# State of Arizona Exceptional Event Documentation

for the Event of August 18, 2011,

for the Phoenix PM 10 

# Nonattainment Area

Final Report Prepared for

Arizona Department of Environmental Quality Maricopa County Air Quality Department

Maricopa Association of Governments

January 23, 2013

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

# State of Arizona Exceptional Event Documentation

for the Event of August 18, 2011,

for the Phoenix PM 10 

# Nonattainment Area

Final Report

STI-912090-5545-DR



# 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 image illustrates windblown dust due to thunderstor m outflow moving into Phoenix, AZ at 1810 LST on August 18, 2011. This photo was taken by an ADEQ visibility came ra from North Mountain looking south toward downtown

Phoenix.Exceptional Event, Maricopa County , August 18, 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.

iiiExceptional Event, Maricopa County, August 18, 2011 Table of Contents



# Table of Contents

Section Page

List of Figures ..............................................................................................................................v ii

List of Tables

............................................................................................................................... . i x

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

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

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

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

5.1.3 PM Rule Effectiveness ................................................................................3 10 

### 5.1.4 Compliance and Enforcement Activities.........................................................4

5.1.5 Review of Source-Permitted Inspections and Public Complaints ..................5

5.2 Forecasts and Warnings ............................................................................................6

5.3 Wind Observations.....................................................................................................6

5.4 Summary ....................................................................................................................6

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

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

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

vExceptional Event, Maricopa County, August 18, 2011 Table of Contents



### vi 

### 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: Air Quality and Meteorological Data ...............................................................1

Appendix B: Media Coverage, Videos, and Images ...........................................................6

Video Links ..........................................................................................................................6 Media Article and Image Links ............................................................................................7

Appendix C: Historical Fluctuation Time-Series Graphs ...................................................20

Appendix D: ADEQ and NWS Forecast Products ............................................................22

Appendix E: Affidavit of Public Notice ................................................................................1Exceptional Event, Maricopa County, August 18, 2011 List of Figures



# List of Figures

Figure Page

Figure 2-1. Location of air quality monitors with exceedances of the 24-hr PM NAAQS and represe ntative NWS meteorological monitors............................................................2 10



### Figure 2-2. Location of air quality sites monitoring PM statewide on August 18, 2011............3 10



### Figure 2-3. Drainage System of Ph oenix, Arizona. .....................................................................4

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

Figure 2-5. Cross-section of a thunderstorm creating an outflow boundary and haboob. (Source: Desert Meteorology, Thomas T. Warner, 2004.) ...............................................6

Figure 2-6. Thunderstorms (bright white areas) over central and eastern Arizona produced outflow boundaries that propagated westward and transported dust to the Phoenix area on August 18, 2011...............................................................................7

Figure 3-1. Visible satellite image from 16:30 LST on August 18, 2011 (GOES-West). Bright white areas indicate tall, convective (thunderstorm) clouds. Thunderstorms over central and eastern Arizona generated outflow boundaries that carried dust

westward across the Phoenix area. ..................................................................................1

Figure 3-2. Phoenix-area air quality and meteorological monitors and general wind

direction. Wind and PM data at the monitors are shown in Table 3-1. Gusty

winds associated with th understorm outflow transported dust across the Phoenix area during the late afternoon hours of August 18, 2011..................................................2 10



### Figure 3-3. Radar base velocity data at 18:06 L ST on August 18, 2011, from NWS Phoenix Doppler radar. Green indicates flow toward the radar; dark orange and red indicate flow toward the radar, and yellow indicates little motion toward the radar. Two well-defined outflow boundaries (dashed liens) approached the Phoenix area from the southeast (A) and east (B). These boundaries carried dust northward and westward across the Phoenix metropolitan area. Error! Bookmark not defined.

Figure 3-4. Hourly PM concentrations and wind speeds at the West Chandler monitor on August 1 8 and 19, 2011. PM concentrations and wind speeds sharply

increased at 16:00 LST on August 18, 2011, indicating the arrival of windblown dust. Sustained winds of 20 mph were measured with gusts over 35 mph......................5 10

10



### Figure 3-5 . Hourly PM concentrations and wind speeds at the Buckeye monitor on August 18 a nd 19, 2011. PM concentrations sharply increased with wind gusts over 35 mph at 20:00 LST on August 18, 2011, indicating the arrival of windblown

dust. ..................................................................................................................................5 10

10



### Figure 3-6. Hourly PM concentrations at the Phoenix area PM monitors and visibility

at KPHX . Visibility was significantly reduced at KPHX between 18:00 and 19:00 LST, coincident with the sharp increase in PM concentrations at area PM monitors, indicating the arrival of windblown dust.............................................................6 10 10

10 10



### viiExceptional Event, Maricopa County, August 18, 2011 List of Figures



### viii 

### Figure 4-1. 24-hr average PM concentrations at the Central Phoenix monitor (2007-2011). The 24-hr average PM concentration on August 18, 2011, is highlighted in red............................................................................................................. ..1 10

10



### Figure 5-1. Timeline of Maricopa County fugitive dust rules and ordinances..............................4

Figure C-0-1. 24-hr average PM concentrations at the Buckeye monitor (2007–2011). The 24-hr average PM concentration on August 18, 2011, is highlighted in red..........20 10

10



### Figure C-0-2. 24-hr average PM concentrations at the West Chandler monitor (2007– 2011). The 24-hr average PM concentration on August 18, 2011, is highlighted

in red.

........................................................................................................................ ......21 10

10



### Figure C-0-3. 24-hr average PM concentrations at the South Phoenix monitor (2007– 2011). The 24-hr average PM concentration on August 18, 2011, is highlighted

in red.

........................................................................................................................ ......21 10

10Exceptional Event, Maricopa County, August 18, 2011 List of Tables



# List of Tables

Table Page

Table 2-1. Statewide monitor information and PM measurements on August 18, 2011. 7 10



### Table 3-1. Observed wi nd speeds and wind gusts at Maricopa County monitors and KPHX on August 18, 2011. All monitors reported high PM concentrations from 18:00 to 20:00 LST on August 18, 2011, coincident with high wind speeds and wind gusts. 3 10



### Table 5-1. Rules and o rdinances regulating particulate matter emissions in Maricopa County. 2

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

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

Nonattainment Area. 3 10



### ixExceptional Event, Phoenix, August 18, 2011 Int roduction



### 1 

# 1. Introduction

On August 18, 2011, four 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 these
exceedances were due to naturally occurring windblown dust, were historically unusual, were not reasonably controllable or preventable, and would not have occurred “but-for” the windblown dust and, therefore, are Exceptional Events as defined by the U.S. Environmental Protection Agency’s (EPA) Exceptional Events Rule (EER).



# 1.1 Report Contents

Section 2 of this assessment contains a c onceptual model of the wind-blown dust event that transpired on August 18, 2011, and provides a background narrative of the exceptional event and an overall explanation of how the event affected air quality. Section 2 also provides

evidence that the event was a natural event.

Section 3 of this assessment establishes a clear causal connection between the natural event on August 18, 2011, and the exceedances of the 24-hr PM 10 

### standard at the four monitoring stations. The evidence in this section also confirms that the event in question both affected air quality and was the result of natural events.

Section 4 of this assessment illustrates that the event of August 18, 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 August
18, 2011, was not reasonably controllable or preventable.

Section 6 of this assessment builds upon t he demonstrations made in the previous sections, showing a clear causal connection between the natural event and the exceedances,

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

### standard on August 18, 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 videos, images, and media reports to supplement Section 3. Appendix C contains time-series graphs to supplement Section 4. Appendix D contains air quality forecasts issued by the Arizona Department of Environmental Quality (ADEQ) and weather statements and warnings issued by the National Weather Service. Appendix E contains a copy of the affidavit of pub lic 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 qualityExceptional Event, Phoenix, August 18, 2011 Introduction



### 2 

### monitoring data. This section of the report contains the requirements of the EER and associated 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 August 18, 2011. More information on ADEQ’s forecasting program can be found in Section 5 of this report. The forecast products that were issued pertaining to this 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 (or another agency operating monitors in Arizona) suspects that data may be influenced by an exceptional event, ADEQ (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 (or the other operating agency) also submits data from continuous monitors into AQS after quality assurance
is complete.

If ADEQ (or other operating air quality agencies) have determined that the potential exists that a monitor’s reading(s) have been infl uenced by an exceptional event, a preliminary flag is submitted for those measurement(s) in AQS. The data are not official until they undergo 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 flags on the August 18, 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 EER. The PM 10 

### exceedances that occurred at four monitors on August 18, 2011, in the Phoenix PM 10 

### nonattainment area were included on this list. This assessment report serves as demonstration supporting the flagging of these data.



## 1.2.4 Document That the Public Comment Process Was Followed for Event

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

ADEQ posted this assessment report on the ADEQ webpage and placed a hard copy of the report in the ADEQ Records Management Center for public review. ADEQ opened a 30-day public comment period on December 3, 2012. A copy of the public notice certification, alongExceptional Event, Phoenix, August 18, 2011 Introduction



### 3 

### with any comments received, will be submitted to EPA, consistent with the requirements of 40 CFR 50.14(c)(3)(iv). See Appendix E for a copy of the affidavit of public notice.



## 1.2.5 Submit Demonstration Supporting Exceptional Event Flag (40 CFR 50.14(a)(1-2))

At the close of the public comment period and after ADEQ has had the opportunity to consider any comments submitted on this document, ADEQ will submit this document, the comments received, and ADEQ’s responses to those comments to EPA Region 9 headquarters in San Francisco, California. The deadline for the submittal of this package is September 30,

2014.



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

The EER states that in order to justify the exclusion of air quality monitoring data, evidence must be provided for the following elements:

1. The event satisfies the criteria set forth in 40 CFR 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.Exceptional Event, Phoenix, August 18, 2011 C onceptual Model



### 1 

# 2. Conceptual Model

This section provides a narrative background and summarizes the meteorological and air quality conditions in place on August 18, 2011, in the Phoenix area. Elements described in

this section include

 A description and map of the geographic settings 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 August 18, 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 typica lly 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. The PM 10 

### exceedances on August 18, 2011, were recorded at the West Chandler, South Phoenix, Central Phoenix, and Buckeye monitors. The National Weather Service (NWS) monitors m easure meteorological data only. Phoenix Sky Harbor International Airport (KPHX), Chandler Municipal Airport (KCHD), and Phoenix Goodyear Airport (KGYR) were the primary NWS sites used in this demonstration package because of those sites’ 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 August 18, 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 in the air and add to regional PM 10 

### loadings during high wind events. Much of this alluvial matter and fine soil is deposited in theExceptional Event, Phoenix, August 18, 2011 Conceptual Model



### 2 

### low-lying areas of central and southern Arizona, with larger depositional areas focused in and around the confluences of dry river channels.

Figure 2-1. Locations of air quality monitors t hat recorded exceedances of the 24-hr

PM 10 

### NAAQS and NWS monitors in the Phoenix area.Exceptional Event, Phoenix, August 18, 2011 Conceptual Model



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

### in Arizona on August 18, 2011.Exceptional Event, Phoenix, August 18, 2011 Conceptual Model



### 4 Figure 2-3. Drainage system of Phoenix, Arizona.Exceptional Event, Phoenix, August 18, 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 mid- to late-summertime period, monsoonal moisture originating from the Gulf of California, Gulf of Mexico, and large thunderstorm complexes over the Sierra Madre

Occidental Mountains in Mexico move northward into Arizona.

