1

Review of Exceptional 

Event Request 

Folsom, CA

1-Hour Ozone

June 23, 2008

June 27, 2008

July 10, 2008

U.S. Environmental Protection Agency

Region 9

April 13, 2011
2

Contents

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

2.0 Summary of the Events..........................................................................................................4

3.0 Requirements of the Exceptional Events Rule.......................................................................4

4.0 Criteria Set Forth in 40 CFR §50.1(j)....................................................................................5

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

6.0 Concentration in Excess of Normal Historical Fluctuations..................................................9

7.0 No Exceedances But For the Event .......................................................................................9

8.0 Procedural Requirements.....................................................................................................11

9.0 Conclusion ...........................................................................................................................11
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1.0 Introduction

On March 22, 2007, EPA adopted the rule Treatment of Data Influenced by Exceptional Events,

1

also known as the Exceptional Events Rule (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 terms of the EER, a state may request EPA to exclude data showing 

exceedances or violations of the National Ambient Air Quality Standard (NAAQS) that are 

directly due to an exceptional event from use in regulatory determinations. It may do so by 

demonstrating to EPA’s satisfaction that such event caused a specific air pollution concentration 

at a particular air quality monitoring location.2 Before EPA will exclude data from these 

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

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

justify the exclusion. After considering the weight of the evidence provided, EPA will then 

evaluate the demonstration in accordance with the requirements of the EER for the purposes of 

either concurring or nonconcurring with the State’s requested flag.

On September 17, 2009, the California Air Resources Board (CARB) submitted to EPA a 

preliminary demonstration for twenty-three 1-hour ozone exceedances on six days and at five 

monitoring sites in the Sacramento Regional Ozone Nonattainment Area. EPA reviewed this 

demonstration and sent a letter to CARB on July 29, 2010, requesting more information. On

March 30, 2011 CARB submitted final demonstrations for eight 1-hour exceedances on three

days at the Folsom monitoring site, a subset of the originally requested exceedances.

This document sets forth the legal and factual basis for EPA’s decisions regarding exceedances 

of the 1-hour Ozone NAAQS in 2008 at the Folsom monitoring site on June 23, June 27, and 

July 10, 2008 that CARB has flagged as due to “wildfire” exceptional events. EPA has not yet 

completed its analysis of the remaining dates and is not making a concurrence or nonconcurrence determination for them at this time. 

The documentation submitted by CARB in support of the exceptional events claims includes the 

following: 

Exceptional Events Demonstration for High Ozone in the Sacramento Regional 

Nonattainment Area Due to Wildfires; Sacramento Metropolitan Air Quality 

Management District and California Air Resources Board – July 8, 2009; Submitted to 

EPA on September 17, 2009 (“September 2009 Submittal”); and

Exceptional Events Demonstration for 1-Hour Ozone Exceedances in the Sacramento 

Regional Nonattainment Area Due to 2008 Wildfires– Updated Documentation; March 

30, 2011 (“March 2011 Submittal”).

Although EPA reviewed both of these documents in developing our decisions, we believe that 

the document submitted on March 30, 2011 is a stand-alone exceptional events demonstration 

that provides revised documentation and support for all rule criteria independently of the 

 

1

72 FR 13560 (March 22, 2007).

2

40 CFR §50.14 (a).
4

September 2009 submittal. Therefore, this document primarily cites evidence from the March 

2011 demonstration.

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. The Governor’s Office of Emergency Services 

reported the 2008 June Fire Siege as the largest single fire event in California’s recorded history 

(since 1936). CARB’s description of the 2008 Lightning Wildfire Complex events in section 2C 

of the March 2011 Submittal explains how lightning strikes from a series of thunderstorms hit 

California from June 20 to June 22, 2008, igniting numerous wildfires. A combination of dry 

conditions over 2007-2008 and other weather conditions such as record-breaking heat waves, 

low humidity and a foehn (dry, downslope) wind event, exacerbated the fires and hampered 

firefighting efforts.

