[Federal Register Volume 80, Number 224 (Friday, November 20, 2015)]
[Proposed Rules]
[Pages 72840-72897]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2015-29350]
[[Page 72839]]
Vol. 80
Friday,
No. 224
November 20, 2015
Part III
Environmental Protection Agency
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40 CFR Part 50
Treatment of Data Influenced by Exceptional Events; Proposed Rule
Federal Register / Vol. 80 , No. 224 / Friday, November 20, 2015 /
Proposed Rules
[[Page 72840]]
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ENVIRONMENTAL PROTECTION AGENCY
40 CFR Part 50
[EPA-HQ-OAR-2013-0572, EPA-HQ-OAR-2015-0229; FRL-9935-73-OAR]
RIN 2060-AS02
Treatment of Data Influenced by Exceptional Events
AGENCY: Environmental Protection Agency (EPA).
ACTION: Proposed rule; notice of availability of related draft
guidance; notice of hearing.
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SUMMARY: The Environmental Protection Agency (EPA) is proposing
revisions to certain sections within the regulations that govern the
exclusion of event-affected air quality data from regulatory decisions.
The EPA is also providing a notice of availability of a draft version
of the non-binding guidance document titled Draft Guidance on the
Preparation of Exceptional Events Demonstrations for Wildfire Events
that May Influence Ozone Concentrations.
DATES: Comments. Written comments on this proposal and draft guidance
must be received by January 19, 2016.
Public hearing: The EPA will hold a public hearing on this proposal
on Tuesday, December 8, 2015, in Phoenix, Arizona. Please refer to
SUPPLEMENTARY INFORMATION for additional information on the comment
period and public hearing.
ADDRESSES: Submit your comments on the EPA's proposed revisions to 40
CFR part 50, identified by Docket ID No. EPA-HQ-OAR-2013-0572, at
http://www.regulations.gov. Follow the online instructions for
submitting comments. Once submitted, comments cannot be edited or
removed from Regulations.gov. The EPA may publish any comment received
to its public docket. Do not submit electronically any information you
consider to be Confidential Business Information (CBI) or other
information whose disclosure is restricted by statute. Multimedia
submissions (audio, video, etc.) must be accompanied by a written
comment. The written comment is considered the official comment and
should include discussion of all points you wish to make. The EPA will
generally not consider comments or comment contents located outside of
the primary submission (i.e., on the Web, Cloud or other file sharing
system). For additional submission methods, the full EPA public comment
policy, information about CBI or multimedia submissions and general
guidance on making effective comments, please visit http://www2.epa.gov/dockets/commenting-epa-dockets.
Submit your comments on the EPA's Draft Guidance on the Preparation
of Exceptional Events Demonstrations for Wildfire Events that May
Influence Ozone Concentrations, identified by Docket ID No. EPA-HQ-OAR-
2015-0229, at http://www.regulations.gov. Follow the online
instructions for submitting comments. Once submitted, comments cannot
be edited or removed from Regulations.gov. The EPA may publish any
comment received to its public docket. Do not submit electronically any
information you consider to be CBI or other information whose
disclosure is restricted by statute. Multimedia submissions (audio,
video, etc.) must be accompanied by a written comment. The written
comment is considered the official comment and should include
discussion of all points you wish to make. The EPA will generally not
consider comments or comment contents located outside of the primary
submission (i.e., on the web, cloud or other file sharing system). For
additional submission methods, the full EPA public comment policy,
information about CBI or multimedia submissions and general guidance on
making effective comments, please visit http://www2.epa.gov/dockets/commenting-epa-dockets.
Public hearing: A public hearing will be held on Tuesday, December
8, 2015, in room 3175 in the Arizona Department of Environmental
Quality main office building located at 1110 W. Washington Street,
Phoenix, Arizona 85007. The public hearing will convene at 10 a.m. and
continue until the earlier of 6 p.m. or 1 hour after the last
registered speaker has spoken. We have scheduled a lunch break from
12:30 p.m. until 2 p.m. People interested in presenting oral testimony
should contact Ms. Pamela Long, Air Quality Planning Division, Office
of Air Quality Planning and Standards (C504-01), U.S. Environmental
Protection Agency, Research Triangle Park, NC 27711, telephone (919)
541-0641, fax number (919) 541-5509, email address [email protected], at
least 2 days in advance of the public hearing (see DATES). People
interested in attending the public hearing should also call Ms. Long to
verify the time, date and location of the hearing.
FOR FURTHER INFORMATION CONTACT: For additional information regarding
this proposed rule, please contact: Beth W. Palma, U.S. EPA, Office of
Air Quality Planning and Standards, Air Quality Policy Division, Mail
Code C539-04, Research Triangle Park, NC 27711, telephone (919) 541-
5432, email at [email protected]. For additional information
regarding the Draft Guidance on the Preparation of Exceptional Events
Demonstrations for Wildfire Events that May Influence Ozone
Concentrations, please contact Melinda Beaver, U.S. EPA, Office of Air
Quality Planning and Standards, Air Quality Policy Division, Mail Code
C539-04, Research Triangle Park, NC 27711, telephone (919) 541-1062,
email at [email protected]. For information on the public hearing
or to register to speak at the hearing, contact Ms. Pamela Long, U.S.
Environmental Protection Agency, Office of Air Quality Planning and
Standards, Air Quality Planning Division, Mail Code C504-01, Research
Triangle Park, NC 27711, telephone (919) 541-0641, fax number (919)
541-5509, email at [email protected] (preferred method for registering).
SUPPLEMENTARY INFORMATION:
I. General Information
A. Does this action apply to me?
Entities potentially directly affected by this proposal and the
draft guidance document include all state air agencies and any local
air quality agency to whom a state has delegated relevant
responsibilities for air quality management, including air quality
monitoring and data analysis. Tribal air agencies operating ambient air
quality monitors that produce regulatory data may also be directly
affected. Entities potentially affected indirectly by this proposal and
the draft guidance document include federal land managers (FLMs) of
Class I areas, other federal agencies and other entities that operate
ambient air quality monitors and submit collected data to the EPA's Air
Quality System (AQS) database.
B. What should I consider as I prepare my comments for the EPA?
1. Docket. The EPA has established one docket for the proposed
revisions to the 2007 Exceptional Events Rule and another docket for
the draft guidance document. All documents in these dockets are listed
on the http://www.regulations.gov Web site in the respective docket.
The rulemaking docket is Docket ID No. EPA-HQ-OAR-2013-0572. The
separate docket established for the Draft Guidance on the Preparation
of Exceptional Events Demonstrations for Wildfire Events that May
Influence Ozone Concentrations is Docket No. EPA-HQ-OAR-2015-0229. The
EPA will not respond to comments relating to the guidance document as
[[Page 72841]]
part of this rulemaking, but will consider these comments in the
development of the final guidance document. If comments on the draft
guidance document are submitted to the rulemaking docket, the EPA will
respond only to the portion of such comments that are relevant to the
rulemaking. The EPA also relies on the documents in Docket ID No. EPA-
HQ-OAR-2011-0887, the docket established for the July 2012 notice of
availability for the Draft Exceptional Events Implementation Guidance,
and incorporates this docket into the record for this action. However,
no new comments may be directed to Docket ID No. EPA-HQ-OAR-2011-0887
and the EPA will not respond to comments that have already been
submitted to this docket unless they are resubmitted to Docket ID No.
EPA-HQ-OAR-2013-0572. Although listed in the indices to the rulemaking
docket and the guidance docket associated with this action (i.e.,
Docket ID No. EPA-HQ-OAR-2013-0572 and Docket No. EPA-HQ-OAR-2015-
0229), some information is not publicly available, (e.g., CBI or other
information whose disclosure is restricted by statute). Certain other
material, such as copyrighted material, will not be placed on the
Internet but may be viewed, with prior arrangement, at the EPA Docket
Center. Publicly available docket materials are available either
electronically in www.regulations.gov or in hard copy at the Air and
Radiation Docket and Information Center, EPA/DC, EPA William Jefferson
Clinton West Building, Room 3334, 1301 Constitution Avenue NW.,
Washington, DC. The Public Reading Room is open from 8:30 a.m. to 4:30
p.m., Monday through Friday, excluding legal holidays. The telephone
number for the Public Reading Room is (202) 566-1744 and the telephone
number for the Air and Radiation Docket and Information Center is (202)
566-1742. For additional information about the EPA's public docket,
visit the EPA Docket Center homepage at: http://www.epa.gov/epahome/dockets.htm.
2. Submitting CBI. Do not submit this information to the EPA
through http://www.regulations.gov or email. Clearly mark the part or
all of the information that you claim to be CBI. For CBI information in
a disk or CD-ROM that you mail to the EPA, mark the outside of the disk
or CD-ROM as CBI and then identify electronically within the disk or
CD-ROM the specific information that is claimed as CBI. In addition to
one complete version of the comment that includes information claimed
as CBI, a copy of the comment that does not contain the information
claimed as CBI must be submitted for inclusion in the public docket.
Information so marked will not be disclosed except in accordance with
procedures set forth in 40 CFR part 2.
3. Tips for Preparing Your Comments. When submitting comments,
remember to:
Identify the rulemaking and/or draft guidance document by
docket number and other identifying information (subject heading,
Federal Register date, page number and guidance document title, if
applicable).
Follow directions--The agency may ask you to respond to
specific questions or organize comments by referencing a Code of
Federal Regulations (CFR) part or section number in the guidance.
Explain why you agree or disagree; suggest alternatives
and substitute language for your requested changes.
Describe any assumptions and provide any technical
information and/or data that you used.
If you estimate potential costs or burdens, explain how
you arrived at your estimate in sufficient detail to allow for it to be
reproduced.
Provide specific examples to illustrate your concerns, and
suggest alternatives.
