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

ENVIRONMENTAL PROTECTION

AGENCY

40 CFR Parts 50 and 51 [EPA-HO-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 andregulatory process established bythe Clean Air Act (CAA) is not appropriate. In this rulemaking action, EPA is finalizing theproposal 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 ofthe 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 ifa State adequately demonstrates that an exceptional event has caused an exceedance or violation ofa NAAQS. The EPA is also requiring States to take reasonable measures to mitigate the impacts ofan exceptional
event. DATES: This final rule is effective May 21, 2007. ADDRESSES: The EPA has established a docket forthis action underDocket ID No. EPA-HQ-OAR-2005-0159. All documents inthe docket are listed on thehttp://www.regulations.goir 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.govor inhard 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 Readjig Room is (202) 566-1744, and the telephone number for the Air andRadiation 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 ofAir 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 shouldbe addressed to Mr. Neil Frank, Office ofAir 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 fraik.neil@epa.gov.

SUPPLEMENTARY INFORMATION:

I. General Information

A. Does ThisActionApply toMe? RegulatedEntities.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 orhave 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 ofthe types ofentities 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 ofthis preamble. Ifyou have any questions regarding the applicability ofthis action to a particular entity; consult the people listed in the preceding section.

B.How Is ThisPreambleOrganized?

Table ofContents

Thefollowing is an outline ofthe preamble. I.General Information

A.Does ThisAction Apply to Me? B.How IsThisPreamble Organized? II.Preamble Glossary ofTerms and Acronyms III. Background andPurpose ofThis Rulemaking A.Legislative Requirements B.Historical Experience Concerning

Exceptional andNatural Events IV. ThisFinal Action

A. toWhom andto What Pollutants Does

ThisRule Apply? B.How DoesThis Rule Relateto Indian

Tribes? C. Comments Submitted on the Proposed Rule D. What Is an Exceptional Event? E. Examples ofExceptional 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 ofAir Quality Data Affected by Exceptional Events A. Flagging ofData in the AQS Database 1. Background 2. Final Rule 3. Comments and Responses B. WhatDoes It Mean for an Event to

"Affect Air Quality"? 1.Background 2. Final Rule 3. Comments and Responses C. Use ofa "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 ofEntire 24-Hour Value as

- Opposed to a Partial Adjusfment ofthe

24-Hour Value 1.Background 2.Final Rule 3. Comments and Responses F. What Should States Be Required To

Submit inTheir Exceptional Events Demonstrations? 1.Background 2. Final Rule 3. Comments and Responses G.Public Availability ofAir 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, andAppropriate andReasonable Measures To ProtectPublic Health 1. Background 2. Final Rule 3. Comments and Responses VII. Special Treatment ofCertain Exceptional Events Under ThisFinal 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 

### 13560

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

A. Background B.Final Rule C. Comments andResponses IX. Statutory and Executive Order Reviews A. Executive Order 12866: Regulatory

Planning andReview 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 forJudicial Review

II. Preamble Glossary ofTerms and Acronyms

The following are abbreviations of
terms used inthe 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 Actof 1995. OAQPS Office ofAir Quality Planning

and Standards. OMB Office ofManagement and

Budget. PM Particulate matter. PM10 Particles with a nominal mean

aerodynamic diameter less than or equal to 10 micrometers. PM 10-2.5 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 ofAgriculture. VCS Voluntary Consensus Standards.

Ill. Background and PurposeofThis Rulemaking

A. LegislativeRequirements

We 1are finalizing arule 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 ofthe CAA, as amended by section 6013 ofthe Safe Accountable Flexible EfficientTransportation Equity Act: ALegacy for Users (SAFE-TEA-LU) of2005, required EPA to publish the proposed rule inthe Federal Register no later than March 1, 2006.2 Further; EPA must issue this final rule no later than 1year from the date ofproposal. The EPA

- published the proposed rule on March 10, 2006 (See 71 FR 12592).

In this finalrule, EPA is establishing procedures and criteria related to the identification, ealuation, interpretation, and use of airquality monitoring datarelated 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 ifthe event affects air quality; is an event thatis not reasonably controllable or preventable; is an event caused by human activity that is unlikely torecur at a.particular location or a natural event; and is determined byEPA tobe an exceptional
event. The statutory definition of exceptional event specifically excludes stagnation of air masses or meteorological inversions; a meteorological event involving high temperatures orlack ofprecipitation; or air pollution relating to source noncompliance.

Section 319(b)(3)(B)(i) requires a State air quality agency to demonstrate through "reliable, accurate datathat is promptly produced" that an exceptional
event occurred.3 Section 319(b)(3)(B)(ii) requires that "a clear causal

IThe U.S. Environmental Protection Agency.

2All subsequent references to section 319 ofthe CAA inthis proposal areto section 319as amended by SAFE-TEA-LU .unlessotherwise noted.

3While thisdfcument refers primarilyto States

as the entityresponsible forflagging data impacted by exceptional events, otheragencies, such aslocal

or Tribal government agencies, may also have standing to flag dataas being affected by these types ofevents, andthe criteria andprocedures that are discussed in thisrulemaking alsoapply tothese entities. relationship" beestablished between a measured exceedance of aNAAQS 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 aGovernor topetition the Administrator to exclude air quality monitoring data that is directly due to exceptional events from use in determinations with respect to exceedances orviolations ofthe NAAQS.

The term exceedance refers to a measured or modeled concentration greater than the level ofone ormore 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 ofthe NAAQS for ozone and PM2.5 requires an average annual concentration level specified by appendix I and N to 40 CFR 50 tobe greater than the level ofthe NAAQS. Public comments favoredthe consideration ofdata contributing to both exceedances andviolations for data exclusion under this Rule. As discussed in section V.C, exceedances ofany NAAQS will be eligible for considerhtion for dataexclusion and any data contributing toviolations of daily or sub-daily standards willalso be eligible for consideration (e.g. 8-hour or 24-hour standards). Data .contributingto annual violations withoutbeing 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 forEPA to follow in developing regulations to implement section 319:

(i)

Protection ofpublic healthis thehighest priority;

(ii)Timely information should be provided to the public inany casein which theair quality isunhealthy;

(iii)All ambient air quality data should be included in a timely manner in an appropriate Federal air quality database that is accessible to thepublic;

(iv)Each State must take necessary heasures to safeguard public health regardless ofthe source oftheairpollution; and

(v) Airquality data should be carefully screened to ensure thatevents not likelyto

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 reliefto States to allow them to avoid being designated as nonattainment or to avoid continuing to be designated. 

### 13561

HeinOnline -- 72 Fed. Reg. 13561 2007

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

nonattainment as aresult ofexceptiona events in appropriate circumstances. Ti accomplish thisgoal, Congress enumerated certain minimum requirements forthis rulemaking. In addition, Congress provided certain statutory principles for EPA to follow i] promulgating regulations to exclude data affected by exceptional events.

B. Historical ExperienceConcerning ExceptionalandNatural 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 firstEPA guidance related to the exclusion or discounting ofdata affected by an exceptional event was an Office ofAir Quality Planning and Standards (OAQPS) guidance document entitled, "Guideline for the Interpretation ofAir Quality Standards," Guideline No. 1.2- 008 (revisedFebruary 1977).4

In July 1986, EPA issued the guidanci entitled, "Guideline On the Identification and Use ofAir Quality Data Affected By Exceptional Events" (theExceptional Events Policy). The Exceptional Events Policyprovided criteria for States to use in making decisions related toidentifying data tha 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 aerodynami diameter of 10 micrometers orless), which also addressed the issue of excluding or discounting data affected by exceptional events. 5 Appendix K of that rule allows for special consideration ofdata determined tobe affected by an exceptional event. Section 2.4 ofappendix K authorizes EPA to discount from consideration in making attainment ornonattainment determinations air quality data that are attributable to "an uncontrollable event caused by natural sources" ofPM,. or "an eventthat is not expected to recur at a given location." Section 2.4 of appendix K, together with EPA guidance contained inthe Exceptional Exients Policy, describes the steps that

4"Guideline for Interpretation ofAir quality Standards," U.S. Environmental Protection Agency Office of Air quality Planning and Standaids, Research Triangle Park, N.C. OAQPS No. 1.2-008 (Revised February 1977). The guidance indicated theneed for a data flagging system which would require the submittal ofdetailed information establishing that aviolation was due to uncontrollable natural sources and that the information could be used in decision making related to the feasibility ofmodifying control strategies.

5Federal Register (52 FR 24667), July 1, 1987. I should be taken for flagging PM 0 data

o that a State believes are affected by an exceptional ornatural event. "

In 1990, section 188(f was added to the CAA. This section ofthe CAA provided EPA authority to waive either.

n a specific attainment date or certain planning requirements for serious PM10 nonattainment areas that are affected by nonanthropogenic sources. Inresponse 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 policytoaddress data affected by natural events entitled, "Areas Affected by PM10 Natural Events," (thePM10 Natural E-ents Policy).6

.OnJuly 18, 1997, EPA issued a revised NAAQS for ozone and a new NAAQS addressing PM 2. 5. For ozone, the revised NAAQS provided for an 8- hour averaging period (versus 1hour for the previous.NAAQS), and the level of the standard was changed from 0.12

e ppm to 0.08 ppm (62 FR 38856). Forthe PM2. 5 NAAQS, EPA established both a nbw 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 t determining whether an area is in attainment ofthe 8-hourozone 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 tobe influenced natural events, and section 1.0(b) of appendix N, related to the PM2. 5 standard, providesthat EPA may give special consideration to data determined tobe affected by an exceptional ornatural event.

Appendices K, I, and N, which are parts ofthe NAAQS forthe affected pollutants as described above, provide that, while States must submitall 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 thathave been appropriately flagged from calculations in determining whether ornot an area has attained the standard. These decisions are to be made on a case-bycase basisusing all available information relatedto the event in question, and arerequired tobe made available tothepublic for review. It should also be noted that, while it

eMemorandum fromMary D. Nicols, Assistant Administrator for Air and Radiation, to EPA Regional Offices entitled, "Areas Affected-by PM1o Natural Events," May 30, 1996. would be desirable tobe able to adjust the daily value to exclude only those portions ofthe 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 ofthe 8- hour ozone and the PM2
. 5 NAAQS, EPA provided additional guidance to States

on how to address data affected by exceptional andnatural events.7 Thatguidance directed the States to follow three specific EPA guidance documents inmaking 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 onWildland and Prescribed Fires, Memorandum fromRichard D. Wilson, Acting Assistant Administrator for Air andRadiation, to EPA Regional Administrators, May 15, 1998. The nterimAir Quality Policy on Wildland and Prescribed Fires addressed the treatment ofair quality monitoring data that are affected by wildland and lrescribed fires that are managed for

resource benefits.8

IV. This Final Action

A.-To Whom andto WhatPollutants Does ThisRuleApply?