0.0 0.2 0.4 0.6 0.8 1.0 1.2

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

Precipitation

Max Temp

Min Temp

Mean Temp



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



### The influx of moisture associated with the monsoon, combined with strong solar heating, can result in unstable atmospheric conditions that are favorable for the development of
thunderstorms. Heavy precipitation associated with thunderstorms, and the eventual collapse or dissipation of thunderstorms, can generate what are known as downbursts. Downbursts are the rapid descent of rain-cooled air in a thunderstorm. Upon reaching the surface, this air rapidly disperses horizontally away from the storm as the outflow boundary (also called gust fronts), as shown in Figure 2-5 . The high winds associated with outflow boundaries can efficiently loft dust into the air and transport the dust over long distances, resulting in dust storms (also called haboobs) with high PM 10 

### concentrations and low visibilities.Exceptional Event, Phoenix, August 18, 2011 Conceptual Model



### 6 Cross

‐ section schematic of a haboob caused by the cool outflow from a thunderstorm, with the leading edge that is propagating ahead of the storm

called an outflow boundary. The strong, gusty winds that prevail at the
boundary are defined as a gust front. The leading edge of the cool air is calle d

the nose, and the upward

‐ protruding part of the features is referred to as the

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

The rapidly moving cool air and the gustiness at the gust front raise dust
(shaded) high into the atmosphere.



### Figure 2-5. Cross-section of a thunderstorm cr eating an outflow boundary and haboob. (Source: Desert Meteorology, Thomas T. Warner, 2004.)



### Dust storms associated with these thunderstorms typically occur in the early part of the monsoon season (July) before subsequent rains moisten the soil and limit potential lofting of soil into the air. However, depending on the amount and frequency of precipitation received during the monsoon season, the extremely hot temperatures can dry the surface soils very quickly; thus, dust storms can occur at any time during the year. Specific PM 10 

### source regions are difficult to determine during thunderstorm-driven dust storms because the thunderstorm outflow
can carry dust over long distances that encompa ss many possible sources of dust. Instead, we
consider general PM 10 

### source regions, which are typically identified based on the locations of the thunderstorms that are believed to have generated the dust-laden outflow winds.



# 2.3 Event Day Summary

On the afternoon and evening of August 18, 2011, strong winds generated by
thunderstorms over central and eastern Arizona transported dust westward into the Phoenix area ( Figure 2-6 ). The windblown dust resulted in 24-hr average PM 10 

### concentrations in exceedance of the NAAQS at four air quality monitors ( 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 east of the Phoenix area, and wind speeds in excess of 30 to 40 mph over whelmed reasonable dust control measures. Monitors across Maricopa, Pinal, and Pima counties recorded high PM 10 

### concentrations during this dust storm, illustrating the widespread, regional nature of the event.Exceptional Event, Phoenix, August 18, 2011 Conceptual Model



### 7 

## Transport of

windblown dust

Figure 2-6. Thunderstorms (bright white areas) over central and eastern Arizona produced outflow boundaries that propagated westward and transported dust to the Phoenix area on August 18, 2011.

Table 2-1. Maricopa County area monitor information and PM 10 

### measurements on August 18, 2011. The four Phoenix-area monito rs discussed in this report are in bold.

Monitor Monitor Type Operator AQS Monitor ID 24-hr Avg

PM 10 (μg/m 3 ) 1-hr

Max

PM 10 (μg/m 3 ) Time of

Max 1-hr

PM 10 (LST) AQS

Qualifier

Flag

Apache County

N/A N/A WMAT 04-001-1003-81102-1 9 29 0700

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 30 74 1200

Maricopa County

Buckeye TEOM MC 04-013-4011-81102-1 296 2946 2000 RJ

Central Phoenix TEOM MC 04-013-3002-81102-4 232 4373 1800 RJ

Durango Complex TEOM MC 04-013-9812-81102-1 152 1395 1800

Dysart TEOM MC 04-013-4010-81102-1 71 723 1900Exceptional Event, Phoenix, August 18, 2011 Conceptual Model



### 8 Fort

McDowell/Yuma

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

Glendale TEOM MC 04-013-2001-81102-1 76 902 1900

Greenwood TEOM MC 04-013-3010-81102-1 107 961 1800

Higley TEOM MC 04-013-4006-81102-1 121 832 1900

JLG Supersite BAM ADEQ 04-013-9997-81102-3 80 985 1800

JLG Supersite TEOM ADEQ 04-013-9997-81102-4 87 1155 1800

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

South Phoenix TEOM MC 04-013-4003-81102-1 179 2496 1800 RJ

West Chandler TEOM MC 04-013-4004-81102-1 186 1564 1800 RJ

West 43 rd Avenue TEOM MC 04-013-4009-81102-1 144 1300 1900

West Phoenix TEOM MC 04-013-0019-81102-1 76 622 1900

Zuni Hills TEOM MC 04-013-4016-81102-1 100 1292 1800

Navajo County

N/A N/A WMAT 04-017-1002-81102-1 12 44 1300

Pima County

Ajo TEOM ADEQ 04-019-0001-81102-3 206 1354 2100 RJ

Geronimo BAM PCDEQ 04-019-1113-81102-1 21 132 1600

Green Valley BAM PCDEQ 04-019-1030-81102-1 N/A N/A N/A

Orange Grove FRM PCDEQ 04-019-0011-81102-2 18 N/A N/A

Rillito TEOM ADEQ 04-019-0020-81102-3 65 758 1500 IJ

South Tucson FRM PCDEQ 04-019-1001-81102-1 21 N/A N/A

Pinal County

Apache Junction

Fire Station TEOM PCAQCD 04-021-3002-81102-3 N/A N/A N/A

Casa Grande

Downtown TEOM PCAQCD 04-021-0001-81102-3 200 2883 1700 RJ

Combs School TEOM PCAQCD 04-021-3009-81102-3 195 3323 1800 RJ

Cowtown TEOM PCAQCD 04-021-3013-81102-3 731 6493 2000 RJ

Maricopa TEOM PCAQCD 04-021-3010-81102-3 199 1939 2000 RJ

Pinal County

Housing TEOM PCAQCD 04-021-3011-81102-3 454 5600 1700 RJ

Stanfield TEOM PCAQCD 04-021-3008-81102-3 224 2655 1700 RJ

Santa Cruz County

Nogales Post Office BAM ADEQ 04-023-0004-81102-3 45 97 400

Yuma County

Yuma Supersite TEOM ADEQ 04-027-8011-81102-3 42 262 1700

TEOM: Tapered element oscillating microbalance monitor

BAM: Beta attenuation monitor

FRM: Federal reference method WMAT: White Mountain Apache Tribe of Fort Apache Reservation, AZ ADEQ: Arizona Department of Environmental Quality MC: Maricopa County Air Quality Department

FMIR: Fort McDowell Indian Reservation PCAQCD: Pinal County Air Quality Control DistrictExceptional Event, Phoenix, August 18, 2011 Conceptual Model



### 9 PCDEQ: Pima County Department of Environmental Quality RJ: qualifier flag for high winds IJ: qualifier flag for high windsExceptional Event, Phoenix, August 18, 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 August 18, 2011. On the afternoon of August 18, thunderstorms developed over the higher terrain of central and eastern Arizona, just east of the Phoenix area ( Figure 3-1 ). These thunderstorms generated dust-carrying outflow boundaries that propagated westward across
the Phoenix area. As stated in Section 2.2, thunderstorms associated with the summer
monsoon season can generate strong winds that producing blowing dust across Arizona. The likely source regions for PM 10 

### during the August 18, 2011, event were the deserts east and southeast of the Phoenix area and along the path of the outflow boundaries from those deserts westward into Maricopa County. This region largely consists of natural, undisturbed desert. The last rainfall in the Phoenix area preceding the August 18, 2011, event was minimal, with 0.17 inches recorded at Phoenix-Sky Harbor International Airport (KPHX) on August 3, 2011. The combination of geography and lack of rainfall preceding the event resulted in a large source region of soils that were particularly vulnerable to particulate suspension.

Figure 3-1. Visible satellite image from 1630 LST on August 18, 2011 (GOES-West). Bright white areas indicate tall, convective (thunderstorm) clouds. Thunderstorms over central and eastern Arizona generated outflow boundaries that carried dust westward

across the Phoenix area.

1Exceptional Event, Phoenix, August 18, 2011 Causal Relationship



### Figure 3-2 and Table 3-1 summarize the progression of the thunderstorm outflow boundaries and windblown dust as it moved through southwestern Arizona. Initially, one outflow boundary approached the Phoenix area from the southeast while a second outflow boundary approached from the east. The southeastern boundary first arrived in the Phoenix area around 1700 LST on August 18, which carried windblown dust to the West Chandler monitor. Sustained winds of 32 mph and a peak gust of 41 mph were reported at the Chandler Municipal Airport (KCHD). The outflow boundary continued northwestward and carried windblown dust to the Central Phoenix and South Phoenix monitors during the 1800 LST hour. Phoenix Sky Harbor International Airport (KPHX) reported sustained winds of 28 mph with gusts to 39 mph. Figure 3-3 shows radar velocity data that illustrate the locations of the two outflow boundaries as they approached Phoenix. The two outflow boundaries merged and continued to propagate
westward across the Phoenix metropolitan area, eventually carrying windblown dust to the Buckeye monitor at 2000 LST. Other PM 10 

### monitors in the Phoenix area also recorded elevated

PM 10 

### concentrations as the outflow boundary passed, but the concentrations were not high enough to result in exceedances of the NAAQS.

Figure 3-2. Phoenix-area air quality and meteorological monitors, and general wind

direction. Wind and PM 10 

### data for the monitors are shown in Table 3-1, along with the names of the stations. Gusty winds associated with thunderstorm outflow transported dust across the Phoenix area during the late afternoon hours of August 18, 2011.

2Exceptional Event, Phoenix, August 18, 2011 Causal Relationship



### Table 3-1. Observed wind speeds and wind gusts at Maricopa County air quality and meteorological monitors on August 18, 2011. All air quality monitors reported high PM 10 

### concentrations from 1800 to 2000 LST on August 18, 2011, coincident with high wind speeds and wind gusts.

Monitor 1-hr Max

PM 10 

### (μg/m 3 

### ) Time of

Observation (LST) Wind Speed (mph) Wind Gust (mph) Wind

Direction (degrees)

KCHD - 1727 32 41 180

West

Chandler 1564 1800 18 38 132

South

Phoenix 2496 1800 10 35 158

Central

Phoenix 4373 1800 14 39 153

KPHX - 1835 28 39 140

KGYR - 1950 26 31 120

Buckeye 2946 2000 16 34 106

3Exceptional Event, Phoenix, August 18, 2011 Causal Relationship



## Radar site 

# A B

Figure 3-3. Radar base velocity data at 1806 LST on August 18, 2011, from NWS Phoenix Doppler radar. Green indicates flow toward t he radar; dark orange and red indicate flow away from the radar, and yellow indicates little motion aw ay from the radar. Two well-defined outflow boundaries (dashed lines) approached the Phoenix ar ea from the southeast (A) and east (B). These boundaries carried dust northward and westward, respectively, across the Phoenix metropolitan area.



### Monitors in the Phoenix area measured sustained winds of over 20 mph and wind gusts in excess of 30 mph, coincident with the sharp increase in PM 10 

### concentrations ( Figure 3-4

, Figure 3-5 , and Appendix A). Visibility at KPHX also decreased significantly with the arrival of the dust ( Figure 3-6 ), prompting the NWS office in Phoenix, Arizona, to issue a Dust Storm Warning for Maricopa County (see Appendix D for the statements issued by NWS). Similar reductions in visibility were reported at KCHD (near the West Chandler PM 10 

### monitor) and at KGYR (just east of the Buckeye PM 10 

### monitor). It is also noteworthy that, before the abrupt

increase in PM 10 

### concentrations at each monitor, winds were comparatively much lighter and

PM 10 

### concentrations were much lower, illustrating the correlation between the high winds and the dust. Visibility cameras in the Phoenix area also clearly depict the rapid arrival of dust and the resulting significant reduction in visibility after 1700 LST on August 18, 2011. Links to these
videos, other media coverage, and images pertaining to this windblown dust event are shown in
Appendix B.

