- 1 -

Review of Evidence Regarding 

Claimed Exceptional Events 

Leading to 24-hour PM2.5

Exceedances 

Plumas County, CA

July 8, 2007

US Environmental Protection Agency

Region 9

March 11, 2010
- 2 -

Contents

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

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

3.0 Requirements of the Exceptional Events Rule......................................................................3

4.0 Criteria Set Forth in 40 CFR §50.1(j)...................................................................................4

4.1 Affects Air Quality............................................................................................................4

4.2 Not Reasonably Controllable or Preventable...................................................7

4.3 Natural Event.....................................................................................................................7

5.0 Clear Causal Relationship.....................................................................................................7

6.0 Concentrations in Excess of Normal Historical Fluctuations.............................................11

7.0 No Exceedance But For the Event......................................................................................12

8.0 Procedural Requirements....................................................................................................14

9.0 Conclusion ..........................................................................................................................15

10.0 Citation of Exceptional Event Request Documentation .....................................................15

Tables

Table 1. Portola 2007 PM2.5 Flagged Event Under Review.............................................3

Table 2. PM2.5 FRM Monitored Values: July 5-11, 2007 (μg/ m

3

)....................................9

Table 3. Portola Monitor: Highest PM2.5Concentrations, Summers (Jun-Aug) 2000-2008......11

Table 4. Portola BAM and FRM Concentrations, July 1 – July 15, 2007...........................13

Figures

Figure 1. Federal Reference Method PM2.5 monitors near the Antelope Complex Fire..............5

Figure 2. PM2.5 Federal Reference Method monitors in and around Plumas County, CA: June –

August, 2007....................................................................................................6

Figure 3. NOAA GOES Satellite Image – July 8, 2007 (7:30am PDT)...............................7

Figure 4. Forward HYSPLIT Trajectory – July 8, 2007 (every hour)..................................9

Figure 5. FRM and BAM PM2.5 concentrations recorded at Northern Sierra monitors, July 

2007.............................................................................................................10

Figure 6. Distribution of Summer (Jun - Aug) PM2.5 FRM Concentrations at Portola, 2000-

2008.............................................................................................................12

Figure 7. Summertime PM2.5 Values at Portola: 2000-2007...........................................14
- 3 -

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 June 17, 2009, California‟s Air Resources Board (CARB) submitted a preliminary demonstration 

for a high-PM2.5 event that occurred at the Plumas County Portola monitor on July 8, 2007. Additional 

clarification was submitted to EPA via email on December 22, 2009.

This document sets forth the legal and factual basis for EPA‟s decision regarding the specific wildfirerelated event that allegedly caused an exceedance of the 24-hour PM2.5 standard at the Plumas County 

Portola monitor on July 8, 2007.

2.0 Summary of the Event

On July 5, 2007, a series of dry thunderstorms moved through Plumas National Forest in Northern 

California. Lightning strikes ignited over a dozen fires, collectively referred to as the Antelope 

Complex Fire (also called the Antelope/Wheeler Fire). The Antelope Complex Fire was contained on 

July 11, 2007 after burning more than 23,000 acres2. 

The Northern Sierra Air District and CARB operate air monitors in and around Plumas County. On 

July 8, 2007, the PM2.5 monitor at Portola recorded an exceedance of the 24-hour PM2.5 standard (see 

Table 1). CARB flagged the July 8, 2007 exceedance and requested the event be excluded as an 

exceptional event due to impacts from the nearby Antelope Complex Fire. 

Table 1: Portola 2007 PM2.5 Flagged Event Under Review

Date Monitor PM2.5 (μg/m3

)

July 8, 2007 Portola Monitor (06-063-1009-07), Plumas County 41.0

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:

 

1

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

2

http://gis.fs.fed.us/r5/hfqlg/monitoring/resource_reports/fire_and_smoke/antelopecomplex_Final_20071204.pdf

. “Fire Behavior and Effects Relating to Suppression, Fuel Treatments, and Protected Areas on the Antelope 

Complex Wheeler Fire,” U.S Forest Service Pacific Southwest Region, p. 5. Retrieved February 6, 2010.
- 4 -

(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

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 day 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.3 These criteria are discussed in detail in sections five and six below.

