# State of Arizona Exceptional Event

Documentation for the Event of

September 2, 2011, for the Phoenix PM 10



# Nonattainment Area

Final Report Prepared for

Arizona Department of Environmental Quality

Phoenix, AZ

January 23, 2013

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

# State of Arizona Excepti onal Event Documentation

for the Event of September 2, 2011,

for the Phoenix PM 10 

# Nonattainment Area

Final Report

STI-912091-5546-DFR



# 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

January 23, 2013

Cover ima ge depicts suspended dust and haze in the Phoe nix area at 0910 LST on Sept ember 2, 2011, resulting

from thunderstorm outflow that transported dust into the re gion several hours prior. This photo was taken by an

ADEQ visibility camera in downtown Phoenix, looking northeastward toward Camelback Mountain.

## Exceptional Event, Phoenix, September 2, 2011 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 2, 2011 Table of Contents



# Table of Contents

Section Page

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, Monsoon, and Thunderstorms .....................................................................5

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

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

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

3.2 Summary ....................................................................................................................6

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

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

4.2 Summary ....................................................................................................................1

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 2, 2011 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 Not Reasonably Preventable

..................................... Error! Bookmark not defined.

7.7 But For .......................................................................................................................2

Appendix A...................................................... .....................................................A-1

Appendix B...................................................... .....................................................B-1

Appendix C...................................................... .....................................................C-1

Appendix D...................................................... .....................................................D-1

Appendix E...................................................... .....................................................E-1

## Exceptional Event, Phoenix, Septem ber 2, 2011 List of Figures



# List of Figures

Figure Page

2-1. Location of air quality and meteorological monitors mentioned in this report and

relevant geographical features in the Phoenix area..........................................................2

2-2. Location of air quality sites monitoring PM statewide on September 2, 2011................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

2-6. Outflow boundaries from thunderstorms over northwest Mexico and south-central

Arizona moved northward and transported dust into the Phoenix area on

September 2, 2011............................................................................................................7

3-1. Infrared satellite image from 0000 LST on September 2, 2011 (GOES-West). ................1

3-2. Phoenix area air quality and meteorological monitors.......................................................2

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

September 2-3, 2011. .......................................................................................................4 10



# 3-4. Hourly PM concentrations and wind speeds at the Higley monitor on September

1-2, 2011. ..........................................................................................................................4 10



# 3-5. Radar base velocity data at 0150 LST on September 2, 2011, from NWS Phoenix

Doppler radar. ...................................................................................................................5

3-6. Hourly PM concentrations at Phoenix area monitors and visibility at KPHX. .................6 10



# 4-1. 24-hr average PM concentrations at the Central Phoenix monitor (2007-2011)............1 10



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

vii

## Exceptional Event, Phoenix, Septem ber 2, 2011 List of Tables



# List of Tables

Table Page

2-1. Statewide monitor information and PM measurements on September 2, 2011.............7 10



# 3-1. Observed wind speeds and wind gusts at Maricopa County monitors on

September 2, 2011............................................................................................................3

5-1. Rules and ordinances regulating particulate matter 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 Maricopa

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



## viii

## Exceptional Event, Phoenix, September 2, 2011 Int roduction



## 1 

# ral events. 

# 1. Introduction

On September 2, 2011, 11 air quality monitors in the Phoenix PM 10 

# nonattainment area

recorded 24-hr average PM 10 

# concentrations in excess of the National Ambient Air Quality

Standard (NAAQS) 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, therefore, is an Exceptional Event as def ined by the U.S. Environmental Protection

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



# 1.1 Report Contents

Section 2 of this assessment contains a c onceptual model of the wind-blown dust event

that transpired on September 2, 2011, providing a background narrative of the exceptional event

and an overall explanation that the event affected ai r 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 2, 2011, and the exceedances of the 24-hr PM 10 

# standard at the

monitoring stations. The evidence in this section also confirms that the event in question both

affected air quality and was the result of natu

Section 4 of this assessment illustrates that the event of September 2, 2011, 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 2, 2011, was not reasonably controllable or preventable.

Section 6 of this assessment builds upon the demonstration, showing a clear causal

connection between the natural event and the exceedances, and concludes that the

exceedances of the 24-hr PM 10 

# standard on September 2, 2011, 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 media coverage pertaining to this dust storm event. Appendix C

contains time-series graphs to supplement Section 4. Appendix D contains air quality forecasts

issued by the Arizona Department of Environm ental Quality (ADEQ) and weather statements

and warnings issued by the National Weather Service. Appendix E 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

## Exceptional Event, Phoenix, September 2, 2011 Introduction



## 2 

# flagging of t hese data.



# cess Was Followed for Event

Document ation (40 CFR 50.14(c)(3)(iv))

ay monitoring data. This section of the report contains the requirements of the EER and

associat ed guidance, and discusses how ADEQ addressed those requirements.



# 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 2, 2011. More

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

forecast products that were issued pertaining to the September 2, 2011 event are included in

Appendix D.



# 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 2, 2011, 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, 20 12, listing all days from calendar year

2011 that ADEQ intends to analyze under the Exceptional Events Rule. The PM 10 

# exceedances that occurred on September 2, 2011, in the Phoenix PM 10 

# nonattainment area

were included on this list. This assessment report serves as demonstration supporting the



# 1.2.4 Document That the Public Comment Pro

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-d

## Exceptional Event, Phoenix, September 2, 2011 Introduction



## 3 

# ements of 40

CFR 50.14(c)(3)(iv). See Appendix E for a copy of the affidavit of public notice.



# stration Supporting Exceptional Event Flag (40 CFR

50.14(a)(1-2))

to

s

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

2014.



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

ion of air quality monitoring data,

evidence must be provided for the f ollowing elements:

h in 40 CFR 501(j) that

activity unlikely to recur in a particular

nship between the measurement(s) under

h a measured concentration(s) in excess of normal

. There would have been no exceedance or violation but for the event. public comment period on December 3, 2012. A copy of the public notice certification, along

with any comments rec eived, will be submitted to EPA, consistent with the requir



# 1.2.5 Submit Demon

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

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 headquarter

in San

The EER states that in order to justify the exclus

1. The event satisfies the criteria set fort

a. the event affected air quality,

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

c. the event was caused by human

lo cation or was a natural event;

2. There is a clear causal relatio

co nsideration and the event;

3. The event is associated wit

hi storical fluctuations; and

4

## Exceptional Event, Phoenix, Sept ember 2, 2011 Conceptual Model



## 1 

# 2

. Conceptual Model

This section provides a narrative background and summarizes the meteorological and

air quality conditions in place on September 2, 2011, in the Phoenix area. Elements described

in this section include

 A description and map of 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 msl) to the northeast, the

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

White Tank Mountains (~4,500 ft msl) to the west, the Sierra Estrella (~4,450 ft msl) to the

southwest, and the Superstition Mountains (~5,000 ft msl) far to the east. Within the City are

the Phoenix Mountains (~2,600 ft msl) and South Mountain (~2,600 ft msl). Current

development is pushing north, west, and 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 locations of

meteorological monitors and the PM 10 

# monitors that recorded exceedances on September 2,

2011. It should be noted that some of the monitors shown in Figure 2-1 are filter-based

monitors; therefore, monitoring data from all locations may only be available for select days (i.e.,

1-in-6 run days). AQS monitors measure both air quality and meteorological data. 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. Arizona Meteorological Network (AZMET) and

National Weather Service (NWS) monitors measure meteorological data only. Several Arizona

AZMET and NWS sites are in operation in the Phoenix area. Phoenix Sky Harbor International

Airport (KPHX) was the primary NWS site used in this demonstration package because of that

site’s high data quality, data completeness, proximity to AQS sites, and representativeness of

meteorological conditions in the Phoenix area. Figure 2-2 shows monitors statewide measuring

PM 10 

# on September 2, 2011.

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 air quality monitors thatrecorded exceedances of the 24-hr PM10NAAQS and meteorological monitorsin the Phoenix area.