4Exceptional Event, Phoenix, August 18, 2011 Causal Relationship



### Figure 3-4. Hourly PM 10 

### concentrations and wind speeds at the West Chandler monitor on August 18 and 19, 2011. PM 10 

### concentrations and wind speeds sharply increased at 1600 LST on August 18, 2011, indicating the arrival of windblown dust. Sustained winds of 20 mph were measured with gusts over 35 mph.

Figure 3-5 . Hourly PM 10 

### concentrations and wind speeds at the Buckeye monitor on August 18 and 19, 2011. PM 10 

### concentrations sharply increased with wind gusts over 35 mph at 2000 LST on August 18, 2011, indicati ng the arrival of windblown dust.

5Exceptional Event, Phoenix, August 18, 2011 Causal Relationship



### Figure 3-6. Hourly PM 10 

### concentrations at the Phoenix-area PM 10 

### monitors and visibility at KPHX. Visibility was significantly reduced at KPHX between 1800 and 1900 LST, coincident with the sharp increase in PM 10 

### concentrations at area PM 10 

### monitors, indicating the arrival of windblown dust.



# 3.2 Summary

The information presented in this section demonstrates a clear causal relationship

between the windblown dust and the PM 10 

### exceedances measured at four Phoenix-area
monitors on August 18, 2011. The radar and wind data shown in this section illustrate the spatial and temporal extent 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 Appendix
A show that the sharp increase in PM 10 

### concentrations coincided with the strong wind speeds and wind gusts, and that the strong winds were experienced over a large area.

6Exceptional Event, Phoenix, August 18, 2011 Historical Norm



# 4. Historical Norm

4. 1 Analysis

PM 10 

### concentrations measured at the Central Phoenix monitor on August 18, 2011, were unusual and in excess of normal historical fluctuations. To establish the severity of this
event, PM 10 

### concentrations measured on August 18, 2011, were compared to a historical 2007– 2011 five-year annual data set at each monitor (see Figure 4-1 and Appendix C). The PM 10 

### concentrations measured at the Central Phoenix monitor (Figure 4-1) on August 18, 2011, were
among the highest 24-hr averages measured over the five-year period. Similar time-series plots for the West Chandler, South Phoenix, and Buckeye monitors are shown in Appendix C.



# 4. 2 Summary

Given the recorded values and using methods for assessing historical air quality similar
to those accepted by the EPA, it is clear that the PM 10 

### levels on August 18, 2011, were outside of normal historical fluctuations. This analysis provides evidence that the event affected air
quality on an historic scale.

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



### Date Central Phoenix 5-Year Historical Fluctuation - 24 Hour Averages

August 18, 2011

July - Sept, 2011



### Figure 4-1. Twenty-four-hour average PM 10 

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

### concentration on August 18, 2011, is highlighted in red.Exceptional Event, Phoenix, August 18, 2011 Not Re as onably 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 Maricopa County Dust Control Forecast of “High Risk”, (2) ADEQ forecasters issue a High Pollution Advisory, or (3) near-real-time moni toring data indicate unique activity via high PM concentrations. The forecasting program and inspection/compliance programs work together so that resources can be best utilized during days of greatest risk for elevated PM

emissions.

On July 25, 2002, EPA took initial action to finalize approval of the Best Available Control Measure (BACM) and the Most Stringent Measure (MSM) demonstrations in the Serious

Area PM 10 

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

### nonattainment area (67 FR 48718). These BACM and MSM demonstrations were again approved by EPA on July 14, 2006 (71 FR 43979). The Agricultural Best Management Practices General Permit rule and related definitions have been adopted into the Arizona Administrative Code as R18-2-610 and R18-2-611, pursuant to Arizona Revised Statutes
§49-457 1



### .



## 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, August 18, 2011 Not Reas onably Controllable or Preventable



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



### Rule/Ordinance Number & Title Description

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

Rule 310: Fugitive dust from dustgenerating operations Establishes limits for the emissions of particulate matter into the ambient air from any property, operations, or activity that may serve as a fugitive dust source.

Rule 310.01: Fugitive dust from nontraditional sources of fugitive dust Establishes limits for the emissions of particulate matter into the ambient air from open areas, vacant lots, unpaved parking lots, and unpaved roadways which are not regulated by Rule 310 and which are not required to have either a permit or a dust control plan.

Rule 311: Particulate matter from process industries Establishes emission rates based on process weight applicable to any affected operations not subject to Rule 316.

Rule 312: Abrasive blasting Establishes limits for particulate emissions from abrasive blasting operations.

Rule 314: Open outdoor fires and indoor fireplaces at commercial and

institutional establishments Establishes limits for the emission s 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 emissi ons 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 emissi ons 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 unincor porated sections of Area A in Maricopa County.

Ordinance P-28: Off-road vehicle use in unincorporated areas of Maricopa County Establishes restrictions for operating vehicles on unpaved property in unincorporated areas of Maricopa County.

Arizona Administrative Code R18-

2-611 & 610: Agricultural PM 10 

### general permit Establishes a requirement for commercial farmers to implement best management practices and maintain a record demonstrating compliance.Exceptional Event, Phoenix, August 18, 2011 Not Reas onably Controllable or Preventable



### 3 

## 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 exis ting and new non-point sources.



### Article Number & Title Description

Article 2: Fugitive dust Provides a mechanism to reasonably regulate operations which periodically may cause fugitive dust emissions into the atmosphere.

Article 3: Construction sites – fugitive dust Improves the control of excessive fugitive dust emissions that have been traditionally associated with construction, earthwork, and land development, and thereby minimize nuisance impacts.

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

Phoenix PM 10 

### Nonattainment Area.



### Article Number & Title Description

Article 4: Nonattainment area rules; dustproofing for commercial parking, drives, and yards Establishes rules to avoid violations of the prevailing PM 10 

### standard and additionally minimize nuisance impacts by improving control of excessive fugitive dust emissions from unpaved parking lots.

Article 5: Nonattainment area rules; stabilizati on 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.

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 10Exceptional Event, Phoenix, August 18, 2011 Not Reas onably Controllable or Preventable



### 4 

### 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 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.

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 and surveillance inspections, conducted both during and after significant air quality events. MCAQD routinely inspects dust control-permitted sites and increases the frequency of inspections for permits covering areas of 10 acres or more. Rule 316 sources areExceptional Event, Phoenix, August 18, 2011 Not Reas onably Controllable or Preventable



### 5 

### also regularly inspected multiple times every ye ar. Maricopa County responds to the majority of
complaints within 24 hours.

Maricopa County monitors the ADEQ Five-Day Dust Control Forecast to identify the
potential for elevated PM 10 

### pollution levels due to high winds or stagnant conditions. When a High Pollution Advisory (HPA) is issued 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-inspection of 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-min intervals. Previously, only hourly readings were available. The real-time data reporting system

includes a mechanism to alert MCAQD field staff when PM concentrations are elevated. The system allows MCAQD responders to review conc entrations at the monitors and to consult the NWS website to check for weather event activity. This capability allows the MCAQD responder to identify regional events and monitor specific issues. If necessary, the MCAQD responders can inform nearby stakeholders and lo cal governments of the elevated PM 10 

### concentraitons.



## 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 August 18, 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 15–21, 2011, MCAQD inspectors conducted a total of 236 inspections of permitted facilities, 177 of which were sources of fugitive dust. Additionally, MCAQD conducted
35 inspections on vacant lots and unpaved parking lots during this period. During this 7-day period, a total of 19 violations were issued countywide for PM 10 

### and non-PM 10 

### -related

violations. No violations were issued for PM 10 

### emissions within a 4-mile radius of any
exceeding monitor.

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 forecast high-windExceptional Event, Phoenix, August 18, 2011 Not Reas onably Controllable or Preventable



### 6 

### alert days. Should the PM 10 

### readings at a MCAQD air monitoring site show a 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.

Based on a review of the inspection reports and site visit documentations, there is no evidence to suggest that agricultural activities produced unusual PM 10 

### emissions. On August 17, 2011, the ADEQ AgBMP inspector perform ed one site visit in the Gilbert area.



# 5 .2 Forecasts and Warnings

Dust forecasts and statements were released prior to the event by both ADEQ and the NWS office in Phoenix (Appendix D). For August 18, 2011, a Maricopa County Dust Control Forecast was issued by ADEQ, indicating a moderate risk level for unhealthy PM 10 

### . The Dust Control Forecast also indicated a potential for strong and gusty winds throughout the area as well as dense blowing and transported dust generated by outflow from thunderstorms.

At 1644 LST on August 18, 2011, the NWS in Phoenix issued a Dust Storm Warning for Maricopa County, indicating that “winds have generated large areas of blowing dust or blowing sand that have substantially reduced visibilities... to 1⁄4 mile or less.” Similarly, at 1654 LST, the NWS issued a Severe Thunderstorm Warning for Maricopa County, indicating damaging winds in excess of 60 mph were possible and that “dense blowing dust may accompany” the thunderstorms.” At 1744 LST, a statement from the NWS indicated that “the leading edge of gusty south to southeast winds 25 to 40 mph had reached the southeast Valley... the gust front and areas of dense blowing dust will push toward the north and west... and affect much of the central and southeast portion of the Greater Phoenix Metropolitan Area by 6 p.m.” The issuance of these statements by the NWS coincided with the peak PM 10 

### concentration, of 1,564 μg/m 3 

### , recorded at the West Chandler monitor; of the four monitors with PM 10 

### exceedances, this was the first monitor to be impacted by the windblown dust. The NWS issued several similar statements through 2000 LST as the windblown dust continued westward across Maricopa County.



# 5 .3 Wind Observations

Sustained wind speeds of over 20 mph with gusts over 30 mph were reported at monitors across the Phoenix area as the outflow boundaries moved through (Figure 3-4 and Appendix A).



# 5.4 Summary

The thunderstorm outflow event of August 18, 2011 produced strong winds that
transported dust and PM 10 

### into the Phoenix PM 10 

### Nonattainment Area. The source region of the outflows that caused the exceedances was largely located in areas outside the Phoenix

PM 10 

### nonattainment area, primarily the deserts of Pinal and southern Maricopa County. The Phoenix area is designated as a serious nonattainment area for PM 10 

### and is required to haveExceptional Event, Phoenix, August 18, 2011 Not Reasonably Controllable or Preventable



### 7 

### BACM for all significant sources of PM 10 

### . BACM on significant anthropogenic sources were in place and enforced during the events, and pro-active tracking and response to the events by regulatory agencies and local governments confirmed the uncontrollable nature of the dust emissions; therefore, these pre-existing prior-approved required controls are adequate for meeting the requirements of an exceptional event and should be considered “reasonable” for
these purposes.

Despite the deployment of comprehensive control measures and sophisticated response programs, high-wind conditions associated with thunderstorms and thunderstorm outflows brought high concentrations of PM 10 

### emissions 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 all 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 August 18, 2011 recorded within the Phoenix PM 10 

### nonattainment area were
not reasonably controllable or preventable.Exceptional Event, Phoenix, August 18, 2011 B ut-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 August 18, 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 east and southeast of Phoenix. The weight of evidence presented in this submittal provides no alternative that could tie the exceedances of August 18, 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 this uncontrollable natural event.

