# State of Arizona

Exceptional Event Documentation

for the Event of September 6, 2012,

for the Phoenix PM 10 

# Nonattainment Area

Final Report prepared for

Arizona Department of Environmental Quality

Phoenix, AZ

February 2013

# This PDF document contains blank pages to accommodate two-sided printing.

# State of Arizona

Exceptional Event Documentation

for the Event of September 6, 2012,

for the Phoenix PM 10 

# Nonattainment Area

Final Report

STI-912098-5572-FR



# Prepared by

Daniel Alrick

Angela Ekstrand

Briana Gordon

Hilary Hafner

Clinton MacDonald

Hilary Minor

Ashley Russell

Sonoma Technology, Inc.

1455 N. McDowell Blvd., Suite D

Petaluma, CA 94954-6503

Ph 707.665.9900 | F 707.665.9800

sonomatech.com



# Prepared for

Theresa Rigney

Air Quality Assessment Section Manager

1110 W. Washington Street

Phoenix, AZ 85007

602.771.2274

February 13, 2013

Cover ima ge depicts widespread blowing dust associated with thunderstorm outflow causing reduced visibilities in the

Phoenix area 1755 LST on September 6, 2012.

# Exceptional Event, Phoenix, September 6, 2012 Acknowledgments



# Acknowledgments

The authors would like to acknowledge the Arizona Department of Environmental Quality

for helpful discussion and feedback during the preparation of this document.

iii

# Exceptional Event, Phoenix, Septem ber 6, 2012 Table of Contents



# Table of Contents

Section Page

Acknowledgments................................................................................................................ ........ iii

List of Figures ............................................................................................................................. vi i

List of Tables

............................................................................................................................... viii

1. Introduction ..........................................................................................................................1

1.1 Report Contents .........................................................................................................1

1.2 Exceptional Event Rule Requirements .......................................................................1

1.2.1 Public Notification that the Event Was Occurring (40 CFR

50.14(c)(1)(i)) .................................................................................................2

1.2.2 Place Informal Flag on Data in AQS (40 CFR 50.14(c)(2)(ii)) ........................2

1.2.3 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)) ................................................................................................2

1.2.4 Document that the Public Comment Process Was Followed for Event

Documentation (40 CFR 50.14(c)(3)(iv)) ........................................................2

1.2.5 Submit Demonstration Supporting Exceptional Event Flag (40 CFR

50.14(a)(1-2)) .................................................................................................3

1.2.6 Documentation Requirements (40 CFR 50.14(c)(3)(iii)) ................................3

2. Conceptual Model ................................................................................................................1

2.1 Geographic Setting and Monitor Locations ................................................................1

2.2 Climate .......................................................................................................................5

2.3 Event Day Summary ..................................................................................................6

3. Causal Relationship .............................................................................................................1

3.1 Discussion ..................................................................................................................1

3.2 Summary ....................................................................................................................5

4. Historical Norm ....................................................................................................................1

4.1 Analysis ......................................................................................................................1

4.2 Summary ....................................................................................................................2

5. Not Reasonably Controllable or Preventable ......................................................................1

5.1 Background ................................................................................................................1

5.1.1 Control Measures ...........................................................................................1

5.1.2 Additional Measures .......................................................................................3

5.1.3 PM Rule Effectiveness ................................................................................4 10



# 5.1.4 Compliance and Enforcement Activities.........................................................5

5.1.5 Review of Source-Permitted Inspections and Public Complaints ..................6

5.2 Forecasts and Warnings ............................................................................................7

5.3 Wind Observations.....................................................................................................7

5.4 Summary ....................................................................................................................7

6. But-For Analysis ..................................................................................................................1

6.1 Discussion ..................................................................................................................1

6.2 Summary ....................................................................................................................1

v

# Exceptional Event, Phoenix, Septem ber 6, 2012 Table of Contents



# vi 

# Section Page

7. Conclusions .........................................................................................................................1

7.1 Affects Air Quality .......................................................................................................1

7.2 Not Reasonably Controllable or Preventable .............................................................1

7.3 Natural Event .............................................................................................................1

7.4 Clear Causal Relationship..........................................................................................2

7.5 Historical Norm ...........................................................................................................2

7.6 But For .......................................................................................................................2

Appendix A: Air Quality and Meteorological Data for Maricopa County .................................. A-1

Appendix B: Media Coverage, Videos, and Images ............................................................... B-1

Appendix C: ADEQ and NWS Forecast Products.................................................................... C-1

Appendix D: Affidavit of Public Notice...................................................................................... D- 1

# Exceptional Event, Phoenix, Septem ber 6, 2012 List of Figures



# List of Figures

Figure Page

2-1. Locations of the air quality monitor that recorded an exceedance of the 24-hr PM

NAAQS on September 6, 2012, and NWS monitors described in this report....................2 10



# 2-2. Location of sites monitoring PM in Arizona on September 6, 2012................................3 10



# 2-3. Drainage system of Phoenix, Arizona. ..............................................................................4

2-4. Average monthly temperatures and precipitation for Phoenix, 1981–2010.......................5

2-5. Cross-section of a thunderstorm creating an outflow boundary and haboob....................6

3-1. Infrared satellite image from 1615 LST on September 6, 2012 (GOES-West). ................1

3-2. Hourly PM concentrations at Pinal County monitors on September 6, 2012.. ...............2 10



# 3-3. Hourly PM concentrations at Maricopa County monitors and visibility at KCHD on

September 6, 2012............................................................................................................3 10



# 3-4. Hourly PM concentrations and wind speeds at the West Chandler monitor on

September 6 and 7, 2012..................................................................................................3 10



# 3-5. Image from an ADEQ visibility camera on North Mountain looking south toward

downtown Phoenix and the South Mountains. ..................................................................4

3-6. Maximum 5-minute PM concentrations (colored circles), 5-minute wind speed

and directio n (vectors), maximum wind gus ts (red numbers), and minimum visibility

observations (white numbers) at Maricopa and Pinal county monitors between

1530 and 1600 LST on September 6, 2012. .....................................................................7 10



# 3-7. Similar to Figure 3-6, but representing observations from 1630 to 1700 LST...................8

3-8. Similar to Figure 3-6, but representing observations from 1730 to 1800 LST...................9

3-9. Similar to Figure 3-6, but representing observations from 1830 to 1900 LST.................10

4-1. 24-hr average PM concentrations at the West Chandler monitor (2007–2012).............1 10



# 4-2. Daily maximum hourly average PM concentrations at the West Chandler monitor

(2007–2012). .....................................................................................................................2 10



# 5-1. Timeline of Maricopa County fugitive dust rules and ordinances......................................5

vii

# Exceptional Event, Phoenix, Septem ber 6, 2012 List of Tables



# List of Tables

Table Page

2-1. Arizona PM measurements on September 6, 2012. ......................................................7 10



# 5-1. Rules and ordinances regulating PM emissions in Maricopa County. ..............................2

5-2. Pinal County rules regulating existing and new non-point sources in Pinal County..........3

5-3. Pinal County rules regulating fugitive dust in Pinal County portion of the Phoenix

PM Nonattainment Area.................................................................................................3 10



# viii

# Exceptional Event, Phoenix, September 6, 2012 Int roduction



# 1 

# 1. Introduction

On September 6, 2012, an air quality monitor in the Phoenix PM 10 

# nonattainment area

recorded a 24-hr average PM 10 

# concentration in excess of the National Ambient Air Quality

Standard (NAAQS) for PM 10 

# of 150 μg/m 3 

# . The purpose of this report is to demonstrate that this

exceedance was due to naturally occurring windblown dust, was not reasonably controllable or

preventable, was historically unusual, and would not have occurred “but-for” the windblown dust

and that it therefore constitutes an Exceptional Event as defined by the U.S. Environmental

Protection Agency’s (EPA) Exceptional Events Rule (EER).



# 1.1 Report Contents

Section 2 of this assessment contains a conceptual model of the windblown dust event

that transpired on September 6, 2012, providing a background narrative of the exceptional event

and an overall explanation showing that the event a ffected air quality. Section 2 also provides

evidence that the event was a natural event.

Section 3 of this assessment establishes a clear causal connection between the natural

event on September 6, 2012, and the exceedance of the 24-hr PM 10 

# standard at the monitoring

station. The evidence in this section also confirms that the event in question both affected air

quality and was the result of natural events.

Section 4 of this assessment illustrates that the event of September 6, 2012, produced

PM 10 

# concentrations in excess of normal historical fluctuations.

Section 5 of this assessment details the existing dust control measures and

demonstrates that, despite the presence and enforcement of these controls, the event of

September 6, 2012, was not reasonably controllable or preventable.

Section 6 of this assessment builds upon t he demonstrations made in the previous

sections, showing a clear causal connection between the natural event and the exceedance,

and concludes that the exceedance of the 24-hr PM 10 

# standard on September 6, 2012, would

not have occurred “but for” the event.

Appendix A contains time-series graphs and data tables to supplement Section 3.

Appendix B contains links to videos, images, and media reports to supplement Section 3.

Appendix C contains air quality forecasts issued by the Arizona Department of Environmental

Quality (ADEQ) and weather statements and warnings issued by the National Weather Service.

Appendix D contains a copy of the affidavit of public notice concerning this assessment report.



# 1.2 E xceptional Event Rule Requirements

In addition to the technical requirements that are contained within the EER, procedural

requirements must also be met in order for the EPA to concur with the flagged air quality

monitoring data. This section of the report lists the requirements of the EER and associated

guidance and discusses how ADEQ addressed those requirements.

# Exceptional Event, Phoenix, September 6, 2012 Introduction



# 2 

# 1.2.1 Public Notification that the E vent Was Occurring (40 CFR 50.14(c)(1)(i))

ADEQ issued Dust Control Action Forecasts and Air Quality Forecasts for Maricopa

County advising citizens of the potential for high wind dust events on September 6, 2012. More

information on ADEQ’s forecasts can be found in Section 5.2 of this report. The forecast

products that were issued for September 6, 2012, are included in Appendix C.



# 1.2.2 Place Informal Flag on Data in AQS (40 CFR 50.14(c)(2)(ii))

ADEQ and other operating air quality agencies in Arizona submit data into the EPA’s Air

Quality System (AQS), the official repository of ambient air quality data. This data submittal to

AQS includes particulate matter (PM) data fr om both filter-based and continuous monitors

operated in Arizona.

When ADEQ and/or another agency operating monitors in Arizona suspect that data

may be influenced by an exceptional event, AD EQ and/or the other operating agency expedites

analysis of the filters collected from the potentially-affected filter-based air monitoring

instruments, quality-assures the results, and submits the data into AQS. ADEQ and/or other

operating agencies also submit data from conti nuous monitors into AQS after quality assurance

is complete.

If ADEQ and/or other operating air quality agencies have determined that a potential

exists that a monitor’s reading(s) have been infl uenced by an exceptional event, a preliminary

flag is submitted for the measurement in AQS. The data are not official until they undergo more

thorough quality assurance and quality control, leading to certification by May 1 of the year

following the calendar year in which the data were collected (40 CFR 58.15(a)(2)). The

presence of the flag on the September 6, 2012, data can be confirmed in AQS.



# 1.2.3 Notify EPA of Intent to Flag Through Submission of Initial Event

Description b y July 1 of Calenda r 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

2012 that ADEQ intends to analyze under the Exceptional Events Rule. The PM 10 

# exceedance

that occurred on September 6, 2012, in the Phoenix PM 10 

# nonattainment area was included on

this list. This assessment report serves as demonstration supporting the flagging of the data.



# 1.2.4 Document that the Public Comme nt Process Was Follow ed for Event

Documentation (40 CFR 50.14(c)(3)(iv))

ADEQ posted this assessment report on the ADEQ webpage and placed a hard copy of

the report in the ADEQ Records Management Center for public review. ADEQ opened a 30-day

public comment period on January 14, 2013. 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.

# Exceptional Event, Phoenix, September 6, 2012 Introduction



# 3 

# 1.2.5 Submit Demonstration Supporting Exceptional Event Flag (40 CFR

50.14(a)(1-2))

At the close of the public comment period, and after ADEQ has had the opportunity to

consider any comments submitted on this document, ADEQ will submit this document, the

comments received, and ADEQ’s responses to those comments to EPA Region 9 headquarters

in San Francisco, California. The deadline for the submittal of this package is September 30,

2015.



# 1. 2.6 Documentation Requirements (40 CFR 50.14(c)(3)(iii))

The EER states that in order to justify the exclusion of air quality monitoring data,

evidence must be provided for the following elements:

1. The event satisfies the criteria set forth in 40 CFR 50.1(j) that

a. the event affected air quality,

b. the event was not reasonably controllable or preventable, and

c. the event was caused by human activity unlikely to recur in a particular

location or was a natural event;

2. There is a clear causal relationship between the measurement(s) under

consideration and the event;

3. The event is associated with a measured concentration(s) in excess of normal

historical fluctuations; and

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

# Exceptional Event, Phoenix, Sept ember 6, 2012 C onceptual Model



# 1 

# 2. Conceptual Model

This section provides a narrative background and summarizes the meteorological and

air quality conditions in place on September 6, 2012 in the Phoenix area. Elements described in

this section include

 A description and map of the geographic setting of the air quality and meteorological

monitors.

