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

ENVIRONMENTAL PROTECTION 

AGENCY 

40 CFR Parts 50 and 51 

[EPA–HQ–OAR–2005–0159; FRL–8289–5] 

RIN 2060–AN40 

Treatment of Data Influenced by 

Exceptional Events 

AGENCY: Environmental Protection 

Agency (EPA). 

ACTION: Final rule. 

SUMMARY: This action finalizes a rule to 

govern the review and handling of air 

quality monitoring data influenced by 

exceptional events. Exceptional events 

are events for which the normal 

planning and regulatory process 

established by the Clean Air Act (CAA) 

is not appropriate. In this rulemaking 

action, EPA is finalizing the proposal to: 

Implement section 319(b)(3)(B) and 

section 107(d)(3) authority to exclude 

air quality monitoring data from 

regulatory determinations related to 

exceedances or violations of the 

National Ambient Air Quality Standards 

(NAAQS) and avoid designating an area 

as nonattainment, redesignating an area 

as nonattainment, or reclassifying an 

existing nonattainment area to a higher 

classification if a State adequately 

demonstrates that an exceptional event 

has caused an exceedance or violation 

of a NAAQS. The EPA is also requiring 

States to take reasonable measures to 

mitigate the impacts of an exceptional 

event. 

DATES: This final rule is effective May 

21, 2007. 

ADDRESSES: The EPA has established a 

docket for this action under Docket ID 

No. EPA–HQ–OAR–2005–0159. All 

documents in the docket are listed on 

the http://www.regulations.gov Web 

site. Although listed in the index, some 

information is not publicly available, 

i.e., confidential business information 

(CBI) or other information whose 

disclosure is restricted by statute. 

Certain other material, such as 

copyrighted material, is not placed on 

the Internet and will be publicly 

available only in hard copy form. 

Publicly available docket materials are 

available either electronically through 

http://www.regulations.gov or in hard 

copy at the OAR Docket, EPA/DC, EPA 

West, Room 3334, 1301 Constitution 

Ave., NW., Washington, DC. The Public 

Reading Room is open from 8:30 a.m. to 

4:30 p.m., Monday through Friday, 

excluding legal holidays. The telephone 

number for the Public Reading Room is 

(202) 566–1744, and the telephone 

number for the Air and Radiation 

Docket and Information Center is (202) 

566–1742. 

FOR FURTHER INFORMATION CONTACT: 

General questions regarding the final 

rule should be addressed to Mr. Larry D. 

Wallace, PhD, Office of Air Quality 

Planning and Standards, Air Quality 

Policy Division, Mail Code C539–01, 

Research Triangle Park, NC 27711; 

telephone (919) 541–0906, and e-mail 

address wallace.larry@epa.gov. 

Questions concerning technical and 

analytical issues related to this final rule 

should be addressed to Mr. Neil Frank, 

Office of Air Quality Planning and 

Standards, Air Quality Assessment 

Division, Mail Code C304–01, Research 

Triangle Park, NC 27711; telephone 

(919) 541–5560, and e-mail address 

frank.neil@epa.gov. 

SUPPLEMENTARY INFORMATION: 

I. General Information 

A. Does This Action Apply to Me? 

Regulated Entities. This final rule will 

affect State and local air quality 

agencies. This rule may also affect 

Tribal air quality agencies that have 

implemented air quality monitoring 

networks or have authority to 

implement air quality programs. 

This list is not intended to be 

exhaustive, but rather provides a guide 

for readers regarding entities likely to be 

regulated by this action. This list gives 

examples of the types of entities EPA is 

now aware could potentially be 

regulated by this action. Other types of 

entities not listed could also be affected. 

To determine whether your facility, 

company, business, organization, etc., is 

regulated by this action, you should 

examine the applicability criteria in 

section IV of this preamble. If you have 

any questions regarding the 

applicability of this action to a 

particular entity, consult the people 

listed in the preceding section. 

B. How Is This Preamble Organized? 

Table of Contents 

The following is an outline of the 

preamble. 

I. General Information 

A. Does This Action Apply to Me? 

B. How Is This Preamble Organized? 

II. Preamble Glossary of Terms and 

Acronyms 

III. Background and Purpose of This 

Rulemaking 

A. Legislative Requirements 

B. Historical Experience Concerning 

Exceptional and Natural Events 

IV. This Final Action 

A. To Whom and to What Pollutants Does 

This Rule Apply? 

B. How Does This Rule Relate to Indian 

Tribes? 

C. Comments Submitted on the Proposed 

Rule 

D. What Is an Exceptional Event? 

E. Examples of Exceptional Events 

1. Chemical Spills and Industrial 

Accidents 

2. Structural Fires 

3. Exceedances Due to Transported 

Pollution 

4. Exceedances Due to a Terrorist Attack 

5. Natural Events 

a. Natural Disasters and Associated CleanUp Activities 

b. Volcanic and Seismic Activities 

c. High Wind Events 

d. Wildland Fires 

e. Stratospheric Ozone Intrusions 

6. Prescribed Fire 

V. The Management of Air Quality Data 

Affected by Exceptional Events 

A. Flagging of Data in the AQS Database 

1. Background 

2. Final Rule 

3. Comments and Responses 

B. What Does It Mean for an Event to 

‘‘Affect Air Quality’’? 

1. Background 

2. Final Rule 

3. Comments and Responses 

C. Use of a ‘‘But For’’ Test 

1. Background 

2. Final Rule 

3. Comments and Responses 

D. Schedules and Procedures for Flagging 

and Requesting Exclusion of Data 

1. Background 

2. Final Rule 

3. Comments and Responses 

E. Exclusion of Entire 24-Hour Value as 

Opposed to a Partial Adjustment of the 

24-Hour Value 

1. Background 

2. Final Rule 

3. Comments and Responses 

F. What Should States Be Required To 

Submit in Their Exceptional Events 

Demonstrations? 

1. Background 

2. Final Rule 

3. Comments and Responses 

G. Public Availability of Air Quality Data 

and Demonstrations Related to 

Exceptional Events 

1. Background 

2. Final Rule 

3. Comments and Responses 

VI. Additional Requirements 

A. Requirements for States To Provide 

Public Notification, Public Education, 

and Appropriate and Reasonable 

Measures To Protect Public Health 

1. Background 

2. Final Rule 

3. Comments and Responses 

VII. Special Treatment of Certain Exceptional 

Events Under This Final Rule 

A. Volcanic and Seismic Activities 

1. Background 

2. Final Rule 

B. High Wind Events 

1. Background 

2. Final Rule 

C. Stratospheric Ozone Intrusion 

1. Background 

2. Final Rule 

VIII. Treatment of Fireworks Displays 


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Federal Register / Vol. 72, No. 55 / Thursday, March 22, 2007 / Rules and Regulations 13561 

1The U.S. Environmental Protection Agency. 

2All subsequent references to section 319 of the 

CAA in this proposal are to section 319 as amended 

by SAFE–TEA–LU unless otherwise noted. 

3While this document refers primarily to States 

as the entity responsible for flagging data impacted 

by exceptional events, other agencies, such as local 

or Tribal government agencies, may also have 

standing to flag data as being affected by these types 

of events, and the criteria and procedures that are 

discussed in this rulemaking also apply to these 

entities. 

A. Background 

B. Final Rule 

C. Comments and Responses 

IX. Statutory and Executive Order Reviews 

A. Executive Order 12866: Regulatory 

Planning and Review 

B. Paperwork Reduction Act 

C. Regulatory Flexibility Act 

D. Unfunded Mandates Reform Act 

E. Executive Order 13132: Federalism 

F. Executive Order 13175: Consultation 

and Coordination With Indian Tribal 

Governments 

G. Executive Order 13045: Protection of 

Children From Environmental Health 

and Safety Risks 

H. Executive Order 13211: Actions That 

Significantly Affect Energy Supply, 

Distribution, or Use 

I. National Technology Transfer 

Advancement Act 

J. Congressional Review Act 

K. Petitions for Judicial Review 

II. Preamble Glossary of Terms and 

Acronyms 

The following are abbreviations of 

terms used in the preamble. 

ARM Approved Regional Methods. 

AQS Air Quality System. 

BACM Best Available Control 

Measures. 

CAA Clean Air Act. 

CAAA Clean Air Act Amendments. 

EPA Environmental Protection 

Agency. 

FEM Federal Equivalent Methods. 

FIP Federal Implementation Plan. 

FR Federal Register. 

FRM Federal Reference Methods. 

NAAQS National Ambient Air Quality 

Standards. 

NEAP Natural Events Action Plan. 

NEPA National Environmental Policy 

Act. 

NTTA National Technology Transfer 

Advancement Act of 1995. 

OAQPS Office of Air Quality Planning 

and Standards. 

OMB Office of Management and 

Budget. 

PM Particulate matter. 

PM10 Particles with a nominal mean 

aerodynamic diameter less than or 

equal to 10 micrometers. 

PM10¥2.5 Particles with a nominal 

mean aerodynamic diameter greater 

than 2.5 micrometers and less than or 

equal to 10 micrometers. 

PM2.5 Particles with a nominal mean 

aerodynamic diameter less than or 

equal to 2.5 micrometers. 

RACM Reasonably Available Control 

Measures. 

SIP State Implementation Plan. 

SAFE–TEA–LU Safe Accountable 

Flexible Efficient-Transportation 

Equity Act—A Legacy for Users. 

SMP Smoke Management Program. 

TAR Tribal Authority Rule. 

TIP Tribal Implementation Plan. 

UMRA Unfunded Mandates Reform 

Act. 

USDA U.S. Department of Agriculture. 

VCS Voluntary Consensus Standards. 

III. Background and Purpose of This 

Rulemaking 

A. Legislative Requirements 

We 1 are finalizing a rule to govern the 

review and handling of air quality 

monitoring data influenced by 

exceptional events. As discussed below, 

these are events for which the normal 

planning and regulatory process 

established by the CAA is not 

appropriate. Section 319 of the CAA, as 

amended by section 6013 of the Safe 

Accountable Flexible EfficientTransportation Equity Act: A Legacy for 

Users (SAFE–TEA–LU) of 2005, 

required EPA to publish the proposed 

rule in the Federal Register no later 

than March 1, 2006.2 Further, EPA must 

issue this final rule no later than 1 year 

from the date of proposal. The EPA 

published the proposed rule on March 

10, 2006 (See 71 FR 12592). 

In this final rule, EPA is establishing 

procedures and criteria related to the 

identification, evaluation, 

interpretation, and use of air quality 

monitoring data related to any NAAQS 

where States petition EPA to exclude 

data that are affected by exceptional 

events. 

Section 319 defines an event as an 

exceptional event if the event affects air 

quality; is an event that is not 

reasonably controllable or preventable; 

is an event caused by human activity 

that is unlikely to recur at a particular 

location or a natural event; and is 

determined by EPA to be an exceptional 

event. The statutory definition of 

exceptional event specifically excludes 

stagnation of air masses or 

meteorological inversions; a 

meteorological event involving high 

temperatures or lack of precipitation; or 

air pollution relating to source 

noncompliance. 

Section 319(b)(3)(B)(i) requires a State 

air quality agency to demonstrate 

through ‘‘reliable, accurate data that is 

promptly produced’’ that an exceptional 

event occurred.3 Section 319(b)(3)(B)(ii) 

requires that ‘‘a clear causal 

relationship’’ be established between a 

measured exceedance of a NAAQS and 

the exceptional event demonstrating 

‘‘that the exceptional event caused a 

specific air pollution concentration at a 

particular location.’’ In addition, section 

319(b)(3)(B)(iii) requires a public 

process to determine whether an event 

is an exceptional event. Finally, section 

319(b)(3)(B)(iv) requires criteria and 

procedures for a Governor to petition 

the Administrator to exclude air quality 

monitoring data that is directly due to 

exceptional events from use in 

determinations with respect to 

exceedances or violations of the 

NAAQS. 

The term exceedance refers to a 

measured or modeled concentration 

greater than the level of one or more for 

a pollutant. The NAAQS are also set 

with particular averaging periods (e.g., 3 

years for ozone and PM2.5) such that a 

violation of the NAAQS for ozone and 

PM2.5 requires an average annual 

concentration level specified by 

appendix I and N to 40 CFR 50 to be 

greater than the level of the NAAQS. 

Public comments favored the 

consideration of data contributing to 

both exceedances and violations for data 

exclusion under this Rule. As discussed 

in section V.C, exceedances of any 

NAAQS will be eligible for 

consideration for data exclusion and 

any data contributing to violations of 

daily or sub-daily standards will also be 

eligible for consideration (e.g. 8-hour or 

24-hour standards). Data contributing to 

annual violations without being 

exceedances themselves are considered 

too close to background air quality 

levels for exclusion under this Rule. 

Section 319 also contains a set of five 

principles for EPA to follow in 

developing regulations to implement 

section 319: 

(i) Protection of public health is the highest 

priority; 

(ii) Timely information should be provided 

to the public in any case in which the air 

quality is unhealthy; 

(iii) All ambient air quality data should be 

included in a timely manner in an 

appropriate Federal air quality database that 

is accessible to the public; 

(iv) Each State must take necessary 

measures to safeguard public health 

regardless of the source of the air pollution; 

and 

(v) Air quality data should be carefully 

screened to ensure that events not likely to 

recur are represented accurately in all 

monitoring data and analyses (42 U.S.C. 

7619(b)(3)(A)). 

In adopting revisions to section 319, 

Congress sought to provide statutory 

relief to States to allow them to avoid 

being designated as nonattainment or to 

avoid continuing to be designated 


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13562 Federal Register / Vol. 72, No. 55 / Thursday, March 22, 2007 / Rules and Regulations 

4 ‘‘Guideline for Interpretation of Air quality 

Standards,’’ U.S. Environmental Protection Agency, 

Office of Air quality Planning and Standards, 

Research Triangle Park, N.C. OAQPS No. 1.2–008 

(Revised February 1977). The guidance indicated 

the need for a data flagging system which would 

require the submittal of detailed information 

establishing that a violation was due to 

uncontrollable natural sources and that the 

information could be used in decision making 

related to the feasibility of modifying control 

strategies. 

5Federal Register (52 FR 24667), July 1, 1987. 

6Memorandum from Mary D. Nicols, Assistant 

Administrator for Air and Radiation, to EPA 

Regional Offices entitled, ‘‘Areas Affected by PM10

Natural Events,’’ May 30, 1996. 

7 ‘‘Guideline on Data Handling Conventions for 

the PM NAAQS,’’ United States Environmental 

Protection Agency, Office of Air Quality Planning 

and Standards, Research Triangle Park, NC 27711, 

EPA–454/R–98–017, December 1998. 

8Following the promulgation of this rule, it is 

EPA’s intention to begin the process to revise the 

‘‘Interim Air Quality Policy on Wildland and 

Prescribed Fires’’ in calendar year 2007 to update 

the policy and to ensure that the policy is 

consistent with this final rulemaking action. In 

addition, it is EPA’s intent that agricultural 

prescribed burning will be addressed when this 

policy is updated and will also address basic smoke 

management practices. 

nonattainment as a result of exceptional 

events in appropriate circumstances. To 

accomplish this goal, Congress 

enumerated certain minimum 

requirements for this rulemaking. In 

addition, Congress provided certain 

statutory principles for EPA to follow in 

promulgating regulations to exclude 

data affected by exceptional events. 

B. Historical Experience Concerning 

Exceptional and Natural Events 

Since 1977, EPA guidance and 

regulations have either implied or 

documented the need for a flagging 

system for data affected by an 

exceptional event. The first EPA 

guidance related to the exclusion or 

discounting of data affected by an 

exceptional event was an Office of Air 

Quality Planning and Standards 

(OAQPS) guidance document entitled, 

‘‘Guideline for the Interpretation of Air 

Quality Standards,’’ Guideline No. 1.2–

008 (revised February 1977).4

In July 1986, EPA issued the guidance 

entitled, ‘‘Guideline On the 

Identification and Use of Air Quality 

Data Affected By Exceptional Events’’

(the Exceptional Events Policy). The 

Exceptional Events Policy provided 

criteria for States to use in making 

decisions related to identifying data that 

have been influenced by an exceptional 

event. 

In addition to the Exceptional Events 

Policy, on July 1, 1987, EPA 

promulgated the NAAQS for PM10

(particulate matter with an aerodynamic 

diameter of 10 micrometers or less), 

which also addressed the issue of 

excluding or discounting data affected 

by exceptional events.5 Appendix K of 

that rule allows for special 

consideration of data determined to be 

affected by an exceptional event. 

Section 2.4 of appendix K authorizes 

EPA to discount from consideration in 

making attainment or nonattainment 

determinations air quality data that are 

attributable to ‘‘an uncontrollable event 

caused by natural sources’’ of PM10, or 

‘‘an event that is not expected to recur 

at a given location.’’ Section 2.4 of 

appendix K, together with EPA 

guidance contained in the Exceptional 

Events Policy, describes the steps that 

should be taken for flagging PM10 data 

that a State believes are affected by an 

exceptional or natural event. 