As detailed in Section 5, all reasonable control measures were in place and/or
implemented on a continual basis. Air quality -related inspection and compliance data revealed no violations or complaints within three days before or after the time of the event. 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 August 18, 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 this uncontrollable natural event.Exceptional Event, Phoenix, August 18, 2011 C onclusions



### 1 

# 7. Conclusions

The PM 10 

### exceedances that occurred on August 18, 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:

 Th e 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;

 There is a clear causal relationship between the measurement(s) under consideration
and the event;

 The event is associated with a measured concentration(s) in excess of normal historical
fluctuations; and

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



# 7 .1 Affects Air Quality

As stated in the preamble to the EER, the event in question is considered to have affected air quality if it can be shown that there is a clear causal relationship between the
monitored exceedance and the event, and that the event is associated with a measured concentration in excess of normal historical fluctuations. Given the information presented in Sections 2, 3, 4, and 5, we can reasonably conclude that the event in question affected air
quality.



# 7 .2 Not Reasonably Controllable or Preventable

Section 50.1(j) of 40 CFR Part 50 requires that an event must be “not reasonably
controllable or preventable” in order to be defined as an exceptional event. This requirement is
met by demonstrating that, despite reasonable control measures in place within Maricopa County, high winds overwhelmed all reasonabl y available controls (Section 5). The PM 10 

### 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 August 18, 2011, were not reasonably controllable or preventable.



# 7.3 Natural Event

As discussed above, the PM 10 

### exceedances on August 18, 2011, were shown to be
caused by PM 10 

### transported into the Phoenix area by thunderstorm outflow. The event therefore qualifies as a natural event.Exceptional Event, Phoenix, August 18, 2011 Conclusions



### 2 

# 7.4 Clear Causal Relationship

The following points demonstrate that the high PM 10 

### concentrations were caused by

windblown dust:

 Time-serie s graphs of PM 10 

### concentrations show that the timing of high PM 10 

### at Phoenix-area monitors was consistent with gusty winds and low visibilities (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 (Section 3).

 Dry conditi ons preceding the event resulted in soils that were particularly susceptible to particulate suspension by high winds (Section 3).

 Visibility camera imageryshows that large quantities of PM 10 

### were transported into the Phoenix area on August 18, 2011. The timing of the dust storm depicted in the visibility
camera imagery is consistent with the PM 10 

### concentration measurements, elevated
winds, and reduced visibility.



# 7 .5 Historical Norm

The 24-hr average PM 10 

### values measured at the exceedance monitors were in excess of normal historical fluctuations, based on a comparison with 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 August 18, 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 of the Phoenix PM 10 

### nonattainment area.Exceptional Event, Phoenix, August 18, 2011 Appendix A



# A ppendix A: Air Quality and Meteorological Data

This section contains time-series graphs of PM 10 

### concentrations and wind data for
Phoenix-area monitors on August 18 and 19, 2011. The data show a region-wide increase in wind speeds and wind gusts coincident with the arrival of dust and high PM 10



### .

Figure A-1. Hourly PM 10 

### concentrations and wind speeds at the Central Phoenix monitor on August 18 and 19, 2011. PM 10 

### concentrations and wind gusts sharply increased at 1800 LST on August 18, 2011, indicating the arrival of windblown dust.

1Exceptional Event, Phoenix, August 18, 2011 Appendix A



### Figure A-2. Hourly PM 10 

### concentrations and wind speeds at the South Phoenix monitor on August 18 and 19, 2011. PM 10 

### concentrations and wind gusts sharply increased at 1800 LST on August 18, 2011, indicating the arrival of windblown dust.

2

### 3U.S. Department of CommerceNational Oceanic &Atmospheric AdministrationQUALITY-CONTROLLED LOCAL CLIMATOLOGICAL DATAHOURLY OBSERVATIONS TABLEPHOENIX SKY HARBOR INTL AIRPORT (23183)PHOENIX, AZ (08/2011)National Climatic Data CenterFederal Building151 Patton AvenueAsheville, North Carolina 28801Elevation:1107 ft. above sea levelLatitude:33.427Longitude:-112.003Data Version:VER3DryBulbTempWetBulbTempDewPointTempDateTime(LST)StationTypeSkyConditionsVisibility(SM)WeatherType(F)(C)(F)(C)(F)(C)RelHumd%WindSpeed(MPH)WindDirWindGusts(MPH)StationPressure(in. hg)PressTendNet3-hrChg(mb)SeaLevelPressure(in. hg)ReportTypePrecip.Total(in)Altimeter(in. hg)123456789101112131415161718192021222318181818181818181818181818181818181818181818181818181818181818181818005101510251035104510551065107510851095110511151125113511451155116511751180018041812183518401848184918511918194719512033205121512251235111111111111111111111111111111111111111111111111111111111111111111111SCT200 BKN250FEW150 SCT250FEW150 SCT250FEW150 SCT250FEW150 SCT250SCT150 BKN250FEW150 SCT250FEW150 SCT250FEW150 SCT250FEW100 SCT180 SCT250FEW110 SCT180 SCT250FEW120 SCT180 SCT250FEW120 SCT250FEW120 SCT250SCT120 SCT190 BKN250SCT120 SCT190 BKN250FEW090 SCT120 BKN200SCT090 SCT120 BKN200SCT090 SCT120 BKN200BKN006 OVC110BKN006 BKN110 BKN250BKN010 BKN110 BKN250BKN010 BKN110 BKN250BKN020 BKN110 BKN250BKN020 BKN110 BKN250BKN020 BKN110 BKN250SCT110 SCT150 BKN200SCT110CB SCT150SCT110CB SCT150SCT120 BKN150 BKN200SCT120 BKN150 BKN200FEW120 SCT150 BKN200FEW120 SCT150 BKN250FEW120 SCT150 BKN25010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.001.250.500.501.002.002.004.004.008.0010.0010.0010.0010.0010.0010.0010.00DSDSBLDUBLDUBLDUBLDUBLDU999899979693939610010210410610810911111110910710299999393919192908485828486848437.236.737.236.135.633.933.935.637.838.940.041.142.242.843.943.942.841.739.037.037.034.034.033.033.033.332.029.029.428.028.930.028.928.97171717171727273727171717272737372727274747474747474747273737372717121.421.521.621.821.722.022.022.522.321.921.721.822.322.222.522.522.422.322.323.523.523.523.523.223.223.423.122.122.622.522.522.121.821.55556565858616161585553525352525253545763636666666666666667686765656412.813.313.314.414.416.116.116.114.412.811.711.111.711.111.111.111.712.214.017.017.019.019.019.019.018.919.019.019.420.019.418.318.317.8232524272834343125211817161514141617233131414144444245555563575053516300035573073910149822242328212523222524182422999250260000000000100080110010VR000VRVR3102702502602701501601701401401401401301201201201001101501501502124183334323938383838363434313228.6428.6428.6428.6428.6528.6628.6828.6928.6928.6928.6928.6628.6328.6028.5728.5428.5428.5728.5828.5828.5928.6228.6228.6328.6328.6428.6628.7028.7128.7228.7228.7328.7328.710318853000000301600302801905000629.7429.7429.7429.7429.7529.7629.7829.8029.7929.8029.7829.7629.7329.7029.6729.6329.6429.67MMMMMMM29.75MM29.82M29.8329.8529.8429.82AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAASPSPSPSPSPSPSPAASPSPAASPAAAAAAAA29.8129.8129.8129.8129.8229.8329.8529.8629.8629.8729.8629.8329.8029.7729.7429.7129.7129.7429.7529.7529.7629.7929.7929.8029.8029.8129.8329.8829.8929.9029.9029.9129.9129.89Figure A-3.Quality-controlled local climatological data hourly observations table for Phoenix Sky Harbor International Airport, Phoenix, AZ(08/18/2011). Note in the Weather Type column that a DS (dust storm) and BLDU (blowing dust) were reported. Dynamically generated viahttp://cdo.ncdc.noaa.gov/qclcd/QCLCD.

### 4U.S. Department of CommerceNational Oceanic & Atmospheric AdministrationQUALITY-CONTROLLED LOCALCLIMATOLOGICAL DATAHOURLY OBSERVATIONS TABLEPHOENIX GOODYEAR AIRPORT (03186)GOODYEAR, AZ(08/2011)National Climatic Data CenterFederal Building151 Patton AvenueAsheville, North Carolina 28801Elevation: 968 ft. above sea levelLatitude: 33.416Longitude: -112.383Data Version: VER2DryBulbTempWetBulbTempDewPointTempDateTime(LST)StationTypeSkyConditionsVisibility(SM)WeatherType(F)(C)(F)(C)(F)(C)RelHumd%WindSpeed(MPH)WindDirWindGusts(MPH)StationPressure(in. hg)PressTendNet3-hrChg(mb)SeaLevelPressure(in. hg)ReportTypePrecip.Total(in)Altimeter(in. hg)123456789101112131415161718192021222318181818181818181818181818181818180547064707470847094710471147124713471447154716501747184719502030205000000000000000000FEW100 SCT180 BKN250FEW100 SCT180 BKN250FEW100 SCT180 BKN250FEW120 FEW180 SCT250FEW180 SCT250FEW180 SCT250FEW180 SCT250FEW120 FEW180 SCT250FEW120 FEW180 SCT250FEW120 SCT250FEW120 BKN250FEW120 FEW180 BKN250FEW090 SCT120 SCT200FEW090 BKN120 OVC200FEW090 BKN120 OVC200SCT120 BKN200SCT120 BKN20010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.005.001.005.005.00BLDUBLDUBLDUBLDU9090939710010210610810911111110910210090868432.032.034.036.038.039.041.042.043.044.044.043.039.038.032.030.029.0727272747472717373757575767575747322.222.222.123.223.122.421.822.522.923.623.623.824.223.723.723.122.8636361636157525455575759646368686817.017.016.017.016.014.011.012.013.014.014.015.018.017.020.020.020.041413433282317171717172029304855598687863991114141116262321240240240250250230VR25025028027026021021012012012020212934342928.8028.8228.8428.8428.8528.8428.8128.7828.7528.7228.6828.6828.7028.7128.8128.8428.86MMMMMMMMMMMMMMMMMAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA29.8329.8529.8729.8729.8829.8729.8429.8129.7829.7529.7129.7129.7329.7429.8429.8729.89Figure A-4.Quality-controlled local climatological data hourly observationstable for Phoenix Goodyear Airport, Goodyear, AZ (08/18/2011).Note in the Weather Type column that BLDU (blowing dust)was reported for several hours. Dynamically generated viahttp://cdo.ncdc.noaa.gov/qclcd/QCLCD.

