)1234567891011121314151617181920212223282828282828282828282828282828282828282828282828005101510251035104510551065107510851095110511151125113511451155116511751185119512051215122512351111111111111111111111111111111111111111111111111SCT130 BKN190FEW130 SCT190FEW130 SCT250SCT200 BKN250SCT200 BKN250FEW130 SCT250FEW110 SCT250FEW110 SCT250FEW110 SCT250FEW110 SCT250FEW150FEW150FEW150FEW110 SCT250FEW110 SCT250FEW110 SCT250FEW110 SCT250FEW110 SCT250FEW110 SCT250FEW110 SCT250FEW250CLRCLRCLR10.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.00909090909191899294961011011041051061071061061041029998979632.232.232.232.232.832.831.733.334.435.638.338.340.040.641.141.741.141.140.038.937.236.736.135.671717171717171717272737273747473727271717171717121.921.921.921.921.721.421.421.922.222.222.722.422.623.023.122.822.422.221.721.621.421.721.621.762626262616061616160595857585856555453545557575816.716.716.716.716.115.616.116.116.115.615.014.413.914.414.413.312.812.211.712.212.813.913.914.439393939373539363330252421212119191818202326262811981087663057131013101316171378911260290330330330270240190220000250VR280310260270260270260270250260280270171717212028.7128.7028.6928.6928.6828.6828.7028.7028.7028.6928.6928.6628.6428.6228.5828.5528.5428.5328.5328.5528.5728.5828.5828.580638863101701001000602502600400929.8229.8129.8029.7929.7829.7829.8129.8129.8129.8129.8029.7829.7529.7229.6829.6529.6429.6329.6329.6529.6729.6829.6729.68AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA29.8929.8829.8729.8629.8529.8529.8829.8829.8829.8729.8629.8429.8129.7929.7529.7229.7129.7029.7029.7229.7429.7529.7529.7554U.S. Department of CommerceNational Oceanic & Atmospheric AdministrationQUALITY CONTROLLED LOCALCLIMATOLOGICAL DATA(final)HOURLY OBSERVATIONS TABLEWILLIAMS GATEWAY AIRPORT (23104)PHOENIX, AZ(08/2011)National Climatic Data CenterFederal Building151 Patton AvenueAsheville, North Carolina 28801Elevation: 1382 ft. above sea levelLatitude: 33.3Longitude: -111.666Data Version: VER2DryBulbTempWetBulbTempDewPointTempDateTime(LST)StationTypeSkyConditionsVisibility(SM)WeatherType(F)(C)(F)(C)(F)(C)RelHumd%WindSpeed(MPH)WindDirWindGusts(MPH)StationPressure(in. hg)PressTendNet3-hrChg(mb)SeaLevelPressure(in. hg)ReportTypePrecip.Total(in)Altimeter(in. hg)12345678910111213141516171819202122232727272727272727272727272727272727272727272727272727272727272727272700150035005501150135015502150235025503150335035504150435045505150535054706470747085009471047114712471347144715471647174717521827185119470000000000000000000000000000000000CLRCLRCLRCLRCLRCLRCLRCLRCLRCLRCLRCLRCLRCLRCLRCLRCLRSCT150SCT150SCT150SCT150SCT150SCT150SCT150SCT150SCT150SCT100 SCT250SCT100 SCT250SCT100 SCT250SCT110 BKN250SCT110 BKN250SCT110CB BKN250SCT110CB BKN250CLR108CB10.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0020.0035.0030.0030.0020.0020.0020.0020.0020.0020.0020.00s3.0020.00s20.00s20.00BLDUBLDUTS BLDUTS91919191908888888888868888888888868888909799102106108108109109111M10810410610233.033.033.033.032.031.031.031.031.031.030.031.031.031.031.031.030.031.031.032.036.037.039.041.042.042.043.043.044.0M42.0s40.041.039.07070707070707071717170707069696869707171747372747674737272M727272M21.121.121.121.121.021.221.221.821.821.820.921.221.220.620.620.120.321.221.821.523.522.922.323.424.223.222.822.122.4M22.422.122.4M5959595959616163636361616159595759616361646157596157555252525455555515.015.015.015.015.016.016.017.017.017.016.016.016.015.015.014.015.016.017.016.018.016.014.015.016.014.013.011.011.011.012.013.013.013.03434343435404043434343404038383540404338342923212219171514M172019M3656035500566635555550661111767132621207080080080090000160130150000000080090070090100110100150120130150000240270240270270260310330040040050VR34292628.4328.4228.4228.4228.4228.4228.4228.4228.4228.4228.4228.4228.4228.4328.4328.4328.4328.4328.4528.4528.4628.4628.4628.4428.4328.4028.3628.3428.3228.3128.3328.3428.36MMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA29.8929.8829.8829.8829.8829.8829.8829.8829.8829.8829.8829.8829.8829.8929.8929.8929.8929.8929.9129.9129.9329.9329.9229.9029.8929.8629.8229.8029.7829.7729.7929.8029.8229.7955272727272727272727272727195520152035205521152135215522152255231523352355000000000000SCT085SCT085CLRCLRCLRCLRCLRCLRCLRCLRCLRCLR10.0010.007.0010.0010.0010.0010.0010.0010.0010.0010.0010.00-RATS10010010097999799979797979738.038.038.036.037.036.037.036.036.036.036.036.070707172727171727273737321.221.321.522.122.421.521.322.122.122.622.622.654545559595755595961616112.012.013.015.015.014.013.015.015.016.016.016.02121222827262328283030301710161033510168711050140150160140220110240260270280310241828161813s1728.3328.3728.4028.4028.3928.3928.3928.4028.4128.4128.4128.44MMMMMMMMMMMMAAAAAAAAAAAAAAAAAAAAAAAA29.7929.8329.8629.8629.8529.8529.8529.8629.8729.8729.8729.9056U.S. Department of CommerceNational Oceanic & Atmospheric AdministrationQUALITY CONTROLLED LOCALCLIMATOLOGICAL DATA(final)HOURLY OBSERVATIONS TABLEWILLIAMS GATEWAY AIRPORT (23104)PHOENIX, AZ(08/2011)National Climatic Data CenterFederal Building151 Patton AvenueAsheville, North Carolina 28801Elevation: 1382 ft. above sea levelLatitude: 33.3Longitude: -111.666Data Version: VER2DryBulbTempWetBulbTempDewPointTempDateTime(LST)StationTypeSkyConditionsVisibility(SM)WeatherType(F)(C)(F)(C)(F)(C)RelHumd%WindSpeed(MPH)WindDirWindGusts(MPH)StationPressure(in. hg)PressTendNet3-hrChg(mb)SeaLevelPressure(in. hg)ReportTypePrecip.Total(in)Altimeter(in. hg)12345678910111213141516171819202122232828282828282828282828282828282828282828282828282828282828282800150035005501150135015502150235025503150335035504150435045505150547064707470847094710471147124713471447154716471747184719470000000000000000000000000000000CLRMCLRCLRCLRCLRCLRCLRCLRCLRCLRCLRCLRCLRCLRCLRFEW100 BKN250SCT150SCT150FEW150FEW200FEW170CLRCLRFEW150FEW150FEW120FEW120 FEW250FEW250FEW250CLR2.002.505.007.0010.0010.005.005.007.007.007.007.007.007.007.007.005.005.005.007.007.007.007.007.0020.0015.0015.0020.0030.0035.0020.00HZHZHZHZHZHZHZHZ9393919090909090909090909090909090909193979910210610610810810810810810234.034.033.032.032.032.032.032.032.032.032.032.032.032.032.032.032.032.033.034.036.037.039.041.041.042.042.042.042.042.039.0737371717172727272717171717171717272737374747474737372737373M22.922.921.721.521.522.122.122.122.121.521.521.521.521.521.521.522.122.422.622.923.223.523.323.422.922.722.422.722.722.7M6464616161636363636161616161616163646464636361595755545555555718.018.016.016.016.017.017.017.017.016.016.016.016.016.016.016.017.018.018.018.017.017.016.015.014.013.012.013.013.013.014.0383837383841414141383838383838384142413833312621201717171717M14181714138798811989765366553691191311810330330320320310320320340350360360330330330310310290VR250230210VRVR250270300300280300300280231628.4528.4528.4628.4628.4628.4628.4628.4628.4528.4528.4428.4528.4428.4428.4428.4428.4428.4628.4628.4628.4628.4528.4328.4028.3728.3428.3128.2928.2928.29MMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA29.9129.9129.9229.9329.9329.9329.9329.9229.9129.9129.9029.9129.9029.9029.9029.9029.9029.9229.9329.9329.9229.9129.8929.8629.8329.8029.7729.7529.7529.7529.77572828282828282828282828282819552015203520552115213521552215223522552315233523550000000000000CLRCLRCLRCLRCLRCLRCLRCLRCLRCLRCLRCLRCLR10.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.00100100100100100999797979790939038.038.038.038.038.037.036.036.036.036.032.034.032.07171717272707272727170717121.521.521.522.022.021.322.122.122.121.521.021.421.55555555757555959595759596113.013.013.014.014.013.015.015.015.014.015.015.016.0222222242423282828263532381188976603030030030030031028025025000004000014000000028.3128.3228.3228.3328.3328.3328.3328.3428.3428.3428.3428.3428.34MMMMMMMMMMMMMAAAAAAAAAAAAAAAAAAAAAAAAAA29.7729.7829.7829.7929.7929.7929.7929.8029.8029.8029.8029.8029.8058U.S. Department of CommerceNational Oceanic & Atmospheric AdministrationQUALITY CONTROLLED LOCALCLIMATOLOGICAL DATA(final)HOURLY OBSERVATIONS TABLECASA GRANDE MUNICIPAL ARPT (03914)CASA GRANDE, AZ(08/2011)National Climatic Data CenterFederal Building151 Patton AvenueAsheville, North Carolina 28801Elevation: 1462 ft. above sea levelLatitude: 32.95Longitude: -111.766Data Version: VER2DryBulbTempWetBulbTempDewPointTempDateTime(LST)StationTypeSkyConditionsVisibility(SM)WeatherType(F)(C)(F)(C)(F)(C)RelHumd%WindSpeed(MPH)WindDirWindGusts(MPH)StationPressure(in. hg)PressTendNet3-hrChg(mb)SeaLevelPressure(in. hg)ReportTypePrecip.Total(in)Altimeter(in. hg)12345678910111213141516171819202122232727272727272727272727272727272727272727272727272727272727272700150035005501150135015502150235025503150335035504150435045505150535055506150635065507150735075508150835085509150935095510150000000000000000000000000000000CLRCLRCLRCLRCLRCLRCLRCLRCLRCLRCLRCLRCLRCLRCLRCLRCLRCLRCLRCLRCLRCLRCLRCLRCLRCLRCLRCLRCLRCLRCLR10.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.008686888888868482828282828282828282818181828486869090919395979730.030.031.031.031.030.029.028.028.028.028.028.028.028.028.028.028.027.027.027.028.029.030.030.032.032.033.034.035.036.036.07069707070706968686868686868686868686868686970707171717272737220.920.321.221.221.220.920.520.220.220.220.220.220.220.220.220.220.220.020.020.020.220.520.920.921.521.521.722.022.322.622.16159616161616161616161616161616161616161616161616161616161615916.015.016.016.016.016.016.016.016.016.016.016.016.016.016.016.016.016.016.016.016.016.016.016.016.016.016.016.016.016.015.043404040404346494949494949494949495151514946434338383734323028000650000050003500005000360000000000000011009000000000000000006000000000010008000000000000013000000000017013000000000000000028.3228.3328.3328.3328.3328.3328.3328.3328.3228.3228.3228.3228.3228.3328.3428.3328.3328.3428.3428.3628.3628.3628.3728.3728.3728.3728.3728.3828.3828.3828.38722003003010MMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA29.8729.8829.8829.8829.8829.8829.8829.8829.8729.8729.8729.8729.8729.8829.8929.8829.8829.8929.8929.9129.9129.9129.9229.9229.9229.9229.9229.9329.9329.9329.935927272727272727272727272727272727272727272727272727272727272727272727272727272727271035105511151135115512151235125513151335135514151435145515151535155516151635165517151735175518151835185519151935195520152035205521152135215522152235225523152335235500000000000000000000000000000000000000000CLRCLRCLRCLRCLRCLRCLRCLRCLRCLRCLRCLRCLRCLRCLRCLRCLRCLRCLRCLRCLRCLRCLRCLRCLRCLRCLRCLRCLRCLRCLRCLRCLRCLRCLRCLRCLRCLRCLRCLRCLR10.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.002.5010.0010.008.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.005.006.00VCTSVCTSVCTSVCTSVCTS97979910010210010210410410610610610810810810910910910910910910910810810810299999188939393919090908890888836.036.037.038.039.038.039.040.040.041.041.041.042.042.042.043.043.043.043.043.043.043.042.042.042.039.037.037.033.031.034.034.034.033.032.032.032.031.032.031.031.0737373747474747475747474757574757575747474737372747171717371737273727271717071717122.622.622.923.123.323.123.323.123.623.423.423.423.623.623.123.823.823.823.323.323.322.822.722.423.121.821.821.822.621.822.622.022.622.322.121.521.521.221.521.821.8616161616161615961595959595957595959575757555554575557576463636163636361616161636316.016.016.016.016.016.016.015.016.015.015.015.015.015.014.015.015.015.014.014.014.013.013.012.014.013.014.014.018.017.017.016.017.017.017.016.016.016.016.017.017.030302928262826232421212120201920202018181817171719212525414337343739413838403843430003006761011907798131013697910222214139711899671014201500000000026000000026019023028025028000026028029026031025029032035034035035003004006022014011013017023026022024027027028028016201717323018232228.3828.3828.3728.3728.3628.3628.3528.3428.3328.3228.3128.3028.2828.2728.2528.2528.2528.2528.2428.2328.2228.2228.2528.2528.2428.2528.2528.2728.3028.3228.3228.3028.2928.3228.3228.3328.3228.3228.3228.3228.3327722003024030027007MMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA29.9329.9329.9229.9229.9129.9129.9029.8929.8829.8729.8629.8529.8329.8229.8029.8029.7929.7929.7829.7729.7629.7629.7929.7929.7829.8029.8029.8129.8529.8729.8729.8529.8429.8729.8729.8829.8729.8729.8729.8729.8860U.S. Department of CommerceNational Oceanic & Atmospheric AdministrationQUALITY CONTROLLED LOCALCLIMATOLOGICAL DATA(final)HOURLY OBSERVATIONS TABLECASA GRANDE MUNICIPAL ARPT (03914)CASA GRANDE, AZ(08/2011)National Climatic Data CenterFederal Building151 Patton AvenueAsheville, North Carolina 28801Elevation: 1462 ft. above sea levelLatitude: 32.95Longitude: -111.766Data Version: VER2DryBulbTempWetBulbTempDewPointTempDateTime(LST)StationTypeSkyConditionsVisibility(SM)WeatherType(F)(C)(F)(C)(F)(C)RelHumd%WindSpeed(MPH)WindDirWindGusts(MPH)StationPressure(in. hg)PressTendNet3-hrChg(mb)SeaLevelPressure(in. hg)ReportTypePrecip.Total(in)Altimeter(in. hg)12345678910111213141516171819202122232828282828282828282828282828282828282828282828282828282828282800150035005501150135015502150235025503150335035504150435045505150535055506150635065507150735075508150835085509150935095510150000000000000000000000000000000CLRCLRCLRCLRCLRCLRCLRCLRCLRCLRCLRCLRCLRCLRCLRCLRCLRCLRCLRCLRCLRCLRCLRCLRCLRCLRCLRCLRCLRCLRCLR6.009.007.009.001.503.009.0010.0010.0010.0010.0010.0010.0010.0010.008.006.007.008.0010.0010.0010.0010.0010.008.005.006.007.0010.0010.0010.008890909188888686868684848484828181818181818282848688909191919331.032.032.033.031.031.030.030.030.030.029.029.029.029.028.027.027.027.027.027.027.028.028.029.030.031.032.033.033.033.034.07069696871717070707069696969707070707069697070707172727272727321.220.420.420.121.821.820.920.920.920.920.520.520.520.520.821.021.021.021.020.620.620.820.821.221.522.122.122.322.322.322.66157575563636161616161616161636464646463636363636364636363636316.014.014.013.017.017.016.016.016.016.016.016.016.016.017.018.018.018.018.017.017.017.017.017.017.018.017.017.017.017.017.04033333043434343434346464646535656565654545353494645413939393716161311111110897630035530537777877305290290300320350360360010350350360210000000210230200200000210220190200210200190210210230000190232128.3428.3528.3628.3628.3728.3828.3728.3628.3628.3728.3728.3628.3628.3628.3628.3628.3628.3628.3728.3828.3928.3928.3928.3928.3828.3828.3828.3828.3828.3828.37272020007010MMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA29.8929.9029.9129.9129.9229.9329.9229.9129.9129.9229.9229.9129.9129.9129.9129.9129.9129.9129.9229.9329.9429.9429.9429.9429.9329.9329.9329.9329.9329.9329.92616228282828282828282828282828282828282828282828282828282828282828282828282828282828281035105511151135115512151235125513151335135514151435145515151535155516151635165517151735175518151835185519151935195520152035205521152135215522152235225523152335235500000000000000000000000000000000000000000CLRCLRCLRCLRCLRCLRCLRCLRCLRCLRCLRCLRCLRCLRCLRCLRCLRCLRCLRCLRCLRCLRCLRCLRCLRCLRCLRCLRCLRCLRCLRCLRCLRCLRCLRCLRCLRCLRCLRCLRCLR10.0010.0010.009.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.00959597979910010010010210410610610610610810810610610610610610410210210010099999797979595959393919190908835.035.036.036.037.038.038.038.039.040.041.041.041.041.042.042.041.041.041.041.041.040.039.039.038.038.037.037.036.036.036.035.035.035.034.034.033.033.032.032.031.0727273737374M72M7373737272737372737373M747372727271707070706969696868686868686722.322.322.622.622.923.0M22.0M22.622.922.922.422.422.722.722.422.822.822.8M23.122.822.322.022.021.821.321.021.021.020.720.720.720.120.119.820.019.919.919.3616161616161595757575757555555555557575757595957575757555555555555555454545555555416.016.016.016.016.016.015.014.014.014.014.014.013.013.013.013.013.014.014.014.014.015.015.014.014.014.014.013.013.013.013.013.013.013.012.012.012.013.013.013.012.0323230302928M24M2120201919171719202020M232423242425232424242626262727293031313100838111193981113136101014131515151414913131310131510111310705600000000270270270270260300320320290310270320300260270280250250260260260280270270270270270280280270270290280260000240230000000171816171620201828.3628.3628.3528.3528.3428.33M28.31M28.2928.2828.2728.2728.2528.2528.2428.2328.2228.2228.22M28.2128.2128.2128.2128.2228.2228.2328.2328.2428.2428.2528.2528.2528.2528.2528.2528.2528.2528.2528.2577722010027024003010MMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMAAAAAAAAAAAAAUTOAAAUTOAAAAAAAAAAAAAAAAAAAAAAAUTOAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA29.9129.9129.9029.9029.8929.8829.8729.8629.8629.8429.8329.8229.8129.8029.7929.7829.7729.7629.7629.7629.7529.7529.7529.7529.7529.7629.7629.7729.7729.7829.7829.7929.8029.7929.8029.8029.8029.8029.8029.8029.80