## Exceptional Event, Phoenix, Sept ember 2, 2011 Conceptual Model



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

## in Arizona on September 2, 2011.

## Exceptional Event, Phoenix, Sept ember 2, 2011 Conceptual Model



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

## Exceptional Event, Phoenix, Sept ember 2, 2011 Conceptual Model



## 5 

# 2. 2 Climate, Monsoon, and Thunderstorms

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 July through early September 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.

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 outflow boundaries (also called gust

fronts; see 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 2, 2011 Conceptual Model



## 6 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, extremely hot temperatures act to 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 encompass 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 early morning of September 2, 2011, gusty winds generated by thunderstorms

over northwestern Mexico and south-central Arizona transported dust northward into the

Phoenix area ( Figure 2-6 ). The windblown dust resulted in 24-hr average PM 10 

# concentrations

in exceedance of the NAAQS at 11 air quality monitors in the Phoenix area ( Table 2-1 ). The

PM 10 

# concentrations measured at these monitors were in excess of normal historical

fluctuations. The dust was naturally occurring and likely originated over undeveloped lands of

northwestern Mexico and southern Arizona outside the city of Phoenix, and wind gusts in

excess of 40 mph overwhelmed reasonable dust control measures. Monitors across the

Phoenix metropolitan area, as well as in Pinal and Pima Counties, recorded high PM 10 

## 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.

## Exceptional Event, Phoenix, Sept ember 2, 2011 Conceptual Model



## 7 

# concentrations as the windblown dust moved through, illustrating the widespread nature of this

event.



# Region of

thunderstorm

development 

# Phoenix

Pima Pinal Maricopa

Figure 2-6. Outflow boundaries from thunderstorms over northwest Mexico and

south-central Arizona moved northward a nd transported dust into the Phoenix area on

September 2, 2011.

Table 2-1. Statewide monitor information and PM10 measurements on September 2,

2011. The exceedance monitors discussed in this report are shown in bold.

Page 1 of 3



## 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

Maricopa County

Buckeye TEOM MC 04-013-4011-81102-1 169 736 200 RJ

Central Phoenix TEOM MC 04-013-3002-81102-4 308 4392 200 RJ

Durango

Complex TEOM MC 04-013-9812-81102-1 255 3217 200 RJ

Dysart TEOM MC 04-013-4010-81102-1 119 504 300

## Exceptional Event, Phoenix, Sept ember 2, 2011 Conceptual Model



## 8 Table 2-1. Statewid e monitor information and PM10 measurements on September 2,

2011. The 11 Phoenix-area monitors discussed in this report are shown in bold font.

Page 2 of 3



## 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

Fort

McDowell/Yuma

Frank TEOM FMIR 04-013-5100-8112-1 195 N/A N/A

Glendale TEOM MC 04-013-2001-81102-1 132 621 200

Greenwood TEOM MC 04-013-3010-81102-1 198 2062 200 RJ

Higley TEOM MC 04-013-4006-81102-1 213 1289 200 RJ

JLG Supersite BAM ADEQ 04-013-9997-81102-3 150 985 200

JLG Supersite TEOM ADEQ 04-013-9997-81102-4 208 2600 200 RJ

North Phoenix TEOM MC 04-013-1004-81102-1 115* 390 300

South Phoenix TEOM MC 04-013-4003-81102-1 339 4163 200 RJ

West Chandler TEOM MC 04-013-4004-81102-1 387 3327 200 RJ

West 43 rd 

## Avenue TEOM MC 04-013-4009-81102-1 219 2523 200 RJ

West Phoenix TEOM MC 04-013-0019-81102-1 133 294 300

Zuni Hills TEOM MC 04-013-4016-81102-1 110 484 300

Apache County

N/A N/A WMAT 04-001-1003-81102-1 10 24 1500

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 68 180 1300 IJ

Navajo County

N/A N/A WMAT 04-017-1002-81102-1 14 42 1400

Pima County

Ajo TEOM ADEQ 04-019-0001-81102-3 150 485 200 IJ

Geronimo BAM PCDEQ 04-019-1113-81102-1 46 137 1400

Green Valley BAM PCDEQ 04-019-1030-81102-1 27 89 1600

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

Rillito TEOM ADEQ 04-019-0020-81102-3 77 222 1300 IJ

South Tucson FRM PCDEQ 04-019-1001-81102-1 47 N/A N/A

Pinal County

Apache Junction

Fire Station TEOM PCAQCD 04-021-3002-81102-3 217 1441 200 RJ

Casa Grande

Downtown TEOM PCAQCD 04-021-0001-81102-3 235 3143 100 RJ

Combs School TEOM PCAQCD 04-021-3009-81102-3 186 2218 200 RJ

Cowtown TEOM PCAQCD 04-021-3013-81102-3 588 7909 200 RJ

Maricopa TEOM PCAQCD 04-021-3010-81102-3 257 2786 200 RJ

## Exceptional Event, Phoenix, Sept ember 2, 2011 Conceptual Model



## 9 Table 2-1. Statewide monitor information and PM10 measurements on September 2,

2011. The 11 Phoenix-area monitors discussed in this report are shown in bold font.

Page 3 of 3



## 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

Pinal County

Housing TEOM PCAQCD 04-021-3011-81102-3 310 4135 100 RJ

Stanfield TEOM PCAQCD 04-021-3008-81102-3 268 2542 200 RJ

Santa Cruz County

Nogales Post

Office BAM ADEQ 04-023-0004-81102-3 27 65 2100

Yuma County

Yuma Supersite TEOM ADEQ 04-027-8011-81102-3 N/A N/A N/A

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

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

TEOM: Tapered element oscillating microbalance monitor

BAM: Beta attenuation monitor

FRM: Federal reference method

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

MC: Maricopa County Air Quality Department

ADEQ: Arizona Department of Environmental Quality

FMIR: Fort McDowell Indian Reservation

PCAQCD: Pinal County Air Quality Control District

PCDEQ: Pima County Department of Environmental Quality

RJ: qualifier flag for high winds

IJ: qualifier flag for high winds

## Exceptional Event, Phoenix, September 2, 2011 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 2, 2011. On the evening of September 1, intense thunderstorms developed over

the higher terrain of northwestern Mexico northward into far southern Arizona ( Figure 3-1 ).

These thunderstorms expanded northward and weakened, but the thunderstorms generated

dust-carrying outflow boundaries that propagated into the Phoenix area early on September 2.

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 regions for PM 10 

# during the September 2, 2011 event were the deserts of far northwestern Mexico and along the

path of the outflow boundary from those deserts northward through Pima, Pinal, and southern

Maricopa Counties. This region largely consists of natural, undisturbed desert. In addition, the

month leading up to the September 2, 2011 event was very dry in the Phoenix area, with the

last measureable rainfall at KPHX occurring on August 3. 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 midnight LST on September 2, 2011

(GOES-West). Colder temperatures (blues, pu rples, and white) indicate tall, convective

(thunderstorm) clouds. Thunderstorms ov er northwestern Mexico generated outflow

boundaries that carried dust northwestward into Arizona.

1

## Exceptional Event, Phoenix, September 2, 2011 Causal Relationship



# Figure 3-2 and Table 3-1 summarize the progression of the thunderstorm outflow and

windblown dust as it moved into the Phoenix area. The dust-laden outflow arrived in the

Phoenix area around 0100 LST on September 2. PM 10 

# concentrations at the West Chandler

( Figure 3-3 ), Higley ( Figure 3-4 ), and other monitors ( Appendix A ) increased sharply over this

time period, with 1-hr PM 10 

# concentrations exceeding 3,000  g/m 3 

# at some monitors. Several

wind monitors in the Phoenix area measured sustained winds of over 20 to 25 mph and wind

gusts in excess of 30 mph coincident with the sharp increase in PM 10 

# concentrations. The

thunderstorm outflow and associated strong winds were also evident on the NWS Doppler radar

in Phoenix ( Figure 3-5 ). In addition, visibility at KPHX and other regional airports decreased

significantly with the arrival of the strong winds and blowing dust ( Figure 3-6 ). Visibility

cameras in the Phoenix area showed hazy conditions after sunrise on September 2, 2011, likely

due to suspended dust from the outflow boundary that moved through earlier that morning.