According to a July 6, 2007 U.S. Forest Service news release, the Antelope Complex Fire was ignited 

by a series of lightning strikes on July 5, 2007. The lightning strikes started over a dozen fires 

(collectively referred to as the Antelope Complex Fire) in the Plumas National Forest, the largest of 

which was the Wheeler Fire, near Wheeler Peak.4 The Antelope Complex Fire was contained on July 

11 after burning more than 23,000 acres.5

 

3

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

4

June Natural Events Documentation (NED), Attachment 3.

5

http://gis.fs.fed.us/r5/hfqlg/monitoring/resource_reports/fire_and_smoke/antelopecomplex_Final_20071204.pdf

. “Fire Behavior and Effects Relating to Suppression, Fuel Treatments, and Protected Areas on the Antelope 

Complex Wheeler Fire,” U.S Forest Service Pacific Southwest Region, p. 5. Retrieved February 6, 2010.
- 5 -

Figure 1 shows the Federal Reference Method (FRM) PM2.5 monitors surrounding the Antelope 

Complex Fire. Portola and Quincy operate in Plumas County, just southwest and south of the fire. 

Shasta and Lassen counties lie to the north of Plumas County. In 2007, the Redding monitor was the 

only Federal Reference Method or Federal Equivalent Method (FEM) PM2.5 monitor operating in 

Shasta and Lassen Counties. The Chico, Butte County monitor lies to the west of Plumas County, 

while Grass Valley and Truckee are to the south in Nevada County.

Figure 1: Federal Reference Method PM2.5 monitors near the Antelope Complex Fire.
- 6 -

As shown in Figure 2, all three monitors that measured concentrations on July 8, 2007 (Portola 

Parameter Occurrence Code (POC) 07, Quincy POC01, and Truckee POC01) showed elevated PM2.5

concentrations. The remaining monitors showed slightly increased concentrations on July 5 - the day 

the fire started, and July 11 - the day the fire was contained.

Figure 2: PM2.5 Federal Reference Method monitors in and around Plumas County, CA: June –

August, 2007.

Wildfire smoke is a mixture of gas and particulate matter and can adversely affect air quality. Satellite 

images, narrative, and new stories, were submitted as part of CARB‟s June 2009 package.6 

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 

 

6

June NED, Attachment 4 and Attachment 5.
- 7 -

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

exceptional events rule on a case by case basis.7. 

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

caused by lightning...”8 The Antelope Complex Fire was caused by lightning and therefore qualifies 

as a wildfire. CARB‟s submittal notes that there was no prescribed burning in the area and that July 8 

was declared a “no-burn” day by the California Department of Forestry and Fire Protection.9 

We conclude that CARB has demonstrated that the event in question was an unplanned wildfire ignited 

by an uncontrollable natural event, and was 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 

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.”10

CARB asserts that the July 8, 2007 exceedance is a direct result of the lightning-ignited Antelope 

Complex Fire. A U.S. Department of Agriculture – Forest Service news release and other news reports 

submitted as part of CARB‟s package confirm that the Antelope Complex Fire was a result of lightning 

strikes.

11

 The event therefore qualifies as a natural event.

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 1, CARB and the Northern Sierra Air Quality District run a number of PM2.5 FRM 

monitors in counties surrounding the Antelope Complex Fire. The two closest to the fire are the 

Portola monitor and the Quincy monitor. According to CARB‟s submittal, the Portola monitor is in a 

valley about 23 miles southeast from the center of the fire, sited at an elevation of about 4,895 feet. 

The Quincy monitor is approximately 24 miles southwest of the center of the fire, at an elevation of 

about 3,422 feet, and is located in a separate valley. The fire was located at an elevation of about 

5,000 feet.12 Due to the area‟s hill and valley terrain, air masses impacting one valley may not impact 

another neighboring valley.

The various monitors sample at different frequencies. The Quincy POC01 and Truckee POC01 FRM 

monitors sample once every three days, and collected data on July 8, 2007 while the fire burned. In 

Portola, there were two monitors running in July 2007. Each sampled every 6th day, but on a staggered 

 

7

72 FR 13560, 13564

8

72 FR 13560, 13566

9

June NED, p. 10.

10 72 FR 135660, 13566

11 June NED, Attachment 3.

12 December Natural Events Documentation (NED), p. 1.
- 8 -

schedule. While the POC01 Portola monitor measured on July 5, 11, and 17, the POC07 Portola 

monitor measured on July 2, 8, and 14. Portola therefore also had a monitor that sampled on July 8. 

