# State of Arizona

Exceptional Event Documentation

for the Event of July 11, 2012,

for the Phoenix PM 10 

# Nonattainment Area

Final Report Prepared for

Arizona Department of Environmental Quality

Phoenix, AZ

February 2013

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

# State of Arizona

Exceptional Event Documentation

for the Event of July 11, 2012,

for the Phoenix PM 10 

# Nonattainment Area

Final Report

STI-912095-5568-FR



# Prepared by

Daniel Alrick

Angela Ekstrand

Briana Gordon

Hilary Hafner

Clinton MacDonald

Hilary Minor

Ashley Russell

Sonoma Technology, Inc.

1455 N. McDowell Blvd., Suite D

Petaluma, CA 94954-6503

Ph 707.665.9900 | F 707.665.9800

sonomatech.com



# Prepared for

Theresa Rigney

Air Quality Assessment Section Manager

1110 W. Washington Street

Phoenix, AZ 85007

602.771.2274

February 13, 2013

Cover image illustrates windblown dust and haze with reduced visibility in the Phoenix area at 2245 LST on July 11,

2012. This photo was taken by an ADEQ visibility camera near downtown Phoenix looking northeast toward

Camelback Mountain.

## Exceptional Event, Phoenix, July 11, 2012 Acknowledgments



# Acknowledgments

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

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

iii

## Exceptional Event, Phoenix, July 11, 2012 Table of Contents



# Table of Contents

Section Page

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

List of Tables

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

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

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

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

1.2.1 Public Notification That the Event Was Occurring (40 CFR

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

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

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

Description by July 1 of Calendar Year Following Event (40 CFR

50.14(c)(2)(iii)) ................................................................................................2

1.2.4 Document That the Public Comment Process Was Followed for Event

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

1.2.5 Submit Demonstration Supporting Exceptional Event Flag (40 CFR

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

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

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

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

2.2 Climate, Monsoon, and Thunderstorms .....................................................................5

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

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

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

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

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

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

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

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

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

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

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

5.1.3 PM Rule Effectiveness ................................................................................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

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

v

## Exceptional Event, Phoenix, July 11, 2012 Table of Contents



## vi 

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

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

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

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

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

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

Video Links ..........................................................................................................................1

Media Articles and Images ..................................................................................................2

Appendix A: Air Quality and Meteorological Data ...............................................................1

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

Appendix C: Historical Fluctuation Time-Series Graphs .....................................................1

Appendix D: ADEQ and NWS Forecast Products ..............................................................1

Appendix E: Affidavit of Public Notice ................................................................................1

## Exceptional Event, Phoenix, July 11, 2012 List of Figures



# List of Figures

Figure Page

2-1. Locations of air quality monitors that recorded exceedances of the 24-hr PM

NAAQS on July 11, 2012, and selected NWS monitors in the Phoenix area....................2 10



# 2-2. Locatio n of sites monitoring PM in Arizona on July 11, 2012. ...........................................3 10



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

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

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

2-6. Outflow boundaries from thunderstorms over south-central Arizona moved northnorthwestward and transported dust into the Phoenix area late on July 11, 2012............7

3-1. Hourly PM concentrations and wind speeds at the Greenwood monitor on July

10

− 12, 2012 ......................................................................................................................2 10



# 3-2. Hourly PM concentrations and wind speeds at the Durango Complex monitor on

July 10

− 12, 2012...............................................................................................................2 10



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

KPHX .. ..............................................................................................................................3 10 10



# 3-4. Hourly PM concentrations at Pinal County monitors on July 10

− 12, 2012. .......................3 10



# 3-5. Infrared satellit e image from 0045 LST on July 12, 2012 (GOES-West) ..............................4

3-6. Phoenix-area air quality and meteorological monitor and general wind direction. ..............5

3-7. Radar base velocity data at 2212 LST on July 11, 2012, from NWS Phoenix Doppler

radar..................................................................................................................................6

4-1. Twenty-four-hour average PM concentrations at the South Phoenix monitor

(2007-2012). ......................................................................................................................1 10



# 4-2. Daily maxi mum hourly average PM concentrations at the South Phoenix monitor

(2007-2012). ......................................................................................................................2 10



# 5-1. Timeline of Maricopa County fu gitive dust rules and ordinances. ........................................4

vii

## Exceptional Event, Phoenix, July 11, 2012 List of Tables



# List of Tables

Table Page

2-1. PM measurements on July 11, 2012. ................................................................................8 10



# 3-1. Observed wind spe eds and wind gusts at Maricopa County air quality and

meteorological monitors on July 11, 2012.........................................................................5

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

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

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

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



## viii

## Exceptional Event, Phoenix, July 11, 2012 Int roduction



## 1 

# 1. Introduction

On July 11, 2012, 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 July 11, 2012, 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 July 11, 2012, 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 July 11, 2012, produced PM 10



# concentrations in excess of normal historical fluctuations.

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

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

July 11, 2012, was not reasonably controllable or preventable.

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

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

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

# standard on July 11, 2012, would not

have occurred but for the event.

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

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

Appendix C contains 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 quality

## Exceptional Event, Phoenix, July 11, 2012 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 July 11, 2012. 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 July 11, 2012, data can be confirmed in AQS.



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

Description b y July 1 of Calenda r Year Following Event (40 CFR

50.14(c)(2)(iii))

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

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

# exceedances

that occurred at four monitors on July 11, 2012, 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 January 14, 2013. A copy of the public notice certification, along with

## Exceptional Event, Phoenix, July 11, 2012 Introduction



## 3 

# 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,

2015.



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

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

evidence must be provided for the following elements:

1. The event satisfies the criteria set forth in 40 CFR 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 bet ween 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, July 11, 2012 C onceptual Model



## 1 

# 2. Conceptual Model

This section provides a narrative background and summarizes the meteorological and

air quality conditions in place on July 11, 2012, 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 July 11, 2012.

AQS monitors typically 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 July 11, 2012, were recorded at the

Durango Complex, West 43 rd 

# Avenue, South Phoenix, and Greenwood monitors. The National

Weather Service (NWS) monitors measure meteorological data only. Phoenix Sky Harbor

International Airport (KPHX) and Phoenix Deer Valley Airport (KDVT) 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 July 11, 2012.

Please note that NWS data were unavailable for most other Phoenix area airports during the

time of this dust storm event.

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 the

low-lying areas of central and southern Arizona, with larger depositional areas focused in and

around the confluences of dry river channels.

## Exceptional Event, Phoenix, July 11, 2012 Conceptual Model



## 2 Figure 2-1. Locations of air quality monitors (gr een) that recorded exceedances of the

24-hr PM 10 

## NAAQS on July 11, 2012, and selected NWS monitors (blue) in the Phoenix

area.

## Exceptional Event, Phoenix, July 11, 2012 Conceptual Model



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

## in Arizona on July 11, 2012.

## Exceptional Event, Phoenix, July 11, 2012 Conceptual Model



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

## Exceptional Event, Phoenix, July 11, 2012 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, July 11, 2012 Conceptual Model



## 6 Cross

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

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

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

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

the nose, and the upward

‐ protruding part of the features is referred to as the

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

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

(shaded) high into the atmosphere.



