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Assessment of Qualification for Treatment under the Arizona Natural and Exceptional 

Events Policy for the High Particulate (PM10) Concentration Events in the 

Phoenix Area on March 14, 2008 

Background

The Arizona Department of Environmental Quality (ADEQ) 

issues Dust Control Action Forecasts as part of the Natural 

Events Action Plan for the Phoenix area. On Thursday, March 

13, 2008, in response to a tightening pressure gradient ahead 

of a low pressure system and associated cold front 

approaching Arizona from the west, ADEQ air quality 

forecasters issued the Maricopa County Dust Control Action 

Forecast which called for a moderate risk of wind-blown dust 

for Friday, March 14th. In addition, ADEQ air quality 

forecasters issued a PM10 Health Watch for March 14, 2008, 

due to the possibility of strong winds and blowing dust 

throughout the Maricopa County area. The forecasts and 

advisories satisfy the requirement in 40 CFR 51.930(a)(1). 

The forecast for March 14th called for strong winds capable of 

producing wind-blown dust. This potential wind-blown dust 

event equated to a moderate risk of exceeding the PM10

National Ambient Air Quality Standards (NAAQS) in 

Maricopa County. During the late morning / early afternoon 

hours of March 14th, strong, gusty winds moved into the 

Phoenix Metro area from the west. All appropriate State 

Implementation Plan (SIP) control measures were in place 

during the event demonstrating, per 40 CFR 50.1(j), that the 

event “is not reasonably controllable or preventable.” A 

discussion of commonly employed Best Available Control 

Measures (BACM) for dust in Maricopa and Yuma counties 

can be found in “High Wind Exceptional Events and Control 

Measures for PM10 Areas” (see “References”). 

Strong winds were observed throughout portions of Maricopa 

County and the Phoenix Metro area on March 14, 2008. The 

initialization of the wind-blown dust event is evident in the 

Phoenix visible camera images as well as the Arizona 

Meteorological Network (AzMET), Maricopa County (MC), 

and National Weather Service (NWS) monitors (see Fig. 1). 

Gusty winds greater than 20 and 30 mph were reported 

between the 10:00 a.m. and 5:00 p.m. hours at several 

Phoenix area monitoring locations. In addition, Phoenix 

Goodyear Airport reported reduced visibility and a wind gust 

of 43 mph during the event. 

This significant event brought elevated ambient 

concentrations of PM10 to the Phoenix area. Due to the spatial 

variability of PM sources both within and outside of the 

Phoenix urban core, the PM10 NAAQS was only exceeded at 

the West 43rd Ave. monitor operated by Maricopa County (see 

Section 2 for more detail). The fact that ambient 

concentrations exceeded the NAAQS satisfies the criteria in 

40 CFR 50.1(j) that the event “affects air quality.” 

The following are the key PM10 monitor readings for the 

monitors examined in this report: 

Monitor (Operator/Type) AQS ID 24-hr Avg PM10 1-hr Max PM10 Max Time Flag** 

PHOENIX METRO AREA 

 West 43rd Ave (MC/TEOM) 04-013-4009* 251 1286 1300 RJ

 South Phoenix (MC/TEOM) 04-013-4003* 119 461 1300 None 

 Durango Complex (MC/TEOM) 04-013-9812* 92 310 1300 None 

 Greenwood (MC/TEOM) 04-013-3010* 71 151 1300 None 

 Higley (MC/TEOM) 04-013-4006* 51 140 0700 None 

 West Phoenix (MC/TEOM) 04-013-0019* 57 126 1300 None 

 Central Phoenix (MC/TEOM) 04-013-3002* 69 231 1300 None 

 JLG Supersite (ADEQ/TEOM) 04-013-9997* 40 62 1300 None 

 Coyote Lakes (MC/TEOM) 04-013-4014* 47 107 0700 None 

* EPA Air Quality System Identification Number 

** 24-hr PM10 concentration influenced by natural or exceptional event to be flagged 

Type Abbreviations: TEOM – Tapered Element Oscillating Microbalance Monitor (Continuous monitor) 

The preliminary findings from this analysis were presented at 

stakeholders meetings on November 19, 2008, and March 19, 

2009, in Phoenix, Arizona. Following the stakeholders 

meetings, ADEQ supplemented and finalized the analysis and 

a public comment period was held from October 15, 2009 

through November 13, 2009. This finalized document and 

any comments received are being submitted to EPA to satisfy 

the requirements in 40 CFR 50.14(c)(3)(i). 
Hr T(F)

V

R Dust Spd Gust Dir Hr T(F)

V

R Dust Spd Gust Dir Hr T(F)

V

R Dust Spd Gust Dir Hr 1

1 0 0 0 0 N/A 1 0 0 0 0 N/A 1 63 10 6 6 E 1 26.1

2 0 0 0 0 N/A 2 0 0 0 0 N/A 2 62 10 6 6 E 2 28.93 0 0 0 0 N/A 3 0 0 0 0 N/A 3 60 10 6 6 E 3 22.2 4 0 0 0 0 N/A 4 0 0 0 0 N/A 4 59 10 7 7 E 4 28.4