# Visibility Cameras

Visibility camera images were comp iled into time lapse photo graphy videos in order to visually show the

dust impacts on portions of Maricopa County on June 27. The animations are available online for each

event and or each of the visibility camera sites in Maricopa Count y. These views can be accessed using

the camera site codes SOMT (South Mountain), CA ME (Camelback Mountains), SUPM (Superstition

Mountains), ESMO (Estrella Mountai ns), and WHTM (White Tank Mountains). It should be noted that

these time lapse photography videos may requi re the installation of a mp4 viewer.

The video files can be accessed as follows:

http://www.phoenixvis.net/videos/mpeg4/xxxx_mmddyyyy.mp4

xxxx = 4-character site code (ie. SOMT)

mm = 2-character month (ie. 06)

dd = 2-character day (ie. 27)

yyyy = 4-character year (ie. 2012)

Conclusion

The information presented within this section has adequately demonstrated a clear causal relationship

between the emissions generated by uncontrollable natu ral events and the exceedances measured at the

monitors. The satellite images, time series graphs, and meteorological data tables provided in this section

show the temporal progression of the dust events from the developm ent of the thunderstorms, to the

increase in wind speeds, and to th e rise in PM10 concentrations. Th e combination of the PM10 and wind

data from Maricopa and Pinal counties shows the tr ansport of particulate ma tter from the south through

Pinal County and into the Phoenix PM10 nonattainment area. This information supports the conclusion

that the events were primarily dr awing from emission sources outside of Maricopa County and were being

transported into the Phoenix area.

63

# VI. “BUT FOR” ANALYSIS

Section 50.14(c)(3)(iv)(D) in 40 CF R part 50 requires that an excep tional event demonstration must

satisfy that “[t]here would have been no exceedance or violation but for the event.” The prior sections of

this submittal have provided detailed information that the exceedances during the period of August 25-28,

2011, were not reasonably c ontrollable or preventable and there is a clear causal relationship between

transported PM10 from thunderstorm outflows originating in the desert areas outside of the Phoenix

PM10 nonattainment area and the measured exceedances within the nonattainment area. The weight of

evidence in these sections demonstrates that but for the existence of emissions generated by these

thunderstorm outflows and associated transported PM10, there would have been no exceedances of the

24-Hour PM10 standard.

As detailed in Section IV, all r easonable control measures were in place and actively enforced before,

during, and after the exceedances of August 25-28, 2011. Inspection and compliance data of local

fugitive dust sources during this time period reveal ed that PM10 from anthropogenic activities was well

controlled and constant. Local regu latory agencies, industry, and the ge neral public were alerted to the

possibility of dust storms due to thunderstorm activity through daily forecasts and media reports.

Heightened, real-time surveillance of PM10 monitoring stations during th e events established a clear link

between rapidly rising PM10 concentrations and the ar rival of the thunderstorm outflows. On-the-ground

observations recorded during the even ts consistently identify transported or re-entrained PM10 as the

cause of the elevated concentratio ns near the exceeding monitors.

As shown in Section V, detailed, time series data establish a clear causal rela tionship between the arrival

of emissions generated by thunders torm outflows and elevated PM10 c oncentrations at the monitors.

Multiple, independent measurements of wind speed, wind di rection, and visibility a ll point to the presence

of thunderstorm outflows as the delivery vehicle fo r transported PM10 into the nonattainment area. Any

local PM10 generated during the arriva l of the thunderstorm out flows are linked to the turbulent and gusty

outflow front of the storm and pale in comparison to the amount of transporte d PM10 originating outside

the nonattainment area. The source regions for th e thunderstorm outflows and transported PM10 are

clearly identified as the de sert areas outside of the P hoenix PM10 nonattainment area.

The body of evidence presented in this submittal provide s no alternative that coul d tie the exceedances of

August 25-28, 2011 to any other causal source but tr ansported and re-entrain ed PM10 generated from

thunderstorm outflows, confirming th at there would have been no exceedances but for the presence of

these uncontrollable natural events.

64

# VII. CONCLUSIONS

The exceedances that occurred during August 25- 28, 2011, satisfy the following criteria of 40 CFR

50.1(j) and meet the definition of an exceptional event:

 The event affects air quality.

 The event is not reasonably controllable or preventable.

 The event is unlikely to reoccur at a partic ular location or [is] a natural event.

Affects Air Quality

As stated in the preamble to the Exceptional Events Rule, the event in question is considered to have

affected air quality if it can be shown that there is a clear causal relationship betwee n the monitored

exceedance and the event, and that the event is associ ated with a measured concentration in excess of

normal historical fluctuations. Gi ven the information presented in Sections 2, 3, 4, and 5, we can

reasonably conclude that the even t in question affected air quality.

Not Reasonably Controllable or Preventable

Section 50.1(j) of Title 40 CFR Part 50 requires that an event must be “not reasonably controllable or

preventable” in order to be define d as an exceptional event. This requirement is met by demonstrating

that, despite reasonable control measures in pl ace within Maricopa County and the Phoenix PM10

nonattainment area, high wind conditions overwhelmed all reasonably available controls. Despite the

deployment of comprehensive control measures and sophisticated response programs, high wind

conditions associated with thunderstorms and thunde rstorm outflows brought hi gh concentrations of

PM10 emissions into, and also overwhelmed controls within, the Phoenix PM10 nonattainment area. The

events discussed in this document that caused the exceed ances in this request (see Sections 2 and 5) were

caused by thunderstorm driven outflow winds that transported dus t into Maricopa County from areas

largely outside of the Phoenix PM10 nonattainment ar ea. The fact that thes e were natural events

involving strong thunderstorm outflow winds that tr ansported PM10 emissions into Maricopa County,

with a majority of the PM10 emissions recorded by Maricopa County area monitors coming from sources

outside of the Phoenix PM10 nonattainment area, provides strong evidence that the events and

exceedances of August 25-28, 2011 recorded within the nonattainment area were not reasonably

controllable or preventable.

Natural Event

As discussed above, the events shown to cause thes e exceedances were emissions of PM10 driven by high

winds caused by thunderstorm activity and related out flow boundaries during the period of August 25-28,

2011. The events therefore qualify as natural events.

Summary

In summary, the exceedances of the federal 24- hour PM10 standard on August 25, August 26, August 27,

and August 28, 2011, would not have occurred but for the monsoonal thunderstorm driven high winds and

windblown dust transport from areas largely outside the Phoenix PM10 nonattainment area, based on the

following weight of evidence:

 Graphs of PM10 at various Phoenix area monitors in Section V and the tables containing

meteorological data for representative NWS airpor t sites show that the timing of elevated PM10

events was consistent with decreased visi bility and high winds at the NWS sites.