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

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



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

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

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

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

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

# source regions are

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

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

consider general PM 10 

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

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



# 2.3 Event Day Summary

On the evening of July 11, 2012, strong winds generated by thunderstorms over central

and eastern Arizona transported dust northward into the Phoenix area ( Figure 2-6 ). The

windblown dust resulted in 24-hr average PM 10 

# concentrations in exceedance of the NAAQS at

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 south of the Phoenix area, and wind speeds over 20 mph,

with gusts over 30 mph, overwhelmed reasonabl e dust control measures. Monitors across

Maricopa and Pinal counties recorded high PM 10 

# concentrations during this dust storm,

illustrating the widespread, regional nature of the event.

## Exceptional Event, Phoenix, July 11, 2012 Conceptual Model



## 7 

# Region of

thunderstorm

development Windblown dust

transported north

‐

northwestward

Figure 2-6. Outflow boundaries from thundersto rms over south-central Arizona moved

north-northwestward and transported dust into the Phoenix area late on July 11, 2012.

## Exceptional Event, Phoenix, July 11, 2012 Conceptual Model



## 8 Table 2-1. PM 10 

## measurements on July 11, 2012. The four Phoenix-area monitors

discussed in this report are in bold.

Page 1 of 2

Monitor Monitor

Type Operator AQS Monitor ID 24-hr

Avg

PM 10 

## (μg/m 3 

## ) 1-hr

Max

PM 10 

## (μg/m 3 

## ) Time of

Max 1-hr

PM 10 

## (LST) AQS

Qualifier

Flag

Apache County

N/A TEOM WMAT 04-001-1003-81102-1 10 19 1900

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 23 85 1900

Maricopa County

West Phoenix TEOM MC 04-013-0019-81102-1 123 956 2300

North Phoenix TEOM MC 04-013-1004-81102-1 19 36 2300

Glendale TEOM MC 04-013-2001-81102-1 89 1433 2300

Central Phoenix TEOM MC 04-013-3002-81102-4 120 1412 2200

Greenwood TEOM MC 04-013-3010-81102-1 212 1875 2200 RJ

South Phoenix TEOM MC 04-013-4003-81102-1 285 3701 2200 RJ

West Chandler TEOM MC 04-013-4004-81102-1 52 381 2200

Tempe TEOM MC 04-013-4005-81102-1 96 1413 2300

Higley TEOM MC 04-013-4006-81102-1 24 76 2300

West 43 rd 

## Ave TEOM MC 04-013-4009-81102-1 172 1644 2200 RJ

Dysart TEOM MC 04-013-4010-81102-1 84 1126 2300

Buckeye TEOM MC 04-013-4011-81102-1 150 480 2300

Zuni Hills TEOM MC 04-013-4016-81102-1 56 912 2300

Fort

McDowell/Yuma

Frank TEOM FMIR 04-013-5100-81102-3 25 N/A N/A

Durango Complex TEOM MC 04-013-9812-81102-1 217 2301 2200 RJ

JLG Supersite BAM ADEQ 04-013-9997-81102-3 51 581 2200

JLG Supersite TEOM ADEQ 04-013-9997-81102-4 49 540 2200

Navajo County

N/A TEOM WMAT 04-017-1002-81102-1 10 33 1400

Pima County

Ajo TEOM ADEQ 04-019-0001-81102-3 33 134 0200

Rillito TEOM ADEQ 04-019-0020-81102-3 35 182 2200

Orange Grove FRM PCDEQ 04-019-0011-81102-2 14 N/A N/A

South Tucson FRM PCDEQ 04-019-1001-81102-1 14 N/A N/A

Green Valley TEOM PCDEQ 04-019-1030-81102-1 10 21 2000

Geronimo TEOM PCDEQ 04-019-1113-81102-1 14 73 2100

## Exceptional Event, Phoenix, July 11, 2012 Conceptual Model



## 9 Table 2-1. PM 10 

## measurements on July 11, 2012. The four Phoenix-area monitors

discussed in this report are in bold.

Page 2 of 2

Monitor Monitor

Type Operator AQS Monitor ID 24-hr

Avg

PM 10 

## (μg/m 3 

## ) 1-hr

Max

PM 10 

## (μg/m 3 

## ) Time of

Max 1-hr

PM 10 

## (LST) AQS

Qualifier

Flag

Pinal County

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 41 326 0000

Combs School TEOM PCAQCD 04-021-3009-81102-3 28 125 2000

Cowtown TEOM PCAQCD 04-021-3013-81102-3 273 1688 2200 RJ

Maricopa TEOM PCAQCD 04-021-3010-81102-3 145 877 0000 RJ

Pinal County

Housing TEOM PCAQCD 04-021-3011-81102-3 39 323 0000

Stanfield TEOM PCAQCD 04-021-3008-81102-3 313 2826 0000 RJ

Santa Cruz County

Nogales Post Office BAM ADEQ 04-023-0004-81102-3 17 41 0600

Yuma County

Yuma Supersite TEOM ADEQ 04-027-8011-81102-3 79 311 0900

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 District

PCDEQ: Pima County Department of Environmental Quality

RJ: qualifier flag for high winds

## Exceptional Event, Phoenix, July 11, 2012 Ca usal Relationship



## 1 

# 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 July 11, 2012. Late in the evening on July 10, 2012, thunderstorms developed over the

higher terrain of central and eastern Arizona, just east of the Phoenix area, generating weak

outflow boundaries that carried dust westward into the Phoenix area. This outflow caused

elevated PM 10 

# concentrations at several Maricopa County monitors and high PM 10



# concentrations (over 2500  g/m 3 

# at one monitor) in Pinal County very late on July 10, 2012, into

early July 11, 2012 ( Figure 3-1

, Figure 3-2

, Figure 3-3, and Figure 3-4 ).

Late in the evening on July 11, 2012, a second round of thunderstorms developed over

south-central Arizona, just south of the Phoenix area ( Figure 3-5 ). Outflow from these later

thunderstorms propagated northwestward across western Pinal County and into Maricopa

County. This later outflow event had a greater effect on PM 10 

# concentrations and wind speeds

at Maricopa County monitors compared to the w eaker event early on July 11, 2012. As stated

in Section 2.2, thunderstorms associated with the summer monsoon season can generate

strong winds and blowing dust across Arizona. PM 10 

# concentrations increased at Pinal County

monitors about one hour before PM 10 

# increased at Maricopa County monitors, which is

consistent with the location and movement of the outflow boundary and indicates that the likely

source regions for PM 10 

# during the July 11, 2012, event were the undeveloped, open land areas

south of Maricopa County. This region largely consists of natural, undisturbed desert. The last

rainfall in the Phoenix area preceding the July 11, 2012, event was minimal, with 0.14 inches

recorded at Phoenix-Sky Harbor International Airport (KPHX) on July 4, 2012. 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.

## Exceptional Event, Phoenix, July 11, 2012 Causal Relationship



## Figure 3-1. Hourly PM 10 

## concentrations and wind speeds at the Greenwood monitor on

July 10

− 12, 2012. PM 10 

## concentrations and wind gust speeds sharply increased at

2200 LST on July 11, 2012, indicating the arrival of windblown dust. Wind gusts of over

50 mph were measured.

Figure 3-2. Hourly PM 10 

## concentrations and wind speeds at the Durango Complex

monitor on July 10

− 12, 2012. PM 10 

## concentrations sharply increased at 2200 LST on

July 11, 2012, coinciding with wind gusts of nearly 50 mph and indicating the arrival of

windblown dust.