Explain your views as clearly as possible, avoiding the
use of profanity or personal threats.
Make sure to submit your comments by the identified
comment period deadline.
C. Where can I get a copy of these documents and other related
information?
In addition to being available in the docket, an electronic copy of
this notice and the draft guidance will be posted at http://www2.epa.gov/air-quality-analysis/treatment-data-influenced-exceptional-events.
D. What should I know about the public hearing?
The EPA intends to hold a public hearing on Tuesday, December 8,
2015, in room 3175 in the Arizona Department of Environmental Quality
main office building located at 1110 W. Washington Street, Phoenix,
Arizona 85007. If you would like to attend or speak at the public
hearing, please contact Ms. Pamela Long, U.S. Environmental Protection
Agency, Office of Air Quality Planning and Standards, Air Quality
Planning Division, Mail Code C504-01, Research Triangle Park, NC 27711,
telephone (919) 541-0641, fax number (919) 541-5509, email at
[email protected] (preferred method for registering) at least 2 days in
advance of the public hearing (see DATES). Interested parties may
submit oral and/or written comments. Interested parties do not need to
attend the public hearing to submit written comments. Additional
details concerning any public hearing for this proposed rule will be
posted on the EPA's Web site for this rulemaking at http://www2.epa.gov/air-quality-analysis/treatment-data-influenced-exceptional-events.
The public hearing will provide interested parties the opportunity
to present data, views or arguments concerning the proposed revisions
to the 2007 Exceptional Events Rule. The EPA will make every effort to
accommodate all speakers who arrive and register. Individuals planning
to attend the hearing will be required to sign in, and may be required
to show valid picture identification to the security staff to gain
access to the meeting room. In addition, no weapons will be allowed in
the facility. Any weapons brought to the site will be stored in a
locker at the facility. No large signs will be allowed in the building,
and cameras may only be used outside of the building. The EPA may ask
clarifying questions during the oral presentations but will not respond
to the presentations at that time. Written statements and supporting
information submitted during the comment period will be considered with
the same weight as oral comments and supporting information presented
at the public hearing. Commenters must submit written comments on the
proposed rule and/or draft guidance by January 19, 2016. Commenters
should notify Ms. Long if they will need specific equipment, or if
there are other special needs related to providing comments at the
hearing. The EPA will provide equipment for commenters to show overhead
slides or make computerized slide presentations if we receive special
requests in advance. Oral testimony will be limited to 5 minutes for
each commenter. The EPA encourages commenters to provide the EPA with a
copy of their oral testimony electronically (via email or CD) or in
hard copy form. The hearing schedule, including the list of speakers,
will be posted on the EPA's Web site at http://www2.epa.gov/air-quality-analysis/treatment-data-influenced-exceptional-events. Verbatim
transcripts of the hearing and written statements will be included in
the docket for the rulemaking. The EPA will make every effort to follow
the schedule as closely as possible on the day of the hearing; however,
please plan for the hearing to
[[Page 72842]]
run either ahead of schedule or behind schedule.
E. How is this document organized?
The information presented in this document is organized as follows:
I. General Information
A. Does this action apply to me?
B. What should I consider as I prepare my comments for the EPA?
C. Where can I get a copy of these documents and other related
information?
D. What should I know about the public hearing?
E. How is this document organized?
II. Glossary of Terms and Acronyms
III. Executive Summary
IV. Background for Proposal
A. Purpose of and Statutory Authority for This Regulatory Action
B. The 2007 Exceptional Events Rule
C. Early Experience in Implementing the 2007 Exceptional Events
Rule
D. The EPA's Interim Exceptional Events Implementation Guidance
E. More Recent Implementation Experience Including EPA-
Recommended Best Practices for the Development of Exceptional Events
Demonstrations
V. Proposed Rule Revisions
A. To whom and to what pollutants does the Exceptional Events
Rule apply?
1. Current Situation
2. Proposed Changes
B. What is an exceptional event?
1. Current Situation
2. Proposed Changes
C. What types of ambient concentration data and data uses may be
affected by the Exceptional Events Rule?
1. Current Situation
2. Proposed Changes
D. What is a natural event?
1. Current Situation
2. Proposed Changes
E. Technical Criteria for the Exclusion of Data Affected by
Events
1. Human Activity Unlikely To Recur at a Particular Location or
a Natural Event
2. Not Reasonably Controllable or Preventable
3. Clear Causal Relationship Supported by a Comparison to
Historical Concentration Data
F. Treatment of Certain Events Under the Exceptional Events Rule
1. Exceedances Due to Transported Pollution
2. Wildland Fires
3. Stratospheric Ozone Intrusions
4. High Wind Dust Events
G. Other Aspects of Flagging Exceptional Events-Influenced Data
and Demonstration Submittal and Review
1. Who may submit a demonstration and request for data
exclusion?
2. Aggregation of Events for NAAQS With Periods Longer Than 24
Hours and Demonstrations With Respect to Multiple NAAQS for the Same
Pollutant
3. Exclusion of Entire 24-Hour Value Versus Partial Adjustment
of the 24-Hour Value for Particulate Matter
4. Flagging of Data
5. Initial Notification of Potential Exceptional Event
6. Submission of Demonstrations
7. Timing of the EPA's Review of Submitted Demonstrations
8. Dispute Resolution Mechanisms
VI. Mitigation
A. Current Situation
B. Proposed Changes
1. Defining Historically Documented or Known Seasonal Events
2. Mitigation Plan Components
3. Options for Implementing Mitigation Plans
VII. Draft Guidance on the Preparation of Exceptional Events
Demonstrations for Wildfire Events That May Influence Ozone
Concentrations
A. What is this draft guidance about and why is it needed?
B. What scenarios are addressed in the draft guidance?
VIII. Environmental Justice Considerations
IX. Statutory and Executive Order Reviews
A. Executive Order 12866: Regulatory Planning and Review and
Executive Order 13563: Improving Regulation and Regulatory Review
B. Paperwork Reduction Act
C. Regulatory Flexibility Act
D. Unfunded Mandates Reform Act
E. Executive Order 13132: Federalism
F. Executive Order 13175: Consultation and Coordination With
Indian Tribal Governments
G. Executive Order 13045: Protection of Children From
Environmental Health & Safety Risks
H. Executive Order 13211: Actions Concerning Regulations That
Significantly Affect Energy Supply, Distribution or Use
I. National Technology Transfer and Advancement Act
J. Executive Order 12898: Federal Actions To Address
Environmental Justice in Minority Populations and Low-Income
Populations
X. Statutory Authority
II. Glossary of Terms and Acronyms
The following are abbreviations of terms used in the preamble.
AQCR Air Quality Control Region
AQS Air Quality System
Be Beryllium
BACM Best available control measures
BLM Bureau of Land Management
BMP Best management practice(s)
BSMP Basic smoke management practices
CAA Clean Air Act
CASTNET Clean Air Status and Trends Network
CBI Confidential business information
CFR Code of Federal Regulations
CO Carbon monoxide
EPA Environmental Protection Agency
FLM Federal land manager responsible for management of a federally
owned area that has been designated a Class I area as codified in 40
CFR part 81, subpart D
FR Federal Register
IPV Isentropic potential vorticity
Lidar A remote sensing technology that measures distance by
illuminating a target with a laser and analyzing the reflected light
[mu]g/m\3\ Micrograms per cubic meter
mph Miles per hour
NAAQS National ambient air quality standard or standards
NAM North American Mesoscale Forecast System
NASA National Aeronautics and Space Administration
NEPA National Environmental Policy Act
NO2 Nitrogen dioxide
NOAA National Oceanic and Atmospheric Administration
NOV Notice of violation
NOx Nitrogen oxides
NPS National Park Service
NSR New source review
NRCS Natural Resources Conservation Service
NRDC Natural Resources Defense Council
NWCG National Wildfire Coordinating Group
NWS National Weather Service
OAQPS Office of Air Quality Planning and Standards, U.S. EPA
OMB Office of Management and Budget
Pb Lead
PM Particulate matter
PM10 Particulate matter with a nominal mean aerodynamic
diameter less than or equal to 10 micrometers
PM2.5 Particulate matter with a nominal mean aerodynamic
diameter less than or equal to 2.5 micrometers
ppb Parts per billion
PSD Prevention of significant deterioration
PT Potential temperature
RACM Reasonably available control measures
RAQMS Real-time Air Quality Modeling System
RUC Rapid Update Cycle
SIP State implementation plan
SMP Smoke management program
SO2 Sulfur dioxide
TAR Tribal Authority Rule
TIP Tribal implementation plan
UMRA Unfunded Mandates Reform Act
USDA U.S. Department of Agriculture
USFS U.S. Forest Service
VOC Volatile organic compound or compounds
III. Executive Summary
This section summarizes the purpose of this regulatory action, the
major provisions of this action, and the development of associated
guidance.
Purpose of This Regulatory Action
Recognizing that it may not be appropriate for the EPA to use
certain monitoring data collected by the ambient air quality monitoring
network and maintained in the air quality data system (AQS) in the
EPA's regulatory determinations, in 2005 Congress provided the
statutory authority for the exclusion of data in specific situations by
adding section 319(b) to the Clean Air Act (CAA). The EPA promulgated
the 2007 Exceptional Events Rule (March 22, 2007, 72 FR 13560) to
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implement this 2005 amendment of the CAA. The purpose of this action is
to propose revisions to the 2007 Exceptional Events Rule to address
certain substantive issues raised by state, local and tribal co-
regulators and other stakeholders since promulgation of the rule and to
increase the administrative efficiency of the Exceptional Events Rule
criteria and process. The EPA intends to promulgate these rule
revisions in advance of the date by which states, and any tribes that
wish to do so, are required to submit their initial designation
recommendations for the revised 2015 ozone NAAQS (expected in October
of 2016). In addition, the EPA intends to address a 2008 D.C. Circuit
Court decision in which the court found that certain preamble language
was ``legally null'' because there was no associated implementing rule
language.