65

# 66 V.  Visibility camera imagery discussed in Sec tion V indicates that la rge quantities of PM10 were

transported into the Phoenix Metro area during the August 26 th 

# event. The timing of the dust

storms depicted in the visibility camer a imagery is consistent with the PM10 concentration

measurements, elevated winds, and reduced visibility reported during the event.

 Historical Fluctuation analyses and graphs in Section III and Appendix A showing five years of

24-hour average data for each of the Phoenix PM 10 nonattainment area monitors depict numerous

atypically high PM10 concentrations during the third qua rter of 2011 including the period of

August 25-28. The sudden increase in the frequency of elevated PM10 concentrations during this

time period was exceptional from a historical perspective.

 Each of the exceedances of the PM10 standard recorded during th e period of August 25-28 are

tied to thunderstorm activity and th understorm generated outflow winds, as can be seen in data

and analyses in Section

 Figures and tables in Section V show that the timing of thunde rstorm-generated outflow boundary

passage and increases in wind speeds at monitoring locations and National Weather Service

stations during each of the events during this pe riod is consistent with the timing of elevated

PM10 concentrations recorded at the monitoring locations in the Phoenix PM10 nonattainment

area.

 Wind directions, thunderstorm-generated out flow boundary propagation, and concentration

patterns showing elevated levels of PM10 in Pinal County prior to leve ls increasing in Maricopa

County, all depicted in Section V, he lp show that a vast majority of the dust that impacted Phoenix

PM10 nonattainment area monitors originated in Pi nal County and other ar eas located generally

south of the Phoenix PM10 nonattainment area.

 Approximate PM10 emissions source flux calculations for se lect events are pr ovided in Section V

to give an idea of the magnitude of the dust storms that affect ed the Phoenix area and the amounts

of PM10 that can be transported in during these types of events.

 Section IV discusses rules that are in place in the Phoenix PM10 nonattainment area as well as

inspections that were conducted in the area to veri fy compliance with those rules in order to show

that the events are not reasonably controllable or preventable. Additionally, the visibility webcam

time lapse photography videos referenced in Section II also help illustrate the magnitude and scale

of these events, which supports the claim that the exceedances recorded during this period were

not reasonably controll able or preventable.

# APPENDIX A

5

- YEAR HISTORICAL FLUCTUATION GRAPHS FOR

THE PHOENIX PM10 NONATTAINMENT AREA MONITORING SITES

# APPENDIX B

ADEQ F ORECAST PRODUCTS FOR PHOENIX

, MARICOPA COUNTY , AND PINAL COUNTY

# MARICOPA COUNTY DUST CONTROL FORECAST

ISSUED WEDNESDAY, AUGUST 24, 2011

Three-day weather outlook:

DURING ACTIVE SUMMER MONSOON EPISODES STRONG GUSTY WINDS AND DENSE BLOWING DUST ARE

POSSIBLE, EVEN FROM DISTANT THUNDERSTORMS

Temperatures will decrease slightly each day through the weekend while the chances fo r showers and thunderstorms continue to

hover around 10-30% during this period. Daytime winds will remain fairly light. The chance for blowing dust from distant stor ms

will also continue into early next week. Thus, the risk of exceeding the 24-hr PM10 health standard in Phoenix will be

MODERATE each day through at least Monday.



# RISK FACTORS

WINDS STAGNATION UNHEALTHY PM-10

RISK LEVEL

Day 1: Thu 08/25/2011 Southwest winds

between 5 and 10 mph

are expected (10-20%

chance of showers and

t-storms). + Rather stagnant

conditions are likely

early, improving late. = 

# MODERATE

Day 2: Fri 08/26/2011 Southwest winds

between 5 and 10 mph

are expected (20-30%

chance of showers and

t-storms). + Rather stagnant

conditions are likely

early, improving late. = 

# MODERATE

Day 3: Sat 08/27/2011 Southwest winds

between 5 and 10 mph

are expected (20-30%

chance of showers and

t-storms). + Rather stagnant

conditions are likely

early, improving late. = 

# MODERATE

EXTENDED OUTLOOK

Day 4: Sun 08/28/2011 Southwest winds

between 5 and 10 mph

are expected (20-30%

chance of showers and

t-storms). + Rather stagnant

conditions are likely

early, improving late. = 

# MODERATE

Day 5: Mon 08/29/2011 Southwest winds

between 5 and 10 mph

are expected (20-30%

chance of showers and

t-storms). + Rather stagnant

conditions are likely

early, improving late. = 

# MODERATE

The Maricopa County Dust Control Ac tion Forecast is issued to assist in the planning of work activities

to help reduce dust pollution. A recorded message of this forecast can be accessed at 602-771-2368 . To

review the complete air quality fo recast for the Phoenix metropolitan ar ea, as well as the health impacts

and reduction methods for different air pollutants, call 602-771-2367 for recorded forecast information or

click on ADEQ's Air Quality Forecast at http://www.azdeq.gov/environ/air/ozone/ensemble.pdf

.

JRP 04/28/2011

# MARICOPA COUNTY DUST CONTROL FORECAST

ISSUED THURSDAY, AUGUST 25, 2011

Three-day weather outlook:

DURING ACTIVE SUMMER MONSOON EPISODES STRONG GUSTY WINDS AND DENSE BLOWING DUST ARE

POSSIBLE, EVEN FROM DISTANT THUNDERSTORMS

A dust storm that moved through the forecast area early Thursday morning has caused several monitors to exceed the PM10 health

standard for the day. Some of these particulates may carry ove r into Friday. In addition, there is a good possibility of some

additional dust from thunderstorm this even ing impacting the Phoenix forecast area. Concentrations should tail off a bit Satur day

through early next week as chances for more storms decreases. Thus, the risk of ex ceeding the 24-hr PM10 health standard in

Phoenix will be HIGH on Friday, decreasing to MODERATE Saturday through next Tuesday.



# RISK FACTORS

WINDS STAGNATION UNHEALTHY PM-10

RISK LEVEL

Day 1: Fri 08/26/2011 Southwest winds

between 5 and 10 mph

are expected (20-30%

chance of showers and

t-storms). + Rather stagnant

conditions are likely

early, improving late. = 

# HIGH

Day 2: Sat 08/27/2011 Southwest winds

between 5 and 10 mph

are expected (10-20%

chance of showers and

t-storms). + Rather stagnant

conditions are likely

early, improving late. = 

# MODERATE

Day 3: Sun 08/28/2011 Southwest winds

between 5 and 10 mph

are expected (10%

chance of showers and

t-storms). + Rather stagnant

conditions are likely

early, improving late. = 

# MODERATE

EXTENDED OUTLOOK

Day 4: Mon 08/29/2011 Southwest winds

between 5 and 10 mph

are expected (10-20%

chance of showers and

t-storms). + Rather stagnant

conditions are likely

early, improving late. = 

# MODERATE

Day 5: Tue 08/30/2011 Southwest winds

between 5 and 10 mph

are expected (20-30%

chance of showers and

t-storms). + Rather stagnant

conditions are likely

early, improving late. = 

# MODERATE

The Maricopa County Dust Control Ac tion Forecast is issued to assist in the planning of work activities

to help reduce dust pollution. A recorded message of this forecast can be accessed at 602-771-2368 . To

review the complete air quality fo recast for the Phoenix metropolitan ar ea, as well as the health impacts

and reduction methods for different air pollutants, call 602-771-2367 for recorded forecast information or

click on ADEQ's Air Quality Forecast at http://www.azdeq.gov/environ/air/ozone/ensemble.pdf

.

JRP 04/28/2011

# MARICOPA COUNTY DUST CONTROL FORECAST

ISSUED FRIDAY, AUGUST 26, 2011

Three-day weather outlook:

DURING ACTIVE SUMMER MONSOON EPISODES STRONG GUSTY WINDS AND DENSE BLOWING DUST ARE

POSSIBLE, EVEN FROM DISTANT THUNDERSTORMS

Afternoon desert temperatures w ill be near 110°F as high pressure holds on thr ough the weekend. By Monday and Tuesday, it

begins to weaken. This will allow temper atures to drop to 103°F by Thursday of ne xt week. We will also see a break in

thunderstorm activity Monday and Tuesday with somewhat drier air being pulled into th e region. The approaching trough of low

pressure could bring with it a chance for more showers and thun derstorms as it sweeps through the region. For now, the risk of

exceeding the 24-hr PM10 health standard in Phoenix due to blowing dust will be MODERATE on Saturday and Sunday, LOW

on Monday and Tuesday, and MODERATE again on Wednesday.



# RISK FACTORS

WINDS STAGNATION UNHEALTHY PM-10

RISK LEVEL

Day 1: Sat 08/27/2011 Southwest winds

between 5 and 10 mph

are expected (10-20%

chance of showers and

t-storms). + Rather stagnant

conditions are likely

early, improving late. = 

# MODERATE

Day 2: Sun 08/28/2011 Southwest winds

between 5 and 10 mph

are expected (10%

chance of showers and

t-storms). + Rather stagnant

conditions are likely

early, improving late. = 

# MODERATE

Day 3: Mon 08/29/2011 Southwest winds

between 5 and 10 mph

are expected (10%

chance of showers and

t-storms). + Rather stagnant

conditions are likely

early, improving late. = 

# LOW

EXTENDED OUTLOOK

Day 4: Tue 08/30/2011 Southwest winds

between 5 and 10 mph

are expected

(10%chance of showers

and t-storms). + Rather stagnant

conditions are likely

early, improving late. = 

# LOW

Day 5: Wed 08/31/2011 Southwest winds

between 5 and 10 mph

are expected (20-30%

chance of showers and

t-storms). + Rather stagnant

conditions are likely

early, improving late. = 

# MODERATE

The Maricopa County Dust Control Ac tion Forecast is issued to assist in the planning of work activities

to help reduce dust pollution. A recorded message of this forecast can be accessed at 602-771-2368 . To

review the complete air quality fo recast for the Phoenix metropolitan ar ea, as well as the health impacts

and reduction methods for different air pollutants, call 602-771-2367 for recorded forecast information or

click on ADEQ's Air Quality Forecast at http://www.azdeq.gov/environ/air/ozone/ensemble.pdf

.

JRP 04/28/2011

# MARICOPA COUNTY DUST CONTROL FORECAST

ISSUED SUNDAY, AUGUST 28, 2011

Five-day weather outlook:

DURING ACTIVE SUMMER MONSOON EPISODES STRONG GUSTY WINDS AND DENSE BLOWING DUST ARE

POSSIBLE EVEN FROM DISTANT THUNDERSTORMS

Although summer monsoon activity with signifi cant rainfall does not look likely for the Phoenix metro area proper the next few

days, there will continue to be a height ened potential for episodes of dense blowi ng dust generated by outflow boundaries from

thunderstorms east and southeast of the metro area. Low-level gradients and upslope flow will yield breezy to gusty conditions at

times each afternoon.



# RISK FACTORS

WINDS STAGNATION UNHEALTHY PM-10

RISK LEVEL

Day 1: Mon 08/29/2011 Westerly 10-20 mph

during the afternoon

except strong and gusty

due to outflow from

thunderstorms. + No significant

stagnation expected. = MODERATE

Day 2: Tue 08/30/2011 Westerly 10-20 mph

during the afternoon

except strong and gusty

due to outflow from

thunderstorms. + No significant

stagnation expected. = MODERATE

Day 3: Wed 08/31/2011 Westerly 5-15 mph

during the afternoon

except strong and gusty

due to outflow from

thunderstorms. + No significant

stagnation expected. = MODERATE

EXTENDED OUTLOOK

Day 4: Thu 09/01/2011 Westerly 5-15 mph

during the afternoon

except strong and gusty

due to outflow from

thunderstorms. + No significant

stagnation expected. = MODERATE

Day 5: Fri 09/02/2011 Westerly 5-15 mph

during the afternoon

except strong and gusty

due to outflow from

thunderstorms. + No significant

stagnation expected. = MODERATE



# The Maricopa County Dust Control Action Forecast is issued to assist in the planning of work activities to

help reduce dust pollution. A recorded message of this forecast can be accessed at 602-771-2368 . To review

the complete air quality forecast for the Phoenix metropolitan area, as well as the health impacts and

reduction methods for different air pollutants, call 602-771-2367 for recorded forecast information or click on

ADEQ's Air Quality Forecast at http://www.azdeq.gov/environ/air/oz one/ensemble.pdf

. CKR 04/28/2011

# VERY UNHEALTHY (201-300)

UNHEALTHY (151-200)

UNHEALTHY FOR SENSITIVE GROUPS (101-150)

MODERATE (51-100)

GOOD (0-50)

For more information visit:

http://www.airnow.gov/index.cfm?action=aqibasics.aqi

NEW!!! CLICK HERE FOR UPDATED OZONE SEASON STATS NEW!!!