2

## Exceptional Event, Phoenix, July 11, 2012 Causal Relationship



## Figure 3-3. Hourly PM 10 

## concentrations at the Phoenix-area PM 10 

## monitors and visibility

at KPHX. Visibility was significantly reduced at KPHX between 2200 LST on July 11,

2012, and 0100 LST on July 12, 2012, coincident with the sharp increase in PM 10



## concentrations at area PM 10 

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

reduction in visibility and increase in PM 10 

## concentrations was evident around 0100 LST

on July 11, 2012, which also contributed to high daily average PM 10 

## concentrations at the

exceedance monitors.

0 500 1000 1500 2000 2500 3000 3500 4000 4500Concentration(ug/m3)



### July 10, 2012 July 11, 2012 July 12, 2012

Time (LST) Casa Grande Downtown PM

10



### Stanfield PM

10



### Combs School PM

10



### Maricopa PM

10



### Pinal County Housing PM

10



### Cowtown PM

10



## Figure 3-4. Hourly PM 10 

## concentrations at Pinal County monitors on July 10

− 12, 2012.

PM 10 

## concentrations sharply increased between 2200 LST on July 10, 2012, and 0000

LST on July 11, 2012, and again between 2100 LST and 2300 LST on July 11, 2012,

coinciding with the arrival of windblown dust due to thunderstorm outflows.

3

## Exceptional Event, Phoenix, July 11, 2012 Causal Relationship



## Figure 3-5. Infrared satelli te image from 0045 LST on July 12, 2012 (GOES-West).

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

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

carried dust northward into Maricopa County.



# Figure 3-6 and Table 3-1 summarize the progression of the thunderstorm outflow

boundary and windblown dust as it moved through southwestern Arizona on the evening of

July 11, 2012. The outflow boundary approached the Phoenix area from the southeast, first

arriving in the Phoenix area around 2200 LST on July 11. These winds carried windblown dust

to the Durango Complex, West 43 rd 

# Ave, South Phoenix, and Greenwood monitors. Sustained

winds of 23 mph and a peak gust of 33 mph were reported at Phoenix Sky Harbor International

Airport (KPHX). The outflow boundary continued northwestward and carried windblown dust to

the Buckeye monitor during the 2300 LST hour. Figure 3-7 shows radar velocity data that

illustrate the location of the outflow boundary as it moved into the Phoenix metropolitan area.

Other monitors in the Phoenix area also recorded elevated PM 10 

# concentrations as the outflow

boundary passed, but the concentrations were not high enough at those monitors to result in

exceedances of the NAAQS.

4

## Exceptional Event, Phoenix, July 11, 2012 Causal Relationship



## Figure 3-6. Phoenix-area air quality and meteorological monitor 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. South-southeasterly winds associated with thunderstorm outflow

transported dust across the Phoenix area during the late evening hours of July 11, 2012.

Table 3-1. Observed wind speeds and wind gusts at Maricopa County air quality and

meteorological monitors on July 11, 2012. All air quality monitors reported high PM 10 

## concentrations at 2200 and 2300 LST on July 11, 2012, coincident with gusty winds. Filled

circles identify sites shown in Figure 3-6.

Site Monitor 1-hr Max

PM 10 

## (μg/m 3 

## ) Time of

Observation

(LST) Wind

Speed

(mph) Wind Gust

(mph) Wind

Direction

(degrees)

Durango

Complex 2301 2200 8 26 131

West 43 rd



## Ave 1644 2200 9 31 148

South

Phoenix 3701 2200 9 28 170

Greenwood 1875 2200 6 24 108

KPHX

- 2233 23 33 160

KDVT

- 2343 14 29 160

5

## Exceptional Event, Phoenix, July 11, 2012 Causal Relationship

Tempe

West 43 rd 

### St Greenwood

Durango Complex

Buckeye Outflow boundary

Radar Site



## Figure 3-7. Radar base velocity data at 2212 LST on July 11, 2012, from NWS Phoenix

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

away from the radar, and yellow indicates little motion away from the radar. A welldefined outflow boundary (dashed line) approach ed the Phoenix area from the southeast.

This boundary carried dust northwestward 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 3-1,

Figure 3-2, and Appendix A). Visibility at KPHX also decreased significantly with the arrival of

the dust (Figure 3-3). A similar reduction in visibility was reported at KDVT (north of the

Greenwood PM 10 

# monitor). Weather observations at KPHX also indicated widespread dust

coincident with the high PM 10 

# concentrations. It is also noteworthy that, immediately before the

abrupt increase in PM 10 

# concentrations at each monitor, wind gusts were comparatively much

lighter and PM 10 

# concentrations were much lower, illustrating the correlation between the gusty

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 2200 LST on July 11, 2012. Links to

these videos, other media coverage, and images pertaining to this windblown dust event are

shown in Appendix B.



# 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

6

## Exceptional Event, Phoenix, July 11, 2012 Causal Relationship



## 7 

# monitors on July 11, 2012. 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.

## Exceptional Event, Phoenix, July 11, 2012 Historical Norm



## 1 

# 4. Historical Norm

4. 1 Analysis

PM 10 

# concentrations measured at the South Phoenix monitor on July 11, 2012, were

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

PM 10 

# concentrations measured on July 11, 2012, were compared to a historical 2007–2012 sixyear annual data set at each monitor. The PM 10 

# concentrations measured at the South Phoenix

monitor on July 11, 2012, were among the highest 24-hr averages ( Figure 4-1 ) and among the

highest daily maximum hourly average concentrations ( Figure 4-2 ) measured over the five-year

period. Similar time-series plots for the Durango, Greenwood, and West 43 rd 

# 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 July 11, 2012, were outside of

normal historical fluctuations. This analysis pr ovides 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 South Phoenix 5-Year Historical Fluctuation - 24 Hour Averages

July 11, 2012



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

## concentrations at the South Phoenix

monitor (2007-2012). The 24-hr average PM 10 

## concentration on July 11, 2012, is

highli ghted in red.

## Exceptional Event, Phoenix, July 11, 2012 Historical Norm



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

Date 

### South Phoenix 5-Year Historical Fluctu ation - Daily Maximum Hourly Averages

July 11, 2012



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

## concentrations at the South Phoenix

monitor (2007-2012). The daily maximu m hourly average concentration on July 11,

2012, is highlighted in red.

## Exceptional Event, Phoenix, July 11, 2012 No t Reas 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, July 11, 2012 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, July 11, 2012 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

## Exceptional Event, Phoenix, July 11, 2012 Not Reas onably Controllable or Preventable



## 4 

# how many sources regulated by MCAQD during the subject time period received no PM 10 

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

compliance during calendar year 2007 was 76% for sources subject to Rule 310, 85% for Rule

310.01 sources, and 40% for Rule 316 sources. In early 2008, Rules 310, 310.01, and 316

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

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

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

# State

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

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



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



# 5.1 .4 Compliance and Enforcement Activities

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

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

proactive inspections and surveillance inspections, conducted both during and after significant

## Exceptional Event, Phoenix, July 11, 2012 Not Reas onably Controllable or Preventable



## 5 

# 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 are

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

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

5-min intervals. Previously, hourly readings were available. The real-time data reporting

system includes a mechanism to alert MCAQD fiel d staff when PM concentrations are elevated.

The system allows MCAQD responders to review concentrations 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 local governments of the elevated PM 10



# concentrations.



# 5. 1.5 Review of Source-Permi t ted Inspections and Public Complaints

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

(AZURITE) database and Maricopa County’s Envi ronmental Management System were queried

to compile a list of inspections for the permitted sources in the Phoenix area around the time of

the July 11, 2012, 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 July 8-14, 2012,

MCAQD inspectors conducted a total of 188 inspections of permitted facilities, 129 of which

were sources of fugitive dust. Additionally, MCAQD conducted 7 inspections on vacant lots and

unpaved parking lots during this period. During this 7-day period, a total of 64 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 mon itor.