Interpreting and implementing the 2007 Exceptional Events Rule has
been challenging in certain respects both for the air agencies
developing exceptional events demonstrations and for the EPA Regional
offices reviewing and acting on these demonstrations. Since 2007, air
agencies have submitted exceptional event demonstrations for a variety
of pollutant and event combinations ranging from volcanic activity
influencing sulfur dioxide (SO2) and particulate matter (PM)
concentrations to stratospheric ozone intrusions. Air agencies
preparing demonstrations have expressed specific concerns and
identified challenges associated with preparing analyses to satisfy the
``but for'' rule criterion, determining what controls constitute
reasonable controls particularly for natural sources and for interstate
and international transport and identifying how much documentation to
include in a demonstration.
As a result of both our experiences and feedback related to
implementing the 2007 Exceptional Events Rule received from state,
local and tribal co-regulators and other stakeholders via letters and
numerous conference calls and meetings, the EPA developed and released
Interim Exceptional Events Implementation Guidance in May of 2013. This
guidance has addressed some of the concerns and challenges raised by
interested parties, has helped reduce the burden of preparing
demonstrations and has reduced the time needed for review. However, the
EPA acknowledged that additional changes could only be accomplished
through a notice-and-comment rulemaking. Therefore, when the EPA
released the Interim Exceptional Events Implementation Guidance in May
of 2013, we simultaneously announced our intent to pursue revisions to
the Exceptional Events Rule. These changes are reflected in this
proposed action.
Concurrent with preparing this proposed action, the EPA held
conference calls with some air agencies to discuss more recent
implementation experiences and to better understand currently employed
exceptional events implementation processes and practices. As a result
of these discussions, the EPA developed a list of best practices for
communication and collaboration between the EPA and air agencies.
Agencies using these approaches have developed a common understanding
of expectations, terminology and interpretation of the EPA's
regulations and policy, which, in turn, helps focus efforts, optimize
resources and save time during the demonstration development and review
process.
Based on our experiences and the input we have received from our
collaborations with interested parties (including state, local and
tribal air agencies) following the promulgation of the 2007 Exceptional
Events Rule and since the development of the Interim Exceptional Events
Implementation Guidance and based on the previous legal challenge, we
have determined those aspects of the 2007 Exceptional Events Rule that
most need to be addressed in this proposed action.
Summary of Major Provisions
For the first time, the EPA proposes to interpret CAA section
319(b) as applying to only a specific set of regulatory actions (e.g.,
designations) because we believe that the criteria and process steps
specified in the CAA were not clearly intended by Congress to apply to
all types of regulatory actions and in some cases certain of the
criteria and steps are not appropriate. We address this concept in this
document in general terms, but we also intend to develop a separate
guidance document to provide guidance on when data can be excluded and
when they cannot for other specific types of regulatory actions.
The EPA proposes to return to the core statutory elements and
implicit concepts of CAA section 319(b): The event affected air quality
in such a way that there exists a clear causal relationship between the
specific event and the monitored exceedance or violation, the event was
not reasonably controllable or preventable and the event was caused by
human activity that is unlikely to recur at a particular location or
was a natural event. Within each of these elements, we are proposing
clarifications regarding the desired analyses to include in exceptional
events demonstrations and we discuss the applicability of these
clarifications to certain event types or categories. As part of this
return to the core statutory elements, we are proposing to remove from
the Exceptional Events Rule a paragraph containing what is commonly
referred to as the ``but for'' criterion.
The EPA is proposing to incorporate the statutory ``affects air
quality'' criterion and the regulatory ``historical fluctuations''
criterion within the ``clear causal relationship'' element. We believe
that if an air agency demonstrates that an event has a clear causal
relationship to an exceedance or violation of a NAAQS, then the event
has certainly affected air quality and that a submitting air agency
does not need to address ``affects air quality'' as a distinct
component. As we indicated in the Interim Exceptional Events
Implementation Guidance (see section IV.D), we believe that a
comparison of the claimed event-influenced concentration(s) to
concentrations at the same monitoring site at other times is extremely
useful evidence in an exceptional events demonstration, particularly as
part of showing a clear causal relationship, and we propose to continue
requiring this type of comparison. This proposed action details the
minimum set of statistical analyses that the EPA expects to see in
demonstrations.
With respect to the ``not reasonably controllable or preventable''
criterion, many states have requested that the EPA automatically
consider an event to be reasonably controlled if the EPA has approved a
state implementation plan (SIP) that contains controls for
anthropogenic sources that contribute to the event that are also
specific to the pollutant of concern in the exceptional events
demonstration. In response, the EPA proposes that enforceable control
measures implemented in accordance with an attainment or maintenance
SIP, approved by the EPA within 5 years of the date of a demonstration
submittal, that address the event-related pollutant and all sources
necessary to fulfill the requirements of the CAA for the SIP to be
reasonable controls with respect to all anthropogenic sources that have
or may have contributed to event-related emissions. Also for this
criterion, the EPA clarifies that air agencies generally have no
obligation to specifically address controls if the event was natural or
if it was due to emissions originating outside their jurisdictional
(i.e., state or tribal) border(s).
With respect to the ``human activity that is unlikely to recur at a
particular
[[Page 72844]]
location or was a natural event'' criterion, we propose a general
approach to determining whether the recurrence frequency of an event is
``unlikely to recur at a particular location'' and an approach
applicable to prescribed fire on wildland only. We also clarify that
natural events can recur, sometimes frequently, and reiterate our
belief that we generally consider human activity to have played little
or no direct role in causing emissions if anthropogenic emission
sources that contribute to the event emissions are reasonably
controlled at the time of the event.
Air agencies must address all of the core statutory elements and
implicit concepts of CAA section 319(b) within an exceptional events
demonstration. In this proposed action, the EPA clarifies the content
and organization of exceptional events submittals to include the core
statutory elements, but we also propose that states be required to
include a conceptual model, or narrative, describing the event(s)
causing the exceedance or violation and a discussion of how emissions
from the event(s) led to the exceedance at the affected monitor(s) and
documentation that the air agency conducted a public comment process.
We are proposing to require an initial notification by the state to the
EPA of a potential exceptional event as a preliminary step before
submitting a demonstration, to ensure the submitting air agency and the
reviewing EPA Regional office share a common understanding regarding
the potential event and are in communication regarding the timeline for
the demonstration to be submitted and to be reviewed by the Regional
office.
Because affected air agencies have provided feedback regarding the
difficulty associated with meeting the current regulatory timelines
associated with data flagging, initial event descriptions and
demonstration submittals, the EPA proposes to remove the specific
deadlines that apply in situations other than initial area designations
following promulgation of a new or revised NAAQS. Also associated with
demonstration timing, the EPA proposes to officially terminate review
of demonstrations that, due to the passage of time, will have no
further regulatory significance specifically for the five types of
regulatory actions identified in section V.C. of this preamble.
Since promulgation of the 2007 Exceptional Events Rule,
stakeholders have raised numerous questions about fire-related
components that were discussed, but not fully defined or clarified in
the preamble to the 2007 Exceptional Events Rule. This proposed action
addresses fire-related definitions, provides more clarity regarding
expectations for smoke management programs (SMPs) and basic smoke
management practices (BSMP), and proposes limited scenarios under which
FLMs and other federal agencies may prepare and submit exceptional
events demonstrations and data exclusion requests directly to the EPA.
Associated Guidance Documents
In addition to proposing revisions to the 2007 Exceptional Events
Rule, this proposed action simultaneously provides a notice of
availability of a draft non-binding guidance document titled, Draft
Guidance on the Preparation of Exceptional Events Demonstrations for
Wildfire Events that May Influence Ozone Concentrations, which applies
the proposed Exceptional Events Rule revisions to wildfire/ozone
events. This guidance document is intended to further address specific
stakeholder questions regarding the Exceptional Events Rule and further
increase the efficiency of rule implementation. In addition, the EPA is
currently developing a guidance document titled, Draft Guidance for
Excluding Some Ambient Pollutant Concentration Data from Certain
Calculations and Analyses for Purposes Other than Retrospective
Determinations of Attainment of the NAAQS, which will apply to the
exclusion of certain data for certain applications using a process and
criteria outside of the Exceptional Events Rule. The EPA intends to
make this guidance document available shortly after proposing revisions
to the Exceptional Events Rule. The EPA expects to finalize these
guidance documents concurrently with promulgating revisions to the
Exceptional Events Rule.
IV. Background for Proposal
A. Purpose of and Statutory Authority for This Regulatory Action
Part of the EPA's mission is to preserve and improve, when needed,
the quality of our nation's ambient air to protect human health and the
environment. As part of accomplishing this, the EPA develops the
national ambient air quality standards (NAAQS) for criteria pollutants
and oversees the states' programs to improve air quality in areas where
the current air quality is unacceptable and to prevent deterioration in
areas where the air quality meets or exceeds the NAAQS. The EPA then
evaluates the status of the ambient air as compared to these NAAQS by
using data collected in the national ambient air quality monitoring
network established under the authority of section 319(a) of the CAA.
Recognizing that it may not be appropriate for the EPA to use
certain monitoring data collected by the ambient air quality monitoring
network and maintained in AQS in our regulatory determinations, in 2005
Congress provided the statutory authority for the exclusion of data in
specific situations by adding section 319(b) to the CAA in 2005. The
EPA promulgated the 2007 Exceptional Events Rule (March 22, 2007, 72 FR
13560) to implement this 2005 amendment of the CAA. The purpose of this
action is to propose revisions to the 2007 Exceptional Events Rule to
address certain issues raised by stakeholders since promulgation of the
rule and to increase the administrative efficiency of the Exceptional
Events Rule criteria and process.