Under the statutory scheme• established by the CAA, States are primarily responsible for the administration ofair quality management programs within their borders. This includes the monitoring and analysis ofambient air quality and submission ofmonitoring data to EPA, which are then stored inEPA's AQS database. The EPA retains an important oversight responsibility for ensuring compliance with CAA requirements. With respect to the treatment ofair quality monitoring data, States are responsible for ensuring dataquality and validity and for identifying
measurements that they believe warrant special consideration, whileEPA is

7"Guideline on Data Handling Conventions for the PMNAAQS," United States Environmental Protection Agency, Office ofAir Quality Planning and Standards, Research Triangle Park, NC 27711, EPA-454/R-98-017, December 1998.

8 Following thepromulgation ofthis rule,it is EPA's intention to begin the process to revise the "Interim Air QualityPolicy on Wildland and Prescribed Fires" in calendar year2007 to update thepolicy and to ensure that the policy is consistent with'this final rulemaking action. In addition, itis EPA'sintent that agricultural prescribed burning will beaddressed when tlis policy is updated and will also address basic smoke management practices. 

### 13562

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

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 onTribal lands, this rule would govern those actions as well.

Atpresent, only theNAAQS for ozone and particulate matter (PM)contain provisions which allowfor the special handling of air quality data affected by exceptional and natural events (40 CFR part 50, appendices K, I, andN). The language ofsection 319 ofthe CAA is broad in terms ofmaking 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 ofdata due to exceptional events, we are only applying the provisions ofthisrule initially to ozone and PM.9 As we review and consider the need forrevisions 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 ofa new or revised NAAQS willnecessitate 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. Inthe interim, where exceptional events result in exceedances

or violations ofNAAQS that do not currently provide for special treatment ofthe data, we intend to use our discretion as outlined under section

9Section IV.G ofthe preamble to the Proposed Rule discussed special considerations relevantto a

new NAAQS forPMIo-2.sproposed by EPA on December 20, 2005. This proposed standard would have drawn adistinction between coarse particles ofurban versus non-urban origin, which raised new issues about thehandling ofexceedances ofthe

coarse particle standard caused by exceptional
events. However, in EPA's final ruleon the PM NAAQS, issued September 21,2006, EPA retained the existing 24-hourPM,o standard instead of promulgating the proposed PMo 2.5standard. Thus, section IV.G ofthe preamble to the Proposed Rule is no longer relevant andhas been removed from this Preamble. 107(d)(3) not to redesignate affected

areas as nonattainment based on these
events. We also intendto use our discretion under this ruleto address determinations for the ozone standard related to the treatment ofdata influenced byboth exceptional and natural events. Currently, appendix I, only addresses the treatment ofdata determined tobe influenced by a stratospheric ozone intrusion and other natural events, but does not address the handling ofdata influenced by other exceptional events.

B. HowDoes ThisRuleRelatetoIndian Tribes?

Under the CAA and the Tribal Authority Rule (TAR), eligible Indian Tribes may develop and submit Tribal Implementation Plans (TIPs) forEPA approval, to administer requirements under the CAA on theirreservations and otherareas undertheirjurisdiction. However, Tribes are not required to develop TIPs orotherwise implement relevant programs under the CAA. The EPA has stated that it will continue to

ensure theprotection ofair quality throughout the nation, including in Indian country, andwill issue Federal Implementation Plans (FIPs) as necessary or appropriate to fill gaps in program implementation in affected

areas ofIndian 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 usedto exclude

or discount data for regulatory purposes. Certain Tribes may implement all relevant components ofan air quality program for purposes ofmeeting the various requirements ofthis rule. In

some cases, however,'a Tribe may implement onlyportions ofthe relevant
program and may notbe in a position
to address each ofthe procedures and requirements associated with excluding

or discounting emissions data (e.g., a particular Tribe may operate a monitoring network forpurposes of gathering and identifying appropriate data, but may not implement relevant programs for the purpose ofmitigating the effects of exceptional events required under this rule). The EPA intends to work with Tribes onthe implementation of thisrule, which may include appropriate implementation by EPA ofprogram elements ensuring that
any exclusion or discounting of datain Indian country areas with air quality affected byexceptional events comports withthe procedures and requirements ofthis rule. C.CommentsSubmittedon the Proposed Rule

The proposed rule on the "Treatment ofData Influenced byExceptional Events" was issued on March 10, 2006 (71 FR 12592). We received 98 letters fromcommenters representing 587

. comments from private citizens, State and local governments, industry, environmental groups"and Federal agencies. Sections V, VI, VII, andVIII of this notice describe the primary elements and requirements concerning the process for the handling ofdata 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 ofthe rule. We have developed a response to comments document which addresses all ofthe timelycomments received on theproposed rule. Following the promulgation ofthisrule, the response to comments document will be placed into the docket ofthis rulemaking action for public review (SeeDocket No. EPA-HQ-OAR-2005- 0159).

D. WhatIs anExceptional Event?

In accordance with the language in section 319, EPA is defining theterm "exceptional event" to mean an event that:

(i)Affects air quality; (ii).Is notreasonably controllable or preventable;

(iii)Is an event caused byhuman activity that isunlikely to recur ata particular location or a natural event; and

(iv)Is determined by EPA through the
process established inthese regulations to be

an exceptional event.

It is important tonote 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 ofthis rule,EPA is defining "natural event" as an event in which human activity plays little orno direct causal role tothe eventin question. We recognize that over time, certain human activities mayhave had

some impact on the conditions which later give riseto a "natural" air pollution event. However, we do not believe that small historical human contributions shouldpreclude an event from being deemed "natural." In adopting section 188(f) ofpart D, subpart 4, ofthe 1990 amendments to 

### 13563

HeinOnline -- 72 Fed. Reg. 13563 2007

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

the CAA, Congress recognized and provided for distinctions between these types ofevents with respect to waiver of applicable requirements and the extension of otherwise applicable attainment dates forthe PMio standard. In approving section 188(f) ofthe CAA,- the House committee ofjurisdiction discussed a circumstance inwhich recurring emissions from a source should be considered tobe anthropogenic. The House report noted EPA statements that, in the cited case, high concentrations ofdust from a lakebed were due to human activity, i.e., the long-term diversion ofwater from a lake. (See Pub. L. 101-549, CAA Amendments of 1990 House Report No. 101-290(1), May 17, 1990; and discussion ofMono Lake, California therein). Also, EPA recognized, in recently acting to retain PM10 as a

measure ofcoarse particulate, that in

some instances exceedances ofthis NAAQS "may be caused inwhole orin 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 orpreventable" because we believe that such determinations will necessarily be dependent on specific facts and circumstances that cannot be prescribed by rule.

E.ExamplesofExceptionalEvents

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 thisrule provided that all otherrequirements ofthe 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 thisrule
may also qualify for exclusion. The AQS

user documentation contains a listof other similar events that may be flagged for special consideration. (http:// www.epa.gov/ttn/airs/airsaqs/man uals/ qualifiers.htm),1 0 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 thatmay meet the definition ofan 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 ofthese may be flagged

as an exceptional event.

CommentsandResponses

Comment: Several commenters stated that "Chemical Spills and Industrial Accidents" should generally notbe 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 havebeen avoided is inconsistent with the CAA.

Response:It is EPA's belief that air quality data thathas been affected by emissions from chemical spills, industrial accidents, or structural fires maybe flagged by a State as an exceptional event andreviewed byEPA for exclusion on acase-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
-tobe due to circumstances that were not reasonably controllable or preventable and are.eventsthat areunlikely to recur ina 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 shouldbe addressed through the normal State Implementation Planning
process.
2. Structural Fires

Structural fires include any accidental fire involving amanmade structure.
CommentsandResponses

Comment:Several commenters indicated that "Structural Fires" should

1oThe EPA willbe revising the list ofevents contained in the AQS database following the promulgation ofthis ruleto ensure that the list is consistent with therequirements ofthe rule. generally not be considered exceptional
events..Commenters stated that these types ofevents shouldbe considered as emissions from anthropogenic sources and handled within the form ofthe respective air quality standards where a certain number ofexceedances 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 ofnonattainment. In cases where structural fires are determined to be the cause ofa monitored violation of the NAAQS, commenters stated that EPA should adopt a case-by-case review ofthese events.

Response:The definition ofstructural fires under this rule pertains to any accidental fire involving a manmade
structure. The EPA believes that structural fires couldbe an exceptional
event under this rule, provided all other requirements ofthe 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 activitythat are unlikely to recur at the same location. However, EPA agrees with the
commenters that these types ofevents,

as well as other similar types ofevents, 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 Dtieto 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 ofthe criteria andrequirements related to exceptional events are metas defined in thisrule. For example, States may flag, andEPA may exclude, data associated with fires occurring outside ofthe borders oftheijUnited 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 ofa pollutant in

an area, leading to exceedances or violations of a NAAQS. An example of interstate transported emissions which maybe flagged as due to an exceptional
event wouldbe emissions due to smoke from wildfires or wildland fire use fires which cause exceedances or violations ofthe 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

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

requirements related to an exceptional
event are met as defined in thisrule. In general, events due to transported pollution may be considered on a caseby-case basis.

CommentsandResponses

Comment:Several commenters expressed concern overEPA allowing the exceptional events rule to be usedto exclide 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 foran exceptional event as defined under thisrule, including requirements for causation and documentation. In cases where an area is impacted by emissions from sources outside of the United States which do
notmeet the criteria for an exceptional
event under thisrule, andthese emissions contribute to an area being designated as nonattainment, the emissions may be addressed under section 179B ofthe CAA related to "International Border Areas." Section 179B provides that where a State is required to submit aState Implementation Plan (SIP) to address issues related to anonattainment " designation, EPA may approve the SIP forthe area provided thatthe plan (1)
meets all the applicable requirements called for under the CAA, otherthan the requirement that the plan demonstrate attainment or maintenance ofthe NAAQS, and (2) the'SIP must demonstrate that the affected area wouldbe able to attain the standard by the applicable attainment date "but for" emissions emanating from outside the United States.