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 and PM 10 

# concentrations were much lower,

illustrating the correlation between the high winds and the dust.

Figure 3-2. Phoenix area air quality and meteorological monitors. Wind and PM 10 

## data

and time of observation are shown in Table 3-1. Gusty south-to-southwesterly winds

transported dust into the Phoenix area early on September 2, 2011. Circular symbols

and numbers are placed at the location of the monitor site; wind barbs are offset for

visual clarity.

2

## Exceptional Event, Phoenix, September 2, 2011 Causal Relationship



## Table 3-1. Observed wind speeds and wind gusts at Phoenix area monitors on

September 2, 2011. Symbols in the first co lumn correspond to monitor locations in

Figure 3-2. All exceedance monitors reported high PM 10 

## concentrations at 0200 LST on

September 2, 2011, coincident with high wind gusts.

Monitor 1-hr Max

PM 10 

## (  g/m 3 

## ) Time of

Observation

(LST) Wind

Speed

(mph) Wind

Gust

(mph) Wind

Direction

(degrees)

KIWA

- 0105 31 37 180

Buckeye 735 0200 8 25 219

Central

Phoenix 4392 0200 9 28 204

Durango

Complex 3217 0200 5 19 204

Greenwood 2062 0200 5 17 201

Higley 1289 0200 12 27 205

JLG Supersite 2600 0200 5 15 197

South Phoenix 4163 0200 9 26 188

West 43 rd



## Avenue 2523 0200 7 19 212

West Chandler 3327 0200 16 34 198

Maricopa

- 0200 21 32 166

Paloma

- 0200 20 28 202

Queen Creek

- 0200 17 32 189

KPHX

- 0209 28 35 180

KBXK

- 0215 20 25 230

KLUF

- 0229 28 34 240

KDVT

- 0251 21 26 230

North Phoenix 390 0300 5 13 263 

# 5

9

8

1

2

3

11

5

7

6

2

3

1

4

1

2

3

4

3

## Exceptional Event, Phoenix, September 2, 2011 Causal Relationship



## Figure 3-3. Hourly PM 10 

## concentrations and wind speeds at the West Chandler monitor

on September 2-3, 2011. PM 10 

## concentrations sharply increased at 0100 LST on

September 2, 2011, coincident with gusty winds , indicating the arrival of windblown dust.

Note that PM 10 

## concentration was not available at 800 LST on September 1, 2011 at the

West Chandler monitor.

Figure 3-4 . Hourly PM 10 

## concentrations and wind speeds at the Higley monitor on

September 1-2, 2011. PM 10 

## concentrations sharply increased at 0100 LST on

September 2, 2011, coincident with gusty winds , indicating the arrival of windblown dust.

4

## Exceptional Event, Phoenix, September 2, 2011 Causal Relationship



## Figure 3-5. Radar base velocity data at 0150 LST on September 2, 2011, from NWS

Phoenix Doppler radar. Green indicates flow toward the radar; orange and red indicate

flow away from the radar. A well-defined outflow boundary (dashed line) approached the

Phoenix area from the south. This boundary carried dust northward and westward

across the Phoenix metropolitan area.

5

## Exceptional Event, Phoenix, September 2, 2011 Causal Relationship



## Figure 3-6. Hourly PM 10 

## concentrations at Phoenix area monitors and visibility at KPHX.

Visibility was greatly reduced at 0200 LST on September 2, coincident with the sharp

increase in PM 10 

## concentrations at Phoenix area monitors, indicating the arrival of

windblown dust.



# PM 10 

# concentrations decreased after 0400 LST as the dust storm propagated northward

out of the Phoenix area. Monitors across the Phoenix metropolitan area and areas further south

in Arizona, including Tucson, reported gusty winds and sharp increases in PM 10 

# concentrations, illustrating the widespread nature of this dust storm event. No measurea

rainfall was reported in Phoenix with the passage of this outflow boundary and the assoc ble

iated

dust.



# 3.2 Summary

n

x

wind speeds

and wind gusts, and that the strong winds were experienced over a large area. The information presented in this section demonstrates a clear causal relationship

between the windblown dust and the PM 10 

# exceedance measured at Phoenix area monitors o

September 2, 2011. The radar and wind data shown in this section illustrate the spatial and

temporal representation of the dust storm as it moved through the Phoenix area. In addition,

the time series plots of air quality and meteorological data found in this section and in Appendi

A show that the sharp increase in PM 10 

# concentrations coincided with the strong

6

## Exceptional Event, Phoenix, September 2, 2011 Historical Norm



# 4. Historical Norm

4. 1 Analysis

PM 10 

# concentrations measured at Phoenix area monitors on September 2, 2011, were

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

PM 10 

# concentrations measured on September 2, 2011, were compared to a historical

2007-2011 five-year annual data set at each monitor ( Figure 4-1 and Appendix C ). The PM 10 

# concentrations measured at the Central Phoenix monitor (Figure 4-1) and other monitors on

September 2, 2011, resulted in some of the high est 24-hr averages measured over the five-year

period. Similar time-series plots for the other Phoenix area monitors with exceedances are

shown in Appendix C. The graphs also highlight the July to September 2011 season, which had

many unusually high PM 10 

# 24-hr averages, demonstrating the uniqueness of the dust storm

events during 2011 relative to previous years.



# 4. 2 Summary

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

is clear that the PM 10 

# levels on September 2, 2011, were outside of normal historical

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

scale.

Figure 4-1. 24-hr average PM 10 

## concentrations at the Central Phoenix monitor

(2007-2011). The 24-hr average PM 10 

## concentration on September 2, 2011, is

highlighted in red. The period of July to September 2011 is shown by the vertical box.

1

## Exceptional Event, Phoenix, September 2, 2011 Not Re asonably Controllable or Preventable



## 1 

# 5. Not Reasonably Controllable or Preventable

5.1 B ackground

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 (AgBMP)

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 High Risk for the Maricopa County Dust Control Forecast, (2) ADEQ forecasters issue a

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

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

together so that resources can be best used 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 approved into the Arizona

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

§49-457 1



# .



# 5.1 .1 Control Measures

Maricopa County regulations of PM 10 

# emissions are listed in Table 5-1

.

1 

## Updates to the AgBMP program in December, 2011, cl arified BMPs for crops and added BMPs for animal

operations. Effective 12/29/2011, R18- 2-611 was renumbered to R18-2-610.01 Agricultural PM10 General Permit

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

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

## Exceptional Event, Phoenix, September 2, 2011 Not Reasonably Controllable or Preventable



## 2 Table 5-1. Rules and ordinances regulating particulate matter 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 2, 2011 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 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 2, 2011 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 department’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

(MAG) 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 2, 2011 Not Reasonably Controllable or Preventable



## 5 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: routine

proactive inspections, as well as surveillance inspections, conducted both during and after

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

increase 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 also 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 for Maricopa County, MCAQD conducts additional

increased surveillance before, during, and after the forecast 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 received violations within two business days,

and an internal MCAQD debriefing of event activities.

During 2011, a total of 14 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 2, 2011 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.

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

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

MCAQD air monitoring sites that include real-time data. The ADEQ AgBMP 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 forecasted high

wind alert days. Should the PM 10 

# readings at a MCAQD air monitoring site show notable

increase, the ADEQ AgBMP inspector is dispatched to contact the owners and operators of

agricultural fields in the area to discern if their activities are causing negative impacts. The

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



# 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 Phoenix area around the time of the September 2, 2011, PM 10 

# exceedances. An evaluation

of all inspection reports, air quality complaints, compliance reports, and other documentation do

not indicate any evidence of unusual anthropogenic-based PM 10 

# emissions. During the time

period of August 30 through September 5, 2011, MCAQD inspectors conducted a total of 112

inspections of permitted facilities, of which 89 were at fugitive dust sources. Additionally,

MCAQD conducted 89 inspections on vacant lots and unpaved parking lots during this period.