As shown in Table 2, both Portola POC07 and Quincy POC01 monitored elevated concentrations on 

July 8, 2007, and significantly lower values on July 5 and July 11. Other monitors located further 

away from the fire showed slightly elevated concentrations at the time of the fire.

Table 2. PM2.5 FRM Monitored Values: July 5-11, 2007. (μg/ m

3

)

Portola 

(AQS: 06-063-

1009-07)

Portola 

(AQS: 06-063-

1009-01)

Quincy (AQS: 

06-063-1006-

01)

Truckee 

(AQS: 06-057-

1001-01)

Grass Valley 

(AQS: 06-057-

0005-01)

Chico (AQS: 

06-007-0002-

01)

Redding 

(AQS: 06-089-

0004-01)

7/2/2007 3 - 4 3 - - -

7/5/2007 - 6 8 6 8 12 7

7/8/2007 41 - 25 15 - - -

7/11/2007 - 11 12 13 6 6 6

7/14/2007 4 - 5 7 - - -

Wildfire smoke is a mixture of gas and particulate matter and can adversely affect air quality. A huge 

plume of smoke was reported both in local news stories and in the National Oceanic and Atmospheric 

Administration‟s (NOAA) descriptive text narrative for smoke/dust observed in satellite imagery. 

Satellite images taken by NOAA‟s Geostationary Operational Environmental Satellite (GOES) server 

also show what appear to be smoke plumes originating at the first and disseminating over surrounding 

areas. Figure 3 shows a satellite image for 7:30am on July 8, 2007. This image, as well as additional 

satellite images, narrative, and new stories, were submitted as part of CARB‟s June 2009 package.13 

Figure 3. NOAA GOES Satellite Image – July 8, 2007 (7:30am PDT)

 

13June NED, Attachment 4 and Attachment 5.
- 9 -

CARB also conducted modeling to demonstrate whether smoke from the Antelope Complex Fire may 

have affected the Portola monitor on July 8, 2007. On December 22, 2009, CARB supplied revised 

forward trajectories that modeled the movement of air parcels from the estimated location of the 

Antelope Complex Fire using the NOAA Hybrid Single-Particle Lagrangian Integrated Trajectory

(HYSPLIT) model. CARB used United States Forestry Service coordinates to orient the fire in the 

model.

Figure 4 is a forward trajectory from the Antelope Complex Fire‟s modeled location, representing July 

8, 2007 from the hours of midnight to midnight. According to the HYSPLIT trajectory, the Portola site 

was directly affected by the fire on July 8, 2007. The trajectory also indicates that Quincy may have 

experienced some smoke affects, and Grass Valley appears to have been minimally affected. This 

modeling result compares well against actual monitored concentrations. Of the monitors in the area, 

Portola recorded the highest concentration on July 8, with Quincy recording roughly half the Portola 

value (Table 2). Grass Valley did not monitor on July 8, but shows lower concentrations on July 11 

than Portola and Quincy. Additional trajectories are included in CARB‟s December 22, 2009 

supplemental information.14

Figure 4. Forward HYSPLIT Trajectory - July 8, 2007 (every hour)

Figure 5 shows PM2.5 concentrations collected at Portola, Quincy, and Grass Valley monitoring 

stations in July 2007. In addition to PM2.5 FRM filter-based monitors it shows 24-hour averages from 

the PM2.5 Beta Attenuation Method (BAM) continuous analyzers. This type of analyzer was not 

approved for FEM status until 200815 and therefore does not meet 40 CFR §58 requirements for 

 

14 December NED, p. 2-7.

15 73 FR 13224
- 10 -

NAAQS comparison in this instance. The BAMs therefore provide additional information on the days 

the FRMs did not monitor, but are not directly compared against the NAAQS. All FRM and BAM

monitors show increased concentrations between July 5 and July 11, with July 8 showing the highest 

concentrations. On July 8, the Portola BAM is lower than the Quincy BAM. This is likely due to a 

malfunction of the Portola BAM which caused it to lose several hours of data.16 

Figure 5: FRM and BAM PM2.5 concentrations recorded at Northern Sierra monitors, July 2007.

The Portola site did not collect carbon speciation data during this time period. Levoglucosan speciation 

data, used to indicate wood smoke, was collected at Portola on a once-every-six-days schedule. Data 

from July 5 and July 11, 2007 show negligible levoglucosan levels (0.01 μg/ m

3

for both days), 

indicating little or no impact from wood smoke on those two days at Portola. As levoglucosan was not 

sampled on July 7, no conclusion is possible for the event day in question based on levoglucosan data. 