The information CARB submitted about these wildfires is corroborated in a report prepared by 

an interagency team of investigators at the request of California Department of Forestry and Fire 

Protection (CAL Fire), the U.S. Forest Service, Office of Emergency Services, and the National Park 

Service.3The following is an excerpt from that report, “The 2008 Fire Siege”:

On June 20th and 21st a series of severe, dry thunderstorms carpeted the state from Big Sur 

to Yreka with more than 5,000 lightning strikes, and igniting over 2,000 fires. During the 

following months, thirteen firefighters were killed and many others were injured on fires in 

this siege. Over 350 structures were destroyed and hundreds of millions of dollars of 

property and natural resources were damaged. Thousands of people were evacuated and 

smoke adversely effected air quality over much of the state for weeks. Communications, 

power delivery, and transportation systems were disrupted. Despite the intensive firefighting 

effort, some fires in remote areas continued to burn throughout the summer. By fall, over 

1,200,000 acres had burned.

The June 2008 Fire Siege report also describes the increases in firefighting resources and public 

awareness efforts that resulted from an Executive Order signed by Governor Schwarzenegger on 

May 9, 2008 in anticipation of a severe fire season.

3.0 Requirements of the Exceptional Events Rule

Pursuant to 40 CFR §50.14(c)(3)(iv) a State’s request that EPA exclude data showing 

exceedances or violations of the NAAQS must be accompanied by a demonstration to justify 

data exclusion that provides evidence that:

(A) The event satisfies the criteria set forth in 40 CFR §50.1(j) that it:

affects air quality; 

is not reasonably controllable or preventable; 

 

3 California Department of Forestry and Fire Protection, “2008 Fire Siege” (retrieved April 1, 2011) available at 

http://www.fire.ca.gov/fire_protection/downloads/siege/2008/2008FireSiege_full-book_r6.pdf (Multiagency Fire 

Investigation Report).
5

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 demonstrations must fully meet all the above criteria to EPA’s satisfaction; failure to meet 

any one of the criteria will result in EPA’s non-concurrence with the flagging of the exceedance 

in question. In addition to technical criteria, the EER also contains procedural requirements. 40 

CFR §50.14(c)(2)(iii) requires that data claimed to be due to an exceptional event must 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.

EPA's will then concur or non-concur with a State's flag indicating that an exceedance resulted 

from an exceptional event. However, such concurrence or nonconcurrence does not constitute 

final agency action. The data that are the subject of the concurrence or nonconcurrence may

become the basis for a subsequent EPA determination regarding an area’s attainment status. 

Only when EPA makes a final determination, after notice-and-comment rulemaking, to exclude 

from consideration the data that were flagged by the State as due to an exceptional event, does 

the concurrence or nonconcurrence become part of a final agency action that is judicially 

reviewable under CAA section 307(b)(1).

The following sections evaluate CARB’s submission regarding the events of June 23, June 27, 

and July 10, 2008, with respect to the requirements of the Exceptional Events Rule.

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

The criteria in 40 CFR §50.1(j) state that the exceptional event must affect air quality, be not 

reasonably controllable or preventable, and be caused by human activity that is unlikely to recur 

at a particular location or a natural event. 

EPA generally considers the emissions of ozone precursors from lightning-induced wildfires as

meeting the regulatory definition of a natural event, defined as one “in which human activity 

plays little or no direct causal role” (40 CFR 50.1(k)).
6

As stated in the preamble to the EER, the event in question shall be 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.4 EPA’s review of these criteria is discussed in sections 

5 and 6 below. 

A determination of whether a particular event was “not reasonably controllable or preventable”

depends on the specific facts and circumstances surrounding the event. Therefore, EPA

addresses this and the other criteria of the EER on a case-by-case basis. With respect to whether 

these wildfire events and their effects on ozone concentrations were not reasonably controllable 

or preventable, EPA notes a number of considerations, all of which support concurrence on the 

state's exceptional events flags for the three days in question. First, the initiation of the 

numerous fires by lightning strikes under dry conditions means that the occurrence of the fires 

was not reasonably preventable. Second, it would not have been reasonable for the state to have 

required or to have itself accomplished prior removal of all or part of the fuel loadings that 

contributed to the fire emissions, given the scattered and unpredictable locations of the fires over 