During this seven-day period, nine violations were issued countywide for PM 10 

# and

non-PM 10 

# related violations. One violation was for PM 10 

# emissions within a four-mile radius of

an exceeding monitor.

On September 1, 2011, a violation was issued to a permitted construction site within four

miles of the Central Phoenix monitor. The violation was issued during a complaint inspection.

The site was issued a violation for failing to maintain complete dust control records. The site

only kept records of the amount of water applied for dust control, but failed to maintain records

of subcontractor registration or maintenance of the trackout control device. The violation was

corrected on subsequent inspections.

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

the seven-day period from August 30 thr ough September 2, 2011, MCAQD received 23

complaints, of which 17 were related to windblown dust. 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 only one emission violation, as discussed in the previous

paragraph, of local, state, or federal PM 10 

# regulations within a four-mile radius of the exceeding

monitors.

## Exceptional Event, Phoenix, September 2, 2011 Not Reasonably Controllable or Preventable



## 7 

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

ADEQ’s Agricultural Best Management Practice Pr ogram (Ag BMP) inspector also monitors the

ADEQ Five-Day Dust Control Forecast and the MCAQD air monitoring sites that include realtime data. The ADEQ Ag BMP inspector uses specific knowledge of seasonal activities and

associations with the local growers and dairyme n 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 activities are causing negative impacts. The Ag BMP inspector is prepared to

respond to most agriculture complaints within 24 hours.

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

evidence to suggest that agricultural activities produced unusual PM 10 

# emissions. On

September 1, 2011, the ADEQ AgBMP inspector received one complaint and made immediate

contact with the operation. The subject agriculture field was located in Surprise and was being

tilled to prepare the field to plant vegetables. Surprise is located in northwestern Maricopa

County, near the Dysart and Zuni Hills AQS monitors. Since both the Dysart and Zuni Hills AQS

monitors were not in exceedance on September 2, 2011, this one particular incident is highly

unlikely to have caused of the widespread regional dust.



# 5 .2 Forecasts and Warnings

Dust forecasts were released prior to the event by ADEQ (Appendix D). For September

2, 2011, the Maricopa County Dust Control Forecast indicated a moderate risk level for

unhealthy PM 10 

# . The Dust Control Forecast also indicated a potential for dense blowing dust

throughout the area generated by outflow from thunderstorms.



# 5 .3 Wind Observations

Sustained wind speeds of over 20 mph with gusts over 30 were reported at monitors

across the Phoenix area, and sustained winds as high as 28 mph at Sky Harbor and 31 mph at

Mesa Gateway with gusts as high as 35 mph were reported as the outflow boundary moved

through (Figure 3-3, Table 3-1 and Appendix A).



# 5.4 Summary

The thunderstorm outflow event of September 2, 2011, produced gusty 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 of Pima, Pinal, and southern Maricopa Counties. 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-approved control measures on significant

anthropogenic sources were in place and enforced during the events, and proactive 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

## Exceptional Event, Phoenix, September 2, 2011 Not Reasonably Controllable or Preventable



## 8 

# 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 thunderstorms and thunderstorm outflows

brought high concentrations of PM 10 

# into, and also overwhelmed controls within, the Phoenix

PM 10 

# nonattainment area. Widespread thunderstorm outflows with sustained winds in excess of

20 mph with gusts over 30 mph were enough to overwhelm available efforts to limit PM 10 

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

thunderstorm outflow winds that transported PM 10 

# emissions into and across the Phoenix area,

with a majority of the PM 10 

# emissions recorded by Phoenix area monitors coming from sources

outside of the Phoenix PM 10 

# nonattainment area, provides strong evidence that the

exceedances of September 2, 2011, recorded within the Phoenix PM 10 

# nonattainment area

were not reasonably controllable or preventa ble.

## Exceptional Event, Phoenix, September 2, 2011 Bu t-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 satisfies that “[t]here would have been no exceedance or violation but for the

event.” The prior sections of this submittal hav e provided detailed information that in regard to

the PM 10 

# exceedances in the Phoenix PM 10 

# nonattainment area on September 2, 2011,

 T he exceedances were not reasonably controllable or preventable, and

 T here was a clear causal relationship between PM 10 

# transported from thunderstorm

outflow originating in desert areas outside the Phoenix metropolitan area and the

measured PM 10 

# exceedances.

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

emissions generated by thunderstorm outflow and the associated transport of PM 10 

# , there would

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



# .

As shown in Section 3, radar velocity data and time-series plots of PM 10 

# and wind

speeds establish a clear causal relationship between the arrival of dust-laden thunderstorm

outflow and elevated PM 10 

# concentrations at monitors in the Phoenix area. Multiple

independent measurements of wind speed, wind direction, and visibility all show that

thunderstorm outflow was the mechanism for transport of PM 10 

# into the Phoenix PM 10 

# nonattainment area. In addition, PM 10 

# concentrations were well below the NAAQS on days

immediately before and after the windblown dust event. The source regions for the

thunderstorm outflow and PM 10 

# are clearly identified as desert areas south of Phoenix. The

weight of evidence presented in this submitta l provides no alternative that could tie the

exceedances of September 2, 2011, to any causal source except PM 10 

# transported by

thunderstorm outflow, confirming that there would have been no exceedances but for the

presence of these uncontrollable natural events.

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

implemented on a continual basis. Local regulatory agencies, industry, and the general public

were alerted to the possibility of dust storms due to thunderstorm activity via daily forecasts and

media reports.



# 6. 2 Summary

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

the exceedances of September 2, 2011, to any causal source except PM 10 

# transported by

thunderstorm outflow, confirming that there would have been no exceedances but for the

presence of these uncontrollable natural events.

## Exceptional Event, Phoenix, September 2, 2011 Co nclusions



## 1 

# 7. Conclusions

The PM 10 

# exceedances that occurred on September 2, 2011, 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:

1. The event satisfies the criteria set forth in 40 CFR 501 (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.



# 7 .1 Affects Air Quality

As stated in the preamble to the Exceptional Events Rule, the event in question is

considered to have affected air quality if it can be shown that there is a clear causal relationship

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 

# exceedances discussed in this report were caused by naturally occurring 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 

# exceedances on

September 2, 2011, were not reasonably controllable or preventable.



# 7.3 Natural Event

As discussed above, the PM 10 

# exceedances on September 2, 2011, were shown to be

caused by transport of PM 10 

# into the Phoenix area from thunderstorm outflow. The event

therefore qualifies as a natural event.

## Exceptional Event, Phoenix, September 2, 2011 Conclusions



## 2 

# 7.4 Clear Causal Relationship

The following points demonstrate that the high PM 10 

# concentrations were caused by

windblown dust:

 Time-seri es of PM 10 

# concentrations show that the timing of high PM 10 

# at Phoenix-area

monitors was consistent with gusty winds and low visibilities (Section 3).

 High PM 1 0 

# concentrations and gusty winds were reported throughout the Phoenix

metropolitan area, illustrating the widespread, regional, and uncontrollable nature of this

event (Section 3).

 PM 10 

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

the windblown dust event (Section3).

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

particulate suspension by high winds (Section 3).

 Visibility camera imagery after sunrise on September 2, 2011, indicated hazy conditions

in the Phoenix area, likely attributable to suspended dust from the outflow boundary that

moved through earlier that morning.