In addition to proposing revisions to the 2007 Exceptional Events
Rule, we are simultaneously providing a notice of availability of a
draft non-binding guidance document titled, Draft Guidance on the
Preparation of Exceptional Events Demonstrations for Wildfire Events
that May Influence Ozone Concentrations, which applies the proposed
Exceptional Events Rule revisions to wildfire/ozone events. We seek
comment on whether the concepts in this guidance document should be
finalized as rule text. We are also currently developing a second
guidance document titled, Draft Guidance for Excluding Some Ambient
Pollutant Concentration Data from Certain Calculations and Analyses for
Purposes Other than Retrospective Determinations of Attainment of the
NAAQS, which will apply to the exclusion of certain data for certain
applications using a process and criteria outside of the Exceptional
Events Rule. Both of these draft guidance documents are intended to
further address specific stakeholder concerns regarding the Exceptional
Events Rule and further increase the efficiency of rule implementation.
B. The 2007 Exceptional Events Rule
The 2007 Exceptional Events Rule created a regulatory process
codified at 40 CFR parts 50 and 51 (sections 50.1, 50.14 and 51.930).
These regulatory sections contain definitions, procedural requirements,
requirements for air agency demonstrations, criteria for the EPA's
approval of the exclusion of event-affected air quality data from the
data set used for regulatory decisions,
[[Page 72845]]
and requirements for air agencies \1\ to take appropriate and
reasonable actions to protect public health from exceedances or
violations of the NAAQS.\2\ The 2007 Exceptional Events Rule superseded
the EPA's previous natural events guidance and those sections of an
earlier guidance document that addressed the treatment of data affected
by exceptional events.\3\
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\1\ References to ``air agencies'' are meant to include state,
local and tribal air agencies responsible for implementing the
Exceptional Events Rule. The regulatory text in the 2007 Exceptional
Events Rule often uses ``State'' to apply to ``air agencies.'' In
the context of flagging data and preparing and submitting
demonstrations, the role of and options available to air agencies
would also apply to federal land managers of Class I areas and other
federal agencies managing federal land.
\2\ Per the definition at 40 CFR 50.1(l), an exceedance with
respect to a national ambient air quality standard means one
occurrence of a measured or modeled concentration that exceeds the
specified concentration level of such standard for the averaging
period specified by the standard. Violations of a standard are
standard-specific and are determined by applying the standard-
specific procedures for air quality data handling identified in the
appendices to 40 CFR part 50. For example, per the requirements in
40 CFR part 50, appendix N, an exceedance of the 2006 24-hour
PM2.5 NAAQS of 35 [mu]g/m\3\ occurs when the 24-hour
concentration is above 35 [mu]g/m\3\ on a single day. A violation of
the 2006 24-hour PM2.5 NAAQS occurs when the 3-year
average of the annual 98th percentile 24-hour concentrations is
above 35 [mu]g/m\3\.
\3\ Previous guidance and policy documents that either implied
or stated the need for special treatment of data affected by an
exceptional event include:
i) Guideline for the Interpretation of Air Quality Standards,
U.S. EPA, OAQPS No. 1.2-008, Revised February 1977. Available at
http://nepis.epa.gov/Exe/ZyNET.exe/2000YFDB.TXT?ZyActionD=ZyDocument&Client=EPA&Index=1976+Thru+1980&Docs=&Query=&Time=&EndTime=&SearchMethod=1&TocRestrict=n&Toc=&TocEntry=&QField=&QFieldYear=&QFieldMonth=&QFieldDay=&IntQFieldOp=0&ExtQFieldOp=0&XmlQuery=&File=D%3A%5Czyfiles%5CIndex%20Data%5C76thru80%5CTxt%5C00000007%5C2000YFDB.txt&User=ANONYMOUS&Password=anonymous&SortMethod=h%7C-&MaximumDocuments=1&FuzzyDegree=0&ImageQuality=r75g8/r75g8/x150y150g16/i425&Display=p%7Cf&DefSeekPage=x&SearchBack=ZyActionL&Back=ZyActionS&BackDesc=Results%20page&MaximumPages=1&ZyEntry=1&SeekPage=x&ZyPURL.
ii) Guideline on the Identification and Use of Air Quality Data
Affected by Exceptional Events (the Exceptional Events Policy), U.S.
EPA, OAQPS, EPA-450/4-86-007, July 1986.
iii) Areas Affected by PM-10 Natural Events (the PM10
Natural Events Policy), memorandum from Mary D. Nichols, Assistant
Administrator for Air and Radiation, to EPA Regional Offices, May
30, 1996. Available at http://www.epa.gov/ttn/caaa/t1/memoranda/nepol.pdf.
iv) Interim Air Quality Policy on Wildland and Prescribed Fires.
U.S. EPA. April 23, 1998. Available at http://www.epa.gov/ttn/oarpg/t1/memoranda/firefnl.pdf.
v) Guideline on Data Handling Conventions for the PM NAAQS. U.S.
EPA, OAQPS, EPA-454/R-98-017, December 1998.
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In general, the exceptional events regulatory process consists of
the following steps. First, an air agency identifies a potential event-
related exceedance or violation. After noting these data in AQS, the
air agency prepares a draft demonstration package to support the
exclusion of the identified event-related data and provides an
opportunity for public comment. The air agency submits the draft
demonstration and any received public comments to its EPA Regional
office, which then reviews the submittal and concurs, nonconcurs or
defers a decision related to the air agency's request to exclude data
that have been affected by exceptional events. If the EPA agrees with
the air agency's request, the data are excluded. If the EPA does not
agree with the air agency claim, or if the EPA decides to defer a
decision on the submittal, the data are used in regulatory
determinations.
The 2007 Exceptional Events Rule was challenged in 2008. In NRDC v.
EPA, 559 F.3d 561 (D.C. Cir. 2009), the Natural Resources Defense
Council (NRDC) brought a petition for review challenging the EPA's
definition of a natural event and seeking to vacate several statements
in the preamble to the final 2007 Exceptional Events Rule concerning
the types of events that could qualify as being eligible for exclusion
under the rule provisions. In particular, NRDC objected to treating
``events in which human activities play `little' causal role'' as
natural events. Regarding the definition of a natural event, the D.C.
Circuit Court determined that NRDC did not identify its objection
during the rulemaking process and, therefore, did not have standing
under CAA section 307 to challenge the definition.
NRDC also challenged the preamble language addressing high wind
events. In its decision, the D.C. Circuit stated,
In one section of the preamble, EPA refers to its ``final rule
concerning high wind events,'' which ``states that ambient
particulate concentrations due to dust being raised by unusually
high winds will be treated as due to uncontrollable natural events''
when certain conditions apply. . . . There is no such final rule.
The final rule does not mention high wind events or anything about
``ambient particulate matter concentrations.'' EPA calls this a
drafting error. In light of the error, the high wind events section
of the preamble is a legal nullity.
The EPA believes it is clear that the ``high wind events section of
the preamble'' to which the court referred is the entire section
titled, ``B. High Wind Events'' beginning at 72 FR 13576. Accordingly,
since 2007, the EPA has not relied solely on this section of the
preamble when implementing the 2007 Exceptional Events Rule. The EPA
maintains that certain of the preamble passages determined to be
``legally null'' are in fact appropriate interpretations of the
Exceptional Events Rule and are consistent with the CAA. For clarity
and regulatory certainty, the EPA is proposing in rule text form some
of the interpretative positions originally stated in the High Wind
Events section of the preamble to the 2007 Exceptional Events Rule.
Within each topical area of this notice, the EPA has provided more
detailed background information on specific aspects of the 2007
Exceptional Events Rule and its implementation to allow readers to
consider the proposed changes in the context of the current situation.
C. Early Experience in Implementing the 2007 Exceptional Events Rule
Interpreting and implementing the 2007 Exceptional Events Rule has
been a challenging process both for the air agencies developing
exceptional events demonstrations and for the EPA Regional offices
reviewing and acting on these demonstrations. Shortly after the EPA
promulgated the rule in 2007, air agencies asked the EPA to clarify key
rule provisions and expectations for these demonstrations. Air agencies
also asked for demonstration templates and/or examples of acceptable
demonstrations for various event and pollutant combinations. Although
the EPA provided some of this information via the exceptional events
Web site at http://www2.epa.gov/air-quality-analysis/treatment-data-influenced-exceptional-events, air agencies noted that, in their view,
the information provided was insufficient and sought additional
guidance to facilitate consistency among the EPA Regional offices in
interpreting and implementing the 2007 Exceptional Events Rule. In the
years since rule promulgation, air agencies continued to express
concern, through various mechanisms including formal letters, informal
emails, interaction at various meetings and Congressional testimony,
about the consistent application of the 2007 Exceptional Events Rule
and the resources expended to prepare exceptional events
demonstrations.
The EPA has also faced challenges in reviewing submitted
demonstrations. Because exceptional events are fact-specific and thus
unique and varied, providing templates or general guidance was, and
still is, challenging. The EPA also acknowledges that the final rule
and preamble language for the 2007 Exceptional Events Rule provided
room for interpretation, making it difficult for air agencies and the
EPA to determine
[[Page 72846]]
how much evidence or technical analysis for demonstrations is needed.
We do, however, think that providing additional recommendations on
appropriate documentation would be helpful. Throughout this proposal,
for example in section V.E, Technical Criteria for the Exclusion of
Data Affected by Events, and in section V.F, Treatment of Certain
Events Under the Exceptional Events Rule, we provide recommendations
for language and analyses to include in demonstration packages.