5 0 0 0 0 N/A 5 0 0 0 0 N/A 5 59 10 5 5 E 5 64.6

6 0 0 0 0 N/A 6 0 0 0 0 N/A 6 57 10 8 8 E with w/o 6 155

7 0 0 0 0 N/A 7 0 0 0 0 N/A 7 57 10 0 0 N Monitor: Event Event 7 146

8 61 60 9 9

W 8 0 0 0 0 N/A 8 61 10 0 0 N 1-W43RD 251 69 8 134

9 66 40 9 9 S

W 9 0 0 0 0 N/A 9 65 10 6 6 E 9 188

10 70 30 7 7

W 10 70 20 15 23 S

W 10 70 10 5 5 S

W 10 329

11 73 20 6 6 SW 11 73 20 16 23 SW 11 77 10 11 20

W > NAAQS < NAAQS 11 355

12 82 15 14 29

W 12 79 20 18 23

W 12 79 10 21 29

W 12 1052

1 86 10 18 34

W 1 81 20 20 26

W 1 81 10 21 30

W 1 1270

2 86 15 25 43

W 2 82 20 21 26

W 2 82 10 25 30

W 2 1286

3 84 20 14 23

W 3 82 20 20 25

W 3 82 10 23 23

W 3 374

4 84 20 17 17 S

W 4 81 20 14 23 S

W 4 82 10 17 24

W 4 87 5 82 40 17 17 SW 5 82 20 11 21

W 5 81 10 13 23

W 5 57.1 wnd @3m agl / Dir corrected to true north

6 81 40 11 11

W 6 81 20 11 11 SW 6 80 10 14 14

W 6 23.6 HIGHLIGHTING Col. Parameter

7 75 40 6 6 *VR 7 75 20 5 5

W 7 77 10 7 7

W 7 37.1 Max Wind T(F) Temp. (Deg. F.)

8 0 0 0 0 N/A 8 0 0 0 0 N/A 8 76 10 9 9 S

W 8 40.8 > 15 mph RH Rel Humidity % 9 70 20 11 11 SW 9 0 0 0 0 N/A 9 72 10 11 11 SW 9 86.4 >25 mph Rn Rain (Inches/hr)

10 0 0 0 0 N/A 10 0 0 0 0 N/A 10 73 10 10 10

W 10 93.1 HR - Time (End) Spd Avg Speed mph

11 0 0 0 0 N/A 11 0 0 0 0 N/A 11 69 10 10 10

W 11 73.4 A.M. Max Max Speed mph

12 0 0 0 0 N/A 12 0 0 0 0 N/A 12 67 10 7 7 W 12 72.9 P.M. Dir Wind Dir. (from)

Hr T(F) PM Spd Max Dir Hr T(F) PM Spd Max Dir Hr T(F) PM Spd Max Dir 03/14/2008 - 12z 

1 69 26 5 9S

W 1 63 63 1 4

W 1 70 19 5 12 S

W

2 68 28 6 10 S

W 2 64 66 3 10 S

W 2 68 28 4 11 S

W

3 66 22 5 8 W 3 66 43 6 11

W 3 67 22 4 11 SW

4 64 28 5 7S

W 4 62 30 1 7S

W 4 64 24 3 8S

W

5 58 64 3 9 NE 5 58 63 2 6 E 5 60 35 1 6 E Yr Sea

6 57 154 5 8 E 6 56 67 2 6 E 6 58 46 2 5E 5 8

7 57 145 4 11 E 7 56 68 2 8 E 7 56 61 2 6E 9 98 59 133 2 6 E 8 62 132 2 4 E 8 59 82 1 4 SE 11 11

9 64 187 2 5 NE 9 71 80 0 3 NE 9 65 49 2 11 S

W 15 13

10 73 328 7 23

W 10 74 117 8 20

W 10 70 75 9 22 S

W 19 19

11 77 355 12 24

W 11 76 90 13 24

W 11 73 66 12 23

W 29 28

12 79 1051 16 31

W 12 78 216 15 29

W 12 76 72 11 28

W 44 46

1 82 1270 18 36

W 1 80 205 15 34

W 1 79 106 13 28

W 65 63

2 83 1286 19 36

W 2 81 310 19 36

W 2 81 125 14 31

W 91 82

3 84 374 14 31

W 3 82 127 15 41

W 3 81 121 14 36

W 121 107

4 84 87 12 26

W 4 84 32 13 27

W 4 81 36 11 25

W 139 125 3/14 - 10:45AM 3/14 - 11:

5 83 57 12 24

W 5 83 28 12 30

W 5 80 25 11 24 S

W 157 134

6 81 23 10 20

W 6 81 27 9 19

W 6 80 27 9 21

W 192 194

7 77 37 6 14

W 7 77 35 6 14

W 7 78 35 4 10

W 227 220

8 75 40 8 15 SW 8 73 67 7 14

W 8 75 50 4 15 SW 313 313

9 74 86 11 22 S

W 9 72 92 9 18 S

W 9 73 66 5 18 S

W

10 72 93 10 22 SW 10 70 89 7 16

W 10 70 65 4 14

W

11 67 73 6 11

W 11 66 81 6 11

W 11 68 67 5 13

W

12 66 72 5 11 SW 12 62 80 4 7 W 12 67 66 5 10

W

3/14 - 10:45AM 3/14 - 11:

Hr T(F) PM Spd Max Dir Hr T(F) PM Spd Max Dir Hr T(F) RH Rn Spd Max Dir Hr T(F) RH Rn Spd Max Dir

1 58 82 2 6 N 1 63 43 3 7 E 1 63 34 - 3 6 SE 1 53 49 - 5 6 SE2 57 68 2 6 N 2 61 39 3 6 E 2 61 35 - 3 6 SE 2 54 44 - 5 7 SE3 55 58 2 5 N 3 59 41 2 6 E 3 60 34 - 3 6 E 3 56 36 - 5 7 E4 53 24 3 8 N 4 58 42 4 7 E 4 60 33 - 3 5 E 4 55 38 - 6 8 E5 52 32 2 6 N 5 57 36 2 5 E 5 58 34 - 3 6 E 5 52 45 - 6 8 SE 3/14 - 10:45AM 3/14 - 11:6 51 45 3 7 NE 6 56 36 4 6 E 6 58 34 - 3 6 E 6 51 48 - 5 8 E7 50 50 2 7 N 7 56 33 3 6 E 7 58 33 - 5 7 SE 7 53 41 - 5 7 E8 54 106 1 5 N 8 64 38 2 6 SE 8 60 33 - 4 7 SE 8 55 42 - 5 8 SE9 66 77 1 4 NE 9 71 54 3 6 E 9 64 29 - 4 7 SE 9 60 43 - 7 10 SE

10 71 55 1 6N 10 76 55 2 17 S

W 10 69 27 - 3 6 SE 10 67 30 - 7 10 S

11 76 35 1 10 S

W 11 78 105 12 25

W 11 73 22 - 2 6 N 11 72 23 - 7 12 S

W

12 79 22 6 21 SW 12 80 127 15 30

W 12 78 12 - 9 18

W 12 76 15 - 10 20

W

1 81 52 11 25

W 1 81 149 16 30

W 1 79 10 - 11 21

W 1 78 10 - 13 20

W

2 82 61 11 30

W 2 82 230 20 37

W 2 81 7 - 13 23

W 2 80 9 - 13 25

W

3 82 98 14 32

W 3 82 159 19 37

W 3 81 7 - 12 23

W 3 80 9 - 13 21

W 3/14 - 10:45AM 3/14 - 11:

4 82 31 12 28

W 4 83 33 14 28

W 4 82 9 - 9 18

W 4 80 9 - 12 20

W

5 82 17 10 26

W 5 83 28 13 29

W 5 81 11 - 9 16

W 5 79 10 - 14 23

W

6 81 13 10 21

W 6 81 31 12 24

W 6 80 11 - 8 14

W 6 77 11 - 12 19

W

7 74 13 4 14

W 7 77 30 7 16

W 7 78 12 - 4 10

W 7 73 13 - 8 15

W

8 66 41 0 2N

W 8 74 47 6 16

W 8 75 12 - 4 10 S

W 8 69 14 - 5 9

W

9 62 44 0 4S 9 73 64 7 16 S

W 9 73 11 - 5 9S

W 9 65 15 - 5 9

W

10 61 32 0 4 NE 10 71 77 6 15

W 10 73 11 - 4 9S

W 10 64 16 - 6 11

W

11 57 33 0 3N 11 69 75 8 19

W 11 70 13 - 3 9S

W 11 63 16 - 5 10 S

W

12 55 42 2 4 N 12 68 74 8 16

W 12 43 65 - 3 7 E 12 60 20 - 7 11 SW

SUM

A low prestrong wwinds on portions Harbor Ingusts to Goodyeahigh as 4winds coPM10 lev

(looking northeast)

SOUTH MOUNTAIN CAMELBACK MTN

(looking south)

Historical Distribution

AZMET Monitoring Locations

See http://ag.arizona.edu/azmet/

F

Ke

Eve

1

WIND & 

PM10 

DATA

NWS-Phx Sky Harbor

NWS-Phx Sky Harbor

NWS-Goodyear Airport

MC - WEST PHOENIX

75%

 2.5%

22-Queen Creek

50%

 5%

PHX METRO - MESA

 1.0%

MONITORS: Column Index

Freq.

(looking south)

NWS-Glendale Municipal Airport

NWS-Goodyear Airport

NWS-Glendale Airport

 0.5%

Min

25%24-Hr. Avg PM1010%

MC - COYOTE LAKES

Event Contrib. Analysis

Hourly PM10 Conc. (μg/m3

)

1-W43RD

Cum. Mon 1

MONITORS:

Pink=Event Contrib.