# 7 .5 Historical Norm

The 24-hr average PM 10 

# values measured at the exceedance monitors were historically

unusually high 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

exceedances of the federal 24-hr PM 10 

# standard on September 2, 2011, in the Phoenix PM 10 

# nonattainment area would not have occurred but for the thunderstorm-driven high winds and

transport of dust from areas largely outside the Phoenix PM 10 

# nonattainment area.

## Exceptional Event, Phoenix, S eptember 2, 2011 Appendix A



# A ppendix A:

Air Quality and Meteorological Data

This section contains time-series of PM 10 

# concentrations and wind data for Phoenix-area

monitors on September 1-2, 2011. The data show a region-wide increase in wind gusts

coincident with the arrival of dust and high PM 10



# .

Figure A-1. Hourly PM 10 

## concentrations and wind speeds at the Buckeye monitor on

September 1-2, 2011. PM 10 

## concentrations sharply increased and gusty winds were

reported at 0200 LST on September 2, 2011, indicating the arrival of windblown dust.

1

## Exceptional Event, Phoenix, S eptember 2, 2011 Appendix A



## 2 Figure A-2. Hourly PM 10 

## concentrations and wind speeds at the Central Phoenix

monitor on September 1-2, 2011. PM 10 

## concentrations and wind increased sharply at

0200 LST on September 2, 2011, indicating the arrival of windblown dust. Note that wi

speed and gust data were not available between 700 and 1000 LST on September 1,

2011 at the Central Phoenix m nd

onitor.

## Exceptional Event, Phoenix, S eptember 2, 2011 Appendix A



## Figure A-3. Hou rly PM 10 

## concentrations and wind speeds at the Durango Complex

monitor on September 1-2, 2011. PM 10 

## concentrations increased sharply at 0200 LST on

September 2, 2011, indicating the arrival of windblown dust.

Figure A-4. Hourly PM 10 

## concentrations and wind speeds at the Greenwood monitor on

September 1-2, 2011. PM 10 

## concentrations sharply increased at 0200 LST on

September 2, 2011, coincident with gusty winds , indicating the arrival of windblown dust.

Note that PM 10 

## concentration was not available at 1000 LST on September 1, 2011 at the

Greenwood monitor.

3

## Exceptional Event, Phoenix, S eptember 2, 2011 Appendix A



## Figure A-5. Hourly PM 10 

## concentrations and wind speeds at the JLG Supersite monitor

on September 1-2, 2011. PM 10 

## concentrations sharply increased at 0200 LST on

September 2, 2011, indicating the arrival of windblown dust.

Figure A-6. Hourly PM 10 

## concentrations and wind speeds at the North Phoenix monitor

on September 1-2, 2011. PM 10 

## concentrations sharply increased at 0300 LST on

September 2, 2011, coincident with gusty winds , indicating the arrival of windblown dust.

Note that PM 10 

## concentrations were not available at 200 LST on September 2, 2011 at

the North Phoenix monitor.

4

## Exceptional Event, Phoenix, S eptember 2, 2011 Appendix A



## Figure A-7. Hourly PM 10 

## concentrations and wind speeds at the South Phoenix monitor

on September 1-2, 2011. PM 10 

## concentrations sharply increased at 0200 LST on

September 2, 2011, coincident with gusty winds , indicating the arrival of windblown dust.

Figure A-8. Hourly PM 10 

## concentrations and wind speeds at the West 43 rd 

## Avenue

monitor on September 1-2, 2011. PM 10 

## concentrations sharply increased at 0200 LST on

September 2, 2011, coincident with gusty winds , indicating the arrival of windblown dust.

5

## Exceptional Event, Phoenix, S eptember 2, 2011 Appendix A



## Figure A-9. Hou rly wind speeds at the Maricopa monitor on September 1-2, 2011. Wind

speeds and gusts sharply increased at 0200 LST on September 2, 2011.

Figure A-10. Hourly wind speeds at the Paloma monitor on September 1-2, 2011. Wind

speeds and gusts sharply increased at 0200 LST on September 2, 2011.

6

## Exceptional Event, Phoenix, S eptember 2, 2011 Appendix A



## 7 Figure A-11. Hourly wind speeds at the Queen Cr eek monitor on September 1-2, 2011.

Wind speeds and gusts sharply increased at 0200 LST on September 2, 2011.

## 8U.S. Department of CommerceNational Oceanic &Atmospheric AdministrationQUALITY CONTROLLED LOCAL CLIMATOLOGICAL DATAHOURLY OBSERVATIONS TABLEPHOENIX SKY HARBOR INTL AIRPORT (23183)PHOENIX, AZ (09/2011)National Climatic Data CenterFederal Building151 Patton AvenueAsheville, North Carolina 28801Elevation:1107 ft. above sea levelLatitude:33.427Longitude:-112.003Data Version:VER3DryBulbTempWetBulbTempDewPointTempDateTime(LST)StationTypeSkyConditionsVisibility(SM)WeatherType(F)(C)(F)(C)(F)(C)RelHumd%WindSpeed(MPH)WindDirWindGusts(MPH)StationPressure(in. hg)PressTendNet3-hrChg(mb)SeaLevelPressure(in. hg)ReportTypePrecip.Total(in)Altimeter(in. hg)12345678910111213141516171819202122230202020202020202020202020202020202020202020202020202020202020202005101490151015401560209023902470251025503150351045105510651075108510951105111511251135114511551165117511851195120512151225123511111111111111111111111111111111111111111111111111111111111111111FEW140 BKN190FEW120 BKN160SCT020 BKN140SCT020 BKN140VV006VV008BKN010BKN013 BKN110BKN013 BKN110BKN019 BKN110 BKN160SCT019 BKN110 BKN160FEW110 BKN160 BKN200FEW110 SCT160 BKN200FEW110 BKN160 BKN200SCT130 BKN160 BKN250FEW110 BKN130 BKN170FEW110 BKN140 BKN170FEW110 SCT140 BKN180FEW110 SCT140 BKN180FEW140 SCT180 BKN210FEW140 SCT190 BKN220FEW140 SCT190 BKN220FEW140 SCT190 BKN220FEW140 SCT190 SCT220FEW140 SCT190 SCT220FEW140 SCT190 SCT250FEW140 SCT250FEW140 SCT250FEW140 SCT250CLRCLRFEW17010.002.501.500.750.751.001.252.002.503.003.005.0010.0010.009.009.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.00HZBLDUBLDUBLDU-RA BLDUBLDUBLDUBLDUBLDUBLDUDU-RA-RA9597959393919191929191919088878889909193979799101101101101989795939335.036.035.034.034.033.033.033.033.333.033.032.832.231.130.631.131.732.232.833.936.136.137.238.338.338.338.336.736.135.033.933.9646668707173717171707170737474737374737372737170706969696867666517.518.820.020.921.522.621.721.721.621.221.721.222.823.423.322.822.923.122.922.622.422.921.921.221.020.520.320.719.919.519.018.540455257596461616059615965686866666665636062575352504953505049474.47.011.114.015.018.016.016.015.615.016.015.018.320.020.018.918.918.918.317.215.616.713.911.711.110.09.411.710.010.09.48.31517233032413737343437344452534847454237293125201918172220222221626221618281714151311097587553103814141311710656230170180160170180180210220210220000360340VR320300300290260280290330320290300280250260250250280343434343430181828.5428.6028.6028.6128.6128.6028.6228.6228.6228.6228.6328.6528.6528.6628.6628.6628.6828.6928.6928.6628.6528.6228.6028.5728.5528.5428.5328.5428.5528.5628.5728.573111865102401600500702102400300829.64M29.70MMMMM29.72MM29.7529.7529.7729.7629.7729.7829.7929.7929.7729.7529.7329.7029.6729.6529.6429.6329.6529.6629.6629.6729.67AASPAASPSPSPSPSPAASPSPAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAATTT29.7129.7729.7729.7829.7829.7729.7929.7929.7929.7929.8029.8229.8229.8329.8329.8329.8529.8629.8629.8429.8229.7929.7729.7429.7229.7129.7029.7129.7229.7329.7429.74Figure A-12.Quality-controlled local climatological data hourly observations table for PhoenixSky Harbor International Airport, Phoenix,Arizona (09/02/2011). Note in the Weather Type column that BLDU (blowing dust) was reported for several hours. For a more detailedexplanation of the weather codes shown in the table above, please seehttp://www.nws.noaa.gov/oso/oso1/oso12/document/guide.shtml. Datadynamically generated viahttp://cdo.ncdc.noaa.gov/qclcd/QCLCD.

