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Review of Evidence Regarding 

Claimed Exceptional Events 

Leading to 24-hour PM2.5

Exceedances 

Shasta County, CA

June 23, 2008

July 23, 2008

Plumas County, CA

June 23, 2008

June 26, 2008

July 11, 2008

July 19, 2008

July 23, 2008

US Environmental Protection Agency

Region 9

March 11, 2010
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Contents

1.0 Introduction...........................................................................................................................3

2.0 Summary of the Events.........................................................................................................3

3.0 Requirements of the Exceptional Events Rule......................................................................5

4.0 Criteria Set Forth in 40 CFR § 50.1(j)..................................................................................6

4.1 Affects Air Quality............................................................................................................6

4.2 Not Reasonably Controllable or Preventable ..................................................................10

4.3 Natural Event...................................................................................................................10

5.0 Clear Causal Relationship...................................................................................................11

6.0 Concentrations in Excess of Normal Historical Fluctuations.............................................15

7.0 No Exceedance But For the Event......................................................................................18

8.0 Procedural Requirements....................................................................................................20

9.0 Conclusion ..........................................................................................................................21

10.0 Citation of Exceptional Event Request Documentation..................................................21

Tables

Table 1: Summer 2008 PM2.5 Flagged Events Under Review......................................................5

Table 2: Federal Wildland Fire Incidents in Northern California – June 20 to September 7, 

2008.........................................................................................................................8

Table 3. Levoglucosan Levels, Portola - Summer 2007 and 2008..............................................14

Table 4. Portola Monitor: Highest PM2.5 concentrations, Summers (Jun - Aug) 2000-2008................15

Table 5. Quincy Monitor: Highest PM2.5 concentrations, Summers (Jun - Aug) 2000-2008................16

Table 6. Redding Monitor: Highest PM2.5 concentrations, Summers (Jun - Aug) 2000-2008...............17

Figures

Figure 1: Summer 2008 California Wildfires and Presidentially Declared Emergency Areas................4

Figure 2: Major Federal Wildfires Burning in California June 20 – September 7, 2008, and PM2.5 (FRM, 

FEM, and BAM) Monitoring Sites in California.....................................................................7

Figure 3: Wildfires Ignited June 20 – July 23, 2008 near the Redding, Portola, and Quincy PM2.5

monitors..................................................................................................................11

Figure 4: PM2.5 concentrations recorded at Redding, Portola, and Quincy, June – August 2008............12

Figure 5. NOAA Satellite Image, June 23, 2008...................................................................13

Figure 6. Wood Burning Markers (Levoglucosan, Galactosan, Mannosan) at Portola during the Summer 

2008 Wildfires, compared to Summer Average. ..................................................................14

Figure 7. Distribution of Summer (June – August) PM2.5 FRM Concentrations at Portola, 2000-

2008.......................................................................................................................16

Figure 8. Distribution of Summer (June – August) PM2.5 FRM Concentrations at Quincy, 2000-

2008.......................................................................................................................17

Figure 9. Distribution of Summer (June – August) PM2.5 FRM Concentrations at Redding, 2000-

2008.......................................................................................................................18

Figure 10. Quincy PM2.5 Concentrations: June – August, 2000-2008..........................................19

Figure 11. Redding PM2.5 Concentrations: June – August, 2000-2008.........................................19

Figure 12. Portola PM2.5 Concentrations: June – August, 2000-2008........................................20
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1.0 Introduction

On March 22, 2007, EPA adopted a final rule, Treatment of Data Influenced by Exceptional Events1

(EER) to govern the review and handling of certain air quality monitoring data for which the normal 

planning and regulatory processes are not appropriate. Under the rule, EPA may exclude data from use 

in determinations of National Ambient Air Quality Standard (NAAQS) exceedances and violations if a 

state demonstrates that an “exceptional event” caused the exceedances. Before EPA can exclude data 

from these regulatory determinations, the state must flag the data in EPA‟s Air Quality System (AQS)

database and, after notice and opportunity for public comment, submit a demonstration to justify the 

exclusion. After considering the weight of evidence provided in the demonstration, EPA decides 

whether or not to concur with each flag.

On August 28, 2009, California‟s Air Resources Board (CARB) submitted a preliminary 

demonstration for high-PM10 and PM2.5 events that occurred at various monitoring locations 

throughout California on twenty-seven separate days in the summer of 2008. Additional clarification 

was submitted to EPA via email on January 19, 2010 and January 26, 2010.

This document sets forth the legal and factual basis for EPA‟s decision regarding specific wildfirerelated events that allegedly caused exceedances of the 24-hour PM2.5 standard in the summer of 2008 

at: the Redding, Shasta County monitor on June 23 and July 23, 2008; the Portola, Plumas County 

monitor on June 23, June 26, July 11, and July 23, 2008; and the Quincy, Plumas County monitor on 

June 23 and July 19, 2008.