Additional detail regarding specific recommendations is available in
the EPA's guidance documents and on the EPA's exceptional events Web
site, which the EPA will update to incorporate the finalized rule
changes concurrently with or shortly after promulgating the final rule.
The EPA will also continue to maintain and update the exceptional
events submissions table on its Web site with examples of approved
submissions. These examples may help air agencies develop demonstration
packages; however, they may not contain the minimum level of data or
case-specific analyses necessary for all exceptional events
demonstrations of the same event type. In addition, commenters on this
notice may wish to provide suggestions on the appropriate documentation
for specific types of exceptional events demonstrations.
D. The EPA's Interim Exceptional Events Implementation Guidance
As a result of stakeholder-identified concerns and the EPA's own
experience related to implementing the 2007 Exceptional Events Rule, in
2010 the EPA began developing additional implementation guidance. In
May of 2011, the EPA released the Draft Exceptional Events
Implementation Guidance: The Draft Guidance to Implement Requirements
for the Treatment of Air Quality Monitoring Data Influenced by
Exceptional Events, the Draft Exceptional Events Rule Frequently Asked
Questions document and the Draft Guidance on the Preparation of
Demonstrations in Support of Requests to Exclude Ambient Air Quality
Data Affected by High Winds under the Exceptional Events Rule. The EPA
provided these draft guidance documents to interested air agencies,
FLMs, other federal agencies and other parties upon request, for
preliminary review to solicit comment and help ensure that the EPA's
final guidance provided an efficient and effective process to make
determinations regarding air quality data affected by exceptional
events. The EPA also placed additional examples of approved
demonstrations on the EPA's Web site.
The EPA incorporated the commenters' feedback, as appropriate, into
revised draft guidance documents, which were made available for broad
public review in a July 6, 2012, Federal Register Notice of
Availability (77 FR 39959) and in the associated docket (Docket ID No.
EPA-HQ-OAR-2011-0887).\4\ This docket includes a summary of the comment
and response process from the 2011 preliminary review of the draft
guidance documents. In addition to identifying specific comments on the
draft guidance documents, this summary clearly identifies that
implementation challenges originated shortly after the EPA promulgated
the 2007 Exceptional Events Rule.\5\ In May 2013, after a round of
review and comment by the general public, the EPA finalized the Interim
Exceptional Events Implementation Guidance and made these documents
publicly available on the exceptional events Web site at http://www2.epa.gov/air-quality-analysis/treatment-data-influenced-exceptional-events.\6\
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\4\ The EPA established Docket ID No. EPA-HQ-OAR-2011-0887 for
the July 2012 notice of availability for the Draft Exceptional
Events Implementation Guidance and has incorporated this docket into
the record for this action.
\5\ Responses to Significant First-Round Comments on the Draft
Guidance Documents on the Implementation of the Exceptional Events
Rule, U.S. EPA, June 2012. Available in Docket No. EPA-HQ-OAR-2011-
0887.
\6\ The Interim Exceptional Events Implementation Guidance
includes: The Interim Guidance to Implement Requirements for the
Treatment of Air Quality Monitoring Data Influenced by Exceptional
Events, the Interim Exceptional Events Rule Frequently Asked
Questions (the Interim Q&A document), and the Interim Guidance on
the Preparation of Demonstrations in Support of Requests to Exclude
Ambient Air Quality Data Affected by High Winds under the
Exceptional Events Rule (the Interim High Winds Guidance document).
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With the release of the Interim Exceptional Events Implementation
Guidance, the EPA simultaneously acknowledged the need to consider
additional changes that could only be accomplished through a notice-
and-comment rulemaking to revise the 2007 Exceptional Events Rule. To
inform the development of proposed rule revisions, the EPA hosted
exceptional events listening sessions in August and November of 2013
for interested air agencies, FLMs, other federal agencies, regional
planning organizations, non-governmental organizations and other
members of the public. The EPA has considered feedback from these
listening sessions and the previous public comments on the Interim
Exceptional Events Implementation Guidance in the development of these
proposed revisions to the 2007 Exceptional Events Rule.
E. More Recent Implementation Experience Including EPA-Recommended Best
Practices for the Development of Exceptional Events Demonstrations
Because of the passage of time since the 2013 exceptional events
listening sessions, the EPA's Office of Air Quality Planning and
Standards (OAQPS) held conference calls with some air agencies and the
EPA Regional offices between September 2014 and March 2015 to ask
whether any new implementation concerns had arisen and to better
understand currently employed exceptional events implementation
processes and practices.
As a result of these discussions, the EPA developed a list of best
practices for communication and collaboration between the EPA and air
agencies. These best practices include having discussions before,
during and after the development and submission of exceptional events
demonstration packages. Specifically, these best practices recommend
that the EPA Regional offices and their air agencies discuss, on a
mutually agreed upon frequency, those demonstrations that the agencies
have developed and submitted for the EPA's action. These regular
discussions should focus on whether the demonstrations have regulatory
significance (e.g., significance for any of the five types of
regulatory actions identified in section V.C.) and, if not, whether the
EPA can provide general technical or policy feedback that the air
agency can include in future demonstrations. Prior to an air agency's
development of future demonstrations, the air agency and the EPA should
identify the relevant days and monitors of focus, the regulatory
significance of these monitor days, the analyses of particular interest
for a specific event and pollutant combination and the anticipated
timeframe for demonstration submission and response. Discussions should
continue while the air agency is developing the demonstration and after
the agency submits the demonstration and while the EPA is reviewing the
demonstration, to ensure both the air agency and the EPA are aware of
status, direction and progress. Finally, after the EPA has acted on the
demonstration, the reviewing EPA Regional office and the air agency
should discuss elements of the process that should continue and those
that should be improved, should understand the information in the
demonstration that was useful versus the information that was
extraneous and should discuss the possibility of
[[Page 72847]]
developing a demonstration template(s) for future events of the same
type(s).
Agencies using this communications approach have developed a common
understanding of expectations, terminology and interpretation of the
EPA's regulations and policy, which, in turn, helps focus efforts,
optimize resources and save time during the demonstration development
and review process. A summary of this ``best practices'' approach to
implementation is available at http://www2.epa.gov/air-quality-analysis/treatment-data-influenced-exceptional-events.
V. Proposed Rule Revisions
A. To whom and to what pollutants does the Exceptional Events Rule
apply?
1. Current Situation
Under the CAA, states are primarily responsible for the
administration of air quality management programs within their borders,
which includes monitoring and analyzing ambient air quality, submitting
monitoring data to the EPA, which are then stored in the EPA's AQS
database, and identifying measurements that may warrant special
treatment under the Exceptional Events Rule. The 2007 Exceptional
Events Rule applies to all state air agencies and to local air quality
agencies to whom a state has delegated relevant responsibilities for
air quality management, including air quality monitoring and data
analysis.
Additionally, the 2007 Exceptional Events Rule applies to some
tribal air quality agencies who have been granted treatment as a state
for section 319 of the CAA. Section 301(d) of the CAA authorizes the
EPA to recognize tribal authority, allowing eligible, federally-
recognized tribal governments to implement provisions of the CAA.
Pursuant to section 301(d)(2), the EPA promulgated regulations, known
as the Tribal Authority Rule (TAR), on February 12, 1999 (63 FR 7254,
codified at 40 CFR part 49). That rule specifies those provisions of
the CAA for which it is appropriate to treat tribes in a similar manner
as states. Under the TAR, tribes may choose to develop and implement
their own CAA programs, but are not required to do so. The TAR also
establishes procedures and criteria by which tribes may request from
the EPA a determination of eligibility to implement the provisions of
the CAA. In cases where a tribal air quality agency is eligible to
implement CAA section 319 and has installed and operates an air quality
monitoring network that produces regulatory data that is affected by
emissions from exceptional events, the criteria and procedures
identified in these proposed rule revisions may be used to exclude data
for purposes of regulatory decisions. Some tribes may implement only
portions of the relevant air quality monitoring program and may choose
not to address all of the procedures and requirements associated with
excluding data that have been influenced by exceptional events (e.g., a
particular tribe may operate a monitoring network for purposes of
gathering and identifying data appropriate for informational or
educational purposes, but may choose not to implement relevant programs
for the purpose of mitigating the effects of exceptional events). Where
a tribal air quality agency is not eligible to implement CAA section
319 but operates an air quality monitoring network that produces
regulatory data that is affected by emissions from exceptional events,
the tribal air quality agency should consult with the EPA Regional
office prior to addressing the procedures and requirements associated
with excluding data that have been influenced by exceptional events.\7\
In all cases, the EPA will continue to work with tribes in implementing
any promulgated rule revisions.
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\7\ As of the signature date of this action, only one tribe is
eligible to implement all portions of CAA section 319 under the TAR.
Several other tribes, however, operate air quality monitoring
networks that produce regulatory data that could be affected by
emissions from exceptional events.
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While air agencies are responsible for administering air quality
management programs within their borders, FLMs of Class I areas, other
federal agencies and/or other entities (e.g., industrial facilities
pursuant to permit conditions) may also operate ambient air quality
monitors that meet all requirements of 40 CFR parts 50 and 58.\8\ The
FLMs, other federal agencies and other entities operating these
regulatory monitors may submit collected data to the EPA's AQS
database.\9\ These concentration measurements can be affected by
exceptional events. The AQS software allows only the entity operating a
monitor (and the EPA data system manager) to apply exceptional events
flags to data from that monitor. Although FLMs and other entities can
apply exceptional events flags to data from monitors they operate, the
Exceptional Events Rule at 40 CFR 50.14(b)(1) states that the EPA shall
exclude data from use in determinations of exceedances and NAAQS
violations where a state demonstrates to the EPA's satisfaction that an
exceptional event caused a specific air pollution concentration in
excess of one or more NAAQS. The language, ``where a State
demonstrates'' has resulted in an interpretation that only states can
initiate the exceptional events process and submit demonstrations. Some
stakeholders have asked the EPA to identify the process that the state
air agency should follow if the state air agency does not have AQS
access rights to place exceptional events flags on event-affected data
from monitoring stations located within the state but not operated by
the state. The EPA addressed this issue generally in Question 23 of the
Interim Q&A document by indicating that air agencies should consult
with their EPA Regional office early in the development of an
exceptional event demonstration package if they believe that monitors
on federally-owned and managed land (e.g., national parks within the
state) have been affected by an event. In these instances, the EPA has
assisted in facilitating cross-agency coordination regarding the
flagging of data, where needed.