## 9U.S. Department of CommerceNational Oceanic & Atmospheric AdministrationQUALITY CONTROLLED LOCALCLIMATOLOGICAL DATA(final)HOURLY OBSERVATIONS TABLEWILLIAMS GATEWAY AIRPORT (23104)PHOENIX, AZ(09/2011)National Climatic Data CenterFederal Building151 Patton AvenueAsheville, North Carolina 28801Elevation: 1382 ft. above sea levelLatitude: 33.3Longitude: -111.666Data Version: VER2DryBulbTempWetBulbTempDewPointTempDateTime(LST)StationTypeSkyConditionsVisibility(SM)WeatherType(F)(C)(F)(C)(F)(C)RelHumd%WindSpeed(MPH)WindDirWindGusts(MPH)StationPressure(in. hg)PressTendNet3-hrChg(mb)SeaLevelPressure(in. hg)ReportTypePrecip.Total(in)Altimeter(in. hg)123456789101112131415161718192021222302020202020202020202020202020202020202020202020202020202020202020202020015003500550115013501550215023502550315033503550415043504550515053505490649074708470954104811481248134714471550164717471847195019552015203500000000000000000000000000000000000CLRCLRCLRBKN002OVC002MMSCT001CLRCLRCLRCLRCLRCLRCLRCLRCLRSCT120 BKN150 OVC200SCT120 BKN150 OVC200SCT120 BKN150 OVC200FEW120 BKN150 BKN200FEW120 BKN150 BKN200SCT120 BKN200SCT120 BKN200FEW150 SCT200FEW150 SCT200FEW150 SCT200FEW150 SCT200FEW150 SCT200FEW150FEW150FEWCLRCLRCLR10.0010.0010.001.002.002.002.507.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.003.005.005.0010.0010.0010.0010.0015.00s15.00s15.00s15.00s15.0015.0010.0010.0010.00HZHZHZHZHZHZHZHZHZHZHZHZHZHZHZ97979797939393939188888888888888888890919193979910210210210610610210210099979736.036.036.036.034.034.034.034.033.031.031.031.031.031.031.031.031.031.032.033.033.034.036.037.039.039.039.041.041.039.039.038.037.036.036.065646470727373737272737272727272717272717374747372737172706868M67666918.417.618.021.022.022.622.622.622.322.122.822.122.122.122.122.121.822.122.121.722.623.523.522.922.322.821.622.120.820.219.8M19.319.020.343394155616363636364666464646464636463616466646157595454484846484646526.04.05.013.016.017.017.017.017.018.019.018.018.018.018.018.017.018.017.016.018.019.018.016.014.015.012.012.09.09.08.09.08.08.011.016131424343737373945484545454545434541374141342923242018141615M1617220683120202010810775330037778789913141114113003000120130180200210210170120110120110120100090000000VR350350330270300300290280280290300310300VR000000230372926251717181828.3028.3128.3328.3528.3628.3628.3728.3928.4028.4128.4128.4128.4128.4128.4128.4128.4128.4028.4028.4228.4328.4428.4328.4228.3928.3728.3428.3228.3028.2928.29M28.3128.3128.31MMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA29.7629.7729.7929.8129.8229.8229.8329.8529.8629.8729.8729.8729.8729.8729.8729.8729.8729.8629.8629.8829.8929.9029.8929.8829.8529.8329.8029.7829.7629.7529.7529.7629.7729.7729.77

## 1002020202020202020202022047205521152135215522152235225523152335235500000000000BKNCLRCLRCLRCLRCLRCLRCLRCLRCLRCLR20.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.00979797909090908888888836.036.036.032.032.032.032.031.031.031.031.0M69696666666667676666M20.320.318.619.118.618.619.319.318.818.8525252505250505454525211.011.011.010.011.010.010.012.012.011.011.0M2222252725253131292935030578763VR250000110000110120130130110110M28.3228.3228.3228.3228.3228.3328.3428.3328.3328.33MMMMMMMMMMMAAAAAAAAAAAAAAAAAAAAAA29.7729.7829.7829.7829.7829.7829.7929.8029.7929.7929.79Figure A-13.Quality-controlled local climatological data hourly observations table for WilliamsGateway Airport, Phoenix, Arizona (09/02/2011).Note in the Weather Type column that HZ (haze) wasreported for several hours. Dynamically generated viahttp://cdo.ncdc.noaa.gov/qclcd/QCLC.

## 11U.S. Department of CommerceNational Oceanic & Atmospheric AdministrationQUALITY CONTROLLED LOCALCLIMATOLOGICAL DATA (final)HOURLY OBSERVATIONS TABLELUKE AFB AIRPORT (23111)GLENDALE, AZ (09/2011)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)12345678910111213141516171819202122230202020202020202020202020202020202020202020202020202020200550155022902460249025503060355045505550655075508550955105511551255135514551555165517551855195520552155225523550000000000000000000000000000FEW140 BKN210FEW140 BKN170FEW010 SCT140BKN140SCT140SCT140FEW140SCT180 BKN200BKN160CLRFEW190CLRCLRFEW180FEW180FEW130 SCT200FEW160FEW170FEW190CLRCLRCLRCLRCLRCLRCLRCLRCLR10.0010.006.008.008.009.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.00-RA-DZ-DZ9396939090898888868687878890919292939698102103101959491898733.835.734.032.032.031.431.030.930.130.230.430.531.332.032.833.133.233.835.436.639.039.738.235.134.533.031.430.46466727273757575757575757574737575747474716767696766666517.918.822.022.222.523.624.123.723.823.823.623.923.823.422.924.023.723.223.423.121.619.619.520.719.118.818.718.4444661636468706970706970696765686765646254444555495051516.67.816.017.018.020.021.020.821.221.020.620.920.319.618.419.819.318.517.816.512.06.87.312.89.710.210.610.71818344142505553595955575347424544403531201315262225272962028181814172295030038735066635766180250240170170190190220240200000360000000VR190200VR21000032030023023023017021020034232828.5828.6028.6228.6528.6628.6628.6628.6628.6728.6828.6928.7028.7128.7128.7128.7028.6828.6628.6328.6028.5828.5628.5628.5728.5828.5828.5928.603121865201302500900501902600300829.6229.6329.6629.7029.7029.7029.7129.7029.7229.7329.7429.7529.7729.7729.7729.7629.7429.7129.6929.6529.6329.6229.6129.6329.6429.6529.6629.66AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAATTTTTT29.7329.7529.7729.8029.8129.8129.8129.8129.8229.8329.8429.8529.8629.8629.8629.8529.8329.8129.7829.7529.7329.7129.7129.7229.7329.7329.7429.75Figure A-14.Quality-controlled local climatological data hourly observations table for Luke Air Force Base, Glendale, Arizona (09/02/2011).Dynamically generated viahttp://cdo.ncdc.noaa.gov/qclcd/QCLCD.