2.0 Summary of the Events

In the summer of 2008, California experienced a confluence of events resulting in one of California‟s 

worst summer fire seasons in history. In June 2008, California‟s governor declared a statewide 

drought, the first time a California statewide drought declaration had ever been made.2 Then, starting 

on June 20, 2008, a series of thunderstorms hit California. Lightning strikes ignited hundreds of fires 

throughout Northern and Central California. On June 28, 2008, the President of the United States 

declared a state of emergency for seven counties due to emergency conditions resulting from 

wildfires.3 On July 4, four more counties were added to the list.4 All told, the fires burned over one 

million acres.5 

Figure 1 is a map noting size, start date, and location of Summer 2008 California fires. It also shows

the eleven counties declared emergency areas due to wildfires. 

 

1

13560 Federal Register / Vol. 72, No. 55 / Thursday, March 22, 2007 / Rules and Regulations.

2

http://www.water.ca.gov/drought/docs/CalDrought.pdf. “Recent California Drought,” California Department 

of Water Resources. Retrieved February 5, 2010. 

3

http://www.fema.gov/news/newsrelease.fema?id=44432 “President Declares Emergency Disaster for 

California,” Federal Emergency Management Agency. Retrieved February 5, 2010. 

4

http://www.fema.gov/news/dfrn.fema?id=10853. “Federal Register Notice for California; Amendment No. 1 

to Notice of an Emergency Declaration,” Federal Emergency Management Agency. Retrieved February 5, 2010. 

5

http://www.bloomberg.com/apps/news?pid=newsarchive&sid=aNDa4mhKUxCU . “California Fires Ravage 

Record Acreage, Spare Economy (Update 1),” Bloomberg.com. Retrieved February 5, 2010. 
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Figure 1: Summer 2008 California Wildfires and Presidentially Declared Emergency Areas. 
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Smoke contains significant amounts of particulate matter and can adversely impact air quality. CARB 

operates air monitors throughout California, including Federal Reference Method (FRM) monitors at 

Portola and Quincy in Plumas County, and Redding in Shasta County. In the summer of 2008, 

monitors throughout Northern and Central California recorded exceedances of the 24-hour PM2.5

standard. This document addresses the exceedances listed in Table 1 that occurred at the Portola, 

Quincy, and Redding monitors. CARB flagged the events listed in Table 1 and requested the data be 

excluded as exceptional events due to effects of the Summer 2008 wildfires. This document addresses 

these specific days and monitors, and does not discuss the remaining PM2.5 or PM10 Summer 2008 

flags. This does not imply that EPA will either concur or not concur on the remaining events.

Table 1: Summer 2008 PM2.5 Flagged Events Under Review

Date Monitor PM2.5 (μg/m3

)

June 23, 2008 Redding Monitor (06-089-0004-01), Shasta County 97.1

“ “ Portola Monitor (06-063-1009-01), Plumas County 41.2

“ “ Quincy Monitor (06-063-1006-01), Plumas County 142.2

June 26, 2008 Portola Monitor (06-063-1009-01), Plumas County 113.5

July 11, 2008 Portola Monitor (06-063-1009-01), Plumas County 56.0

July 19, 2008 Quincy Monitor (06-063-1006-01), Plumas County 133.0

July 23, 2008 Redding Monitor (06-089-0004-01), Shasta County 200.2

“ “ Portola Monitor (06-063-1009-01), Plumas County 68.6

3.0 Requirements of the Exceptional Events Rule

Pursuant to 40 CFR §50.14(c)(3)(iii) a request for EPA‟s concurrence on an exceptional event flag 

must be accompanied by a demonstration that:

(A) The event satisfies all of the criteria set forth in 40 CFR §50.1(j). It:

affects air quality;

is not reasonably controllable or preventable; and

is caused by human activity that is unlikely to recur at a particular location, or is a natural 

event;

(B) There is a clear causal relationship between the measurement under consideration and the event 

that is claimed to have affected the air quality in the area;

(C) The event is associated with a measured concentration in excess of normal historical fluctuations, 

including background; and

(D) There would have been no exceedance or violation but for the event.

The EER also has procedural requirements. 40 CFR §50.14(c)(2)(iii) requires that data claimed to be 

due to an exceptional event be flagged in the AQS database, and that an initial description of the event
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be provided to EPA; both must occur by July 1 of the year following the event. In addition, 40 CFR 

§50.14(c)(3)(i) requires that the State:

submit a demonstration to EPA within three years of the calendar quarter of the event or 12 

months prior to an EPA regulatory decision;

provide notice and opportunity for public comment; and

submit any public comments along with the demonstration.