### 5U.S. Department of CommerceNational Oceanic & Atmospheric AdministrationQUALITY-CONTROLLED LOCALCLIMATOLOGICAL DATAHOURLY OBSERVATIONS TABLECHANDLER MUNICIPAL AIRPORT (53128)CHANDLER, AZ(08/2011)National Climatic Data CenterFederal Building151 Patton AvenueAsheville, North Carolina 28801Elevation: 1243 ft. above sea levelLatitude: 33.268Longitude: -111.812Data Version: VER2DryBulbTempWetBulbTempDewPointTempDateTime(LST)StationTypeSkyConditionsVisibility(SM)WeatherType(F)(C)(F)(C)(F)(C)RelHumd%WindSpeed(MPH)WindDirWindGusts(MPH)StationPressure(in. hg)PressTendNet3-hrChg(mb)SeaLevelPressure(in. hg)ReportTypePrecip.Total(in)Altimeter(in. hg)12345678910111213141516171819202122231818181818181818181818181818181818181805520648074908470947104711471248134814471547164717271750181018301848194720500000000000000000000SCT150 BKN200SCT150 BKN200FEW150 BKN200FEW150SCT150FEW110 SCT250FEW110 SCT250SCT110 SCT200SCT100 BKN200SCT100 BKN250SCT100 BKN250SCT120 BKN250BKN050BKN050BKN050BKN050BKN050 BKN100BKN050 BKN150BKN050 BKN15040.0040.0040.0040.0040.0035.0035.0030.0020.0030.0020.0020.000.50s1.003.002.008.0010.0010.00BLDUDSBLDUBLDU8690939710010210610810910911110810093908482818130.032.034.036.038.039.041.042.043.043.044.042.038.034.032.029.028.027.027.07171727374737373737373737573727371727121.521.622.022.623.122.822.922.522.622.622.922.523.622.622.422.821.822.321.66361616161595754545454546363646866686617.016.016.016.016.015.014.012.012.012.012.012.017.017.018.020.019.020.019.0463834302824201716161517303742595865603576737996131132172326302529100VR1601501801502402102302902802901801701501001000900602341262939393428.5328.5528.5628.5728.5728.5628.5328.5028.4728.4428.4028.4228.4628.4828.5028.5228.5428.5628.60MMMMMMMMMMMMMMMMMMMAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA29.8529.8729.8829.8929.8929.8829.8529.8229.7929.7629.7229.7329.7729.8029.8229.8429.8629.8829.92Figure A-5.Quality-controlled local climatological data hourly observationstable for Chandler Municipal Airport, Chandler, AZ (08/18/2011).Note in the Weather Type column that a DS (dust storm) andBLDU (blowing dust) were reported. Dynamically generated viahttp://cdo.ncdc.noaa.gov/qclcd/QCLCD.Exceptional Event, Phoenix, August 18, 2011 Appendix B



# Appendix B: Media Coverage, Videos, and Images

Video Links

ADEQ visibility cameras in the Phoenix area:

South Mountain: www.phoenixvis.net/videos/mpeg4/SOMT_08182011.mp4

Estrella Mountains: www.phoenixvis.net/videos/mpeg4/ESMO_08182011.mp4

Camelback Mountains: www.phoenixvis.net/videos/mpeg4/CAME_08182011.mp4

Superstition Mountains: www.phoenixvis.net/videos/mpeg4/SUPM_08182011.mp4

Local citizens often create videos during dust storms, documenting their observations. Here are

a few links to these videos.

http://www.youtube.com/watch?v=HJP4daOMUdM

http://www.youtube.com/watch?v=xZeUucphi-I

http://www.youtube.com/watch?v=MlyKfzaBH4gExceptional Event, Phoenix, August 18, 2011 Appendix B



# Media Article and Image Links

http://articles.latimes.com/2011/aug/18/nation/la-naw-phoenix-storm-20110819

Dust storm in Phoenix makes driving — and breathing — risky: Flights are delayed, poles are toppled and thousands lose power. It was the third major dust storm to hit the city since July.

August 18, 2011 Los Angeles Times Staff Writer

PHOENIX — A giant wall of dust rolled through the Phoenix area Thursday for the third time since early July -- turning the sky brown, creating dangerous driving conditions and delaying some airline flights.

The dust storm, also known as a haboob in Arabic and around Arizona, swept through Pinal County and headed northeast, reaching Phoenix at about 6 p.m.

Some incoming and departing flights at Phoenix Sky Harbor International Airport were temporarily delayed because of the storm, accordi ng to airport officials who couldn't immediately provide exact numbers. Takeoffs and landings resumed at about 6:50 p.m.

National Weather Service meteorologists said a powerful thunderstorm packing winds of up to 60 mph hit Pinal County and pushed the dust storm toward Arizona's most populous county. There were several reports of downed poles, and Salt River Project officials said 3,500 of its customers were without electricity, mostly in the Queen Creek area southeast of Phoenix.

There were no immediate reports of any weather-related auto accidents.

It was the third major dust storm to hit the Phoenix metro area since last month. A haboob on July 5 brought a mile-high wall of dust that halted airline flights, knocked out power for 10,000 people and covered everything in its path with a thick sheet of dust. Another dust storm hit July 18, reaching heights of 3,000 to 4,000 feet, delaying flights and cutting off power for more than 2,000 people in the Phoenix metro area.

Weather officials say haboobs only happen in Arizona, the Sahara desert and parts of the Middle East because of dry conditions and large amounts of sand.

Pollution levels skyrocket during dust storms and create even more breathing problems for people with asthma and other similar conditions.Exceptional Event, Phoenix, August 18, 2011 Appendix B



### http://www.cbsnews.com/2100-201_162-20094755.html

Another giant dust storm coats Phoenix in dirt

August 19, 2011, 3:08 PM

AP

PHOENIX - A thick cloud of dust has swallowed Phoenix at sundown three times this summer, covering the city with grit and baffling even longtime residents who can't remember seeing so many dramatic "haboobs" during a monsoon season.

A 1,000-feet-high wall of dust traveled at least 50 miles into metro Phoenix and neighboring Pinal County on Thursday evening before dissipating.

It turned the skies brown, reduced visibility , created dangerous driving conditions and caused some airline flights to be delayed. The storm, also known by the Arabic word haboob, also coated anything left outside in a thin layer of fine dirt and left some people who walked outside for a minute or two with grit between their teeth.

Danny Shepherd, a deejay who was driving to a gig at a coffee house during the storm, has lived in metropolitan Phoenix since 1989 and can't recall so many big dust storms in one year. "They're typical but I also think there's been a lo t more this year -- big ones and small ones and the haboob, the grand-daddy of them all," Shepherd said.

National Weather Service meteorologist Ken Waters said the area is experiencing a typical number of dust storms this year, but what sets this season apart from others is the size and power of three of the storms.

"Each year, you are going to get some variety of the dust storms," Waters said. "We don't see a single causative factor for why they seem to be stronger this year."

Waters said thunderstorms moving through southern Arizona supplied winds of up to 60 mphthat stirred up fine dust in the agricultural fields and sent Thursday's storm to the nation's sixthlargest city.

"It was a strong dust storm, but nothing on the order of the big one in July," he said.

This season's most powerful dust storm came on July 5 when a mile-high wall of dust halted airline flights, knocked out power for 10,000 people and covered everything in its path with a thick sheet of dust. Another dust storm hit July 18 reaching heights of 3,000 to 4,000 feet, delaying flights and cutting off power for more than 2,000 people in the Phoenix metro area.

Weather experts said such massive dust storms only happen in Arizona, Africa's Sahara desert and parts of the Middle East because of dry conditions and large amounts of sand.

At a Honda car dealership in Phoenix, a crew of four men used a portable pressure washer to

hose down vehicles covered in a thick coat of dust that made the car windows opaque.Exceptional Event, Phoenix, August 18, 2011 Appendix B



### Erik Fisher, a new car director at the dealership, estimated his crew will have to wash about 350 cars Friday thanks to the dust storm. "They'll probably be out there half a day," Fisher said. "It's a lot of extra man power."

Pollution levels skyrocket during dust storms and create even more breathing problems for people with asthma and other conditions.

Enemencio Campos, right, and Pedro Lopez, both of Eloy, Ariz., pick up roofing debris Aug. 19, 2011, from the middle of an Eloy street the day after a violent storm hit the area. Pinal County authorities are assessing damage in Eloy after a summer storm rolled through, leaving behind a path of destruction. Homes were damaged, roofs were torn off businesses and a junior-high school had part of its roof missing.

Dennis Dickerson, a compliance manager at the Maricopa County Air Quality Department, said Thursday's dust storm dramatically raised ai r pollution levels. Dickerson said even people without health issues should stay out of severe dusts storms.

Dickerson said the normal level of dust in the air is anywhere from 20 to 70 micrograms per cubic meter. Thursday's 24-hour average for Phoenix reached nearly 160 micrograms per cubic meter. That figure was just slightly above what federal standards deem healthy.

Dr. Art Mollen, who operates a family medicine practice in Scottsdale, Ariz., said there were twice as many patients as usual in his waiting r oom at the start of work Friday. People came in with asthma flare-ups, sinus inflammation, opthalmological migraines and other problems.

"We have been inordinately busy today because of the dust storm," Mollen said, noting also that since early July he has seen more patients with allergy problems, even though Arizona's allergy season happens in the spring and fall.

Mollen also said he expects to see more cases of valley fever, a fungal pneumonia that thrives in the hot, arid Southwest in dirt found just a few feet beneath the earth's surface. It can be stirred up by construction, wind or other activities.

Meteorologists also were trying to determine whether microbursts caused storm damage in metro Phoenix and neighboring Pinal County.

Power lines landed on top of several cars and one elementary school bus in Pinal County, just south of metro Phoenix. County spokesman Elias Johnson said there were no reported injuries and everyone got out safely, including the four students on the bus.

Some incoming and departing flights at Phoenix Sky Harbor International Airport were delayed about 40 minutes because of the storm. Take-offs and landings resumed after the storm

subsided.

One utility, the Salt River Project, said at the peak of the storm 3,500 of its customers were without electricity, mostly in the Queen Creek, Ariz., area southeast of Phoenix, but power had been restored to nearly everyone within about five hours of the storm's arrival.

Authorities in Pinal County were assessing damage in the city of Eloy, Ariz., where homes were damaged, roofs were torn off businesses and a junior high school has part of its roof missing.Exceptional Event, Phoenix, August 18, 2011 Appendix B



### KTVK-TV re ports that elsewhere in Eloy, tr ees landed on top of homes and winds sheared off

the roof of a business in the downtown area.

A dust storm moves to consume Camelback Mountain in Phoenix Aug. 18, 2011. / AP Photo/The Arizona RepublicExceptional Event, Phoenix, August 18, 2011 Appendix B



### http://www.reuters.com/article/2011/08/19/us-weather-phoenix-duststormidUSTRE77I0P620110819

Billowing dust storm engulfs downtown Phoenix

Fri Aug 19, 2011 9:30am EDT

PHOENIX

(Reuters) - A billowing wall of dust engulfed downtown Phoenix on Thursday, cutting visibility to a few hundred yards and delaying flights at the international airport, authorities and news reports said.

Driving rains and winds gusting at nearly 60 miles per hour also buffeted San Tan Valley, southeast of Phoenix in the early evening, according to the National Weather Service.

Roaring gusts downed trees and power lines in Pinal County, trapping drivers in their cars and preventing commuters from reaching their homes south of the state capital.

"This storm hit during a very busy time for traffic, bringing down power lines over several miles on top of cars with visibility near zero," Pinal County Sheriff's Office spokesman Elias Johnson

said in a statement.

Deputies "will keep residents out until we can determine their safety is no longer at risk," he

added.

The dust storm prevented planes from taking off or landing at Phoenix Sky Harbor International Airport for about 40 minutes, The Arizona Republic newspaper reported.

A call to the airport seeking confirmation of the delays was not immediately returned on Thursday.

In early July, a huge sand storm -- dubbed a haboob -- swallowed the Phoenix valley, darkening the streets, sending residents scrambling for cover and cutting power to thousands of homes.

Weather experts say haboobs frequently occur during the swelteringly hot summer monsoon

season in the southwest United States.

(Reporting by Tim Gaynor; Editing by Cynthia Johnston)Exceptional Event, Phoenix, August 18, 2011 Appendix B



### Pedestrians wait for a transit bus along Indian School Road during a dust storm in Phoenix, Arizona August 18, 2011. Credit: REUTERS/Joshua Lott.

A dust storm surrounds high rise buildings in Phoenix, Arizona August 18, 2011. Credit:

REUTERS/Joshua Lott.Exceptional Event, Phoenix, August 18, 2011 Appendix B



### A pedestrian walks along Indian School Road during a dust storm in Phoenix, Arizona August 18, 2011. Credit: REUTERS/Joshua Lott.