## 12U.S. Department of CommerceNational Oceanic & Atmospheric AdministrationQUALITY CONTROLLED LOCALCLIMATOLOGICAL DATA (final)HOURLY OBSERVATIONS TABLEPHOENIX DEER VALLEY ARPT (03184)PHOENIX, AZ (09/2011)National Climatic Data CenterFederal Building151 Patton AvenueAsheville, North Carolina 28801Elevation: 1455 ft. above sea levelLatitude: 33.688Longitude: -112.081Data 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)1234567891011121314151617181920212223020202020202020202020202020202020202020202020202020202020202005301530234024002510253025603070351035304530553065307530853095310531153125313531453155316531753185319532053215322532353121212121212121212121212121212121212121212121212121212121212CLRCLRBKN013VV012BKN013BKN013BKN013BKN017BKN031BKN033OVC032FEW032FEW028CLRSCT100 SCT120FEW050FEW110CLRCLRCLRCLRCLRCLRCLRCLRCLRCLRCLRCLRCLR10.0010.002.001.001.502.004.005.009.009.009.009.008.008.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.00HZHZ-RA-RA-RAHZ919293939192919086868584858587878889909295979910099969289868532.833.334.034.033.033.333.032.030.030.029.428.929.429.430.630.631.131.732.233.335.036.137.237.837.235.633.331.730.029.463626667656564677171727273727271717171707171696664646362626217.316.718.719.118.318.317.919.621.821.822.322.122.622.322.021.621.821.721.521.321.721.820.619.018.017.617.016.916.516.84339485048474654646466666766646363626159595852443940414344466.13.99.010.09.08.38.012.018.017.818.918.919.418.917.817.217.216.716.115.015.014.411.16.73.94.45.06.16.77.8191621232321212948485355555346454341383330272115121417202326081316211615141010106079653039911116300500002201701802302302302302402402402500003603303002602500002902702602702702802200000001100002526262628.1828.2028.2428.2528.2628.2628.2628.2728.2928.2928.3028.3028.3028.3128.3128.3228.3228.3128.2928.2628.2428.2128.2028.1728.1728.1828.2028.2028.2028.213113875300903100400402002400300829.6529.67MMM29.73MMM29.7629.7729.7729.7829.7829.7829.7929.8029.7829.7629.7329.7129.6829.6629.6529.6429.6529.6629.6729.6829.69AAAASPSPSPAASPSPSPAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAT29.7429.7629.8029.8129.8229.8229.8229.8329.8529.8529.8629.8629.8629.8729.8729.8829.8829.8729.8529.8229.8029.7729.7529.7329.7329.7429.7529.7529.7629.77Figure A-15.Quality-controlled local climatological data hourly observations table for Phoenix Deer Valley Airport, Phoenix, Arizona(09/02/2011). Note in the Weather Type column that HZ (haze) was reported forseveral hours. Dynamically generated viahttp://cdo.ncdc.noaa.gov/qclcd/QCLCD.

## Exceptional Event, Phoenix, S eptember 2, 2011 Appendix B



# Appendix B: Media Coverage, Videos, and Images

ADEQ visibility cameras in the Phoenix area:

South Mountain: www.phoenixvis.net/videos/mpeg4/SOMT_09022011.mp4

Estrella Mountains: www.phoenixvis.net/videos/mpeg4/ESMO_09022011.mp4

Camelback Mountains: www.phoenixvis.net/videos/mpeg4/CAME_09022011.mp4

Superstition Mountains: www.phoenixvis.net/videos/mpeg4/SUPM_09022011.mp4

Other media sources:

http://www.youtube.com/watch?v=0ckZh57Lsx4

http://www.azfamily.com/younews/129081558.html?img=1&mg=t

Figure B-1. Dust storm in Phoenix at approximat ely 0200 LST on September 2, 2011.

This photo was taken on 20th Street and Indian School Road. Image source:

http://www.azfamily.com/younews/129081558.html?img=1&mg=t

.

1

## Exceptional Event, Phoenix, S eptember 2, 2011 Appendix C



# Appendix C: Historical Fluctuation Time Series Graphs

Figure C-1. 24-hr average PM 10 

## concentrations at the Greenwood monitor (2007–2011).

The 24-hr average PM 10 

## concentration on September 2, 2011, is shown in red and

highlighted by the arrow.

1

## Exceptional Event, Phoenix, S eptember 2, 2011 Appendix C



## Figure C-2. 24-hr average PM 10 

## concentrations at the South Phoenix monitor (2007–

2011). The 24-hr average PM 10 

## concentration on September 2, 2011, is shown in red

and highlighted by the arrow.

Figure C-3. 24-hr average PM 10 

## concentrations at the West Chandler monitor (2007–

2011). The 24-hr average PM 10 

## concentration on September 2, 2011, is shown in red

and highlighted by the arrow.

2

## Exceptional Event, Phoenix, S eptember 2, 2011 Appendix C



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

## concentrations at the Higley monitor (2007–2011). The

24-hr average PM 10 

## concentration on September 2, 2011, is highlighted in red. The

period of July to September 2011, is show n in red and highlighted by the arrow.

Figure C-5. 24-hr average PM 10 

## concentrations at the We st 43rd monitor (2007–2011).

The 24-hr average PM 10 

## concentration on September 2, 2011, is shown in red and

highlighted by the arrow.

3

## Exceptional Event, Phoenix, S eptember 2, 2011 Appendix C



## Figure C-6. 24-hr average PM 10 

## concentrations at the Bu ckeye monitor (2007–2011).

The 24-hr average PM 10 

## concentration on September 2, 2011, is shown in red and

highlighted by the arrow.

Figure C-7. 24-hr average PM 10 

## concentrations at the Durango monitor (2007–2011).

The 24-hr average PM 10 

## concentration on September 2, 2011, is shown in red and

highlighted by the arrow.

4

## Exceptional Event, Phoenix, S eptember 2, 2011 Appendix C



## Figure C-8. 24-hr average PM 10 

## concentrations at the JLG Supersite monitor (2007–

2011). The 24-hr average PM 10 

## concentration on September 2, 2011, is shown in red

and highlighted by the arrow.

Figure C-9. 24-hr average PM 10 

## concentrations at the North Phoenix monitor (2007–

2011). The 24-hr average PM 10 

## concentration on September 2, 2011, is shown in red

and highlighted by the arrow.

5

## Exceptional Event, Phoenix, S eptember 2, 2011 Appendix C



## Figure C-10. 24-hr average PM 10 

## concentrations at the Fort McDowell/Yuma Frank

monitor (2007–2011). The 24-hr average PM 10 

## concentration on September 2, 2011, is

shown in red and highlighted by the arrow.

F igure C-11. 24-hr average PM 10 

## concentrations at the Apache Junction monitor (2007–

2011). The 24-hr average PM 10 

## concentration on September 2, 2011, is shown in red

and highlighted by the arrow.

6

## Exceptional Event, Phoenix, S eptember 2, 2011 Appendix D



# Appendix D:

ADEQ and NWS Forecast Products

MARICOPA COUNTY DUST CONTROL FORECAST

ISSUED THURSDAY, SEPTEMBER 01, 2011

Five-day weather outlook:

DURING ACTIVE SUMMER MONSOON EPISODES STRONG GUSTY WINDS AND DENSE BLOWING DUST ARE

POSSIBLE EVEN FROM DISTANT THUNDERSTORMS

Although the prospects for thunderstorms and si gnificant rainfall in the Valley are remo te, an increase in summer monsoon moist ure

and thunderstorm activity east and southeast of the metro area th e next few days will mean a higher risk for unhealthy levels of PM10 due to dense blowing dust generated by out flow boundaries. Otherwise, low-level grad ient winds and upslope flow will yield

breezy to gusty conditions at times each afternoon thru Sunday with a light eas terly wind regime possible by Monday.



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

WINDS STAGNATION UNHEALTHY PM-10

RISK LEVEL



## D-1 Day 1: Fri 09/02/2011 Southwest to westerly

10-20 mph during the

afternoon except strong

and gusty due to

outflow from

thunderstorms. No significant

+ stagnation expected. = MODERATE

Day 2: Sat 09/03/2011 Southwest to westerly

10-20 mph during the

afternoon except strong

and gusty due to

outflow from

thunderstorms. No significant

+ stagnation expected. = MODERATE

Day 3: Sun 09/04/2011 Southwest to westerly

10-20 mph during the

afternoon except strong

and gusty due to

outflow from

thunderstorms. No significant

+ stagnation expected. = MODERATE

EXTENDED OUTLOOK

Day 4: Mon 09/05/2011 Easterly 5-10 mph

except strong and gusty

due to outflow from

thunderstorms. No significant

+ stagnation expected. = MODERATE

Day 5: Tue 09/06/2011 Easterly 5-10 mph

except strong and gusty

due to outflow from

thunderstorms. No significant

+ stagnation expected. = MODERATE

## Exceptional Event, Phoenix, S eptember 2, 2011 Appendix D



## D-2 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/ozone/ensemble.pdf

. CKR 04/28/2011

## Exceptional Event, Phoenix, S eptember 2, 2011 Appendix D



## D-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

NEW!!! CLICK HERE FOR UPDATED OZONE SEASON STATS NEW!!!