Conclusion: As shown above, the PM10 

concentration wouldhave been below theNAAQS "BUT FOR" the event contribution (hours highlighted in pink).

90%

Max

99.5%

WHITE TANK MTN

(looking west)

ESTRELLA MTN

Conclusion: Flagged Value is exceptional

MC - COYOTE LAKES

MC - WEST PHOENIX

127530 (112.31Wx33.67N) 16329 (112.05Wx33.46N)

MC - CENTRAL PHOENIX

AZMET - 

251

in nature (ie greater than 95% of all data)

29-Mesa

AZMET -

MC - CENTRAL PHOENIX

SOUTHEAST PHOENIX

95%

97.5%

Flagged

Value

99.0%

5-Yr. Dist. of Values (μg/m3

)

Sea - Data for Spring

 season only (5-Yrs)

1-W43RD Yr - All Data (5-Yrs)

16477 (112.14Wx33.48N)

NOAA - Surface Anal

y

16659 (112.14Wx33.41N)

MC - WEST FORTY THIR

MC - WEST FORTY THIR

MC - DURANGO COMPLEX

16375 (112.12Wx33.43N)

MC - DURANGO COMPLE

X
Assessment of March 14, 2008 event (Cont.) 

- 4 - 

Assessment under the Technical Criteria Document (TCD)

1. Properly qualify and validate the air quality measurement 

to be flagged. As this was not a filter sampling date (1-in-6 

run day), only data from the continuous analyzers were 

examined. The air quality monitoring data were reviewed by 

the agency responsible for operation of the monitor. All 

hourly PM10 readings from the West 43rd Ave. monitoring site 

were valid for March 14th. Audits of the analyzers revealed 

operations were within acceptable tolerance. No local sources 

were reported as significantly contributing to the air quality 

episode. Exceedances of the NAAQS were recorded at the 

West 43rd Ave. monitoring site operated by Maricopa County. 

2. Review suspected contributing sources. The NWS, 

AzMET, and MC surface data for Arizona, along with the 

visible camera images in Phoenix, provide a good explanation 

of the meteorological conditions that were in place on March 

14th. Strong westerly winds were occurring in the Phoenix 

area due to a low pressure system approaching from the west 

with a cold front situated west of Arizona. The plot of hourly 

PM10 concentration data and max winds in the upper right 

corner of Figure 1 confirms the nearly identical timing of 

elevated PM10 and strong wind gusts at the West 43rd Ave. 

monitor. The high wind event was a regional phenomenon 

that affected the entire Phoenix Metro area. However, PM 

sources are highly variable across space; therefore, the 

locations of higher PM10 concentrations (namely the Salt 

River channel) are likely an indication that these locations (or 

areas upwind of these locations) contain greater sources of 

PM than other locations within the Phoenix Metropolitan 

area. While no specific source allocation can be determined 

for this particular day, the 2005 ADEQ revised PM10 SIP for 

the Salt River area (attached) contains modeled source 

contributions on high wind days (see section 4.2 – Source 

Categories). Results estimate that approximately 76% of 

PM10 concentrations can be attributed to windblown dust, of 

which 21% is from agricultural fields, 15% from alluvial 

channels, and 21% from vacant lots. It is not clear whether 

similar source allocations can be assumed for this March 14, 

2008, high wind event. 

3. Examine all air quality monitoring information. Data from 

all monitors in the network were reviewed. Monitors from 

the affected areas are summarized in the table in the 

Background section of this assessment. Pursuant to 40 CFR 

50.14(c)(3)(iii)(C), the “Historical Distribution” Table in 

Figure 1 has been included to demonstrate that the event is 

associated with a measured concentration in excess of normal 

historical fluctuations, including background (i.e., 

concentrations greater than the 95th percentile). Additionally, 

the winds associated with the elevated PM10 concentrations 

may be characterized as unusual as described in “Impact of 

Exceptional Events’ ‘Unusual Winds’ on PM10

Concentrations” (see “References”). 

4. Examine the meteorological conditions before and during 

the event. The meteorological data are summarized in Figure 

1. The wind data are highlighted yellow if the max wind 

speed in the hour exceeds 15 mph and orange if it exceeds 25 

mph. As can be seen in Figure 1, wind speeds did not pick up 

in central Arizona until approximately 10:00 or 11:00 a.m., 

when several stations reported gusty winds that approached 

30 and even 40 mph at times. This timing corresponds to the 

onset of elevated PM10 concentrations recorded at the West 

43rd Ave. monitoring site, which remained elevated through 

the afternoon hours until the winds decreased to below 20 

mph. 

5. Perform a qualitative attribution to emission source(s). All 

evidence indicates the elevated PM10 concentrations in the 

Phoenix area can be attributed to soil emissions that were 

transported over portions of the Phoenix Metro area in 

Maricopa County. No source specific emission allocation is 

possible based on the data available for analysis. The hourly 

concentration data do not show any significant source other 

than the wind-blown dust event occurring on March 14, 2008. 