 A d escription of Phoenix’s climate.

 An overall description of meteorological and air quality conditions on the event day.



# 2.1 Geographic Setting and Monitor Locations

Phoenix is located in the Salt River Valley in south-central Arizona. It lies at an 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

Phoenix area is surrounded by the McDowell Mountains (~4,200 ft above msl) to the northeast,

the foothills of the Bradshaw (~7,900 ft above msl) and Mazataal (~7,900 ft above msl) ranges

to the north, the White Tank Mountains (~4,500 ft above msl) to the west, the Sierra Estrella

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

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

Mountain (~2,600 ft above msl). Current development is pushing north, west, and south into

Pinal County.

A fairly dense network of air quality and meteorological monitors exists throughout the

Phoenix area, with a much less dense network of monitors throughout the rest of Arizona.

Figure 2-1 shows the general geographic setting of Phoenix, as well as the location of the PM 10 

# monitor that recorded an exceedance on September 6, 2012. The monitors shown in the map

include AQS monitors, which measure air quality and meteorological data, and National

Weather Service (NWS) monitors, which measure meteorological data only. Some of the AQS

monitors in the Phoenix area are run by the Maricopa County Air Quality Department (MCAQD),

while others are run by ADEQ. The PM 10 

# exceedance on September 6, 2012, was recorded at

the West Chandler monitor. Phoenix Sky Harbor International Airport (KPHX) and Chandler

Municipal Airport (KCHD) were the primary NWS sites used in this demonstration package

because of those sites’ high data quality, data completeness, proximity to the West Chandler

monitor, and representativeness of meteorological conditions in the Phoenix area. Figure 2-2

shows the locations of PM 10 

# monitors statewide on September 6, 2012.

Figure 2-3 depicts the drainage systems or watersheds for the State of Arizona. Many

of the rivers that form Arizona’s drainage system are dry for most of the 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 low-lying

areas of central and southern Arizona, with larger depositional areas focused in and around the

confluences of dry river channels.

# 2Figure 2-1.Locations of the air quality monitor that recorded an exceedance of the 24-hr PM10NAAQS on September 6, 2012,and NWS monitors described in this report.

# Exceptional Event, Phoenix, Sept ember 6, 2012 Conceptual Model



# 3 Figure 2-2. Location of sites monitoring PM 10 

# in Arizona on September 6, 2012.

# Exceptional Event, Phoenix, Sept ember 6, 2012 Conceptual Model



# 4 Figure 2-3. Drainage system of Phoenix, Arizona.

# Exceptional Event, Phoenix, Sept ember 6, 2012 Conceptual Model



# 5 

# 2. 2 Climate

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

average summer high temperatures are among the hottest of any populated area in the United

States ( Figure 2-4 ). Temperatures reach or exceed 100°F an average of 110 days annually,

and reach or exceed 110°F an average of 18 days annually. Phoenix receives an average of

7.66 inches of rain per year. The bulk of this rain usually falls during the December through

March and July through August time periods. During the December through March period,

winter storms originating from the Pacific Ocean can produce significant rains in southwestern

Arizona. During the mid- to late-summer time period, monsoonal moisture originating from the

Gulf of California, Gulf of Mexico, and large thunderstorm complexes over the Sierra Madre

Occidental Mountains in Mexico move northward into Arizona.

0.0 0.2 0.4 0.6 0.8 1.0 1.2

0 20 40 60 80 100 120Precipitation(inches)Temperature(°F)



# Precipitation

Max Temp

Min Temp

Mean Temp



# Figure 2-4. Average monthly temperatures and precipitation for Phoenix, 1981–2010.



# The influx of moisture associated with the monsoon, combined with strong solar heating,

can result in unstable atmospheric conditions that are favorable for the development of

thunderstorms. Heavy precipitation associated with thunderstorms, and the eventual collapse

or dissipation of thunderstorms, can generate what are known as downbursts. Downbursts are

the rapid descent of rain-cooled air in a thunderstorm. Upon reaching the surface, this air

rapidly disperses horizontally away from the storm as the outflow boundary (also called gust

fronts), as shown in Figure 2-5 . The high winds associated with outflow boundaries can

efficiently loft dust into the air and transport the dust over long distances, resulting in dust

storms (also called haboobs) with high PM 10 

# concentrations and low visibilities.

# Exceptional Event, Phoenix, Sept ember 6, 2012 Conceptual Model



# 6 Cross

‐ section schematic of a haboob caused by the cool outflow from a

thunderstorm, with the leading edge that is propagating ahead of the storm

called an outflow boundary. The strong, gusty winds that prevail at the

boundary are defined as a gust front. The leading edge of the cool air is calle d

the nose, and the upward

‐ protruding part of the features is referred to as the

head. Behind the roll in the windfield at the leading edge is a turbulent wake.

The rapidly moving cool air and the gustiness at the gust front raise dust

(shaded) high into the atmosphere.



# Figure 2-5. Cross-section of a thunderstorm cr eating an outflow boundary and haboob.

(Source: Desert Meteorology , Thomas T. Warner, 2004.)



# Dust storms associated with these thunderstorms typically occur in the early part of the

monsoon season (July) before subsequent rains moisten the soil and limit potential lofting of soil

into the air. However, depending on the amount and frequency of precipitation received during

the monsoon season, the extremely hot temperatures can dry the surface soils very quickly;

thus, dust storms can occur at any time during the year. Specific PM 10 

# source regions are

difficult to determine during thunderstorm-driven dust storms because the thunderstorm outflow

can carry dust over long distances that encompa ss many possible sources of dust. Instead, we

consider general PM 10 

# source regions, which are typically identified based on the locations of

the thunderstorms that are believed to have generated the dust-laden outflow winds.



# 2.3 Event Day Summary

On the afternoon and evening of September 6, 2012, strong winds generated by

thunderstorms over south-central Arizona transported dust northward into the Phoenix area.

The windblown dust resulted in 24-hr average PM 10 

# concentrations in exceedance of the

NAAQS at one air quality monitor ( Table 2-1 ). The PM 10 

# concentration measured at this

monitor was in excess of normal historical fluctuations. The dust was naturally occurring and

likely originated over undeveloped lands south of the Phoenix area, and wind gusts in excess of

30 mph overwhelmed reasonable dust control meas ures. Monitors across Maricopa and Pinal

counties recorded high PM 10 

# concentrations during this dust storm, illustrating the widespread,

regional nature of the event.

# Exceptional Event, Phoenix, Sept ember 6, 2012 Conceptual Model



# 7 Table 2-1. Arizona PM 10 

# measurements on September 6, 2012. The exceedance

monitors discussed in this report are shown in bold.

Monitor Monitor

Type Operator AQS Monitor ID 24-hr

Avg

PM 10 

# (μg/m 3 

# ) 1-hr

Max

PM 10 

# (μg/m 3 

# ) Time of

Max 1-hr

PM 10 

# (LST) AQS

Qualifier

Flag

Apache County

N/A TEOM WMAT 04-001-1003-81102-1 12 25 700

Coconino County

N/A N/A ADEQ 04-005-1237-81102-1 N/A N/A N/A

Gila County

Hayden Old Jail TEOM ADEQ 04-007-1001-81102-3 41 139 1100

Maricopa County

Senior Center Air

Monitoring Station N/A SRP-MIC 04-013-7020-81102-1 125 N/A N/A

Senior Center Air

Monitoring Station N/A SRP-MIC 04-013-7020-81102-2 121 N/A N/A

Lehi Air Monitoring

Station N/A SRP-MIC 04-013-7022-81102-1 150 N/A N/A

West Phoenix BAM MC 04-013-0019-81102-1 30 117 1800

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

Glendale TEOM MC 04-013-2001-81102-1 39 185 1700

Central Phoenix TEOM MC 04-013-3002-81102-4 64 624 1700

Greenwood TEOM MC 04-013-3010-81102-1 46 247 1700

South Phoenix TEOM MC 04-013-4003-81102-1 79 870 1700

West Chandler TEOM MC 04-013-4004-81102-1 164 3056 1700 RJ

Tempe TEOM MC 04-013-4005-81102-1 103 1535 1700

Higley TEOM MC 04-013-4006-81102-1 128 2189 1700

West 43 rd 

# Ave TEOM MC 04-013-4009-81102-1 65 508 1700

Dysart TEOM MC 04-013-4010-81102-1 50 282 1700

Buckeye TEOM MC 04-013-4011-81102-1 46 325 1700

Zuni Hills TEOM MC 04-013-4016-81102-1 60 631 1800

South Scottsdale TEOM MC 04-013-3003-81102-1 101 1094 1700

Fort

McDowell/Yuma

Frank TEOM FMIR 04-013-5100-81102-3 N/A N/A N/A

Durango Complex TEOM MC 04-013-9812-81102-1 81 862 1700

JLG Supersite BAM ADEQ 04-013-9997-81102-3 37 113 600

JLG Supersite TEOM ADEQ 04-013-9997-81102-4 N/A N/A N/A

Navajo County

N/A TEOM WMAT 04-017-1002-81102-1 16 35 1600

Pima County

Ajo TEOM ADEQ 04-019-0001-81102-3 N/A N/A N/A

Rillito TEOM ADEQ 04-019-0020-81102-3 42 300 1400

Orange Grove FRM PCDEQ 04-019-0011-81102-2 27 N/A N/A

# Exceptional Event, Phoenix, Sept ember 6, 2012 Conceptual Model



# 8 Monitor Monitor

Type Operator AQS Monitor ID 24-hr

Avg

PM 10 

# (μg/m 3 

# ) 1-hr

Max

PM 10 

# (μg/m 3 

# ) Time of

Max 1-hr

PM 10 

# (LST) AQS

Qualifier

Flag

Prince Road FRM PCDEQ 04-019-1009-81102-1 18 N/A N/A

Tangerine FRM PCDEQ 04-019-1018-81102-1 22 N/A N/A

Santa Clara FRM PCDEQ 04-019-1026-81102-1 17 N/A N/A

Pinal County

Casa Grande

Downtown TEOM PCAQCD 04-021-0001-81102-3 92 978 1500

Apache Junction

Fire Station FRM PCAQCD 04-021-3002-81102-3 83 746 1700

Stanfield TEOM PCAQCD 04-021-3008-81102-3 121 1649 1600

Combs School TEOM PCAQCD 04-021-3009-81102-3 70 497 1700

Maricopa TEOM PCAQCD 04-021-3010-81102-3 N/A N/A N/A

Pinal County

Housing TEOM PCAQCD 04-021-3011-81102-3 164 2964 1600 RJ

Cowtown TEOM PCAQCD 04-021-3013-81102-3 159 2659 1600 RJ

Bapchule FRM GRIC 04-021-7004-81102-1 613 N/A N/A RJ

Bapchule FRM GRIC 04-021-7004-81102-2 547 N/A N/A RJ

Santa Cruz County

Nogales Post Office BAM ADEQ 04-023-0004-81102-3 17 38 1200

Yuma County

Yuma Supersite TEOM ADEQ 04-027-8011-81102-3 25 159 2000

TEOM: Tapered Element Oscillating Microbalance monitor

FRM: Federal Reference Method

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

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

PCDEQ: Pima County Department of Environmental Quality

PCAQCD: Pinal County Air Quality Control District

GRIC: Gila River Indian Community

RJ: qualifier flag for high winds

1 

# PM 10 

# data for 1600 and 1700 on Septembe r 6, 2012, were not available.

# Exceptional Event, Phoenix, September 6, 2012 Ca usal Relationship



# 3. Causal Relationship

3.1 Discussion

Meteorological and air quality observations indicate that dust carried by thunderstorm

outflow was directly responsible for the high PM 10 

# concentrations observed in the Phoenix area

on September 6, 2012. On the afternoon of September 6, a large area of thunderstorms

developed over south-central Arizona, south of the Phoenix area ( Figure 3-1 ). As these

thunderstorms drifted north, they generated a dust-carrying outflow boundary that propagated

northward into the Phoenix area. As stated in Section 2.2, thunderstorms associated with the

summer monsoon season can generate strong winds and blowing dust across Arizona. The

likely source region for PM 10 

# during the September 6, 2012, event was the deserts south of

Phoenix and largely outside the Phoenix PM 10 

# nonattainment area. This region mainly consists

of natural, undisturbed desert. In addition, the two weeks leading up to the event were dry in

the Phoenix area, with the last measureable rainfall at KPHX occurring on August 23. This

combination of geography and lack of rainfall preceding the event resulted in a large fetch of

soils that were particularly vulnerable to particulate suspension.

Figure 3-1. Infrared satellite image from 1615 LST on September 6, 2012 (GOES-West).

Colder temperatures (blues, purples, and whit e) indicate tall, convective (thunderstorm)

clouds. Thunderstorms over south-centra l Arizona generated outflow boundaries that

carried dust northward into Arizona.