4. Exceedances Dueto aTerrorist Attack

Emissions that result from aterrorist attack such as smoke from fires, dust, explosions, power outages, train derailments, vehicular accidents, or combinatibns ofthese maybe flagged as

an exceptional event.

CommentsandResponses

No comments were received.on this topic.
5. Natural Events

The natural events addressed bythis' finalrule 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 ofnatural events on a case-by-case basis. a. Natural Disasters and Associated Clean-Up Activities

Forthe purpose offlagging, 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 areasonable timeperiod
to allow for.clean-up activities associated with thesetypes ofactivities. 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 ofthe 12-month timeperiod. The EPA will grant requests for extensions ofthe timeperiod related to such events on a case-by-case basis if the States submitadequate supporting information concerning the reason for the extension as well asthe length of time being requested for the extension.

CommentsandResponses

Comment:Several commenters indicated thatEPA should limit the time period associated with clean-up , activities due to anatural 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 ofthe CAA. For example, declaring an episode ofhigh

summer temperatures to be anatural disaster could potentially allow a State
to exclude high ozone levels which commonly occur during hotweather.

Response:Atime 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 reliefhas been granted, may be flagged for exclusion as exceptional events under this rule.The clean-up activities 

### associated wihths 4ypso eet
may also be flagged for exclusion as being due to an exceptional event. Given the nature ofa majornatural disaster, the 12-month timeperiod allowed forclean-up activities following such disaster is a reasonable time period, and is consistentwith the time period being allowed for volcanic and seismic activities under this rule. The period ofhigh 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 ofparticulate
matter for which volcanic or seismic activity caused or significantly contributed to high levels ofparticulate
matter in an affected area will be treated

as natural events. While generally not occurring frequently, volcanic and seismic activity can affect air quality datarelated tothe 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 ofparticulate matter due
to primary emissions (e.g., ash), and emissions ofprecursor pollutants (e.g., sulfur dioxide) thatcontribute to the secondary formation ofparticulate
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 ofthe NAAQS.

Comments andResponses

Comment:Several commenters indicated that the rule shouldprovide sufficient flexibility for datato be excluded where the duration ofthe
event may last for a longperiod oftime. An example of such anevent is where volcanic activities last forseveral days.

Response:The EPA agrees with the
commenters and notes that therule allows forStates to flag data andjubmit 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 formajor natural disasters, for clean-up activities following volcanic and seismic events. States are encouraged to submit supporting information related tothe

reasons forthe requested extension and the length oftime 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 orthrough the re-entrainment of material that has been deposited. In

some locations, concentrations ofcoarse particles like PM10 are most likely affected by these types ofevents, although PM2. 5 standards maybe exceeded under such circumstances as well. Section VII.B. also includes a discussion ofthis issue.

Comments andResponses

. Comment:Several commenters suggested that EPA replace the term 

### 13565

HeinOnline -- 72 Fed. Reg. 13565 2007

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

"high winds" with the term "windgenerated dust" because (1) itplaces 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 ofnatural
event that should be excluded under thisrule, as well as the action which caused the exceedance or violation of the standard. The term also serves as an indicator concerning the level ofwind which caused the exceedance or violation ofthe standard and indicates that it was unusually high for the affected area during the time period that the event occurred. Therefore, States
mustprovide appropriate documentation to substantiate why the level ofwind speed associated with the
event in question should be considered unusual for the affected area during the time ofyear 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 ofthe year that the
event is claimed.l

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 ontheir causal circumstances and therole that such fires play in the affected ecosystems. Prescribed fire is addressed more fully inthe following section.

The question ofwhat is a natural

versus an anthropogenic fire has particular significance when considering the impacts ofwildland fires (wildfire, wildland fire use fire and prescribed fire) on air quality and how these impacts shouldbe regarded under thisrule. A "wildfire" is defined as an unplanned, unwanted wildland fire

"As described elsewhere in the preamble, EPA is adopting aweight of evidence approach to demonstrate that an exceptional event caused an exceedance or violation. Therefore, in instances where the level ofthe wind speed results in exceedances orviolations ofparticulate matter, for data affected by these events to be considered for exclusion under the weight ofevidence 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 considerin the weight of evidence analysis winds that produce emissions contributed to by anthropogenic activities that have been controlled to the extent possible through use ofallreasonably available reasonable and appropriate measures. (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. Incontrast, a "wildland fire use" fire is the application ofthe appropriate management response to a naturallyignited (e.g., as theresult oflightning) wildland fire to accomplish specific

resource management objectives in predefined and designated areas where fire is necessary and outlined in fire management orland management plans.

Usingthese 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 awildland fire willbe considered fortreatment as an exceptional event ifthe fire is determined to be either a wildfire or wildland fire use fire.

Comments andResponses

Comment:Ingeneral, commenters strongly supported exempting wildfires

as exceptional events under the rule.

Response:The EPA acknowledges support forthe proposal to classify wildfires as apotential exceptional
event. As noted above, the Agency states that wildland fires will be excluded as exceptional events ifthey meet the criteria and requirements ofthe exceptional events rule.

Comment:The Agency received
comments both supporting and opposing the proposal allowing wildland fire use fires to qualify as an exceptional evefit.

Response:After reviewing Congress' revisions to section 319, the various Agency policies cited inthe proposal, and comments received, the Agency has deterntined that wildland fire use fires
may also qualify as an exceptional
event. However, these types offires
must also meet certain criteria. For example, these fires mustoccur on lands.thathave 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 tobegin revising thispolicy in 2007 as part ofits *overall Fire Strategy after promulgation of thisrule.

e. StratosphericOzoneIntrusions

Stratospheric ozone intrusion is considered to be anatural event. A stratospheric ozone intrusion occurs when a parcel ofair originating inthe stratosphere, which is at an average height of20 km or 12.4 miles, is transported directly to the surface ofthe 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.
CommentsandResponses

Comment:One commenter stated that EPA should update its approach to stratospheric events, establish criteria by which such events maybe determined, and credit States for the impact ofintrusion events on noncompliant ozone monitorreadings.

Response:Stratospheric ozone intrusion is identified as anatural event under 40 CFR part 50, appendix I, for
ozone, and willbe 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, priorto ignition a prescribed fire
musthave an approved prescribed fire plan andmust meet the National Environmental Policy Act (NEPA) requirements (where applicable)(see National Wildiand Fire Coordination Group Glossary ofWildland Fire Terminology, 2003). Forpurposes of section 319, a prescribed fire cannot be classified as "natural," giventhe extent ofthe 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 aparticular location" and is "not reasonably controllable orpreventable." The determination ofwhether a prescribed fire can be considered an exceptional
event showld be made on a case-by-case basistaking 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 andmimic fire under natural conditions. As such,

a prescribed fire's expected frequency

can vary widely, depending on the natural fire return interval ofa particular landscape or wildland ecosystem. The natural firereturn 

### 13566

HeinOnline -- 72 Fed. Reg. 13566 2007Federal Register/Vol. 72, No. 55/Thursday, March 22, 2007/Rules and Regulations

interval can range fromonce every year to less frequently than once inmore 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 ofthe statutory language.

A prescribed fire may also meet the condition of "not reasonably controllable or preventable" by examining whether there are reasonable alternatives tothe use offire inlight of the needs and objectives'to be served by it. For instance, there may be a significant build-up offorest fuels in a particular area that ifleftunaddressed would pose an unacceptable risk of catastrophic wildfire, which could result in adverse impacts ofmuch greater magnitude, duration, and severity than would result from careful

use ofprescribed fire. A particular ecosystem may alsobe highly dependent on a natural fire return interval tomaintain 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 arenot reasonably feasible forreasons that include, but are not limited to, a lack ofaccess, or severe topography, we believe that prescribed fire qualifies asbeing "not reasonably controllable orpreventable." Thus, we believe that a prescribed fire, conducted byFederal, State, Tribal or private wildland managers or owners, under the conditions described above may qualify

as an exceptional event.

In addition, one ofthe 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 ofthe source ofair pollution. We believe itreasonable to tie the qualifying criteria for an anthropogenically generated prescribed fire to State accountability forpublic health protection. Consistent with historical practice governed by the guidance contained in the "Interim Air Quality Policy on Wildland and Prescribed Tires," issued on May 15, 1998, EPA approval ofexceedances linked to aprescribed fire used for

resource management purposes is contingent onthe State certifying that it has adopted and is implementing a Smoke Management Program (SMP) as described in that policy.A State SWP establishes abasic framework of procedures andrequirements for managing smoke from a prescribed fire managed forresource benefits: A SMP is typically developed by a State orTrilje 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 ofthat approach. We also proposed to expand the criteria for contingent approval to a -prescribed fire where, in lieu ofa SMP, basic smoke management practic'es, that minimize emissions and control impacts, are being employed byburners. 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 bywhich a prescribed fire may qualify as an exceptional event. In those cases, the Agency willjudge on

a case-by-case basis whether the State has ensured that appropriate basic. smoke management practices havebeen employed in determining whether the prescribed fire qualifies as an exceptional event. Ifan exceptional
event occurs using the basic smoke management practices approach, the State must undertake a review oftheir approach to ensure public health is being protected and must include consideration of development ofa SMP.

Comments andResponses

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 ofcommenters also disapproved ofallowing prescribed fire
to be considered as an exceptional event because they believe that this type of

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 ofpeople at such receptors, identify steps taken to monitor the effects ofthe fire

on air quality, and identify procedures to ensure that burners areusing basic smoke management prictices. fire is anthropogenic and does not meet the statutory definition ofexceptional
event. Some commenters'also favored expanding the criteria for contingent approval to include instances where basic smoke management practices are used in lieu ofa SMP, while other
commenters did notfavor 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 inthis 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 ofthe rule including, among others, the schedules and procedures for flagging and demonstration are met. In those instances where aprescribed fire meets the criteria for an exceptional event, the State must also provide appropriate documentation to show thata certified SMP was inplace or thatthe burner employed basic smoke management practices and that the appropriate practices werebeing followed at the time that the event occurred. Because a prescribed fire is an anthropogenic

source ofemissions for purposes of section 319, even 'thoughit may qualify

as an exceptional event, a State can attempt to limit the health impact of a prescribed fire through the thoughtful development andimplementation of a SMP orensuring that basic smoke management practices were -employed that minimize emissions and control impacts from prescribed fires.