Observational reports of reduced visibility throughout 

portions of Phoenix are further proof that the elevated PM10

concentrations were attributed to soil emissions transported 

by high winds. These reports, in addition to the visual 

evidence of reduced visibility seen in the lower right portion 

of Figure 1, provide proof that the elevated PM10

concentrations in Phoenix can be attributed to soil emissions. 

6. Estimation of Contribution from Source or Event. The 

primary source appears to be wind-blown dust over central 

Arizona for which there is not an effective or efficient method 

to estimate the relative contributions from specific sources. 

The demonstration analysis contained in this report 

establishes the linkage between the measurements to be 

flagged and the event, thus satisfying the requirement in 40 

CFR 50.14(c)(3)(iii)(B). Pursuant to 40 CFR 

50.14(c)(3)(iii)(D), the “Event Contrib. Analysis” Table in 

Figure 1 has been included to demonstrate that there would 

have been no exceedance or violation but for the event (i.e., 

the contribution during the event overwhelmed the 24-hour 

average). 

7. Determination that a Natural or Exceptional Event 

Contributed To an Exceedance. Based on this analysis, the 

event satisfies the requirement in 40 CFR 50.1(j) that the 

elevated concentration at West 43rd Ave. was attributed to a 

natural event. 

Conclusion

Transport of dust from soils by high winds. The elevated 

PM10 event on March 14, 2008, in Maricopa County was the 

result of the transport of dust and soils from high winds that 

suspended natural soils and soils from areas where Best 

Available Control Measures are in place and should be 

flagged for air quality planning purposes. The “high wind” 

(RJ) flag should be applied to the monitor readings indicated 

in the table at the beginning of this report, as the monitor 

would have been below the NAAQS but for the contribution 

of the event. 
ATTACHMENTS AND REFERENCES 

FOR EXCEPTIONAL EVENTS ANALYSIS 

The following are supplemental materials helpful in understanding the exceptional 

event summarized in the main report. In addition, the reader is referred to the 

following references. 

REFERENCES

Arizona Department of Environmental Quality (ADEQ), Air Quality Exceptional and 

Natural Events Policy, Policy Number 2009.002 (April 28, 1999; revised January 10, 

2006 and June 22, 2007). 

Arizona Department of Environmental Quality (ADEQ), Technical Criteria Document 

for Determination of Natural Exceptional Events for Particulate Matter Equal to or Less 

Than Ten Microns in Aerodynamic Diameter (PM10) (May 31, 2000). 

Arizona Department of Environmental Quality (ADEQ), Technical Criteria Document 

for Determination of Natural and Exceptional Events (December 12, 2005). 

Arizona Department of Environmental Quality (ADEQ), Impact of Exceptional Events 

‘Unusual Winds’ on PM10 Concentrations (October 14, 2009). 

Arizona Department of Environmental Quality (ADEQ), High Wind Exceptional Events 

and Control Measures for PM10 Areas (October 14, 2009). 

Environmental Protection Agency (EPA), The Treatment of Data Influenced by 

Exceptional Events (Exceptional Event Rule), 73 FR 70597; 40 CFR Parts 50 and 51 

(November 21, 2008). 
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.epa.gov/airnow/aqibroch

 

*LINK TO EXCEEDANCE & HEALTH STATEMENT INFO FOR THE 2006-07 & 2007-08 FORECAST SEASONS*

AIR QUALITY FORECAST FOR FRIDAY, MARCH 14, 2008

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

for areas within and bordering Maricopa County in Arizona

 

* O3 = Ozone CO = Carbon Monoxide PM-10 = Particles 10 microns & smaller PM-2.5 = Particles smaller than 2.5 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 outflow from thunderstorms are possible.

FORECAST 

DATE

NOTICES 

(*SEE BELOW 

FOR DETAILS) 

AIR POLLUTANT 

YESTERDAY 

WED 03/12/2008

NONE 

Highest AQI Reading/Site 

(Preliminary data only) 

TODAY 

THU 03/13/2008

NONE 

TOMORROW 

FRI 03/14/2008

PM-10 HEALTH 

WATCH 

EXTENDED 

SAT 03/15/2008

NONE 

O3* 42 

APACHE JUNCTION 

51 

MODERATE 

47 

GOOD 

35 

GOOD 

CO* 16 

GREENWOOD 

15 

GOOD 

11 

GOOD

09 

GOOD 

PM-10* 58 

WEST FORTY THIRD 

68 

MODERATE

94 

MODERATE

74 

MODERATE 

PM-2.5* 38 

PHOENIX SUPERSITE 

31 

GOOD

27 

GOOD

24 

GOOD
Health message for Thursday, Mar 13: Unusually sensitive people should consider 

reducing prolonged or heavy exertion. 

Health message for Friday, Mar 14: Unusually sensitive people should consider 

reducing prolonged or heavy exertion. 