a huge land area, given that at least some of the lands are intended to be left undisturbed, and 

given that federal land management agencies already had adopted forest plans for many of the 

areas in question after extensive research and public input. Third, it would have been 

inappropriate for the state or its districts to have had rules in place prior to the fires requiring 

specific approaches towards management of wildfires once ignited, given that wildfire situations 

occur without warning of their time or locations, such that resources to manage them cannot be 

deployed in advance and therefore it would be unreasonable to expect that such rules could 

always be adhered to by fire managers. Fourth, once the fires had started, it is reasonable that 

those responsible for managing them should have considered protection of human life and 

property to be their priorities, and it is reasonable that the state did not attempt to influence their 

decisions more towards minimization of ozone precursor emissions. The multiagency report 

“2008 Fire Siege” also states that the firefighting efforts for this “unprecedented” fire event were 

large and extensive – by July 13, over 20,000 firefighters, from as far away as Australia and New 

Zealand, were engaged in firefighting operations – but that still “[w]eather and fuel conditions and 

competition for resources made fire control efforts difficult.”

5

Therefore, EPA agrees with CARB 

that the event (ozone precursor emissions from the 2008 Lightning Wildfire Complex) was not 

reasonably controllable or preventable (see demonstration section 5B in CARB’s March 2011 

Submittal). 

 

4

72 FR at 13569; see also Approval and Promulgation of Implementation Plans; Designation of Areas for Air 

Quality Planning Purposes; State of California; PM–10; Affirmation of Determination of Attainment for the San 

Joaquin Valley Nonattainment Area; Final Rule, 73 FR 14687, 14702 (March 19, 2008); and Approval and 

Promulgation of Implementation Plans; Designation of Areas for Air Quality Planning Purposes; State of California; 

PM–10; Affirmation of Determination of Attainment for the San Joaquin Valley Nonattainment Area; Proposed 

Rule, 72 FR 49046, 49051 (Aug. 27, 2007).

5 California Department of Forestry and Fire Protection, “2008 Fire Siege” (retrieved April 1, 2011) available at 

http://www.fire.ca.gov/fire_protection/downloads/siege/2008/2008FireSiege_full-book_r6.pdf (Multiagency Fire 

Investigation Report).
7

5.0 Clear Causal Relationship 

Section 319 of the CAA and 40 CFR § 50.14(c)(3)(iv)(B) 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. 

The relationship between wildfire emissions and resulting air quality impacts is complicated. 

Fire can generate ozone precursors, but it can also reduce solar radiation needed to drive ozone 

formation. Also, fire plumes containing ozone and ozone precursors can pass over a monitoring 

site without mixing down to ground level and affecting the monitored concentration. Therefore, 

to demonstrate the clear causal relationship between the wildfire emissions and the 1-hour O3

exceedances at Folsom, CARB demonstrated that (1) the wildfires occurred, (2) these wildfires 

produced emissions that were transported to the Folsom monitor, and (3) these wildfire 

emissions elevated ozone concentrations measured at the Folsom monitor.

Demonstration that the Wildfires Occurred

Section 2 and Appendix A of CARB’s March 2011 Submittal provide an extensive description of 

the fires. The evidence presented includes a map and tables showing the location of the fire 

complexes burning in northern California at this time and average distances from Folsom, and 

satellite images showing smoke plumes on June 23, June 27 and July 10, 2008. Appendix F of 

the state’s demonstration also includes numerous news reports of the fires throughout the 

summer of 2008. 

Demonstration that Wildfire Emissions Were Transported to the Folsom Monitor

CARB’s demonstration presents several types of evidence to show that the fire emissions 

reached the Folsom monitor. First, an analysis of the meteorology summarized in sections 3.C.1, 

3.D.1 and 3.E.1 shows that conditions were favorable for the transport of emissions from fires in 

the Coastal and Sierra Nevada Mountain Ranges surrounding the northern part of the Sacramento 

Valley to Folsom (see Appendices B, C and D of the March 2011 Submittal for a detailed 

analysis). Satellite images show smoke over the entire Sacramento Valley on these three days 

and observations at the airports in the area confirm that the wildfire smoke was present at the 

surface, enough to impact visibility. 