V. The Management ofAir Quality Data Affected byExceptional Events

TheEPA 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, ifan 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.' 3 For data exclusion, States must clearly identify, or "flag,"

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 ofa single AQS data point. The EPA encourages State submittalsto package demonstrations about single exceptional events to expedite the review
process. 

### 13567

HeinOnline -- 72 Fed. Reg. 13567 2007

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

data they believe to be influenced by such events. The demonstration to justify data exclusion shall provide evidence that: (a) The eventqualifies 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 thatis claimed tohave affected the airquality inthe 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 forthe
event.

The SAFE-TEA-LU requirements for exclusion ofdata from exceptional events are: (1) The occurrence ofthe exceptional event must be demonstrated byreliable 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 petitionEPA 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 ofdata as exceptional events that are determined tohave affected air quality, submittal ofdemonstrations to request data exclusion, public review, and the schedule and timing forthese 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 ofwhether 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 ofthe 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 ifthe agencyrequests 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 ifthe data do not qualify for exclusion. IfEPA

concurs on the exclusion ofdata from qualifying exceptional events, the data willbe excluded from regulatory consideration but will still count toward data capture requirements.

A. Flagging ofDatain theAQS Database

1. Background

Air quality data are required, pursuant to 40 CFR 58.15, tobe submitted to EPA by each State on a calendar quarterly basis, with submissions due not laterthan 90 days after the end ofa quarterly reporting period. Once air quality data havebeen submitted to EPA, it is possible to "flag" specific values forvarious purposes. "Data flagging" refers to the act of making anotation in a designated field of an electronic data record. The principal purpose ofthe data flagging system inthe 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 ofexceptional events, States place the initial flag on the data inthe AQS database. Following

an evaluation ofthe supporting documentation, EPA will decide whether to concur with the flag;

concurrence will be marked bythe placement of a second flag in the AQS database by EPA. Once EPA has concurred on the flag, the datawill be excluded from regulatory decisions such

as determinations ofattainment or nonattainnient."

a "While the flagging ofdata by the State is the first step in an exceptional
events demonstration, it is insufficient by itselfto 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 ofthe 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 ofexceptional events, States and Tribes place the initial flag

on the data inthe AQS database, but EPA determines the available flags.14 States may also delegate authority to

14ItisEPA's intention, for purposes of consistency withthis rule, to review the list of exceptional events that are currently inthe AQS database following the promulgation ofthe rule. local agencies to submit flags and documentation. In-any event, States should work with their local agencies for the identification andreview of exceptional events and consider requests to flag data from those agencies. At the time the flag is inserted into the AQS database, the Statemust also provide an initial description ofthe
event inthe AQS comment field.This initial description should include such information asthe direction and distance from the event to the air quality monitor in question, as well asthe direction ofthe wind on the day in question. The flags, andthe initial event description, mustbe inserted into the AQS database prior to July 1st following the year in whichthe event occurred. Schedules for demonstrations are discussed in section V.D.

Following an evaluation ofthe supporting documentation, EPA will make a decision concerning whether to

concur with the flag; concurrence will be marked bythe placement ofa second flag in the AQS database by EPA. IfEPA 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 ofthe data inthe 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 itselfto allow for the exclusion ofdata. 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 ofthe event inquestion, to demonstrate that the event qualifies as
an exceptional event in accordance with section IV.D, is consistent with EPA policies and guidance forcertain events

as described in section IV.E, has provided forpublic review in accordance with section V.G, and to document the causal connection between the measurement under consideration andthe event that is claimed to have affected the air quality in the area. The State, Tribe, or local agency must also demonstrate that the eventis associated with an unusual measured concentration beyond typical fluctuations including background, and that there would have been no exceedance orviolation "but for' the event. Because the initial step of 

### 13568

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

flagging the data is arelatively simple
one, States, Tribes, and local agencies may flag more days than the number of days for which they ultimately intend to submit demonstrations tojustify data exclusion.

3. Comments and Responses

Comment:One commentei supported flagging data related to any fire that caused an exceedance.

Response:This Rule does not preclude a State, Tribe, orLocal-agency from flagging any data allegedly influenced by exceptional events. However, forthe 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. WHatDoesItMeanforanEvent To "Affect AirQuality"?

1.Background

It isImportant to recognize that any emissions-producing event has the potential tohave some influence on downwind air quality. Indeed, on any given day, measured air quality at any given location will reflect the influences ofavariety ofactivities, including both natural and anthropogenic emissions from bothlocal as well asremote upwind sources. Given the directive in section 319(b)(3)(B)(ii), that a clear causal connection mustexist between the "measured exceedances" and the exceptional event, EPAbelieves that it wouldbe unreasonable to exclude data affected by an exceptional event simply because ofatrivial contribution ofan 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
uponwhich EPA's air quality standards

are based. The effect of such exclusion would be an inappropriate reduction in the stringency ofthe NAAQS, rather than providing specific reliefunder the circumstances provided in section 319 for which States should not be designated nonattainment orbe 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 forexclusion or special
treatment. However, section 319(b)(3)(B)(ii) and (iv)provides that there mustbe 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 mustbe shown that the data in question are "directly due" to an exceptional event. Moreover, one ofthe principles provided by section 319(b)(3)(A) indicates that the protection ofpublichealth is the highest priority. For these reasons, weproposed three conditions under which an event may qualify as "exceptional" for purposes of special regulatory consideration: Its air quality impactmust (1) fallboth above the level ofthe applicable standard (i.e., mustbe an "exceedance" as required by section 319), (2)be significantly beyond the normal fluctuating range ofair quality, including background air quality concentrations, and (3) should be large enough such thatwithout 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 ofthese approaches

was most suitable for demonstrating such impacts. These approaches primarily applied to condition (2) above. Two ofthe approaches involved statistical comparisons ofexisting flagged data. Thefinal 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 mustprovide ajustification that: (a)The
event qualifies in accordance with section IV.D. andif 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 includingbackground, and (d) there would have been no exceedance orviolation 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 anumber of methods includi.ng, 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 ofhistorical evidence.

The final rulepermits a case-by-case evaluation, without prescribed threshold criteria, to demonstrate that

an event affected air quality. This demonstration would bebased on the weight ofavailable evidence, but must consider thehistorical 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 tobest compare contemporary concentrations with the distribution ofhistorical values. For consistency with data reporting and computation ofNAAQS statistics, a calendar quarter basis is suggested. Baseline data may also be defined differently foreach 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 allmeasured data during the past several years is independent of historical flagging practices and allows States to accurately represent events not likely to recurby including all monitoring data inanalyses.

In addition, the magnitude ofthe measured concentration ondays affected by exceptional events relative
to historical,temporally adjusted air quality levels can guide the level of necessary analysis and documentation
to demonstrate thatthe 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 tojustify exclusion of data for regulatory purposes. This weight ofevidence approach is most nearly analogous to

our historical treatment ofexceptional
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 

### 13569

HeinOnline -- 72 Fed. Reg. 13569 2007

### 13570

. 

### Federal Register 

### /Vol. 72, No. 55 /Thursday, March 22, 2007 /Rules and. Regulations

* 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 itwilluse 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 mustbe associated with an unusual measured concentration beyond typical fluctuations including background. Demonstration ofthe magnitude ofthe measured concentrations with respect to historical frequency under similar conditions will provide a newlevel of consistency across monitoring locations.

Comment:Ifan area exceeds the NAAQS, one commenter stated that use of a 95th percentile criterion better

ensures that the definition ofan exceptional event is met (i.e., unlikely
torecur at aparticular location).

Response:The EPA recognizes that
extreme concentrations (e.g., corresponding to values greater than the 95th percentile ofhistorical 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 ofoccurrence relative to historical concentrations would be used

as an important part ofthe overall weight ofevidence to demonstrate the exceptional nature ofthe claimed air qualityimpact.

C. Useofa "ButFor"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 theresponsibilities of States to manage for purposes ofair quality attainment and maintenance. Forthis reason, we proposed to require that air quality data may not be excluded except where States show that exceedances or violations ofapplicable standards would not have occurred "but for" the influence ofexceptional 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 wouldbe above the level ofthe standards even withofit the influence of the exceptional event, the air quality data for the day(s) inquestion should
notbe excluded. However, consideration ofthe 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 maynot 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 forthe event [See sample "but-for" analysis in memo to docket, Husar et 01. 2006 (http:// www.regulations.gov,EPA-HQ-OAR2003-0061-0733 thru 0733.5)]. This analysis does not require aprecise estimate ofthe estimated air quality impact fromthe event. The weight of evidence demonstration can present a range ofpossible 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 thatcontributed to an exceedance or aviolation -thatare 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 ofsection 319. The short-term PM2.5 NAAQS isbased

on a 3-year average ofthe annual 98th percentile of 24-hour values. Therefore, itis possible that one ortwo of these annual concentration values may be below the level ofthe NAAQS whilethe 3-year average is above the level ofthe NAAQS. Because three annual q8th percentile concentration values are included inthe determination ofa short-term PM2.5 NAAQS violation, individual measurements below the NAAQS may contribute to a violation.

Onthe other hand, the annual PM2.5 NAAQSis also a standard based on a 3-
year average. However, violations ofthe annual standard that are caused by
measurements which are not exceedances of that standard will be difficult to distinguish fromtypical air quality concentrations including background. To accommodate the 3-year form ofthe PM2. 5 NAAQS, this rule will allow measurements whose concentrations are greater than the level ofthe annual NAAQS to be flagged as being affected by exceptional events for the purposes ofcontributing to an exceedance or violation ofthe 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 or24-hour NAAQS.
3. Comments and Responses

Comment:One commenter stated that, while some ofthose 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 ispossible that an event can affect multiple days. The "but for" provision allows for data exclusion ifbut 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 bythis rule and the air quality impact on each day are considered exceptional.

Comment:One commenter cautioned EPA about using thephrase "to the
extent itis possible to determine" because a "bright line" distinction between the contribution fromnatural and anthropogenic sources often does
not exist.

Response:We agree with this
comment and forthis reason we will

- permit a weight ofevidence-based

HeinOnline -- 72 Fed. Reg. 13570 2007

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

approach to demonstrate that there would nothave been an exceedance or violation but forthe event.