The following sections evaluate CARB‟s demonstration for the days and events in question with 

respect to these requirements.

4.0 Criteria Set Forth in 40 CFR § 50.1(j)

4.1 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.6 These criteria are discussed in detail in sections five and six below.

Smoke is made up of gas and particulate matter, and can adversely affect air quality. In the summer of 

2008, Northern California experienced an extreme fire season. From June 20 – July 22, 2008, a series 

of thunderstorms produced over 6,000 lightning strikes throughout Northern and Central California. 

These ignited numerous wildfires in over 26 counties that consumed over one million acres before 

containment on July 29.7 On June 28, seven counties were declared disaster areas, including Butte, 

Shasta, and Trinity Counties.

8

 By July 4, four more counties were declared disaster areas, including 

Plumas County.9 

Figure 2 shows the fires that started between June 20, 2008 and September 7, 2008 as well as CARB‟s 

Federal Reference Method (FRM), Federal Equivalent Method (FEM), and Beta Attenuation Method 

(BAM) PM2.5 air monitors. The specific fires are listed in Table 2. 

 

6

See 72 FR 13569, 72 FR 49051, and 73 FR 14702.

7 August Natural Events Documentation (NED), p. 5.

8

http://www.fema.gov/news/newsrelease.fema?id=44432 “President Declares Emergency Disaster for 

California,” Federal Emergency Management Agency. Retrieved February 5, 2010. 

9

http://www.fema.gov/news/dfrn.fema?id=10853. “Federal Register Notice for California; Amendment No. 1 

to Notice of an Emergency Declaration,” Federal Emergency Management Agency. Retrieved February 5, 2010.
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Figure 2: Major Federal Wildfires Burning in California June 20 – September 7, 2008, and 

PM2.5 (FRM, FEM, and BAM) Monitoring Sites in California. 
- 8 -

Table 2: Federal Wildland Fire Incidents in Northern California – June 20 to September 7, 2008.

Map 

Number

Incident 

Number Incident Name Latitude Longitude

Size 

(acres) Start Date

Controlled 

Date

1

CA-SRF1057 Blue 41.5664 -123.8217 225 6/20/2008

2

CA-SRF1224 Blue 2 41.5664 -123.8217 9,728 6/20/2008

3

CA-SRF1123 Hell's Half 40.7511 -123.5956 15,146 6/20/2008

4

CA-HUU003384 Humboldt Complex 40.3994 -123.9494 1,325 6/20/2008

5

CA-SHF1041 LIME COMPLEX 40.5342 -123.4508 99,585 6/20/2008

6

CA-SRF1120 Mad Complex 40.3047 -123.5364 3,705 6/20/2008

7

CA-MEU004608

MEU Lightning 

Complex 39.5139 -123.2083 54,819 6/20/2008 11/4/2008

8

CA-CZU005581 TRABING 36.9319 -121.8089 630 6/20/2008 6/24/2008

9

CA-SRF1126

Ukonom-South 

Complex 41.3547 -123.5364 58,871 6/20/2008

10

CA-SHF001079 ALPS COMPLEX 40.9194 -123.2381 1,218 6/21/2008

11

CA-TNF1011

American River 

Complex 39.1439 -120.6725 20,541 6/21/2008

12

CA-LPF1649 Basin Complex 36.2103 -121.7394 162,818 6/21/2008

13

CA-BEU002390 BROWN 36.7622 -121.1750 3,870 6/21/2008 6/24/2008

14

CA-BTU007660

BTU Lightning 

Complex 39.8797 -121.4000 64,995 6/21/2008 10/3/2008

15

CA-PNF000539 Canyon Complex 39.7039 -121.2483 47,680 6/21/2008 10/1/2008

16

CA-LNF2713 CUB Complex 40.1808 -121.5622 19,718 6/21/2008

17

CA-KNF002970 Gould 41.2003 -123.0464 229 6/21/2008 7/2/2008

18

CA-SHF1057

Iron & Alps 

Complexes 40.7325 -123.0539 105,805 6/21/2008

19

CA-MNF000579

June ABCD 

Complex 39.5025 -122.2025 3,000 6/21/2008

20

CA-KNF3393 Klamath Theater 41.6600 -123.1850 192,038 6/21/2008

21

CA-LNF002729

LNF June Lightning 

Complex 40.3750 -120.6250 200 6/21/2008 7/3/2008

22

CA-MMU008048 Mariposa Complex 37.3450 -120.2142 2,500 6/21/2008 6/24/2008

23

CA-STF1063 North Mountain 37.8833 -119.8792 2,889 6/21/2008

24

CA-MMU008107 OLIVER 37.4511 -119.7533 2,789 6/21/2008

25

CA-SNF0715 OLIVER COMPLEX 37.4511 -119.7533 1,000 6/21/2008

26

CA-LNF002745 Peterson 40.9114 -121.3789 1,200 6/21/2008

27

CA-LNF002782 Peterson Complex 40.9000 -121.3333 7,842 6/21/2008

28

CA-LMU2725 Popcorn 40.9347 -121.3342 3,000 6/21/2008

29

CA-SHU004727

SHU LIGHTNING 

COMPLEX 40.5708 -122.3558 86,500 6/21/2008
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Map 