In 1990, section 188(f) was added to 

the CAA. This section of the CAA 

provided EPA authority to waive either 

a specific attainment date or certain 

planning requirements for serious PM10

nonattainment areas that are affected by 

nonanthropogenic sources. In response 

to section 188(f), and in consideration of 

the CAA consequences for areas affected 

by elevated concentrations caused by 

natural events, in 1996 EPA issued a 

policy to address data affected by 

natural events entitled, ‘‘Areas Affected 

by PM10 Natural Events,’’ (the PM10

Natural Events Policy).6

On July 18, 1997, EPA issued a 

revised NAAQS for ozone and a new 

NAAQS addressing PM2.5. For ozone, 

the revised NAAQS provided for an 8- 

hour averaging period (versus 1 hour for 

the previous NAAQS), and the level of 

the standard was changed from 0.12 

ppm to 0.08 ppm (62 FR 38856). For the 

PM2.5 NAAQS, EPA established both a 

new 24-hour standard and a new annual 

standard. In that Federal Register, EPA 

also promulgated appendices I and N to 

40 CFR 50. Appendices I and N 

provided the methodologies for 

determining whether an area is in 

attainment of the 8-hour ozone and 

PM2.5 NAAQS respectively, using 

ambient air quality data. Section 1.0 of 

appendix I, related to the ozone 

standard, addresses the treatment of 

data determined to be influenced 

natural events, and section 1.0(b) of 

appendix N, related to the PM2.5

standard, provides that EPA may give 

special consideration to data 

determined to be affected by an 

exceptional or natural event. 

Appendices K, I, and N, which are 

parts of the NAAQS for the affected 

pollutants as described above, provide 

that, while States must submit all valid 

ambient air quality data to EPA’s Air 

Quality System (AQS) database for use 

in making regulatory decisions, in some 

cases it may be appropriate for EPA to 

exclude, discount, weight, or make 

adjustments to data that have been 

appropriately flagged from calculations 

in determining whether or not an area 

has attained the standard. These 

decisions are to be made on a case-bycase basis using all available 

information related to the event in 

question, and are required to be made 

available to the public for review. It 

should also be noted that, while it 

would be desirable to be able to adjust 

the daily value to exclude only those 

portions of the data that are attributable 

to the exceptional event, due to 

technical limitations, such subtraction 

has not been possible, and EPA’s 

historical practice has been to exclude 

a daily measured value in its entirety 

when that value is found to be largely 

caused by an exceptional event. 

Following the promulgation of the 8- 

hour ozone and the PM2.5 NAAQS, EPA 

provided additional guidance to States 

on how to address data affected by 

exceptional and natural events.7 That 

guidance directed the States to follow 

three specific EPA guidance documents 

in making determinations related to data 

influenced by exceptional and natural 

events: (1) The Exceptional Events 

Policy; (2) The PM10 Natural Events 

Policy; and (3) The Interim Air Quality 

Policy on Wildland and Prescribed 

Fires, Memorandum from Richard D. 

Wilson, Acting Assistant Administrator 

for Air and Radiation, to EPA Regional 

Administrators, May 15, 1998. The 

Interim Air Quality Policy on Wildland 

and Prescribed Fires addressed the 

treatment of air quality monitoring data 

that are affected by wildland and 

prescribed fires that are managed for 

resource benefits.8

IV. This Final Action 

A. To Whom and to What Pollutants 

Does This Rule Apply? 

Under the statutory scheme 

established by the CAA, States are 

primarily responsible for the 

administration of air quality 

management programs within their 

borders. This includes the monitoring 

and analysis of ambient air quality and 

submission of monitoring data to EPA, 

which are then stored in EPA’s AQS 

database. The EPA retains an important 

oversight responsibility for ensuring 

compliance with CAA requirements. 

With respect to the treatment of air 

quality monitoring data, States are 

responsible for ensuring data quality 

and validity and for identifying 

measurements that they believe warrant 

special consideration, while EPA is 


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Federal Register / Vol. 72, No. 55 / Thursday, March 22, 2007 / Rules and Regulations 13563 

9Section IV.G of the preamble to the Proposed 

Rule discussed special considerations relevant to a 

new NAAQS for PM10–2.5 proposed by EPA on 

December 20, 2005. This proposed standard would 

have drawn a distinction between coarse particles 

of urban versus non-urban origin, which raised new 

issues about the handling of exceedances of the 

coarse particle standard caused by exceptional 

events. However, in EPA’s final rule on the PM 

NAAQS, issued September 21, 2006, EPA retained 

the existing 24-hour PM10 standard instead of 

promulgating the proposed PM10–2.5 standard. Thus, 

section IV.G of the preamble to the Proposed Rule 

is no longer relevant and has been removed from 

this Preamble. 

responsible for reviewing and approving 

or disapproving any requests for such 

consideration. Therefore, this final rule 

applies to all States; to local air quality 

agencies to whom a State has delegated 

relevant responsibilities for air quality 

management, including air quality 

monitoring and data analysis; and, as 

discussed below, to Tribal air quality 

agencies where appropriate. This rule 

governs EPA’s actions in reviewing and 

approving or disapproving the relevant 

actions taken or requested by States. 

Where EPA implements air quality 

management programs on Tribal lands, 

this rule would govern those actions as 

well. 

At present, only the NAAQS for ozone 

and particulate matter (PM) contain 

provisions which allow for the special 

handling of air quality data affected by 

exceptional and natural events (40 CFR 

part 50, appendices K, I, and N). The 

language of section 319 of the CAA is 

broad in terms of making its provisions 

applicable to events that ‘‘affect air 

quality’’ and to exceedances or 

violations of ‘‘the national ambient air 

quality standards’’ (42 U.S.C. 

7619(b)(1)(A)(i), (b)(3)(B)(iv)). Thus, its 

provisions can apply to the NAAQS for 

any criteria pollutant. Because the 

NAAQS established for other criteria 

pollutants do not currently contain 

provisions permitting the discounting or 

exclusion of data due to exceptional 

events, we are only applying the 

provisions of this rule initially to ozone 

and PM.9 As we review and consider the 

need for revisions to the NAAQS for 

other pollutants, we will include 

provisions to address exceptional events 

in those NAAQS in accordance with 

section 319, as appropriate at that time. 

Because issuance of a new or revised 

NAAQS will necessitate the initiation of 

the designation process, EPA believes 

that the NAAQS rules are an 

appropriate place to make provisions for 

exceptional events in the evaluation of 

air quality data. In the interim, where 

exceptional events result in exceedances 

or violations of NAAQS that do not 

currently provide for special treatment 

of the data, we intend to use our 

discretion as outlined under section 

107(d)(3) not to redesignate affected 

areas as nonattainment based on these 

events. We also intend to use our 

discretion under this rule to address 

determinations for the ozone standard 

related to the treatment of data 

influenced by both exceptional and 

natural events. Currently, appendix I, 

only addresses the treatment of data 

determined to be influenced by a 

stratospheric ozone intrusion and other 

natural events, but does not address the 

handling of data influenced by other 

exceptional events. 

B. How Does This Rule Relate to Indian 

Tribes? 

Under the CAA and the Tribal 

Authority Rule (TAR), eligible Indian 

Tribes may develop and submit Tribal 

Implementation Plans (TIPs) for EPA 

approval, to administer requirements 

under the CAA on their reservations and 

other areas under their jurisdiction. 

However, Tribes are not required to 

develop TIPs or otherwise implement 

relevant programs under the CAA. The 

EPA has stated that it will continue to 

ensure the protection of air quality 

throughout the nation, including in 

Indian country, and will issue Federal 

Implementation Plans (FIPs) as 

necessary or appropriate to fill gaps in 

program implementation in affected 

areas of Indian country (63 FR 7254, 

7265; February 12, 1998). 

In cases where a Tribal air quality 

agency has implemented an air quality 

monitoring network, which is affected 

by emissions from exceptional events, 

the criteria and procedures identified in 

this final rule may be used to exclude 

or discount data for regulatory purposes. 

Certain Tribes may implement all 

relevant components of an air quality 

program for purposes of meeting the 

various requirements of this rule. In 

some cases, however, a Tribe may 

implement only portions of the relevant 

program and may not be in a position 

to address each of the procedures and 

requirements associated with excluding 

or discounting emissions data (e.g., a 

particular Tribe may operate a 

monitoring network for purposes of 

gathering and identifying appropriate 

data, but may not implement relevant 

programs for the purpose of mitigating 

the effects of exceptional events 

required under this rule). The EPA 

intends to work with Tribes on the 

implementation of this rule, which may 

include appropriate implementation by 

EPA of program elements ensuring that 

any exclusion or discounting of data in 

Indian country areas with air quality 

affected by exceptional events comports 

with the procedures and requirements 

of this rule. 

C. Comments Submitted on the 

Proposed Rule 

The proposed rule on the ‘‘Treatment 

of Data Influenced by Exceptional 

Events’’ was issued on March 10, 2006 

(71 FR 12592). We received 98 letters 

from commenters representing 587 

comments from private citizens, State 

and local governments, industry, 

environmental groups, and Federal 

agencies. Sections V, VI, VII, and VIII of 

this notice describe the primary 

elements and requirements concerning 

the process for the handling of data 

influenced by exceptional events. Each 

section summarizes the relevant issues 

and options discussed in the proposed 

rule and provides the final decisions 

related to the issues for each section. In 

this preamble, we have provided 

responses to certain significant 

comments to elaborate or provide 

clarification for EPA’s decision on an 

issue discussed in the relevant section 

of the rule. We have developed a 

response to comments document which 

addresses all of the timely comments 

received on the proposed rule. 

Following the promulgation of this rule, 

the response to comments document 

will be placed into the docket of this 

rulemaking action for public review 

(See Docket No. EPA–HQ–OAR–2005–

0159). 

D. What Is an Exceptional Event? 

In accordance with the language in 

section 319, EPA is defining the term 

‘‘exceptional event’’ to mean an event 

that: 

(i) Affects air quality; 

(ii) Is not reasonably controllable or 

preventable; 

(iii) Is an event caused by human activity 

that is unlikely to recur at a particular 

location or a natural event; and 

(iv) Is determined by EPA through the 

process established in these regulations to be 

an exceptional event. 

It is important to note that natural 

events, which are one form of 

exceptional events according to this 

definition, may recur, sometimes 

frequently (e.g., western wildfires). For 

the purposes of this rule, EPA is 

defining ‘‘natural event’’ as an event in 

which human activity plays little or no 

direct causal role to the event in 

question. We recognize that over time, 

certain human activities may have had 

some impact on the conditions which 

later give rise to a ‘‘natural’’ air 

pollution event. However, we do not 

believe that small historical human 

contributions should preclude an event 

from being deemed ‘‘natural.’’ In 

adopting section 188(f) of part D, 

subpart 4, of the 1990 amendments to 


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13564 Federal Register / Vol. 72, No. 55 / Thursday, March 22, 2007 / Rules and Regulations 

10The EPA will be revising the list of events 

contained in the AQS database following the 

promulgation of this rule to ensure that the list is 

consistent with the requirements of the rule. 

the CAA, Congress recognized and 

provided for distinctions between these 

types of events with respect to waiver of 

applicable requirements and the 

extension of otherwise applicable 

attainment dates for the PM10 standard. 

In approving section 188(f) of the CAA, 

the House committee of jurisdiction 

discussed a circumstance in which 

recurring emissions from a source 

should be considered to be 

anthropogenic. The House report noted 

EPA statements that, in the cited case, 

high concentrations of dust from a 

lakebed were due to human activity, i.e., 

the long-term diversion of water from a 

lake. (See Pub. L. 101–549, CAA 

Amendments of 1990 House Report No. 

101–290(l), May 17, 1990; and 

discussion of Mono Lake, California 

therein). Also, EPA recognized, in 

recently acting to retain PM10 as a 

measure of coarse particulate, that in 

some instances exceedances of this 

NAAQS ‘‘may be caused in whole or in 

part, by exceptional events, including 

natural events such as windstorms 

* * *. (and that) an exceedance may be 

treated as an exceptional event even 

though anthropogenic sources such as 

agricultural and mining emissions 

contribute to the exceedance.’’ (71 FR 

61216; October 17, 2006). 

In this final rule, EPA also defines the 

term ‘‘exceedance’’ with respect to 

compliance with the NAAQS and 

establishes criteria for determining 

when an event can be said to ‘‘affect air 

quality.’’ We are not finalizing more 

detailed requirements for determining 

when an event is ‘‘not reasonably 

controllable or preventable’’ because we 

believe that such determinations will 

necessarily be dependent on specific 

facts and circumstances that cannot be 

prescribed by rule. 

E. Examples of Exceptional Events 

The EPA believes that the following 

types of events meet the definition of 

exceptional events, as defined above. 

This means that air quality data affected 

by these types of events may qualify for 

exclusion under this rule provided that 

all other requirements of the rule are 

met. By providing the examples listed 

below, EPA is not determining that such 

events are the only types of events that 

may qualify for exclusion under the rule 

as exceptional events. Other events that 

meet the statutory criteria for an 

exceptional event as defined in this rule 

may also qualify for exclusion. The AQS 

user documentation contains a list of 

other similar events that may be flagged 

for special consideration. (http:// 

www.epa.gov/ttn/airs/airsaqs/manuals/ 

qualifiers.htm).10

In addition, in the sections below, we 

have provided responses to certain 

significant comments received during 

the comment period for the proposed 

rule regarding the examples of events 

that may meet the definition of an 

exceptional event in order to elaborate 

upon or provide clarification about what 

constitutes an exceptional event. 

1. Chemical Spills and Industrial 

Accidents 

Emissions that result from accidents 

such as fires, explosions, power outages, 

train derailments, vehicular accidents, 

or combinations of these may be flagged 

as an exceptional event. 

Comments and Responses 

Comment: Several commenters stated 

that ‘‘Chemical Spills and Industrial 

Accidents’’ should generally not be 

considered exceptional events. 

Commenters stated that most industrial 

accidents and chemical spills are 

reasonably controllable and preventable 

with proper planning and mitigation 

efforts. These commenters stated that 

allowing for accidents or spills that 

could have been avoided is inconsistent 

with the CAA. 

Response: It is EPA’s belief that air 

quality data that has been affected by 

emissions from chemical spills, 

industrial accidents, or structural fires 

may be flagged by a State as an 

exceptional event and reviewed by EPA 

for exclusion on a case-by-case basis to 

determine whether it meets the criteria 

for exceptional events as defined in this 

rule. In particular, data influenced by 

chemical spills or industrial accidents 

must be demonstrated to have ‘‘affected 

air quality’’ and must be demonstrated 

to be due to circumstances that were not 

reasonably controllable or preventable 

and are events that are unlikely to recur 

in a particular location. The EPA agrees 

with the commenters that industrial or 

point source emissions due to 

malfunctions or non-compliance would 

not be considered exceptional events 

and should be addressed through the 

normal State Implementation Planning 

process. 

2. Structural Fires 

Structural fires include any accidental 

fire involving a manmade structure. 

Comments and Responses 

Comment: Several commenters 

indicated that ‘‘Structural Fires’’ should 

generally not be considered exceptional 

events. Commenters stated that these 

types of events should be considered as 

emissions from anthropogenic sources 

and handled within the form of the 

respective air quality standards where a 

certain number of exceedances of the 

standards are allowed over a 3-year 

period. Commenters assert that 

structural fires, lasting for several hours, 

are unlikely to cause an area to reach 

the level of nonattainment. In cases 

where structural fires are determined to 

be the cause of a monitored violation of 

the NAAQS, commenters stated that 

EPA should adopt a case-by-case review 

of these events. 

Response: The definition of structural 

fires under this rule pertains to any 

accidental fire involving a manmade 

structure. The EPA believes that 

structural fires could be an exceptional 

event under this rule, provided all other 

requirements of the rule are met, 

because they could ‘‘affect air quality,’’

could be an event that is not 

‘‘reasonably controllable’’ or 

‘‘preventable,’’ and could be events that 

are caused by human activity that are 

unlikely to recur at the same location. 

However, EPA agrees with the 

commenters that these types of events, 

as well as other similar types of events, 

should be reviewed on a case-by-case 

basis to determine whether they meet 

the criteria for an exceptional event as 

defined by this rule. 

3. Exceedances Due to Transported 

Pollution 

Transported pollution, whether 

national or international in origin, and 

whether from natural or anthropogenic 

sources, may cause exceedances eligible 

for exclusion under this rule, as long as 

all of the criteria and requirements 

related to exceptional events are met as 

defined in this rule. For example, States 

may flag, and EPA may exclude, data 

associated with fires occurring outside 

of the borders of the United States, such 

as forest fires in Mexico, Central 

America, and Canada; or transport 

events such as African dust and Asian 

dust which contribute significantly to 

ambient concentrations of a pollutant in 

an area, leading to exceedances or 

violations of a NAAQS. An example of 

interstate transported emissions which 

may be flagged as due to an exceptional 

event would be emissions due to smoke 

from wildfires or wildland fire use fires 

which cause exceedances or violations 

of the NAAQS at monitoring sites in 

other States. Other examples could 

include data affected by emissions from 

mining and agricultural activities when 

such emissions are subjected to longrange transport, and the criteria and 


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requirements related to an exceptional 

event are met as defined in this rule. In 

general, events due to transported 

pollution may be considered on a caseby-case basis. 