D.SchedulesandProcedures for Flagging andRequestingExclusionof Data

1. Background

In establishing procedures and time tables for States to request, andEPA to grant, exclusion ofdata 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 allpertinent and valid air quality data wouldbe appropriately considered in regulatory determinations. To assist EPA in determining the best approach to managing the data flagging process and submissions ofdemonstrations for the final rule, we proposed three alternatives for public review and commient. Public comments showed that each optionhad desirable aspects, and these are incorporated into the final rule.

2. Final Rule

A multi-step process will be established for identification ofdata and submission of demonstrations. The
process is designed to ensure that States,Tribes, and local agencies have adequate opportunity to compile and

- present evidence ofexceptional and natural events but also ensures timely submittals in order to make regulatorydecisions and ensure the protection of human health through NAAQS determinations. The steps include State flagging, annual State submission ofan initial event description, State submission ofa demonstration to justify data exclusion and EPA review followed by approval or disapproval. Where air quality in an areais 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 ofsources contributing to measured air quality concentrations are extremely complex and varied, making itmore difficult to distinguish between the effects of routine activities and unusual ones,
more time and effort willbe 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 datathat they believe to be affected by exceptional
events at the time ofsubmission ofthe 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 ofthe calendar quarter. This includes both flagging ofdata and insertion ofthe 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 ofdata. This approach would

ensure thatthe flagging process remains consistent with the timeline set forthin rules governing data submission requirements. The EPA recognizes that laboratory analyses may delay these submissions andtherefore is extending therequired 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 byJuly 1 ofthe following year).

We encourage States,Tribes, and local agencies to submit the demonstration to justify dataexclusion annually for exceedarices ofshort-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 tojustify data exclusion must be submitted within 3 years ofthe calendar quarter following

an event, but nolater than 12 months prior to aregulatory decision. This period shouldbe 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 letterrecommending the list ofnonattainment ares. 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 deshonstration to justify data exclusion

as well as the EPA responses and the rationale for the EPA decision willbe made'publicly available through EPA. The reason for providing the 3-year timeframe is that for ozone and PM, decisions regarding whether or notan

area is attaining the applicable standard

are based on the mostrecent 3 years of air quality data. Providing 3 years for submission ofdemonstrations would provide States, Tribes, and local agencies with an opportunity to evaluate whether the influence ofone or more exceptional events will be relevant
to determinations ofattainment or nonattainment before undertaking the effort ofpreparing and submitting demonstrations.

Once EPA receives a State's demonstration, EPA generally will undertake toreview the demonstration and provide aconcurrence or

nonconcurrence onthe flag in the AQS database within 60 days. The EPA expects that, in most cases, this time period shouldbe enough time toreview and provide aconcurrence ornonconcurrence related to a State's request to exclude data affected by an exceptional event. However, formore complex demonstrations, EPA may require additional time to make its decision and willnotify the State of the additional time required.

3. Comments andResponses

Comment:One commenter supported arguments on why the proposed rule
must include a procedure for retrospective flagging that addresses the full set ofthe State's needs so that the end result is that the Statecan flag any and all events impacted bynatural
events.

Response:With the Final Rule, EPA requires annual submittal offlags. States may, ifthey so choose, submitthem

sooner. This schedule ensures that data

are collected And retained shortly after the event and identification ofpotential (non-routine) events is done in atimely fashion to ensure that appropriate corrective actions canbe taken. States would only maintain minimal documentation supporting the decision
to flag the data. The full demonstrations, however, can come later, in orderto allow States timeto 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 toroutine natural events that are part ofbackground air quaity Comment:One commenter was concerned that a State may have failed
to flag data impacted by anatural 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 ofthis rule, States may include a demonstration tojustify 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 othercomments, for PM2.5 data collected during calendar years 2004- 2006, that the State identifies as resulting from an exceptional event, 13571

HeinOnline -- 72 Fed. Reg. 13571 2007

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

EPA is permitting the State to flag and submit an initial description ofthe
event provided that these are submitted

nolater than October 1, 2007. In cases where the State is able to show that this time period is inadequate, a Statemay submit arequest for an extension and EPA will grant this request foran 'extension up to but no laterthan 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 ofthe schedules for submittal ofdata for future revision ofstandards.

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 equired timeframes. Inthese
cases, the commenter asserted that EPA should provide some type ofpetitioning 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 ofdata should not be delayed oraltered based

on aState's failure to submit documentation or follow the regulatory procedures ina timely manner.
E.Exclusion of Entire24-HourValueas Opposedto aPartial Adjustment ofthe 24-HourValue

1.Background

In general, EPA's historical practice hasbeen to exclude a dailymeasured value in its entirety when Ian exceptional event causes thatvalue, and

we retained this approach in the proposed rule. With thisapproach, a determination is made that emissions from the event are largely responsible for the resultant ambient air pollutant concentration. For example, ifthe observed concentration is 200 gg/m 3 for PM2.5 and is associated with a nearby forest fire, thenEPA is likely toconcur with the claim that the event was responsible for the ambient concentration. The measured value wouldbe 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 wouldbe desirable to adjustthe daily value to exclude only those portions ofthe data that are attributable to the exceptional event in question, and toretain the remainder of the day's measurement ifappropriate and accurate methods were available to make such adjustments. For example, if an area affected by.awildfire had a measured 24-hour PM2. 5 concentration of50 pg/m 3 and the estimated event impact was 30 gg/m 3

,then the expected value that would have occurred but for the eventwould have been 20 gg/m3

. Normal air quality -forthis location mightbe 16 pg/m 3 and, therefore, the "but-for" concentration of20 pg/m 3 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 pg/m3). We

are currently seeking to develop and evaluate new analytical methods that. would allow usto discount onlythe portion ofthe daily value attributable to theexcdptional event. However, at present, we are not aware of the existence ofprecise and universally applicable techniques that are administratively and technically feasible and that could support partial adjustment ofair quality data except perhaps in limited cases, such as where the number and type ofpollutant 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 wedetermine that techniques foradjustment ofair quality data are sufficiently well-demonstrated for-usein exceptional events determinations, we will publish a notice ofproposed rulemaking to seek
comment onthe appropriateness and scope ofsuch use and its impact onthe requirements setforth in this rulefor determining an exceptional event.
2. Final Rule

We areretaining in this ruleEPA's historical practice to exclude a daily measured valuein its entirety when that value is found to becaused by a qualifying exceptional event that affected air quality in accordance With the conditions described in sections V.B and V.D. Ifprecise and universally applicable techniques that are administratively and technically feasible and that could support partial adjustment ofair quality data become available inthe future, EPA will, through a rulemaking, propose, and as appropriate, finalize atechnique for partial adjustment of data as well as any other matters inthis rule which maybe affected bythe availability ofthis technology.

One exception may be made to this exclusion ofthe 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 hourlj (but not sub-hourly).
measurements affected bythe intrusion may be excluded in orderto calculate the ozone measurements for the day. The individual hours are tobe excluded' however, iftheresulting calculated NAAQS averaging time value exceeds the level ofthe standard, notjust if the individual hourly values exceed that level. Thus, in the case ofozone, the resulting 8-hour average must exceed 0.08 ppm, and theresulting 24-hour average must exceed 15.0pg/m 3 for PM 25. 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 ifone halfthe 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 consideied valid when fewerthan eighteen valid hours are present if

zeroes can be-substituted forthe missing hours andtheresultant 24-hour value still exceeds 15.0 gg/m 3

. 3. Comments and Responses
Comment:One commenter supported value adjustment rather than exclusion when, and only when, such adjustment

can be accomplished bythe application ofvarious 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 ofthe 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. WhatShouldStatesBeRequiredTo Submitin Their ExceptionalEvents Demonstrations?
1. Background

.Section 319 requires that, in orderto have a flagged value excluded from regulatory determinations, a State must make an affirmative demonstration that

an event occurred (as shown byreliable 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 questionto 

### 13572

HeinOnline -- 72 Fed. Reg. 13572 2007Federal Register /Vol. 72, No. 55/Thursday, March 22, 2007/Rules and Regulations

."demonstratethatthe 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 ofthe 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 infact occurred and that emissions related to the eventwere transported in the direction ofthe monitor(s) where
measurements were recorded; the size of the area affected by the transported emissions; therelationship in time between the event, transport of emissions, and recorded concentrations; and, as appropriate, pollutant speciesspecific information supporting a causal relationship between the event andthe measured concentration. The latter information could be based on available data provided byroutine speciation, monitoring'networks, or from selective laboratory analysis ofarchived particulate matter filters for the day thoughtto be impacted by specific
events. In certain situations, such data mightbe useful forevaluation 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 timethat the event occurred, orafter 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 inpreparing their demonstrations:

9 Information demonstrating the

occurrence ofthe event and its subsequent transport to the affected monitors. This could include, for instance, documentation from land owners/managers, satellite-derived pixels (portions ofdigital images) indicating the presence offires; satellite images ofthe dispersing smoke and smoke plume transport ortrajectory calculations (calculationsto determine the direction oftransport ofpollutant emissions from theirpoint of origin) connecting fires with the receptors.

* Identification ofthe spatial pattern ofthe affected area (the size, shape, and

area ofgeographic coverage). This could include, for instance, the use of satellite

or surface measurement data.

* Information about temporal patterns (e.g., the time and duration ofan 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 ofthe chemical composition ofmeasured concentrations. This could include, for instance, organic or crustal material in

excess oftypically observed quantities
to differentiate from other high concentration events.

* High wind speeds relative to historically typical levels forthe season ofthe year in which the claimed event occurred.

This listis not exhaustive andnot all ofthese kinds ofinformation and/or documentation will need tobe provided in every instance. A particular instance may require more or less documentation, depending on the particular facts orcircumstances inthat instance. The simplest demonstrations could consist ofnewspaper 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 thatwildfires upwind ofthe San Diego area very likely caused high concentrations ofparticulate matter measured in October 2003based on the actual physical damage caused by fire to the ambientmonitor. Depending on the
nature ofthe event, meteorological conditions, severity and spatial extent of measured ambient concentrations (includingrelevant chemical components when available) relative to what typically occurs in the area, and

on emissions ofpollutants from the exceptional event which have similar characteristics to those ofother 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 andtopography, and where the emissions from the event in question
may well be similar tothose from other

sources contributing tomeasured concentrations, as compared to an area that has relatively few sources, simple terrain and less complex meteorology, andwhere emissions associated with the event are both substantially greater than and different incomposition from those of other nearby sources.
2.FinalRule

The demonstration tojustify data exclusion will address specific monitor readings reported to the AQS database. As stated inthe previous sections, a complete demonstration shalljustify 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 havebeen no exceedance or violation but forthe 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 varyby the type of
event and can be guided in partby the relative magnitude ofthe observed concentrations. To obtain concurrence, EPA must determine thatthe demonstration is complete and provides

a reasonable technical demonstration.