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

the 7- day period from July 8 through July 14, 2012, MCAQD received 18 complaints, of which

11 were windblown dust-related. Each complaint was assigned to and investigated by a

## Exceptional Event, Phoenix, July 11, 2012 Not Reas onably Controllable or Preventable



## 6 

# MCAQD inspector. A review of all pertinent records from this period indicates that MCAQD

inspectors did not observe any PM 10 

# emission violations of local, state, or federal regulations

within a 4-mile radius of an 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-wind

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 documentation, there is no

evidence to suggest that agricultural activities produced unusual PM 10 

# emissions on July 11,

2012. The ADEQ Ag BMP inspector did not receive any complaints in the three days prior to

the event.



# 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 July 11, 2012, a Maricopa County Dust Control

Forecast was issued by ADEQ, indicating a low risk level for unhealthy PM 10 

# . The Dust Control

Forecast stated that southeast winds between 5 and 10 mph were expected, and that “during

the active summer monsoon period, strong outflow winds from even distant thunderstorms can

generate periods of dense blowing dust.”

The NWS office in Phoenix issued Blowing Dust Advisories for portions of Pinal and

Maricopa counties during the period of gusty outflow winds and high PM 10 

# concentrations in the

Phoenix area. These advisories warned residents of the potential for gusty winds in excess of

40 mph and visibilities reduced below 1 mile due to blowing dust.



# 5 .3 Wind Observations

Wind gusts over 30 mph were measured at several monitors as the outflow boundary

moved through the Phoenix area (Figure 3-1, Figure 3-2, and Appendix A).



# 5 .4 Summary

The thunderstorm outflow event of July 11, 2012, produced strong winds that

transported dust and PM 10 

# into the Phoenix PM 10 

# Nonattainment Area. The source region of

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

PM 10 

# Nonattainment Area, primarily the deserts of Pima, Pinal and southern Maricopa County.

The Phoenix area is designated as a serious nonattainment area for PM 10 

# and is required to

## Exceptional Event, Phoenix, July 11, 2012 Not Reasonably Controllable or Preventable



## 7 

# have BACM for all significant sources of PM 10 

# . BACM on significant anthropogenic sources

were in place and enforced during the events, and pro-active tracking and response to the

events by regulatory agencies and local governments confirmed the uncontrollable nature o

dust emissions; therefore, these pre-existing prior-approved required controls are adequate

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

these purposes. f the

for

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 July 11, 2012 recorded within the Phoenix PM 10 

# Nonattainment Area were not

reasonably controllable or preventable.

## Exceptional Event, Phoenix, July 11, 2012 Bu t-For Analysis



## 1 

# 6. But-For Analysis

6 .1 Discussion

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

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

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

the PM 10 

# exceedances in the Phoenix PM 10 

# Nonattainment Area on July 11, 2012,

 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 south of Phoenix.

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

exceedances of July 11, 2012, 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 in the vicinity of the exceedance monitors 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 July 11, 2012, 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, July 11, 2012 C onclusions



## 1 

# 7. Conclusions

The PM 10 

# exceedances that occurred on July 11, 2012, satisfy the criteria of the EER,

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

provided for the following elements:

 The event satisfies the criteria set forth in 40 CFR 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;

 Th ere 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

July 11, 2012, were not reasonably controllable or preventable.



# 7 .3 Natural Event

As discussed above, the PM 10 

# exceedances on July 11, 2012, 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, July 11, 2012 Conclusions



## 2 

# tion 3).

). 

# 7.4 Clear Causal Relationship

The following points demonstrate that the high PM 10 

# concentrations were caused by

windblown dust:

 Ti me-series graphs of PM 10 

# concentrations show that the timing of high PM 10 

# at

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

 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 imagery shows that large quantities of PM 10 

# were transported into the

Phoenix area on July 11, 2012. 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 Histori cal 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 July 11, 2012, 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, July 11, 2012 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 July 10-12, 2012. 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 South Phoenix monitor

on July 10

− 12, 2012. PM 10 

## concentrations and wind gusts sharply increased at 2200

LST on July 11, 2012, indicating the arrival of windblown dust.

1

## Exceptional Event, Phoenix, July 11, 2012 Appendix A



## Figure A-2. Hourly PM 10 

## concentrations and wind speeds at the West 43 rd 

## Avenue

monitor on July 10

− 12, 2012. PM 10 

## concentrations and wind gusts sharply increased at

2200 LST on July 11, 2012, indicating the arrival of windblown dust.

2

# 3U.S. Department of CommerceNational Oceanic & Atmospheric AdministrationQUALITY CONTROLLED LOCALCLIMATOLOGICAL DATA (final)HOURLY OBSERVATIONS TABLEPHOENIX SKY HARBOR INTL AIRPORT (23183)PHOENIX, AZ (07/2012)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)12345678910111213141516171819202122231111111111111111111111111111111111111111111111111111111111005101510251035104510551065107510851095110511151125113511451155116511751185119512051215122332237225122562315234723511111111111111111111111111111111111111111111111111111111111SCT160 BKN180 BKN240SCT160 BKN180 BKN240SCT180 BKN240SCT180 BKN240FEW140 SCT180 BKN240FEW140 SCT200 BKN240FEW140 SCT180 BKN240FEW180 BKN240FEW180 BKN240FEW090 SCT180 BKN240FEW095 BKN240FEW110 BKN240FEW100 BKN240FEW110 BKN240FEW100 SCT160 BKN250FEW100 SCT130 SCT200FEW090 SCT130 SCT200FEW090 SCT110 SCT200FEW090 SCT110 SCT200FEW110 SCT170 SCT200FEW110 SCT170 SCT200FEW090 BKN130 BKN200SCT014 BKN120 BKN200BKN012 BKN120 BKN200BKN012 BKN075 BKN110BKN012CB BKN075CB BKN120BKN005CB BKN020 BKN070BKN018CB BKN070CB BKN120BKN018CB BKN070CB BKN1209.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.002.001.752.002.003.006.007.00DUDUDU-TSRATSDUTSDU9393929191909193981001031061051091081081101081071051051039797949393939433.933.933.332.832.832.232.833.936.737.839.441.140.642.842.242.243.342.241.740.640.639.436.036.034.434.034.034.034.4717170717170717173737373737473737373737373737272727272737321.821.521.321.721.721.321.421.822.522.822.722.922.523.122.722.523.022.722.622.822.522.522.122.121.922.022.022.622.5605959616160606060605857565655545555555756575959606161636215.615.015.016.116.115.615.615.615.615.614.413.913.313.312.812.212.812.812.813.913.313.915.015.015.616.016.017.016.733323337373735332827232020181717161718212022282832343437351111869106067139375015961310323201714141414130100120100070120180000VR120140170VR140VR000310290VR330330010160160150170320290280182018333224232528.6328.6428.6528.6628.6628.6828.6928.7028.7128.6928.6928.6628.6428.6028.5628.5328.5228.5128.5228.5428.5428.5728.6128.6128.6028.6128.6328.6228.621118863302200701600802902500502129.7329.7429.7529.7629.7629.7829.8029.8129.8129.8029.7929.7629.7429.7029.6629.6329.6229.6129.6229.6429.6429.67MM29.70MMM29.71AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAASPSPAASPSPSPAATT29.8029.8129.8229.8329.8329.8529.8729.8829.8929.8729.8629.8329.8129.7729.7329.7029.6929.6829.6929.7129.7129.7429.7829.7829.7729.7829.8029.7929.79Figure A-4.Quality-controlled local climatological data hourly observations table for Phoenix Sky Harbor International Airport, Phoenix, AZ(07/11/2012). Note that visibilities were reduced with gusty winds and DU (widespread dust) reported after 2200 LST coincidentwith high PM10concentrations in the Phoenixarea. Dynamically generated viahttp://cdo.ncdc.noaa.gov/qclcd/QCLCD.