A pedestrian crosses Central Avenue during a dust storm in Phoenix, Arizona August 18, 2011.

Credit: REUTERS/Joshua Lott.Exceptional Event, Phoenix, August 18, 2011 Appendix B



### A dust storm surrounds high rise buildings in Phoenix, Arizona August 18, 2011. Credit:

REUTERS/Joshua Lott.Exceptional Event, Phoenix, August 18, 2011 Appendix B



### http://www.npr.org/blogs/thetwo-way/2011/08/19/139780992/video-third-haboob-of-summercovers-phoenix-in-sand-and-dust (follow the link to see the video)

VIDEO: Third Haboob Of Summer Covers Phoenix In Sand And Dust



## by Mark Memmott

August 19, 2011 9:15 AM

The area around Phoenix was hit by its third "ha boob" of the summer last evening, as strong winds sent a huge cloud of sand and dust rolling over the area.

The Arizona Republic says that "blowing dust blanketed much of the Valley ... reducing visibility to less than a quarter-mile."

As during previous dust storms, news outlets in Phoenix caught much of the action and have posted video. Here's one from the Republic.

By the way, "haboob" is the word they've been using in Arizona and in meteorological circles for many years, the Republic reports. As Merriam-Webster says, it's Arabic in origin and means "a violent dust storm or sandstorm especially of Sudan."Exceptional Event, Phoenix, August 18, 2011 Appendix B



### http://news.nationalgeographic.com/news/2011/08/pictures/110819-haboob-dust-storm-phoenixarizona-lightning-science/#/haboob-hits-phoenix-dust-storm-lightning_39333_600x450.jpg

Pictures: Huge Dust Storm Swallows Phoenix

Flash in a Haboob

Published August 19, 2011

AP

A flash of lightning accentuates a thick blanket of dust over Gilbert, Arizona, on Thursday—the third major dust storm to hit the Phoenix metropolitan area (map) since early July.

The billowing cloud of dust was about a half mile (0.8 kilometer) high and 50 to 55 miles (80 to 88 kilometers) wide. The storm rolled across Arizona's Pinal County last night with winds reaching 30 to 40 miles (48 to 64 kilometers) an hour, the Arizona Republic reported.

Dust storms are relatively common between June and September in parts of the U.S. Southwest. Severe dust storms are also called haboobs—Arabic for "violent wind"—since they often appear in northern Africa and the Middle East. (See a picture of a haboob in western Iraq.)

Photos below are credited to Matt York/AP.Exceptional Event, Phoenix, August 18, 2011 Appendix BExceptional Event, Phoenix, August 18, 2011 Appendix BExceptional Event, Phoenix, August 18, 2011 Appendix BExceptional Event, Phoenix, August 18, 2011 Appendix C



# Appendix C: Historical Fluctuation Time-Series Graphs

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



### Date Buckeye 5-Year Historical Fluctuation - 24 Hour Averages

August 18, 2011



### Figure C-1. Twenty-four--hour average PM 10 

### concentrations at the Buckeye monitor (2007–2011). The 24-hr average PM 10 

### concentration on August 18, 2011, is shown in red and highlighted by the arrow.Exceptional Event, Phoenix, August 18, 2011 Appendix C

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

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

August 18, 2011



### Figure C-2. Twenty-four-hour average PM 10 

### concentrations at the West Chandler monitor (2007–2011). The 24-hr average PM 10 

### concentration on August 18, 2011, is shown in red and highlighted by the arrow.

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



### Date South Phoenix 5-Year Historical Fluctuation - 24 Hour Averages

August 18, 2011



### Figure C-3. Twenty-four-hour average PM 10 

### concentrations at the South Phoenix monitor (2007–2011). The 24-hr average PM 10 

### concentration on August 18, 2011, is shown in red and highlighted by the arrow.Exceptional Event, Phoenix, August 18, 2011 Appendix D



# Appendix D:
ADEQ and NWS Forecast Products

MARICOPA COUNTY DUST CONTROL FORECAST

ISSUED WEDNESDAY, AUGUST 17, 2011

Five-day weather outlook:

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

POSSIBLE EVEN FROM DISTANT THUNDERSTORMS

Active summer monsoon weather will continue over or in the vicinity of the Phoenix me tro area thru Friday followed by a brief lull as dry westerly winds aloft occur. Moisture will be on the increas e again by Monday. As a result, thunderstorm outflow boundaries from even distant thunderstorms will pose a risk for periods of dense blowing dust and unhealthy PM-10 levels thru Friday and again on Monday.



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

WINDS STAGNATION UNHEALTHY PM-10

RISK LEVEL

Day 1: Thu 08/18/2011 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: Fri 08/19/2011 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: Sat 08/20/2011 Southwest to westerly 10-20 mph during the

afternoon. No significant + stagnation expected. = LOW

EXTENDED OUTLOOK

Day 4: Sun 08/21/2011 Southwest to westerly 10-20 mph during the

afternoon. No significant + stagnation expected. = LOW

Day 5: Mon 08/22/2011 Southwest to westerly 10-20 mph during the afternoon except strong and gusty due to

outflow from

thunderstorms. No significant

+ stagnation expected. = MODERATEExceptional Event, Phoenix, August 18, 2011 Appendix D

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 04/28/2011Exceptional Event, Phoenix, August 18, 2011 Appendix D

VERY UNHEALTHY (201-300)

UNHEALTHY (151-200)

UNHEALTHY FOR SENSITIVE GROUPS (101-150)

MODERATE (51-100)

GOOD (0-50)

For more information visit: http://www.airnow.gov/index.cfm?action=aqibasics.aqi

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

## AIR QUALITY FORECAST FOR THURSDAY, AUGUST 18, 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

TUE 08/16/2011

DUST

Highest AQI Reading/Site

(Preliminary data only) 

### TODAY

WED 08/17/2011

DUST 

### TOMORROW

THU 08/18/2011

DUST 

### EXTENDED

FRI 08/19/2011

DUST



## O3* 58

QUEEN VALLEY 

### 84

MODERATE 

### 80

MODERATE 

### 77

MODERATE



## CO* 05

GREENWOOD 

### 06

GOOD 

### 07

GOOD 

### 06

GOOD



## PM-10* 60

SOUTH PHOENIX 

### 75

MODERATE 

### 75

MODERATE 

### 75

MODERATE



## PM-2.5* 33

GLENDALE 

### 28

GOOD 

### 34

GOOD 

### 31

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.

“ 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.Exceptional Event, Phoenix, August 18, 2011 Appendix D

“ DUST ” means that short periods of high PM-10 concentrati ons caused by outflow from thunderstorms are possible.Exceptional Event, Phoenix, August 18, 2011 Appendix D

Health message for Wednesday, August 17: Unusually sensitive people should consider reducing prolonged or heavy exertion outdoors.

Health message for Thursday, August 18: Unusually sensitive people should consider reducing prolonged or heavy exertion outdoors.



### Synopsis and Discussion

OZONE: Considerable cloud cover held local ozone levels dow n on Tuesday but today is starting out under mostly sunny skies. This, along with rather subdued gradient winds, should support high est ozone concentrations reaching the upper moderate range of the Air Quality I ndex. Winds aloft are now being advertis ed to become westerly thru a deep layer by Thursday morning. Since this component aligns with the typical upslope flow this time of year, higher

afternoon winds are forecast to resume tomorrow and continue thru the weekend. This situation usually means that highest ozone levels will occur over the far eastern Valley a nd at this time are forecast to be in the mid-moderate range of the AQI.

PARTICLES: Another outflow boundary from thunders torm activity impacted parts of the Valley Tuesday evening with wind gusts as strong as 36 mph and reductions in visibilities to as low as two miles in bl owing dust. This contributed to a max hourly PM-10 concentration of 591.2ug/m3 at the Higley monitoring si te at 8:00 p.m. Active

summer monsoon weather will continue over or in the vicinity of the Phoenix metro area thru Friday followed by a brief lull as dry westerly winds aloft occur. Moisture will be on the increase again by Monday. As a result,

thunderstorm outflow boundaries from even distant thunderstorms will continue to pose a risk for periods of dense blowing dust and unhealthy PM-10 le vels the next few evenings.

MONITORING SITE MAPS: STATIC MAP

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

IN TERACTIVE MAPS - http://aqwww.maricopa.gov/AirM onit oring/SitePollutionMap.aspx http://www.airnow.gov /



### POLLUTION MONITOR READINGS FOR TUESDAY, AUGUST 16, 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) 44 37

Apache Junction (Pinal County) 61 54

Blue Point 59 50

Buckeye 34 29

Casa Grande (Pinal County) 44 37

Cave Creek 49 42

Central Phoenix 44 37

Dysart 38 32

Falcon Field 53 45

Fountain Hills 60 51

Glendale 45 38

Humboldt Mountain 49 42

North Phoenix 51 43

Phoenix Supersite 48 41

Pinal Air Park (Pinal County) 47 40

Pinnacle Peak 55 47

Queen Valley (Pinal County) 62 58

Rio Verde 56 47

South Phoenix 43 36

South Scottsdale 52 44

Tempe 42 36

Tonto Nat’l Mon. (Gila County) 52 44

West Chandler 52 44

West Phoenix 44 37

Yuma (Yuma County) 35 30Exceptional Event, Phoenix, August 18, 2011 Appendix D



## CO (CARBON MONOXIDE)

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

Central Phoenix 0.1 01

Greenwood 0.4 05

Phoenix Supersite NOT AVBL NOT AVBL NOT AVBL

West Phoenix 0.2 02 

## PM-10 (PARTICLES)

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

Buckeye 39 36

Central Phoenix 38 35

Combs School(Pinal County 76 61

Durango 51 47

Dysart 32 30

Glendale 54 50

Greenwood 37 34

Higley 61 54

Maricopa (Pinal County) 62 54

Phoenix Supersite 33 31

South Phoenix 73 60

West Chandler 49 45

West Forty Third 66 56

West Phoenix 46 43

Zuni Hills 36 33 

## 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 8.2 27

Dysart 6.4 21

Estrella Mountain Park 4.3 14

Glendale 10.1 33

Phoenix Supersite 6.8 22

South Phoenix 6.6 21

Vehicle Emissions Lab 5.5 18

West Phoenix 8.3 27Exceptional Event, Phoenix, August 18, 2011 Appendix D



### Statements, Advisories, and Warnings issued b y the National Weather Service office in Phoenix, AZ, pertaining to the August 18, 2011, dust storm event:

URGENT - WEATHER MESSAGE

NATIONAL WEATHER SERVICE PHOENIX AZ

444 PM MST THU AUG 18 2011

AZZ023-027-190100-

/O.EXA.KPSR.DS.W.0013.000000T0000Z-110819T0100Z/

/O.CON.KPSR.EH.W.0007.000000T0000Z-110819T0300Z/

GREATER PHOENIX AREA-SOUTHWEST MARICOPA COUNTYINCLUDING THE CITIES OF...BUCKEYE...MESA...PHOENIX...GILA BEND

444 PM MST THU AUG 18 2011

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

...EXCESSIVE HEAT WARNING REMAINS IN EFFECT UNTIL 8 PM MST THIS

EVENING...

THE NATIONAL WEATHER SERVICE IN PHOENIX HAS ISSUED A DUST STORM

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

EXCESSIVE HEAT WARNING REMAINS IN EFFECT UNTIL 8 PM MST THIS

EVENING.

* AFFECTED AREA: SOUTHWEST AND CENTRAL MARICOPA COUNTY.