While the speciation data are inconclusive, the trajectory modeling and satellite images indicate that 

the Portola monitor was affected by smoke from the Antelope Complex Fire on July 8, 2007, and 

monitored values also increase following the July 5, 2007 lightning strikes. CARB‟s submission also 

includes local news articles that further document the wildfire and its impact on air quality.17 The 

evidence suggests a clear causal relationship between the July 8, 2007 exceedance and the Antelope 

Complex Fire.

 

16 December NED, p. 8.

17 June NED, Attachment 4 and Attachment 5.
- 11 -

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.18

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

wintertime concentrations, while summertime PM2.5 levels in Plumas County typically fall between 

0-10 μg/m3(see Figure 6). 

For Portola, CARB has flagged a number of summer days in the AQS for exceptional events review. 

All flagged days are associated with summer fires. From 2000 to 2008, the highest, non-flagged 

summer value monitored at Portola was 17.0 μg/m

3

. July 8, 2007‟s value of 41.0 μg/m

3

is more than 

double this maximum concentration. If one considers both flagged and non-flagged data, the July 8, 

2007 value of 41.0 μg/m

3

falls within the 98th percentile (see Table 3). As shown in Table 3 and Figure 

6, the July 8, 2007 value far exceeds the normal range of values observed during the summer months in 

Portola.

Table 3. Portola Monitor: Highest PM2.5 concentrations, Summers (Jun -

Aug) 2000-2008.

Date

PM2.5 concentration 

(μg/ m

3

)

Data 

Percentile AQS flag

June 26, 2008 113.5 100% rt

July 23, 2008 68.6 100% rt

July 11, 2008 56.0 99% rt

Aug 22, 2000 43.0 99% e

June 23, 2008 41.2 98% rt

July 8, 2007 41.0 98% e

June 29, 2008 31.5 97% rt

June 17, 2000 17.0 97% none

rt = Wildfire-U.S.

e = Forest Fire

*Uses POC7 data for Jun-Aug 2007; uses POC1 data for all other years. No 2002 

data available for Portola.

 

18 Exceptional Events Rulemaking (EER) Preamble, 72 FR 13569
- 12 -

Figure 6. Distribution of Summer (Jun - Aug) 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.

These values are evidence that the concentration measured on July 8, 2007 is in excess of normal 

historical fluctuations and is a clear outlier value at the Portola monitor. 

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,

19 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.

Table 4 shows concentrations just before and after the claimed exceptional event day. The FRM 

monitor collects a sample once every three days and is relevant for comparison against the NAAQS. 

Although the continuous BAM monitor was not an approved FEM at the time of monitoring and is 

 

19 EER Preamble 72 FR 23570

95%

Flagged – Other 

Fire Events

Flagged –

July 8, 2007 Antelope 

Complex Fire
- 13 -

therefore not relevant for comparison against the NAAQS in this instance, the Portola BAM data are 

provided for informational purposes. Three days before the event, the FRM monitor measured 6.0 

μg/m

3

, then rose to 41.0 μg/m

3

on July 8, and three days later decreased to 11.0 μg/m

3

. The 

continuous Portola BAM monitor measured 10.0 μg/m

3

the day before the flagged event, increased to 

24.7 μg/m

3

on July 8, remained elevated on July 9, and decreased down to 7.7 μg/m

3

by July 10. The 

BAM data shows elevated concentrations from the day the fire started (July 5, 2007) until a few days 

after the fire was contained on July 11, 2007. Higher concentrations may be seen following 

containment due to lingering smoke in the atmosphere, smoke from embers, or smoke from contained 

but not fully extinguished portions of the fire. 

Table 4. Portola BAM and FRM Concentrations, July 1 – July 15, 2007

Date

Portola BAM 

Concentration (μg/m3)

Portola FRM Concentration 

(μg/m3)

7/1/2007 0 -

7/2/2007 0.3 3.0

7/3/2007 1 -

7/4/2007 1.5 -

7/5/2007 1.5 6.0

7/6/2007 6.1 -

7/7/2007 10 -

7/8/2007 24.7 41.0

7/9/2007 22.2 -

7/10/2007 7.7 -

7/11/2007 10.2 11.0

7/12/2007 6.8 -

7/13/2007 3.6 -

7/14/2007 2 4.0

7/15/2007 1.5 -

The FRM and BAM data show a clear spike in concentrations concurrent with the Antelope Complex 

Fire, indicating that but for the fires, the Portola FRM would not have exceeded the standard on July 8, 

2007.