# AIR QUALITY FORECAST FOR THURSDAY, AUGUST 25, 2011

This report is updated by 1:00 p.m. Sunday thru Friday and is valid

for areas within and bordering Maricopa County in Arizona

* O3 = Ozone CO = Carbon Monoxide PM-10 = Particles 10 microns & smaller PM-2.5 = Particles smaller than 2.5 micro ns



# *“ Ozone Health Watch ” means that the highest concentration of OZONE may approach the federal health standard.

“ PM-10 or PM-2.5 Health Watch ” means that the highest concentration of PM-10 or PM-2.5 may approach the federal health standard.

“ High Pollution Advisory ” means that the highest concentrati on of OZONE, PM-10, or PM-2.5 may exceed the federal health standard.

“ DUST ” means that short periods of high PM-10 concentrati ons caused by outflow from thunderstorms are possible. 

# FORECAST

DATE

NOTICES

(*SEE BELOW

FOR DETAILS)

AIR POLLUTANT 

# YESTERDAY

TUE 08/23/2011

Highest AQI Reading/Site

(Preliminary data only) 

# TODAY

WED 08/24/2011 

# TOMORROW

THU 08/25/2011

DUST

Possible 

# EXTENDED

FRI 08/26/2011

DUST

Possible



# O3* 80

HUMBOLDT

MOUNTAIN 

# 84

MODERATE 

# 87

MODERATE 

# 80

MODERATE



# CO* 7

GREENWOOD 

# 7

GOOD 

# 7

GOOD 

# 7

GOOD



# PM-10* 52

BUCKEYE 

# 42

GOOD 

# 77

MODERATE 

# 65

MODERATE



# PM-2.5* 29

ESTRELLA 

# 28

GOOD 

# 48

GOOD 

# 38

GOOD

# Health message for Wednesday, August 24: Unusually sensitive people should

consider limiting prolonged exertion outdoors.

Health message for Thursday, August 25: Unusually sensitive people should

consider limiting prolonged exertion outdoors.

Temperatures will peak today across the Valley with a forecasted high somewhere around 114-116°F.

This is well above normal for this time of year.

Questions have been asked recently about the relationship between temperature and ground-level

ozone. The short answer is: there isn’t one. Ozone fo rmation and peak concentrations at a given location is

very complex. First there needs to be abundant amounts of precursors (which apparently we don’t

currently have). Then there needs to be unimpeded, direct sunlight (which we do have). Wind speeds can

affect a developing ozone plume by mixing the air up. Light winds (which we currently have) promote

ozone formation. Then you must f actor in the wind direction, howeve r strong or weak that may be.

Models call for a slight southeast-to-northwest flow today and Thursday. This means that we can expect

the highest concentrations to be in the north-central part of the forecast area. Other factors to take into

account are the development of nearby thunderstorms. Such storm can climb to 40- 60,000 feet high. The

updrafts can draw air from valley floors, taking with it the pollution that is accumulating. This can result in

lower than potential ozone concentrations in the valley, such as the Phoenix metro area.

All the factors have played a ro le in the recent lower-than-poten tial ozone concentrations in the

Phoenix forecast area. We expect to see slightly high er concentrations today and Thursday in the north and

northeast part of the Valley. Cloud cover Friday morning may hold ozone production down a bit, resulting

in lower overall concentrations.

PM10 levels climbed into the lower MODERATE range at the Buckeye and Durango monitors on

Tuesday. There really hasn’t been much wind to cause the elevated levels. This raises a valid concern that

the Valley soil is not as stable as we would like it to be and the threat of blowing dust from distant and even

localized thunderstorms could send PM10 concentrations deep into the MODERATE category or even into

UNHEALTHY FOR SENSITIVE GROUPS territory sometime in the next week. Such events are very

difficult to accurately predict, but we’ve raised the PM10 forecast to cover the possibilit y on Thursday.

Check back tomorrow for more. Until then, have a good day! -J.Paul

MONITORING SITE MAPS

STATIC MAP http://www.azdeq.gov/environ/ai r/monitoring/images/map.jpg

http://aqwww.maricopa.gov/AirMonitoring/SitePollutionMap.aspx INTERACTIVE MAPS http://www.airnow.gov/



# POLLUTION MONITOR READINGS FOR T UESDAY, AUGUST 23, 2011



# O3 (OZONE)

Info on current 8-hour ozone standard: http://www.epa.gov/air/ozonepollution/pdfs/2008_03_aqi_changes.pdf

For archived AQI maps go to: http://www.airnow.gov/index.cfm?action=airnow.maps

SITE NAME MAX 8-HR VALUE (PPB) MAX AQI AQI COLOR CODE

Alamo Lake (La Paz County) 

# NOT AVBL NOT AVBL NOT AVBL

Apache Junction (Pinal County) 

# 58 49

Blue Point 63 61

Buckeye 47 40

Casa Grande 49 42

Cave Creek 68 77

Central Phoenix 60 51

Dysart 52 44

Falcon Field 59 50

Fountain Hills 63 61

Glendale 53 45

# Humboldt Mountain 69 80

North Phoenix 67 74

Phoenix Supersite 63 61

Pinal Air Park (Pinal County) 

# 67 74

Pinnacle Peak 52 44

Queen Valley (Pinal County) 61 54

Rio Verde 65 67

South Phoenix 59 50

South Scottsdale 63 61

Tempe 55 47

Tonto Nat’l Mon. (Gila County) 

# 57 48

West Chandler 56 47

West Phoenix 61 54

Yuma NOT AVBL NOT AVBL NOT AVBL



# CO (CARBON MONOXIDE)

SITE NAME MAX 8-HR VALUE (PPM) MAX AQI AQI COLOR CODE

Central Phoenix 0.3 3

Greenwood 0.6 7

West Phoenix 0.4 5



# PM-10 (PARTICLES)

SITE NAME MAX 24-HR VALUE (μg/m3) 

# MAX AQI AQI COLOR CODE

Buckeye 57.1 52 HIGHEST LOCALLY



# Central Phoenix 45.2 41

Combs School (Pinal County) 

# 70.5 58

Durango 56.0 51

Dysart 31.7 29

Glendale 35.8 33

Greenwood 42.3 39

Higley 38.1 35

Maricopa (Pinal County) 52.1 48

Phoenix Supersite 37.6 34

South Phoenix 43.0 39

West Chandler 36.1 33

West Forty Third 47.5 43

West Phoenix 49.7 45

Zuni Hills 30.0 27



# PM-2.5 (PARTICLES)

(Some data derived from light-scattering equipment)



# For maps go to: http://www.airnow.gov /

SITE NAME MAX 24-HR VALUE (μg/m3) 

# MAX AQI AQI COLOR CODE

Durango 8.3 27

Dysart 5.0 16

Estrella Mountain Park 8.9 29

Glendale 8.1 26

Phoenix Supersite 8.6 28

North Phoenix 7.8 25

South Phoenix 6.3 20

Vehicle Emissions Lab NOT AVBL NOT AVBL NOT AVBL



# West Phoenix 7.9 26

# LOCAL AIR POLLUTANTS IN DETAIL

O3 (OZONE) :

Description – This is a secondary pollutant that is formed by the reaction of other primary

pollutants (precursors) such as VOCs (v olatile o rganic c ompounds) and NOx (N itrogen Ox ides)

in the presence of heat and sunlight.

Sources – VOCs are emitted from motor vehicles, chemical plants, refineries, factories, and

other industrial sources. NOx is emitted from motor vehicles, power plants, and other sources of

combustion.

Potential health impacts – Exposure to ozone can make people more susceptible to respiratory

infection, result in lung inflammation, and aggr avate pre-existing respiratory diseases such as

asthma. Other effects include decrease in lung fu nction, chest pain, and cough.

Unit of measurement – Parts per billion (ppb).

Averaging interval – Highest eight-hour period within a 24-hour period (midnight to midnight).

Reduction tips – Curtail daytime driving, refuel cars an d use gasoline-powered equipment as late

in the day as possible.



# CO (CARBON MONOXIDE) :

Description – A colorless, odorless, poisonous gas formed when carbon in fuels is not burned

completely.

Sources – In cities, as much as 95 percent of all CO emissions emanate from automobile exhaust.

Other sources include industrial processes, non-transportation fuel combustion, and natural

sources such as wildfires. Pe ak concentrations occur in colder winter months.

Potential health impacts – Reduces oxygen delivery to the body’s organs and tissues. The health

threat is most serious for those who suff er from cardiovascular disease.

Unit of measurement – Parts per million (ppm).

Averaging interval – Highest eight-hour period within a 24-hour period (midnight to midnight)

Reduction tips – Keep motor vehicle tuned properly and minimize nighttime driving.



# PM-10 & PM-2.5 (PARTICLES) :

Description – The term “particulate matter” (PM) includes both solid particles and liquid droplets

found in air. Many manmade and natural sources emit PM directly or emit other pollutants that

react in the atmosphere to form PM. Particles le ss than 10 micrometers in diameter tend to pose

the greatest health concern because they can be inhaled into and accumulate in the respiratory

system. Particles less than 2.5 micrometers in diameter are referred to as “fine” particles and are

responsible for many visibility degradations such as the “Valley Brown Cloud” (see

http://www.phoenixvis.net/ ). Particles with diameters between 2.5 and 10 micrometers are referred

to as “coarse”.

Sources – Fine = All types of combustion (motor vehicles, power plants, wood burning, etc.) and

some industrial processes. Coarse = crushing or grinding operations and dust from paved or

unpaved roads.

Potential health impacts – PM can increase susceptibility to respiratory infections and can

aggravate existing respiratory diseases, such as asthma and chronic bronchitis.

Units of measurement – Micrograms per cubic meter (ug/m3)

Averaging interval – 24 hours (midnight to midnight).

# Reduction tips – Stabilize loose soils, slow down on dirt ro ads, carpool, and use public transit.

{ Updated 03/23/2010 }

# VERY UNHEALTHY (201-300)

UNHEALTHY (151-200)

UNHEALTHY FOR SENSITIVE GROUPS (101-150)

MODERATE (51-100)

GOOD (0-50)

For more information visit:

http://www.airnow.gov/index.cfm?action=aqibasics.aqi

NEW!!! CLICK HERE FOR UPDATED OZONE SEASON STATS NEW!!!



# AIR QUALITY FORECAST FO R FRIDAY, AUGUST 26, 2011

This report is updated by 1:00 p.m. Sunday thru Friday and is valid

for areas within and bordering Maricopa County in Arizona

* O3 = Ozone CO = Carbon Monoxide PM-10 = Particles 10 microns & smaller PM-2.5 = Particles smaller than 2.5 micro ns



# *“ Ozone Health Watch ” means that the highest concentration of OZONE may approach the federal health standard.

“ PM-10 or PM-2.5 Health Watch ” means that the highest concentration of PM-10 or PM-2.5 may approach the federal health standard.

“ High Pollution Advisory ” means that the highest concentrati on of OZONE, PM-10, or PM-2.5 may exceed the federal health standard.

“ DUST ” means that short periods of high PM-10 concentrati ons caused by outflow from thunderstorms are possible. 

# FORECAST

DATE

NOTICES

(*SEE BELOW

FOR DETAILS)

AIR POLLUTANT 

# YESTERDAY

WED 08/24/2011

Highest AQI Reading/Site

(Preliminary data only) 

# TODAY

THU 08/25/2011

(Ozone and PM10)

DUST 

# TOMORROW

FRI 08/26/2011

(PM10) (Ozone)

DUST 

# EXTENDED

SAT 08/27/2011

DUST



# O3* 97

QUEEN VALLEY 

# 106

UNHEALTHY for

SENSITIVE

GROUPS 

# 93

MODERATE 

# 80

MODERATE



# CO* 7

GREENWOOD 

# 7

GOOD 

# 7

GOOD 

# 7

GOOD



# PM-10* 57

BUCKEYE 

# 250

VERY

UNHEATHY 

# 125

UNHEALTHY for

SENSITIVE

GROUPS 

# 65

MODERATE



# PM-2.5* 32

ESTRELLA

MOUNTAIN PARK 

# 48

GOOD 

# 45

GOOD 

# 38

GOOD

# Health message for Thursday, August 25: People with respiratory disease, such as

asthma, should avoid any outdoor activity; everyone else, especially the elderly and

children, should limit outdoor exertion.

Health message for Friday, August 26: People with respiratory disease, such as

asthma, should limit outdoor exertion.

...SAME DAY PM10 AND OZONE HIGH POLLUTION ADVISORY FOR THURSDAY, AUGUST 25, 2011...

...THURSDAY’S PM10 HPA IS BEING EXTENDED THROUGH FRIDAY, AUGUST 26, 2011...