Number

Incident 

Number Incident Name Latitude Longitude

Size 

(acres) Start Date

Controlled 

Date

30 CA-SNF-718 SILVER COMPLEX 36.4392 -119.6772 1,161 6/21/2008

31

CA-KNF002975

Siskiyou / Blue 2 

Complex 41.5894 -123.5800 82,186 6/21/2008

32 CA-MNF-645 SODA COMPLEX 39.3750 -122.9756 8,632 6/21/2008

33

CA-TGU4245

TGU LIGHTNING 

COMPLEX 40.1872 -122.2069 22,907 6/21/2008 7/6/2008

34

CA-WNP1095

Whiskeytown 

Complex 40.6000 -122.6333 6,420 6/21/2008

35

CA-LNU004790 WILD 38.3000 -122.2044 NR 6/21/2008 6/26/2008

36

CA-MNF000663 Yolla Bolly Complex 40.0703 -122.9653 NR 6/21/2008 9/15/2008

37

CA-TNF1015

Yuba River 

Complex 39.3664 -120.8206 4,254 6/21/2008

38

CA-LNF002776 Antelope 40.2519 -121.8664 600 6/22/2008

39

CA-SCU3094 HUMMINGBIRD 37.0353 -121.6553 794 6/22/2008

40

CA-LNF002777 Mill 40.1503 -121.8475 1,500 6/22/2008

41

CA-LNF002781 Mill Complex 40.1503 -121.8475 2,100 6/22/2008

42

CA-CZU005708 Quarry 37.6847 -122.4033 300 6/22/2008 6/29/2008

43

CA-LNU004843 WALKER 39.0714 -122.4947 NR 6/22/2008 7/3/2008

44

CA-SCU003091 WHITEHURST 37.0100 -121.6692 200 6/22/2008

45

CA-BDF6944 CAJON 34.2281 -117.4228 100 6/23/2008

46

CA-LMU2759 Corral 40.8681 -120.8825 12,434 6/23/2008

47

CA-KRN19301 BENA 35.2725 -118.6128 120 6/27/2008 6/27/2008

48

CA-SQF001356 PIUTE 35.4308 -118.4011 37,026 6/28/2008 8/31/2008

49

CA-KNF003204 No Mans 41.7219 -123.5325 200 6/30/2008 7/6/2008

50

CA-LPF1778 Gap 34.4869 -119.7828 9,443 7/1/2008

51

CA-LMU002934 Dixie 40.8853 -121.0844 350 7/2/2008 7/4/2008

52

CA-KNP0020 Tehipite 36.9047 -118.7986 11,596 7/19/2008 12/10/2008

53

CA-TCU006881 FRENCH 37.9767 -120.4808 102 7/22/2008 7/26/2008

54

CA-KNF003624 Panther 41.5919 -123.4308 72,344 7/22/2008

55

CA-MMU009779 Telegraph 37.5675 -119.9969 34,091 7/25/2008

56

CA-TCU7033 Serpentine 37.8089 -120.3014 162 7/26/2008 7/28/2008

57

CA-PNF000784 RICH 40.0114 -121.1836 6,112 7/29/2008 12/1/2008

58

CA-BTU9395 Craig 39.5667 -121.3669 2,001 8/3/2008 8/22/2008

59

CA-INF000656 SHERWIN 37.6106 -118.9403 347 8/3/2008

60 CA-LPF- Santa Lucia 34.9678 -120.1297 244 8/15/2008 9/2/2008
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Map 

Number

Incident 

Number Incident Name Latitude Longitude

Size 

(acres) Start Date

Controlled 

Date

002250 Lightning Complex

61

CA-BNP0437 Jack 41.8267 -121.5594 6,900 8/17/2008

62

CA-KNF004096 Slinkard 41.8164 -123.1653 374 8/17/2008

63

CA-FKU009403 Avenal 35.9639 -120.1078 946 8/19/2008 8/20/2008

64

CA-SHU006888 Lake 40.6031 -122.3819 110 8/26/2008 8/30/2008

65

CA-SHU6922 Olinda 40.4122 -122.3450 186 8/27/2008 8/30/2008

66

CA-SHF1949 ELMORE 40.8450 -122.3633 343 9/7/2008

67

CA-SHF1944 GULCH 40.3667 -122.9350 2,847 9/7/2008

The National Oceanic and Atmospheric Administration‟s (NOAA) descriptive text narrative for 

smoke/dust observed in satellite imagery describes dense smoke affecting northern California during 

this time period. Satellite images as well as numerous news reports and health advisories discussing 

smoke from the fires were submitted as part of CARB‟s package.10 

Given this evidence and the information presented in sections five and six below, we can reasonably 

conclude that the event in question had the potential to affect air quality. 