1

# Exceptional Event, Phoenix, September 6, 2012 Causal Relationship



# The effects of the thunderstorm outflow and associated windblown dust were evident at

most Pinal County monitors between 1600 and 1700 LST on September 6, with PM 10 

# concentrations exceeding 2,500 μg/m 3 

# at two monitors ( Figure 3-2 ). The thunderstorm outflow

and associated dust continued northward and arrived in the Phoenix area between 1700 and

1800 LST on September 6, with visibility reduced to near zero at KCHD ( Figure 3-3 ). PM 10 

# concentrations at the West Chandler monitor increased sharply over this time period, with 1-hr

PM 10 

# concentrations exceeding 3,000 μg/m 3 

# ( Figure 3-4 ). Collocated wind observations at

West Chandler showed wind gusts in excess of 30 mph coincident with the high PM 10 

# concentrations. Several other monitors in the Phoenix area reported gusty winds at the same

time as the high PM 10 

# concentrations, including a wind gust of 40 mph at KCHD (Appendix A).

Visibility cameras in the Phoenix area also clearly showed a reduction in visibility and blowing

dust as the outflow arrived ( Figure 3-5 ). Links to these videos and other media coverage and

images pertaining to this windblown dust event are shown in Appendix B. It is also important to

note that before the abrupt increase in PM 10 

# in the Phoenix area, winds were lighter, visibilities

were greater, and PM 10 

# concentrations were much lower, illustrating the correlation between the

high winds and the dust. In response to the approaching thunderstorm outflow and associated

dust and low visibilities, the NWS office in Phoenix issued a Blowing Dust Advisory and Dust

Storm Warning for portions of western Pinal and Maricopa Counties (Appendix C). The Blowing

Dust Advisory and Dust Storm Warning specifically mentioned the Chandler area, which is

where the West Chandler monitor is located.

Figure 3-2. Hourly PM 10 

# concentrations at Pinal County monitors on September 6, 2012.

PM 10 

# concentrations sharply increased between 1500 and 1700 LST, indicating the

arrival of windblown dust.

2

# Exceptional Event, Phoenix, September 6, 2012 Causal Relationship



# Figure 3-3. Hourly PM 10 

# concentrations at Maricopa County monitors and visibility at

KCHD on September 6, 2012. Visibility wa s greatly reduced at 1700 and 1800 LST on

September 6, 2012, coinciding with the sharp increase in PM 10 

# concentrations at

Maricopa County monitors, indicating the arrival of windblown dust.

Figure 3-4. Hourly PM 10 

# concentrations and wind speeds at the West Chandler monitor

on September 6 and 7, 2012. PM 10 

# concentrations and wind speeds sharply increased

at 1700 LST on September 6, 2012, indica ting the arrival of windblown dust

.

3

# Exceptional Event, Phoenix, September 6, 2012 Causal Relationship



# Figure 3-5. Image from an ADEQ visibility camera on North Mountain looking south

toward downtown Phoenix and the South Mount ains. Windblown dust associated with

thunderstorm outflow reduced visibility thro ughout the Phoenix area, obscuring the

downtown skyline and South Mountains.



# The progression of the thunderstorm outflow and windblown dust through the Phoenix

area is summarized by the radar velocity and wind vector spatial plots below ( Figures 3-6

through 3-9 ).



# 1530-1600 LST (Figure 3-6)

Observations at area monitors generally showed light winds with a westerly component,

high visibilities, and low PM 10 

# concentrations across Maricopa County. At this time,

thunderstorm outflow was just beginning to impact monitors in western Pinal County, but the

outflow boundary itself was not yet detected on Doppler radar.



# 1630-1700 LST (Figure 3-7)

Between 1630 and 1700 LST, the outflow boundary was detectable on Doppler radar

over northwestern Pinal County and far southern Maricopa County and was just south of the

West Chandler monitor. Note that the outflow boundary exhibited a bowed structure, with a

4

# Exceptional Event, Phoenix, September 6, 2012 Causal Relationship



# 5 

# bulge northward aimed at the West Chandler monitor. In quasi-linear thunderstorm boundaries,

bowing structures, and especially the apex of a bowing structure, are often locations of stronger

wind speeds. Thus, the structure and motion of the outflow boundary on September 6, 2012,

was particularly favorable for the development of strong winds specifically in the vicinity of the

West Chandler monitor. Monitors in western Pi nal County were already impacted by the outflow

boundary and windblown dust, reporting PM 10 

# concentrations above 2,500 μg/m 3 

# , gusty

southwesterly winds, and decreased visibilities. Monitors across Maricopa County had not yet

been affected by the outflow, and thus continued to report low PM 10 

# concentrations, generally

light winds, and high visibilities.



# 1730-1800 LST (Figure 3-8)

The outflow boundary continued moving northward into Maricopa County, affecting

several monitors in the Phoenix metropolitan area, but most strongly impacting the east and

southeast side of the Phoenix area. Conditions near and south of the outflow boundary were

characterized by gusty south-southwesterly winds , visibilities as low as 0.25 miles, and high

PM 10 

# concentrations. Although only the West Chandler monitor in Maricopa County recorded

an exceedance of the NAAQS, several other monitors reported 5-minute PM 10 

# concentrations in

excess of 2,500 μg/m 3 

# . PM 10 

# concentrations and wind speeds decreased at Pinal County

monitors as the outflow boundary moved northward out of Pinal County.

The West Chandler monitor likely recorded the highest PM 10 

# concentrations because of

its location on the southeastern side of the Phoenix urban area, closer to the undeveloped lands

of western Pinal County where much of the dust and PM 10 

# likely originated. And, as mentioned

above, the bowed structure of the outflow boundary favored locally stronger winds in the vicinity

of the West Chandler monitor. Also of note were very high 24-hour average PM 10 

# concentrations at the filter-based monitor operated by the Gila River Indian Community (see

Table 2-1), which is in northern Pinal County very near the West Chandler monitor. Thus, the

West Chandler monitor was likely subject to greater quantities of transported PM 10 

# compared to

other monitors in the nonattainment area.



# 1830-1900 LST (Figure 3-9)

As the outflow boundary continued northward, PM 10 

# concentrations decreased at most

Maricopa and Pinal county monitors, including at West Chandler. Winds remained gusty across

Maricopa County but shifted to westerly, which was no longer conducive to transport of dust and

PM 10 

# from the south. Finally, visibilities quickly returned to at or above 10 miles as the outflow

boundary departed to the north of the Phoenix area.



# 3.2 Summary

The information presented in this section demonstrates a clear causal relationship

between the windblown dust and the PM 10 

# exceedance measured in the Phoenix PM 10 

# nonattainment area on September 6, 2012. The wind, visibility, PM 10 

# , and radar data shown in

this section illustrate the spatial and temporal extent of the dust storm as it moved through

Maricopa County.

# Exceptional Event, Phoenix, September 6, 2012 Causal Relationship



# 6 

# In addition, meteorological data tables found in Appendix A show that the sharp increase

in PM 10 

# concentrations coincided with the gusty winds, low visibilities, and airport observer

reports of blowing dust. The fact that PM 10 

# concentrations in Pinal County spiked prior to PM 10 

# concentrations increasing in Maricopa County illustrate that a vast majority of the dust that

impacted the nonattainment area monitors originated outside of Maricopa County and was

transported into the Phoenix PM 10 

# nonattainment area. While PM 10 

# concentrations were high

regionally during the event, the West Chandler monitor was the closest Maricopa County

monitor to the open and desert areas of western Pinal County, resulting in an exceedance at the

West Chandler monitor. The proximity of t he West Chandler monitor to open and desert areas

of Pinal County provides solid evidence as to why this was the only monitor within the Maricopa

County nonattainment area that recorded an exceedance.RadarSite



# 7Figure 3-6.Maximum 5-minute PM10concentrations (colored circles), 5-minutewind speed and direction (vectors), maximumwind gusts (red numbers), and minimum visibility observations (white numbers) at Maricopa and Pinal county monitors between1530 and 1600 LST on September 6, 2012. Where 5-minute data are unavailable (e.g., PM10data in Pinal County), 1-hour dataare used. Underlying colors are Doppler radar velocity data at 1534 LST, where greens indicate motion toward the radar andoranges/reds indicate motion away from the radar.RadarSite



# 8Figure 3-7.Similar to Figure 3-6, but representing observations from 1630 to 1700 LST. Doppler radar data are from 1644 LST.OutflowboundaryRadarSite



# 9Figure 3-8.Similar to Figure 3-6, but representing observations from 1730 to 1800 LST. Doppler radar data are from 1730 LST.

# 10RadarSiteFigure 3-9.Similar to Figure 3-6, but representing observationsfrom 1830 to 1900 LST. Doppler radar data are from 1838 LST.

# Exceptional Event, Phoenix, September 6, 2012 Historical Norm



# 4. Historical Norm

4. 1 Analysis

PM 10 

# concentrations measured at Phoenix-area monitors on September 6, 2012, were

unusual and in excess of normal historical fluctuations. To establish the severity of this event,

PM 10 

# concentrations measured on September 6, 2012, were compared to a historical 2007 to

2012 annual data set at the West Chandler monitor. The PM 10 

# concentrations measured at the

West Chandler monitor on September 6, 2012, resulted in some of the highest 24-hr averages

( Figure 4-1 ) and daily maximum hourly averages ( Figure 4-2 ) measured over the 5-year period.

0 50 100 150 200 250 300 350 400 450 500PM10Concentration (μg/m3)



# Date West Chandler 5-Year Historical Fluctuation - 24 Hour Averages

September 6, 2012



# Figure 4-1. 24-hr average PM 10 

# concentrations at the West Chandler monitor (2007–

2012). The 24-hr average PM 10 

# concentration on September 6, 2012, is shown in red

and highlighted by the arrow.

1

# Exceptional Event, Phoenix, September 6, 2012 Historical Norm



# 2 0 500 1000 1500 2000 2500 3000 3500 4000 4500 5000PM10 Concentration (μg/m3)



# Date 

# West Chandler 5-Year Historical Fluctuation - Daily Maximum Hourly Averages

September 6, 2012



# Figure 4-2. Daily maximum hourly average PM 10 

# concentrations at the West Chandler

monitor (2007–2012). The daily maximum hourly average PM 10 

# concentration on

September 6, 2012, is i ndicated by the arrow.



# 4.2 Summary

Given the recorded values and using a methodology similar to the one accepted by EPA,

it is clear that the PM 10 

# levels on September 6, 2012, were outside normal historical

fluctuations. This analysis provides evidence that the event affected air quality on a hi storic

scale.

# Exceptional Event, Phoenix, September 6, 2012 No t Reasonably Controllable or Preventable



# 1 

# 5. Not Reasonably Controllable or Preventable

5. 1 Background

ADEQ and MCAQD are responsible for implementing regulatory measures to control

emissions from agricultural sources, stationary sources, fugitive dust sources, and open burning

within Maricopa County. Three major programs provide or contribute to air pollution control

measures for the Greater Phoenix area. These programs include

1. AD EQ’s Agricultural Best Management Program (Ag BMP)

2. Ma ricopa County’s Inspection and Compliance Program

3. AD EQ’s Air Quality Forecasting Program

Specifically, ADEQ is responsible for co mpliance assistance and enforcement of

Agricultural Best Management Practices developed by the Governor’s Agricultural Best

Management Practices Committee, while MCAQD is responsible for compliance assurance for

all other significant sources of PM 10 

# emissions. In addition to routine inspections and

inspections driven by complaints, inspections are often increased when (1) ADEQ forecasters

issue a Maricopa County Dust Control Forecast of “High Risk,” (2) ADEQ forecasters issue a

High Pollution Advisory, or (3) near-real-time moni toring data indicate unique activity via high

PM concentrations. The forecasting program and inspection/compliance programs work

together so that resources can be best utilized during days of greatest risk for elevated PM

emissions.

On July 25, 2002, EPA took initial action to finalize approval of the Best Available

Control Measure (BACM) and the Most Stringent Measure (MSM) demonstrations in the Serious

Area PM 10 

# plan for the Maricopa County portion of the metropolitan Phoenix PM 10 

# nonattainment area (67 FR 48718). These BACM and MSM demonstrations were again

approved by EPA on July 14, 2006 (71 FR 43979). The Agricultural Best Management

Practices General Permit rule and related definitions have been adopted into the Arizona

Administrative Code as R18-2-610 and R18-2-611, pursuant to Arizona Revised Statutes

§49-457 1 

# Updates to the Ag BMP program in December 2011 clarified BMPs.



# 5.1.1 Control Measures

Maricopa County regulations of PM 10 

# emissions are listed in Table 5-1

.

1 

# Updates to the Ag BMP program in December 2011 clarified BMPs for crops and added BMPs for animal

operations. Effective 12/29/2011, R18- 2-611 was renumbered to R18-2-610.01 Agricultural PM 10 

# General Permit

for Crop Operations and R18-2-611.01 Animal Operations PM 10 

# General Permit was added. Definitions for Crop

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

# Exceptional Event, Phoenix, September 6, 2012 Not Reasonably Controllable or Preventable



# 2 Table 5-1. Rules and ordinances regulating PM emissions in Maricopa County.



# Rule/Ordinance Number & Title Description

Rule 300: Visible emissions Establishes standards for visible emissions and opacity.