* LOCATIONS INCLUDE: GILA BEND...BUCKEYE...MESA...PHOENIX

* VISIBILITY: LESS THAN ONE QUARTER MILE DUE TO BLOWING DUST.

* IMPACTS: SUDDEN REDUCTION IN VISIBILITY DUE TO BLOWING DUST CAN BE

VERY HAZARDOUS...ESPECIALLY TO MOTORISTS. EXCESSIVELY HOT

TEMPERATURES CAN BE STRESSFUL TO HUMANS AND ANIMALS.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

A DUST STORM WARNING IS ISSUED WHEN WINDS HAVE GENERATED LARGE

AREAS OF BLOWING DUST OR BLOWING SAND THAT HAVE SUBSTANTIALLY

REDUCED VISIBILITIES...TO 1/4 MILE OR LESS...RESULTING IN

HAZARDOUS DRIVING CONDITIONS IN SOME AREAS. BE READY FOR A SUDDEN

DROP IN VISIBILITY TO NEAR ZERO. USE EXTRA CAUTION AND SLOW DOWN

WHILE DRIVING...AS OBJECTS ON AND NEAR ROADWAYS WILL BE SEEN ONLY

AT CLOSE RANGE. IF YOU ENCOUNTER BLOWING DUST OR BLOWING SAND ON

THE ROADWAY OR SEE IT APPROACHING...PULL OFF THE ROAD AS FAR AS

POSSIBLE AND PUT YOUR VEHICLE IN PARK. TURN THE LIGHTS ALL THE

WAY OFF AND KEEP YOUR FOOT OFF THE BRAKE PEDAL.

BULLETIN - EAS ACTIVATION REQUESTED

SEVERE THUNDERSTORM WARNING

NATIONAL WEATHER SERVICE PHOENIX AZ

454 PM MST THU AUG 18 2011

THE NATIONAL WEATHER SERVICE IN PHOENIX HAS ISSUED A

* SEVERE THUNDERSTORM WARNING FOR...

EAST CENTRAL MARICOPA COUNTY IN SOUTH CENTRAL ARIZONA...

CENTRAL PINAL COUNTY IN SOUTH CENTRAL ARIZONA...

* UNTIL 545 PM MST

* AT 446 PM MST...NATIONAL WEATHER SERVICE METEOROLOGISTS DETECTED

SEVERE THUNDERSTORMS CAPABLE OF PRODUCING DAMAGING WINDS IN

EXCESS OF 60 MPH. IN ADDITION...DENSE BLOWING DUST MAY ACCOMPANY

THESE STORMS. THESE STORMS WERE LOCATED 14 MILES EAST OF

MAGMA...OR 6 MILES SOUTHEAST OF FLORENCE JUNCTION...AND WERE NEAR

STATIONARY.

* OTHER LOCATIONS IN THE WARNING INCLUDE BUT ARE NOT LIMITED TO

SANTAN AND SACATON

PRECAUTIONARY/PREPAREDNESS ACTIONS...

THIS IS A DANGEROUS STORM. IF YOU ARE IN ITS PATH...PREPARE

IMMEDIATELY FOR DAMAGING WINDS AND DEADLY CLOUD TO GROUND LIGHTNING.Exceptional Event, Phoenix, August 18, 2011 Appendix D



### MOVE TO SHELTER INSIDE A STRONG BUILDING. STAY AWAY FROM WINDOWS.

SEVERE WEATHER STATEMENT

NATIONAL WEATHER SERVICE PHOENIX AZ

520 PM MST THU AUG 18 2011

AZC013-021-190045-

/O.CON.KPSR.SV.W.0032.000000T0000Z-110819T0045Z/

PINAL AZ-MARICOPA AZ520 PM MST THU AUG 18 2011

...A SEVERE THUNDERSTORM WARNING REMAINS IN EFFECT UNTIL 545 PM MST

FOR EAST CENTRAL MARICOPA AND CENTRAL PINAL COUNTIES...

AT 510 PM MST...NATIONAL WEATHER SERVICE METEOROLOGISTS DETECTED TWO

SEVERE THUNDERSTORMS IN THE WARNED AREA. SEVERE THUNDERSTORMS WERE

LOCATED SOUTHEAST OF SUN LAKES AND SOUTHEAST OF SAN TAN VALLEY. BOTH

STORMS WERE NEAR STATIONARY AND WERE PRODUCING STRONG OUTFLOW FINDS

IN EXCESS OF 60 MPH. OUTFLOW BOUNDARIES FROM THESE STORMS ARE ALSO

GENERATING AREAS OF BLOWING DUST.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

THESE ARE DANGEROUS STORMS. INDIVIDUALS IN THE VICINITY SHOULD TAKE

COVE INDOORS.

REPORT SEVERE WEATHER TO THE NEAREST LAW ENFORCEMENT AGENCY. THEY

WILL RELAY YOUR REPORT TO THE NATIONAL WEATHER SERVICE FORECAST

OFFICE.

GREATER PHOENIX AREA-SOUTHWEST MARICOPA COUNTYNORTHWEST AND NORTH CENTRAL PINAL COUNTYINCLUDING THE CITIES OF...BUCKEYE...MESA...PHOENIX...GILA BEND...

APACHE JUNCTION...CASA GRANDE...FLORENCE

544 PM MST THU AUG 18 2011

...EXCESSIVE HEAT WARNING REMAINS IN EFFECT UNTIL 8 PM MST THIS

EVENING...

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

EVENING...

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

EXCESSIVE HEAT WARNING REMAINS IN EFFECT UNTIL 8 PM MST THIS EVENING.

* AT 540 PM...THE LEADING EDGE OF GUSTY SOUTH TO SOUTHEAST WINDS 25

TO 40 MPH HAD REACHED THE SOUTHEAST VALLEY. A DUST STORM...WITH

VISIBILITY LESS THAN ONE QUARTER MILE AT TIMES...ACCOMPANIED THE

GUSTY WINDS. THE GUST FRONT AND AREAS OF DENSE BLOWING DUST WILL

PUSH TOWARD THE NORTH AND WEST...AND AFFECT MUCH OF THE CENTRAL AND

SOUTHEAST PORTION OF THE GREATER PHOENIX METROPOLITAN AREA BY 6 PM.

* AFFECTED AREA: SOUTHWEST AND CENTRAL MARICOPA COUNTY.

* LOCATIONS INCLUDE:

MESA...CHANDLER...PHOENIX...GILBERT...TEMPE...QUEEN CREEK...SCOTTSDALE

* VISIBILITY: LESS THAN ONE QUARTER MILE DUE TO BLOWING DUST.

* IMPACTS: SUDDEN REDUCTION IN VISIBILITY DUE TO BLOWING DUST

CAN BE VERY HAZARDOUS...ESPECIALLY TO MOTORISTS. EXCESSIVELY

HOT TEMPERATURES CAN BE STRESSFUL TO HUMANS AND ANIMALS.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

A DUST STORM WARNING IS ISSUED WHEN WINDS HAVE GENERATED LARGE

AREAS OF BLOWING DUST OR BLOWING SAND THAT HAVE SUBSTANTIALLY

REDUCED VISIBILITIES...TO 1/4 MILE OR LESS...RESULTING IN

HAZARDOUS DRIVING CONDITIONS IN SOME AREAS. BE READY FOR A SUDDEN

DROP IN VISIBILITY TO NEAR ZERO. USE EXTRA CAUTION AND SLOW DOWN

WHILE DRIVING...AS OBJECTS ON AND NEAR ROADWAYS WILL BE SEEN ONLY

AT CLOSE RANGE. IF YOU ENCOUNTER BLOWING DUST OR BLOWING SAND ON

THE ROADWAY OR SEE IT APPROACHING...PULL OFF THE ROAD AS FAR AS

POSSIBLE AND PUT YOUR VEHICLE IN PARK. TURN THE LIGHTS ALL THE

WAY OFF AND KEEP YOUR FOOT OFF THE BRAKE PEDAL.Exceptional Event, Phoenix, August 18, 2011 Appendix D



### AIRPORT WEATHER WARNING FOR SKY HARBOR AIRPORT

NATIONAL WEATHER SERVICE PHOENIX AZ

553 PM MST THU AUG 18 2011

...AIRPORT WEATHER WARNING FOR SKY HARBOR AIRPORT IN EFFECT UNTIL

745 PM MST...

THE NATIONAL WEATHER SERVICE IN PHOENIX HAS ISSUED AN AIRPORT WEATHER

WARNING FOR SKY HARBOR AIRPORT FOR STRONG GUSTY WINDS.

THUNDERSTORM WIND GUSTS BETWEEN 36 AND 40 KNOTS FROM THE SOUTHEAST.

VISIBILITY 1/4 MILE IN BLOWING DUST AT TIMES.

URGENT - WEATHER MESSAGE...UPDATED

NATIONAL WEATHER SERVICE PHOENIX AZ

600 PM MST THU AUG 18 2011

AZZ027-028-190300-

/O.EXP.KPSR.DS.W.0013.000000T0000Z-110819T0100Z/

/O.CON.KPSR.EH.W.0007.000000T0000Z-110819T0300Z/

SOUTHWEST MARICOPA COUNTYNORTHWEST AND NORTH CENTRAL PINAL COUNTYINCLUDING THE CITIES OF...GILA BEND...APACHE JUNCTION...

CASA GRANDE...FLORENCE

600 PM MST THU AUG 18 2011

...EXCESSIVE HEAT WARNING REMAINS IN EFFECT UNTIL 8 PM MST THIS

EVENING...

...DUST STORM WARNING WILL EXPIRE AT 6 PM MST THIS EVENING...

THE DUST STORM WARNING WILL EXPIRE AT 6 PM MST THIS EVENING. AN

EXCESSIVE HEAT WARNING REMAINS IN EFFECT UNTIL 8 PM MST THIS

EVENING.

* GUSTY WINDS WITH BLOWING DUST WILL PERSIST ACROSS PORTIONS OF

SOUTHWEST MARICOPA COUNTY AS WELL AS NORTHWEST AND NORTH-CENTRAL

PINAL COUNTY THROUGH 7 PM. VISIBILITY WILL GENERALLY BE AT AND

ABOVE 1 MILE WITH THE DUST WHILE WINDS GRADUALLY DIMINISH.

* AFFECTED AREA: SOUTHWEST AND CENTRAL MARICOPA COUNTY.

* LOCATIONS INCLUDE: CASA GRANDE...GILA BEND
* VISIBILITY: LESS THAN ONE QUARTER MILE DUE TO BLOWING DUST UNTIL 6

PM...WITH IMPROVING VISIBILITY THEREAFTER.

* IMPACTS: SUDDEN REDUCTION IN VISIBILITY DUE TO BLOWING DUST

CAN BE VERY HAZARDOUS...ESPECIALLY TO MOTORISTS. EXCESSIVELY

HOT TEMPERATURES CAN BE STRESSFUL TO HUMANS AND ANIMALS.

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

600 PM MST THU AUG 18 2011

...DUST STORM WARNING NOW IN EFFECT UNTIL 8 PM MST THIS

EVENING...

...EXCESSIVE HEAT WARNING REMAINS IN EFFECT UNTIL 8 PM MST THIS

EVENING...

THE DUST STORM WARNING IS NOW IN EFFECT UNTIL 8 PM MST THIS

EVENING. AN EXCESSIVE HEAT WARNING REMAINS IN EFFECT UNTIL 8 PM

MST THIS EVENING.