4.2 Not Reasonably Controllable or Preventable

Pursuant to 40 CFR § 50.14(c)(3), a state that is requesting exclusion of data affected by an 

exceptional event must submit a demonstration to EPA to justify the exclusion. One of the justification 

criteria is a showing that the event was “not reasonably controllable or preventable.” A determination 

of whether a particular event was reasonably controllable or preventable depends on the specific facts 

and circumstances surrounding the event. Therefore, EPA addresses this and other criteria of the 

exceptional events rule on a case by case basis.11. 

The Exceptional Events Rule defines a wildfire as an unplanned, unwanted wildland fire “such as fires 

caused by lightning...”12 The Summer 2008 California fires were caused by lightning13 and therefore 

qualify as a wildfires. 

We conclude that CARB has demonstrated that the events in question were unplanned wildfires ignited 

by uncontrollable natural events, and were not reasonably controllable or preventable. 

4.3 Natural Event

The Exceptional Events Rule states that “both wildfires and wildland fire use fires fall within the 

meaning of „natural events‟ as that term is used in CAA § 319. Therefore, ambient particulate matter 

 

10 August NED, Appendix C, Appendix F, and Appendix G.

11 72 FR 13560, 13564

12 72 FR 13560, 13566

13 August NED, Appendix G.
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and ozone concentrations due to smoke from a wildland fire will be considered for treatment as an 

exceptional event if the fire is determined to be either a wildfire or wildland fire use fire.”14

CARB asserts that the exceedances were a direct result of the lightning-ignited June and July wildfires. 

News reports submitted as part of CARB‟s package confirm that the fires were a result of lightning 

strikes.15 The events therefore qualify as natural events.

5.0 Clear Causal Relationship

Section 319 of the CAA and 40 CFR § 50.14(c)(3)(iii) require the State to demonstrate that there is a 

clear causal relationship between the measurement under consideration and the event that is claimed to 

have affected air quality in the area. 

As shown in Figure 2 and Table 2 above, a number of fires were ignited primarily along California‟s 

northern coast on June 20th. Over the following days and weeks, new fires started further inland. 

Figure 3 shows the location of the Redding, Quincy, and Portola PM2.5 monitors and the location of 

some of the fires that ignited between June 20 – July 23, 2008. 

Figure 3: Wildfires Ignited June 20 – July 23, 2008 near the Redding, Portola, and Quincy PM2.5

monitors. 

PM2.5 Monitor Icons:

1 = Redding monitor; 2 = Quincy monitor; 3 = Portola monitor

Fire Icons:

Dark Purple target – Fires started 6/20/2008; Light Purple target – Fires started 6/21/2008;

Pink target – Fires started 6/22/2008; Orange target – Fires started 6/23/2008;

Yellow target – Fires started 7/2/2008.

 

14 72 FR 135660, 13566

15 August NED, Appendix G.
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Wildfire smoke is a mixture of gas and particulate matter, and can adversely affect air quality. The 

PM2.5 FRM monitors at Portola and Quincy sampled every three days in the summer of 2008. The 

Redding monitor sampled once every six days. As shown in Figure 4, Portola, Quincy, and Redding 

began recording elevated PM2.5 concentrations on June 23 and measured lower concentrations by July 

26, 2008. This is consistent with the fires starting June 20, 2008 and containment by July 29, 2008.

Figure 4: PM2.5 concentrations recorded at Redding, Portola, and Quincy, June – August 2008.

The National Oceanic and Atmospheric Administration‟s (NOAA) descriptive text narrative for 

smoke/dust observed in satellite imagery describes dense smoke affecting northern California on June 

23, 2008. The June 26, 2008 narrative describes a large mass of smoke covering much of California 

extending north. Northern California is described as being covered by heavy, dense smoke on July 

11th, and moderate to dense smoke on July 19th. Finally, on July 23rd the northern third of California is 

described as covered with moderately dense to dense smoke from the wildfires.16 Satellite images 

taken by NOAA‟s Geostationary Operational Environmental Satellite (GOES) server also show what 

appear to be smoke plumes disseminating over Shasta and Plumas Counties. The June 23, 2008 

satellite image is included below. Additional satellite images as well as numerous news reports and 

health advisories discussing smoke from the fires were submitted as part of CARB‟s package.17 

 

16August NED, Appendix E.