Comments and Responses 

Comment: Several commenters 

expressed concern over EPA allowing 

the exceptional events rule to be used to 

exclude data that has been affected by 

emissions emanating from sources 

outside the borders of the United States. 

Response: States may flag data that 

has been affected by sources emanating 

from outside the United States that meet 

the criteria for an exceptional event as 

defined under this rule, including 

requirements for causation and 

documentation. In cases where an area 

is impacted by emissions from sources 

outside of the United States which do 

not meet the criteria for an exceptional 

event under this rule, and these 

emissions contribute to an area being 

designated as nonattainment, the 

emissions may be addressed under 

section 179B of the CAA related to 

‘‘International Border Areas.’’ Section 

179B provides that where a State is 

required to submit a State 

Implementation Plan (SIP) to address 

issues related to a nonattainment 

designation, EPA may approve the SIP 

for the area provided that the plan (1) 

meets all the applicable requirements 

called for under the CAA, other than the 

requirement that the plan demonstrate 

attainment or maintenance of the 

NAAQS, and (2) the SIP must 

demonstrate that the affected area 

would be able to attain the standard by 

the applicable attainment date ‘‘but for’’

emissions emanating from outside the 

United States. 

4. Exceedances Due to a Terrorist Attack 

Emissions that result from a terrorist 

attack such as smoke from fires, dust, 

explosions, power outages, train 

derailments, vehicular accidents, or 

combinations of these may be flagged as 

an exceptional event. 

Comments and Responses 

No comments were received on this 

topic. 

5. Natural Events 

The natural events addressed by this 

final rule are: (1) Natural disasters and 

associated cleanup activities; (2) 

volcanic and seismic activities; (3) high 

wind events; (4) wildfires and wildland 

fire use fires; and (5) stratospheric ozone 

intrusions. The EPA will consider other 

types of natural events on a case-by-case 

basis. 

a. Natural Disasters and Associated 

Clean-Up Activities 

For the purpose of flagging, major 

natural disasters such as hurricanes and 

tornadoes for which State, local, or 

Federal relief has been granted, and 

clean-up activities associated with these 

events, may be considered exceptional 

events. The EPA believes that for a 

major natural disaster, a timeframe up to 

12 months is a reasonable time period 

to allow for clean-up activities 

associated with these types of activities. 

In cases where the damage caused by 

the event is so substantial that a 12- 

month period is inadequate to address 

the clean up that is necessary, a State 

may submit a request to EPA for an 

extension of the 12-month time period. 

The EPA will grant requests for 

extensions of the time period related to 

such events on a case-by-case basis if 

the States submit adequate supporting 

information concerning the reason for 

the extension as well as the length of 

time being requested for the extension. 

Comments and Responses 

Comment: Several commenters 

indicated that EPA should limit the time 

period associated with clean-up 

activities due to a natural disaster. One 

commenter indicated that the 

exceptional events rule as proposed 

would allow States to apply the term 

‘‘natural disaster’’ very broadly to 

include circumstances that would 

circumvent the intent of the CAA. For 

example, declaring an episode of high 

summer temperatures to be a natural 

disaster could potentially allow a State 

to exclude high ozone levels which 

commonly occur during hot weather. 

Response: A time period up to 12 

months for clean-up activities is 

permitted for major natural disasters, 

such as hurricanes and tornadoes, for 

which State, local, or Federal relief has 

been granted, may be flagged for 

exclusion as exceptional events under 

this rule. The clean-up activities 

associated with these types of events 

may also be flagged for exclusion as 

being due to an exceptional event. 

Given the nature of a major natural 

disaster, the 12-month time period 

allowed for clean-up activities following 

such disaster is a reasonable time 

period, and is consistent with the time 

period being allowed for volcanic and 

seismic activities under this rule. The 

period of high summer temperatures 

noted in the comment would not 

represent a major natural disaster, as 

described above, subject to the 12- 

month clean-up period. 

b. Volcanic and Seismic Activities 

Ambient concentrations of particulate 

matter for which volcanic or seismic 

activity caused or significantly 

contributed to high levels of particulate 

matter in an affected area will be treated 

as natural events. While generally not 

occurring frequently, volcanic and 

seismic activity can affect air quality 

data related to the particulate matter 

NAAQS for an extended period of time 

after an event. Volcanic activities can 

contribute to ambient concentrations in 

several ways: it may influence 

concentrations of particulate matter due 

to primary emissions (e.g., ash), and 

emissions of precursor pollutants (e.g., 

sulfur dioxide) that contribute to the 

secondary formation of particulate 

matter. Seismic activity (e.g., 

earthquakes) can also contribute to 

ambient particulate matter 

concentrations by shaking the ground, 

causing structures to collapse, and 

otherwise raising dust which may lead 

to exceedances or violations of the 

NAAQS. 

Comments and Responses 

Comment: Several commenters 

indicated that the rule should provide 

sufficient flexibility for data to be 

excluded where the duration of the 

event may last for a long period of time. 

An example of such an event is where 

volcanic activities last for several days. 

Response: The EPA agrees with the 

commenters and notes that the rule 

allows for States to flag data and submit 

documentation related to events such as 

long-term volcanic and seismic 

activities. States may also submit 

requests to EPA to extend the time 

period up to 12 months for major 

natural disasters, for clean-up activities 

following volcanic and seismic events. 

States are encouraged to submit 

supporting information related to the 

reasons for the requested extension and 

the length of time being requested for 

the extension. 

c. High Wind Events 

High wind events are events that 

affect ambient particulate matter 

concentrations through the raising of 

dust or through the re-entrainment of 

material that has been deposited. In 

some locations, concentrations of coarse 

particles like PM10 are most likely 

affected by these types of events, 

although PM2.5 standards may be 

exceeded under such circumstances as 

well. Section VII.B. also includes a 

discussion of this issue. 

Comments and Responses 

Comment: Several commenters 

suggested that EPA replace the term 


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11As described elsewhere in the preamble, EPA 

is adopting a weight of evidence approach to 

demonstrate that an exceptional event caused an 

exceedance or violation. Therefore, in instances 

where the level of the wind speed results in 

exceedances or violations of particulate matter, for 

data affected by these events to be considered for 

exclusion under the weight of evidence approach, 

a clear causal relationship must be demonstrated 

between the exceedances measured at the air 

quality monitoring site and the high wind event in 

question. EPA will consider in the weight of 

evidence analysis winds that produce emissions 

contributed to by anthropogenic activities that have 

been controlled to the extent possible through use 

of all reasonably available reasonable and 

appropriate measures. 

‘‘high winds’’ with the term ‘‘windgenerated dust’’ because (1) it places the 

emphasis on the natural mechanism, (2) 

dust may become entrained at relatively 

low wind velocities, and (3) the change 

will eliminate confusion between the 

wind speeds associated with a natural 

event and wind speeds needed to 

qualify for a ‘‘high wind’’ exceptional 

event under EPA’s 1986 guidance. 

Response: The EPA is retaining the 

term ‘‘high wind’’ event because it 

accurately connotes the type of natural 

event that should be excluded under 

this rule, as well as the action which 

caused the exceedance or violation of 

the standard. The term also serves as an 

indicator concerning the level of wind 

which caused the exceedance or 

violation of the standard and indicates 

that it was unusually high for the 

affected area during the time period that 

the event occurred. Therefore, States 

must provide appropriate 

documentation to substantiate why the 

level of wind speed associated with the 

event in question should be considered 

unusual for the affected area during the 

time of year that the event occurred. The 

EPA will evaluate such instances on a 

case-by-case basis, including factors 

such as historically typical windspeed 

levels for the season of the year that the 

event is claimed.11

d. Wildland Fires 

Federal land managers have afforded 

recognition to several different types of 

wildland fires (i.e., wildfire, wildland 

fire use fire and prescribed fire), 

depending on their causal 

circumstances and the role that such 

fires play in the affected ecosystems. 

Prescribed fire is addressed more fully 

in the following section. 

The question of what is a natural 

versus an anthropogenic fire has 

particular significance when 

considering the impacts of wildland 

fires (wildfire, wildland fire use fire and 

prescribed fire) on air quality and how 

these impacts should be regarded under 

this rule. A ‘‘wildfire’’ is defined as an 

unplanned, unwanted wildland fire 

(such as a fire caused by lightning), and 

include unauthorized human-caused 

fires (such as arson or acts of 

carelessness by campers), escaped 

prescribed fire projects (escaped control 

due to unforeseen circumstances), 

where the appropriate management 

response includes the objective to 

suppress the fire. In contrast, a 

‘‘wildland fire use’’ fire is the 

application of the appropriate 

management response to a naturallyignited (e.g., as the result of lightning) 

wildland fire to accomplish specific 

resource management objectives in 

predefined and designated areas where 

fire is necessary and outlined in fire 

management or land management plans. 

Using these definitions, we believe 

that both wildfires and wildland fire use 

fires fall within the meaning of ‘‘natural 

events’’ as that term is used in section 

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. 

Comments and Responses 

Comment: In general, commenters 

strongly supported exempting wildfires 

as exceptional events under the rule. 

Response: The EPA acknowledges 

support for the proposal to classify 

wildfires as a potential exceptional 

event. As noted above, the Agency states 

that wildland fires will be excluded as 

exceptional events if they meet the 

criteria and requirements of the 

exceptional events rule. 

Comment: The Agency received 

comments both supporting and 

opposing the proposal allowing 

wildland fire use fires to qualify as an 

exceptional event. 

Response: After reviewing Congress’

revisions to section 319, the various 

Agency policies cited in the proposal, 

and comments received, the Agency has 

determined that wildland fire use fires 

may also qualify as an exceptional 

event. However, these types of fires 

must also meet certain criteria. For 

example, these fires must occur on 

lands that have been designated in fire 

management or land management plans 

as areas where fires are necessary and 

desirable to accomplish specific 

resource management objectives. 

Comment: Many commenters 

supported EPA’s commitment to update 

the 1998 Interim Air Quality Policy on 

Wildland and Prescribed Fires to be 

consistent with this rule. 

Response: The Agency plans to begin 

revising this policy in 2007 as part of its 

overall Fire Strategy after promulgation 

of this rule. 

e. Stratospheric Ozone Intrusions 

Stratospheric ozone intrusion is 

considered to be a natural event. A 

stratospheric ozone intrusion occurs 

when a parcel of air originating in the 

stratosphere, which is at an average 

height of 20 km or 12.4 miles, is 

transported directly to the surface of the 

earth. Stratospheric ozone intrusions are 

very infrequent, localized events of 

short duration. They are typically 

associated with strong frontal passages 

and, thus, may occur primarily during 

the spring season. 

Comments and Responses 

Comment: One commenter stated that 

EPA should update its approach to 

stratospheric events, establish criteria 

by which such events may be 

determined, and credit States for the 

impact of intrusion events on noncompliant ozone monitor readings. 

Response: Stratospheric ozone 

intrusion is identified as a natural event 

under 40 CFR part 50, appendix I, for 

ozone, and will be considered for 

treatment as an exceptional event. 

6. Prescribed Fire 

A ‘‘prescribed fire’’ is defined as any 

fire ignited by management actions to 

meet specific resource management 

objectives. According to existing Federal 

policy, prior to ignition a prescribed fire 

must have an approved prescribed fire 

plan and must meet the National 

Environmental Policy Act (NEPA) 

requirements (where applicable)(see 

National Wildland Fire Coordination 

Group Glossary of Wildland Fire 

Terminology, 2003). For purposes of 

section 319, a prescribed fire cannot be 

classified as ‘‘natural,’’ given the extent 

of the direct human causal connection, 

however, a prescribed fire may meet the 

statutory criteria defined in section 319 

of ‘‘affect[ing] air quality,’’ being 

‘‘unlikely to recur at a particular 

location’’ and is ‘‘not reasonably 

controllable or preventable.’’ The 

determination of whether a prescribed 

fire can be considered an exceptional 

event should be made on a case-by-case 

basis taking into account the factors 

described below. 

A prescribed fire carried out for 

resource management objectives is 

frequently designed to restore essential 

ecological processes of fire and mimic 

fire under natural conditions. As such, 

a prescribed fire’s expected frequency 

can vary widely, depending on the 

natural fire return interval of a 

particular landscape or wildland 

ecosystem. The natural fire return 


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12Basic smoke management practices could 

include, among other practices, steps that will 

minimize air pollutant emissions during and after 

the burn, evaluate dispersion conditions to 

minimize exposure of sensitive populations, actions 

to notify populations and authorities at sensitive 

receptors and contingency actions during the fire to 

reduce exposure of people at such receptors, 

identify steps taken to monitor the effects of the fire 

on air quality, and identify procedures to ensure 

that burners are using basic smoke management 

practices. 

13Although a single qualifying exceptional event 

may affect air quality for multiple days and at 

multiple monitors, the discussions below consider 

an individual demonstration as justifying exclusion 

of a single AQS data point. The EPA encourages 

State submittals to package demonstrations about 

single exceptional events to expedite the review 

process. 

interval can range from once every year 

to less frequently than once in more 

than 200 years. Thus, in many, though 

not all cases, it may be possible to 

demonstrate that the likelihood of 

recurrence is sufficiently small enough 

to show that a prescribed fire under 

these conditions meets the ‘‘unlikely to 

recur at a particular location’’

requirement of the statutory language. 

A prescribed fire may also meet the 

condition of ‘‘not reasonably 

controllable or preventable’’ by 

examining whether there are reasonable 

alternatives to the use of fire in light of 

the needs and objectives to be served by 

it. For instance, there may be a 

significant build-up of forest fuels in a 

particular area that if left unaddressed 

would pose an unacceptable risk of 

catastrophic wildfire, which could 

result in adverse impacts of much 

greater magnitude, duration, and 

severity than would result from careful 

use of prescribed fire. A particular 

ecosystem may also be highly 

dependent on a natural fire return 

interval to maintain a sustainable 

natural species composition. 

Alternatively, pest or disease outbreaks 

in an area may be such that there are no 

reasonable alternatives to prescribed 

fire. In some cases, other legal 

requirements may preclude the use of 

mechanical fuel reduction methods 

such as in designated wilderness or 

National Parks. Where such ecological 

conditions exist, or where mechanical 

or other treatments are not reasonably 

feasible for reasons that include, but are 

not limited to, a lack of access, or severe 

topography, we believe that prescribed 

fire qualifies as being ‘‘not reasonably 

controllable or preventable.’’ Thus, we 

believe that a prescribed fire, conducted 

by Federal, State, Tribal or private 

wildland managers or owners, under the 

conditions described above may qualify 

as an exceptional event. 

In addition, one of the principles 

contained in SAFE–TEA–LU, section 

6013(b)(3)(A), includes the principle 

that States must take necessary 

measures to safeguard public health 

regardless of the source of air pollution. 

We believe it reasonable to tie the 

qualifying criteria for an 

anthropogenically generated prescribed 

fire to State accountability for public 

health protection. Consistent with 

historical practice governed by the 

guidance contained in the ‘‘Interim Air 

Quality Policy on Wildland and 

Prescribed Fires,’’ issued on May 15, 

1998, EPA approval of exceedances 

linked to a prescribed fire used for 

resource management purposes is 

contingent on the State certifying that it 

has adopted and is implementing a 

Smoke Management Program (SMP) as 

described in that policy. A State SMP 

establishes a basic framework of 

procedures and requirements for 

managing smoke from a prescribed fire 

managed for resource benefits. A SMP is 

typically developed by a State or Tribe 

with cooperation and participation by 

wildland managers, both public and 

private, and the general public. As 

reflected in the Interim Air Quality 

Policy on Wildland and Prescribed 

Fires, States are provided flexibility on 

the structure of a SMP. Thus, a SMP can 

be extensive and detailed, or simply 

identify the basic smoke management 

practices for minimizing emissions, and 

controlling impacts from a prescribed 

fire.12 In the proposal to this rule, EPA 

proposed to continue the use of that 

approach. We also proposed to expand 

the criteria for contingent approval to a 

prescribed fire where, in lieu of a SMP, 

basic smoke management practices, that 

minimize emissions and control 

impacts, are being employed by burners. 

In order to protect public health in areas 

where a SMP has not been adopted, in 

the final rule, the Agency has elected to 

expand, on a case-by-case basis, the 

qualifying criteria by which a prescribed 

fire may qualify as an exceptional event. 

In those cases, the Agency will judge on 

a case-by-case basis whether the State 

has ensured that appropriate basic 

smoke management practices have been 

employed in determining whether the 

prescribed fire qualifies as an 

exceptional event. If an exceptional 

event occurs using the basic smoke 

management practices approach, the 

State must undertake a review of their 

approach to ensure public health is 

being protected and must include 

consideration of development of a SMP. 

Comments and Responses 

Comment: Several commenters 

supported classifying prescribed fire as 

qualifying as an exceptional event. 

However, some commenters indicated 

that there should be limitations placed 

on when this type of fire should be 

considered as an exceptional event. A 

number of commenters also 

disapproved of allowing prescribed fire 

to be considered as an exceptional event 

because they believe that this type of 

fire is anthropogenic and does not meet 

the statutory definition of exceptional 

event. Some commenters also favored 

expanding the criteria for contingent 

approval to include instances where 

basic smoke management practices are 

used in lieu of a SMP, while other 

commenters did not favor this 

expansion. 