# 4U.S. Department of CommerceNational Oceanic & Atmospheric AdministrationQUALITY CONTROLLED LOCALCLIMATOLOGICAL DATA (final)HOURLY OBSERVATIONS TABLEPHOENIX DEER VALLEY ARPT (03184)PHOENIX, AZ (07/2012)National Climatic Data CenterFederal Building151 Patton AvenueAsheville, North Carolina 28801Elevation: 1455 ft. above sea levelLatitude: 33.688Longitude: -112.081Data Version: VER2DryBulbTempWetBulbTempDewPointTempDateTime(LST)StationTypeSkyConditionsVisibility(SM)WeatherType(F)(C)(F)(C)(F)(C)RelHumd%WindSpeed(MPH)WindDirWindGusts(MPH)StationPressure(in. hg)PressTendNet3-hrChg(mb)SeaLevelPressure(in. hg)ReportTypePrecip.Total(in)Altimeter(in. hg)12345678910111213141516171819202122231111111111111111111111111111111111111111111111111111005301530253035304530553065307530853095310531153125313531453155316531753185319532053215322532343234623531212121212121212121212121212121212121212121212121212CLRCLRCLRCLRCLRCLRCLRCLRCLRCLRCLRCLRCLRCLRCLRCLRCLRCLRCLRCLRCLRCLRSCT120FEW046 BKN095 OVC110FEW044 SCT070 BKN110FEW042 SCT070 BKN10010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.004.002.503.007.00HZ+RA+RARA9291919089899193969810110210310310410410610310210099999890888533.332.832.832.231.731.732.833.935.636.738.338.939.439.440.040.041.139.438.937.837.237.236.732.031.029.4707069707070717172727373727272727373727271717170707221.321.120.621.021.121.121.421.722.222.222.722.522.422.222.322.322.822.722.322.021.621.621.421.021.222.3595957596060606060595958575656565758575756565659616615.015.013.915.015.615.615.615.615.615.015.014.413.913.313.313.313.914.413.913.913.313.313.315.016.018.9333432353838353330272523222120202023232424242535405389510860559119709531511118710141113160140100100090080000120VR150140180VR000240VR3403103303303300101201601501801629292128.2728.2828.2828.2928.3028.3228.3328.3528.3528.3428.3228.3028.2728.2328.2028.1828.1728.1728.1728.1828.2028.2128.2228.2528.2528.251318863302700601400802802200601229.7329.7529.7529.7629.7729.7929.8029.8129.8229.8029.7929.7629.7429.7029.6729.6529.6329.6329.6429.6529.6629.6729.69MM29.72AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAASPSPAA0.2129.8329.8429.8429.8529.8629.8829.8929.9129.9129.9029.8829.8629.8329.7929.7629.7429.7229.7229.7329.7429.7529.7729.7829.8129.8129.81Figure A-5.Quality-controlled local climatological data hourly observationstable for Phoenix Deer Valley Airport, Phoenix, AZ (07/11/2012).Note in the Weather Type column that HZ (haze) was reported withreduced visibilities and gusty winds coincident with the arrival of high PM10concentrations in the Phoenixarea. Dynamically generated viahttp://cdo.ncdc.noaa.gov/qclcd/QCLCD.

# 5U.S. Department of CommerceNational Oceanic & Atmospheric AdministrationQUALITY CONTROLLED LOCALCLIMATOLOGICAL DATA(final)HOURLY OBSERVATIONS TABLECASA GRANDE MUNICIPAL ARPT (03914)CASA GRANDE, AZ(07/2012)National Climatic Data CenterFederal Building151 Patton AvenueAsheville, North Carolina 28801Elevation: 1462 ft. above sea levelLatitude: 32.95Longitude: -111.766Data Version: VER2DryBulbTempWetBulbTempDewPointTempDateTime(LST)StationTypeSkyConditionsVisibility(SM)WeatherType(F)(C)(F)(C)(F)(C)RelHumd%WindSpeed(MPH)WindDirWindGusts(MPH)StationPressure(in. hg)PressTendNet3-hrChg(mb)SeaLevelPressure(in. hg)ReportTypePrecip.Total(in)Altimeter(in. hg)12345678910111213141516171819202122231111111111111111111111111111111111111111111111111111111111111111111100150035005501150135015502150235025503150335035504150435045505150535055506150635065507150735075508150835085509150935095510151035105511150000000000000000000000000000000000CLRCLRCLRCLRCLRCLRFEW065 FEW080 SCT090CLRCLRCLRCLRCLRCLRCLRCLRCLRCLRCLRCLRCLRCLRCLRCLRCLRCLRCLRCLRCLRCLRCLRCLRCLRCLRCLR10.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.008886848888888684848484848284848482848486888888888888909193979797979931.030.029.031.031.031.030.029.029.029.029.029.028.029.029.029.028.029.029.030.031.031.031.031.031.031.032.033.034.036.036.036.036.037.07170707170717171727070707070707070707071717171727271727373747474747321.820.921.221.821.221.821.821.522.121.221.221.220.821.221.221.220.821.221.221.521.821.821.822.122.121.822.422.622.923.523.523.223.222.96361636361636464666363636363636363636363636363646463646464646463636117.016.017.017.016.017.018.018.019.017.017.017.017.017.017.017.017.017.017.017.017.017.017.018.018.017.018.018.018.018.018.017.017.016.04343494340434851554949495349494953494946434343454543424138343433332922207068955810913978550656600505550578160170200000140090070040020080090090080110110090100100000080060140160000000090000180160170000170150100303128.2828.2728.2828.2828.3028.3128.3128.3228.3228.3228.3228.3228.3328.3328.3428.3428.3428.3528.3528.3528.3628.3628.3828.3828.3928.3828.3828.3828.3728.3728.3628.3628.3628.352227003010014007MMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA29.8329.8229.8329.8329.8529.8629.8629.8729.8729.8729.8729.8729.8829.8829.8929.8929.8929.9029.9029.9029.9129.9129.9329.9329.9429.9329.9329.9329.9229.9229.9129.9129.9129.90