Because PM2.5 is directly emitted during combustion and because there are filter-based PM2.5

monitoring sites in the Sacramento region, CARB used PM2.5 sampling data to demonstrate that 

emissions from the wildfires reached ground level monitors in the Sacramento region. The State 

identified “surrogate” days for each fire-affected day in the request, based on similar 

meteorological indicators and local- to synoptic-scale conditions. These surrogate days provide 

an indication of what the air quality would have been without the presence of emissions from 

wildfires (see Appendix X of the March 2011 Submittal). In comparison to the surrogate days, 

24-hour PM2.5 concentrations on June 23, June 27, and July 10, as well as throughout the fireaffected months, were much higher than normal and widespread throughout the area (see Section 

3, Figures 9, 17 and 24 of the March 2011 Submittal). Levoglucosan and organic carbon 

concentrations while the fires were burning were evaluated from PM2.5 filter samples collected 

during June and July at monitoring stations close to Folsom showed elevated levels as well. This 

evidence of elevated PM2.5 concentrations and anomalous PM2.5 composition demonstrates 
8

clearly that emissions from the wildfire were present at ground level throughout the Sacramento 

area during June and July 2008.

In order to show that the wildfire emissions transported to the monitor also contained the 

expected ozone precursors, NOx and VOCs, CARB compared the monitored NOx concentrations 

on the surrogate days and the fire-affected days. The fire-affected days show regionally elevated 

NOx, similar to the 24-hour PM2.5 observation. Column NO2 satellite measurements also show 

the same elevated pattern. Observed hourly PM2.5 surface concentrations, which increase as the 

height of the mixing layer decreases, are provided as evidence that the NO2 concentration is also 

likely to increase at the surface. 

Demonstration that Wildfire Emissions Elevated Ozone at the Folsom Monitor 

As CARB discusses in section 2 of the March 2011 Submittal, emissions from wildfires can 

increase or decrease ambient ozone concentrations. While the research on this topic is ongoing, 

it is clear that relevant factors include: (i) the fuel being burned; (ii), whether smoke is thick 

enough to inhibit the photochemical production of ozone; and (iii) the distance from the location 

where the fire is producing emissions to the location where the air quality impact is measured. 

CARB argues that the sources of the fire emissions were too far away from the monitoring 

stations for the plume to contain enough NO remaining to titrate the ozone and have an ozonelowering affect on air quality at Folsom. CARB also presents evidence of a regional increase in 

ozone that is consistent with the extent and timing of the observed increase in PM2.5, indicating 

that it is more likely that the fire emissions increased ozone (due to increased precursors), rather 

than decreased ozone (due to decreased solar insolation or increased ozone titration).

Section 2 of the March 2011 Submittal depicts the evidence that ozone was elevated throughout 

the Sacramento air basin on the fire-affected days. Table 4, which lists exceedances that 

occurred at nearby monitoring sites from June 25 through August 13, 2008 while the fires were 

burning, shows that there were more exceedances than normal, all likely affected by wildfire 

emissions. Also, Figures 15, 21, and 28 in Section 3 of the March 2011 Submittal are maps 

comparing 1-hour maximum ozone concentrations on June 23, June 27 and July 10, 2008 to their

surrogate days, which exhibit significant regional increases in ozone concentrations on fireaffected days. The measured 1-hour maximum ozone concentrations at Folsom on the three 

surrogate days were below the NAAQS, and were only 49 to 65 percent of the concentrations 

measured on the corresponding fire-affected days. Lastly, the minimum ozone concentrations on 

June 27 and July 10, 2008 were higher than normal. These concentrations occurred early in the 

morning, before daily ozone production had fully started, indicating that there was anomalously 

high ozone carryover from previous days. 