17 August NED, Appendix C, Appendix F, and Appendix G.
- 13 -

Figure 5. NOAA Satellite Image, June 23, 2008.

Due to the area‟s hill and valley terrain, air masses impacting one valley may not impact another 

neighboring valley. According to CARB‟s submittal, the Plumas County, Portola monitor sits at an 

elevation of about 4,895 feet. It is located in a valley, surrounded by hilly terrain. The Plumas 

County, Quincy monitor is also in a small valley, and is sited at an elevation of approximately 3,422 

feet. The Shasta County, Redding monitor is located between the Cascades and the Trinity Alps, at 

approximately 560 feet.18 

CARB‟s January 26, 2010 supplemental information provided hourly wind vector and streamlines for 

Northern California on June 23, June 26, and July 11, 19, and 23. These show downslope winds 

moving air down through the valleys. 

Limited speciation data was available at Portola during the period under review; no speciation data was 

available from Redding or Quincy. Speciated levoglucosan data, used to indicate wood smoke, was 

available at Portola on a once-every-six-days schedule in 2007 and 2008. Some additional samples 

were also collected at the monitoring agency‟s discretion. Elevated concentrations were measured in 

June and July 2008, offering further support that smoke from forest fires was affecting this part of 

California. (See Table 3.)

 

18 January 26 Natural Events Documentation (NED), p. 5
- 14 -

Table 3. Levoglucosan Levels, Portola - Summer 2007 and 2008

Month Day 2007 24-hour Concentration (μg/m3) 2008 24-hour Concentration (μg/m3)

June 05 0.01 0.01

June 11 0.01 0.01

June 17 0.01 0.01

June 23 0.01 1.00

June 26 0.01 -

June 29 - 0.32

July 05 0.01 0.26

July 08 - 0.06

July 11 0.01 -

July 17 0.01 0.01

July 23 0.01 1.40

July 29 0.01 0.01

Aug 04 0.01 0.01

Aug 07 0.01 -

Aug 10 - 0.01

Aug 16 0.01 0.01

Aug 19 - 0.01

Aug 22 0.01 -

Aug 28 0.01 0.01

CARB supplied additional wood burning speciation information for Portola. Figure 6 shows wood 

burning markers levoglucosan, galactosan, and mannosan. The figure compares levels measured at 

Portola from June 23 through July 23, 2008 to the summer average levels.

Figure 6. Wood Burning Markers (Levoglucosan, Galactosan, Mannosan) at Portola during the 

Summer 2008 Wildfires, compared to Summer Average.
- 15 -

Speciation data indicates wood smoke affected the Portola monitor between June 23 and July 23. 

Satellite images and news reports indicate that smoke from numerous fires was impacting Shasta and 

Plumas Counties between June 23 and July 23, 2008.19 Monitored values at Portola, Quincy, and 

Redding indicate increased concentrations consistent with known fire activity. Taken together, the 

evidence indicates a clear causal relationship between the measurements under consideration and the 

wildfires.

6.0 Concentrations in Excess of Normal Historical Fluctuations

Pursuant to 40 CFR § 50.14(c)(3)(iii)(C), the demonstration must show that “the event is associated 

with a measured concentration in excess of normal historical fluctuations.” There is no “bright line” or 

specific threshold test for this requirement, but concentrations in the high percentiles can provide 

supporting evidence.20

PM2.5 levels in Plumas and Shasta County vary by season. Use of woodburning stoves results in 

higher wintertime concentrations, while summertime PM2.5 levels in Plumas and Shasta Counties 

typically fall between 0-10 μg/m3. (See Figures 7, 8 and 9.) 

For 2000-2008, these three monitors have a number of summertime fire exceptional events flags 

entered into the AQS database. From 2000 to 2008, the highest, non-flagged summer value monitored 

at Portola was 17.0 μg/m

3

. The June 23, June 26, July 11, and July 23, 2008 values are all more than 

twice this maximum concentration. If one considers both flagged and non-flagged data, these four 

days fall within or above the 98th percentile (see Table 4), and are four of the five highest summer 

values recorded at Portola from 2000-2008. As shown in Table 4 and Figure 7, values during the four 

Portola days in question far exceed the normal range of values observed during the summer months in 

Portola.

Table 4. Portola Monitor: Highest PM2.5 concentrations, Summers (Jun - Aug) 2000-2008.