# AIR QUALITY FORECAST FOR FRIDAY, SEPTEMBER 02, 2011

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

for areas within and bordering Maricopa County in Arizona



## FORECAST

DATE

NOTICES

(*SEE BELOW

FOR DETAILS)

AIR POLLUTANT 

# YESTERDAY

WED 08/31/2011

DUST

NWS EXCESSIVE

HEAT WARNING

Highest AQI Reading/Site

(Preliminary data only) 

# TODAY

THU 09/01/2011

OZONE HEALTH

WATCH

DUST

NWS EXCESSIVE

HEAT WARNING 

# TOMORROW

FRI 09/02/2011

OZONE HEALTH

WATCH

DUST

NWS EXCESSIVE

HEAT WARNING 

# EXTENDED

SAT 09/03/2011

OZONE HEALTH

WATCH

POSSIBLE

DUST



# O3* 93

QUEEN VALLEY 

## 97

MODERATE 

## 93

MODERATE 

## 90

MODERATE



# CO* 07

GREENWOOD 

## 06

GOOD 

## 05

GOOD 

## 06

GOOD



# PM-10* 58

WEST FORTY THIRD 

## 75

MODERATE 

## 75

MODERATE 

## 75

MODERATE



# PM-2.5* 41

PHOENIX SUPERSITE 

## 50

GOOD 

## 49

GOOD 

## 47

GOOD

* O3 = Ozone CO = Carbon Monoxide PM-10 = Particles 10 micr ons & 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.

## Exceptional Event, Phoenix, S eptember 2, 2011 Appendix D



## D-4 “ PM-10 or PM-2.5 Health Watch ” means that the highest concentration of PM-10 or PM-2.5 may approach the federal health standard.

“ High Pollution Advisory ” means that the highest concentration of OZONE, PM-10, or PM-2.5 may exceed the federal health standard.

“ DUST ” means that short periods of high PM-10 concentrati ons caused by outflow from thunderstorms are possible.

## Exceptional Event, Phoenix, S eptember 2, 2011 Appendix D

Health message for Thursday September 01: Unusually sensitive people should consider

reducing prolonged or heavy exertion outdoors.

Health message for Friday September 02: Unusually sensitive peop le should consider

reducing prolonged or heavy exertion outdoors.



## Synopsis and Discussion

OZONE: AN OZONE HEALTH WATCH HAS BEEN ISSUED FOR TODAY AND FRIDAY SEPT 02

It appears that last evening’s thunderstorm outflow boundary has significantly altered the local ozone chemistry due to

a suspected increase in ozone precursors. Around 9:00 p. m. Wednesday hourly ozone time series’ from nearly all

Valley ozone monitoring sites showed a subtle increase in ozone concentrations following east to southeasterly wind

gusts of up to 25 mph. Ozone readings at some metro lo cations subsequently remained elevated thru the overnight

period and hourly concentrations Valley-wide were ramping up rapidly as of this writing. As of 10:00 a.m. hourly

concentrations were between 20 and 30 parts per billion higher than those of 24 hours ago at sites such South Phoenix,

West Phoenix, and South Scottsdale. Since a westerly wind regime remains in place, highest 8-hour average ozone

levels are still expected to occur over the eastern portion of the metro area but readings may now approach unhealthy

concentrations over some central city locations as well. As a result, an Ozone Health Watch has been issued for the

remainder of today. A si milar situation looks possible for Friday so the Watch will c ontinue in effect.

PARTICLES: A localized blowing dust event occurred Wednesday evening with the highest PM-10 concentration of

428.1ug/m3 measured at the Higley monitoring site at 8:00 p.m. Visibilit ies as low as five miles and wind gusts up to 26 mph were

recorded. 

## Although the prospects for thunderstorms and significant rainfall in the Valley are remote, an increase in

summer monsoon moisture and thunderstorm activity east and southeast of the metr o area the next few days will mean

a higher risk for unhealthy levels of PM-10 due to dense blowing dust generated by out flow boundaries. Otherwise,

low-level gradient winds and upslope flow will yield breezy to gusty conditions at times each afternoon thru Saturday.

MONITORING SITE MAPS: STATIC MAP

- http://www.azdeq.gov/environ/air/monitoring/images/map.jpg



## D-5 IN TERACTIVE MAPS - http://aqwww.maricopa.gov/AirM onit oring/SitePollutionMap.aspx

http://www.airnow.gov /



# POLLUTION MONITOR READINGS FOR WEDNESDAY, AUGUST 31, 2011



# O3 (OZONE)

Info on current 8-hour ozone standard: http://www.epa.gov/air/ozonepoll ution/pdfs/2008_03_aqi_changes.pdf

For archived AQI maps go to: http://www.airnow.gov/index.cfm?action=airnow.maps

SITE NAME MAX 8-HR VALUE (PPB) MAX AQI AQI COLOR CODE

Alamo Lake (La Paz County) 55 47

Apache Junction (Pinal County) 63 61

Blue Point 62 58

Buckeye 42 36

Casa Grande (Pinal County) 50 42

Cave Creek 57 48

Central Phoenix 54 46

Dysart 47 40

Falcon Field 61 54

Fountain Hills 63 61

Glendale 52 44

Humboldt Mountain 57 48

North Phoenix 58 49

Phoenix Supersite 57 48

Pinal Air Park (Pinal County) 52 44

Pinnacle Peak 55 47

Queen Valley (Pinal County) 73 93

Rio Verde 62 58

South Phoenix 53 45

South Scottsdale 57 48

Tempe 50 42

Tonto Nat’l Mon. (Gila County) 63 61

West Chandler 63 61

West Phoenix 55 47

Yuma (Yuma County) 47 40

## Exceptional Event, Phoenix, S eptember 2, 2011 Appendix D



## D-6 

# CO (CARBON MONOXIDE)

SITE NAME MAX 8-HR VALUE (PPM) MAX AQI AQI COLOR CODE

Central Phoenix 0.5 06

Greenwood 0.6 07

Phoenix Supersite NOT AVBL NOT AVBL NOT AVBL

West Phoenix 0.4 05



# PM-10 (PARTICLES)

SITE NAME MAX 24-HR VALUE (ug/m3) MAX AQI AQI COLOR CODE

Buckeye 62 54

Central Phoenix 48 44

Combs School(Pinal County 77 59

Durango 63 55

Dysart 38 35

Glendale 41 38

Greenwood 42 39

Higley 62 54

Maricopa (Pinal County) 79 63

Phoenix Supersite 38 35

South Phoenix 62 54

West Chandler 47 44

West Forty Third 69 58

West Phoenix 52 48

Zuni Hills 38 35



# PM-2.5 (PARTICLES)

(Some data derived from light-scattering equipment)



### For maps go to: http://www.airnow.gov /

SITE NAME MAX 24-HR VALUE (ug/m3) MAX AQI AQI COLOR CODE

Durango 11.4 37

Dysart 8.4 27

Estrella Mountain Park 4.4 14

Glendale 9.5 31

Phoenix Supersite 12.6 41

South Phoenix 8.6 28

Vehicle Emissions Lab 9.1 30

West Phoenix 9.9 32

## Exceptional Event, Phoenix, S eptember 2, 2011 Appendix E



# Appendix E:

Affidavit of Public Notice

1