Rule 310: Fugitive dust from dustgenerating 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 nontraditional 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 for particulate emissions from abrasive blasting

operations.

Rule 314: Open outdoor fires and

indoor fireplaces at commercial and

institutional establishments Establishes limits for t he 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 emission s 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 particulate matter from existing power plants

and cogeneration plants.

Rule 323: Fuel burning equipment

from industrial/commercial/

institutional (ICI) sources Establishes limits for the emissions of nitrogen oxides, sulfur oxides,

carbon monoxide and particulate 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 engines used in cogeneration.

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 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 wood

burning restriction Establishes restrictions for residential wood burning.

Ordinance P-27: Vehicle parking

and use on unstabilized vacant lots Establishes restrictions for vehicle parking and use on unstabilized

vacant lots in unincorporated sections of Area A in Maricopa County.

Ordinance P-28: Off-road vehicle

use in unincorporated areas of

Maricopa County Establishes restrictions for operatin g vehicles on unpaved property in

unincorporated areas of Maricopa County.

# Exceptional Event, Phoenix, September 6, 2012 Not Reasonably Controllable or Preventable



# 3 

# Rule/Ordinance Number & Title Description

Arizona Administrative Code R18-

2-611 & 610: Agricultural PM 10 

# general permit Establishes a requirement for commer cial farmers to implement best

management practices and maintain a record demonstrating

compliance.



# 5.1.2 Additional Measures

In addition to the rules and regulations listed in Table 5-1 , other PM 10 

# -reducing control

measures (e.g., paving unpaved roads, PM 10 

# -certified street sweepers, controlling unpaved

parking lots, etc.) have been committed to and implemented by local jurisdictions throughout the

PM 10 

# nonattainment area and incorporated into the Arizona state implementation plan (SIP)

through PM 10 

# plans such as the Revised Maricopa Association of Governments’ (MAG) 1999

Serious Area Particulate Plan for PM 10 

# 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 County (see Table 5-2 ).

Additionally, the PCAQCD implements specific n onattainment rules for that part of the Phoenix

PM 10 

# nonattainment area that resides in Pinal County (see Table 5-3 ).

Table 5-2. Pinal County rules regulating existing and new non-point sources in Pinal County.



# Article Number & Title Description

Article 2: Fugitive dust Provides a mechanism to reasonably regulate operations which

periodically may cause fugitive dust emissions into the atmosphere.

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 5-3. Pinal County rules regulating fugitive dust in Pinal County portion of the

Phoenix PM 10 

# Nonattainment Area.



# Article Number & Title Description

Article 4: Nonattainment area rules;

dustproofing for commercial parking,

drives, and yards Establishes rules to avoid violations of the prevailing PM 10 

# standard

and additionally minimize nuisance impacts by improving control of

excessive fugitive dust emissions from unpaved parking lots.

Article 5: Nonattainment area rules;

stabilization for residential parking

and drives Establishes rules for stabilizing residential properties.

Article 6: Restrictions on vehicle

parking and use on vacant lots Establishes rules for unpaved or unstable vacant lots.

Article 7: Construction sites in

nonattainment areas – fugitive dust Establishes rules to avoid violations of the prevailing PM 10 

# standard

and additionally minimize nuisance impacts by improving control of

excessive fugitive dust emissions from activities associated with

construction, earthwork, or land development.

# Exceptional Event, Phoenix, September 6, 2012 Not Reasonably Controllable or Preventable



# 4 

# Article Number & Title Description

Article 8: Nonattainment area rules,

requirement for stabilization of

disturbed areas at vacant lots Establishes rules for stabilizing di sturbed areas at vacant lots.



# 5.1 .3 PM 10 

# Rule Effectiveness

MCAQD analyzed the effectiveness of its fugitive dust rules (Rules 310, 310.01, and

316) in terms of permit compliance rates. This rule effectiveness (RE) study was designed to

assess how many sources regulated by MCAQD during the subject time period received no

PM 10 

# emissions-related violations. As a basis for comparison, the percentage of permitted

sources 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 strengthened, and new ordinances (covering additional source categories such as

leaf blowers, vacant lots, and off-road vehicles) were adopted. These enhancements resulted

from MCAQD’s obligations under such agreements as the 2005 Revised PM 10 

# State

Implementation Plan for the Salt River Area and the Maricopa Association of Governments 2007

Five Percent Plan for PM 10 

# for the Maricopa County Nonattainment Area to reduce PM 10 

# emissions throughout the county. Three major areas that contributed to increased compliance

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

regulatory changes that broadened 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, 95% compliance (from 85%) for Rule 310.01 sources, and 65% (from 40%)

for Rule 316 sources. These improvements continued into calendar year 2010 with compliance

rates of 94% for Rule 310 sources, 96% for Rule 310.01 sources, and 73% for Rule 316

sources. The timeline below ( Figure 5-1 ) illustrates the improvements in RE over the last

several years; it also points out significant revi sions to previous rules, as well as newly adopted

rules and ordinances.

# Exceptional Event, Phoenix, September 6, 2012 Not Reasonably Controllable or Preventable



# 5 M a r c h 2 0 0 8 S e p t e m b e r 2 0 0 6



# Figure 5-1. Timeline of Maricopa County fugitive dust rules and ordinances.



# 5.1 .4 Compliance and Enforcement Activities

MCAQD is prepared to proactively respond to high wind events and protect human

health and well-being. MCAQD’s approach consists of two primary components: proactive

inspections conducted routinely, as well as surveillance inspections conducted during and after

significant air quality events. MCAQD routi nely inspects dust control-permitted sites and

increases the frequency of inspections for permits covering areas of 10 acres or more. Rule

316 sources are also regularly inspected multiple times every year. Maricopa County responds

to the majority of complaints within 24 hours.

Maricopa County monitors the ADEQ Five-Day Dust Control Forecast to identify the

potential for elevated PM 10 

# pollution levels due to high winds or stagnant conditions. When a

High Pollution Advisory (HPA) is issued fo r Maricopa County, MCAQD conducts increased

surveillance before, during, and after the fore cast event(s). MCAQD also conducts event

surveillance and post-event activities during exceedance days that had not been forecast (i.e.,

those instances in which an HPA had not been issued).

Pre-event surveillance consists of surv eying high-risk areas for any dust-generating

activities, educating sources of the impending HPA event, and issuing violations for failure to

comply with local, state, or federal regulati ons. During the event, MCAQD inspectors survey

high-risk areas to confirm that control measures are in place, document any violations, and

contact other regulatory agencies if necessary. Post-event activities include continued surveys

of high-risk areas, re-inspecting sources that had incurred violations within two business days,

and an internal MCAQD debriefing of event activities.

During 2011 and 2012, a total of 17 MCAQD air monitoring sites were upgraded with

new equipment that allows the monitoring sites to automatically report measured readings at

5-minute intervals. Previously, only hourly r eadings were available. The real-time data

reporting system includes a mechanism to aler t MCAQD field staff when PM concentrations are

elevated. The system allows MCAQD responders to review concentrations at the monitors and

# Exceptional Event, Phoenix, September 6, 2012 Not Reasonably Controllable or Preventable



# 6 

# to consult the National Weather Service website to check for weather event activity. This

capability allows the MCAQD responder to identif y regional events and monitor specific issues.

If necessary, the MCAQD responders can inform nearby stakeholders and local governments of

the elevated PM 10 

# concentrations.



# 5.1 .5 Review of Source-Permi t ted Inspections and Public Complaints

ADEQ’s Arizona Unified Repository for Information Tracking of the Environment

(AZURITE) database was queried to compile a list of inspections for the permitted sources in

the Maricopa area around the time of the September 6, 2012, PM 10 

# exceedances. An

evaluation of all inspection reports, air quality complaints, compliance reports, and other

documentation did not indicate any evidence of unusual anthropogenic-based PM 10 

# emissions.

During the period of September 3 through 9, 2012, MCAQD inspectors conducted a total of 144

inspections of permitted facilities, of which 102 were at fugitive dust sources. Additionally,

MCAQD conducted 69 inspections on vacant lots and unpaved parking lots. During this 7-day

period, a total of 24 citations for violations were issued countywide for PM 10 

# and non-PM 10



# related violations. One violation was issued for PM 10 

# emissions within a 4-mile radius of an

exceeding monitor (West Chandler).

On September 4, 2012, a violation was issued to an earthmoving operation of 0.15 acres

for not obtaining a dust control permit. A dust control permit was issued to this site on

September 19, 2012. No unstable area was disc overed during the inspection on September 4,

2012, or the subsequent inspections performed on September 10, 2012, and October 15, 2012.

The site was located approximately 3.4 miles west of the West Chandler monitor. Since winds

during the thunderstorm outflow and high PM 10 

# event were from the south, it is highly unlikely

that this violation impacted PM 10 

# concentrations at the West Chandler monitor on September 6,

2012.

MCAQD was prepared for any complaints received due to the high wind event. During

the 7 day period from September 3, 2012 th rough September 9, 2012, MCAQD received 18

complaints, of which 11 were windblown dust-related. Each complaint was assigned to and

investigated by a MCAQD inspector. A review of all pertinent records from this period indicates

that MCAQD inspectors observed no PM 10 

# violations of local, state, or federal regulations within

a 4-mile radius of the exceeding monitor.

In addition to MCAQD’s efforts in pre-event surveillance and proactive inspections,

ADEQ’s Ag BMP inspector also monitors the ADEQ Five-Day Dust Control Forecast and the

MCAQD air monitoring sites that include real-tim e data. The ADEQ Ag BMP inspector uses

specific knowledge of seasonal activities and associations with the local growers and dairymen

to communicate the importance of limiting dust-generating activities, especially during high wind

events. Additional outreach is conducted with facility representatives prior to forecast high wind

alert days. Should the PM 10 

# readings at a MCAQD air monitoring site show a notable increase,

the ADEQ Ag BMP inspector is dispatched to contact the owners and operators of agricultural

fields in the area to discern whether their ac tivities are causing negative impacts. The Ag BMP

inspector is prepared to respond to most agriculture complaints within 24 hours.

# Exceptional Event, Phoenix, September 6, 2012 Not Reasonably Controllable or Preventable



# 7 

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

evidence to suggest that agricultural activities produced unusual PM 10 

# emissions. On

September 6, 2012, the ADEQ Ag BMP inspector received one complaint and conducted

outreach in response to a dust complaint at an agricultural composting location in the area of

Lindsey Road and Ocotillo Road.



# 5. 2 Forecasts and Warnings

Dust forecasts and statements were released prior to the event by both ADEQ and the

NWS office in Phoenix (Appendix C). On September 5, 2012, a Maricopa County Dust Control

Forecast for September 6, 2012, was issued by ADEQ, indicating a moderate risk level for

unhealthy PM 10 

# . The Dust Control Forecast also indicated a potential for gusty winds near

thunderstorm outflow.

The NWS office in Phoenix issued several Blowing Dust Advisories, Dust Storm

Warnings, and Severe Thunderstorm Warnings between 1600 and 1800 LST for portions of

Pinal and Maricopa counties, coincident with the period of gusty outflow winds and high PM 10 

# concentrations in the Phoenix area. These advisories warned residents of the potential for

gusty winds to 40 mph and visibilities reduced below 1⁄4 mile due to blowing dust generated by

thunderstorm outflow moving northward from Pinal County into Maricopa County.



# 5.3 Wind Observations

Wind data during the event (Figure 3-2 and Appendix A) showed widespread wind gusts

of over 30 mph coincident with the high PM 10 

# concentrations, including a wind gust of 40 mph at

KCHD (near the West Chandler PM 10 

# monitor).



# 5 .4 Summary

The thunderstorm outflow event of September 6, 2012, produced strong winds that

transported dust and PM 10 

# into the Phoenix PM 10 

# nonattainment area. The source region of the

outflows that caused the exceedances was largely located in areas outside the Phoenix PM 10 

# nonattainment area, primarily the deserts south of Maricopa County. The Phoenix area is

designated as a serious nonattainment area for PM 10 

# and is required to have BACM for all

significant sources of PM 10 

# . BACM on significant anthropogenic sources were in place and

enforced during the events, and pro-active tracking and response to the events by regulatory

agencies and local governments confirmed the uncontrollable nature of the dust emissions;

therefore, these pre-existing prior-approved required controls are adequate for meeting the

requirements of an exceptional event and should be considered “reasonable” for these

purposes.