...AN OZONE HEALTH WATCH IS BEING I SSUED THROUGH FRIDAY, AUGUST 26, 2011...



# An area of disturbance in the stealth of the night generated a wall of dust that pushed northwest from

north of Tucson through Pinal County (Casa Grande ), settling out in northwestern Maricopa County.

That’s a path of more 130 miles. It took just over 4 hours for the wall of dust to move through. In its

wake, nearly all of Pinal County’s PM10 monitors and several more of Maricopa County’s monitors

exceeded the health standard. This occurred between 1-2am this morning. Even if every hour from now

until midnight registered completely clean air, the 24-hr average still exceeds. Thus, we have issued a

PM10 High Pollution Advisory for Thursday . There’s not much anyone can do to prevent something

that has already happened, but there is plenty they can do to keep it from becoming worse as well as

protecting their healthy by avoiding outdoor exposure today.

Ozone levels were in the 90s of the Air Quality Index (AQI) at several forecast area monitors on

Thursday as well. That wall of dust that brought all of the particulates also imported some ozone as well.

Many Valley monitors are starting 10 to 20 parts per b illion (ppb) higher than 24 h ours earlier. As the sun

comes out, addition ozone will be generated, likely pushing some parts over the Valley above the health

standard for ozone, as well. Thus, we have also issued a same-day Ozone HPA for Thursday

. Models are suggesting that we have an increased chance for some showers/thunderstorms moving in

tonight from the southeast. Along with this possib ility comes the likelihood of more blowing dust. This

will likely add to today’s totals for PM10. The hold over of lingering dust Friday morning could be enough

to push some Valley monitors over the edge once more. So... we are EXTENDING today PM10 HPA

through Friday. Cloud cover Friday morning along with a sustained southeast-to-northwest flow should

result in slightly lower Ozone levels, but we are issuing an Ozone Health Watch for Friday with the

target area of highest concentrations in the north-central part of the forecast area.

Check back tomorrow for the weekend outlook. Until then, have a good day! -J.Paul

MONITORING SITE MAPS

STATIC MAP http://www.azdeq.gov/environ/ai r/monitoring/images/map.jpg

http://aqwww.maricopa.gov/AirMonitoring/SitePollutionMap.aspx INTERACTIVE MAPS http://www.airnow.gov/



# POLLUTION MONITOR READINGS FOR T UESDAY, AUGUST 23, 2011



# O3 (OZONE)

Info on current 8-hour ozone standard: http://www.epa.gov/air/ozonepollution/pdfs/2008_03_aqi_changes.pdf

For archived AQI maps go to: http://www.airnow.gov/index.cfm?action=airnow.maps

SITE NAME MAX 8-HR VALUE (PPB) MAX AQI AQI COLOR CODE

Alamo Lake (La Paz County) 

# 56 47

Apache Junction (Pinal County) 

# 66 71

Blue Point 72 90

Buckeye 47 40

Casa Grande 52 44

Cave Creek 73 93

Central Phoenix 60 51

Dysart 54 46

Falcon Field 64 64

# Fountain Hills 71 87

Glendale 56 47

Humboldt Mountain 73 93

North Phoenix 68 77

Phoenix Supersite 63 61

Pinal Air Park (Pinal County) 

# 53 45

Pinnacle Peak 65 67

Queen Valley (Pinal County) 74 97

Rio Verde 70 84

South Phoenix 58 49

South Scottsdale 65 67

Tempe 56 47

Tonto Nat’l Mon. (Gila County) 

# 65 67

West Chandler 63 61

West Phoenix 59 50

Yuma NOT AVBL NOT AVBL NOT AVBL



# CO (CARBON MONOXIDE)

SITE NAME MAX 8-HR VALUE (PPM) MAX AQI AQI COLOR CODE

Central Phoenix 0.3 3

Greenwood 0.6 7

West Phoenix 0.4 5



# PM-10 (PARTICLES)

SITE NAME MAX 24-HR VALUE (μg/m3) 

# MAX AQI AQI COLOR CODE

Buckeye 67.9 57

Central Phoenix 40.4 37

Combs School (Pinal County) 

# 60.5 53

Durango 52.0 47

Dysart 34.7 32

Glendale 38.5 35

Greenwood 41.3 38

Higley 37.7 34

Maricopa (Pinal County) 62.8 54

Phoenix Supersite 37.7 34

South Phoenix 48.3 44

West Chandler 39.6 36

West Forty Third 47.7 43

West Phoenix 45.1 41

Zuni Hills 31.9 29



# PM-2.5 (PARTICLES)

(Some data derived from light-scattering equipment)



# For maps go to: http://www.airnow.gov /

SITE NAME MAX 24-HR VALUE (μg/m3) 

# MAX AQI AQI COLOR CODE

Durango 8.3 27

Dysart 5.5 18

Estrella Mountain Park 9.8 32

Glendale 9.1 30

Phoenix Supersite 7.6 25

North Phoenix 6.9 22

South Phoenix 6.7 22

Vehicle Emissions Lab NOT AVBL NOT AVBL NOT AVBL

# West Phoenix 7.6 25



# LOCAL AIR POLLUTANTS IN DETAIL

O3 (OZONE) :

Description – This is a secondary pollutant that is formed by the reaction of other primary

pollutants (precursors) such as VOCs (v olatile o rganic c ompounds) and NOx (N itrogen Ox ides)

in the presence of heat and sunlight.

Sources – VOCs are emitted from motor vehicles, chemical plants, refineries, factories, and

other industrial sources. NOx is emitted from motor vehicles, power plants, and other sources of

combustion.

Potential health impacts – Exposure to ozone can make people more susceptible to respiratory

infection, result in lung inflammation, and aggr avate pre-existing respiratory diseases such as

asthma. Other effects include decrease in lung fu nction, chest pain, and cough.

Unit of measurement – Parts per billion (ppb).

Averaging interval – Highest eight-hour period within a 24-hour period (midnight to midnight).

Reduction tips – Curtail daytime driving, refuel cars an d use gasoline-powered equipment as late

in the day as possible.



# CO (CARBON MONOXIDE) :

Description – A colorless, odorless, poisonous gas formed when carbon in fuels is not burned

completely.

Sources – In cities, as much as 95 percent of all CO emissions emanate from automobile exhaust.

Other sources include industrial processes, non-transportation fuel combustion, and natural

sources such as wildfires. Pe ak concentrations occur in colder winter months.

Potential health impacts – Reduces oxygen delivery to the body’s organs and tissues. The health

threat is most serious for those who suff er from cardiovascular disease.

Unit of measurement – Parts per million (ppm).

Averaging interval – Highest eight-hour period within a 24-hour period (midnight to midnight)

Reduction tips – Keep motor vehicle tuned properly and minimize nighttime driving.



# PM-10 & PM-2.5 (PARTICLES) :

Description – The term “particulate matter” (PM) includes both solid particles and liquid droplets

found in air. Many manmade and natural sources emit PM directly or emit other pollutants that

react in the atmosphere to form PM. Particles le ss than 10 micrometers in diameter tend to pose

the greatest health concern because they can be inhaled into and accumulate in the respiratory

system. Particles less than 2.5 micrometers in diameter are referred to as “fine” particles and are

responsible for many visibility degradations such as the “Valley Brown Cloud” (see

http://www.phoenixvis.net/ ). Particles with diameters between 2.5 and 10 micrometers are referred

to as “coarse”.

Sources – Fine = All types of combustion (motor vehicles, power plants, wood burning, etc.) and

some industrial processes. Coarse = crushing or grinding operations and dust from paved or

unpaved roads.

Potential health impacts – PM can increase susceptibility to respiratory infections and can

aggravate existing respiratory diseases, such as asthma and chronic bronchitis.

# Units of measurement – Micrograms per cubic meter (ug/m3)

Averaging interval – 24 hours (midnight to midnight).

Reduction tips – Stabilize loose soils, slow down on dirt ro ads, carpool, and use public transit.

{ Updated 03/23/2010 }

# VERY UNHEALTHY (201-300)

UNHEALTHY (151-200)

UNHEALTHY FOR SENSITIVE GROUPS (101-150)

MODERATE (51-100)

GOOD (0-50)

For more information visit:

http://www.airnow.gov/index.cfm?action=aqibasics.aqi

NEW!!! CLICK HERE FOR UPDATED OZONE SEASON STATS NEW!!!



# AIR QUALITY FORECAST FO R SATURDAY, AUGUST 27, 2011

This report is updated by 1:00 p.m. Sunday thru Friday and is valid

for areas within and bordering Maricopa County in Arizona

* O3 = Ozone CO = Carbon Monoxide PM-10 = Particles 10 microns & smaller PM-2.5 = Particles smaller than 2.5 micro ns



# *“Ozone Health Watch ” means that the highest concentration of OZONE may approach the federal health standard.

“PM-10 or PM-2.5 Health Watch ” means that the highest concentration of PM-10 or PM-2.5 may approach the federal health standard.

“High Pollution Advisory ” means that the highest concentration of OZONE, PM-10, or PM-2.5 may exceed the federal health standard.

“DUST ” means that short periods of high PM-10 concentrati ons caused by outflow from thunderstorms are possible. 

# FORECAST

DATE

NOTICES

(*SEE BELOW

FOR DETAILS)

AIR POLLUTANT 

# YESTERDAY

THU 08/25/2011

(Ozone and PM10)

DUST

Highest AQI Reading/Site

(Preliminary data only) 

# TODAY

FRI 08/26/2011

(PM10) (Ozone)

DUST 

# TOMORROW

SAT 08/27/2011

(Ozone)

DUST 

# EXTENDED

SUN 08/28/2011



# O3* 122

PHOENIX SUPERSITE 

# 93

MODERATE 

# 93

MODERATE 

# 77

MODERATE



# CO* 5

GREENWOOD 

# 7

GOOD 

# 7

GOOD 

# 7

GOOD



# PM-10* 316

DURANGO 

# 125

UNHEALTHY for

SENSITIVE

GROUPS 

# 65

MODERATE 

# 56

MODERATE



# PM-2.5* 111

DURANGO 

# 45

GOOD 

# 38

GOOD 

# 35

GOOD

# Health message for Friday, August 26: People with respiratory disease, such as

asthma, should limit outdoor exertion.

Health message for Saturday, August 27: Unusually Sensitive People should

consider limiting prolonged exertion outdoors.

...A PM10 HIGH POLLUTION ADVISORY REMAINS IN EFFECT FOR FRIDAY, AUGUST 26, 2011...

FRIDAY’S OZONE HEALTH WATCH HAS BEEN EXTENDED THROUGH SATURDAY, AUGUST 27, 2011



# The results are in for yesterday’s air quality levels, and their pretty eye opening. That early morning

dust storm caused all but one site to exceed the 24-hr PM10 health standard. Not only that, but Durango’s

monitor registered levels in the code BROWN category, which is HAZARDOUS. That’s incredible.

Durango’s PM2.5 monitor was the only one to exceed that standard as well, but several others got close,

reaching the upper MODERATE range. Ozone levels ex ceeded at six monitors with Phoenix Supersite

(17th avenue and Campbell) reaching 122 on the Air Qua lity Index (AQI). Overall, it was not a good day

to be outside in the Phoenix metro area (not to mention the 113°F heat!)

Many ozone monitors are at or below where they were yesterday. A few are slightly higher. The good

news is that the rate of increase has slowed. We have an Ozone Health Watch in place for today with the

highest concentrations expected to be in the north and northwest part of the Valley, around Cave Creek,

Glendale, North Phoenix, and Dysart. Tomorrow’s pattern and levels will be similar to today, so we are

extending that Health Watch through Saturday. With high pressure breaking down Sunday through next

week, we will see a shift in winds out of the southwest. This will not only drop our thunderstorm chances,

but also help decrease local ozone levels.

The dust has cleared out nicely as mostly monito rs are now showing PM10 concentrations in the

GOOD range. We still have the PM10 HPA in place fo r today, but that will be allowed to expire at

midnight with no further extension.

The latest WRF-RUC model suggests thunderstorms will develop over the Valley tonight around 8pm.

If it does happen, that would be a good thing as rain will clear the air and stabilize the soil. It’s only when

the storm originate outside of the Valley th e concern of significant dust is raised.