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\8\ The Ambient Air Quality Surveillance provisions in 40 CFR
part 58 include, among other elements, the requirements for
monitoring data certification and data submittal and archive in AQS.
40 CFR 58.3 provides that these data reporting requirements
specifically apply to state air pollution control agencies and any
local air pollution control agency to which the state has delegated
authority to operate a portion of the state's monitoring network.
\9\ For a description of one network of monitoring sites
operated by federal agencies, see the 2014 CASTNET (Clean Air Status
and Trends Network) Annual Network Plan, available at http://epa.gov/castnet/javaweb/ozone/CASTNET_Plan_2014_Final.pdf, which
applies to National Park Service (NPS) and Bureau of Land Management
(BLM) site managers operating CASTNET monitors.
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The 2007 Exceptional Events Rule applies to all criteria pollutant
NAAQS.\10\ This is appropriate given the language in CAA section
319(b)(3)(B)(iv), which applies to exceedances or violations of ``the
national ambient air quality standards.'' The EPA regulations for the
interpretation of ambient data with respect to the NAAQS that were in
place prior to the 2007 Exceptional Events Rule and that have not been
revised do not contain provisions allowing for the special handling of
air quality data affected by exceptional events or do so without
explicit reference to the Exceptional Events Rule as governing such
exclusion. One NAAQS without a specific provision for handling event-
[[Page 72848]]
affected data is 40 CFR part 50, appendix K for PM with a nominal mean
aerodynamic diameter less than or equal to 10 micrometers
(PM10). Nevertheless, the EPA has enabled in AQS the
capability to flag all criteria pollutant data, including the option
for the EPA's concurrence, as the EPA maintains that the monitored
concentrations of all NAAQS pollutants have the potential to be
elevated by one or more event types and the Exceptional Events Rule
should govern the process of data exclusion for certain types of
regulatory actions (see section V.C).
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\10\ There are NAAQS for carbon monoxide (CO), lead (Pb),
nitrogen dioxide (NO2), ozone, particle pollution and
sulfur dioxide (SO2). This applicability includes the
primary and secondary NAAQS. At present, most of the secondary NAAQS
are identical to the primary NAAQS for the same pollutant, so there
is no distinction in how the Exceptional Events Rule applies. To
date, the EPA has not encountered an exceptional event situation
with respect to a non-identical secondary NAAQS.
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2. Proposed Changes
As noted above, because FLMs and other federal agencies may operate
regulatory monitors and submit collected data to the EPA's AQS database
and emissions from exceptional events could affect these same monitors,
the EPA proposes to allow FLMs and other federal agencies to prepare
and submit exceptional events demonstrations and data exclusion
requests directly to the EPA. The EPA believes that the CAA language at
section 319(b)(3)(B)(i), which states that ``the occurrence of an
exceptional event must be demonstrated by reliable, accurate data that
is promptly produced and provided by Federal, State, or local
government agencies'' provides authority for FLMs to initiate and
submit such demonstration packages and data exclusion requests.
Further, the EPA believes this is appropriate because, in many cases,
the lands managed and/or owned by federal entities are not entirely
within the jurisdictional boundary of a single state or local
government. Also, as we discuss in more detail in section V.F.2,
federal entities may either initiate prescribed fires or fight
wildfires on lands managed and/or owned by federal entities. The EPA
could determine both of types of fires to be exceptional events. The
EPA expects that allowing FLMs and other federal agencies to submit
exclusion requests directly will expedite the exceptional events
demonstration development and submittal process. The EPA solicits
comment on this proposed addition to the rule text, which appears at
the end of this document. Based on comments received, the EPA may
retain, modify or not include this provision in the final promulgated
rule. This provision would apply only to FLMs and other federal
agencies that either operate a monitor that has been affected by an
event or that manage land on which an exceptional event originates. The
provision would allow such FLMs and other federal agencies to provide
demonstrations directly to the EPA only after a discussion with the
state in which the monitor is operated. Alternatively, this discussion
might result in an agreement that the federal agency flag the data in
AQS at the air agency's request and then provide a draft demonstration
document to the appropriate state air agency for adoption and
submission by the air agency to the EPA, as is currently allowed.
Regardless of who ultimately submits the demonstration, the EPA
encourages collaboration between the FLMs and other federal agencies
and the appropriate state air agency during the event identification
and demonstration development process. If the provision for direct
submission to the EPA is included in the final action, demonstrations
prepared by FLMs or other federal agencies would be required to meet
all provisions in the Exceptional Events Rule, including the
requirement for a public comment period on a prepared demonstration
\11\ and the requirements related to schedules and procedures for
demonstration package submittal (see sections V.G.4, V.G.5 and V.G.6)
that apply to state agencies that operate monitors.
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\11\ A public comment opportunity is important prior to
submission to the EPA because under the Exceptional Events Rule the
EPA is not required to provide a public comment opportunity prior to
concurring with an air agency's request to exclude data. The EPA
generally provides a public comment opportunity before we use air
quality data, with or without such exclusions, in a final regulatory
action. States typically provide an opportunity for public comment
by posting draft demonstrations on a Web site. Federal agencies
could do the same.
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B. What is an exceptional event?
1. Current Situation
The existing definition of an exceptional event at 40 CFR 50.1(j)
repeats the CAA definition, which provides that an exceptional event is
one that affects air quality, is not reasonably controllable or
preventable, is caused by human activity that is unlikely to recur at a
particular location or is a natural event, and is determined by the
Administrator in accordance with 40 CFR 50.14 to be an exceptional
event. Also, CAA section 319(b)(3)(B)(ii) requires that a clear causal
relationship must exist between the measured exceedances of a NAAQS and
the exceptional event to demonstrate that the exceptional event caused
a specific air pollution concentration at a particular air quality
monitoring location. In addition to these defining elements, the 2007
Exceptional Events Rule at 40 CFR 50.14(c)(3)(iv) requires that the
demonstration provide evidence that ``the event is associated with a
measured concentration in excess of normal historical fluctuations,
including background'' and evidence that ``there would have been no
exceedance or violation but for the event.''
Both the statutory and regulatory definitions of an exceptional
event include the provision that the event affected air quality. Many
types of events affect air quality by causing emissions or increasing
otherwise occurring emissions. Stratospheric ozone intrusions, one type
of event, differ from most other event types in that they transport
ozone already formed in the stratosphere to a surface monitor. High
temperatures, air stagnations and meteorological inversions can
increase the level of air pollution formed from a given amount of
emissions. However, both the statutory and regulatory definitions of an
exceptional event specifically exclude stagnation of air masses,
meteorological inversions and meteorological events involving high
temperatures or lack of precipitation, as well as air pollution
relating to source noncompliance.
While the CAA definition of an exceptional event excludes ``a
meteorological event involving high temperatures or lack of
precipitation,'' high temperatures and drought conditions can
contribute to exceedances and violations caused by other exceptional
events such as high wind dust events. If an air agency submits evidence
showing that a severe drought that resulted in arid conditions (e.g.,
lower than typical soil moisture content, decreased vegetation) was
combined with an event, such as a high wind event, that falls within
the CAA definition of an exceptional event and has affected air quality
data, these data could be considered eligible for exclusion under the
provisions of the Exceptional Events Rule. Under this scenario, the EPA
would consider the high wind event as the critical exceptional event.
The high wind event would need to meet the provisions of the
Exceptional Events Rule, including assessing whether the event is a
natural event or an event due to human activity unlikely to recur at a
particular location. As another example, if a wildfire exacerbated by
drought conditions causes ozone exceedances, then the EPA can consider
the ozone exceedances for exclusion under the Exceptional Events Rule
because wildfires, unlike lack of precipitation itself, are not
excluded from the CAA definition of an exceptional event. However, high
temperatures alone that result in elevated ozone concentrations would
not be eligible for exclusion under the
[[Page 72849]]
Exceptional Events Rule. Elevated temperatures and inversions can
affect ambient air quality apart from any interactions with emissions,
but such conditions alone are not exceptional events by the very clear
provisions of the CAA. The EPA believes that Congress intended air
agencies to compensate for the effects of high temperature and
inversions on concentrations formed from anthropogenic emissions
through the development of SIPs.
To summarize, the 2007 Exceptional Events Rule specifies six
elements that air agencies must address when requesting that the EPA
exclude event-related concentrations from regulatory determinations:
The event affected air quality.
The event was not reasonably controllable or preventable.
The event was a human activity that is unlikely to recur
at a particular location, or was a natural event.
There exists a clear causal relationship between the
specific event and the monitored exceedance.
The event is associated with a measured concentration in
excess of normal historical fluctuations including background.
There would have been no exceedance or violation but for
the event.