Response: The EPA believes that a 

prescribed fire may be excluded as an 

exceptional event under this rule only 

in cases where the event meets the 

criteria for an exceptional event as 

defined in this rule, if documentation is 

submitted to show that the fire meets 

the requirement, as described above, of 

‘‘affect[ing] air quality,’’ being ‘‘not 

reasonably controllable or preventable’’

and ‘‘unlikely to recur at location’’ and 

provided the other requirements of the 

rule including, among others, the 

schedules and procedures for flagging 

and demonstration are met. In those 

instances where a prescribed fire meets 

the criteria for an exceptional event, the 

State must also provide appropriate 

documentation to show that a certified 

SMP was in place or that the burner 

employed basic smoke management 

practices and that the appropriate 

practices were being followed at the 

time that the event occurred. Because a 

prescribed fire is an anthropogenic 

source of emissions for purposes of 

section 319, even though it may qualify 

as an exceptional event, a State can 

attempt to limit the health impact of a 

prescribed fire through the thoughtful 

development and implementation of a 

SMP or ensuring that basic smoke 

management practices were employed 

that minimize emissions and control 

impacts from prescribed fires. 

V. The Management of Air Quality Data 

Affected by Exceptional Events 

The EPA proposed that, in order to 

exclude air quality data from 

consideration for regulatory purposes, 

States must follow the procedures, 

timelines, and other requirements 

described in the proposed rule. Under 

the Final Rule, if an event is determined 

to be a qualifying exceptional event 

according to section IV.D, a State, Tribe, 

or designated local agency may petition 

EPA to classify the event as exceptional 

and submit a demonstration to justify 

data exclusion.13 For data exclusion, 

States must clearly identify, or ‘‘flag,’’


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13568 Federal Register / Vol. 72, No. 55 / Thursday, March 22, 2007 / Rules and Regulations 

14 It is EPA’s intention, for purposes of 

consistency with this rule, to review the list of 

exceptional events that are currently in the AQS 

database following the promulgation of the rule. 

data they believe to be influenced by 

such events. The demonstration to 

justify data exclusion shall provide 

evidence that: (a) The event qualifies in 

accordance with section IV.D and with 

EPA policies and guidance for certain 

events as described in section IV.E, (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 an unusual measured 

concentration beyond typical 

fluctuations including background, and 

(d) that there would have been no 

exceedance or violation but for the 

event. 

The SAFE–TEA–LU requirements for 

exclusion of data from exceptional 

events are: (1) The occurrence of the 

exceptional event must be demonstrated 

by reliable and accurate data; (2) the 

State must show that there is a ‘‘clear 

causal relationship’’ between the 

NAAQS exceedances and the event; (3) 

there must be a public review process 

related to the exceptional event 

determination; and (4) the rule must set 

criteria and procedures for States to 

petition EPA to exclude data directly 

affected by an exceptional event. The 

sections below describe how each of 

these requirements must be met. 

The sections below address the 

flagging of data as exceptional events 

that are determined to have affected air 

quality, submittal of demonstrations to 

request data exclusion, public review, 

and the schedule and timing for these 

processes. After an exceptional event 

occurs (judged according to section 

IV.D) and an agency determines that the 

event affected ambient air quality, 

flagging may occur according to section 

V.A. Section V.B describes the 

evaluation of whether or not the event 

affected ambient air quality. Section V.C 

describes the necessary ‘‘but-for’’ test 

that data would have complied with the 

applicable standard but for the 

occurrence of the exceptional event. 

Section V.D explains the schedules and 

procedures for the flagging and 

demonstration submittals, section V.E 

discusses the applicability to hourly 

readings, section V.F states the 

requirements for determination 

submittals if the agency requests EPA to 

exclude the data from consideration for 

regulatory purposes, and section V.G 

describes the public review 

requirements. Some commenters 

suggested that all data occurring from 

exceptional events should be flagged, 

and EPA will allow these flags for 

informational purposes, even if the data 

do not qualify for exclusion. If EPA 

concurs on the exclusion of data from 

qualifying exceptional events, the data 

will be excluded from regulatory 

consideration but will still count toward 

data capture requirements. 

A. Flagging of Data in the AQS Database 

1. Background 

Air quality data are required, 

pursuant to 40 CFR 58.16, to be 

submitted to EPA by each State on a 

calendar quarterly basis, with 

submissions due not later than 90 days 

after the end of a quarterly reporting 

period. Once air quality data have been 

submitted to EPA, it is possible to ‘‘flag’’

specific values for various purposes. 

‘‘Data flagging’’ refers to the act of 

making a notation in a designated field 

of an electronic data record. The 

principal purpose of the data flagging 

system in the AQS database is to 

identify those air quality measurements 

for which special attention or treatment 

is warranted. These include, but are not 

limited to, those measurements that are 

influenced by exceptional events. 

The preamble to the proposed rule 

stated: ‘‘In the case of exceptional 

events, States place the initial flag on 

the data in the AQS database. Following 

an evaluation of the supporting 

documentation, EPA will decide 

whether to concur with the flag; 

concurrence will be marked by the 

placement of a second flag in the AQS 

database by EPA. Once EPA has 

concurred on the flag, the data will be 

excluded from regulatory decisions such 

as determinations of attainment or 

nonattainment.’’

• ‘‘While the flagging of data by the 

State is the first step in an exceptional 

events demonstration, it is insufficient 

by itself to allow for the exclusion of 

data. In order to have EPA concur on a 

flag, States must meet the additional 

requirements described below. As stated 

previously, the State has the 

responsibility to document both the 

occurrence of the event and the causal 

connection to the monitoring data under 

consideration. Because the initial step of 

flagging the data is a relatively simple 

one, States may flag many more days 

than the number of days for which they 

ultimately submit documentation to 

support exclusion.’’

2. Final Rule 

In the case of exceptional events, 

States and Tribes place the initial flag 

on the data in the AQS database, but 

EPA determines the available flags.14

States may also delegate authority to 

local agencies to submit flags and 

documentation. In any event, States 

should work with their local agencies 

for the identification and review of 

exceptional events and consider 

requests to flag data from those 

agencies. At the time the flag is inserted 

into the AQS database, the State must 

also provide an initial description of the 

event in the AQS comment field. This 

initial description should include such 

information as the direction and 

distance from the event to the air quality 

monitor in question, as well as the 

direction of the wind on the day in 

question. The flags, and the initial event 

description, must be inserted into the 

AQS database prior to July 1st following 

the year in which the event occurred. 

Schedules for demonstrations are 

discussed in section V.D. 

Following an evaluation of the 

supporting documentation, EPA will 

make a decision concerning whether to 

concur with the flag; concurrence will 

be marked by the placement of a second 

flag in the AQS database by EPA. If EPA 

has concurred on the flag, the data will 

be excluded from regulatory 

determinations such as determinations 

related to attainment or nonattainment, 

or determinations concerning SIP 

development. The EPA will use the 

second flag to indicate the following 

conditions: EPA concurrence, EPA nonconcurrence, and documentation 

submitted with EPA decision pending. 

While flagging of the data in the AQS 

database by the affected State, local, or 

Tribe authority is the first step in an 

exceptional events demonstration, it is 

insufficient in and of itself to allow for 

the exclusion of data. In order for EPA 

to concur on an exceptional events flag, 

States, Tribes, and local agencies must 

meet the additional requirements 

described below. As explained, the 

State, Tribe, or local agency has the 

responsibility to document the 

occurrence of the event in question, to 

demonstrate that the event qualifies as 

an exceptional event in accordance with 

section IV.D, is consistent with EPA 

policies and guidance for certain events 

as described in section IV.E, has 

provided for public review in 

accordance with section V.G, and to 

document the causal connection 

between the measurement under 

consideration and the event that is 

claimed to have affected the air quality 

in the area. The State, Tribe, or local 

agency must also demonstrate that the 

event is associated with an unusual 

measured concentration beyond typical 

fluctuations including background, and 

that there would have been no 

exceedance or violation ‘‘but for’’ the 

event. Because the initial step of 


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flagging the data is a relatively simple 

one, States, Tribes, and local agencies 

may flag more days than the number of 

days for which they ultimately intend to 

submit demonstrations to justify data 

exclusion. 

3. Comments and Responses 

Comment: One commenter supported 

flagging data related to any fire that 

caused an exceedance. 

Response: This Rule does not 

preclude a State, Tribe, or Local agency 

from flagging any data allegedly 

influenced by exceptional events. 

However, for the data to qualify as an 

exceptional event and to exclude it from 

regulatory decisions, the data must meet 

all of the criteria described in this Rule 

and all the procedures delineated must 

be followed. 

B. What Does It Mean for an Event To 

‘‘Affect Air Quality’’? 

1. Background 

It is important to recognize that any 

emissions-producing event has the 

potential to have some influence on 

downwind air quality. Indeed, on any 

given day, measured air quality at any 

given location will reflect the influences 

of a variety of activities, including both 

natural and anthropogenic emissions 

from both local as well as remote 

upwind sources. Given the directive in 

section 319(b)(3)(B)(ii), that a clear 

causal connection must exist between 

the ‘‘measured exceedances’’ and the 

exceptional event, EPA believes that it 

would be unreasonable to exclude data 

affected by an exceptional event simply 

because of a trivial contribution of an 

event to air quality. Furthermore, we 

believe that it would be unreasonable to 

exclude more significant, but routine 

background air quality impacts, as this 

would disregard an important part of 

the public’s exposure to air pollution 

upon which EPA’s air quality standards 

are based. The effect of such exclusion 

would be an inappropriate reduction in 

the stringency of the NAAQS, rather 

than providing specific relief under the 

circumstances provided in section 319 

for which States should not be 

designated nonattainment or be required 

to prepare costly SIP control strategies. 

Neither section 319, nor its legislative 

history, provides precise guidance on 

what should be considered when 

determining whether an event ‘‘affects 

air quality’’ and thus qualifies to be 

considered for exclusion or special 

treatment. However, section 

319(b)(3)(B)(ii) and (iv) provides that 

there must be a ‘‘clear causal 

relationship’’ between a measured 

exceedance of a standard and the event 

to show that the event ‘‘caused a 

specific air pollution concentration;’’

and it must be shown that the data in 

question are ‘‘directly due’’ to an 

exceptional event. Moreover, one of the 

principles provided by section 

319(b)(3)(A) indicates that the 

protection of public health is the highest 

priority. For these reasons, we proposed 

three conditions under which an event 

may qualify as ‘‘exceptional’’ for 

purposes of special regulatory 

consideration: Its air quality impact 

must (1) fall both above the level of the 

applicable standard (i.e., must be an 

‘‘exceedance’’ as required by section 

319), (2) be significantly beyond the 

normal fluctuating range of air quality, 

including background air quality 

concentrations, and (3) should be large 

enough such that without it there would 

have been no exceedance. 

We next provided several alternative 

approaches to determining whether and 

when air quality is ‘‘affected by’’

exceptional events and requested 

comment on which of these approaches 

was most suitable for demonstrating 

such impacts. These approaches 

primarily applied to condition (2) 

above. Two of the approaches involved 

statistical comparisons of existing 

flagged data. The final rule most closely 

reflects the third proposed option with 

some modifications. This option 

considered a case-by-case evaluation of 

the data against historical, seasonally 

adjusted air quality levels. Finally, the 

proposed rule provided details 

regarding what is meant by an 

exceedance (1) and the ‘‘but-for’’

condition (3). These are discussed in 

detail in section V.C. 

2. Final Rule 

Under the Final Rule, the 

demonstration to justify data exclusion 

must provide a justification that: (a) The 

event qualifies in accordance with 

section IV.D. and if applicable, with 

EPA policies and guidance for certain 

events as described in section IV.E, (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 an unusual measured 

concentration beyond typical 

fluctuations including background, and 

(d) there would have been no 

exceedance or violation but for the 

event (discussed in section V.C). The 

second and third criteria establish that 

the event affected air quality. 

The second criterion that the event 

caused an air quality impact may be 

shown through a number of methods 

including, but not limited to, modeling 

and speciation analysis. The third 

criterion distinguishes common events 

from those that are exceptional and may 

be accomplished through the 

presentation of historical evidence. 

The final rule permits a case-by-case 

evaluation, without prescribed 

threshold criteria, to demonstrate that 

an event affected air quality. This 

demonstration would be based on the 

weight of available evidence, but must 

consider the historical frequency of 

such measured concentrations. While a 

State may determine the specific 

approach to use for such analysis, it 

must compare contemporary 

concentrations with the distribution of 

all measured data during the past 

several years. The evidence that an 

event affected air quality may be 

presented on a seasonal or other 

temporal basis to best compare 

contemporary concentrations with the 

distribution of historical values. For 

consistency with data reporting and 

computation of NAAQS statistics, a 

calendar quarter basis is suggested. 

Baseline data may also be defined 

differently for each event type (e.g., 

April and May data may be the most 

relevant information for statistical 

comparison with certain dust events). 

The general statistical approach of 

using all measured data during the past 

several years is independent of 

historical flagging practices and allows 

States to accurately represent events not 

likely to recur by including all 

monitoring data in analyses. 

In addition, the magnitude of the 

measured concentration on days 

affected by exceptional events relative 

to historical, temporally adjusted air 

quality levels can guide the level of 

necessary analysis and documentation 

to demonstrate that the event affected 

air quality. For extremely high 

concentrations relative to historical 

values (e.g., concentrations greater than 

the 95th percentile), a lesser amount of 

documentation or evidence may be 

required to demonstrate that the event 

affected air quality. The closer the event 

concentration is to typical levels (e.g., 

values less than the historical 75th 

percentile), the stronger the necessary 

evidence would have to be to justify 

exclusion of data for regulatory 

purposes. This weight of evidence 

approach is most nearly analogous to 

our historical treatment of exceptional 

events. 

3. Comments and Responses 

Comment: One commenter noted that 

EPA’s proposed rule concedes that the 

third option would ‘‘provide the least 

definitive guidance to assist States in 

their evaluations,’’ and ‘‘may make it 


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difficult for EPA regions to be consistent 

when determining whether to concur on 

a flag.’’ Moreover, ‘‘the case-by-case 

approach allows for consideration of 

days with ambient concentrations 

which are not necessarily among the 

highest concentrations that have been 

historically observed. While such days 

are unlikely to impact short-term 

standards, discounting such days can 

certainly have an impact on an annual 

average concentration.’’ The commenter 

asserted that EPA’s description of the 

proposed case-by-case evaluation makes 

the case for rejecting that option because 

it fails to provide the guidance 

mandated by section 319, and is so 

vague as to be arbitrary. 

Response: The EPA disagrees with the 

commenter that this option fails to 

provide guidance and is so vague as to 

be arbitrary. The EPA has explained 

above the criteria that it will use in 

making its case-by-case evaluations. The 

commenter’s concern that the event 

must represent concentrations that are 

not typically observed is addressed by 

the third criterion that the event must be 

associated with an unusual measured 

concentration beyond typical 

fluctuations including background. 

Demonstration of the magnitude of the 

measured concentrations with respect to 

historical frequency under similar 

conditions will provide a new level of 

consistency across monitoring locations. 

Comment: If an area exceeds the 

NAAQS, one commenter stated that use 

of a 95th percentile criterion better 

ensures that the definition of an 

exceptional event is met (i.e., unlikely 

to recur at a particular location). 

Response: The EPA recognizes that 

extreme concentrations (e.g., 

corresponding to values greater than the 

95th percentile of historical values) are 

more likely associated with exceptional 

events. With the final rule, we are not 

assuming that such values are definitely 

exceptional. In fact, some extreme 

concentrations may be associated with 

various emission sources and 

atmospheric conditions which are 

unrelated to a causal connection to the 

claimed exceptional event. Instead, the 

frequency of occurrence relative to 

historical concentrations would be used 

as an important part of the overall 

weight of evidence to demonstrate the 

exceptional nature of the claimed air 

quality impact. 

C. Use of a ‘‘But For’’ Test 

1. Background 

There may be instances in which 

exceptional events may have a 

significant impact on air quality on days 

when concentrations are already above 

the applicable standard in the absence 

of the influence of such events. In such 

cases, it is important to preserve and 

consider all valid air quality data 

influenced by such activities, which 

properly fall within the responsibilities 

of States to manage for purposes of air 

quality attainment and maintenance. 

For this reason, we proposed to require 

that air quality data may not be 

excluded except where States show that 

exceedances or violations of applicable 

standards would not have occurred ‘‘but 

for’’ the influence of exceptional events. 

In other words, to the extent that it is 

possible to determine that the resulting 

air quality concentrations and 

appropriate design values for an area 

would be above the level of the 

standards even without the influence of 

the exceptional event, the air quality 

data for the day(s) in question should 

not be excluded. However, 

consideration of the impacts of 

exceptional events on air quality values 

for control strategy planning purposes 

may be appropriate, and States are 

encouraged to consult with the 

appropriate EPA regional office to 

further discuss this issue. 