Check back on Sunday for the week end wrap up and a look ahead at next week’s weather and air

quality. Until then, have a good day! -J.Paul

MONITORING SITE MAPS

STATIC MAP http://www.azdeq.gov/environ/ai r/monitoring/images/map.jpg

http://aqwww.maricopa.gov/AirMonitoring/SitePollutionMap.aspx INTERACTIVE MAPS http://www.airnow.gov/



# POLLUTION MONITOR READINGS FOR THURSDAY, AUGUST 24, 2011



# O3 (OZONE)

Info on current 8-hour ozone standard: http://www.epa.gov/air/ozonepollution/pdfs/2008_03_aqi_changes.pdf

For archived AQI maps go to: http://www.airnow.gov/index.cfm?action=airnow.maps

SITE NAME MAX 8-HR VALUE (PPB) MAX AQI AQI COLOR CODE

Alamo Lake (La Paz County) 

# NOT AVBL NOT AVBL NOT AVBL

Apache Junction (Pinal County) 

# 64 64

Blue Point 75 100

Buckeye 64 64

Casa Grande 64 64

Cave Creek 82 116

Central Phoenix 71 87

Dysart 74 97

Falcon Field 68 77

Fountain Hills 77 104

Glendale 82 116

# Humboldt Mountain 73 93

North Phoenix 82 116

Phoenix Supersite 84 122

Pinal Air Park (Pinal County) 

# 68 77

Pinnacle Peak 73 93

Queen Valley (Pinal County) 69 80

Rio Verde 72 90

South Phoenix 74 97

South Scottsdale 71 87

Tempe 62 58

Tonto Nat’l Mon. (Gila County) 

# NOT AVBL NOT AVBL NOT AVBL



# West Chandler 67 74

West Phoenix 80 111

Yuma 53 45



# CO (CARBON MONOXIDE)

SITE NAME MAX 8-HR VALUE (PPM) MAX AQI AQI COLOR CODE

Central Phoenix 0.2 2

Greenwood 0.4 5

West Phoenix 0.3 3



# PM-10 (PARTICLES)

SITE NAME MAX 24-HR VALUE (μg/m3) 

# MAX AQI AQI COLOR CODE

Buckeye 235.9 141

Central Phoenix 308.7 178

Combs School (Pinal County) 

# 60.1 53

Durango 437.5 316

Dysart 273.7 160

Glendale 241.2 144

Greenwood 388.6 250

Higley 131.4 89

Maricopa (Pinal County) 529.3 425

Phoenix Supersite 242.2 144

South Phoenix 421.5 296

West Chandler 278.6 163

West Forty Third 370.3 223

West Phoenix 212.6 130

Zuni Hills 212.8 130



# PM-2.5 (PARTICLES)

(Some data derived from light-scattering equipment)



# For maps go to: http://www.airnow.gov /

SITE NAME MAX 24-HR VALUE (μg/m3) 

# MAX AQI AQI COLOR CODE

Durango 39.4 111

Dysart 17.9 57

Estrella Mountain Park 22.5 68

Glendale 24.1 72

Phoenix Supersite 33.0 94

North Phoenix 9.6 31

South Phoenix 23.7 71

Vehicle Emissions Lab NOT AVBL NOT AVBL NOT AVBL



# West Phoenix 31.6 91

# LOCAL AIR POLLUTANTS IN DETAIL

O3 (OZONE) :

Description – This is a secondary pollutant that is formed by the reaction of other primary

pollutants (precursors) such as VOCs (v olatile o rganic c ompounds) and NOx (N itrogen Ox ides)

in the presence of heat and sunlight.

Sources – VOCs are emitted from motor vehicles, chemical plants, refineries, factories, and

other industrial sources. NOx is emitted from motor vehicles, power plants, and other sources of

combustion.

Potential health impacts – Exposure to ozone can make people more susceptible to respiratory

infection, result in lung inflammation, and aggr avate pre-existing respiratory diseases such as

asthma. Other effects include decrease in lung fu nction, chest pain, and cough.

Unit of measurement – Parts per billion (ppb).

Averaging interval – Highest eight-hour period within a 24-hour period (midnight to midnight).

Reduction tips – Curtail daytime driving, refuel cars an d use gasoline-powered equipment as late

in the day as possible.



# CO (CARBON MONOXIDE) :

Description – A colorless, odorless, poisonous gas formed when carbon in fuels is not burned

completely.

Sources – In cities, as much as 95 percent of all CO emissions emanate from automobile exhaust.

Other sources include industrial processes, non-transportation fuel combustion, and natural

sources such as wildfires. Pe ak concentrations occur in colder winter months.

Potential health impacts – Reduces oxygen delivery to the body’s organs and tissues. The health

threat is most serious for those who suff er from cardiovascular disease.

Unit of measurement – Parts per million (ppm).

Averaging interval – Highest eight-hour period within a 24-hour period (midnight to midnight)

Reduction tips – Keep motor vehicle tuned properly and minimize nighttime driving.



# PM-10 & PM-2.5 (PARTICLES) :

Description – The term “particulate matter” (PM) includes both solid particles and liquid droplets

found in air. Many manmade and natural sources emit PM directly or emit other pollutants that

react in the atmosphere to form PM. Particles le ss than 10 micrometers in diameter tend to pose

the greatest health concern because they can be inhaled into and accumulate in the respiratory

system. Particles less than 2.5 micrometers in diameter are referred to as “fine” particles and are

responsible for many visibility degradations such as the “Valley Brown Cloud” (see

http://www.phoenixvis.net/ ). Particles with diameters between 2.5 and 10 micrometers are referred

to as “coarse”.

Sources – Fine = All types of combustion (motor vehicles, power plants, wood burning, etc.) and

some industrial processes. Coarse = crushing or grinding operations and dust from paved or

unpaved roads.

Potential health impacts – PM can increase susceptibility to respiratory infections and can

aggravate existing respiratory diseases, such as asthma and chronic bronchitis.

Units of measurement – Micrograms per cubic meter (ug/m3)

Averaging interval – 24 hours (midnight to midnight).

# Reduction tips – Stabilize loose soils, slow down on dirt ro ads, carpool, and use public transit.

{ Updated 03/23/2010 }

# VERY UNHEALTHY (201-300)

UNHEALTHY (151-200)

UNHEALTHY FOR SENSITIVE GROUPS (101-150)

MODERATE (51-100)

GOOD (0-50)

For more information visit:

http://www.airnow.gov/index.cfm?action=aqibasics.aqi

NEW!!! CLICK HERE FOR UPDATED OZONE SEASON STATS NEW!!!



# AIR QUALITY FORECAST FOR MONDAY, AUGUST 29, 2011

This report is updated by 1:00 p.m. Sunday thru Friday and is valid

for areas within and bordering Maricopa County in Arizona

* O3 = Ozone CO = Carbon Monoxide PM-10 = Particles 10 microns & smaller PM-2.5 = Particles smaller than 2.5 micro ns



# *“ Ozone Health Watch ” means that the highest concentration of OZONE may approach the federal health standard.

“ PM-10 or PM-2.5 Health Watch ” means that the highest concentration of PM-10 or PM-2.5 may approach the federal health standard.

“ High Pollution Advisory ” means that the highest concentrati on of OZONE, PM-10, or PM-2.5 may exceed the federal health standard.

“ DUST ” means that short periods of high PM-10 concentrati ons caused by outflow from thunderstorms are possible. 

# FORECAST

DATE

NOTICES

(*SEE BELOW

FOR DETAILS)

AIR POLLUTANT 

# YESTERDAY

SAT 08/27/2011

OZONE HEALTH

WATCH

DUST

NWS EXCESSIVE

HEAT WARNING

Highest AQI Reading/Site

(Preliminary data only) 

# TODAY

SUN 08/28/2011

PM-10 HEALTH

WATCH

DUST

NWS EXCESSIVE

HEAT WARNING 

# TOMORROW

MON 08/29/2011

DUST

NWS EXCESSIVE

HEAT WARNING 

# EXTENDED

TUE 08/30/2011

DUST



# O3* 90

CAVE CREEK 

# 77

MODERATE 

# 80

MODERATE 

# 80

MODERATE



# CO* 05

GREENWOOD 

# 07

GOOD 

# 06

GOOD 

# 06

GOOD



# PM-10* 174

SOUTH PHOENIX 

# 95

MODERATE 

# 75

MODERATE 

# 75

MODERATE



# PM-2.5* 119

DURANGO 

# 35

GOOD 

# 50

GOOD 

# 44

GOOD

# Health message for Sunday August 28: Unusually sensitive people should consider reducing

prolonged or heavy exertion outdoors.

Health message for Monday August 29: Unusually sensitive people should consider reducing

prolonged or heavy exertion outdoors.



# Synopsis and Discussion

OZONE: Hot daytime temperatures and minimal cloud cover will promote above average ozone production the next

few days. However, a low-leve l westerly wind regime will help to keep ozone accumulation at below average levels

thru Tuesday. As a result, expect highest local ozone levels in the mi d to upper-moderate range of the Air Quality

Index to occur over the east Valley thru this forecast period.

PARTICLES: A PM-10 HEALTH WATCH HAS BEEN ISSUED FOR THE REMAINDER OF TODAY



# Due to lingering suspended dust from last evening’s wind event, at 9:00 a.m. this morning hourly PM-10

concentrations around the Valley ranged from 40ug/m3 at Buckeye to 148ug/m3 at Central Phoenix. This has

prompted the issuance of a PM-10 Health Watch for the remainder of today. Alth ough summer monsoon activity with

significant rainfall does not look likely for the Phoenix metro area proper the next few days, there will continue to be a

heightened potential for similar episodes of dense blow ing dust generated by outflow boundaries from thunderstorms

east and southeast of the metro area. Low-level gradients an d upslope flow will yield br eezy to gusty conditions at

times each afternoon.

MONITORING SITE MAPS: STATIC MAP

- http://www.azdeq.gov/environ/air/monitoring/images/map.jpg

INTERACTIVE MAPS - http://aqwww.maricopa.gov/AirM onit oring/SitePollutionMap.aspx

http://www.airnow.gov /



# POLLUTION MONITOR READINGS FOR SATURDAY, AUGUST 27, 2011



# O3 (OZONE)

Info on current 8-hour ozone standard: http://www.epa.gov/air/ozonepo llut ion/pdfs/2008_03_aqi_changes.pdf

For archived AQI maps go to: http://www.airnow.gov/index.cfm?action=airnow.maps

SITE NAME MAX 8-HR VALUE (PPB) MAX AQI AQI COLOR CODE

Alamo Lake (La Paz County) 62 58

Apache Junction (Pinal County) 62 58

Blue Point 64 64

Buckeye 58 49

Casa Grande (Pinal County) 58 49

Cave Creek 72 90

Central Phoenix 65 67

Dysart 61 54

Falcon Field 64 64

Fountain Hills 69 80

Glendale 67 74

Humboldt Mountain 65 67

North Phoenix 71 87

Phoenix Supersite 71 87

Pinal Air Park (Pinal County) 56 47

Pinnacle Peak 64 64

Queen Valley (Pinal County) 67 74

Rio Verde 64 64

South Phoenix 64 64

South Scottsdale 65 67

Tempe 58 49

Tonto Nat’l Mon. (Gila County) 61 54

West Chandler 61 54

West Phoenix 68 77

Yuma (Yuma County) NOT AVBL NOT AVBL NOT AVBL

# CO (CARBON MONOXIDE)

SITE NAME MAX 8-HR VALUE (PPM) MAX AQI AQI COLOR CODE

Central Phoenix 0.2 02

Greenwood 0.4 05

Phoenix Supersite NOT AVBL NOT AVBL NOT AVBL

West Phoenix 0.3 03



# PM-10 (PARTICLES)

SITE NAME MAX 24-HR VALUE (ug/m3) MAX AQI AQI COLOR CODE

Buckeye 226 136

Central Phoenix 234 140

Combs School(Pinal County NOT AVBL NOT AVBL NOT AVBL

Durango 261 154

Dysart 126 86

Glendale 220 130

Greenwood 208 127

Higley 115 81

Maricopa (Pinal County) NOT AVBL NOT AVBL NOT AVBL

Phoenix Supersite 132 89

South Phoenix 301 174

West Chandler 229 138

West Forty Third 292 169

West Phoenix 164 105

Zuni Hills 112 79



# PM-2.5 (PARTICLES)

(Some data derived from light-scattering equipment)



# For maps go to: http://www.airnow.gov /

SITE NAME MAX 24-HR VALUE (ug/m3) MAX AQI AQI COLOR CODE

Durango 43.0 119

Dysart 11.7 38

Estrella Mountain Park 21.5 66

Glendale 42.7 119

Phoenix Supersite 21.9 67

South Phoenix 30.6 88

Vehicle Emissions Lab 18.9 59

West Phoenix 24.6 73

# LOCAL AIR POLLUTANTS IN DETAIL

O3 (OZONE) :

Description – This is a secondary pollutant that is formed by the reaction of other primary

pollutants (precursors) such as VOCs (v olatile o rganic c ompounds) and NOx (N itrogen Ox ides)

in the presence of heat and sunlight.

Sources – VOCs are emitted from motor vehicles, chemical plants, refineries, factories, and

other industrial sources. NOx is emitted from motor vehicles, power plants, and other sources of

combustion.

Potential health impacts – Exposure to ozone can make people more susceptible to respiratory

infection, result in lung inflammation, and aggr avate pre-existing respiratory diseases such as

asthma. Other effects include decrease in lung fu nction, chest pain, and cough.

Unit of measurement – Parts per billion (ppb).