Because ofthe variability in the
nature ofexceptional events and the resulting demonstration requirements, States should consult with the appropriate EPA Regional Office early in the process ofpreparing their demonstrations. We are not specifying what willbe required as a minimum level ofdocumentation in all cases because facts and circumstances:will vary significantly based on, among other things, geography, meteorology and the relative complexity ofsource contributions to measured concentrations in any particular location. We believe, however, that at a minimum, the elements ofsuch 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 tothe monitor recording ahigh concentration of one or more criteria pollutants. Acceptable documentation -willbe determined through consultation with the EPA regional offices. However, certain minimum requirements (e.g., "but for" test)will be necessary as discussed inthe earlier sections ofthis rule. 

### 13573

HeinOnline -- 72 Fed. Reg. 13573 2007

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

3. Comments and Responses

Comment:In cases where high wind datacannot 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 causedby recurring anthropogenic

sources.

Response:TheEPA agrees that a weight ofevidence 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, ifthe flagged value does not impact a regulatory determination or ifmore detailed investigation indicates that the value may nothave been caused by an exceptional event after all. In these
cases, the agency should have the option to remove the flag.

Response:We agreethat the flag can be removed in these circumstances or left forinformational 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 ofdata.

Response:The EPA regional offices will work with the States, Tribes, and local agencies fo ensure thatproper documentation is submitted tojustify 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 donot 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 Availabilityof Air Quality DataandDemonstrations Relatedto ExceptionalEvents

1.Background

Section 40 CFR part 58.16 ofEPA's air quality monitoring rules state that all ambient air quality data and associated quality assurance data, including metadata records and information specified,bythe AQS Data Coding Manual epa.gov/ttn/airs/airsaqs/ manuals/manuals.htmmust 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 priorto the final demonstration being submitted to EPA for a decision concerning whether to exclude the datafrom regulatory consideration. Notice and availability ofsuch data and demonstrations mustbe 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 ofthe 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 shouldbe consistent with priorEPA 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 ofthe final ruleprovide sufficient time to engage the public.Not only does the final rulerequire that thepublic be accorded an opportunity to comment on the State's findings,but in some instances there willbe further opportunities forpublic review and
comment at the time that EPA proposes *tobase specific actions, e.g., approval,or disapproval ofSIP revisions. Thus, we do notbelieve that additional public review and comment provisions are necessary orappropriate.

VI. Additional Requirements

Pursuantto section 319, EPA is finalizing this ruleto address data that has been influenced by exceptional events. Also, EPA is finalizing one.of four options put forth in the proposed ruleto address the issue ofwhether, 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 ofthe

source ofair 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 forStates ToProvide Public Notification,PublicEducation, andAppropriateandReasonable MeasuresToProtect PublicHealth

1. Background

The EPA proposed one approach and took comments onthree alternative options concerning what actions a State should take inanticipation of, or in response to, the occurrence ofan exceptional event. The options that

were proposed ranged from being very detailed and prescriptive to being very flexible andless prescriptive in terms of the actions that States should take to mitigate the impact ofan exceptional
event on the public. While EPA does not believe that section 319(b)(3)(A) explicitly requires, in and ofitself,that States must develop mitigating

measures or plans, EPAsolicited
comment inthe proposed rule on whether this subparagraph.supports the

use ofother legal authority to require mitigating actions orplans when an exceptional event occurs, and solicited
comment onissues 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 incases where exceedances of aNAAQS are caused by

an exceptional event, once a State. becomes aware that an exceptional event is occurring, is predicted to occur,-
orhas occurred, the State must take reasonable and appropriate actions to:

e Provide notice to the public ofthe event. This may include, but is not limited to,using the media to alert the public ofthe event.

e Provide public education concerning the potential health risks associated with being exposed to high ambient concentrations ofpollutant(s) related tothe event. This may include, but is not limited to, providing information to sensitive populations related to the healthrisks associated with the event.

e Take appropriate and reasonable

measures to abate orminimize the exposure ofthe public to high 

### 13574

HeinOnline -- 72 Fed. Reg. 13574 2007Federal Register/Vol. 72, No. 55/Thursday, March 22, 2007/Rules and Regulations

concentrations ofair pollution associated with the exceptional event. This may include, but is not limitedto, taking reasonable and appropriate actions to implement control measures

on significant contributing anthropogenic sources toreduce potential'exposure ofthe 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, inthe case of volcanic or seismic activity,this may include, but is not limited to, prdiriding 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 apart ofits demonstration, appropriate documentation to show that the State provided public notice and public education concerning the event in question, andthat the State took reasonable and appropriate measures to abate orminimize the exposure ofthe public to the emissions from the event, where appropriate.

Option 2 in the proposed rule provided that, States arerequired to adopt a general mitigation plan to address exceptional events before the

occurrence of an event as a part ofthe State's SIP required under section 110(a)(1) ofthe CAA. Section 110(a)(1) requires States to adopt and submit to EPA, within 3 years following the promulgation ofa new or revised NAAQS, a planwhich provides for the implementation, maintenance, and enforcement of the standard in each air quality region within the State. Under this option, States wouldbe required to develop and adopt the general requirements and procedures necessary for the implementation ofa mitigation plan to address exceptional events as a part ofits 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 totake reasonable and appropriate measures to mitigate the public health impacts ofan 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 inresponse to

aspecific event that affects the air quality ofa 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) ofthe CAA which would contain the general provisions ofa mitigation plan in advance ofthe

occurrence ofany exceptional event. Under option 3,the mitigation plan would only be developed by the State following the occurrence ofan exceptional event forwhich the State requested exclusion ofthe air quality data, and would notbe submitted as a part ofthe SIP. The mitigation plan wouldbe 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 ofplans developed under Option 2 above, including therequirements to notify the public that an event is expected to
occur, or is occurring, or has occurred,
to provide forpublic education related
to the health effects associated with the event, and to identify the actions that would be taken bythe State to mitigate the impact ofany recurrence ofthe
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 forEPA to exclude data from regulatory consideration. This approach proposed to allow States to have the maximum degree of flexibility in determining what actions shouldbe taken tomitigate 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 notbe 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 ofthe SIP such

as those contained in Option 2, or to develop a more formal plan with requirements not a part ofthe SIP such

as those contained in Option 3.

2. Final Rule

The EPA is adopting a modified version ofOption 1 from the proposed rule, as described above. This option does notrequire States to submit formal mitigation plans; however, States must provide public notice, public education, and mustprovide forimplementation of reasonable measures to protectpublic health when an event occurs.
3. Comments andResponses

Comment:Several commenters supported option I because they stated that itprovides more flexibility for States to determine the appropriate

measures to be implemented related to the occurrence ofan exceptional event. Other commenters supported option 1 for well defined, well understood events that are non-recurring or unlikely to

recur. The majority ofthe 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 statedthat issues concerning exceptional events should be dealt with outside the SIP process and section 110 ofthe 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 tomitigate the poor air quality impacts associated with exceptional events. The
commenter stated that BACM, not RACM, must be implemented on all contributing anthropogenic sources relatedto an exceptional event. Several
commenters supported option 3 for addressing public health impacts related
torecurring natural events. The
commenters stated that mitigation plans should include BACM for contributing anthropogenic sources, notRACM. The majority ofcommenters who commented on option 4.stated thatthey supported the implementation ofoption 4 because itallows States the most flexibility fordeveloping and tailoring.
programs for public notification of exceptional events, the implementation ofeducation programs on exceptional events, and implementation of reasonable measures to protect public health.

Response:States have an inherent responsibility toprotect its citizens and

as such to provide appropriate and reasonable actions to mitigate the impact ofexceptional events onthe public health. This includes alerting the public when such events occur, .providingpublic education concerning thehealth effects of such events, and implementing reasonable measures to mitigate the impact ofsuch events on public health. Consistent with this inherent responsibility, it is EPA's belief that States are in abetter position to make decisions concerning what actions should be taken to protect the public when an exceptional event occurs. This 

### 13575

HeinOnline -- 72 Fed. Reg. 13575 2007Federal Register/Vol. 72, No. 55/Thursday, March 22, 2007/Rules and Regulations

being the case, States should havethe necessary flexibility to take appropriate actions when exceptional events occur. The EPA is adopting a modified version ofits 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 ofits citizens, and are capable of making the determinations ofwhat actions shbuld 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 ittook to mitigate the impact of exceptional events, in order forEPA 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 thatis required. The EPA believes that this" modified option 1provides 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 SAFETEA-LU, does not specifically provide that States must implement mitigation plans, in developing the exceptional
events rule, EPA is requiredto consider the enumerated principles including the principle that States must take necessary measures to protect public health regardless ofthe source ofair pollution. Therefore, under the modified version ofoption 1 adopted in this final rule, States musttake reasonable and appropriate actions to protect public health.

Comment:Several commenters stated that the exceptional events rule should be consistent with the current -requirementsunder existing policies withrespect to the need for a NEAP to address recurring natural events such as high wind events.

Response:TheEPA 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 ashigh wind events. However, following the promulgation of this rule, States will no longer be required to keep NEAPs in place thatwere not approved as a part ofa SIP foran area. Where a NEAP, as well as BACM, has been approved as a part ofa nonattainment SIP for an area, the NEAP, as well asthe associated BACM, must remain inplace. States may, however, submit arequest to EPA
toremove the NEAP and BACM from the SIP. The request must contain an approvable demonstration, as required by section 110(1), which shows that the removal of theNEAP and BACM will
not interfere with any applicable requirement concerning attainment or maintenance ofthe NAAQS foran area, reasonable further progress, or any other applicable requirement for the area.
VII. Special Treatment ofCertain 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 asubset of exceptional events) at air quality monitoring sites where ithas 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 ofnatural 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 fromnational and international sources that otherwise
meets the criteria and requirements for exceptional events. Some types of exceptional events have unusual characteristics thatrequire special consideration in the context ofthis final rulemaking. We discuss each ofthese special issues, and the necessary accommodations, below.