2. Final Rule 

The EPA will maintain the proposed 

‘‘but-for’’ requirement that air quality 

data may not be excluded except where 

States, Tribes, or local agencies show 

that exceedances or violations of 

applicable standards would not have 

occurred ‘‘but for’’ the influence of 

exceptional events. Through analyses, it 

is possible to demonstrate that an 

exceedance or violation would not have 

occurred but for the event [See sample 

‘‘but-for’’ analysis in memo to docket, 

Husar et al. 2006 (http:// 

www.regulations.gov, EPA–HQ–OAR–

2003–0061–0733 thru 0733.5)]. This 

analysis does not require a precise 

estimate of the estimated air quality 

impact from the event. The weight of 

evidence demonstration can present a 

range of possible concentrations which 

is not as technically demanding as 

justifying a specific adjustment to a 

measured value. 

Because there are two standards for 

PM2.5, clarification is needed regarding 

the measurements that contributed to an 

exceedance or a violation that are 

eligible to be excluded. This rule is 

limited to values above the annual 

standard for PM2.5 because this 

simplifies the process for determining 

which values are eligible for flagging 

according to the intent of section 319. 

The short-term PM2.5 NAAQS is based 

on a 3-year average of the annual 98th 

percentile of 24-hour values. Therefore, 

it is possible that one or two of these 

annual concentration values may be 

below the level of the NAAQS while the 

3-year average is above the level of the 

NAAQS. Because three annual 98th 

percentile concentration values are 

included in the determination of a 

short-term PM2.5 NAAQS violation, 

individual measurements below the 

NAAQS may contribute to a violation. 

On the other hand, the annual PM2.5

NAAQS is also a standard based on a 3- 

year average. However, violations of the 

annual standard that are caused by 

measurements which are not 

exceedances of that standard will be 

difficult to distinguish from typical air 

quality concentrations including 

background. To accommodate the 3-year 

form of the PM2.5 NAAQS, this rule will 

allow measurements whose 

concentrations are greater than the level 

of the annual NAAQS to be flagged as 

being affected by exceptional events for 

the purposes of contributing to an 

exceedance or violation of the PM2.5

NAAQS. Thus, we provide the 

following clarification that individual 

measured values greater than the annual 

PM2.5 NAAQS will be considered 

‘‘exceedances’’ under this rule and 

therefore eligible to be considered for 

exclusion for comparisons to either the 

annual or 24-hour NAAQS. 

3. Comments and Responses 

Comment: One commenter stated that, 

while some of those measurements may 

not individually be above the NAAQS, 

taken together they might be sufficient 

to put an area in violation of an annual 

standard. Any ‘‘but for’’ determination 

must take into account the aggregate of 

exceptional events that occurred within 

the applicable NAAQS period. 

Response: The rule acknowledges that 

it is possible that an event can affect 

multiple days. The ‘‘but for’’ provision 

allows for data exclusion if but for the 

entire event there would have been no 

exceedance or violation. Therefore, for 

those events that can be shown to affect 

air quality on multiple consecutive 

days, measurements for the entire 

period are eligible for data exclusion, 

provided that at least one measurement 

day during the episode is an exceedance 

as defined by this rule and the air 

quality impact on each day are 

considered exceptional. 

Comment: One commenter cautioned 

EPA about using the phrase ‘‘to the 

extent it is possible to determine’’

because a ‘‘bright line’’ distinction 

between the contribution from natural 

and anthropogenic sources often does 

not exist. 

Response: We agree with this 

comment and for this reason we will 

permit a weight of evidence-based 


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approach to demonstrate that there 

would not have been an exceedance or 

violation but for the event. 

D. Schedules and Procedures for 

Flagging and Requesting Exclusion of 

Data 

1. Background 

In establishing procedures and time 

tables for States to request, and EPA to 

grant, exclusion of data affected by 

exceptional events, we are guided by 

two competing considerations: Ensuring 

States have adequate time and 

opportunity to compile and evaluate all 

relevant and available information in 

support of such requests; and making 

determinations in a timely manner so 

that all pertinent and valid air quality 

data would be appropriately considered 

in regulatory determinations. To assist 

EPA in determining the best approach to 

managing the data flagging process and 

submissions of demonstrations for the 

final rule, we proposed three 

alternatives for public review and 

comment. Public comments showed that 

each option had desirable aspects, and 

these are incorporated into the final 

rule. 

2. Final Rule 

A multi-step process will be 

established for identification of data and 

submission of demonstrations. The 

process is designed to ensure that 

States, Tribes, and local agencies have 

adequate opportunity to compile and 

present evidence of exceptional and 

natural events but also ensures timely 

submittals in order to make regulatory 

decisions and ensure the protection of 

human health through NAAQS 

determinations. The steps include State 

flagging, annual State submission of an 

initial event description, State 

submission of a demonstration to justify 

data exclusion and EPA review followed 

by approval or disapproval. Where air 

quality in an area is influenced by a 

relatively small set of emission sources 

with well-defined emission profiles and 

limited pollutant species, a 

demonstration that an air quality 

measurement influenced by a particular 

event merits exclusion may be relatively 

simple to make. In other cases, such as 

where the number and types of sources 

contributing to measured air quality 

concentrations are extremely complex 

and varied, making it more difficult to 

distinguish between the effects of 

routine activities and unusual ones, 

more time and effort will be needed for 

a State, Tribe, or local agency to provide 

an adequate demonstration in support of 

its request. 

States, Tribes, and local agencies are 

encouraged to flag the data that they 

believe to be affected by exceptional 

events at the time of submission of the 

air quality data to EPA’s AQS database, 

in accordance with the schedule 

described in 40 CFR 58.16, which is 

generally no later than 90 days after the 

end of the calendar quarter. This 

includes both flagging of data and 

insertion of the initial event description 

into the AQS comment field. This 

constitutes notification of the 

appropriate EPA Regional Office 

concerning the State’s intention to seek 

exclusion of data. This approach would 

ensure that the flagging process remains 

consistent with the timeline set forth in 

rules governing data submission 

requirements. The EPA recognizes that 

laboratory analyses may delay these 

submissions and therefore is extending 

the required time period for submission 

to 180 days after the end of the calendar 

year (i.e., all flags, along with initial 

event descriptions, for a calendar year 

must be reported by July 1 of the 

following year). 

We encourage States, Tribes, and local 

agencies to submit the demonstration to 

justify data exclusion annually for 

exceedances of short-term NAAQS by 

July 1. However, the demonstration to 

justify data exclusion must also be 

submitted no later than 12 months prior 

to a regulatory decision. For all flagged 

events, the demonstration to justify data 

exclusion must be submitted within 3 

years of the calendar quarter following 

an event, but no later than 12 months 

prior to a regulatory decision. This 

period should be used primarily to 

support NAAQS compliance with 

annual averages and violations of the 

short-term standard that were not 

anticipated. For nonattainment 

designations, this would occur with the 

Governor’s letter recommending the list 

of nonattainment areas. We also 

recognize that special circumstances 

could dictate more expedited data 

delivery, flagging, and minimal 

demonstrations (e.g., PM2.5 designations 

using 2002–2004 data). The submitted 

demonstration to justify data exclusion 

as well as the EPA responses and the 

rationale for the EPA decision will be 

made publicly available through EPA. 

The reason for providing the 3-year 

timeframe is that for ozone and PM, 

decisions regarding whether or not an 

area is attaining the applicable standard 

are based on the most recent 3 years of 

air quality data. Providing 3 years for 

submission of demonstrations would 

provide States, Tribes, and local 

agencies with an opportunity to 

evaluate whether the influence of one or 

more exceptional events will be relevant 

to determinations of attainment or 

nonattainment before undertaking the 

effort of preparing and submitting 

demonstrations. 

Once EPA receives a State’s 

demonstration, EPA generally will 

undertake to review the demonstration 

and provide a concurrence or 

nonconcurrence on the flag in the AQS 

database within 60 days. The EPA 

expects that, in most cases, this time 

period should be enough time to review 

and provide a concurrence or nonconcurrence related to a State’s request 

to exclude data affected by an 

exceptional event. However, for more 

complex demonstrations, EPA may 

require additional time to make its 

decision and will notify the State of the 

additional time required. 

3. Comments and Responses 

Comment: One commenter supported 

arguments on why the proposed rule 

must include a procedure for 

retrospective flagging that addresses the 

full set of the State’s needs so that the 

end result is that the State can flag any 

and all events impacted by natural 

events. 

Response: With the Final Rule, EPA 

requires annual submittal of flags. States 

may, if they so choose, submit them 

sooner. This schedule ensures that data 

are collected and retained shortly after 

the event and identification of potential 

(non-routine) events is done in a timely 

fashion to ensure that appropriate 

corrective actions can be taken. States 

would only maintain minimal 

documentation supporting the decision 

to flag the data. The full demonstrations, 

however, can come later, in order to 

allow States time to focus efforts on 

those events that are determined to have 

an impact on attainment. The Agency 

notes that the Exceptional Events Rule 

does not apply to routine natural events 

that are part of background air quality. 

Comment: One commenter was 

concerned that a State may have failed 

to flag data impacted by a natural event 

because the data values were below the 

current NAAQS, only to find the State 

threatened with nonattainment after 

NAAQS revisions. 

Response: For data collected before 

the effective date of this rule, States may 

include a demonstration to justify data 

exclusion with the Governor’s 

recommendation letter on 

nonattainment areas, provided that 

there was notice and opportunity for 

public comment. After considering this 

and other comments, for PM2.5 data 

collected during calendar years 2004–

2006, that the State identifies as 

resulting from an exceptional event, 


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EPA is permitting the State to flag and 

submit an initial description of the 

event provided that these are submitted 

no later than October 1, 2007. In cases 

where the State is able to show that this 

time period is inadequate, a State may 

submit a request for an extension and 

EPA will grant this request for an 

extension up to but no later than 

December 1, 2007. This procedure 

should accommodate States concerned 

about potential PM2.5 nonattainment 

areas using the 2004–2006 data sets. The 

EPA may consider a similar exemption 

of the schedules for submittal of data for 

future revision of standards. 

Comment: One commenter stated that 

EPA should also make allowances for 

those situations when a State neglects to 

flag a value or submit documentation 

within the required timeframes. In these 

cases, the commenter asserted that EPA 

should provide some type of petitioning 

process. 

Response: If a State fails to meet the 

schedule for flagging or document 

submittal, late petitions will not be 

considered. Policy decisions, SIP 

planning, and dissemination of data 

should not be delayed or altered based 

on a State’s failure to submit 

documentation or follow the regulatory 

procedures in a timely manner. 

E. Exclusion of Entire 24-Hour Value as 

Opposed to a Partial Adjustment of the 

24-Hour Value 

1. Background 

In general, EPA’s historical practice 

has been to exclude a daily measured 

value in its entirety when an 

exceptional event causes that value, and 

we retained this approach in the 

proposed rule. With this approach, a 

determination is made that emissions 

from the event are largely responsible 

for the resultant ambient air pollutant 

concentration. For example, if the 

observed concentration is 200 μg/m3 for 

PM2.5 and is associated with a nearby 

forest fire, then EPA is likely to concur 

with the claim that the event was 

responsible for the ambient 

concentration. The measured value 

would be excluded in its entirety from 

the data used to judge attainment (as per 

40 CFR 50, appendix N), although the 

measurement would still count towards 

meeting minimum data capture 

requirements. 

We believe it would be desirable to 

adjust the daily value to exclude only 

those portions of the data that are 

attributable to the exceptional event in 

question, and to retain the remainder of 

the day’s measurement if appropriate 

and accurate methods were available to 

make such adjustments. For example, if 

an area affected by a wildfire had a 

measured 24-hour PM2.5 concentration 

of 50 μg/m3 and the estimated event 

impact was 30 μg/m3, then the expected 

value that would have occurred but for 

the event would have been 20 μg/m3. 

Normal air quality for this location 

might be 16 μg/m3 and, therefore, the 

‘‘but-for’’ concentration of 20 μg/m3 is 

above average. Discounting the entire 

event day could, therefore, 

inappropriately bias a determination of 

nonattainment with the annual PM2.5

NAAQS (currently set at 15 μg/m3). We 

are currently seeking to develop and 

evaluate new analytical methods that 

would allow us to discount only the 

portion of the daily value attributable to 

the exceptional event. However, at 

present, we are not aware of the 

existence of precise and universally 

applicable techniques that are 

administratively and technically 

feasible and that could support partial 

adjustment of air quality data except 

perhaps in limited cases, such as where 

the number and type of pollutant 

species and contributing sources are 

relatively less complex or potentially 

when sufficient spatial, temporal, 

meteorological and chemical data are 

available [See memo to docket, Husar et 

al. 2006, (http://www.regulations.gov, 

EPA–HQ–OAR–2003–0061–0733 thru 

0733.5)]. When we determine that 

techniques for adjustment of air quality 

data are sufficiently well-demonstrated 

for use in exceptional events 

determinations, we will publish a notice 

of proposed rulemaking to seek 

comment on the appropriateness and 

scope of such use and its impact on the 

requirements set forth in this rule for 

determining an exceptional event. 

2. Final Rule 

We are retaining in this rule EPA’s 

historical practice to exclude a daily 

measured value in its entirety when that 

value is found to be caused by a 

qualifying exceptional event that 

affected air quality in accordance with 

the conditions described in sections V.B 

and V.D. If precise and universally 

applicable techniques that are 

administratively and technically 

feasible and that could support partial 

adjustment of air quality data become 

available in the future, EPA will, 

through a rulemaking, propose, and as 

appropriate, finalize a technique for 

partial adjustment of data as well as any 

other matters in this rule which may be 

affected by the availability of this 

technology. 

One exception may be made to this 

exclusion of the entire daily value for 

monitoring locations with hourly 

measurements by Federal Reference 

Methods (FRM), Federal Equivalent 

Methods (FEM), and/or Approved 

Regional Methods (ARM) where such 

data are submitted routinely to AQS. 

For example, in cases where 

stratospheric ozone intrusion occurs, 

those hourly (but not sub-hourly) 

measurements affected by the intrusion 

may be excluded in order to calculate 

the ozone measurements for the day. 

The individual hours are to be excluded 

however, if the resulting calculated 

NAAQS averaging time value exceeds 

the level of the standard, not just if the 

individual hourly values exceed that 

level. Thus, in the case of ozone, the 

resulting 8-hour average must exceed 

0.08 ppm, and the resulting 24-hour 

average must exceed 15.0 μg/m3 for 

PM2.5. Incomplete data substitution 

protocols shall also be considered when 

evaluating the original and revised 

NAAQS averaging time value. In other 

words, an 8-hour ozone period is 

considered valid when fewer than six 

valid hours are present if one half the 

minimum detection limit can be 

substituted for the missing hours and 

the resultant 8-hour value still exceeds 

0.08 ppm; a daily (24-hour) PM2.5 value 

is considered valid when fewer than 

eighteen valid hours are present if 

zeroes can be substituted for the missing 

hours and the resultant 24-hour value 

still exceeds 15.0 μg/m3. 

3. Comments and Responses 

Comment: One commenter supported 

value adjustment rather than exclusion 

when, and only when, such adjustment 

can be accomplished by the application 

of various quantitative or semiquantitative approaches. When this is 

not possible, the value in question 

should be replaced with a long-term 

seasonal mean value. 

Response: The EPA will consider 

such analyses as part of the weight of 

evidence to judge ‘‘but-for,’’ but will not 

make quantitative adjustments to 

reported measured values because EPA 

does not believe sufficient quantitative 

methods are available at this time. 

F. What Should States Be Required To 

Submit in Their Exceptional Events 

Demonstrations? 

1. Background 

Section 319 requires that, in order to 

have a flagged value excluded from 

regulatory determinations, a State must 

make an affirmative demonstration that 

an event occurred (as shown by reliable 

and accurate data that is promptly 

produced) and that there is a clear 

causal relationship between measured 

exceedances or violations of a standard 

and the exceptional event in question to 


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‘‘demonstrate that the exceptional event 

caused a specific air pollution 

concentration’’ (42 U.S.C. 

7619(b)(3)(B)(ii), (iv)). Section 319 also 

indicates that regulations promulgated 

under the section should provide for 

criteria and procedures to exclude air 

quality monitoring data ‘‘directly due to 

exceptional events from use in 

determinations by the Administrator 

with respect to exceedances or 

violations of the national ambient air 

quality standards.’’

Therefore, after flagging data in the 

AQS database, States are expected to 

develop appropriate documentation to 

support each individual flag. As a 

general matter, we believe that such 

demonstrations should include 

documentation showing that the event 

in fact occurred and that emissions 

related to the event were transported in 

the direction of the monitor(s) where 

measurements were recorded; the size of 

the area affected by the transported 

emissions; the relationship in time 

between the event, transport of 

emissions, and recorded concentrations; 

and, as appropriate, pollutant speciesspecific information supporting a causal 

relationship between the event and the 

measured concentration. The latter 

information could be based on available 

data provided by routine speciation, 

monitoring networks, or from selective 

laboratory analysis of archived 

particulate matter filters for the day 

thought to be impacted by specific 

events. In certain situations, such data 

might be useful for evaluation of 

impacts from exceptional events, e.g., to 

distinguish between impacts caused by 

natural fires versus impacts caused by 

industrial sources. States also need to 

show that appropriate mitigation actions 

were taken at the time that the event 

occurred, or after an event occurred in 

order to protect public health. 