Date

PM2.5 concentration 

(μg/m3) Data Percentile AQS flag

June 26, 2008 113.5 100% rt

July 23, 2008 68.6 100% rt

July 11, 2008 56 99% rt

Aug 22, 2000 43 99% e

June 23, 2008 41.2 98% rt

July 8, 2007 41 98% e

June 29, 2008 31.5 97% rt

June 17, 2000 17 97% none

rt = Wildfire-U.S.; e = Forest Fire

*Uses Parameter Occurrence Code (POC) 07 data for Jun-Aug 2007; uses POC01 data for all other years. No 

2002 data available for Portola.

 

19 August NED, Appendix C, Appendix E, Appendix G.

20 Exceptional Events Rulemaking (EER) Preamble, 72 FR 13569
- 16 -

Figure 7. Distribution of Summer (June - August) PM2.5 FRM Concentrations at Portola, 2000-2008.

*Uses POC07 data for Jun-Aug 2007; uses POC01 data for all other years. No 2002 data available.

The highest, non-flagged summer value monitored at Quincy from 2000 to 2008 was 16.0 μg/m

3

. At 

142.2 and 133 μg/m3, respectively, the June 23, 2008 and July 19, 2008 values are well above this 

maximum concentration. If one considers both flagged and non-flagged data, these two days fall 

within the 100th percentile (see Table 5). These days are the highest recorded at Quincy over the past 

nine summers. Values during the two Quincy days in question far exceed the normal range of values 

observed during the summer months in Quincy. (See Table 5 and Figure 8.)

Table 5. Quincy Monitor: Highest PM2.5 concentrations, Summers (Jun - Aug) 2000-2008.

Date PM2.5 concentration (μg/m3) Data Percentile AQS flag

June 23, 2008 142.2 100% rt

July 19, 2008 133 100% rt

July 11, 2008 85.5 99% rt

June 26, 2008 80.7 99% rt

July 8, 2008 54.3 98% rt

July 26, 2008 29.3 98% rt

June 28, 2006 26 98% e

July 8, 2007 25 97% e

Aug 21, 2002 18 97% e

Aug 1, 2002 17 96% e

June 14, 2008 16 96% none

rt = Wildfire-U.S; e = Forest Fire

95%

Other Flagged

Fire Events

Flagged 

Summer 2008 Events 

Under Review
- 17 -

Figure 8. Distribution of Summer (June – August) PM2.5 FRM Concentrations at Quincy, 2000-2008.

From 2000 to 2008, the highest, non-flagged summer value monitored at Redding was 38.0 μg/m

3

. 

The July 23, 2008 and June 23, 2008 values of 200.2 and 97.1 μg/m

3

far exceed this maximum 

concentration. If one considers both flagged and non-flagged data, these are the two highest days 

recorded at Redding over the past nine summers, and fall within the 99th and 100th percentile (see 

Table 6). As shown in Table 6 and Figure 9, values during the two days in question far exceed the 

normal range of values observed during the summer months in Redding.

Table 6. Redding Monitor: Highest PM2.5 concentrations, Summers (Jun - Aug) 2000-2008.

Date PM2.5 concentration (μg/m3) Data Percentile AQS flag

July 23, 2008 200.2 100% rt

June 23, 2008 97.1 99% rt

June 29, 2008 92.4 98% rt

July 17, 2008 54.8 98% rt

July 5, 2008 48.3 97% rt

Aug 18, 2002 38 96% none

rt = Wildfire-U.S.

Flagged 

Summer 2008 Events 

Under Review

Other Flagged

Fire Events

95%
- 18 -

Figure 9. Distribution of Summer (June – August) PM2.5 FRM Concentrations at Redding, 2000-2008.

These values are evidence that the summer 2008 concentrations under review at Portola, Quincy, and 

Redding are in excess of normal historical fluctuations and are clear outliers for their respective 

monitors.

7.0 No Exceedance But For the Event

Pursuant to 40 CFR §50.14(c)(3)(iii)(D), the demonstration must show that “there would have been no 

exceedance or violation but for the event.” The weight of evidence in a demonstration does not require 

a precise estimate of the estimated air quality impact from the event,

21 though that could be useful. 

Concentrations on days with similar emissions but without the influence of the event are rough 

evidence of what the concentration on the event day would have been but for the event. Comparison to 

otherwise similar days may provide one kind of evidence in the demonstration that the exceedance 

would not have occurred but for the event.

The following three figures show summer concentrations for Portola, Quincy, and Redding, measured 

from 2000-2008. Although Portola did not measure PM2.5 during the summer of 2002, all other years 

are represented for each monitor. 