Synopsis and Discussion

A PM-10 HEALTH WATCH HAS BEEN ISSUED FOR FRIDAY MARCH 14

Major changes in local weather conditions are on tap the next few days as the mid-latitude storm track 

migrates south over the area. Westerly winds aloft over the Valley are advertised to reach 50+ mph at the 

10K’ level and near 100 mph at the 18K’ level on Friday; since the predicted mixing depth is near 9K’, 

some of this momentum will have an avenue for reaching the surface. Areas of blowing and suspended dust 

are therefore likely as is the potential for transported dust from desert areas upwind of the metro area. 

Since PM-10 (coarse particle) levels may approach unhealthy levels, a PM-10 Health Watch has been 

issued for Friday. After a very breezy day on Saturday, an upper level trough and surface cold frontal 

passage are forecast to occur on Sunday and will be accompanied by showers and a few thunderstorms – 

along with gusty winds and much colder temperatures. -Reith 

 

MONITORING SITE MAPS: STATIC MAP – http://www.azdeq.gov/environ/air/monitoring/images/winter.jpg

 INTERACTIVE MAPS – http://aqwww.maricopa.gov/AirMonitoring/SitePollutionMap.aspx

 http://www.airnow.gov/

POLLUTION MONITOR READINGS FOR WEDNESDAY, MARCH 12, 2008 

O3 (OZONE) 

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

Apache Junction 54 42 

Blue Point 42 33 

Central Phoenix 43 34 

Fountain Hills 49 38 

North Phoenix 32 25 

Phoenix Supersite 47 37 

Pinnacle Peak 45 35 

South Phoenix 50 39 

South Scottsdale 43 34 

West Phoenix 45 35 

CO (CARBON MONOXIDE) 

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

Buckeye 0.3 04 

Central Phoenix 0.8 09 

Dysart 0.4 05 

Glendale 0.6 07 

Greenwood 1.4 16 

Mesa 0.5 06 

North Phoenix 0.6 07 

Phoenix Supersite 1.2 14 

South Phoenix 0.8 09 

South Scottsdale 0.4 05 

Tempe 0.7 08 

West Chandler 0.5 06 

West Indian School 1.3 15 

West Phoenix 1.0 11 
PM-10 (PARTICLES)

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

Buckeye 48 44 

Central Phoenix 35 32 

Coyote Lakes 22 20 

Durango 56 51 

Greenwood 48 44 

Higley 42 39 

Maricopa (Pinal County) 70 58 

Phoenix Supersite 31 29 

Queen Creek (Pinal County) 54 50 

South Phoenix 46 43 

West Forty Third 70 58 

West Phoenix 40 37 

PM-2.5 (PARTICLES) 

(Some data derived from light-scattering equipment) 

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

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

Durango 11.2 36 

Dysart 3.4 11 

Estrella Mountain Park 6.1 20 

Phoenix Supersite 11.8 38 

Vehicle Emissions Lab NOT AVBL NOT AVBL NOT AVBL 

West Phoenix 11.4 37 

LOCAL AIR POLLUTANTS IN DETAIL 

O3 (OZONE): 

Description – This is a secondary pollutant that is formed by the reaction of other primary 

pollutants (precursors) such as VOCs (volatile organic compounds) and NOx (Nitrogen Oxides) 

in the presence of heat and sunlight. 

Sources – VOCs are emitted from motor vehicles, chemical plants, refineries, factories, and 

other industrial sources. NOx is emitted from motor vehicles, power plants, and other sources of 

combustion. 

Potential health impacts – Exposure to ozone can make people more susceptible to respiratory 

infection, result in lung inflammation, and aggravate pre-existing respiratory diseases such as 

asthma. Other effects include decrease in lung function, chest pain, and cough. 

 Unit of measurement – Parts per billion (ppb). 

 Averaging interval – Highest eight-hour period within a 24-hour period (midnight to midnight). 

Reduction tips – Curtail daytime driving, refuel cars and use gasoline-powered equipment as late 

in the day as possible. 
CO (CARBON MONOXIDE): 

Description – A colorless, odorless, poisonous gas formed when carbon in fuels is not burned 

completely. 

Sources – In cities, as much as 95 percent of all CO emissions emanate from automobile exhaust. 

Other sources include industrial processes, non-transportation fuel combustion, and natural 

sources such as wildfires. Peak concentrations occur in colder winter months. 

Potential health impacts – Reduces oxygen delivery to the body’s organs and tissues. The health 

threat is most serious for those who suffer from cardiovascular disease. 

 Unit of measurement – Parts per million (ppm). 

 Averaging interval – Highest eight-hour period within a 24-hour period (midnight to midnight) 

 Reduction tips – Keep motor vehicle tuned properly and minimize nighttime driving. 

 

PM-10 & PM-2.5 (PARTICLES): 

Description – The term “particulate matter” (PM) includes both solid particles and liquid droplets 

found in air. Many manmade and natural sources emit PM directly or emit other pollutants that 

react in the atmosphere to form PM. Particles less than 10 micrometers in diameter tend to pose 

the greatest health concern because they can be inhaled into and accumulate in the respiratory 

system. Particles less than 2.5 micrometers in diameter are referred to as “fine” particles and are 

responsible for many visibility degradations such as the “Valley Brown Cloud” (see 

http://www.phoenixvis.net/). Particles with diameters between 2.5 and 10 micrometers are referred 

to as “coarse”. 