The following examples are intended 

to further illustrate the kinds of 

information that States could consider 

in preparing their demonstrations: 

• Information demonstrating the 

occurrence of the event and its 

subsequent transport to the affected 

monitors. This could include, for 

instance, documentation from land 

owners/managers, satellite-derived 

pixels (portions of digital images) 

indicating the presence of fires; satellite 

images of the dispersing smoke and 

smoke plume transport or trajectory 

calculations (calculations to determine 

the direction of transport of pollutant 

emissions from their point of origin) 

connecting fires with the receptors. 

• Identification of the spatial pattern 

of the affected area (the size, shape, and 

area of geographic coverage). This could 

include, for instance, the use of satellite 

or surface measurement data. 

• Information about temporal patterns 

(e.g., the time and duration of an event 

in relation to measured downwind 

concentrations, air quality trends over 

time and space). This could include, for 

instance, observed sequential 

concentration spikes at multiple 

locations in a downwind direction. 

• Identification of the chemical 

composition of measured 

concentrations. This could include, for 

instance, organic or crustal material in 

excess of typically observed quantities 

to differentiate from other high 

concentration events. 

• High wind speeds relative to 

historically typical levels for the season 

of the year in which the claimed event 

occurred. 

This list is not exhaustive and not all 

of these kinds of information and/or 

documentation will need to be provided 

in every instance. A particular instance 

may require more or less 

documentation, depending on the 

particular facts or circumstances in that 

instance. The simplest demonstrations 

could consist of newspaper accounts or 

satellite images to demonstrate that an 

event occurred together with daily and 

seasonal average ambient concentrations 

to demonstrate an unusually high 

ambient concentration level, which is 

clearly indicative of an exceptional 

impact. Such is the case with events 

such as volcanic eruptions and nearby 

forest fires. In one instance, we 

determined that wildfires upwind of the 

San Diego area very likely caused high 

concentrations of particulate matter 

measured in October 2003 based on the 

actual physical damage caused by fire to 

the ambient monitor. Depending on the 

nature of the event, meteorological 

conditions, severity and spatial extent of 

measured ambient concentrations 

(including relevant chemical 

components when available) relative to 

what typically occurs in the area, and 

on emissions of pollutants from the 

exceptional event which have similar 

characteristics to those of other sources 

in the area, additional showings could 

be required on a case-by-case basis. In 

particular, we anticipate that 

significantly more effort will be needed 

to establish that an exceptional event 

caused a particular concentration in an 

urban area in which there are numerous 

and diverse sources and complex 

meteorology and topography, and where 

the emissions from the event in question 

may well be similar to those from other 

sources contributing to measured 

concentrations, as compared to an area 

that has relatively few sources, simple 

terrain and less complex meteorology, 

and where emissions associated with 

the event are both substantially greater 

than and different in composition from 

those of other nearby sources. 

2. Final Rule 

The demonstration to justify data 

exclusion will address specific monitor 

readings reported to the AQS database. 

As stated in the previous sections, a 

complete demonstration shall justify 

that: (a) The event qualifies in 

accordance with section IV.D. and with 

EPA policies and guidance for certain 

events as described in section IV.E, (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 an unusual measured 

concentration beyond typical 

fluctuations including background, (d) 

there would have been no exceedance or 

violation but for the event, and (e) the 

State has provided an opportunity for 

the public to comment as required 

under section V.G. The level of 

documentation may vary by the type of 

event and can be guided in part by the 

relative magnitude of the observed 

concentrations. To obtain concurrence, 

EPA must determine that the 

demonstration is complete and provides 

a reasonable technical demonstration. 

Because of the variability in the 

nature of exceptional events and the 

resulting demonstration requirements, 

States should consult with the 

appropriate EPA Regional Office early 

in the process of preparing their 

demonstrations. We are not specifying 

what will be required as a minimum 

level of documentation in all cases 

because facts and circumstances will 

vary significantly based on, among other 

things, geography, meteorology and the 

relative complexity of source 

contributions to measured 

concentrations in any particular 

location. We believe, however, that at a 

minimum, the elements of such a 

demonstration should include a 

showing that an event occurred at a time 

when meteorological conditions were 

conducive to transporting emissions 

from the event downwind to the 

monitor recording a high concentration 

of one or more criteria pollutants. 

Acceptable documentation will be 

determined through consultation with 

the EPA regional offices. However, 

certain minimum requirements (e.g., 

‘‘but for’’ test) will be necessary as 

discussed in the earlier sections of this 

rule. 


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3. Comments and Responses 

Comment: In cases where high wind 

data cannot be found, one commenter 

stated that EPA should use a ‘‘weight of 

evidence’’ approach, and should 

recognize that not accepting a 

demonstration that such exceedances 

are exceptional events is equivalent to a 

determination that the exceedances 

were caused by recurring anthropogenic 

sources. 

Response: The EPA agrees that a 

weight of evidence approach is the most 

appropriate for demonstrations of 

exceptional impact. 

Comment: One commenter asserted 

that States should be allowed to choose 

not to submit any demonstration, if the 

flagged value does not impact a 

regulatory determination or if more 

detailed investigation indicates that the 

value may not have been caused by an 

exceptional event after all. In these 

cases, the agency should have the 

option to remove the flag. 

Response: We agree that the flag can 

be removed in these circumstances or 

left for informational purposes only. 

Comment: One commenter stated that 

EPA must provide a reasonable 

explanation and documentation for their 

decision to deny any request for the 

flagging of data. 

Response: The EPA regional offices 

will work with the States, Tribes, and 

local agencies to ensure that proper 

documentation is submitted to justify 

data exclusion. The EPA will make the 

response and associated explanation 

publicly available. 

Comment: One commenter stated that 

EPA must establish a technically-based 

appellate process for States to follow 

when Regional Offices do not concur 

with a data flag. 

Response: The EPA does not believe 

that an appellate process is necessary 

because we anticipate that the States 

and Regional Offices will be working 

closely through the data and 

documentation submission process. 

G. Public Availability of Air Quality 

Data and Demonstrations Related to 

Exceptional Events 

1. Background 

Section 40 CFR part 58.16 of EPA’s air 

quality monitoring rules state that all 

ambient air quality data and associated 

quality assurance data, including 

metadata records and information 

specified by the AQS Data Coding 

Manual epa.gov/ttn/airs/airsaqs/ 

manuals/manuals.htm must be reported 

to EPA via AQS. This information 

includes exceptional event flags. 

2. Final Rule 

We are requiring that all relevant 

flagged data, along with the reasons for 

the data being flagged, and a 

demonstration that the flagged data are 

caused by exceptional events be made 

available by the State for 30 days of 

public review and comment. The State 

or designated local agency should 

consider the public comments prior to 

the final demonstration being submitted 

to EPA for a decision concerning 

whether to exclude the data from 

regulatory consideration. Notice and 

availability of such data and 

demonstrations must be adequate and 

consistent with States’ administrative 

procedures governing similar 

submissions. The EPA does not require 

that public hearings be held on 

exceptional events demonstrations but 

leaves this matter to the States’

discretion consistent with their 

administrative procedures. With the 

submission of the demonstration, the 

State should document that the public 

comment process was followed. 

3. Comments and Responses 

Comment: One commenter stated that 

any new rules related to the flagging of 

exceptional events should be consistent 

with prior EPA policies and provide 

sufficient time for States to engage the 

public in the process prior to data being 

flagged in the AQS. 

Response: The EPA believes that the 

data demonstration requirements of the 

final rule provide sufficient time to 

engage the public. Not only does the 

final rule require that the public be 

accorded an opportunity to comment on 

the State’s findings, but in some 

instances there will be further 

opportunities for public review and 

comment at the time that EPA proposes 

to base specific actions, e.g., approval or 

disapproval of SIP revisions. Thus, we 

do not believe that additional public 

review and comment provisions are 

necessary or appropriate. 

VI. Additional Requirements 

Pursuant to section 319, EPA is 

finalizing this rule to address data that 

has been influenced by exceptional 

events. Also, EPA is finalizing one of 

four options put forth in the proposed 

rule to address the issue of whether, and 

to what extent, States are required to 

adopt specific mitigation plans or 

measures to protect the public from 

emissions due to exceptional events. 

Section 319 states that in promulgating 

regulations under the section, EPA shall 

follow certain, enumerated principles 

and that regulations must contain 

certain requirements. Section 

319(b)(3)(A) contains five principles, 

including the principle that each State 

‘‘must take necessary measures to 

safeguard public health regardless of the 

source of air pollution.’’ In order to 

address this principle, EPA is finalizing 

its proposal to exclude trivial and more 

routine air quality impacts from 

qualifying as an exceptional event and 

is also finalizing a ‘‘but for’’ test as a 

precondition to qualification as an 

exceptional event (See: section V.C 

above). 

A. Requirements for States To Provide 

Public Notification, Public Education, 

and Appropriate and Reasonable 

Measures To Protect Public Health 

1. Background 

The EPA proposed one approach and 

took comments on three alternative 

options concerning what actions a State 

should take in anticipation of, or in 

response to, the occurrence of an 

exceptional event. The options that 

were proposed ranged from being very 

detailed and prescriptive to being very 

flexible and less prescriptive in terms of 

the actions that States should take to 

mitigate the impact of an exceptional 

event on the public. While EPA does not 

believe that section 319(b)(3)(A) 

explicitly requires, in and of itself, that 

States must develop mitigating 

measures or plans, EPA solicited 

comment in the proposed rule on 

whether this subparagraph supports the 

use of other legal authority to require 

mitigating actions or plans when an 

exceptional event occurs, and solicited 

comment on issues regarding its legal 

authority to require mitigation measures 

and plans, and the legal basis for not 

requiring mitigation measures or plans. 

Option 1 in the proposed rule 

provided that in cases where 

exceedances of a NAAQS are caused by 

an exceptional event, once a State 

becomes aware that an exceptional 

event is occurring, is predicted to occur, 

or has occurred, the State must take 

reasonable and appropriate actions to: 

• Provide notice to the public of the 

event. This may include, but is not 

limited to, using the media to alert the 

public of the event. 

• Provide public education 

concerning the potential health risks 

associated with being exposed to high 

ambient concentrations of pollutant(s) 

related to the event. This may include, 

but is not limited to, providing 

information to sensitive populations 

related to the health risks associated 

with the event. 

• Take appropriate and reasonable 

measures to abate or minimize the 

exposure of the public to high 


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concentrations of air pollution 

associated with the exceptional event. 

This may include, but is not limited to, 

taking reasonable and appropriate 

actions to implement control measures 

on significant contributing 

anthropogenic sources to reduce 

potential exposure of the public to 

emissions associated with natural 

events. States must review the need to 

implement controls on contributing 

anthropogenic sources on a case-by-case 

basis. For example, in the case of 

volcanic or seismic activity, this may 

include, but is not limited to, providing 

for prompt clean-up of the ash deposits 

related to the event to prevent reentrainment. 

Under option 1, EPA also proposed 

that, where a State is requesting that air 

quality data be excluded as an 

exceptional event, the State must 

submit, as a part of its demonstration, 

appropriate documentation to show that 

the State provided public notice and 

public education concerning the event 

in question, and that the State took 

reasonable and appropriate measures to 

abate or minimize the exposure of the 

public to the emissions from the event, 

where appropriate. 

Option 2 in the proposed rule 

provided that, States are required to 

adopt a general mitigation plan to 

address exceptional events before the 

occurrence of an event as a part of the 

State’s SIP required under section 

110(a)(1) of the CAA. Section 110(a)(1) 

requires States to adopt and submit to 

EPA, within 3 years following the 

promulgation of a new or revised 

NAAQS, a plan which provides for the 

implementation, maintenance, and 

enforcement of the standard in each air 

quality region within the State. Under 

this option, States would be required to 

develop and adopt the general 

requirements and procedures necessary 

for the implementation of a mitigation 

plan to address exceptional events as a 

part of its section 110(a)(1) SIP to 

address a new or revised NAAQS. The 

general plan related to exceptional 

events would include provisions 

providing for public notice, public 

education related to an event, and 

provide a requirement for a State to take 

reasonable and appropriate measures to 

mitigate the public health impacts of an 

exceptional event. Under this option, in 

cases where control measures are 

required to address the impacts 

associated with an exceptional event, 

the State would be required to 

implement appropriate measures on an 

episodic basis, meaning in response to 

a specific event that affects the air 

quality of a particular area. 

Option 3 in the proposed rule 

required that, where appropriate, EPA 

would require a State to develop and 

implement a mitigation plan for an area 

following the occurrence of an 

exceptional event. This is in contrast to 

option 2 above, which would require 

each State to adopt a plan under section 

110(a)(1) of the CAA which would 

contain the general provisions of a 

mitigation plan in advance of the 

occurrence of any exceptional event. 

Under option 3, the mitigation plan 

would only be developed by the State 

following the occurrence of an 

exceptional event for which the State 

requested exclusion of the air quality 

data, and would not be submitted as a 

part of the SIP. The mitigation plan 

would be required to address the actions 

that would be taken by the State related 

to future similar events. The mitigation 

plan under this option would have the 

same provisions as required of plans 

developed under Option 2 above, 

including the requirements to notify the 

public that an event is expected to 

occur, or is occurring, or has occurred, 

to provide for public education related 

to the health effects associated with the 

event, and to identify the actions that 

would be taken by the State to mitigate 

the impact of any recurrence of the 

event on public health. 

Option 4 provided that EPA would 

not require a State to develop and 

implement a mitigation plan for 

exceptional events, or to take specific 

mitigation measures as described in 

options 1–3 in order for EPA to exclude 

data from regulatory consideration. This 

approach proposed to allow States to 

have the maximum degree of flexibility 

in determining what actions should be 

taken to mitigate the impacts of 

exceptional events, e.g., public 

notification, public education, efforts to 

reduce exposures, or other necessary 

measures to safeguard public health. 

Thus, under this proposed option States 

would not be obligated to take any 

particular actions to mitigate exposures 

such as those contained in Option 1, to 

develop and implement a formal 

mitigation plan as part of the SIP such 

as those contained in Option 2, or to 

develop a more formal plan with 

requirements not a part of the SIP such 

as those contained in Option 3. 

2. Final Rule 

The EPA is adopting a modified 

version of Option 1 from the proposed 

rule, as described above. This option 

does not require States to submit formal 

mitigation plans; however, States must 

provide public notice, public education, 

and must provide for implementation of 

reasonable measures to protect public 

health when an event occurs. 

3. Comments and Responses 

Comment: Several commenters 

supported option 1 because they stated 

that it provides more flexibility for 

States to determine the appropriate 

measures to be implemented related to 

the occurrence of an exceptional event. 

Other commenters supported option 1 

for well defined, well understood events 

that are non-recurring or unlikely to 

recur. The majority of the commenters 

who commented on option 2 strongly 

opposed that option. The commenters 

indicated that option 2 would waste 

scarce local resources in developing a 

mitigation plan. Other commenters 

stated that issues concerning 

exceptional events should be dealt with 

outside the SIP process and section 110 

of the CAA. With regard to Option 3, 

one commenter indicated that a 

preemptive plan similar to a Natural 

Events Action Plan (NEAP) (which 

includes Reasonably Available Control 

Measures (RACM)/Best Available 

Control Measures (BACM) is necessary 

to mitigate the poor air quality impacts 

associated with exceptional events. The 

commenter stated that BACM, not 

RACM, must be implemented on all 

contributing anthropogenic sources 

related to an exceptional event. Several 

commenters supported option 3 for 

addressing public health impacts related 

to recurring natural events. The 

commenters stated that mitigation plans 

should include BACM for contributing 

anthropogenic sources, not RACM. The 

majority of commenters who 

commented on option 4 stated that they 

supported the implementation of option 

4 because it allows States the most 

flexibility for developing and tailoring 

programs for public notification of 

exceptional events, the implementation 

of education programs on exceptional 

events, and implementation of 

reasonable measures to protect public 

health. 

Response: States have an inherent 

responsibility to protect its citizens and 

as such to provide appropriate and 

reasonable actions to mitigate the 

impact of exceptional events on the 

public health. This includes alerting the 

public when such events occur, 

providing public education concerning 

the health effects of such events, and 

implementing reasonable measures to 

mitigate the impact of such events on 

public health. Consistent with this 

inherent responsibility, it is EPA’s belief 

that States are in a better position to 

make decisions concerning what actions 

should be taken to protect the public 

when an exceptional event occurs. This 


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being the case, States should have the 

necessary flexibility to take appropriate 

actions when exceptional events occur. 

The EPA is adopting a modified version 

of its proposed preferred option 1, 

which requires States to provide public 

notification, public education, and 

provides that States should take 

‘‘reasonable and appropriate measures’’

to protect public health related to the 

occurrence of an event. Because States 

are inherently responsible for the public 

health of its citizens, and are capable of 

making the determinations of what 

actions should be taken to mitigate the 

impact of such events on the public 

when they occur. The EPA has modified 

option 1 from the proposed rule and 

will not be requiring States to submit 

documentation concerning the actions 

that it took to mitigate the impact of 

exceptional events, in order for EPA to 

exclude data from regulatory 

consideration. As proposed in option 1, 

States may still make determinations 

regarding reasonable measures in a 

particular instance, which may or may 

not include the implementation of 

control measures on contributing 

anthropogenic sources related to an 

event, and are not limited to any 

particular measure. Therefore, under 

this option the implementation of 

RACM or BACM is not required, but a 

State has the necessary flexibility to 

determine if, and what, controls should 

be implemented following an event, as 

well as the level of control that is 

required. The EPA believes that this 

modified option 1 provides suitable 

flexibility to allow States to take those 

actions that it deems necessary and 

appropriate to protect public health. 