Section 50.14(b)(3) clearly makes the first three of these elements
preconditions for the EPA to approve an air agency's request to exclude
data. However, the last three of these elements are listed only in
Sec. 50.14(c)(iv), which provides that the state ``shall provide
evidence'' that they are true. Since promulgation of the 2007
Exceptional Events Rule, the EPA has treated all six elements as
conditions that air agencies must address in a demonstration prior to
the EPA's concurring with an air agency's request to exclude data. In
the Interim Exceptional Events Implementation Guidance, the EPA stated
that for the fifth of these elements (e.g., the ``historical
fluctuations'' element), there is no bright line that defines when a
concentration is ``in excess of historical fluctuations.'' With respect
to the sixth element, referred to as the ``but for'' criterion,
although the EPA has, in some cases, expected demonstrations to contain
a quantitative estimate of the concentration increment caused by the
event, more frequently the EPA has considered the ``but for'' criterion
to be satisfied by a more qualitative showing that the measured
concentration was much greater than the non-exceedance concentration
that would have normally been expected on the day in question.
In addition to considering whether or not an event is
``exceptional'' under the Exceptional Events Rule, an air agency and
the EPA must also decide whether an ``event'' has occurred. An event,
or anomaly, is a deviation from normal or expected conditions that
contributes to air pollution. In some cases, air agencies or other
observers can clearly see this ``deviation,'' for example unusually
high wind speeds transporting dust, fires generating PM or ozone
precursors or volcanoes venting plumes of SO2, PM and PM
precursors.\12\ In other cases, such as with stratospheric ozone
intrusions, the physical effects of the event may not be visible and
the occurrence of an event can only be inferred from seeing the effect
on monitored air quality of emissions associated with the event. As
described in section V.E.3, comparing the ambient pollutant
concentrations in question to the historical distribution of
concentrations of the same pollutant can help an air agency determine
whether a deviation from normal concentrations occurred. However, such
comparisons must consider that multiple factors often contribute to
high pollutant concentrations. Some events, such as stratospheric ozone
intrusions and high wind dust events, may last only a few hours at any
one location. Still other events, such as volcanic activity, may occur
and affect pollutant concentrations for a sustained period of time
(e.g., multiple days). Some events may create pollutant-increasing
conditions that persist after the original event process has ceased,
for example high winds or volcanic eruptions that leave deposits of
dust on roadways.
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\12\ The EPA considers on-going emissions from volcanic activity
to be ``events'' even if they occur every day over a long period.
The EPA considers this approach to be consistent with Congressional
intent, but that extending the same treatment to air pollution due
to every day biological processes or lightning would not be
consistent with that intent.
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2. Proposed Changes
The EPA is proposing the following generally applicable changes to
the 2007 Exceptional Events Rule with respect to clarifying what
constitutes an exceptional event:
Revising the definition of exceptional event by including
the concept of considering the combined effects of an event and the
resulting emissions.
Removing the ``but for'' element.
Moving the ``clear causal relationship'' element into the
list of criteria that explicitly must be met for data to be excluded.
Subsuming the ``affects air quality'' element into the
``clear causal relationship'' element.
Removing the term ``historical fluctuations'' and
replacing it with text referring to a comparison to historical
concentrations, identifying the types of analyses that are necessary in
a demonstration to address the comparison of the event-affected
concentration to historical concentrations and clarifying that an air
agency does not need to prove a specific ``in excess of'' fact.
Making these changes would result in returning to the following
three core statutory elements of CAA section 319(b) that air agencies
must meet when requesting that the EPA exclude event-related
concentrations from regulatory determinations:
The event affected air quality in such a way that there
exists a clear causal relationship between the specific event and the
monitored exceedance or violation.
The event was not reasonably controllable or preventable.
The event was a human activity that is unlikely to recur
at a particular location or was a natural event.
The implicit intent of CAA section 319(b) is that when the above
conditions are met, the data should be excluded from regulatory
decisions so as not to drive SIPs to include unreasonable or additional
measures to address the effects of certain events.
a. Definition of an Event
While an event may have a physical component that is purely natural
in origin, for example high wind speeds, human activity either prior to
or simultaneous with the event may influence air quality during the
event. In implementing the 2007 Exceptional Events Rule, the EPA's
approach in determining whether an exceptional event that affected a
monitored concentration was natural or due to human activity (an
important distinction, as discussed in section V.D) has been to
consider both whether the initiating physical event was natural or the
result of human activity and whether human activity had any role in
strengthening the emissions generation process. In contrast, some
parties have argued that only the naturalness of the initiating
physical event should be considered. To clarify that an event is not a
``natural event'' merely because natural processes initiated the
emissions generation process, the EPA proposes to revise the regulatory
definition of exceptional event to say that both the naturally
occurring physical event and its associated resulting emissions are to
[[Page 72850]]
be considered when applying the definitions and criteria for exclusion
provided in the Exceptional Events Rule. For example, an exceptional
event might consist of a high wind and the subsequently entrained PM
that is transported to a monitoring site or a wildfire that generates
ozone or ozone precursors, which are transported to a monitoring site.
The EPA would not consider the physical event (e.g., in the previous
example, the high wind or the wildfire) to be an exceptional event
unless the resulting emissions (e.g., the PM or ozone) reached and
elevated the concentration at a monitoring location or locations.
b. ``But For'' Element
The EPA proposes to rely more directly upon the statutory
requirement at CAA section 319(b)(3)(B)(ii) by removing the regulatory
requirement at 40 CFR 50.14(c)(3)(iv)(D) that ``there would have been
no exceedance or violation but for the event'' (i.e., the ``but for''
criterion). In promulgating the 2007 Exceptional Events Rule, the EPA
derived the ``but for'' criterion from the language at section
319(b)(3)(B)(ii), which requires ``a clear causal relationship. . .
between the measured exceedances . . . and the exceptional event to
demonstrate that the exceptional event caused a specific air pollution
concentration at a particular air quality monitoring location.'' \13\
The EPA combined this language with the requirement that there be
``criteria and procedures for the Governor of a State to petition the
Administrator to exclude . . . data that is directly due to the
exceptional events.'' \14\ Under the EPA's interpretation of CAA
section 319(b) at the time, these words suggested that a ``but for''
causation standard for exceptional events was appropriate.
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\13\ The EPA believes that the terminology ``specific air
pollution concentration'' refers to the identified exceedance or
violation rather than a specific increment in the measured
concentration, which implies quantitative source attribution and a
supporting quantitative analysis.
\14\ CAA section 319(b)(3)(B)(iv) (emphasis added).
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Air agencies have expressed concern that the EPA has, in many
cases, historically interpreted the ``but for'' criterion as implying
the need for a strict quantitative analysis to show a single value, or
at least an explicitly bounded plausible range,\15\ of the estimated
air quality impact from the event. While a single event can in some
cases clearly be shown to be a ``but for'' cause of a NAAQS exceedance
or violation in the sense that without the event, the exceedance or
violation would not have occurred, it is more often the case that the
impact of emissions from events and other sources cannot be separately
quantified and distinguished, and the ``but for'' role of a single
source or event is difficult to determine with certainty. Even when the
effects of events are quantifiable with a sufficient degree of
confidence, air agencies have reported expending significant resources
to quantify them. The EPA was aware of these concerns in 2007 as a
result of public comment on the proposed rule and attempted to
alleviate them by stating in the preamble to the 2007 Exceptional
Events Rule that an air agency's ``but for'' analysis does not
necessarily need to be precise and that the EPA would use a holistic
``weight of evidence'' approach in analyzing submitted demonstration
packages.\16\ Without clear examples of what the EPA would accept as
satisfying a weight of evidence approach, some air agencies began using
burdensome approaches to provide quantitative ``but for'' analyses in
their exceptional events demonstrations. The reviewing EPA Regional
offices use similarly resource-intensive approaches to validate these
quantitative analyses as they review demonstrations. In some cases, the
detailed quantitative approaches have not produced results any better
than what could have been achieved with less burdensome measures.
Therefore, the EPA is proposing to remove the ``but for'' regulatory
language and focus on the ``clear causal relationship'' statutory
criterion applied to the specific case, using a weight of evidence
approach.\17\
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\15\ The EPA stated in the preamble to the 2007 Exceptional
Events Rule that a ``weight of evidence demonstration can present a
range of possible concentrations, which is not as technically
demanding as justifying a specific adjustment to a measured value.''
72 FR 13570 (March 22, 2007).
\16\ 72 FR 13570 (March 22, 2007).
\17\ The term ``weight of evidence'' means that the EPA will
consider all relevant evidence and qualitatively ``weigh'' this
evidence based on its relevance to the Exceptional Events Rule
criterion being addressed, the degree of certainty, its
persuasiveness, and other considerations appropriate to the
individual pollutant and the nature and type of event.
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In so doing, we propose that in their submittals, air agencies
demonstrate by the weight of evidence in the record that the event
caused the specific air pollution concentration at issue.\18\ Depending
on the event characteristics and the case-by-case nature of the
evaluation, an air agency may or may not need to provide quantitative
analyses or estimates to support the weight of evidence approach. The
EPA will discuss with an air agency the appropriate approach for a
given event demonstration during conversations preceding the submittal
of a demonstration. For example, when a concentration during an event
is higher than any concentration previously observed in the same area
and time of year, the air agency will generally not need to quantify
the event impact to reach the conclusion that the event ``caused'' the
concentration at issue. However, in cases where the concentrations on
non-event days during the same season come close to or exceed the
applicable NAAQS, thus providing evidence that non-event pollution
sources may produce exceedances of the NAAQS, the EPA would expect an
air agency's clear causal relationship showing to include a
quantitative estimate (or range of estimates) of the specific event's
impact on air pollution concentrations, even if uncertain, as a part of
a weight of evidence showing alongside other qualitative evidence.
Section V.E.3 of this proposal clarifies the EPA's expectations
regarding analyses associated with the ``clear causal'' criterion.
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\18\ This approach is consistent with language in the preamble
to the 2007 Exceptional Events Rule that states, ``The final rule
permits a case-by-case evaluation, without prescribed threshold
criteria, to demonstrate that an event affected air quality.'' 72 FR
13569 (March 22, 2007).