Despite the deployment of comprehensive control measures and sophisticated response

programs, high wind conditions associated with the thunderstorm outflow transported high

concentrations of PM 10 

# into, and also overwhelmed controls within, the Phoenix PM 10 

# nonattainment area. Widespread wind gusts ov er 30 mph were strong enough to overwhelm

available efforts to limit PM 10 

# concentrations during the event. The fact that these were natural

# Exceptional Event, Phoenix, September 6, 2012 Not Reasonably Controllable or Preventable



# 8 

# events involving strong winds that transported PM 10 

# emissions into and across Maricopa

County, with a majority of the PM 10 

# emissions recorded by Maricopa County area monitors

coming from sources outside of the Phoenix PM 10 

# nonattainment area, provides strong

evidence that the exceedance of September 6, 2012, recorded within the Phoenix PM 10 

# nonattainment area was not reasonably controllable or preventable.

# Exceptional Event, Phoenix, September 6, 2012 But -For Analysis



# 1 

# 6. But-For Analysis

6. 1 Discussion

Section 50.14(c)(3)(iv)(D) in 40 CFR Part 50 requires that an exceptional event

demonstration satisfy the condition that “[t]here would have been no exceedance or violation but

for the event.” The prior sections of this subm ittal have provided detailed information that, in

regard to the PM 10 

# exceedance at the West Chandler monitor on September 6, 2012,

 the exceedance was not reasonably controllable or preventable, and

 t here was a clear causal relationship between PM 10 

# transported strong winds originating

in desert areas outside the Phoenix PM 10 

# nonattainment area and the measured PM 10



# exceedance at the West Chandler monitor.

The weight of evidence in these sections demonstrates that, but for the existence of dust

emissions generated by strong winds and the associated transport of PM 10 

# , there would have

been no exceedance of the NAAQS for 24-hr average PM 10



# .

As shown in Section 3, maps and time-series plots of PM 10 

# and wind speeds establish a

clear causal relationship between windblown dust due to thunderstorm outflow and elevated

PM 10 

# concentrations at Phoenix-area monitors. Multiple independent measurements of wind

speed, wind direction, and visibility point to the presence of gusty winds generated by

thunderstorm outflow as the mechanism for transport of PM 10 

# into the Phoenix nonattainment

area. In addition, PM 10 

# concentrations were well below the NAAQS on days immediately before

and after the windblown dust event. The source region for the PM 10 

# is clearly identified as

desert areas south of the Phoenix PM 10 

# nonattainment area. The weight of evidence presented

in this submittal provides no alternative that could tie the exceedance of September 6, 2012, to

any causal source except PM 10 

# transported by strong winds, confirming that there would have

been no exceedance but for the presence of this uncontrollable natural event.

As detailed in Section 5, all reasonable control measures were in place and/or

implemented on a continual basis. Air quality -related inspection and compliance data revealed

one violation with 4 miles of the exceedance monitor; however, the meteorological conditions on

September 6, 2012, indicate that the source of this violation does not explain and could not

have resulted in the very high PM 10 

# concentrations observed. Local regulatory agencies,

industry, and the general public were alerted to the possibility of dust storms due to strong

winds via daily forecasts and media reports.



# 6. 2 Summary

The weight of evidence presented in this submittal provides no alternative that could tie

the exceedance of September 6, 2012, to any causal source other than PM 10 

# transported by

gusty winds due to thunderstorm outflow, confirming that there would have been no exceedance

but for the presence of this uncontrollable natural event.

# Exceptional Event, Phoenix, September 6, 2012 C onclusions



# 1 

# 7. Conclusions

The PM 10 

# exceedance that occurred on September 6, 2012, satisfy the criteria of the

EER, which states that in order to justify the exclusion of air quality monitoring data, evidence

must be provided for the following elements:

 The event satisfies the criteria set forth in 40 CFR 50.1 (j) that

a . the event affected air quality,

b. the event was not reasonably controllable or preventable, and

c. the event was caused by human activity unlikely to recur in a particular location or

was a natural event;

 Th ere is a clear causal relationship between the measurement(s) under consideration

and the event;

 Th e event is associated with a measured concentration(s) in excess of normal historical

fluctuations; and

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



# 7 .1 Affects Air Quality

As stated in the preamble to the EER, the event in question is considered to have

affected air quality if it can be shown that there is a clear causal relationship between the

monitored exceedance and the event, and that the event is associated with a measured

concentration in excess of normal historical fluctuations. Given the information presented in

Sections 2, 3, 4, and 5, we can reasonably conclude that the event in question affected air

quality.



# 7 .2 Not Reasonably Controllable or Preventable

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

controllable or preventable” in order to be defined as an exceptional event. This requirement is

met by demonstrating that despite reasonable control measures in place within Maricopa

County, high winds overwhelmed all reasonabl y available controls (Section 5). The PM 10 

# exceedance discussed in this report was caused by naturally occurring gusty winds associated

with thunderstorm outflow that transported dust into the Phoenix area from areas largely outside

the Phoenix PM 10 

# nonattainment area. These facts provide strong evidence that the PM 10 

# exceedance on September 6, 2012, was not reasonably controllable or preventable.



# 7 .3 Natural Event

As discussed above, the PM 10 

# exceedance at the West Chandler monitor on September

6, 2012, was shown to be caused by transport of PM 10 

# into the Phoenix area from gusty winds

associated with thunderstorm outflow. The event therefore qualifies as a natural event.

# Exceptional Event, Phoenix, September 6, 2012 Conclusions



# 2 

# 7 .4 Clear Causal Relationship

The following points demonstrate that the high PM 10 

# concentrations were caused by

windblown dust:

 Time-series graphs of PM 10 

# concentrations show that the timing of high PM 10 

# at Phoenix

area monitors was consistent with gusty winds and low visibilities at Phoenix-area

meteorological stations (Section 3).

 H igh PM 10 

# concentrations and gusty winds were reported at several monitors throughout

the Phoenix metropolitan area (Sections 3 and 5).

 P M 10 

# concentrations were well below the NAAQS on days immediately before and after

the windblown dust event (Section 3).

 Dry conditi ons preceding the event resulted in soils that were particularly susceptible to

particulate suspension by high winds (Section 3).

 Wind direct ions, thunderstorm-generated outflow boundary propagation, and

concentration patterns showing elevated levels of PM 10 

# in Pinal County prior to levels

increasing in Maricopa County illustrate that a vast majority of the dust that impacted the

nonattainment area monitors originated outside of Maricopa County and was transported

to the nonattainment area. The particular wind magnitudes and wind direction, and the

proximity of the exceeding monitor to open and desert areas of Pinal County, provide

solid evidence as to why only one monitor within the Maricopa County nonattainment

area recorded an exceedance (Section 3).

 Visibility cameras clearly illustrate the arrival of dust and significant reductions in visibility

in the Phoenix area coinciding with the sharp increases in PM 10 

# concentrations.



# 7 .5 Historical Norm

The 24-hr average PM 10 

# values measured at Phoenix area monitors were historically

unusual compared to a multi-year data set (Section 4).



# 7 .6 But For

On the basis of the weight of evidence described above and in Section 6, the

exceedance of the federal 24-hr PM 10 

# standard on September 6, 2012, in the Phoenix PM 10 

# nonattainment area would not have occurred but for the high winds and transport of dust from

areas largely outside the Phoenix PM 10 

# nonattainment area.

# Exceptional Event, Phoenix, S eptember 6, 2012 Appendix A



# A ppendix A:

Air Quality and Meteorological Data for Maricopa County

This section contains tables of meteorological data from National Weather Service sites

in the Phoenix area for September 6, 2012. Reduced visibilities, gusty winds, and blowing dust

or dust storms were reported coincident with the arrival of thunderstorm outflow and high PM 10



# concentrations.

1

# 2U.S. Department of CommerceNational Oceanic & Atmospheric AdministrationQUALITY CONTROLLED LOCALCLIMATOLOGICAL DATA(final)HOURLY OBSERVATIONS TABLECHANDLER MUNICIPAL AIRPORT (53128)CHANDLER, AZ(09/2012)National Climatic Data CenterFederal Building151 Patton AvenueAsheville, North Carolina 28801Elevation: 1243 ft. above sea levelLatitude: 33.268Longitude: -111.812Data 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)123456789101112131415161718192021222306060606060606060606060606060606060547064707490850094710471147124713501450154716501727174718501947204700000000000000000FEW200FEW200FEW200FEW250FEW250FEW060 FEW200FEW060 FEW200FEW070 SCT200FEW070 SCT200SCT070 BKN200SCT070 BKN200VV001BKN070BKN070 OVC200SCT070 OVC200BKN070 BKN200BKN15015.0035.0035.0035.0035.0035.0030.0030.0030.0030.0030.000.25s1.004.0015.0015.0015.00BLDUsBLDUBLDU8181848890939397991009995868686848427.027.029.031.032.034.034.036.037.038.037.035.030.030.030.029.029.0737374757576747575757374727474747423.023.023.524.123.724.223.524.123.823.622.923.222.423.123.123.523.5707070706868666664636164666868707021.021.021.021.020.020.019.019.018.017.016.018.019.020.020.021.021.0696963554844413632302936515555636373356359911923232317617040110030VRVR24027019027029027021021022020015017018403728.5628.5928.6028.6128.6228.6128.5928.5628.5328.4828.4928.5128.5328.5228.5428.5628.61MMMMMMMMMMMMMMMMMAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA29.8829.9129.9229.9329.9429.9329.9129.8829.8529.8029.8129.8329.8529.8429.8629.8829.93Figure A-1.Quality-controlled local climatological data hourly observations table for Chandler Municipal Airport, Chandler, Arizona(09/06/2012). Note in the Weather Type column that BLDU (blowing dust) was reported. For a more detailed explanation of the weather codesshown in the table above, please seehttp://www.nws.noaa.gov/oso/oso1/oso12/document/guide.shtml. Data dynamically generated viahttp://cdo.ncdc.noaa.gov/qclcd/QCLCD.

# 3U.S. Department of CommerceNational Oceanic & Atmospheric AdministrationQUALITY CONTROLLED LOCALCLIMATOLOGICAL DATA(final)HOURLY OBSERVATIONS TABLEGLENDALE MUNICIPAL AIRPORT (53126)GLENDALE, AZ(09/2012)National Climatic Data CenterFederal Building151 Patton AvenueAsheville, North Carolina 28801Elevation: 1066 ft. above sea levelLatitude: 33.527Longitude: -112.295Data 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)1234567891011121314151617181920212223060606060606060606060606060606054706470747084709471047114712471347144715471647173517471847000000000000000FEW120FEW250FEW250FEW250FEW250FEW250FEW100 FEW250FEW100 FEW250FEW100 SCT250FEW080 SCT250SCT080 BKN200SCT080 BKN200SCT080 SCT200 OVC250SCT080 BKN200 OVC250SCT080 BKN180 OVC25020.0020.0020.0020.0020.0020.0020.0020.0020.0020.0020.0020.003.004.0010.00BLDUBLDU84848890909195979910010210097918829.029.031.032.032.033.035.036.037.038.039.038.036.033.031.074737374757576777676767575757523.522.822.823.123.723.924.524.724.424.524.223.924.123.924.170686666686868686666646466687021.020.019.019.020.020.020.020.019.019.018.018.019.020.021.0635948454847413934332931364755639887958111114242522190170200210180200220140200190190190190180230182037323128.7428.7728.7828.7928.8028.7928.7828.7628.7128.6928.6628.6828.6828.6928.74MMMMMMMMMMMMMMMAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA29.8829.9129.9229.9329.9429.9329.9229.8929.8529.8229.7929.8129.8129.8229.87Figure A-2.Quality-controlled local climatological data hourly observationstable for Glendale Municipal Airport, Glendale, Arizona (09/06/2012).Note in the Weather Type column that BLDU (blowing dust) was reported. Dynamically generated viahttp://cdo.ncdc.noaa.gov/qclcd/QCLCD.

# 4U.S. Department of CommerceNational Oceanic & Atmospheric AdministrationQUALITY CONTROLLED LOCALCLIMATOLOGICAL DATA(final)HOURLY OBSERVATIONS TABLEPHOENIX GOODYEAR AIRPORT (03186)GOODYEAR, AZ(09/2012)National Climatic Data CenterFederal Building151 Patton AvenueAsheville, North Carolina 28801Elevation: 968 ft. above sea levelLatitude: 33.416Longitude: -112.383Data 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)123456789101112131415161718192021222306060606060606060606060606060606060547064707470847094710471147124713551455155516471720175518551947204700000000000000000FEW150 FEW250FEW250FEW250FEW250SCT250FEW050 FEW250FEW050FEW050FEW070 SCT250SCT070 SCT250SCT070 SCT180 BKN250SCT070 SCT180 BKN250SCT070 SCT150 OVC200SCT070 SCT150 OVC200SCT070 BKN180 OVC250SCT070 BKN180 OVC250BKN070 BKN150 OVC20010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.003.0010.0010.0010.0010.00BLDU-RA828286889191959599100100100919088868428.028.030.031.033.033.035.035.037.038.038.038.033.032.031.030.029.0747474747576777676767676757675757623.223.223.123.423.924.525.124.524.424.524.524.523.924.424.123.824.5707068686870706866666666687070707321.021.020.020.020.021.021.020.019.019.019.019.020.021.021.021.023.0676755524750444134333333475255597076789896711141725172117212402302302502302602902402602402302302201902302102203429292328.8628.8828.9028.9128.9228.9128.8928.8728.8328.7928.7728.7928.7828.7928.8428.8328.88MMMMMMMMMMMMMMMMMAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA29.8929.9129.9329.9429.9529.9429.9229.9029.8629.8229.8029.8229.8129.8229.8729.8629.91Figure A-3.Quality-controlled local climatological data hourly observations table for Phoenix Goodyear Airport, Goodyear, Arizona(09/06/2012). Note in the Weather Type column that BLDU (blowing dust) was reported. Dynamically generated viahttp://cdo.ncdc.noaa.gov/qclcd/QCLCD.