A. VolcanicandSeismicActivities

1. Background

Volcanic and seismic activities may affect air quality for an extended period oftime after theinitial occurrence ofthe
event in question. Therefore, EPA believes that it is appropriate to consider an extended timefrane for flagging and exclusion ofdata 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 activit4r during the firstyear (12 months) following an event willbe 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 forthe clean-up of ash deposits due to volcanic/seismic events. During that timeperiod, emissions ofreentrained dust due to anthropogenic activities associated with cleanup may be treated as exceptional events. In

cases where the damage caused bythe 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 ofthe 12-month time period to EPA. As stated elsewhere inthis 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 forthe extension and the length oftimebeing reqiested for the extension.

B. High WindEvents

1.Background

Where high wind events result in exceedances or violations ofthe particulate matter standards, EPA proposed that they be treated as natural events ifthere is aclear causal relationship demonstrated between the exceedances measured at the air quality monitoring site andthe high wind event in question, and ifanthropogenic activities which contribute to particulate matter emissions in conjunction with the high wind event

are reasonably well-controlled.

2. FinalRule

The EPA's final rule concerning high wind events states that ambient particulate matter concentrations due to dust beingraised 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 withinthe 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 tohave contributed to exceedances orviolations due to highwind events at air quality monitoring sites, per our decision in thisrulemaking concerning the action that States must take to mitigate the impact ofexceptional events on public 

### 13576

HeinOnline -- 72 Fed. Reg. 13576 2007Federal Register /Vol. 72, No. 55/Thursday, March 22, 2007 /Rules aid Regulations

health (See section VI above), States
musttake reasonable and appropriate

measures to mitigate the impact associated with the event on publiq 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 ormay not include the implementation ofcontrols on contributing anthropogenic sources relatedto an event. However, where anthropogenic sources have contributed
to the exceedances ofthe PM NAAQS at

an air quality monitoring site due to a high wind event, a State musttake reasonable and appropriate measures to protect public health.

Since the conditions that cause or contribute to high wind events vary from area to areawith soil type, precipitation, andthe speed ofwind gusts, States should provide appropriate documentation which indicates what types ofcircumstances contributed to the exceedances orviolations at the monitoring site inquestion. 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 aparticular event shouldbe considered exceptional for theaffected

area. The EPA will review the documentation submitted by States concerning high wind events and will make decisions concerning whether to exclude the data asbeing influenced by

15 Section 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 ora lack ofprecipitation; or (iii) air pollution relating to source noncompliance." In
terms ofthe exclusion related to "a meteorological
event involving high temperatures or a lack of precipitation" EPA believes that this statutory language prohibits EPAfrom treating a typical dry day(s) or a dry season for an area as an exceptional

event. However, EPAbelieves that Congress did not intenud 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 ofdata ondays characterized by "high temperature and a lack ofprecipitation." Therefore, EPA is permitting States to submit documentation which shows that "severe drought" conditions may have contributed to the occurrence ofahigh wind
event. The documentation must, however, be compelling enough to show that the conditions present at thetime of theevent were more substantial than.atypical dry day(s) or dry season forthe area in question, butwere related to severe drought conditions. The EPA willreview this information and make decisions concerning the exclusion ofthe data related to the event on a caseby-case basis. an exceptional eventon a case-by-case basis.

C.StratosphericOzoneIntrusion.

1. Background

Consideration of stratospheric ozone intrusions applies only to the 8-hour

ozone standard. The occurrence ofsuch intrusions are extremely difficult to

measure or document given currently measured meteorological parameters and the locations ofthese
measurements. The infrequency, short durations, andlocalized nature of such
events makes it difficult touse currently available, general meteorological data, which are usually collected atisolated 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 forthe purpose of flagging data, and other non-exceptional meteorological events. Although-data have been identified inthe past showing the result ofstratospheric ozone intrusion, no standard definition or criteria have been established for
concrete identification. Therefore, EPA's determination ofwhether a stratospheric ozone intrusion has occurred is a case-by-case decision based onreasonable judgment considering the season ofthe year, time ofday, persistence, duration, type and severity ofaccompanying meteorological conditions associated with the ozone measurement in question, and otherdata showing that conditions were not conducive to local high ozone production but forthis intrusion.

2. Final Rule

The EPA is finalizing its rule as proposed. The EPA's determination of whether a stratospheric ozone intrusion has occurred willbe made on acase-bycase basis based on reasonablejudgment considering the criteria as noted above. Itis our intention toreview this type of exceptional event during the next review ofthe NAAQS forozone. A review ofhistorical data related to the flagging ofstratospheric ozone intrusion

as an exceptional event shows that the
event hal only been flagged on afew isolated occasions.

VIII.Treatment ofFireworks Displays

A. Background

The EPA proposed to treat emissions due to fireworks displays in amanner similar to exceptional events. Some national and/or cultural traditions, such

asJuly 4thIndependence 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 arenot aware ofany information showing adverse air quality impacts caused by individual use offireworks in relatively small quantities. However, analyses ofmonitoring data collected on July 4th andJuly 5th indicates that large fireworks displays, in combination with other sources, can in some circumstances be potentially significant

sources ofairpollutant emissions. For this reason, States are encouraged to take reasonable precautions to minimize exposures to emissions from fireworks displays, to explore the use oflower emitting fireworks, as well as tomanage associated activities thatmay also have significant air quality impacts inthe

areas where these events are held. Such precautions may include alerting the public tothe potential for short-term air quality impacts that may resultfrom the discharge offireworks at large displays, monitoring prevailing winds, and locating displays downwind of concentrations ofpeople. Forthese
reasons, where States can show that the

use offireworks 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 thisrule.

B. Final Rule
The EPA is finalizing the approach as stated in the proposed rule to treat emissions from fireworks similar to the
treatment ofexceptional events inthe final rule provided that the event meets the other criteria as stated inthis rulemaking. For example, the event must be determined to have affected air quality. Where a State can show that the

use offireworks is significantly integral
to traditional national, ethnic, orother cultural events (e.g., July Fourth celebrations, Chinese New Year celebrations, Diwali, etc.), EPA will exclude data fromregulatory determinations for monitoring stations whose exceedances orviolations has been determined to be causedby emissions from fireworks displays on a case-by-case basis. As stated in other parts oftherule, .Statesmust assure that reasonable measures were taken to protect the public fromthe emissions created bythe fireworks display. Under this rule, States are also strongly encouraged toinstitute educational
programs that alert the publicto the 

### I.13577

HeinOnline -- 72 Fed. Reg. 13577 2007

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

health effects associated with exposure to emissions from fireworks displays.

C.Comments andResponses

Comment:The majority of
commenters who commented on this issue agreed that emissions from fireworks shouldbe 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 notmake provisions for fireworks to be excluded

as an exceptional event.

Response:In considering the intent of the SAFETEA-LU legislation, itis EPA's beliefthat Congress did not intend to prohibit the exclusion ofdata affected by emissions from fireworks related to celebrations ofnational or cultural traditions. Itis EPA's beliefthat data influenced by fireworks displays should be subjectto the same provisions as other exceptional events identified under this rule. Therefore, the mitigation actions described in sebtion VI.A above would also apply to emissions related to fireworks displays.

IX.Statutory andExecutive Order Reviews

A. Executive Order12866:Regulatory PlanningandReview

Under Executive Order 12866 (58 FR 51735, October 4, 1993), this action is a significant regulatory action because it raises novel legal orpolicy issues arising out oflegal mandates. Accordingly, EPA submitted this action
to the Office ofManagement and Budget (OMB) forreview under Executive Order 12866 and any changes made in response to 0MB recommendations have been documented in the docket for this action.

B.Paperwork ReductionAct
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 tojustify data that has been flagged asbeing affected by exceptional ornatural events. However, the OMB has previously approved the information collection requirements regulations forambient air monitoring contained in40 CFR part 58,-subparts A through E, under the provisions ofthe Paperwork Reduction Act, 44 U.S.C. 3501 etseq. and assigned OMB control number 2060-0084, EPA ICR number 940.17. A cOly ofthe OMB approved Information Collection Request (ICR) maybe obtained from Susan Auby, Collection Strategies Division; U.S. Environmental Protection Agency (2822T); 1200 Pennsylvania Ave., NW., Washington, DC 20460 orby calling (202) 566-1672.

Burden means that total time, effort,

or financial resources expended by persons to generate, maintain, retain, or disclose orprovide information to or for

a Federal agency. This includes the time needed toreview instructions; develop, acquire, install, and utilizetechnology 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 torespond 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 notrequired to respond to a collection ofinformation unless it displays a currently valid OMB control number. The OMB control numbers.for EPA'sregulations inthe CFRare listed in 40 CFR part 9.

C.Regulatory Flexibility Act
I. 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 orany other statute unless the EPA certifies that therule will nothave a significant economic impact on a substantial number ofsmall entities. Small entities include smallbusinesses, small organizations, and small governmental jurisdictions. Forthe purpose of assessing the impacts ofthis final rule

on small entities, small entityis defined

as: (1)A small business as defined by the Small Business Administration's regulations at 13 CFR 121.2.01; (2) a small governmental jurisdiction that is a government of a city,county, town, school district or special district with a population ofless 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 RFAto require aregulatory flexibility analysis only when small entities willbe subject to the requirements ofthe rule. See, Michiganv.EPA, 213 F.3d 663, 668-69 (DCCir., 2000), cert.den., 532 U.S. 903 (2001). This rule would notestablish 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 asbeing influenced by an exceptional ornatural
event. The rule alsoprovides information concerning what action. shouldbe taken by a State, local, or Tribal air quality agency toprotect 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 ofthe rule on small entities.

After considering the economic impacts ofthis final rule on small entities, I certify that this rule will not have a significant economic impact on
a substantial number ofsmall entities.

D. UnfundedMandatesReformAct

Title II ofthe 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 andthe private
sector. Under section 202 ofthe UMRA, EPA generally must prepare a written statement, including a cost-benefit analysis, for proposed and final rules with "Federal mandates" that may resultin expenditures to State governments, inthe aggregate, orto the -privatesector, of$100 million or more inany 1year. Before promulgating an EPA rule for which a written statement is needed, section 205 ofthe UMRA generally requires EPA to identify and 'considera 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 ifthe Administrator publishes with the final rule an explanation ofwhy that alternative was not adopted. Before EPA establishes any regulatory requirements that may significantly or uniquely affect small governments, including Tribal governments, itmust have developed under section 203 ofthe UMRA a small government agency plan. The plan 'must provide for notifying potentially affected small governments to have meaningful and timely input in the 

### 13518

HeinOnline -- 72 Fed. Reg. 13578 2007Federal Register/Vol. 72, No. 55/Thursday, March 22, 2007/Rules and Regulations

development ofEPA 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 resultin expenditures of$100 million or more for State, local, and Tribal governments, in the aggregate, or the private sector in any 1year. This action simplyprovides 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 bfsections 202, 203, and 205 ofthe UMRA.