Sources – Fine = All types of combustion (motor vehicles, power plants, wood burning, etc.) and 

some industrial processes. Coarse = crushing or grinding operations and dust from paved or 

unpaved roads. 

Potential health impacts – PM can increase susceptibility to respiratory infections and can 

aggravate existing respiratory diseases, such as asthma and chronic bronchitis. 

 Units of measurement – Micrograms per cubic meter (ug/m3) 

 Averaging interval – 24 hours (midnight to midnight). 

 Reduction tips – Stabilize loose soils, slow down on dirt roads, carpool, and use public transit. 

{Updated 09/24/2007}

 
ADEQ AIR POLLUTION HEALTH WATCH

ISSUANCE NOTICE 

Issuance Date and Time: Thursday, March 13, 2008 10:00 a.m. 

Valid for Date(s): Friday, March 14, 2008 

Pollutant: COARSE PARTICLES (PM-10) 

Message: Blowing and suspended dust due to strong 

and gusty winds may cause concentrations of 

coarse particles to approach unhealthy levels 

on Friday. 

Detailed air quality forecast information is available on:

• The internet at www.azdeq.gov

• A telephone recording at 602-771-2367 

 

Duty Forecaster: Christopher Reith 520-770-3172 

 Joe Paul 602-771-2363 

 Bryan Paris 602/771-7665 

 CKR 12/06/2007 
MARICOPA COUNTY 

DUST CONTROL ACTION FORECAST

ISSUED THURSDAY, MARCH 13, 2008

Three-day weather outlook:

 

tttttttttttttttttttt 

R I S K F A C T O R S

The broad low-amplitude ridge aloft currently over the local forecast area will give way to a strengthening and then amplifying

mid-latitude storm track on Friday and thru the weekend. A strong westerly wind event looks likely on Friday and areas of

blowing dust are possible by early afternoon; a MODERATE risk has been posted. A breezy to marginally windy day is 

expected on Saturday ahead of a strong trough and cold front; showers and thunderstorms are possible on Sunday with the frontal

and trough passage. 

 WINDS STAGNATION RISK LEVEL

Day #1: Fri 03/14/2008 

+ =

 

 

Westerly 20-30 mph 

with gusts near 40 

mph. 

Little if any stagnation 

expected. 

 MODERATE 

 

Day #2: Sat 03/15/2008 + = 

South to southwesterly 

15-25 mph.

Little if any stagnation 

expected.

 

 LOW 

 

 

Day #3: Sun 03/16/2008 + = 

Southwest to westerly 

10-20 mph except 

strong and gusty near 

thunderstorms. 

Little if any stagnation 

expected. 

 MODERATE 

 

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

help reduce dust pollution. To review the complete air quality forecast for the Phoenix metropolitan area 

and the health effects of air pollution, please see ADEQ's Air Quality Forecast at 

http://www.azdeq.gov/environ/air/ozone/ensemble.pdf, or call 602-771-2367 for recorded forecast 

information. 
03/14/2008 - ADDITIONAL GRAPHS

West 43rd - PM 10 vs. Wind Speed

0

200400600800

100012001400

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3/14/2008

PM Concentration (μg/m^3)

051015202530354045

Wind Speed (mph)

PM10Max Wind

Durango - PM 10 vs. Wind 

0

200400600800

1000120014001600

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3/14/2008

PM Concentration (μg/m^3)

PM10Max Wind

South Phoenix - PM 10 vs. Wind Speed

0

200400600800

1000120014001600

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3/14/2008

PM Concentration (μg/m^3)

051015202530354045

Wind Speed (mph)

PM10Max Wind

Greenwood - PM 10 vs. Win

0

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100012001400

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3/14/2008

PM Concentration (μg/m^3)

PM10Max Wind
Phoenix Area PM10 and Meteorological Monitors 

Source: US EPA, ADEQ, & Google Earth 
Salt River Area PM10 and Meteorological Monitors 

Source: US EPA, ADEQ, & Google Earth 
26

CHAPTER 4: OVERVIEW OF PM10 CONTROL MEASURES 

4.1 INTRODUCTION 

Chapter 1.2.2 of this SIP ("Regulatory History of the Metropolitan Maricopa PM10 Nonattainment 

Area") notes that on July 25, 2002, EPA approved the Maricopa Serious PM10 Nonattainment Area, 

and granted Arizona's request, in accordance with CAA § 188(e), to extend the CAA deadline for 

attainment of the annual and 24-hour PM10 standards from December 31, 2001, to December 31, 

2006 (67 FR 48718). 