# 5U.S. Department of CommerceNational Oceanic & Atmospheric AdministrationQUALITY CONTROLLED LOCALCLIMATOLOGICAL DATA (final)HOURLY OBSERVATIONS TABLELUKE AFB AIRPORT (23111)GLENDALE, AZ (09/2012)National Climatic Data CenterFederal Building151 Patton AvenueAsheville, North Carolina 28801Elevation: 1085 ft. above sea levelLatitude: 33.55Longitude: -112.366Data 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)1234567891011121314151617181920212223060606060606060606060606060606060606060606060606060606060606005501550255035504550555065507550831085509551055115512551355145515551655172917301742175117551818185519552055215522552355000000000000000000000000000000CLRCLRCLRCLRCLRCLRCLRCLRCLRCLRCLRCLRCLRCLRCLRCLRCLRFEW090FEW004 SCT090FEW003 SCT090FEW003 SCT090FEW003 BKN080FEW003CB SCT080CBSCT085CBCLRSCT170FEW150CLRFEW150CLR10.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.005.004.005.003.006.006.0010.0010.0010.0010.0010.0010.00HZHZHZBLDUVCTS DUTS DU878685858484848788899193959610010110210099979391918890868583838330.430.029.729.429.028.728.730.731.031.532.733.834.935.837.538.439.037.937.036.034.033.032.931.032.029.929.328.528.428.376767575747473747475757677777776767677777676767575747575747324.324.123.623.623.123.122.823.323.423.623.924.524.824.924.824.424.224.225.024.724.224.524.224.123.723.423.623.723.323.071717070696968686868686969696765646568686870697068697071706921.421.621.321.020.820.419.920.020.019.820.220.520.520.419.318.117.618.620.020.020.021.020.721.020.220.720.921.521.120.859616161616159535250474643423431293237394450495548576167656317141310995111110106561314132131312425252617202114117210200200190200200200200200220170VRVRVR23021025020021021021021021022024020022021018021025343438333228.6828.6928.6928.7028.7128.7128.7428.7528.7528.7628.7628.7628.7428.7128.6828.6428.6328.6328.6428.6428.6428.6528.6628.6928.7028.7028.7428.7428.7528.753330850100200401700302801502002129.7629.7729.7729.7729.7829.7929.8229.8329.8429.8429.8529.8429.8229.7929.7529.7229.7029.7129.7129.7129.72M29.7429.7729.7829.7829.8329.8429.8429.84AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA29.8329.8429.8429.8529.8629.8729.8929.9129.9129.9229.9229.9229.9029.8729.8329.7929.7829.7829.7929.7929.7929.8029.8129.8429.8529.8529.9029.9029.9129.91

# 6Figure A-4.Quality-controlled local climatological data hourly observations table for Luke Air Force Base Airport, Glendale, Arizona(09/06/2012). Note in the Weather Type column that HZ (haze), BLDU (blowing dust),and DU (widespread dust) were reported. Dynamicallygenerated viahttp://cdo.ncdc.noaa.gov/qclcd/QCLCD.U.S. Department of CommerceNational Oceanic & Atmospheric AdministrationQUALITY CONTROLLED LOCALCLIMATOLOGICAL DATA(final)HOURLY OBSERVATIONS TABLEFALCON FIELD AIRPORT (03185)MESA, AZ(09/2012)National Climatic Data CenterFederal Building151 Patton AvenueAsheville, North Carolina 28801Elevation: 1380 ft. above sea levelLatitude: 33.466Longitude: -111.733Data 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)12345678910111213141516171819202122230606060606060606060606060605480647075508470947105511471247144815491647173217500000000000000FEW200FEW200FEW200FEW200FEW150FEW200FEW150TCU SCT200FEW150TCU SCT200FEW080 SCT160FEW080TCU BKN200SCT080TCU BKN200FEW000sSCT080 BKN15030.0030.0030.0030.0035.0035.0035.0035.0035.0035.0030.000.25s2.00BLDUsBLDU828486888891919510099M938628.029.030.031.031.033.033.035.038.037.0M34.030.073737473737474757574M727222.522.823.122.822.823.223.223.823.923.5M22.022.46868686666666666646361616620.020.020.019.019.019.019.019.018.017.016.016.019.063595548484444393131M345165709988101182117050VR050000300300230270250250230190220252528.4128.4428.4528.4628.4628.4528.4428.4128.3428.3428.3428.3528.37MMMMMMMMMMMMMAAAAAAAAAAAAAAAAAAAAAAAAAA29.8929.9229.9329.9429.9429.9329.9229.8929.8129.8129.8129.8329.84Figure A-5.Quality-controlled local climatological data hourly observationstable for Falcon Field Airport, Mesa, Arizona (09/06/2012). Note inthe Weather Type column that BLDU (blowing dust) was reported. Dynamically generated viahttp://cdo.ncdc.noaa.gov/qclcd/QCLCD.

# 7U.S. Department of CommerceNational Oceanic & Atmospheric AdministrationQUALITY CONTROLLED LOCALCLIMATOLOGICAL DATA(may be updated)HOURLY OBSERVATIONS TABLEPHOENIX SKY HARBOR INTL AIRPORT (23183)PHOENIX, AZ (09/2012)National Climatic Data CenterFederal Building151 Patton AvenueAsheville, North Carolina 28801Elevation: 1107 ft. above sea levelLatitude: 33.427Longitude: -112.003Data 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)12345678910111213141516171819202122230606060606060606060606060606060606060606060606060606060606005101510251035104510551065107510851095110511151125113511451155116511733173817471751175718241851195120512151225123511111111111111111111111111111111111111111111111111111111111SCT250SCT250FEW250FEW250FEW250FEW250FEW250FEW250FEW250FEW055 SCT250FEW055 SCT250FEW065FEW075 SCT250FEW075 SCT250FEW075 SCT250SCT070 BKN250FEW070 SCT200 BKN250FEW011 SCT080 BKN200SCT014 SCT080 BKN200BKN014 BKN080 OVC250BKN014 BKN080 OVC250BKN019 BKN080 OVC250SCT025 SCT080 BKN200SCT025 SCT080 BKN200FEW080 BKN200 BKN250FEW080 SCT200 BKN250FEW055 SCT110 OVC160FEW055 SCT110 OVC160FEW110 OVC18010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.001.750.751.502.004.0010.0010.0010.0010.0010.0010.0010.00BLDUBLDUBLDU90898888878686879093939697991001019993939392939193888886858532.231.731.131.130.630.030.030.632.233.933.935.636.137.237.838.337.234.034.034.033.334.033.033.931.131.130.029.429.4747574747473737374767675747575757473747474747475747475747423.423.623.423.423.322.822.822.623.124.224.224.023.523.823.623.823.222.923.523.523.423.523.223.823.123.123.823.323.3676868686867676666686866646463636264666666666667676770696919.420.020.020.020.019.419.418.918.920.020.018.917.817.817.217.216.718.019.019.018.919.019.019.419.419.421.120.620.6475052525353535045444437343230293038414142414443505059595996866660375610105111518161416241316165896270290300300280260230000VR23031030028032027030022020020020021022025028026019011014011017201725252423292428.6628.6828.6828.6828.6928.6928.7228.7328.7428.7428.7328.7128.6928.6628.6228.6228.6328.6328.6328.6328.6328.6328.6428.6628.6828.7328.7328.7328.733230853000500301700202601001701829.7729.7829.7929.7929.7929.8029.8329.8429.8529.8629.8529.8329.8029.7729.7329.7229.74MMM29.74MM29.7829.7929.8529.8529.8529.84AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAASPSPSPAASPSPAAAAAAAAAAAA29.8429.8529.8529.8529.8629.8729.9029.9129.9229.9229.9129.8929.8729.8329.7929.7929.8029.8029.8029.8029.8029.8029.8129.8429.8529.9129.9129.9129.91

# 8Figure A-6.Quality-controlled local climatological data hourly observations table for Phoenix Sky Harbor International Airport, Phoenix, Arizona(09/06/2012). Note in the Weather Type column that BLDU (blowing dust) was reported. Dynamically generated viahttp://cdo.ncdc.noaa.gov/qclcd/QCLCD.U.S. Department of CommerceNational Oceanic & Atmospheric AdministrationQUALITY CONTROLLED LOCALCLIMATOLOGICAL DATA(final)HOURLY OBSERVATIONS TABLESCOTTSDALE AIRPORT (03192)SCOTTSDALE, AZ (09/2012)National Climatic Data CenterFederal Building151 Patton AvenueAsheville, North Carolina 28801Elevation: 1473 ft. above sea levelLatitude: 33.622Longitude: -111.910Data 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)123456789101112131415161718192021222306060606060606060606060606060606060606060606060606060606005301530253035304530553065307530853095310531153125313531453155316531753181218201825185118531953205321532253235312121212121212121212121212121212121212121212121212121212CLRCLRCLRCLRCLRCLRCLRCLRCLRCLRCLRCLRCLRCLRCLRCLRCLRCLRFEW003 SCT090FEW005 SCT030 BKN090FEW005 BKN028 BKN090SCT020SCT018CLRCLRCLRCLRCLR10.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.002.501.503.0010.0010.0010.0010.0010.0010.0010.00HZHZHZ8786858584848386878891959597999998979393939191878786858330.630.029.429.428.928.928.330.030.631.132.835.035.036.137.237.236.736.134.034.034.033.032.830.630.630.029.428.37374747473727372737474757475747575747374747474737372737322.923.123.323.322.822.422.622.422.623.123.223.823.523.823.523.723.623.222.923.523.523.223.222.922.922.422.623.06768696968676866666766666565636464636466666666676766676919.420.020.620.620.019.420.018.918.919.418.918.918.318.317.217.817.817.218.019.019.019.018.919.419.418.919.420.652555959595761515050443937353132333338414144445252515563306003033568089771461511161765606VR00027000000031000028029023029025000025028023022021020023023026026024025022000014020182323242928.2928.2928.2928.2928.3028.3128.3328.3528.3628.3628.3528.3328.3028.2728.2428.2328.2428.2528.2528.2628.2628.2828.2828.3128.3428.3528.3528.353330853000600201600202701202401329.8029.8129.8129.8029.8129.8229.8529.8629.8729.8829.8729.8429.8129.7829.7429.7329.7529.75MMMM29.8029.8329.8629.8729.8629.86AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAASPSPSPSPAAAAAAAAAAAA29.8929.8929.8929.8929.9029.9129.9329.9529.9629.9629.9529.9329.9029.8729.8329.8229.8329.8429.8429.8529.8529.8829.8829.9129.9429.9529.9529.95

# 9Figure A-7.Quality-controlled local climatological data hourly observations table for Scottsdale Airport, Scottsdale, Arizona (09/06/2012). Notein the Weather Type column that HZ (haze)was reported. Dynamically generated viahttp://cdo.ncdc.noaa.gov/qclcd/QCLCD.U.S. Department of CommerceNational Oceanic & Atmospheric AdministrationQUALITY CONTROLLED LOCALCLIMATOLOGICAL DATA(final)HOURLY OBSERVATIONS TABLEWILLIAMS GATEWAY AIRPORT (23104)PHOENIX, AZ(09/2012)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)1234567891011121314151617181920212223060606060606060606060606060606060606060606060606060606001500350055011501350155021502350255031503350355041504350455051505470647074708470947114712471347144715471647000000000000000000000000000CLRCLRCLRCLRCLRCLRCLRCLRCLRCLRCLRCLRCLRCLRCLRCLRFEW120FEW200FEW200SCT200FEW060 SCT200FEW080 SCT100FEW080 SCT100FEW080 SCT100FEW080 SCT100FEW080 SCT100FEW080 BKN20010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0030.0035.0045.0030.0030.0030.0030.0030.0030.0010.0030.00MMMMMMMMMMMMMMMM8282848890939597999999MMMMMMMMMMMMMMMM28.028.029.031.032.034.035.036.037.037.037.0MMMMMMMMMMMMMMMM7474747576767677757574MMMMMMMMMMMMMMMM23.123.123.524.124.424.124.424.723.823.823.5MMMMMMMMMMMMMMMM7070707070686868646463MMMMMMMMMMMMMMMM21.021.021.021.021.020.020.020.018.018.017.0MMMMMMMMMMMMMMMM67676355524441393232310000676555556767787557951111900000000000012012011011009007009008009009009010010011012008010026026025031030024028.4328.4328.4328.4428.4428.4428.4428.4428.4428.4428.4428.4428.4428.4428.4428.4428.4528.4828.4828.4928.5028.4828.4528.4228.3828.3828.38MMMMMMMMMMMMMMMMMMMMMMMMMMMAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA29.8929.8929.8929.9029.9029.9029.9029.9029.9029.9029.9029.9029.9029.9029.9029.9029.9129.9429.9529.9629.9729.9429.9129.8829.8429.8429.84

# 10060606060606060606060606060606060606170017251747184719471955201520352055211521352155221522352255231523352355000000000000000000VV001 BKN080BKN080 OVC150BKN080 OVC120BKN060 BKN100OVCCLRCLRCLRCLRCLRCLRCLRCLRCLRCLRCLRCLRCLR0.50s1.505.0010.0020.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.00DSsBLDUBLDU9088888886MMMMMMMMMMMMM32.031.031.031.030.0MMMMMMMMMMMMM75747374MMMMMMMMMMMMMM23.723.422.823.4MMMMMMMMMMMMMM6868666868MMMMMMMMMMMMM20.020.019.020.020.0MMMMMMMMMMMMM48524852MMMMMMMMMMMMMM17171111691314978998768821021024020015014014014014013014013014013013012013013030232328.4028.4228.4128.42M28.4828.4928.4928.4928.4928.4928.5028.5028.4928.4928.4828.4928.50MMMMMMMMMMMMMMMMMMAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA29.8629.8829.8729.8829.9229.9429.9629.9629.9629.9629.9629.9729.9729.9629.9629.9529.9629.97Figure A-8.Quality-controlled local climatological data hourly observationstable for Williams Gateway Airport, Phoenix, Arizona (09/06/2012).Note in the Weather Type column that BLDU (blowing dust)and DS (dust storm) were reported. Dynamically generated viahttp://cdo.ncdc.noaa.gov/qclcd/QCLCD.