Data from 2000-2007 also indicate that but for the fires, PM2.5 levels would not have reached 41.0 

μg/m

3

. Figure 7 shows summer concentrations for Portola, measured 2000-2001, and 2003-2007. 

Portola did not measure PM2.5 during the summer of 2002. Data from the primary Portola monitor as 

well as a temporary Portola monitor that operated from 2007 through early 2008 is included for 2007. 

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

with meteorology similar to that of July 8, 2007. Out of 213 monitored summer days, only one value 

matches July 8, 2007 in magnitude. This value, recorded in August 2000, is flagged in AQS as a forest 

fire event. Other than this single other value, the July 8, 2007 event at Portola is well above recorded 

concentrations for summers 2000-2007.
- 14 -

Figure 7. Summertime PM2.5 Values at Portola: 2000-2007.

Since no PM2.5 speciation data was collected in the Portola area on the day in question, an organic mass 

apportionment was not possible. The magnitude of the observed concentration compared to days just 

before and just after, the value‟s uniqueness over seven years of data, together with wind trajectories 

that strongly support the transport of smoke into the Portola area, present sufficient evidence to 

conclude that there would have been no exceedance of the 24-hour standard but for the event. 

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 that the State must submit a demonstration to EPA within three years 

of the event. 

The event was flagged in AQS as required by 40 CFR §50.14. On June 17, 2009, CARB submitted 

their demonstration to EPA for the July 8, 2007 event. CARB sent additional clarification on 

December 22, 2009.

Flagged –

July 8, 2007 Antelope 

Complex Fire
- 15 -

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. The 

Northern Sierra Air Quality Management District (NSAQMD) public noticed the July 8, 2007 package 

from May 5, 2009 through June 5, 2009 on the NSAQMD website. No public comments were 

received.20 

Smoke and Health Information issued by the Plumas National Forest in response to the July 8, 2007 

fires was included in the July 8, 2007 package.21 

9.0 Conclusion

Documentation submitted by CARB claims that smoke from the Antelope Complex Fire caused an 

exceedance of the 24-hour PM2.5 NAAQS at the Portola site on July 8, 2007. Forward HYSPLIT 

trajectories as well as satellite photographs strongly support the possibility of smoke impacts in the 

Portola area on July 8, 2007. The value measured on July 8, 2007 is above the site‟s 95th percentile 

observed during summer months (June – August), 2000-2008. The value far exceeds the expected 

range of concentrations for unflagged days and falls into the 98th percentile when considering all data 

(flagged and unflagged). Since no PM2.5 speciation data was collected in the Portola area on the day in 

question, an organic mass apportionment was not possible. 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 event determination. In this particular instance, 

however, given that the event is a wildfire affecting a 24-hour PM2.5 concentration, the cause of the 

event (lightning), the magnitude of the observed concentration compared to days just before and after, 

historical levels at the site, wind trajectories that support the transport of smoke into the Portola area,

and satellite images and news articles combine to provide sufficient evidence to satisfy the EER 

criteria. Provided this weight of evidence, EPA concurrence is given to the exceptional event flag on 

the Portola monitor‟s July 8, 2007 PM2.5 concentration.

10.0 Citation of Exceptional Event Request Documentation

June NED June 17, 2009 Natural Event Documentation

“Natural Event Document: Antelope Fire, July 2007,” 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, June 17, 2009 requesting exclusion of July 8, 2007 exceedance, with 

enclosures: June NED; Letter from Gretchen Bennitt, Northern Sierra Air Quality 

Management District, to Karen Magliano, California Air Resources Board, June 9, 2009, 

requesting exclusion of the July 8, 2007 exceedance; photocopy of public notice, “Natural 

Event Document for July 8, 2007 Portola Smoke Incursion from Antelope/Wheeler Complex 

Fire, Plumas County.”

December NED December 22, 2009 Natural Event Documentation

“July 8, 2007 Portola Exceptional Event,” California Air Resources Board, December 22, 2009.

 

20 Letter from Karen Magliano, attachment. 

21 June NED, Attachment 1.