# 611111111111111111111111111111111111111111111111111111111111111111111111111111135115512151235125513151335135514151435145515151535155516151635165517151735175518151835185519151935195520152035205521152135215522152235225523152335235500000000000000000000000000000000000000CLRCLRCLRCLRCLRCLRCLRCLRCLRCLRCLRCLRCLRCLRCLRCLRCLRCLRCLRCLRCLRCLRCLRCLRCLRCLRSCT120BKN120BKN120FEW095 BKN120FEW025 SCT055 BKN070FEW024 SCT055 BKN070FEW015 SCT021 BKN037CLRCLRFEW110CLRCLR10.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.0010.008.0010.0010.0010.0010.0010.0010.0010.00VCTSTSTSVCTSTSVCTS10010010010210210410410410210210210410610610610610410610410410410410210210210210010010099888275797981818138.038.038.039.039.040.040.040.039.039.039.040.041.041.041.041.040.041.040.040.040.040.039.039.039.039.038.038.038.037.031.028.024.026.026.027.027.027.0747474747475757473737373747373737474747373737272727272727274737169697071717123.023.023.023.323.323.623.623.122.822.822.822.623.322.822.822.823.123.323.122.622.622.622.322.322.322.322.022.022.023.522.721.820.620.621.321.621.621.6616161616161615959595957595757575959595757575757575757575763666666646666666616.016.016.016.016.016.016.015.015.015.015.014.015.014.014.014.015.015.015.014.014.014.014.014.014.014.014.014.014.017.019.019.019.018.019.019.019.019.0282828262624242324242421212020202321232121212323232324242431485874606560606095811811710588663711131113111413109755301325201169118708018009015016016013007032016010004011020024027028027027026026025024024024025025026000017006002032023022021023020017171821211616181820332928.3428.3328.3228.3128.3028.2928.2828.2728.2728.2528.2528.2328.2128.2128.2028.2128.2028.2028.2028.2028.1928.2028.2028.2028.2128.2228.2228.2228.2428.2728.3228.3628.3028.2928.2728.2828.2928.307722030027007020MMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA0.030.030.030.100.100.1029.8929.8829.8729.8629.8529.8429.8329.8229.8129.7929.7929.7729.7529.7529.7429.7529.7429.7429.7429.7429.7329.7429.7429.7429.7529.7629.7629.7629.7829.8129.8729.9129.8529.8429.8229.8329.8429.85Figure A-6.Quality-controlled local climatological data hourly observations table for Casa Grande Municipal Airport, Casa Grande, AZ(07/11/2012). Note that reduced visibilities with gusty winds occurred after 2100 LST coincident with the arrival of high PM10concentrations inthe Casa Grande area. Dynamically generated viahttp://cdo.ncdc.noaa.gov/qclcd/QCLCD.

## Exceptional Event, Phoenix, July 11, 2012 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_07112012.mp4

Estrella Mountains: www.phoenixvis.net/videos/mpeg4/ESMO_07112012.mp4

Camelback Mountains: www.phoenixvis.net/videos/mpeg4/CAME_07112012.mp4

Superstition Mountains: www.phoenixvis.net/videos/mpeg4/SUPM_07112012.mp4

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

some links to these videos.

Lightning Over Phoenix, AZ – July 11, 2012 (clip 1)

http://www.youtube.com/watch?v=zz0Lc9hlKVA

AZ monsoon video – July 11, 2012

http://www.youtube.com/watch?v=20sdQEZka-Q

1

## Exceptional Event, Phoenix, July 11, 2012 Appendix B



# Media Articles and Images

http://www.accuweather.com/en/weather-blogs/clark/another-scorcherthunderstorms-toincrease/67876

Another Scorcher-Thunderstorms to Increase

Ken Clark

July 11, 2012; 12:52 PM

Today has been another sizzler in the Southwest. Many places inland from the cooling effects of

the Pacific were at, or well above, 100. An increase in low-level moisture in the southeast

deserts of California have kept temperatures lower than yesterday but, of course, the added

moisture is making up for that. The AccuWeather RealFeel temperatures are pretty much the

same as yesterday in a lot of these areas. I am not sure how hot the tables and slots are in

Vegas today in giving up money but I can guarantee you those moving between casinos are hot

and giving up a lot of sweat as temperatures on the Strip have risen to between 111 and 114

degrees.

It will stay hot the next couple of days but it probably will not be as hot in all the deserts as the

last two days because of increase moisture causing an increase in cloud cover and also the

development of thunderstorms. A look at the wate r vapor satellite picture from early afternoon

Wednesday shows moisture moving in from the southeast.

2

## Exceptional Event, Phoenix, July 11, 2012 Appendix B



# A big increase in available moisture from today to tomorrow will take place over all of Southern

California north into southern Nevada and into portions of the Sierra. This will help the

development of showers and thunderstorms in al l the deserts and mountains. The most active

time will be in the afternoon and evening hours. With a lot more water vapor in the air tomorrow

expect thunderstorms that develop to bring locall y heavy rain that could cause some temporary

flash flooding. Friday looks active too then over the weekend moisture will be on the decrease

as a trough drops down from the north.

As an interesting side not. The so-called low temperature this morning in Death Valley was a

toasty 103 degrees.

http://thetandd.com/news/more-thunderstorms-may-rumble-through/article_66eaea26-cb1c11e1-80a1-001a4bcf887a.html

More thunderstorms may rumble through

By Gene Zaleski

July 11, 2012 5:30 am

Mother Nature was not so nurturing Tuesday afternoon as downed trees, power outages and

nickel-size hail were reported primarily in the southern portion of The Times and Democrat

Region.

And there could be more on the way.

“We are expecting a good chance of showers and thunderstorms through the end of this week,”

National Weather Service meteorologist Dan Miller said.

Miller said the rain is welcome not only because conditions have been dry, but it has helped

reduce the temperatures which have hovered near the century mark.

On Tuesday, the National Weather Service report ed trees down from Bamberg to Denmark. Hail

was reported near Cope, along with windy conditions.

In Orangeburg County, trees were down from Bowman’s Winter Creek Road to Interstate 26.

Trees were also reported down on Vance Road in the Providence area as well as on Bass

Drive.

In Bamberg, a couple thousand Edisto Electric Cooperative Inc. customers were without power

for about one hour Tuesday afternoon as storms rolled through.

“It has been kind of crazy,” Edisto Electric Manager of Member Services Frank Furtick said.

“The storm took a transmission line down that had most of our system around Bamberg and the

town of Bamberg.”

Furtick said the transmission line was rerouted and customers had power restored.

3

## Exceptional Event, Phoenix, July 11, 2012 Appendix B



## 4 

# As of late Tuesday afternoon, Furtick said there were still scattered outages in the Bamberg,

Ehrhardt, Cope and St. George areas.

Sharon Hammond, Bamberg County Emergency Se rvices director, says trees were down

throughout the county.

Calhoun County Emergency Services Director Bill Minikiewicz said there were no reports of

significant weather-related damage on Tuesday afternoon.

“We are the blessed people,” he said.

The T&D Region is under a hazardous weather outlook, with the forecast calling for more

thunderstorms today and through the end of the week.

The chance of rain is 60 percent for today and 50 percent for Thursday. The chance of rainfall

over the weekend is about 30 percent.

## Exceptional Event, Phoenix, July 11, 2012 Appendix C



# Appendix C: Historical Fluctuation Time-Series Graphs

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



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

July 11, 2012



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

## concentrations at the Durango monitor

(2007–2012). The 24-hr average PM 10 

## concentration on July 11, 2012, is shown in red.

1

## Exceptional Event, Phoenix, July 11, 2012 Appendix C

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



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

July 11, 2012



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

## concentrations at the Greenwood monitor

(2007–2012). The 24-hr average PM 10 

## concentration on July 11, 2012, is shown in red.

2

## Exceptional Event, Phoenix, July 11, 2012 Appendix C

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



### Date West 43rd 5-Year Historical Fluctuation - 24 Hour Averages

July 11, 2012



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

## concentrations at the West 43rd monitor

(2007–2012). The 24-hr average PM 10 

## concentration on July 11, 2012, is shown in red.

3

## Exceptional Event, Phoenix, July 11, 2012 Appendix C

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

Date 

### Durango 5-Year Historical Fluctuation - Daily Maximum Hourly Averages

July 11, 2012



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

## concentrations at the Durango monitor

(2007–2012). The daily maximum hourly average concentration on July 11, 2012, is

shown in red.