# Exceptional Event, Phoenix, S eptember 6, 2012 Appendix B



# 1 

# Appendix B: Media Coverage, Videos, and Images

Video Links

ADEQ visibil ity cameras in the Phoenix area:

 South Mountain: www.phoenixvis.net/videos/mpeg4/SOMT_09062012.mp4

 Estrella Mountains: www.phoenixvis.net/videos/mpeg4/ESMO_09062012.mp4

 Camelback Mountains: www.phoenixvis.net/videos/mpeg4/CAME_09062012.mp4

 Superstition Mountains: www.phoenixvis.net/videos/mpeg4/SUPM_09062012.mp4

L ocal citizens often create videos during storms, documenting their observations. Here

are links to two such videos.

 Haboob - Dust Storm Rolling over South Mountain - Phoenix, AZ 9/6/12:

http://www.youtube.com/watch?v=2GVWgfygaAg

 September 6, 2012 - Dust Storm Time Lapse:

http://www.youtube.com/watch?v=Zb9OOhA9vOQ (This video is from a YouTube

channel based in Phoenix, Arizona)



# Articles and Image Links

http://www.azcentral.com/news/articles/2011/11/04/20111104arizona-drivers-warned-blowingdust-abrk04-ON.html?nclick_check=1

Dust storm, rain hit Phoenix area

by Domenico Nicosia and Marissa Scott - Sept. 6, 2012 07:21 PM

The Arizona Republic-12 News Breaking News Team

Slow moving thunderstorms northwest of Peoria dropped 2 inches of rain in a one-hour period

Thursday evening after a dust storm swept across the Phoenix metropolitan area.

Storms moving north between Surprise and Sun City got between 0.5 and 0.75 inches of rain,

said Charlotte Dewey, a meteorologist from the National Weather Service.

Various areas throughout the Valley are receiving gusts of wind at approximately 25 mph

following the dissipating dust storm, she said.

Scattered showers helped clear visibility from the approximately 2,500-foot dust wall that

passed through the area, meteorologists said.

Rain probability of up to 60 percent could bring scattered showers and thunderstorms before 11

p.m.

# Exceptional Event, Phoenix, S eptember 6, 2012 Appendix B



# 2 

# The wall that traveled over highways during rush-hour traffic approached the downtown Phoenix

area, at speeds of up to 30 mph and lowered visibility in some areas to one-quarter of a mile.

Phoenix Sky Harbor International Airport expected delays of up to 20 minutes around 5:15 p.m.

that lasted for about an hour, said Deborah Ostreicher, deputy aviations director at the airport.

The opaque cloud diffused slightly and slowed as it headed away from the desert area and

through the downtown buildings.

Motorists who find themselves in the dust are advised to pull to the side of the road and turn off

vehicle lights. The wall of dust was reported near Interstate 10 and Ray Road at 5:10 p.m.

The National Weather Service issued a blowing-dust advisory until 7 p.m. Thursday.

The storm may bring showers and thunderstorms to the Phoenix metropolitan area and may

cause localized flash floods in the evening, said Valerie Meyers, a meteorologist for the National

Weather Service.

The National Weather Service earlier had issued a hazardous-weather outlook for

thunderstorms in the Phoenix area on Thursday night.

There is a 50 to 60 percent chance of rain in the greater Phoenix area, with possible local

flooding and "ponding" of water in parking lots, Meyers said.

Thunderstorm chances continue through Saturday night and Sunday at 30 percent. There is a

10 percent chance of scattered storms on Friday, she said.

Meyers added that this will be a "wet" weekend with storm chances increasing by the day.

Temperatures in the Phoenix metro area will be the same throughout the weekend. The high on

Thursday will be 101, with temperatures remaining in the lower 100s with a high of 102 on

Friday, 103 on Saturday and 103 on Sunday.

http://www.myfoxphoenix.com/story/19478870/2 012/09/06/dust-storm-envelopes-maricopa (go

to link for news video)

Rain comes to wash away dust storm's remnants

Sep 06, 2012 5:15 PM

PHOENIX - It's another day of active weather -- dust storms over the valley and later, rain.

A long line of dust, 2,500 feet tall, crept into the valley from the south Thursday night, right in the

middle of rush hour, reducing visibility for drivers. It wrapped east to west from Phoenix to

Scottsdale as it moved north.

Planes approaching Sky Harbor were seen changing direction to avoid the wall of dust. Some

planes were prevented from takeoff as the storm rolled in.

# Exceptional Event, Phoenix, S eptember 6, 2012 Appendix B



# 3 

# The National Weather Service issued a dust storm warning on Thursday. It expired at 7 p.m.

Wind speeds reached 25 to 35 miles per hour, with gusts up to 40 miles per hour. Visibility was

under a quarter-mile at times, according to NWS.

About 9:30 p.m., rain started falling in downtow n Phoenix to wash away what was left by the

dust storm.

Heavy rain also fell in Tucson. Officials made six swift-water rescues. Most of those involved

motorists who were briefly trapped by floodwaters on desert-area roads.

The monsoon season officially ends Sept. 30.

Driving tips from NWS:

Drivers need to be ready for a sudden drop in visibility.

If you encounter blowing dust or sand on the road or see it approaching, pull off and put your

vehicle in park.

Turn the lights off and keep your foot off the brake pedal.

# Exceptional Event, Phoenix, S eptember 6, 2012 Appendix B



# 4 

# Photos from AZ Central

http://www.azcentral.com/photo/23288

A dust storm moves over the ASU campus in Tempe on Sept. 6, 2012.

PHOTO BY: Cheryl Evans/The Republic.

A dust storm moves through the Phoenix area on Sept. 6, 2012.

PHOTO BY: Pat Shannahan/The Arizona Republic.

# Exceptional Event, Phoenix, S eptember 6, 2012 Appendix B



# 5 A dust storm moves Thursday from the southeast to wards the northwest as it climbs above South

Mountain, with the tower at Sky Harbor International Airport in the foreground.

PHOTO BY: Tom Tingle/The Republic.

South Parking Lot of South Mountain Comm unity College taken at 5:30 on 9.6.2012.

PHOTO BY: Kathleen Hawkins.

# Exceptional Event, Phoenix, S eptember 6, 2012 Appendix B



# 6 A dust storm moves through the Phoenix area on Sept. 6, 2012.

PHOTO BY: Cathie Wilkerson.

Fully Engulfed in Dust! Taken 9.6.2012.

PHOTO BY: Kathleen Hawkins.

# Exceptional Event, Phoenix, S eptember 6, 2012 Appendix B



# 7 A dust storm moves through the metro Phoenix area on Sept. 6, 2012.

PHOTO BY: 12 News.

A dust storm moves through the Phoenix area on Sept. 6, 2012.

PHOTO BY: Kelli Andrews.

# Exceptional Event, Phoenix, S eptember 6, 2012 Appendix C



# 1 RISK LEVEL 

# Appendix C: ADEQ and NWS Forecast Products

MARICOPA COUNTY DUST CONTROL FORECAST

ISSUED Wednesday, September 5, 2012

Three-day weather outlook:

NOTE: DURING THE ACTIVE SUMMER MONSOON PER IODS, STRONG OUTFLOW WINDS FROM EVEN

DISTANT THUNDERSTORMS CAN GENERATE PERIODS OF DENSE BLOWING DUST

Showers and thunderstorms will continue to dance around the pe rimeter of the Phoenix metro area through Friday. We

could see an upswing in moisture over t he weekend with a good shot at some wetting rains by Monday. Until then, dust

remains a possibility. Thus, the risk of exceeding the 24-hr PM10 health standard in Phoenix is forecast to be

Moderate through Saturday, dropping to Low by Sunday.



# R I S K F A C T O R S

WINDS STAGNATION UNHEALTHY PM-10

Day 1: Thu. 9/6/2012 Mostly light winds are

expected except

gusty near

+ thunderstorm out flow

(20% chance of

showers). No significant

stagnation is

expected. = 

# MODERATE

Day 2: Fri. 9/7/2012 Mostly light winds are

expected except

gusty near

thunderstorm out flow

(20% chance of

showers). No significant

+ stagnation is

expected. = 

# MODERATE

Day 3: Sat. 9/8/2012 Mostly light winds are

expected except

gusty near

thunderstorm out flow

(20-30% chance of

showers). No significant

+ stagnation is

expected. = 

# MODERATE

EXTENDED OUTLOOK

Day 4: Sun. 9/9/2012 Mostly light winds are

expected except

gusty near

thunderstorm out flow

(30-40% chance of

showers). No significant

+ stagnation is

expected. = 

# LOW

# Exceptional Event, Phoenix, S eptember 6, 2012 Appendix C



# 2 Day 5: Mon. 9/10/2012 Mostly light winds are

expected except

gusty near

thunderstorm out flow

(40% chance of

showers). No significant

+ stagnation is

expected. = 

# LOW

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/o zone/ensemble.pdf.

JRP 04/28/2011

# Exceptional Event, Phoenix, S eptember 6, 2012 Appendix C



# 3 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

*LINK TO 2012 AIR POLLUTION EXCEEDANCE GRAPH*



# AIR QUALITY FORECAST FOR Thur sday, September 6, 2012, 2012

This report is updated by 1:00 p.m. Sunday thru Friday and is valid

for areas within and bordering Maricopa County in Arizona



# FORECAST

DATE

NOTICES

(*SEE BELOW

FOR DETAILS)

A IR POLLUT A NT 

# YESTERDAY

Tue 09/04/2012

Dust

Highest AQI Reading/Site



# (* Preliminary data only *) 

# TODAY

Wed 09/05/2012

Dust 

# TOMORROW

Thu 09/06/2012

Dust 

# EXTENDED

Fri 09/07/2012

Dust



# O3* 48

Queen Valley 

# 51

Moderate 

# 77

Moderate 

# 84

Moderate



# CO* 7

West Phoenix 

# 7

Good 

# 7

Good 

# 6

Good



# PM-10* 56

West 43rd 

# 72

Moderate 

# 70

Moderate 

# 75

Moderate



# PM-2.5* 44

West Phoenix 

# 48

Good 

# 52

Moderate 

# 56

Moderate

* O3 = Ozone CO = Carbon Monoxide PM-10 = Particles 10 microns & smaller PM-2.5 = Particles smaller than 2.5 microns

*“ 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 concentratio n of OZONE, PM-10, or PM-2.5 may exceed the federal health standard.

“ DUST ” means that short periods of high PM-10 concentrations caused by outfl ow from thunderstorms are possible.

# Exceptional Event, Phoenix, S eptember 6, 2012 Appendix C



# 4 Health Statements

Wednesday, 09/05/2012 

# Unusually sensitive people should consider reducing prolonged or heavy

exertion outdoors.

Thursday, 09/06/2012 

# Unusually sensitive people should consider reducing prolonged or heavy

exertion outdoors.



# SYNOPSIS AND DISCUSSION

Some impressive lightning was seen around the Valley Tuesday night, particularly to the

south. Though no rain made it into the forecast area, the collapsing storms did send some dust

north. Five south Valley PM10 monitors snuck into the Moderate range as a result. With each

passing day, the local soil continues to dry out. This will make it easier for the top soil to become

airborne with outflow from nearby storms. Models suggest an upswing in thunderstorm activity

heading into the weekend. We're keeping the fore casted PM10 concentrations in the middle part

of the Moderate range as a result.

Ozone concentrations remained in the Good rang e of the Air Quality Index (AQI) on Tuesday.

NOAA's Air Quality model predicts higher concentra tions in the east part of the Valley the next

few days. This is feasible as high pressure remains overhead. For now, we are keeping the

forecasted ozone levels below Health Watch criter ia, but that may change if this latest upswing

proves to be significant.