Meteorological conditions during this nine year period would be expected to include multiple days 

with meteorology similar to conditions seen on the days under review. The two 2008 values under 

review at Quincy are well above values recorded at any other time during summers 2000-2008. (See 

Figure 10.) Except for other summer 2008 days also associated with the 2008 wildfires, the two 

 

21 EER Preamble 72 FR 23570

Flagged 

Summer 2008 Events 

Under Review

Other Flagged

Fire Events

95%
- 19 -

Redding values under review far exceed any summer concentrations measured 2000-2008. (See Figure 

11.) 2008 values at Portola are also well above recorded values, with the exception of one day in 2000 

and one day in 2007, both of which are flagged in AQS as fire events. (See Figure 12.)

Figure 10. Quincy PM2.5Concentrations: June – August, 2000-2008.

Figure 11. Redding PM2.5 Concentrations: June – August, 2000-2008.

July 23, 2008 Event 

Under Review

June 23, 2008 Event 

Under Review

July 19, 2008 

Event Under 

Review

June 23, 2008 

Event Under 

Review
- 20 -

Figure 12. Portola PM2.5Concentrations: June – August, 2000-2008.

The presence and extent of the wildfires, coupled with the speciation data, satellite images, news 

reports discussed in Section 5, and the uniqueness of the values over the past nine summers supports 

the conclusion that there would not have been exceedances on the days in question but for the 

wildfires. 

8.0 Procedural Requirements

The EER at 40 CFR §50.14(c) requires that data claimed to be due to an exceptional event must be 

flagged in the AQS database, that an initial description of the event be provided to EPA by July 1 of 

the year following the event, and the State must submit a demonstration to EPA within three years of 

the event. 

CARB flagged the events in AQS in accordance with 40 CFR §50.14. On August 28, 2009, CARB 

submitted their package for the Summer 2008 PM2.5 events. CARB sent additional clarification to 

EPA via email on January 19, 2010, and January 26, 2010.

40 CFR §50.14(c)(3)(i) also requires notice and opportunity for public comment. 40 CFR 

§50.14(c)(3)(i) requires that any public comments be submitted along with the demonstrations. CARB 

public noticed the Summer 2008 PM2.5 Events package beginning July 20,2009. The package was 

June 23, 2008 & 

June 26, 2008 

Events Under 

Review

July 11, 2008 & 

July 23, 2008 Events 

Under Review
- 21 -

posted on the CARB website, and air districts and public listserv recipients were notified. No public 

comments were received.22 

Numerous health and smoke advisories issued in response to the summer 2008 fires are included as 

Appendix F in CARB‟s August 28, 2009 submittal. 

9.0 Conclusion

Documentation submitted by CARB claims that smoke from the summer 2008 wildfires caused 

exceedances of the 24-hour PM2.5 NAAQS at numerous monitoring stations. This package reviews 

exceedances at the Portola monitor on June 23, June 26, July 11, and July 23, 2008, exceedances at the 

Quincy monitor on June 23 and July 19, 2008, and exceedances at the Redding monitor on June 23 and 

July 23, 2008. All values under review fall above their respective site‟s 95th percentile observed during 

summer months (June – August), 2000-2008. The values far exceed the expected range of 

concentrations for unflagged days and fall into or above the 98th percentile when considering all data 

(flagged and unflagged). Speciation data collected at Portola shows evidence of forest fire 

contributions, and news reports, satellite imagery, and wind field modeling indicate smoke from the 

wildfires was affecting air quality in Plumas and Shasta Counties. The information and analyses 

presented in this package and in CARB‟s submittal documents do not represent the entire suite of 

possible evidence for exceptional event packages. For other types of events and other pollutants, 

additional or alternate evidence may be necessary to make an exceptional events determination. In this 

particular instance, however, given that the events are wildfires affecting 24-hour PM2.5 concentrations, 

the weight of evidence is sufficient to satisfy the EER criteria. EPA concurrence is given to the 

aforementioned Summer 2008 PM2.5 exceptional event flags for the Portola, Quincy, and Redding 

monitors.

10.0 Citation of Exceptional Event Request Documentation

August NED August 28, 2009 Natural Event Documentation

“PM2.5 and PM10 Natural Event Document: Summer 2008 Northern California Wildfires, 

June/July/August 2008,” California Air Resources Board, August 28, 2009, with attachments.

Letter from Karen Magliano, Air Resources Board, to Matthew Lakin, U.S. Environmental Protection 

Agency Region 9, August 28, 2009 requesting exclusion of Summer 2008 exceedances, with 

enclosures: August NED.

January 19 NED January 19, 2010 Natural Event Documentation

“2008 Northern California Wildfires,” California Air Resources Board, January 19, 2010.

January 26 NED January 26, 2010 Natural Event Documentation

“Wind Fields in Northern California During the 2008 Wild Fires,” California Air Resources 

Board, January 26, 2010.

 

22 January 19 NED, p. 1.