Conclusion

In conclusion, the evidence contained in CARB’s March 2011 Submittal indicates that there was 

an anomalous increase in ozone on these days and that the cause that most likely accounts for 

those differences was the presence of wildfire emissions. EPA has determined that the weight of 

evidence analysis presented in section 3 of CARB’s March 2011 submittal adequately 

demonstrates a clear causal relationship between the wildfire emissions, which constitute the 

event, and the 1-hour ozone exceedances at Folsom on June 23, June 27, and July 10, 2010.
9

6.0 Concentration in Excess of Normal Historical Fluctuations

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

associated with a measured concentration in excess of normal historical fluctuations.” In section 

3F of the March 2011 Submittal, CARB provided a plot of the daily ozone maximum 

concentration at Folsom for the high ozone seasons (May through October) from 2004 through 

2008. June 23, June 27, and July 10, 2008 all fall above the 99th percentile of data from these five 

ozone seasons at this site.

While there is no specific threshold test for this requirement, the statistical analysis presented 

strengthens the overall weight of evidence for the exceptional events demonstration and fulfills

the requirement of 40 CFR §50.14(c)(3)(iv)(C) that there be evidence showing the event is 

associated with measured concentrations in excess of normal historical concentrations. 

7.0 No Exceedances But For the Event

Pursuant to 40 CFR §50.14(c)(3)(iv)(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 air quality impact from the event,6though such 

information is often useful. EPA recognizes that since effects of a fire on ozone are complex, 

meeting this requirement may be more difficult for many, if not all ozone fire exceptional events. 

This is primarily due to the fact that wildfires often occur during the same seasons that exhibit 

high ozone caused by anthropogenic precursor emissions, making it difficult to separate the 

wildfire contribution from a high ozone event that would have occurred without the fire.

However, this is still a required showing.

Section 4 of the March 2010 Submittal presents the evidence used to demonstrate the 

requirement of 40 CFR §50.14(c)(3)(iv)(D). The first method of analysis that CARB uses is a 

regression model developed for Sacramento County that predicts maximum ozone concentrations 

in the county from various meteorological parameters. Since the maximum concentration of 

ozone in Sacramento County occurs at Folsom for the general wind direction observed on these 

three days, EPA agrees that the model can be used to predict what the 1-hour maximum ozone 

concentrations at Folsom may have been on these three days without the emissions from the 

wildfire. CARB discusses the inherent uncertainties with this method and their potential impact 

on the predicted results in Section 4B and Appendix X of the March 2011 Submittal. Despite 

these uncertainties, EPA agrees that the evidence that the predicted 1-hour maximum ozone 

concentrations from the regression model are below the NAAQS for these three days (ranging 

from 77 to 95 ppb) indicates that the ozone concentrations at Folsom would not have exceeded 

the 1-hour O3 NAAQS without the impact of the wildfire emissions.

In order to evaluate the performance and uncertainties in the regression model results, CARB

calculated the 95th percentile of the daily differences between the observed and predicted ozone 

concentrations for May through October 2007 and May through June 22 and September 2008. 

This value, 27.6 ppb, was then added to the daily predicted concentrations to give a conservative 

 

6

72 FR at 13570.
10

statistical threshold of expected maximum concentration, called a regular upper limit. In general, 

this regular upper limit should only be exceeded 5 percent of the time, but during the fire period, 

it was exceeded 16 of the 34 days (47 percent). This is further evidence supporting the 

conclusion that ozone was anomalously elevated at Folsom during the fire period, and that since 

there are no known variations in anthropogenic sources during this time, it is very likely that the 

wildfire emissions constituted the anomalous source.

The 1-hour ozone maximum concentrations measured on the surrogate days as described in 

section 5 of this document were below the NAAQS and were similar in magnitude to the 

concentrations predicted by the regression model analysis (see table 8 in section 4.C of the 

March 2011 Submittal), providing additional support for the conclusion that without the 

emissions from the wildfire, the ozone concentrations on these three days would not have 

exceeded the 1-hour standard.

Another method used by CARB to estimate the expected 1-hour ozone maximum concentration 

without the influence of the wildfire emissions is outlined in section 4.C of their March 2011 

demonstration.7 This analysis identifies both meteorological indicators generally necessary to 

produce 8-hour ozone concentrations greater than 95 ppb and the synoptic-scale conditions that 

the Sacramento Metropolitan Air Quality Management District has determined are conducive to 

typical high ozone events. These indicators, referred to as the rules of thumb, are specifically 

developed for a certain 8-hour ozone threshold in Sacramento County, but can give a rough 

indication of the likelihood of a 1-hour ozone maximum above the NAAQS at Folsom. 