Check back tomorrow for the latest. Until then, have a good day! -J.Paul

MONITORING SITE MAPS

ST A TIC M A P htt p : / / www.azde q

. g o v / en v iron/air/monitorin g/ ima g es / ma p

. j pg

http://aqwww.maricopa.gov/AirMonitoring/SitePollutionMap.aspx

http://156.42.96.39/alert/Google/air.html INTERACTIVE MAPS

http://www.airnow.gov/



# POLLUTION MONITOR READINGS FOR Tuesday, September 4, 2012



# 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 

# 43 36

Apache Junction 

# 49 42

Blue Point 

# 56 47

Buckeye 

# 43 36

Casa Grande 

# 46 39

Cave Creek 

# 47 40

Central Phoenix 

# 50 42

Dysart 

# 42 36

Falcon Field 

# 53 45

Fountain Hills 

# 50 42

Glendale 

# 43 36

Humboldt Mountain 

# NOT AVBL NOT AVBL NOT AVBL

Phoenix Supersite 

# 46 39

North Phoenix 

# 51 43

Pinal Air Park 

# 50 42

Pinnacle Peak 

# 56 47

Queen Valley 

# 57 48

Rio Verde 

# NOT AVBL NOT AVBL NOT AVBL

South Phoenix 

# 50 42

# Exceptional Event, Phoenix, S eptember 6, 2012 Appendix C



# 5 South Scottsdale 

# 53 45

Tempe 

# 50 42

Tonto Nat’l Mon. 

# 47 40

West Chandler 

# 50 42

West Phoenix 

# 49 42

Yuma 

# 38 32



# 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 

# 0.6 7



# PM-10 (PARTICLES)

SITE NAME MAX 24-HR VALUE (μg/m3) 

# MAX AQI AQI COLOR CODE

Apache Junction 

# 22.2 21

Buckeye 

# 63.0 55

Central Phoenix 

# NOT AVBL NOT AVBL NOT AVBL

Combs School (Pinal County) 

# 45.8 42

Durango 

# 63.8 55

Dysart 

# 41.2 38

Glendale 

# 46.8 43

Greenwood 

# 61.4 54

Higley 

# 41.7 38

Maricopa (Pinal County) 

# NOT AVBL NOT AVBL NOT AVBL

North Phoenix 

# 49.2 45

Phoenix Supersite 

# 51.9 47

South Phoenix 

# 35.0 32

Tempe 

# 37.4 34

West Chandler 

# 31.9 29

West Forty Third 

# 65.3 56

West Phoenix 

# 55.9 51

Zuni Hills 

# 41.8 38



# 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 

# 10.3 33

Dysart 

# 8.5 28

Estrella Mountain Park 

# 9.5 31

Glendale 

# 8.5 28

Phoenix Supersite 

# 7.7 25

North Phoenix 

# 8.8 29

South Phoenix 

# 7.5 24

Tempe 

# NOT AVBL NOT AVBL NOT AVBL

Vehicle Emissions Lab 

# 6.9 22

West Phoenix 

# 13.4 44

# Exceptional Event, Phoenix, S eptember 6, 2012 Appendix C



# Statements, Advisories, and Warnings issued by the National Weather Service office in

Phoenix, AZ pertaining to this dust storm event:

URGENT - WEATHER MESSAGE

NATIONAL WEATHER SERVICE PHOENIX AZ

416 PM MST THU SEP 6 2012

AZZ028-070100-

/O.NEW.KPSR.DS.W.0016.120906T2316Z-120907T0100Z/

NORTHWEST AND NORTH CENTRAL PINAL COUNTYINCLUDING THE CITIES OF...APACHE JUNCTION...CASA GRANDE...

FLORENCE

416 PM MST THU SEP 6 2012

...DUST STORM WARNING IN EFFECT UNTIL 6 PM MST THIS EVENING...

THE NATIONAL WEATHER SERVICE IN PHOENIX HAS ISSUED A DUST STORM

WARNING...WHICH IS IN EFFECT UNTIL 6 PM MST THIS EVENING.

POWERFUL THUNDERSTORMS SOUTH AND SOUTHWEST OF CASA GRANDE HAVE

GENERATED STRONG NORTHWARD MOVING WIND GUSTS THAT HAVE KICKED UP

DUST WITH VISIBILITIES BELOW 1/4 MILE AT TIMES.

* AFFECTED AREA...PORTIONS OF PINAL COUNTY NEAR THE CITIES OF CASA

GRANDE...MARICOPA...STANFIELD...COOLIDGE...SACATON...AND NEARBY

PORTIONS OF INTERSTATE 10 BETWEEN CASA GRANDE AND PHOENIX.

* TIMING...DUST STORM WARNING THROUGH 6 PM.

* WINDS...20 TO 30 MPH WITH GUSTS TO 40 MPH.

* VISIBILITY...LESS THAN 1/4 MILE AT TIMES.

* IMPACTS...DANGEROUSLY LOW VISIBILITIES IN DENSE BLOWING DUST.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

BE READY FOR A SUDDEN DROP IN VISIBILITY TO NEAR ZERO. IF YOU

ENCOUNTER BLOWING DUST OR BLOWING SAND ON THE ROADWAY OR SEE IT

APPROACHING...PULL OFF THE ROAD AS FAR AS POSSIBLE AND PUT YOUR

VEHICLE IN PARK. TURN THE LIGHTS ALL THE WAY OFF AND KEEP YOUR

FOOT OFF THE BRAKE PEDAL.

REMEMBER...PULL ASIDE...STAY ALIVE.

6

# Exceptional Event, Phoenix, S eptember 6, 2012 Appendix C



# BULLETIN - EAS ACTIVATION REQUESTED

SEVERE THUNDERSTORM WARNING

NATIONAL WEATHER SERVICE PHOENIX AZ

419 PM MST THU SEP 6 2012

THE NATIONAL WEATHER SERVICE IN PHOENIX HAS ISSUED A

* SEVERE THUNDERSTORM WARNING FOR...

WEST CENTRAL PINAL COUNTY IN SOUTH CENTRAL ARIZONA...

INCLUDING THE AREAS NEAR STANFIELD...WEST CASA GRANDE...

NORTHWARD TO THE TOWN OF MARICOPA.

* UNTIL 500 PM MST

* AT 412 PM MST...NATIONAL WEATHER SERVICE METEOROLOGISTS DETECTED

SEVERE THUNDERSTORMS CAPABLE OF PRODUCING DAMAGING WINDS IN

EXCESS OF 60 MPH. THIS STORM WAS LOCATED 15 MILES SOUTH OF

MARICOPA...OR 19 MILES WEST OF CASA GRANDE. THIS STORM WAS

NEARLY STATIONARY.

* THE SEVERE THUNDERSTORM WILL OTHERWISE REMAIN OVER MAINLY RURAL

AREAS OF THE INDICATED COUNTY.

PRELIMINARY LOCAL STORM REPORT

NATIONAL WEATHER SERVICE PHOENIX AZ

429 PM MST THU SEP 06 2012

..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...

..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....

..REMARKS..

0410 PM DUST STORM CASA GRANDE 32.89N 111.74W

09/06/2012 PINAL AZ AMATEUR RADIO

0.25 MILE VISIBILITY IN BLOWING DUST

PRELIMINARY LOCAL STORM REPORT

NATIONAL WEATHER SERVICE PHOENIX AZ

431 PM MST THU SEP 06 2012

..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...

..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....

..REMARKS..

0415 PM DUST STORM 1 WSW COOLIDGE 32.98N 111.54W

09/06/2012 PINAL AZ TRAINED SPOTTER

VISIBILITY LESS THAN 0.25 MILE IN BLOWING DUST

7

# Exceptional Event, Phoenix, S eptember 6, 2012 Appendix C



# SHORT TERM FORECAST

NATIONAL WEATHER SERVICE PHOENIX AZ

437 PM MST THU SEP 6 2012

AZZ023-070145-

GREATER PHOENIX AREAINCLUDING THE CITIES OF...BUCKEYE...CAREFREE...CAVE CREEK...

CHANDLER...FOUNTAIN HILLS...GILBERT...GLENDALE...MESA...PEORIA...

PHOENIX...SCOTTSDALE...SUN CITY...AND TEMPE

437 PM MST THU SEP 6 2012

.NOW...

GUSTY SOUTH WINDS 25 TO 35 MPH WITH GUSTS 40 MPH...GENERATED FROM

POWERFUL THUNDERSTORMS NEAR CASA GRANDE...WILL MOVE THROUGH THE

AHWATUKEE...CHANDLER...TEMPE...AND PHOENIX AREAS BETWEEN 5 PM AND 7

PM. A DUST STORM WITH VISIBILITIES UNDER 2 MILES AT TIMES WILL ALSO

MOVE THROUGH THE AREA.

GREATER PHOENIX AREAINCLUDING THE CITIES OF...MESA...PHOENIX

441 PM MST THU SEP 6 2012

...BLOWING DUST ADVISORY IN FOR PHOENIX EFFECT UNTIL 7 PM MST THIS

EVENING...

THE NATIONAL WEATHER SERVICE IN PHOENIX HAS ISSUED A BLOWING DUST

ADVISORY FOR THE GREATER PHOENIX AREA...WHICH IS IN EFFECT UNTIL 7 PM

MST THIS EVENING.

* AFFECTED AREA...FIRST AHWATUKEE...CHANDLER...TEMPE...MESA... THE

SPREADING INTO DOWNTOWN PHOENIX NORTHWARD.

* TIMING...BETWEEN 455 PM AND 7 PM.

* WINDS...SOUTH WINDS 25 TO 35 MPH WITH GUSTS TO 40 MPH.

* VISIBILITY...UNDER 1 MILE AT TIMES.

* IMPACTS...DANGEROUSLY LOW VISIBILITIES FOR MOTORISTS.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

BE READY FOR A SUDDEN DROP IN VISIBILITY. IF YOU ENCOUNTER

BLOWING DUST OR BLOWING SAND ON THE ROADWAY OR SEE IT

APPROACHING...PULL OFF THE ROAD AS FAR AS POSSIBLE AND PUT YOUR

VEHICLE IN PARK. TURN THE LIGHTS ALL THE WAY OFF AND KEEP YOUR

FOOT OFF THE BRAKE PEDAL.

REMEMBER...PULL ASIDE...STAY ALIVE.

8

# Exceptional Event, Phoenix, S eptember 6, 2012 Appendix C



# URGENT - WEATHER MESSAGE

NATIONAL WEATHER SERVICE PHOENIX AZ

452 PM MST THU SEP 6 2012

AZZ023-070200-

/O.UPG.KPSR.DU.Y.0048.000000T0000Z-120907T0200Z/

/O.EXB.KPSR.DS.W.0016.000000T0000Z-120907T0200Z/

GREATER PHOENIX AREAINCLUDING THE CITIES OF...MESA...PHOENIX

452 PM MST THU SEP 6 2012

...DUST STORM WARNING IN EFFECT UNTIL 7 PM MST THIS EVENING...

THE NATIONAL WEATHER SERVICE IN PHOENIX HAS ISSUED A DUST STORM

WARNING...WHICH IS IN EFFECT UNTIL 7 PM MST THIS EVENING. THE

BLOWING DUST ADVISORY ISSUED EARLIER IS NO LONGER IN EFFECT.

* AFFECTED AREA...FIRST AHWATUKEE...CHANDLER...TEMPE...MESA...THEN

SPREADING NORTHWARD INTO PHOENIX.

* TIMING...THROUGH 7 PM.

* WINDS...SOUTH WINDS 25 TO 35 MPH WITH GUSTS TO 40 MPH.

* VISIBILITY...UNDER 1/4 MILE AT TIMES.

* IMPACTS...DANGEROUSLY LOW VISIBILITIES FOR MOTORISTS.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

BE READY FOR A SUDDEN DROP IN VISIBILITY TO NEAR ZERO. IF YOU

ENCOUNTER BLOWING DUST OR BLOWING SAND ON THE ROADWAY OR SEE IT

APPROACHING...PULL OFF THE ROAD AS FAR AS POSSIBLE AND PUT YOUR

VEHICLE IN PARK. TURN THE LIGHTS ALL THE WAY OFF AND KEEP YOUR

FOOT OFF THE BRAKE PEDAL.

REMEMBER...PULL ASIDE...STAY ALIVE.

PRELIMINARY LOCAL STORM REPORT

NATIONAL WEATHER SERVICE PHOENIX AZ

527 PM MST THU SEP 06 2012

..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...

..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....

..REMARKS..

0524 PM DUST STORM 3 E MESA RIVERVIEW MALL 33.43N 111.82W

09/06/2012 MARICOPA AZ TRAINED SPOTTER

VSBY LESS THAN 0.25 MI.

9

# Exceptional Event, Phoenix, S eptember 6, 2012 Appendix C



# 10 PRELIMINARY LOCAL STORM REPORT

NATIONAL WEATHER SERVICE PHOENIX AZ

555 PM MST THU SEP 06 2012

..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...

..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....

..REMARKS..

0543 PM DUST STORM 4 SW WITTMANN 33.74N 112.58W

09/06/2012 MARICOPA AZ TRAINED SPOTTER

LESS THAN 0.25 MI. VSBY

# Exceptional Event, Phoenix, S eptember 6, 2012 Appendix D



# Appendix D:

Affidavit of Public Notice

1