Averaging interval – Highest eight-hour period within a 24-hour period (midnight to midnight).

Reduction tips – Curtail daytime driving, refuel cars an d use gasoline-powered equipment as late

in the day as possible.



# CO (CARBON MONOXIDE) :

Description – A colorless, odorless, poisonous gas formed when carbon in fuels is not burned

completely.

Sources – In cities, as much as 95 percent of all CO emissions emanate from automobile exhaust.

Other sources include industrial processes, non-transportation fuel combustion, and natural

sources such as wildfires. Pe ak concentrations occur in colder winter months.

Potential health impacts – Reduces oxygen delivery to the body’s organs and tissues. The health

threat is most serious for those who suff er from cardiovascular disease.

Unit of measurement – Parts per million (ppm).

Averaging interval – Highest eight-hour period within a 24-hour period (midnight to midnight)

Reduction tips – Keep motor vehicle tuned properly and minimize nighttime driving.



# PM-10 & PM-2.5 (PARTICLES) :

Description – The term “particulate matter” (PM) includes both solid particles and liquid droplets

found in air. Many manmade and natural sources emit PM directly or emit other pollutants that

react in the atmosphere to form PM. Particles le ss than 10 micrometers in diameter tend to pose

the greatest health concern because they can be inhaled into and accumulate in the respiratory

system. Particles less than 2.5 micrometers in diameter are referred to as “fine” particles and are

responsible for many visibility degradations such as the “Valley Brown Cloud” (see

http://www.phoenixvis.net/ ). Particles with diameters between 2.5 and 10 micrometers are referred

to as “coarse”.

Sources – Fine = All types of combustion (motor vehicles, power plants, wood burning, etc.) and

some industrial processes. Coarse = crushing or grinding operations and dust from paved or

unpaved roads.

Potential health impacts – PM can increase susceptibility to respiratory infections and can

aggravate existing respiratory diseases, such as asthma and chronic bronchitis.

Units of measurement – Micrograms per cubic meter (ug/m3)

Averaging interval – 24 hours (midnight to midnight).

Reduction tips – Stabilize loose soils, slow down on dirt roads, carpool, and us e public transit.

{ Updated 03/23/2010 }

# FORECAST

GOOD (0-50) MODERATE (51-100) UNHEALTHY FOR

SENSITIVE GROUPS

(101-150) UNHEALTHY

(151-200) VERY UNHEALTHY

(201-300) HAZARDOUS

(301-500)



# AIR QUALITY FORECAST FOR

THURSDAY, AUGUST 25, 2011

This forecast is updated by 1:00 p.m. M onday through Friday and as needed

(AQI Forecast on Twitter – see tables below for location specific Twitters )

Valid for areas within Pinal County Arizona

Highest AQI value/Site

in Pinal County 

# Highest AQI forecasted value

(see tables below for forecasts by monitoring location)

YESTERDAY

TUE 8/23/11 TODAY

WED 8/24/11 TOMORROW

THU 8/25/11 EXTENDED

FRI 8/26/11 EXTENDED

SAT 8/27/11

OZONE 49

APACHE JUNCTION 70

MODERATE 55

MODERATE 52

MODERATE 55

MODERATE

PM-10* 58**

SAN TAN VALLEY 67**

MODERATE 85**

MODERATE 80**

MODERATE 60**

MODERATE

HEALTH

WATCH/

ADVISORY NONE NONE DUST DUST NONE

*PM-10 = Particles 10 microns and smaller

**Excludes Cowtown monitor. See follo wing page for Cowtown forecast.

“Ozone Health Watch ” means that the highest concen tration of OZONE may approach the federal health standard.

“PM-10 Health Watch ” means that the highest concentration of PM-10 may approach the federal health standard.

“High Pollution Advisory ” (HPA) means that the highest concentra tion of OZONE or PM-10 may exceed the

federal health standard.

“DUST ” means that short periods of high PM-10 concentrations caused by outflow from thunderstorms are possible.



# Health message for Thursday, August 25, 2011: Active children, adults and people with

lung disease, such as asthma, should co nsider reducing prolonged or heavy exertion

outdoors.

# Discussion

Updated Wednesday, August 24, 2011 at 11:35 a.m.

The strong high pressure aloft will continue to bring record or near-record

temperatures to the region the next several days. Yesterday’s high temperature in Casa

Grande was 111 degrees!

A few minor weather disturbances will pass through during the ThursdaySaturday timeframe. No local rain is expected however storm development (and

associated strong outflow winds ) to the south and east of Pi nal County may create areas

of blowing dust that may make their way into the count y. Therefore the PM 10 

# forecast has

been increased into the mi ddle and upper range of the m oderate AQI category for

Thursday and Friday.

The ozone levels should reach the good to low moderate range of the AQI scale

the next few days.

Everyone is encouraged to limit outdoor activities during the heat of the day and

drink plenty of water. Check back tomo rrow for an updated air quality forecast.

Forecaster – S. DiBiase



# COWTOWN

(Twitter: Cowtown_AQI )

YESTERDAY

TUE 8/23/11 TODAY’S

AQI FORECAST

WED 8/24/11 TOMORROW

AQI FORECAST

THU 8/25/11 EXTENDED

AQI FORECAST

FRI 8/26/11 EXTENDED

AQI FORECAST

SAT 8/27/11

PM-10* 99 105 110 115 105

MONITORING NETWORK MAP YESTERDAY’S AQI LEVELS



# AIR QUALITY FORECAST BY LOCATION FOR



# PM-10 (PARTICLES)

SITE NAME TODAY’S

AQI

FORECAST

WED 8/24/11 TOMORROW

AQI

FORECAST

THU 8/25/11 EXTENDED

AQI

FORECAST

FRI 8/26/11 EXTENDED

AQI

FORECAST

SAT 8/27/11

Casa Grande (Twitter: CG_AQI ) 50 55 55 45

Eleven Mile Corner

(Twitter: PC_Housing_AQI ) 50 75 70 48

Maricopa (Twitter:

MaricopaCity_AQ ) 52 60 60 50

San Tan Valley

(Twitter: Santan_AQI ) 52 65 60 50

Stanfield

(Twitter: Stanfield_AQI ) 67 85 80 60

# OZONE*

SITE NAME TODAY’S

AQI FORECAST

WED 8/24/11 TOMORROW

AQI FORECAST

THU 8/25/11 EXTENDED

AQI FORECAST

FRI 8/26/11 EXTENDED

AQI FORECAST

SAT 8/27/11

Apache Junction

(Twitter: AJ_AQI ) 70 55 50 50

Casa Grande

(Twitter: CG_AQI ) 50 49 50 50

Pinal Air Park

(Twitter:

PC_Airpark_AQI ) 50 50 52 55



# AIR POLLUTANTS IN DETAIL

PM-10 & PM-2.5 (PARTICLES):

Description – The term “particulate matter” (P M) includes both solid particles and

liquid droplets found in air. Many manmade and natural sources emit PM directly or

emit other pollutants that react in the atmosphere to form PM. Particles less than 10

micrometers in diameter tend to pose the greatest health concern because they can be

inhaled into and accumulate in the respiratory system. Particles less than 2.5

micrometers in diameter are referred to as “fine” particles a nd are responsible for

many visibility degradations such as the “Valley Brown Cloud” (see

http://www.phoenixvis.net/). Particles with diameters between 2.5 and 10

micrometers are referred to as “coarse”.

Sources – Fine = All types of combustion (m otor vehicles, pow er plants, wood

burning, etc.) and some industrial processes. Coarse = crushing or grinding operations

and dust from paved or unpaved roads.

Potential health impacts – PM can increase susceptibility to respiratory infections

and can aggravate existing respiratory di seases, such as asthma and chronic

bronchitis.

Units of measurement – Micrograms per cubic meter (ug/m 3 

# )

Averaging interval – 24 hours (midnight to midnight).

Reduction tips – Stabilize loose soils, slow down on dirt roads and carpool.

O 3 

# OZONE:

Description – This is a secondary pollutant that is formed by the reaction of other

primary pollutants (precursors) such as VOCs (volatile organic compounds) and NOx

(Nitrogen Oxides) in the presence of heat and sunlight. The ozone “season” generally

occurs during the spring and summer months (April-October) when high temperatures

and extended daylight hours create the condi tions most conducive to ozone formation.

Sources – VOCs are emitted from motor vehicl es, chemical plants, refineries,

factories, and other industrial sources. NOx is emitted from motor vehicles, power

plants, and other so urces of combustion.

Potential health impacts – Exposure to ozone can make people more susceptible to

respiratory infection, result in lung in flammation, and aggravate pre-existing

respiratory diseases such as asthma. Othe r effects include decr ease in lung function,

chest pain, and cough.

# Unit of measurement – Parts per billion (ppb).

Averaging interval – Highest eight-hour period with in a 24-hour period (midnight to

midnight).

Reduction tips – Curtail daytime driving, refu el cars and use gasoline-powered

equipment as late in the day as possible.

# FORECAST

GOOD (0-50) MODERATE (51-100) UNHEALTHY FOR

SENSITIVE GROUPS

(101-150) UNHEALTHY

(151-200) VERY UNHEALTHY

(201-300) HAZARDOUS

(301-500)



# AIR QUALITY FORECAST FOR

FRIDAY, AUGUST 26, 2011

This forecast is updated by 1:00 p.m. M onday through Friday and as needed

(AQI Forecast on Twitter – see tables below for location specific Twitters )

Valid for areas within Pinal County Arizona

Highest AQI value/Site

in Pinal County 

# Highest AQI forecasted value

(see tables below for forecasts by monitoring location)

YESTERDAY

WED 8/24/11 TODAY

THU 8/25/11 TOMORROW

FRI 8/26/11 EXTENDED

SAT 8/27/11 EXTENDED

SUN 8/28/11

OZONE 71

APACHE JUNCTION 55

MODERATE 53

MODERATE 52

MODERATE 53

MODERATE

PM-10* 78**

STANFIELD 165**

UNHEALTHY 75**

MODERATE 60**

MODERATE 60**

MODERATE

HEALTH

WATCH/

ADVISORY NONE HIGH

POLLUTION

ADVISORY DUST NONE NONE

*PM-10 = Particles 10 microns and smaller

**Excludes Cowtown monitor. See follo wing page for Cowtown forecast.

“Ozone Health Watch ” means that the highest concen tration of OZONE may approach the federal health standard.

“PM-10 Health Watch ” means that the highest concentration of PM-10 may approach the federal health standard.

“High Pollution Advisory ” (HPA) means that the highest concentra tion of OZONE or PM-10 may exceed the

federal health standard.

“DUST ” means that short periods of high PM-10 concentrations caused by outflow from thunderstorms are possible.



# Health message for Friday, August 26, 2011: Active children, adults and people with lung

disease, such as asthma, should consider reduc ing prolonged or heavy exertion outdoors.

# Discussion

Updated Thursday, August 25, 2011 at 11:30 a.m.

*** PM10 HIGH POLLUTION ADVISORY (HPA) IN EFFECT

THURSDAY AUGUST 25, 2011 ***

Blowing dust from thunderstorm outfl ows during the early morning hours

Thursday resulted in several of Pina l County monitors recording high PM 10 

# readings.

Several sites already exceed the 24 hour National Ambient Air Quality Standard in the

western half of Pinal County. Therefore, a PM 10 

# High Pollution Advisory (HPA) is in

effect for the remainder of today. Thunderstorm activity is possible again this afternoon

and evening adding onto the already elevat ed particulate matter concentrations.

For Friday the chance for thunderstorms remain in the forecast but with slightly

lower chances. The PM10 HPA will not be exte nded into Friday. Wind blown dust is still

a possibility during the afternoon and evening hours. Strong hi gh pressure will remain in

place and continue to bring n ear-record high temperatures. Oz one is expected to remain

in the Good to Moderate range of the AQI scale.