* AT 555PM...THE LEADING EDGE OF GUSTY SOUTH TO SOUTHEAST WINDS 25 TO

35 MPH HAD REACHED THE SOUTHEAST VALLEY...AND EXTENDED FROM SKY

HARBOR AIRPORT TO DOWNTOWN SCOTTSDALE. A DUST STORM...WITH

VISIBILITY LESS THAN ONE QUARTER MILE AT TIMES...ACCOMPANIED THE

GUSTY WINDS. THE GUST FRONT AND AREAS OF DENSE BLOWING DUST WILL

PUSH TOWARD THE NORTH AND WEST...AND AFFECT MUCH OF THE GREATER

PHOENIX METROPOLITAN AREA BETWEEN 6 PM AND 8 PM. WIND SHOULD SLOWLY

DECREASE WITH TIME...AND VISIBILITY WILL SLOWLY IMPROVE.

* AFFECTED AREA: SOUTHWEST AND CENTRAL MARICOPA COUNTY.Exceptional Event, Phoenix, August 18, 2011 Appendix D



### * LOCATIONS INCLUDE: MESA...CHANDLER...PHOENIX...GILBERT...

TEMPE...QUEEN CREEK...SCOTTSDALE...PARADISE VALLEY

* VISIBILITY: LESS THAN ONE QUARTER MILE DUE TO BLOWING DUST.

* IMPACTS: SUDDEN REDUCTION IN VISIBILITY DUE TO BLOWING DUST

CAN BE VERY HAZARDOUS...ESPECIALLY TO MOTORISTS. EXCESSIVELY

HOT TEMPERATURES CAN BE STRESSFUL TO HUMANS AND ANIMALS.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

A DUST STORM WARNING IS ISSUED WHEN WINDS HAVE GENERATED LARGE

AREAS OF BLOWING DUST OR BLOWING SAND THAT HAVE SUBSTANTIALLY

REDUCED VISIBILITIES...TO 1/4 MILE OR LESS...RESULTING IN

HAZARDOUS DRIVING CONDITIONS IN SOME AREAS. BE READY FOR A SUDDEN

DROP IN VISIBILITY TO NEAR ZERO. USE EXTRA CAUTION AND SLOW DOWN

WHILE DRIVING...AS OBJECTS ON AND NEAR ROADWAYS WILL BE SEEN ONLY

AT CLOSE RANGE. IF YOU ENCOUNTER BLOWING DUST OR BLOWING SAND ON

THE ROADWAY OR SEE IT APPROACHING...PULL OFF THE ROAD AS FAR AS

POSSIBLE AND PUT YOUR VEHICLE IN PARK. TURN THE LIGHTS ALL THE

WAY OFF AND KEEP YOUR FOOT OFF THE BRAKE PEDAL.

BULLETIN - EAS ACTIVATION REQUESTED

SEVERE THUNDERSTORM WARNING

NATIONAL WEATHER SERVICE PHOENIX AZ

612 PM MST THU AUG 18 2011

THE NATIONAL WEATHER SERVICE IN PHOENIX HAS ISSUED A

* SEVERE THUNDERSTORM WARNING FOR...

CENTRAL MARICOPA COUNTY IN SOUTH CENTRAL ARIZONA...

THIS INCLUDES THE CITIES OF...YOUNGTOWN...SURPRISE...SUN CITY

WEST...SUN CITY...PEORIA...EL MIRAGE...

* UNTIL 700 PM MST

* AT 606 PM MST...NATIONAL WEATHER SERVICE METEOROLOGISTS DETECTED

SEVERE THUNDERSTORMS CAPABLE OF PRODUCING DAMAGING WINDS IN

EXCESS OF 60 MPH. THESE STORMS WERE LOCATED NEAR PEORIA...AND

MOVING SOUTHEAST AT 5 MPH.

* THE SEVERE THUNDERSTORM WILL OTHERWISE REMAIN OVER MAINLY RURAL

AREAS OF THE INDICATED COUNTY.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

THESE ARE DANGEROUS STORMS. SEEK SHELTER NOW INSIDE A STURDY

STRUCTURE AND STAY AWAY FROM WINDOWS!

IF YOU ENCOUNTER DENSE BLOWING DUST WHILE DRIVING...PULL OVER AS FAR

OFF THE ROADWAY AS POSSIBLE AND PARK. TURN OFF YOUR HEADLIGHTS AND

KEEP YOUR FOOT OFF THE BRAKE.

SEVERE WEATHER STATEMENT

NATIONAL WEATHER SERVICE PHOENIX AZ

640 PM MST THU AUG 18 2011

AZC013-190200-

/O.CON.KPSR.SV.W.0033.000000T0000Z-110819T0200Z/

MARICOPA AZ640 PM MST THU AUG 18 2011

...A SEVERE THUNDERSTORM WARNING REMAINS IN EFFECT UNTIL 700 PM MST

FOR CENTRAL MARICOPA COUNTY...

AT 634 PM MST...NATIONAL WEATHER SERVICE METEOROLOGISTS CONTINUED TO

DETECT SEVERE THUNDERSTORMS CAPABLE OF PRODUCING DAMAGING WINDS IN

EXCESS OF 60 MPH. THESE STORMS WERE LOCATED NEAR PEORIA AND WERE

NEAR STATIONARY.

THE SEVERE THUNDERSTORM WILL OTHERWISE REMAIN OVER MAINLY RURAL AREAS

OF THE INDICATED COUNTY.

THE STORMS HAVE WEAKENED...BURT WILL LIKELY REINTENSIFY AS THEY

INTERSECT AN OUTFLOW BOUNDARY APPROACHING FROM THE EAST.

PRECAUTIONARY/PREPAREDNESS ACTIONS...Exceptional Event, Phoenix, August 18, 2011 Appendix D



### IF YOU ARE IN THE WARNING AREA...GO INSIDE A STURDY BUILDING.

REMEMBER...A SEVERE THUNDERSTORM WILL PRODUCE DAMAGING WINDS AND

DEADLY LIGHTNING

REPORT SEVERE WEATHER TO THE NEAREST LAW ENFORCEMENT AGENCY. THEY

WILL RELAY YOUR REPORT TO THE NATIONAL WEATHER SERVICE FORECAST

OFFICE.

URGENT - WEATHER MESSAGE...UPDATED

NATIONAL WEATHER SERVICE PHOENIX AZ

719 PM MST THU AUG 18 2011

AZZ023-190330-

/O.CAN.KPSR.EH.W.0007.000000T0000Z-110819T0300Z/

/O.CON.KPSR.DS.W.0013.000000T0000Z-110819T0300Z/

GREATER PHOENIX AREAINCLUDING THE CITIES OF...MESA...PHOENIX...SCOTTSDALE...PEORIA |

719 PM MST THU AUG 18 2011

...DUST STORM WARNING REMAINS IN EFFECT UNTIL 8 PM MST THIS

EVENING...

...EXCESSIVE HEAT WARNING IS CANCELLED...

THE NATIONAL WEATHER SERVICE IN PHOENIX HAS CANCELLED THE

EXCESSIVE HEAT WARNING. A DUST STORM WARNING REMAINS IN EFFECT

UNTIL 8 PM MST THIS EVENING...MAINLY FOR THE NORTH AND WEST PORTION

OF THE GREATER PHOENIX AREA.

* AT 715PM...THE LEADING EDGE OF GUSTY SOUTH TO SOUTHEAST WINDS 25 TO

40 MPH HAD REACHED THE NORTH VALLEY. BETWEEN 630 AND 650 PM...DEER

VALLEY AIRPORT REPORTED A PEAK GUST OF 44 MPH...WHILE SCOTTSDALE

AIRPORT REPORTED A PEAK GUST OF 40 MPH. A DUST STORM..WITH

VISIBILITY OCCASIONALLY LESS THAN ONE QUARTER MILE...ACCOMPANIED

THE LEADING EDGE OF THE GUSTY WINDS. THE GUST FRONT WILL PUSH WEST

ACROSS MUCH OF THE WEST VALLEY...WITH LOCALIZED AREAS OF DENSE

BLOWING DUST POSSIBLE. VISIBILITY HAS IMPROVED OVER CENTRAL AND

SOUTHEAST PORTIONS OF THE GREATER PHOENIX AREA...THOUGH DUSTY

CONDITIONS PERSIST.

* AFFECTED AREA: CENTRAL AND NORTH-CENTRAL MARICOPA COUNTY.

* LOCATIONS INCLUDE: MESA...CHANDLER...PHOENIX...GILBERT...

TEMPE...QUEEN CREEK...SCOTTSDALE...PARADISE VALLEY

* VISIBILITY: OCCASIONALLY LESS THAN ONE QUARTER MILE DUE TO BLOWING

DUST...WITH WIDESPREAD VISIBILITY LESS THAN 2 MILES.

* IMPACTS: SUDDEN REDUCTION IN VISIBILITY DUE TO BLOWING DUST CAN BE

VERY HAZARDOUS...ESPECIALLY TO MOTORISTS.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

A DUST STORM WARNING IS ISSUED WHEN WINDS HAVE GENERATED LARGE AREAS

OF BLOWING DUST OR BLOWING SAND THAT HAVE SUBSTANTIALLY REDUCED

VISIBILITIES...TO 1/4 MILE OR LESS...RESULTING IN HAZARDOUS DRIVING

CONDITIONS IN SOME AREAS. BE READY FOR A SUDDEN DROP IN VISIBILITY TO

NEAR ZERO. USE EXTRA CAUTION AND SLOW DOWN WHILE DRIVING...AS OBJECTS

ON AND NEAR ROADWAYS WILL BE SEEN ONLY AT CLOSE RANGE. IF YOU

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

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

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

OFF THE BRAKE PEDAL.

URGENT - WEATHER MESSAGE...UPDATED

NATIONAL WEATHER SERVICE PHOENIX AZ

755 PM MST THU AUG 18 2011

AZZ023-190400-

/O.EXP.KPSR.DS.W.0013.000000T0000Z-110819T0300Z/

GREATER PHOENIX AREA-Exceptional Event, Phoenix, August 18, 2011 Appendix D



### INCLUDING THE CITIES OF...MESA...PHOENIX

755 PM MST THU AUG 18 2011

...DUST STORM WARNING WILL EXPIRE AT 8 PM MST THIS EVENING...

THE DUST STORM WARNING WILL EXPIRE AT 8 PM MST THIS EVENING. WINDY

CONDITIONS WILL PERSIST THROUGH MUCH OF THE EVENING...BUT VISIBILITY

HAS IMPROVED NOTICEABLY AT MOST LOCATIONS. THEREFORE...THE DUST STORM

WARNING WILL BE ALLOWED TO EXPIRE AT 8 PM. ISOLATED THUNDERSTORMS

OVER THE NORTH VALLEY COULD GENERATE LOCALIZED AREAS OF DENSE BLOWING

DUST THROUGH 9 PM...BUT VISIBILITY RESTRICTION DUE TO BLOWING DUST IS

NOT EXPECTED TO LOWER TO ONE QUARTER MILE.

* AFFECTED AREA: CENTRAL AND NORTH-CENTRAL MARICOPA COUNTY

* LOCATIONS INCLUDE: PHOENIX...PEORIA...GLENDALE...SCOTTSDALE

* WINDS: SOUTHEAST 20 TO 35 MPH...WITH LOCALLY STRONGER GUSTS.

* VISIBILITY: OCCASIONALLY BELOW 4 MILES DUE TO BLOWING DUST OVER THE

WEST AND NORTH VALLEY THROUGH 9 PM.

* IMPACTS: THE AIR IS STILL RATHER DUSTY...WHICH COULD POSE A PROBLEM FOR PEOPLE WITH RESPIRATORY PROBLEMS.|

$$

NATIONAL WEATHER SERVICE PHOENIX IS ON THE INTERNET AT

WEATHER.GOV/PHOENIXExceptional Event, Phoenix, August 18, 2011 Appendix E



# Appendix E:

Affidavit of Public Notice