E.Executive Order13132:Federalism

Executive Order 13132, entitled "Federalism" (64 FR 43255, August 10, 1999),requires EPA to develop an accountable process to ensure "meaningful and timely inputby State and local officials in the development of regulatory policies thathave federalism implications." "Policies that have federalism implications" is defined in the Executive Order to include regulations that have "substantial direct effects on the States, orthe relationship between the national government and the States, or onthe distribution of
power and responsibilities among the various levels ofgovernment."

This final rule does nothave federalism implications. It willnot have substantial direct effects on the States,

on the relationship between the national government and the States, oron the distribution ofpower and responsibilities among the various levels ofgovernment, 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 thisrule.

F.ExecutiveOrder13175:Consultation andCoordinationWith IndianTribal Governments

Executive Order 13175, entitled "Consultation and Coordination with Indian Tribal Governments" (65 FR 67249, November 9, ?000), requires EPA
to develop an accountable process to

ensure "meaningful andtimely inputby Tribal officials inthe development of regulatory policies that have Tribal implications." This final rule does not have "Tribal implications" as specified inExecutive Order 13175. The rule provides information concerning what action should be taken by a State, local,

orTribal.air quality agency implementing.relevant air quality
programs toprotect public health once EPA has provided aconcurrence 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 ofthe Tribe whether to develop these programs and which programs, or appropriate elements ofa 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 atthis time. Furthermore, this rule does notaffect the relationship or distribution ofpower and responsibilities between the Federal government and Indian Tribes. The CAA and the TAR establish the relationship ofthe 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 thoughwe found that this rule does not have Tribal implications, we nevertheless were

aware ofTribes thathad an interest in this rule. Therefore, We conducted communications and outreach related to therule 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 Order13045:Protectionof ChildrenFromEnvironmental Health andSafetyRisks

Executive Order13045: "Protection of Children From Environmental Health anqd SafetyRisks" (62 FR 19885, April 23, 1997) applies to any rule that (1)is determined to be "economically significant" as defined underExecutive Order 12866, and (2) concerns an environmental health and safetyrisk 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 ofthe planned rule on children, and explain why the planned regulation is preferable to other potentially effective and reasonably

- feasible alternatives considered byEPA.

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 nothave 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 ait quality
agency to protect public health once EPA has provided a concurrence on data that has been flagged asbeing influenced by an.exceptional or natural
event.

H. ExecutiveOrder13211:Actions That Significantly Affect EnergySupply, Distribution, or Use
This ruleis not a "significant energy action" as defined inExecutive Order 13211, "Actions That Significantly Affect Energy Supply, Distribution, or Use," (66 FR 28355, May 22, 2001) because it is not likel to have a significant adverse effect onthe supply, distribution, oruse ofenergy. Further,

we have concluded thatthis rule is not likely to have any adverse energy effects.

L NationalTechnology Transfer AdvancementAct

Section 12(d) ofthe National Technology TransferAdvancement 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) thatare developed or adopted byVCS bodies. The NTTAA directs EPA to provide Congress, through OMB, explanations when EPA decides notto use available and applicable VCS.

This action does not involve technical standards. Therefore, EPA did not consider the use of anyVCS.

J. Congressional ReviewAct
The Congressinnal Review Act, 5 U.S.C. 801 etseq., as added by the Small Business Regulatory Enforcement Fairness Act of1996, generally provides thatbefore a rule may take effect, the agencypromulgating the rule must 'submit arule report, which includes a copy of the rule, to each House ofthe Congress and to the Comptroller General ofthe 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 ofthe United States prior to publication of the rule in the Federal 

### 13579

HeinOnline -- 72 Fed. Reg. 13579 2007

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

Register. A major rule cannot take effect until 60 days after itis 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 forJudicial Review
Under section 307(b)(1) ofthe CAA, petitions forjudicial review of this action mustbe filed inthe United States Court ofAppeals forthe District of Columbia Circuit by May 21, 2007. Filing a petitioi for reconsideration by the Administrator ofthis final rule does not affect the finality ofthis rule for the purposes ofjudicial review nor does it extend the time within which a petition forjudicial review must be filed, and shall not postpone the effectiveness of such rule oraction. This action may not be challenged later in proceedings to enforce its requirements. See CAA Section 307(b)(2).

List ofSubjects

40 CFRPart 50
Environmental protection, Air pollution control, National parks, Wilderness areas.
40 CFRPart 51
Environmental protection, Air pollution control, Administrative practice and procedure, Reporting and recordkeeping requirements.

Dated: March 14, 2007. Stephen L. Johnson, Administrator.

mInconsideration ofthe foregoing, the Environmental Protection Agency amends 40 CFRparts 50 and 51 as follows:

PART 50-NATIONAL PRIMARY AND SECONDARY AMBIENT AIR QUALITY
STANDARDS

0 1.Theauthority citation forpart 50 continues to read as follows:

Authority: 42 U.S.C. 7401 etseq.
* 2. Amend §50.1 to add paragraphs (j) and (k)to read as follows:
§50.1 Definitions.

(j)Exceptionaleventmeans an event that affects air quality, is not reasonably controllable or preventable, is an event caused by human activity that isunlikely to recur ata 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 ormeteorological inversions, a meteorological event involving high temperatures or lack ofprecipitation, or air pollution relating to source noncompliance.

(k)Naturalevent means an event in which human activity plays little or no direct causal role.

(1)Exceedancewith respecttoa nationalambientair qualitystandard

means one occurrence of ameasured or modeled concentration that exceeds the specified concentration level ofsuch standard for the averaging period specified by the standard.

* 3. Add §50.14 toread as follows:
§50.14 Treatment of air qualitymonitoring data Influenced byexceptional events.

(a) Requirements.(1) A State may request EPA to exclude data showing exceedances or violations ofthe national ambient air quality standard that are directly due to an exceptional event fromuse in determinations by demonstrating to EPA's satisfaction that such event -causeda specific air pollution concentration at a particular air quality monitoring location.

(2) Demonstration tojustify data exclusion may include any reliable and
accurate data, but must demonstrate a clear causal relationship between the measured exceedance orviolation of such standard and the event in accordance with paragraph (c)(3](iii) of this section. (b) Determinations byEPA. (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 ormore national ambient air quality

- standards at a particular air quality

monitoring location and otherwise satisfies the requirements ofthis section.

- (2) EPA shall exclude data from use in determinations ofexceedances and NAAQS violations where a-State demonstrates to EPA's satisfaction that emissions from fireworks displays caused a specific air pollutionconcenttation in excess ofone drmore national ambient air quality standards at

a particular air quality monitoring location and otherwise satisfies the requirements ofthis section. Such data willbe treated in the same manner as exceptional events under thisrule, provided a State demonstrates that such.

use of fireworks is significantly integral totraditional national, ethnic, or other cultural events including, but not limited to July Fourth celebrations which satisfy the requirements ofthis section.

(3) EPA shall exclude data from use in determinations ofexceedances and NAAQS violations, where a State demonstrates to EPA's satisfaction that emissions from prescribed fires caused

a specific air pollution concentration in

excess ofone 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), andprovided that the State has certified toEPA that ithas adopted and is implementing a Smoke Management Program or the State has ensured that theburner employed basic smoke management practices. If an exceptional
event occurs using the basic smoke management practices approach, the State must undertake a review ofits approach to ensure publichealth is being protected and must include consideration ofdevelopment ofa SMP. (4) [Reserved]

- (c) SchedulesandProcedures.(1) Public notification. (i) All States and, where applicable, their political subdivisions must notify the public promptly whenever an event

occurs or isreasonably anticipated to

occur which mayresult in the exceedance ofan applicable air quality standard.

(ii) [Reserved.] (2) Flagging ofdata. (i) A State shall notify EPA of its intent to exclude one or more measured exceedances ofan applicable ambient air quality standard asbeing due to an exceptional eventby placing a flag in the appropriate field for the data record ofconcern in accordance with the schedules for submission ofdata 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 respectto exceedances or violations ofthe national ambient air quality standards unless and until, following the State's submittal ofits 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 ofthe event shallbe submitted to EPA not later than July 1st ofthe calendar year following the year in which the flagged measurement occurred, except asalloWed under paragraph (c)(2)(iv) ofthis section.

(iv) For PM2. 5 data collected during calendar years 2004-2006, that the State identifies as resulting from an 

### 13580

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

exceptional event, the State must notify EPA of the flag and submit an initial description ofthe event no later than October 1, 2007. EPA may grant an extension, ifa State requests an extension, and permit the State o submit the notification ofthe flag and initial description byno later than December 1, 2007.

(v) When EPA sets aNAAQS for a

new pollutant, or revises the NAAQS for

an existing pollutant, it mayrevise or set anew schedule for flagging data for the initial designation ofareas forthose NAAQS.

(3) Submissionof demonstrations. (i) A State that has flagged data as being due to an exceptional event and is requesting exclusion ofthe affected
measurement data shall, after notice and opportunity for public comment, submit

a demonstratioh to justify data exclusion to EPA not later thanthe lesser of, 3years 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 submitthe public
comments itreceived along with its demonstration to EPA.

-

(ii)A State that flags data collected during calendar years 2004-2006, pursuant to paragraph (c)(2)(iv) ofthis section,must adopt the procedures and requirements specified in paragraph (c)(3)(i) of this section and must include

a demonstration tojustify the exclusion ofthe data not later than the submittal ofthe Governor's recommendation letter

onnonattainment areas.

(iii)The demonstration tojustify data exclusion shall provide evidence that:

(A) The event satisfies the criteria set forth in40 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 ofthe 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

I 4. The authority citation forpart51 continues toread as follows: Authority: 23 U.S.C. 101; 42 U.S.C. 7401- 7671q.

* 5.Adding SubpartY 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 andreasonable actions to protect public health from exceedances orviolations ofthe 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 ofair 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]

BILUNG CODE 6560-50-P 

### 13581

HeinOnline -- 72 Fed. Reg. 13581 2007