4

## Exceptional Event, Phoenix, July 11, 2012 Appendix C

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

Date 

### Greenwood 5-Year Historical Fluctuation - Daily Maximum Hourly Averages

July 11, 2012



## Figure C-5. Daily maximum hourly average PM 10 

## concentrations at the Greenwood

monitor (2007–2012). The daily maximum hourly average concentration on July 11,

2012, is shown in red.

5

## Exceptional Event, Phoenix, July 11, 2012 Appendix C



## 6 0 500 1000 1500 2000 2500 3000 3500 4000 4500 5000PM10 Concentration (μg/m3)

Date 

### West 43rd 5-Year Historical Fluctuat ion - Daily Maximum Hourly Averages

July 11, 2012



## Figure C-6. Daily maximum hourly average PM 10 

## concentrations at the West 43rd

monitor (2007–2012). The daily maximum hourly average concentration on July 11,

2012, is shown in red.

## Exceptional Event, Phoenix, July 11, 2012 Appendix D



## 1 

# Appendix D: ADEQ and NWS Forecast Products

MARICOPA COUNTY DUST CONTROL FORECAST

ISSUED TUESDAY, JULY 10, 2012

Three-day weather outlook:

NOTE: DURING THE ACTIVE SUMMER MONSOON PERIOD, STRONG OUTFLOW WINDS FROM EVEN DISTANT

THUNDERSTORMS CAN GENERATE PERIODS OF DENSE BLOWING DUST

The Phoenix forecast area is still looking for its first valley-wi de rain event of the monsoon season. Spotty storm across

the deserts to southeast have lowered the chances for blowing dust impacting the area. With high pressure now over

the Four Corners, the steering flow is out of the northeast. These storms tend to be more electric rather than dust

producing. Thus, the risk of exceeding the 24-hr PM10 health standard in Phoenix has been lowered to Low through

Sunday.



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

RISK LEVEL 

## SURFACE WINDS 

## STAGNATION UNHEALTHY PM-10

Day 1: Wed 07/11/2012 Southeast winds

between 5 and 10

mph are expected

(20% chance of rain). No significant

+ stagnation is

expected. = 

# LOW

Day 2: Thu 07/12/2012 Southeast winds

between 5 and 10

mph are expected

(20% chance of rain). No significant

+ stagnation is

expected. = 

# LOW

Day 3: Fri 07/13/2012 Southeast winds

between 5 and 10

mph are expected

(30% chance of rain). No significant

+ stagnation is

expected. = 

# LOW

EXTENDED OUTLOOK

= 

# LO W Day 4: Sat 07/14/2012 Southeast winds

between 5 and 10

mph are expected

(30% chance of rain). + No significant

stagnation is likely.

= 

# LO W Day 5: Sun 07/15/2012 Southeast winds

between 5 and 10

mph are expected

(30% chance of rain). + No significant

stagnation is likely.

## Exceptional Event, Phoenix, July 11, 2012 Appendix D



## 2 The Maricopa County Dust Control Action Forecast is issued to assist in the planning of work

activities to help reduce dust pollution. A recorded message of this forecast can be accessed at

602-771-2368 . To review the complete air quality forecast for the Phoenix metropolitan area, as

well as the health impacts and reduction methods for different air pollutants, call 602-771-

2367 for recorded forecast information or click on ADEQ's Air Quality Forecast at

http://www.azdeq.gov/environ/ air/o zone/ensemble.pdf

.

JRP 04/28/2011

## Exceptional Event, Phoenix, July 11, 2012 Appendix D



## 3 VERY UNHEALTHY (201-300)

UNHEALTHY (151-200)

UNHEALTHY FOR SENSITIVE GROUPS (101-150)

MODERATE (51-100)

GOOD (0-50)

For more information visit:

http://www.airnow.gov/index.cfm?action=aqibasics.aqi

*LINK TO 2012 AIR POLLUTION EXCEEDANCE GRAPH*



# AIR QUALITY FORECAST FO R WEDNESDAY, JULY 11, 2012

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

areas within and bordering Maricopa County in Arizona



## FORECAST

DATE

NOTICES

(*SEE BELOW

FOR DETAILS)

A IR POLLUT A NT 

# YESTERDAY

MON 07/09/2012

Ozone Health

Watch

DUST

Highest AQI Reading/Site



### (* Preliminary data only *) 

# TODAY

TUE 07/10/2012

Ozone Health

Watch

DUST

NWS Excessive

Heat Warning 

# TOMORROW

WED 07/11/2012

NWS Excessive

Heat Warning 

# EXTENDED

THU 07/12/2012



# O3* 90

BLUE POINT 

## 97

MODERATE 

## 54

MODERATE 

## 57

MODERATE



# CO* 5

CENTRAL PHOENIX 

## 6

GOOD 

## 8

GOOD 

## 6

GOOD



# PM-10* 36

DURANGO 

## 65

MODERATE 

## 45

GOOD 

## 42

GOOD



# PM-2.5* 27

WEST PHOENIX 

## 38

GOOD 

## 43

GOOD 

## 31

GOOD

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

*“ Ozone Health Watch ” means that the highest concentration of OZONE may approach the federal health standard.

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

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

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

## Exceptional Event, Phoenix, July 11, 2012 Appendix D



## Health Statements

Tuesday, 07/10/12 

## Unusually sensitive people should consider limiting prolonged or heavy

exertion outdoors.

Wednesday, 07/11/12 

## Unusually sensitive people should consider limiting prolonged or heavy

exertion outdoors.



## SYNOPSIS AND DISCUSSION

...An Ozone Health Watch remains in effect for today, Tuesday, July 10, 2012...

High pressure is in a favorable position to drive thunderstorms off of the Mogollon Rim and

towards the Valley. Such storms tend to be more electrical in nature due to the topography,

additional vertical movement and associated fricti on of the air molecules within the developing

storms. Such storms also tend to be less apt to generate wide-spread blowing dust coming off of

the more vegetated mountainous areas. Thus, it’s less likely that we will see significant PM10

levels over the next few days.

The subtle “shift” we’ve been waiting for has been underway. Ozone levels reached the

upper Moderate range under the east-northeast fl ow. Today, day 2 of the “shift” reveals lower

concentrations than 24-hr earlier. The forecast calls for a continuation of the northeast-tosouthwest flow. Thus, ozone concentrations should drop a bit more with highest levels towards

the southwest part of the forecast area (Buckeye) on Wednesday.

Check back tomorrow for more. Until then, have a good day. -J.Paul

MONITORING SITE MAPS

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

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

. j pg



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

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

http://www.airnow.gov/



# POLLUTION MONITOR READINGS FOR MONDAY, JULY 9, 2012



# O3 (OZONE)

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

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

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

Alamo Lake 

### 53 45

Apache Junction 

### 51 43

Blue Point 

### 72 90

Buckeye 

### 49 42

Casa Grande 

### 56 47

Cave Creek 

### 65 67

Central Phoenix 

### 59 50

Dysart 

### 52 44

Falcon Field 

### 61 54

Fountain Hills 

### 64 64

Glendale 

### 56 47

Humboldt Mountain 

### 63 61

North Phoenix 

### 63 61

Phoenix Supersite 

### 60 51

Pinal Air Park 

### 60 51

Pinnacle Peak 

### 71 87

Queen Valley 

### 65 67

Rio Verde 

### 69 80

South Phoenix 

### 58 49

## Exceptional Event, Phoenix, July 11, 2012 Appendix D



## 5 South Scottsdale 

### 67 74

Tempe 

### 60 51

Tonto Nat’l Mon. 