While the synoptic-scale conditions are different for typical high ozone events and for the days

requested for exclusion, some of the meteorological indicators on the wildfire-affected days are

conducive to 8-hour ozone concentrations above 95 ppb. Therefore, to address the uncertainties 

in using the rules of thumb to predict 1-hour ozone, CARB evaluated the likelihood of a 1-hour 

ozone exceedance occurring on days with 8-hour ozone concentrations above 95 ppb. The

analysis shows that there are no 1-hour ozone exceedances on days with 8-hour concentrations 

below 95 ppb between 2004 and 2010. Also, seven of the 46 days with 8-hour concentrations 

above 95 ppb from 2004 to 2010 had corresponding 1-hour ozone exceedances, six of which 

were or may have been affected by wildfire emissions. CARB argues that this shows that even 

for days in Sacramento County with 8-hour ozone concentrations above 95 ppb, a 1-hour ozone

exceedance is very unlikely.

Considering the weight of evidence, the evaluation for all three days provides sufficient evidence 

to establish that there would not have been exceedances at the Folsom monitor on June 23, June 

27 and July 10, 2008 but for the event.

8

 

 

7

See Appendix Y: Evaluation of Exceptional Events Based on Rules of Thumb of the March 2010 Submittal for the 

complete analysis.

8 EPA notes, however, that this conclusion is based on the facts and circumstances that pertain here, and application 

of the EER to other fire events will depend similarly on the specific circumstances of those events.
11

8.0 Procedural Requirements

The EER at 40 CFR §50.14(c)(2) requires that data claimed to be due to an exceptional event 

must both be flagged in the AQS database and an initial description of the event must be 

provided to EPA by July 1 of the year following the event. The EER at 40 CFR §50.14(c)(3)(i) 

requires that the State submit a demonstration to EPA within three years of the event that has 

been subject to public notice and opportunity for comment, and that any public comments be 

submitted along with the demonstrations. 

CARB flagged the events in AQS in accordance with 40 CFR §50.14. CARB issued its 

demonstration for public notice on July 29, 2009. Notices were published in the following 

counties that comprise the Sacramento Regional Ozone Nonattainment area: Sacramento, El 

Dorado, Placer, Yolo, Solano and Sutter. Two public comments were received that focused on 

the issue of fire management. The District has included these comments and the District’s 

responses to these comments in Appendix G of the March 2011 submittal. The District’s 

responses highlight the “Wildland Fire Use Coordination and Communication Protocol” that is 

already in place to manage the forests and minimize smoke impacts. On September 17, 2009, 

CARB submitted their demonstration for the 2008 wildfire ozone events in the Sacramento 

Regional Ozone Nonattainment Area. CARB sent additional clarification to EPA via email on 

March 30, 2011.

9.0 Conclusion

Documentation submitted by CARB claims that emissions from the summer 2008 wildfires 

elevated ozone levels throughout the Sacramento Regional Ozone Nonattainment Area and 

caused exceedances of the 1-hour Ozone NAAQS at the Folsom monitoring station on three 

days. EPA reviewed the weight of evidence provided by CARB to demonstrate that the 

exceedances at the Folsom monitor on June 23, June 27, and July 10, 2008 meet the criteria in 

the EER for the purposes of EPA’s concurrence on the flagging of the data for these days. While 

the information and analyses presented in CARB’s submittal documents do not represent the 

entire suite of possible evidence for exceptional event packages, and additional or alternate 

evidence may be necessary to make an exceptional event determination for other wildfire or 

other types of events, in this particular instance EPA finds that the weight of evidence is 

sufficient for concurrence on the flagging of the data for the Folsom monitor on June 23, June 

27, and July 10, 2008. These concurrences do not constitute final EPA action to exclude these 

data from consideration for purposes of determining the attainment status of the area. Final

actions will come only after EPA completes notice and comment rulemaking on those 

determinations.