Anyone with respiratory and/or heart ailments should limit outdoor activities

today in order to reduce health im pacts due to the high levels of PM 10 

# . Forecaster – M.

Sundblom



# COWTOWN

(Twitter: Cowtown_AQI )

YESTERDAY

WED 8/24/11 TODAY

AQI FORECAST

THU 8/25/11 TOMORROW

AQI FORECAST

FRI 8/26/11 EXTENDED

AQI FORECAST

SAT 8/27/11 EXTENDED

AQI FORECAST

SUN 8/28/11

PM-10* 142 375 115 105 105

MONITORING NETWORK MAP YESTERDAY’S AQI LEVELS



# AIR QUALITY FORECAST BY LOCATION FOR



# PM-10 (PARTICLES)

SITE NAME TODAY’S

AQI

FORECAST

THU 8/25/11 TOMORROW

AQI

FORECAST

FRI 8/26/11 EXTENDED

AQI

FORECAST

SAT 8/27/11 EXTENDED

AQI

FORECAST

SUN 8/28/11

Casa Grande (Twitter: CG_AQI ) 120 52 45 45

Eleven Mile Corner

(Twitter: PC_Housing_AQI ) 110 54 48 48

Maricopa (Twitter:

MaricopaCity_AQ ) 165 57 50 50

San Tan Valley

(Twitter: Santan_AQI ) 65 54 50 50

Stanfield

(Twitter: Stanfield_AQI ) 110 75 60 60

# OZONE*

SITE NAME TODAY’S

AQI FORECAST

THU 8/25/11 TOMORROW

AQI FORECAST

FRI 8/26/11 EXTENDED

AQI FORECAST

SAT 8/27/11 EXTENDED

AQI FORECAST

SUN 8/28/11

Apache Junction

(Twitter: AJ_AQI ) 55 53 52 53

Casa Grande

(Twitter: CG_AQI ) 49 47 50 50

Pinal Air Park

(Twitter:

PC_Airpark_AQI ) 50 45 45 50



# AIR POLLUTANTS IN DETAIL

PM-10 & PM-2.5 (PARTICLES):

Description – The term “particulate matter” (P M) includes both solid particles and

liquid droplets found in air. Many manmade and natural sources emit PM directly or

emit other pollutants that react in the atmosphere to form PM. Particles less than 10

micrometers in diameter tend to pose the greatest health concern because they can be

inhaled into and accumulate in the respiratory system. Particles less than 2.5

micrometers in diameter are referred to as “fine” particles a nd are responsible for

many visibility degradations such as the “Valley Brown Cloud” (see

http://www.phoenixvis.net/). Particles with diameters between 2.5 and 10

micrometers are referred to as “coarse”.

Sources – Fine = All types of combustion (m otor vehicles, pow er plants, wood

burning, etc.) and some industrial processes. Coarse = crushing or grinding operations

and dust from paved or unpaved roads.

Potential health impacts – PM can increase susceptibility to respiratory infections

and can aggravate existing respiratory di seases, such as asthma and chronic

bronchitis.

Units of measurement – Micrograms per cubic meter (ug/m 3 

# )

Averaging interval – 24 hours (midnight to midnight).

Reduction tips – Stabilize loose soils, slow down on dirt roads and carpool.

O 3 

# OZONE:

Description – This is a secondary pollutant that is formed by the reaction of other

primary pollutants (precursors) such as VOCs (volatile organic compounds) and NOx

(Nitrogen Oxides) in the presence of heat and sunlight. The ozone “season” generally

occurs during the spring and summer months (April-October) when high temperatures

and extended daylight hours create the condi tions most conducive to ozone formation.

Sources – VOCs are emitted from motor vehicl es, chemical plants, refineries,

factories, and other industrial sources. NOx is emitted from motor vehicles, power

plants, and other so urces of combustion.

# Potential health impacts – Exposure to ozone can make people more susceptible to

respiratory infection, result in lung in flammation, and aggravate pre-existing

respiratory diseases such as asthma. Othe r effects include decr ease in lung function,

chest pain, and cough.

Unit of measurement – Parts per billion (ppb).

Averaging interval – Highest eight-hour period with in a 24-hour period (midnight to

midnight).

Reduction tips – Curtail daytime driving, refu el cars and use gasoline-powered

equipment as late in the day as possible.

# FORECAST

GOOD (0-50) MODERATE (51-100) UNHEALTHY FOR

SENSITIVE GROUPS

(101-150) UNHEALTHY

(151-200) VERY UNHEALTHY

(201-300) HAZARDOUS

(301-500)



# AIR QUALITY FORECAST FOR

SATURDAY, AUGUST 27 THROUGH

MONDAY, AUGUST 29, 2011

This forecast is updated by 1:00 p.m. M onday through Friday and as needed

(AQI Forecast on Twitter – see tables below for location specific Twitters )

Valid for areas within Pinal County Arizona

Highest AQI value/Site

in Pinal County 

# Highest AQI forecasted value

(see tables below for forecasts by monitoring location)

YESTERDAY

THU 8/25/11 TODAY

FRI 8/26/11 TOMORROW

SAT 8/27/11 EXTENDED

SUN 8/28/11 EXTENDED

MON 8/29/11

OZONE 77

PINAL AIR PARK 53

MODERATE 52

MODERATE 53

MODERATE 55

MODERATE

PM-10* 425**

MARICOPA 155**

UNHEALTHY 70**

MODERATE 60**

MODERATE 65**

MODERATE

HEALTH

WATCH/

ADVISORY PM 10 

# HPA

DUST PM 10 

# HPA

DUST NONE NONE NONE

*PM-10 = Particles 10 microns and smaller

**Excludes Cowtown monitor. See follo wing page for Cowtown forecast.

“Ozone Health Watch ” means that the highest concen tration of OZONE may approach the federal health standard.

“PM-10 Health Watch ” means that the highest concentration of PM-10 may approach the federal health standard.

“High Pollution Advisory ” (HPA) means that the highest concentra tion of OZONE or PM-10 may exceed the

federal health standard.

“DUST ” means that short periods of high PM-10 concentrations caused by outflow from thunderstorms are possible.



# Health message for Saturday, Augu st 27 through Monday, August 29, 2011: Active

children, adults and people with lung diseas e, such as asthma, should consider reducing

prolonged or heavy exertion outdoors.

# Discussion

Updated Friday, August 26, 2011 at 11:15 a.m.

*** PM 10 

# High Pollution Advisory (HPA) in effect

for the remainder of Friday August 26, 2011 ***

Blowing dust from thunderstorm out flows in Pima County during the

overnight/early morning hours Thursday a nd again on Thursday evening resulted in

several of Pinal County monitors exceeding the PM 10 

# health standard. Both the Cowtown

and Maricopa monitors reached the Hazardous level on the AQI scale.

Unfortunately today will also be an active day weather- wise, especially to our

south and east. More storm outflows and blow ing dust are likely today; therefore a same

day PM 10 

# High Pollution Advisory (HPA) is bei ng issued for the remainder of Friday.

Anyone with respiratory and/or heart ailments should limit outdoor activities

today in order to reduce health im pacts due to the high levels of PM 10



# . Saturday and Sunday will feature lower chances at storm development and

blowing dust. The PM 10 

# levels will range from upper good to mid moderate range of the

AQI scale with slightly lower levels of ozone expected. Forecaster – S. DiBiase



# COWTOWN

(Twitter: Cowtown_AQI )

YESTERDAY

THU 8/25/11 TODAY

AQI FORECAST

FRI 8/26/11 TOMORROW

AQI FORECAST

SAT 8/27/11 EXTENDED

AQI FORECAST

SUN 8/28/11 EXTENDED

AQI FORECAST

MON 8/29/11

PM-10* 889 155 105 115 105

MONITORING NETWORK MAP YESTERDAY’S AQI LEVELS



# AIR QUALITY FORECAST BY LOCATION FOR



# PM-10 (PARTICLES)

SITE NAME TODAY

AQI

FORECAST

FRI 8/26/11 TOMORROW

AQI

FORECAST

SAT 8/27/11 EXTENDED

AQI

FORECAST

SUN 8/28/11 EXTENDED

AQI

FORECAST

MON 8/29/11

Casa Grande (Twitter: CG_AQI ) 110 55 50 52

Eleven Mile Corner

(Twitter: PC_Housing_AQI ) 110 55 48 50

Maricopa (Twitter:

MaricopaCity_AQ ) 150 55 50 50

San Tan Valley

(Twitter: Santan_AQI ) 100 55 50 55

Stanfield

(Twitter: Stanfield_AQI ) 155 70 60 65

# OZONE*

SITE NAME TODAY

AQI FORECAST

FRI 8/26/11 TOMORROW

AQI FORECAST

SAT 8/27/11 EXTENDED

AQI FORECAST

SUN 8/28/11 EXTENDED

AQI FORECAST

MON 8/29/11

Apache Junction

(Twitter: AJ_AQI ) 53 52 53 55

Casa Grande

(Twitter: CG_AQI ) 47 52 50 50

Pinal Air Park

(Twitter:

PC_Airpark_AQI ) 45 52 50 49



# AIR POLLUTANTS IN DETAIL

PM-10 & PM-2.5 (PARTICLES):

Description – The term “particulate matter” (P M) includes both solid particles and

liquid droplets found in air. Many manmade and natural sources emit PM directly or

emit other pollutants that react in the atmosphere to form PM. Particles less than 10

micrometers in diameter tend to pose the greatest health concern because they can be

inhaled into and accumulate in the respiratory system. Particles less than 2.5

micrometers in diameter are referred to as “fine” particles a nd are responsible for

many visibility degradations such as the “Valley Brown Cloud” (see

http://www.phoenixvis.net/). Particles with diameters between 2.5 and 10

micrometers are referred to as “coarse”.

Sources – Fine = All types of combustion (m otor vehicles, pow er plants, wood

burning, etc.) and some industrial processes. Coarse = crushing or grinding operations

and dust from paved or unpaved roads.

Potential health impacts – PM can increase susceptibility to respiratory infections

and can aggravate existing respiratory di seases, such as asthma and chronic

bronchitis.

Units of measurement – Micrograms per cubic meter (ug/m 3 

# )

Averaging interval – 24 hours (midnight to midnight).

Reduction tips – Stabilize loose soils, slow down on dirt roads and carpool.

O 3 

# OZONE:

Description – This is a secondary pollutant that is formed by the reaction of other

primary pollutants (precursors) such as VOCs (volatile organic compounds) and NOx

(Nitrogen Oxides) in the presence of heat and sunlight. The ozone “season” generally

occurs during the spring and summer months (April-October) when high temperatures

and extended daylight hours create the condi tions most conducive to ozone formation.

Sources – VOCs are emitted from motor vehicl es, chemical plants, refineries,

factories, and other industrial sources. NOx is emitted from motor vehicles, power

plants, and other so urces of combustion.

Potential health impacts – Exposure to ozone can make people more susceptible to

respiratory infection, result in lung in flammation, and aggravate pre-existing

respiratory diseases such as asthma. Othe r effects include decr ease in lung function,

chest pain, and cough.

# Unit of measurement – Parts per billion (ppb).

Averaging interval – Highest eight-hour period with in a 24-hour period (midnight to

midnight).

Reduction tips – Curtail daytime driving, refu el cars and use gasoline-powered

equipment as late in the day as possible.

# APPENDIX C

NOTICE OF PUBLIC COMMENT PERIOD

# Request for Public Comments on Exception al Events in the Greater Phoenix Area

In 2005, Congress identified a need to account fo r events that result in exceedances of the

National Ambient Air Quality Standards (NAAQS) that are exceptional in nature (e.g., not

expected to reoccur or caused by acts of nature beyond man-made controls.) In response, EPA

promulgated the Exceptional Events Rule (EER) to address exceptional events in 40 CFR Parts

50 and 51 on March 22, 2007 (72 FR 13560). On May 2, 2011, EPA released draft guidance

documents on the implementation of the EER to Stat e, tribal and local air agencies for review.

The EER allows for states and tribes to “flag” air quality monitoring data as an exceptional

event. If flagged, these data can be excluded from consideration in air quality planning if EPA

concurs with the demonstration submitted by the flagging agency documenting that all

procedural and technical re quirements have been met.

Pursuant to 40 CFR 50.14(c)(3)(i) , the Arizona Department of E nvironmental Quality (ADEQ) is

soliciting comments on its final demonstrations of events that have caused elevated

concentrations of PM 10 

# in the Greater Phoenix area on February 19; July 18; August 3; August

18; August 25 through 28; September 2; Octobe r 4; November 4, 2011; January 21 – 22 and

February 27, 2012. ADEQ has decided to flag thes e episodes based on these analyses. Copies of

the demonstrations are available for review beginning Monday, December 3, 2012, on the ADEQ

website at www.azdeq.gov/environ/air/plan/ . Interested parties can submit written comments

throughout the comment period which will end at 5:00 p.m. on Tuesday, January 1, 2013. Any

comments received will be responded to and forwar ded to EPA with the final demonstrations.

Written comments should be addressed, faxed, or e-mailed to:

Andra Juniel, Air Assessment Section, Arizona Department of Environmental Quality, 1110 W.

Washington Street, 3415-A, Phoenix, AZ 85007, PHONE: (602) 771-4417; FAX: (602) 771-

2366, E-mail: juniel.andra@azdeq.gov.

In addition to being available on-line, copies of the analyses are available for review, Monday

through Friday, 8:30 a.m. to 4:30 p.m., at the ADEQ Records Center , 1110 W. Washington St.,

Phoenix, AZ, 85007, Attn: David Olivo, (602) 771-4380, email: olivo.david@azdeq.gov.

Persons with a disability may request reasonabl e accommodations by contacting Linda Morrison

at (602) 771-4793 or 1-800-234-5677 ext. 771-4793. Th is document is available in alternative

formats by contacting ADEQ TDD phone number at (602) 771-4829.

# APPENDIX D

NATIONAL WEATHER SERVICE FORECASTS,

WARNINGS, AND ALERTS