While section 319, as revised by SAFE–

TEA–LU, does not specifically provide 

that States must implement mitigation 

plans, in developing the exceptional 

events rule, EPA is required to consider 

the enumerated principles including the 

principle that States must take 

necessary measures to protect public 

health regardless of the source of air 

pollution. Therefore, under the 

modified version of option 1 adopted in 

this final rule, States must take 

reasonable and appropriate actions to 

protect public health. 

Comment: Several commenters stated 

that the exceptional events rule should 

be consistent with the current 

requirements under existing policies 

with respect to the need for a NEAP to 

address recurring natural events such as 

high wind events. 

Response: The EPA believes that it is 

advantageous for States to keep NEAPs 

in place that are currently being 

implemented in order to address the 

public health impacts associated with 

recurring natural events such as high 

wind events. However, following the 

promulgation of this rule, States will no 

longer be required to keep NEAPs in 

place that were not approved as a part 

of a SIP for an area. Where a NEAP, as 

well as BACM, has been approved as a 

part of a nonattainment SIP for an area, 

the NEAP, as well as the associated 

BACM, must remain in place. States 

may, however, submit a request to EPA 

to remove the NEAP and BACM from 

the SIP. The request must contain an 

approvable demonstration, as required 

by section 110(l), which shows that the 

removal of the NEAP and BACM will 

not interfere with any applicable 

requirement concerning attainment or 

maintenance of the NAAQS for an area, 

reasonable further progress, or any other 

applicable requirement for the area. 

VII. Special Treatment of Certain 

Exceptional Events Under This Final 

Rule 

As stated in section IV.D above, this 

final rule applies to data affected by 

natural events (which are a subset of 

exceptional events) at air quality 

monitoring sites where it has been 

determined that concentrations due to 

these events have caused, or 

substantially contributed to, 

exceedances of the NAAQS in an 

affected area. This final rule applies to 

several types of natural events, 

including, but not limited to, volcanic 

and seismic activities, natural disasters, 

high wind events, certain fires, and 

stratospheric ozone intrusions. It also 

applies to transported pollution 

originating from national and 

international sources that otherwise 

meets the criteria and requirements for 

exceptional events. Some types of 

exceptional events have unusual 

characteristics that require special 

consideration in the context of this final 

rulemaking. We discuss each of these 

special issues, and the necessary 

accommodations, below. 

A. Volcanic and Seismic Activities 

1. Background 

Volcanic and seismic activities may 

affect air quality for an extended period 

of time after the initial occurrence of the 

event in question. Therefore, EPA 

believes that it is appropriate to 

consider an extended timeframe for 

flagging and exclusion of data 

associated with such events. 

Specifically, EPA believes that 

emissions attributed to anthropogenic 

activities associated with clean-up that 

re-entrain volcanic ash and dust from 

seismic activity during the first year (12 

months) following an event will be 

treated as due to the natural event. 

2. Final Rule 

The EPA is finalizing its proposal 

with regards to volcanic and seismic 

activities. The EPA will allow up to 12 

months for the clean-up of ash deposits 

due to volcanic/seismic events. During 

that time period, emissions of reentrained dust due to anthropogenic 

activities associated with cleanup may 

be treated as exceptional events. In 

cases where the damage caused by the 

event is so substantial that a 12-month 

period is inadequate to address the 

clean-up that is necessary, a State may 

submit a request for an extension of the 

12-month time period to EPA. As stated 

elsewhere in this rule, EPA will grant 

requests for extensions of the time 

period related to such events on a caseby-case basis. States are encouraged to 

submit supporting information 

concerning the reason for the extension 

and the length of time being requested 

for the extension. 

B. High Wind Events 

1. Background 

Where high wind events result in 

exceedances or violations of the 

particulate matter standards, EPA 

proposed that they be treated as natural 

events if there is a clear causal 

relationship demonstrated between the 

exceedances measured at the air quality 

monitoring site and the high wind event 

in question, and if anthropogenic 

activities which contribute to 

particulate matter emissions in 

conjunction with the high wind event 

are reasonably well-controlled. 

2. Final Rule 

The EPA’s final rule concerning high 

wind events states that ambient 

particulate matter concentrations due to 

dust being raised by unusually high 

winds will be treated as due to 

uncontrollable natural events where (1) 

the dust originated from 

nonanthropogenic sources, or (2) the 

dust originated from anthropogenic 

sources within the State, that are 

determined to have been reasonably 

well-controlled at the time that the 

event occurred, or from anthropogenic 

sources outside the State. These events 

are also discussed in section IV.E.5.c 

above. In cases where anthropogenic 

sources are determined to have 

contributed to exceedances or violations 

due to high wind events at air quality 

monitoring sites, per our decision in 

this rulemaking concerning the action 

that States must take to mitigate the 

impact of exceptional events on public 


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15Section 319(b)(1)(B) states: ‘‘In this subsection, 

the term ‘exceptional event’ does not include (i) 

stagnation of air masses or meteorological 

inversions; (ii) a meteorological events involving 

high temperatures or a lack of precipitation; or (iii) 

air pollution relating to source noncompliance.’’ In 

terms of the exclusion related to ‘‘a meteorological 

event involving high temperatures or a lack of 

precipitation’’ EPA believes that this statutory 

language prohibits EPA from treating a typical dry 

day(s) or a dry season for an area as an exceptional 

event. However, EPA believes that Congress did not 

intend that the above quoted language to prevent a 

State from submitting compelling documentation 

which shows that severe drought conditions may 

have contributed to an exceptional event, but 

instead was designed to prevent the indiscriminate 

exclusion of data on days characterized by ‘‘high 

temperature and a lack of precipitation.’’ Therefore, 

EPA is permitting States to submit documentation 

which shows that ‘‘severe drought’’ conditions may 

have contributed to the occurrence of a high wind 

event. The documentation must, however, be 

compelling enough to show that the conditions 

present at the time of the event were more 

substantial than a typical dry day(s) or dry season 

for the area in question, but were related to severe 

drought conditions. The EPA will review this 

information and make decisions concerning the 

exclusion of the data related to the event on a caseby-case basis. 

health (See section VI above), States 

must take reasonable and appropriate 

measures to mitigate the impact 

associated with the event on public 

health. As stated in section VI of this 

rule, States have the flexibility to 

implement reasonable measures to 

protect public health when an 

exceptional event occurs. These actions 

may or may not include the 

implementation of controls on 

contributing anthropogenic sources 

related to an event. However, where 

anthropogenic sources have contributed 

to the exceedances of the PM NAAQS at 

an air quality monitoring site due to a 

high wind event, a State must take 

reasonable and appropriate measures to 

protect public health. 

Since the conditions that cause or 

contribute to high wind events vary 

from area to area with soil type, 

precipitation, and the speed of wind 

gusts, States should provide appropriate 

documentation which indicates what 

types of circumstances contributed to 

the exceedances or violations at the 

monitoring site in question.15 In this 

rule, EPA is not identifying a specific 

wind speed which should be considered 

when making a determination 

concerning whether an event should 

qualify as exceptional. Instead, EPA is 

requiring that States submit appropriate 

documentation which demonstrates 

why a particular event should be 

considered exceptional for the affected 

area. The EPA will review the 

documentation submitted by States 

concerning high wind events and will 

make decisions concerning whether to 

exclude the data as being influenced by 

an exceptional event on a case-by-case 

basis. 

C. Stratospheric Ozone Intrusion 

1. Background 

Consideration of stratospheric ozone 

intrusions applies only to the 8-hour 

ozone standard. The occurrence of such 

intrusions are extremely difficult to 

measure or document given currently 

measured meteorological parameters 

and the locations of these 

measurements. The infrequency, short 

durations, and localized nature of such 

events makes it difficult to use currently 

available, general meteorological data, 

which are usually collected at isolated 

locations such as airports, to determine 

whether a stratospheric ozone intrusion 

has occurred. The EPA believes that it 

is important to differentiate between 

stratospheric ozone intrusion, which is 

an exceptional event for the purpose of 

flagging data, and other non-exceptional 

meteorological events. Although data 

have been identified in the past showing 

the result of stratospheric ozone 

intrusion, no standard definition or 

criteria have been established for 

concrete identification. Therefore, EPA’s 

determination of whether a 

stratospheric ozone intrusion has 

occurred is a case-by-case decision 

based on reasonable judgment 

considering the season of the year, time 

of day, persistence, duration, type and 

severity of accompanying 

meteorological conditions associated 

with the ozone measurement in 

question, and other data showing that 

conditions were not conducive to local 

high ozone production but for this 

intrusion. 

2. Final Rule 

The EPA is finalizing its rule as 

proposed. The EPA’s determination of 

whether a stratospheric ozone intrusion 

has occurred will be made on a case-bycase basis based on reasonable judgment 

considering the criteria as noted above. 

It is our intention to review this type of 

exceptional event during the next 

review of the NAAQS for ozone. A 

review of historical data related to the 

flagging of stratospheric ozone intrusion 

as an exceptional event shows that the 

event has only been flagged on a few 

isolated occasions. 

VIII. Treatment of Fireworks Displays 

A. Background 

The EPA proposed to treat emissions 

due to fireworks displays in a manner 

similar to exceptional events. Some 

national and/or cultural traditions, such 

as July 4th Independence Day and the 

Chinese New Year, have long included 

fireworks displays as important 

elements of their observances. While 

this issue is not specifically covered in 

CAA section 319, EPA believes that 

Congress did not intend to require EPA 

to consider air quality violations 

associated with such cultural traditions 

in regulatory determinations. 

We are not aware of any information 

showing adverse air quality impacts 

caused by individual use of fireworks in 

relatively small quantities. However, 

analyses of monitoring data collected on 

July 4th and July 5th indicates that large 

fireworks displays, in combination with 

other sources, can in some 

circumstances be potentially significant 

sources of air pollutant emissions. For 

this reason, States are encouraged to 

take reasonable precautions to minimize 

exposures to emissions from fireworks 

displays, to explore the use of lower 

emitting fireworks, as well as to manage 

associated activities that may also have 

significant air quality impacts in the 

areas where these events are held. Such 

precautions may include alerting the 

public to the potential for short-term air 

quality impacts that may result from the 

discharge of fireworks at large displays, 

monitoring prevailing winds, and 

locating displays downwind of 

concentrations of people. For these 

reasons, where States can show that the 

use of fireworks displays was integral to 

significant traditional national, ethnic, 

or other cultural events, we proposed 

that air quality data associated with 

such events could be excluded similar 

to exceptional events under this rule. 

B. Final Rule 

The EPA is finalizing the approach as 

stated in the proposed rule to treat 

emissions from fireworks similar to the 

treatment of exceptional events in the 

final rule provided that the event meets 

the other criteria as stated in this 

rulemaking. For example, the event 

must be determined to have affected air 

quality. Where a State can show that the 

use of fireworks is significantly integral 

to traditional national, ethnic, or other 

cultural events (e.g., July Fourth 

celebrations, Chinese New Year 

celebrations, Diwali, etc.), EPA will 

exclude data from regulatory 

determinations for monitoring stations 

whose exceedances or violations has 

been determined to be caused by 

emissions from fireworks displays on a 

case-by-case basis. As stated in other 

parts of the rule, States must assure that 

reasonable measures were taken to 

protect the public from the emissions 

created by the fireworks display. Under 

this rule, States are also strongly 

encouraged to institute educational 

programs that alert the public to the 


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health effects associated with exposure 

to emissions from fireworks displays. 

C. Comments and Responses 

Comment: The majority of 

commenters who commented on this 

issue agreed that emissions from 

fireworks should be treated as an 

exceptional event. However, some 

commenters disagreed with EPA’s 

proposal to treat fireworks as an 

exceptional event. Several commenters 

believed that fireworks are neither an 

exceptional event nor a natural event 

and that EPA should not make 

provisions for fireworks to be excluded 

as an exceptional event. 

Response: In considering the intent of 

the SAFETEA–LU legislation, it is EPA’s 

belief that Congress did not intend to 

prohibit the exclusion of data affected 

by emissions from fireworks related to 

celebrations of national or cultural 

traditions. It is EPA’s belief that data 

influenced by fireworks displays should 

be subject to the same provisions as 

other exceptional events identified 

under this rule. Therefore, the 

mitigation actions described in section 

VI.A above would also apply to 

emissions related to fireworks displays. 

IX. Statutory and Executive Order 

Reviews 

A. Executive Order 12866: Regulatory 

Planning and Review 

Under Executive Order 12866 (58 FR 

51735, October 4, 1993), this action is a 

significant regulatory action because it 

raises novel legal or policy issues 

arising out of legal mandates. 

Accordingly, EPA submitted this action 

to the Office of Management and Budget 

(OMB) for review under Executive 

Order 12866 and any changes made in 

response to OMB recommendations 

have been documented in the docket for 

this action. 

B. Paperwork Reduction Act 

This action does not impose an 

information collection burden. The 

information being requested under this 

rule is consistent with current 

requirements related to information 

needed to verify the authenticity of 

monitoring data submitted to EPA’s 

AQS database, and to justify data that 

has been flagged as being affected by 

exceptional or natural events. However, 

the OMB has previously approved the 

information collection requirements 

regulations for ambient air monitoring 

contained in 40 CFR part 58, subparts A 

through E, under the provisions of the 

Paperwork Reduction Act, 44 U.S.C. 

3501 et seq. and assigned OMB control 

number 2060–0084, EPA ICR number 

940.17. A copy of the OMB approved 

Information Collection Request (ICR) 

may be obtained from Susan Auby, 

Collection Strategies Division; U.S. 

Environmental Protection Agency 

(2822T); 1200 Pennsylvania Ave., NW., 

Washington, DC 20460 or by calling 

(202) 566–1672. 

Burden means that total time, effort, 

or financial resources expended by 

persons to generate, maintain, retain, or 

disclose or provide information to or for 

a Federal agency. This includes the time 

needed to review instructions; develop, 

acquire, install, and utilize technology 

and systems for the purposes of 

collecting, validating, and verifying 

information, processing and 

maintaining information, and disclosing 

and providing information; adjust the 

existing ways to comply with any 

previously applicable instructions and 

requirements; train personnel to be able 

to respond to a collection of 

information; search data sources; 

complete and review the collection of 

information; and transmit or otherwise 

disclose the information. An Agency 

may not conduct or sponsor, and a 

person is not required to respond to a 

collection of information unless it 

displays a currently valid OMB control 

number. The OMB control numbers for 

EPA’s regulations in the CFR are listed 

in 40 CFR part 9. 

C. Regulatory Flexibility Act 

The Regulatory Flexibility Act 

generally requires an agency to prepare 

a regulatory flexibility analysis of any 

rule subject to notice and comment 

rulemaking requirements under the 

Administrative Procedures Act or any 

other statute unless the EPA certifies 

that the rule will not have a significant 

economic impact on a substantial 

number of small entities. Small entities 

include small businesses, small 

organizations, and small governmental 

jurisdictions. For the purpose of 

assessing the impacts of this final rule 

on small entities, small entity is defined 

as: (1) A small business as defined by 

the Small Business Administration’s 

regulations at 13 CFR 121.201; (2) a 

small governmental jurisdiction that is a 

government of a city, county, town, 

school district or special district with a 

population of less than 50,000; and (3) 

a small organization that is any not-forprofit enterprise which is independently 

owned and operated and is not 

dominate in its field. 

Courts have interpreted the RFA to 

require a regulatory flexibility analysis 

only when small entities will be subject 

to the requirements of the rule. See, 

Michigan v. EPA, 213 F.3d 663, 668–69 

(DC Cir., 2000), cert. den., 532 U.S. 903 

(2001). This rule would not establish 

requirements applicable to small 

entities. Instead, this rule provides the 

criteria necessary for State, local, or 

Tribal air quality agencies to meet in 

order to properly flag data as being 

influenced by an exceptional or natural 

event. The rule also provides 

information concerning what action 

should be taken by a State, local, or 

Tribal air quality agency to protect 

public health during and following an 

exceptional or natural event. Because 

affected States would have discretion to 

implement controls on sources that may 

need to be regulated due to 

anthropogenic contribution in the area 

determined to be influenced by an 

exceptional or natural event, EPA could 

not predict the effect of the rule on 

small entities. 

After considering the economic 

impacts of this final rule on small 

entities, I certify that this rule will not 

have a significant economic impact on 

a substantial number of small entities. 