Because the attainment deadline for this plan revision is also December 31, 2006, and the 

measures must be applied to all similar sources throughout the Phoenix Nonattainment Area (see 

67 FR 44369, July 2, 2002), the control strategies must meet the "Most Stringent Measures" test, as 

well as the “Best Available Control Measures/Technology” test. In its July 25, 2002, approval of the 

Maricopa County Plan, EPA defined “most stringent measures” (MSMs) as the most stringent 

measures included in any state implementation plan, or being implemented in any state, that are 

economically and technologically feasible for the nonattainment area in question. “Best Available 

Control Measures” (BACM) must be applied in serious nonattainment areas, also taking into 

account the economic and technological feasibility of each measure. 

This chapter details the proposed BACM and MSM that were evaluated for each significant source 

category. 

4.2 SOURCE CATEGORIES 

The Salt River Study Area 2002 base year emissions inventory is described in Chapter 3.0 and the 

TSD’s Chapter 4.0. The 2002 emissions source category contributions to ambient PM10 are 

depicted in Table 4.2.1. The average concentrations are derived from the modeled concentrations 

outlined in the TSD, Chapter 6. 

Assumptions used to calculate trackout emissions appear in Appendix K “Methodology for 

Weighting Trackout Emissions” and Appendix P “Mapping Weighted Trackout Emissions into 

Predicted Concentrations” of the October 2004 TSD. Calculation methodology for street sweeping 

emissions reductions appears in Appendix L “Street Sweeping Reductions” of the October 2004 

TSD. 

Table 4.2.1 2002 Salt River Study Area Source Category Contributions to Ambient PM10

Concentrations 

Average Low Wind 

Day Contribution 

Average High Wind 

Day Contribution 

Highest 

Contribution(μg/m3) Source Category Percentage 

Contribution 

Percentage 

Contribution 

Low Wind 

Day 

High Wind 

Day 

Industrial Sources 25.9% 8.3% 60.2 31.8 

 Point Emissions 2.7% 1.1% 5.3 3.0 

 Area Emissions 23.2% 7.2% 54.9 28.8 

Construction 5.8% 0.9% 6.0 4.4 

Area Sources 4.2% 0.7% 8.0 3.1 

 Unpaved Parking Lots 1.7% 0.2% 0.8 1.4 

 Unpaved Shoulders 2.5% 0.4% 7.2 1.7 
27

Table 4.2.1 2002 Salt River Study Area Source Category Contributions to Ambient PM10

Concentrations 

Average Low Wind 

Day Contribution 

Average High Wind 

Day Contribution 

Highest 

Contribution(μg/m3) Source Category Percentage 

Contribution 

Percentage 

Contribution 

Low Wind 

Day 

High Wind 

Day 

Roads & Trackout 63.7% 13.5% 73.6 42.7 

 Freeway 0.4% 0.2% 0.7 0.4 

 Primary Roads 43.6% 9.3% 44.8 33.3 

 Secondary Roads 7.5% 1.5% 6.9 1.5 

 Trackout 12.1% 2.5% 21.2 7.5 

Agricultural Tillage 0.4% NA 0.2 NA 

Windblown Dust NA 76.7% NA 290.1 

 Agricultural Fields NA 21.3% NA 84.9 

 Alluvial Channels NA 14.9% NA 79.5 

 Construction NA 3.5% NA 14.0 

 Industrial NA 7.3% NA 33.6 

 Disturbed Areas NA 5.2% NA 25.9 

 Stockpiles NA 3.6% NA 12.6 

 Vacant Lots NA 20.9% NA 39.6 

Note: Bold concentrations exceed the 5 μg/m3 threshold for significant sources.

In Table 4.2.2, the modeled contributions for each of the source categories are given for the 2006 

attainment case. These percentages are similar to the 2002 case, but with several significant 

differences. For example, the windblown contribution decreases from 77% to 59% from 2002 to 

2006. 

Table 4.2.2 Salt River Study Area Source Category Contributions to Ambient PM10 

Concentrations for the 2006 Attainment Case 

Average Low Wind Day 

Contribution 

Average High Wind Day 

Contribution 

Source Category 

Percentage Contribution Percentage Contribution 

Industrial Sources 29.7% 12.1% 

 Point Source Emissions 4.4% 3.1% 

 Area Emissions 25.2% 8.9% 

Construction 5.2% 1.8% 

Area Sources 7.1% 2.1% 

 Unpaved Parking Lots 0.5% 0.6% 

 Unpaved Shoulders 6.6% 1.5% 

Roads & Trackout 58.0% 24.7% 

 Freeway 0.9% 0.4% 

 Primary Roads 48.3% 21.6% 

 Secondary Roads 6.8% 1.9% 

 Trackout 2.0% 0.7% 

Agricultural Tillage 0.1% NA 

Windblown Dust NA 59.4% 

 Agricultural Fields NA 8.9% 

 Alluvial Channels NA 15.4% 

 Construction NA 4.2% 

 Industrial NA 6.7% 

 Disturbed Areas NA 10.1% 

 Stockpiles NA 5.9% 

 Vacant Lots NA 8.4%