### 61 54

West Chandler 

### 59 50

West Phoenix 

### 56 47

Yuma 

### 48 41



# CO (CARBON MONOXIDE)

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

Central Phoenix 

### 0.4 5

Greenwood 

### 0.4 5

West Phoenix 

### 0.3 3



# PM-10 (PARTICLES)

SITE NAME MAX 24-HR VALUE (μg/m3) 

### MAX AQI AQI COLOR CODE

Apache Junction 

### 22.3 21

Buckeye 

### 35.1 32

Central Phoenix 

### 24.9 23

Combs School (Pinal County) 

### 45.6 42

Durango 

### 39.8 36

Dysart 

### 24.0 22

Glendale 

### 24.4 22

Greenwood 

### 30.8 28

Higley 

### 32.2 29

Maricopa (Pinal County) 

### 35.5 33

North Phoenix 

### 21.1 19

Phoenix Supersite 

### 21.6 20

South Phoenix 

### 32.6 30

Tempe 

### 22.4 20

West Chandler 

### 22.9 21

West Forty Third 

### NOT AVBL NOT AVBL NOT AVBL

West Phoenix 

### 27.7 25

Zuni Hills 

### 21.2 19



# PM-2.5 (PARTICLES)

(Some data derived from light-scattering equipment)



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

SITE NAME MAX 24-HR VALUE (μg/m3) 

### MAX AQI AQI COLOR CODE

Durango 

### 6.1 20

Dysart 

### 2.8 9

Estrella Mountain Park 

### 5.0 16

Glendale 

### 6.6 21

Phoenix Supersite 

### 3.4 11

North Phoenix 

### 6.3 20

South Phoenix 

### 4.9 16

Tempe 

### 6.4 21

Vehicle Emissions Lab 

### 3.0 10

West Phoenix 

### 8.2 27

## Exceptional Event, Phoenix, July 11, 2012 Appendix D



## 6 

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

Phoenix, AZ, pertaining to the July 11, 2012, dust storm event:

264

WWUS75 KPSR 120335

NPWPSR

URGENT - WEATHER MESSAGE

NATIONAL WEATHER SERVICE PHOENIX AZ

835 PM MST WED JUL 11 2012

AZZ028-120500-

/O.NEW.KPSR.DU.Y.0011.120712T0335Z-120712T0500Z/

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

FLORENCE

835 PM MST WED JUL 11 2012

...BLOWING DUST ADVISORY IN EFFECT UNTIL 10 PM MST THIS

EVENING...

THE NATIONAL WEATHER SERVICE IN PHOENIX HAS ISSUED A BLOWING DUST

ADVISORY...WHICH IS IN EFFECT UNTIL 10 PM MST THIS EVENING.

* AFFECTED AREA...NORTHERN PINAL COUNTY...INCLUDING FLORENCE...

COOLIDGE...HIGHWAY 79...INTERSTATE 10...AND CASA GRANDE.

* TIMING...VALID UNTIL 1000 PM MST.

* WINDS...WIDESPREAD WINDS OF 25 MPH...GUSTS TO 40 MPH.

* VISIBILITY...WIDESPREAD VISIBILITIES LESS THAN 3 MILES...LOCALLY BELOW 1

MILE.

* IMPACTS...RAPID CHANGES IN VISIBILITY ON AREA ROADS.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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

BLOWING DUST OR BLOWING SAND ON THE ROADWAY OR SEE IT

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

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

FOOT OFF THE BRAKE PEDAL.

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

&&

## Exceptional Event, Phoenix, July 11, 2012 Appendix D



## URGENT - WEATHER MESSAGE

NATIONAL WEATHER SERVICE PHOENIX AZ

1027 PM MST WED JUL 11 2012

AZZ023-027-120700-

/O.NEW.KPSR.DU.Y.0012.120712T0527Z-120712T0700Z/

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

1027 PM MST WED JUL 11 2012

...BLOWING DUST ADVISORY IN EFFECT UNTIL MIDNIGHT MST TONIGHT...

THE NATIONAL WEATHER SERVICE IN PHOENIX HAS ISSUED A BLOWING DUST

ADVISORY...WHICH IS IN EFFECT UNTIL MIDNIGHT MST TONIGHT.

* AFFECTED AREA...SOUTHERN AND SOUTHWESTERN PORTIONS OF THE PHOENIX

METROPOLITAN AREA...AND SOUTHWESTERN MARICOPA COUNTY.

* TIMING...THROUGH MIDNIGHT MST.

* WINDS...SUSTAINED 20-30 MPH...GUSTS TO 45 MPH.

* VISIBILITY...WIDESPREAD 2-3 MILES...LOCALLY BELOW 1 MILE.

* IMPACTS...RAPID CHANGES IN VISIBILITY...ESPECIALLY ALONG

INTERSTATES 8 AND 10...AND HIGHWAY 85.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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

BLOWING DUST OR BLOWING SAND ON THE ROADWAY OR SEE IT

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

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

FOOT OFF THE BRAKE PEDAL.

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

SPECIAL WEATHER STATEMENT

NATIONAL WEATHER SERVICE PHOENIX AZ

1035 PM MST WED JUL 11 2012

AZZ027-028-120615-

PINAL AZ-MARICOPA AZ1035 PM MST WED JUL 11 2012

...SIGNIFICANT WEATHER ADVISORY...

THE NATIONAL WEATHER SERVICE IN PHOENIX HAS ISSUED A

SIGNIFICANT WEATHER ADVISORY FOR...

SOUTH CENTRAL MARICOPA COUNTY IN SOUTH CENTRAL ARIZONA

EXTREME WEST CENTRAL PINAL COUNTY IN SOUTH CENTRAL ARIZONA

7

## Exceptional Event, Phoenix, July 11, 2012 Appendix D



## 8 UNTIL 1115 PM MST

AT 1032 PM MST...NATIONAL WEATHER SERVICE METEOROLOGISTS DETECTED A

STRONG THUNDERSTORM 8 MILES SOUTHWEST OF ESTRELLA SAILPORT...MOVING

WEST AT 20 MPH.

WIND GUSTS UP TO 50 MPH ARE EXPECTED WITH THIS STORM...ALONG WITH

HEAVY RAIN. GUSTY WINDS WILL SPREAD AHEAD OF THE STORM...AND WILL

ARRIVE WELL BEFORE THE RAIN.

LOCATIONS IMPACTED INCLUDE...

GILA BEND...

BIG HORN...

ESTRELLA...

SONORAN NATIONAL MONUMENT...

BOSQUE...

IF THIS STORM INTENSIFIES...A WARNING MAY BE NEEDED. STAY TUNED TO

NOAA WEATHER RADIO...LOCAL RADIO OR TV FOR THE LATEST UPDATES.

SOME UNSECURED OBJECTS WILL BE BLOWN AROUND...TREE LIMBS COULD BE

SNAPPED OFF...AND ISOLATED POWER OUTAGES WILL BE POSSIBLE. SEEK

SHELTER INDOORS UNTIL THE STORM PASSES.

BLOWING DUST IS POSSIBLE....ESPECIALLY ALONG INTERSTATE 8 AND

HIGHWAY 85. IF YOU ENCOUNTER 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. REMEMBER...PULL

A SIDE...AND STAY ALIVE.

## Exceptional Event, Phoenix, July 11, 2012 Appendix E



# Appendix E: Affidavit of Public Notice

1