D. Unfunded Mandates Reform Act 

Title II of the Unfunded Mandates 

Reform Act of 1995 (UMRA), Public 

Law 104–4, establishes requirements for 

Federal Agencies to assess the effects of 

their regulatory actions on State, local 

and Tribal governments and the private 

sector. Under section 202 of the UMRA, 

EPA generally must prepare a written 

statement, including a cost-benefit 

analysis, for proposed and final rules 

with ‘‘Federal mandates’’ that may 

result in expenditures to State 

governments, in the aggregate, or to the 

private sector, of $100 million or more 

in any 1 year. Before promulgating an 

EPA rule for which a written statement 

is needed, section 205 of the UMRA 

generally requires EPA to identify and 

consider a reasonable number of 

regulatory alternatives and adopt the 

least costly, most cost-effective or least 

burdensome alternative that achieves 

the objectives of the rule. The 

provisions of section 205 do not apply 

when they are inconsistent with 

applicable law. Moreover, section 205 

allows EPA to adopt an alternative other 

than the least costly, most cost-effective 

or least burdensome alternative if the 

Administrator publishes with the final 

rule an explanation of why that 

alternative was not adopted. Before EPA 

establishes any regulatory requirements 

that may significantly or uniquely affect 

small governments, including Tribal 

governments, it must have developed 

under section 203 of the UMRA a small 

government agency plan. The plan must 

provide for notifying potentially 

affected small governments to have 

meaningful and timely input in the 


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Federal Register / Vol. 72, No. 55 / Thursday, March 22, 2007 / Rules and Regulations 13579 

development of EPA regulatory 

proposals with significant Federal 

intergovernmental mandates, and 

informing, educating, and advising 

small government on compliance with 

regulatory requirements. 

We have determined that this rule 

does not contain a Federal mandate that 

may result in expenditures of $100 

million or more for State, local, and 

Tribal governments, in the aggregate, or 

the private sector in any 1 year. This 

action simply provides the criteria for 

State, local, or Tribal air quality 

agencies to flag data to be discounted for 

regulatory purposes that is being 

influenced by exceptional or natural 

events. Thus, this rule is not subject to 

the requirements of sections 202, 203, 

and 205 of the UMRA. 

E. Executive Order 13132: Federalism 

Executive Order 13132, entitled 

‘‘Federalism’’ (64 FR 43255, August 10, 

1999), requires EPA to develop an 

accountable process to ensure 

‘‘meaningful and timely input by State 

and local officials in the development of 

regulatory policies that have federalism 

implications.’’ ‘‘Policies that have 

federalism implications’’ is defined in 

the Executive Order to include 

regulations that have ‘‘substantial direct 

effects on the States, or the relationship 

between the national government and 

the States, or on the distribution of 

power and responsibilities among the 

various levels of government.’’

This final rule does not have 

federalism implications. It will not have 

substantial direct effects on the States, 

on the relationship between the national 

government and the States, or on the 

distribution of power and 

responsibilities among the various 

levels of government, as specified in 

Executive Order 13132. The CAA 

establishes the scheme whereby States 

take the lead in developing plans to 

meet the NAAQS. Thus, Executive 

Order 13132 does not apply to this rule. 

F. Executive Order 13175: Consultation 

and Coordination With Indian Tribal 

Governments 

Executive Order 13175, entitled 

‘‘Consultation and Coordination with 

Indian Tribal Governments’’ (65 FR 

67249, November 9, 2000), requires EPA 

to develop an accountable process to 

ensure ‘‘meaningful and timely input by 

Tribal officials in the development of 

regulatory policies that have Tribal 

implications.’’ This final rule does not 

have ‘‘Tribal implications’’ as specified 

in Executive Order 13175. The rule 

provides information concerning what 

action should be taken by a State, local, 

or Tribal air quality agency 

implementing relevant air quality 

programs to protect public health once 

EPA has provided a concurrence on data 

that has been flagged as being 

influenced by an exceptional or natural 

event. The CAA and the Tribal 

Authority Rule (TAR) give Tribes the 

opportunity to develop and implement 

CAA programs, but it leaves to the 

discretion of the Tribe whether to 

develop these programs and which 

programs, or appropriate elements of a 

program, the Tribe will adopt through 

the Tribal Implementation Plan (TIP). 

This rule does not have Tribal 

implications as defined by Executive 

Order 13175. It does not have a 

substantial direct effect on one or more 

Indian Tribes, because no Tribe has 

implemented a TIP related to the PM or 

the 8-hour ozone NAAQS at this time. 

Furthermore, this rule does not affect 

the relationship or distribution of power 

and responsibilities between the Federal 

government and Indian Tribes. The 

CAA and the TAR establish the 

relationship of the Federal government 

and Tribes in developing plans to attain 

the NAAQS, and this rule does nothing 

to modify that relationship. Because this 

rule does not have Tribal implications, 

Executive Order 13175 does not apply. 

However, even though we found that 

this rule does not have Tribal 

implications, we nevertheless were 

aware of Tribes that had an interest in 

this rule. Therefore, we conducted 

communications and outreach related to 

the rule with the Tribes through 

discussions via conference calls with 

the Tribal Association. We also 

provided information to the Tribes on 

the rule via the Quarterly Tribal Air 

Newsletter. 

G. Executive Order 13045: Protection of 

Children From Environmental Health 

and Safety Risks 

Executive Order 13045: ‘‘Protection of 

Children From Environmental Health 

and Safety Risks’’ (62 FR 19885, April 

23, 1997) applies to any rule that (1) is 

determined to be ‘‘economically 

significant’’ as defined under Executive 

Order 12866, and (2) concerns an 

environmental health and safety risk 

that EPA has reason to believe may have 

a disproportionate effect on children. If 

the regulatory action meets both criteria, 

EPA must evaluate the environmental 

health or safety effects of the planned 

rule on children, and explain why the 

planned regulation is preferable to other 

potentially effective and reasonably 

feasible alternatives considered by EPA. 

This action is not subject to Executive 

Order 13045 because it is not 

economically significant as defined in 

Executive Order 12866, and because 

EPA does not have reason to believe that 

the environmental health risks or safety 

risks addressed by this rule present a 

disproportionate risk or safety risk to 

children. The rule provides information 

concerning what action should be taken 

by a State, local, or Tribal air quality 

agency to protect public health once 

EPA has provided a concurrence on data 

that has been flagged as being 

influenced by an exceptional or natural 

event. 

H. Executive Order 13211: Actions That 

Significantly Affect Energy Supply, 

Distribution, or Use 

This rule is not a ‘‘significant energy 

action’’ as defined in Executive Order 

13211, ‘‘Actions That Significantly 

Affect Energy Supply, Distribution, or 

Use,’’ (66 FR 28355, May 22, 2001) 

because it is not likely to have a 

significant adverse effect on the supply, 

distribution, or use of energy. Further, 

we have concluded that this rule is not 

likely to have any adverse energy 

effects. 

I. National Technology Transfer 

Advancement Act 

Section 12(d) of the National 

Technology Transfer Advancement Act 

of 1995 (NTTAA), Public Law No. 104–

113, section 12(d) (15 U.S.C. 272 note) 

directs EPA to use voluntary consensus 

standards (VCS) in its regulatory 

activities unless to do so would be 

inconsistent with applicable law or 

otherwise impracticable. Voluntary 

consensus standards are technical 

standards (e.g., materials specifications, 

test methods, sampling procedures, and 

business practices) that are developed or 

adopted by VCS bodies. The NTTAA 

directs EPA to provide Congress, 

through OMB, explanations when EPA 

decides not to use available and 

applicable VCS. 

This action does not involve technical 

standards. Therefore, EPA did not 

consider the use of any VCS. 

J. Congressional Review Act 

The Congressional Review Act, 5 

U.S.C. 801 et seq., as added by the Small 

Business Regulatory Enforcement 

Fairness Act of 1996, generally provides 

that before a rule may take effect, the 

agency promulgating the rule must 

submit a rule report, which includes a 

copy of the rule, to each House of the 

Congress and to the Comptroller General 

of the United States. The EPA will 

submit a report containing this rule and 

other required information to the U.S. 

Senate, the U.S. House of 

Representatives, and the Comptroller 

General of the United States prior to 

publication of the rule in the Federal 


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13580 Federal Register / Vol. 72, No. 55 / Thursday, March 22, 2007 / Rules and Regulations 

Register. A major rule cannot take effect 

until 60 days after it is published in the 

Federal Register. This action is not a 

‘‘major rule’’ as defined by 5 U.S.C. 

804(2). This rule will be effective May 

21, 2007. 

K. Petitions for Judicial Review 

Under section 307(b)(1) of the CAA, 

petitions for judicial review of this 

action must be filed in the United States 

Court of Appeals for the District of 

Columbia Circuit by May 21, 2007. 

Filing a petition for reconsideration by 

the Administrator of this final rule does 

not affect the finality of this rule for the 

purposes of judicial review nor does it 

extend the time within which a petition 

for judicial review must be filed, and 

shall not postpone the effectiveness of 

such rule or action. This action may not 

be challenged later in proceedings to 

enforce its requirements. See CAA 

Section 307(b)(2). 

List of Subjects 

40 CFR Part 50 

Environmental protection, Air 

pollution control, National parks, 

Wilderness areas. 

40 CFR Part 51 

Environmental protection, Air 

pollution control, Administrative 

practice and procedure, Reporting and 

recordkeeping requirements. 

Dated: March 14, 2007. 

Stephen L. Johnson, 

Administrator. 

■ In consideration of the foregoing, the 

Environmental Protection Agency 

amends 40 CFR parts 50 and 51 as 

follows: 

PART 50—NATIONAL PRIMARY AND 

SECONDARY AMBIENT AIR QUALITY 

STANDARDS 

■ 1. The authority citation for part 50 

continues to read as follows: 

Authority: 42 U.S.C. 7401 et seq. 

■ 2. Amend § 50.1 to add paragraphs (j) 

and (k) to read as follows: 

§ 50.1 Definitions. 

* * * * * 

(j) Exceptional event means an event 

that affects air quality, is not reasonably 

controllable or preventable, is an event 

caused by human activity that is 

unlikely to recur at a particular location 

or a natural event, and is determined by 

the Administrator in accordance with 40 

CFR 50.14 to be an exceptional event. It 

does not include stagnation of air 

masses or meteorological inversions, a 

meteorological event involving high 

temperatures or lack of precipitation, or 

air pollution relating to source 

noncompliance. 

(k) Natural event means an event in 

which human activity plays little or no 

direct causal role. 

(l) Exceedance with respect to a 

national ambient air quality standard 

means one occurrence of a measured or 

modeled concentration that exceeds the 

specified concentration level of such 

standard for the averaging period 

specified by the standard. 

■ 3. Add § 50.14 to read as follows: 

§ 50.14 Treatment of air quality monitoring 

data influenced by exceptional events. 

(a) Requirements. (1) A State may 

request EPA to exclude data showing 

exceedances or violations of the 

national ambient air quality standard 

that are directly due to an exceptional 

event from use in determinations by 

demonstrating to EPA’s satisfaction that 

such event caused a specific air 

pollution concentration at a particular 

air quality monitoring location. 

(2) Demonstration to justify data 

exclusion may include any reliable and 

accurate data, but must demonstrate a 

clear causal relationship between the 

measured exceedance or violation of 

such standard and the event in 

accordance with paragraph (c)(3)(iii) of 

this section. 

(b) Determinations by EPA. (1) EPA 

shall exclude data from use in 

determinations of exceedances and 

NAAQS violations where a State 

demonstrates to EPA’s satisfaction that 

an exceptional event caused a specific 

air pollution concentration in excess of 

one or more national ambient air quality 

standards at a particular air quality 

monitoring location and otherwise 

satisfies the requirements of this 

section. 

(2) EPA shall exclude data from use 

in determinations of exceedances and 

NAAQS violations where a State 

demonstrates to EPA’s satisfaction that 

emissions from fireworks displays 

caused a specific air pollution 

concentration in excess of one or more 

national ambient air quality standards at 

a particular air quality monitoring 

location and otherwise satisfies the 

requirements of this section. Such data 

will be treated in the same manner as 

exceptional events under this rule, 

provided a State demonstrates that such 

use of fireworks is significantly integral 

to traditional national, ethnic, or other 

cultural events including, but not 

limited to July Fourth celebrations 

which satisfy the requirements of this 

section. 

(3) EPA shall exclude data from use 

in determinations of exceedances and 

NAAQS violations, where a State 

demonstrates to EPA’s satisfaction that 

emissions from prescribed fires caused 

a specific air pollution concentration in 

excess of one or more national ambient 

air quality standards at a particular air 

quality monitoring location and 

otherwise satisfies the requirements of 

this section provided that such 

emissions are from prescribed fires that 

EPA determines meets the definition in 

§ 50.1(j), and provided that the State has 

certified to EPA that it has adopted and 

is implementing a Smoke Management 

Program or the State has ensured that 

the burner employed basic smoke 

management practices. If an exceptional 

event occurs using the basic smoke 

management practices approach, the 

State must undertake a review of its 

approach to ensure public health is 

being protected and must include 

consideration of development of a SMP. 

(4) [Reserved] 

(c) Schedules and Procedures. (1) 

Public notification. 

(i) All States and, where applicable, 

their political subdivisions must notify 

the public promptly whenever an event 

occurs or is reasonably anticipated to 

occur which may result in the 

exceedance of an applicable air quality 

standard. 

(ii) [Reserved.] 

(2) Flagging of data. 

(i) A State shall notify EPA of its 

intent to exclude one or more measured 

exceedances of an applicable ambient 

air quality standard as being due to an 

exceptional event by placing a flag in 

the appropriate field for the data record 

of concern in accordance with the 

schedules for submission of data to the 

AQS database in 40 CFR 58.16. 

(ii) Flags placed on data in accordance 

with this section shall be deemed 

informational only, and the data shall 

not be excluded from determinations 

with respect to exceedances or 

violations of the national ambient air 

quality standards unless and until, 

following the State’s submittal of its 

demonstration pursuant to paragraph 

(c)(3) of this section and EPA review, 

EPA notifies the State of its concurrence 

by placing a concurrence flag in the 

appropriate field for the data record in 

the AQS database. 

(iii) Flags placed on data as being due 

to an exceptional event together with an 

initial description of the event shall be 

submitted to EPA not later than July 1st 

of the calendar year following the year 

in which the flagged measurement 

occurred, except as allowed under 

paragraph (c)(2)(iv) of this section. 

(iv) For PM2.5 data collected during 

calendar years 2004–2006, that the State 

identifies as resulting from an 


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exceptional event, the State must notify 

EPA of the flag and submit an initial 

description of the event no later than 

October 1, 2007. EPA may grant an 

extension, if a State requests an 

extension, and permit the State to 

submit the notification of the flag and 

initial description by no later than 

December 1, 2007. 

(v) When EPA sets a NAAQS for a 

new pollutant, or revises the NAAQS for 

an existing pollutant, it may revise or 

set a new schedule for flagging data for 

the initial designation of areas for those 

NAAQS. 

(3) Submission of demonstrations. 

(i) A State that has flagged data as 

being due to an exceptional event and 

is requesting exclusion of the affected 

measurement data shall, after notice and 

opportunity for public comment, submit 

a demonstration to justify data 

exclusion to EPA not later than the 

lesser of, 3 years following the end of 

the calendar quarter in which the 

flagged concentration was recorded or, 

12 months prior to the date that a 

regulatory decision must be made by 

EPA. A State must submit the public 

comments it received along with its 

demonstration to EPA. 

(ii) A State that flags data collected 

during calendar years 2004–2006, 

pursuant to paragraph (c)(2)(iv) of this 

section, must adopt the procedures and 

requirements specified in paragraph 

(c)(3)(i) of this section and must include 

a demonstration to justify the exclusion 

of the data not later than the submittal 

of the Governor’s recommendation letter 

on nonattainment areas. 

(iii) The demonstration to justify data 

exclusion shall provide evidence that: 

(A) The event satisfies the criteria set 

forth in 40 CFR 50.1(j); 

(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. 

(iv) With the submission of the 

demonstration, the State must document 

that the public comment process was 

followed. 

(v) [Reserved.] 

(A) [Reserved] 

PART 51—NATIONAL PRIMARY AND 

SECONDARY NATIONAL AMBIENT AIR 

QUALITY STANDARDS 

■ 4. The authority citation for part 51 

continues to read as follows: 

Authority: 23 U.S.C. 101; 42 U.S.C. 7401–

7671q. 

■ 5. Adding Subpart Y consisting of 

§ 51.930 to read as follows: 

Subpart Y—Mitigation Requirements 

§ 51.930 Mitigation of Exceptional Events. 

(a) A State requesting to exclude air 

quality data due to exceptional events 

must take appropriate and reasonable 

actions to protect public health from 

exceedances or violations of the 

national ambient air quality standards. 

At a minimum, the State must: 

(1) Provide for prompt public 

notification whenever air quality 

concentrations exceed or are expected to 

exceed an applicable ambient air quality 

standard; 

(2) Provide for public education 

concerning actions that individuals may 

take to reduce exposures to unhealthy 

levels of air quality during and 

following an exceptional event; and 

(3) Provide for the implementation of 

appropriate measures to protect public 

health from exceedances or violations of 

ambient air quality standards caused by 

exceptional events. 

(b) [Reserved] 

[FR Doc. E7–5156 Filed 3–21–07; 8:45 am] 

BILLING CODE 6560–50–P 


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