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c. Clear Causal Relationship Element
The EPA is proposing to modify the regulatory language in section
50.14(c)(iv) to more clearly indicate, consistent with the CAA
directive, the requirement to ``demonstrate'' versus to merely
``provide evidence'' that a clear causal relationship must exist
between the specific event and the monitored exceedance. The EPA will
evaluate this criterion on a weight of evidence basis.
d. Affects Air Quality Element
As explained above, the EPA has treated the ``affects air quality''
element as a distinct criterion that air agencies must meet for data to
be excluded, and has expected exceptional events demonstrations to
conclude that the ``affects air quality'' condition has been satisfied.
However, after carefully considering Congress' intent and air agencies'
and the EPA's experience in implementing the 2007 Exceptional Events
Rule, we propose to integrate the phrase ``affected air quality'' into
the clear causal relationship criterion. We believe that separately
requiring an air agency to provide evidence to support a conclusion
that an event ``affects air quality'' is unnecessary if we finalize
this proposal to require a mandatory clear causal relationship showing.
If an air agency demonstrates that an event has a clear causal
relationship to an exceedance or violation of a NAAQS,
[[Page 72851]]
then the event has certainly affected air quality. This proposed
approach will reduce the time required to prepare demonstrations,
reduce their length, result in more understandable demonstrations for
the public during the notice-and-comment process, and simplify and
expedite the EPA's review process.
e. Historical Fluctuations Element
As we indicated in the Interim Exceptional Events Implementation
Guidance, we believe that a comparison of the claimed event-influenced
concentration(s) to concentrations at the same monitoring site at other
times is extremely useful evidence in an exceptional events
demonstration. The EPA considers these comparisons as part of the
evidence available for determining whether an air agency has satisfied
the statutory and regulatory ``clear causal relationship'' criterion.
Because preparing this type of comparison is within the ability and
resources of every air agency, the EPA proposes to continue to require
this type of comparison in every demonstration. However, the EPA is
proposing to re-word the requirement to prevent misinterpretation that
this comparison must show that the concentration in question was ``in
excess of normal historical fluctuations, including background.'' This
phrase is not clear and has caused confusion and regulatory
uncertainty. For example, ``fluctuations in concentrations'' can convey
either day-to-day or hour-to-hour differences in monitored
concentrations. These concentration differentials cannot usefully be
compared to an absolute concentration (i.e., monitored concentration at
a given point in time) because many absolute concentrations will be
larger than the differences between concentrations. The phrase ``in
excess'' might be interpreted to mean that the concentration at issue
must be higher than all historical concentrations, but the EPA
maintains that Congress did not intend this, nor would such an
interpretation be reasonable. Concentrations that are exceedances of a
standard but are not higher than all concentrations recorded at a
particular monitor may be causally connected to an event of the type
that Congress clearly identified for treatment as an exceptional event.
Finally, the language ``including background'' is confusing. In many
cases, the monitor or monitors intended to represent ``background''
concentrations are separated from the event-influenced monitoring site
by some distance such that the event-influenced monitor and the
``background'' monitor reflect a different mixture of emissions
sources, which could lead to misinterpretation. Regardless, the EPA
sees no clear reason why such ``background'' concentrations are
relevant for analyses associated with provisions in the Exceptional
Events Rule.
The change that the EPA is proposing to the text of the 2007
Exceptional Events Rule would require demonstrations to include a
comparative analysis of the concentration data alleged to have been
affected by an event and data at other times, and would specify certain
aspects of the analysis. The change would also make clear that there is
no specific ``in excess of'' relationship between the event-affected
data and other data that must be proven, for example that the event-
affected data be above a certain percentile point in the annual
distribution of data. Section V.E.3 of this proposal contains
additional detail regarding the minimum set of statistical analyses
that the EPA expects to see in demonstrations.
C. What types of ambient concentration data and data uses may be
affected by the Exceptional Events Rule?
The CAA language at section 319(b)(3)(B)(iv) requires the
Administrator to promulgate regulations that provide that there are
criteria and procedures for the governor of a state to petition the
Administrator to exclude air quality monitoring data that is directly
due to exceptional events from use in determinations by the
Administrator with respect to exceedances or violations of the national
ambient air quality standards. The implementing language in the 2007
Exceptional Events Rule states at 40 CFR 50.14(a)(1) that air agencies
may request that the EPA exclude data showing exceedances or violations
of the NAAQS that are directly due to an exceptional event from use in
determinations without naming those determinations in that paragraph.
The rule at 40 CFR 50.14(b)(1) states that the EPA shall exclude data
from use in determinations of exceedances and NAAQS violations where an
air agency demonstrates to the EPA's satisfaction that an exceptional
event caused a specific air pollution concentration in excess of one or
more NAAQS. Thus, both the statutory language and the 2007 Exceptional
Events Rule use the phrase ``in determinations of exceedances and NAAQS
violations'' with no further explanation.
In this section, we consider the specific types of determinations
by the Administrator that should be governed by CAA section 319(b).
This issue was not specifically addressed in the rulemaking that
promulgated the 2007 Exceptional Events Rule and consequently has
caused some confusion and regulatory uncertainty.
1. Current Situation
The EPA believes that Congress clearly intended the CAA language in
section 319(b) to apply to exclusions of ambient data from
determinations of whether a NAAQS exceedance or violation occurred at
an ambient monitoring site at a particular time in the past. We
characterize these exceedances or violations as occurring in the
``past'' because the process of determining whether an actual
exceedance or violation occurred involves reviewing the ambient air
monitoring data collected at monitoring sites over some historical
timeframe. For example, on December 14, 2012, the EPA promulgated a
revised primary annual PM2.5 NAAQS of 12.0 [mu]g/m\3\, which
is attained when the 3-year average of the annual arithmetic means does
not exceed 12.0 [mu]g/m\3\.\19\ The EPA Administrator made initial area
designation decisions for the revised NAAQS in December 2014 based on
air quality monitoring data for the most recent period 3-year period,
which was 2011 through 2013.\20\ Historical, or ``past,'' data were
reviewed and assessed to determine whether an exceedance or violation
had occurred that would influence a current or future regulatory
determination. Determinations of ``past'' exceedances or violations are
key to the EPA's actions to designate or redesignate an area, to
initially classify an area for a NAAQS (where classifications apply),
to determine if a nonattainment area has attained the NAAQS for which
it has previously been designated nonattainment, to determine whether a
nonattainment area is eligible for an attainment date extension (where
applicable) and, in some cases, to find that a SIP is inadequate and to
issue a SIP call. No affected stakeholders with whom the EPA has
interacted since 2007 have disputed this interpretation or approach.
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\19\ 78 FR 3086 (January 15, 2013).
\20\ 80 FR 2206 (January 15, 2015).
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It is not as clear whether CAA section 319(b) also means that data
should be excluded from determinations of whether a NAAQS exceedance or
violation will or is likely to occur in the future. Predictions of
future NAAQS violation(s) generally involve reviewing the historical
ambient concentration data that are the evident focus of CAA section
319(b), estimating expected
[[Page 72852]]
future emissions, and then using both of these data sets as inputs to
an air quality modeling tool or other analytical approach that
extrapolates these data to predict a future outcome. While science
supports and the EPA relies on predictions of future NAAQS violations
in several parts of the clean air program, such as in the EPA's
approval of attainment demonstrations in SIPs, in prevention of
significant deterioration (PSD) air permitting programs and in actions
to reclassify a moderate PM10 or PM2.5
nonattainment area to serious,\21\ the fact that these predicted future
values rely only in part on historical monitoring data implies that a
different standard for data exclusion may be appropriate.
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\21\ Projection of future NAAQS exceedances or violations do not
necessarily play a role in reclassification of an ozone
nonattainment area to a higher classification level.
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Another interpretation question is whether and under what
conditions event-affected data should be excluded from determinations
that are based wholly or in part on monitoring data but formally are
not determinations of exceedances or violations of the NAAQS. For
example, under 40 CFR part 51, subpart H, Prevention of Air Pollution
Emergency Episodes, the required content of a state's emergency plan
depends on whether the state has experienced air pollution that exceeds
a specified threshold level that is well above any NAAQS. Also, under
the EPA's guidance, the eligibility of an area for a simplified
maintenance plan for PM10 depends on the difference between
the better-than-the-NAAQS air quality in an area and the NAAQS.
To date, the EPA has not issued guidance that explicitly and
comprehensively identifies the types of data exclusion that are
authorized and required by CAA section 319(b) or that may be otherwise
appropriate and permissible. In the 2013 Interim Q&A document, the EPA
provided only limited clarification regarding the meaning of ``exclude
data.'' \22\ Question 14a of the Interim Q&A document notes that when
the EPA concurs based on the weight of evidence that an air agency has
successfully made the demonstrations referred to in 40 CFR 50.14(a)(2)
and (b)(1), then the EPA generally excludes the affected data from the
following types of calculations and activities:
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\22\ Interim Exceptional Events Rule Frequently Asked Questions.
U.S. EPA. May 2013. Available at http://www2.epa.gov/sites/production/files/2015-05/documents/eer_qa_doc_5-10-13_r3.pdf.
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The EPA's AQS does not count these days as exceedances
when generating user reports, and does not include them in design
values estimates,\23\ unless the AQS user specifically indicates that
they should be included, which may be appropriate for non-regulatory
applications of interest to the user.\24\
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\23\ The EPA uses design values in many regulatory decisions,
including, but not limited to, when designating areas as attainment,
nonattainment or unclassifiable for a NAAQS and when determining
whether a nonattainment area has attained or is still violating a
NAAQS. A design value is a statistic that describes the air quality
status of a given location relative to the level of a particular
NAAQS. Design values are computed according to the procedures
defined in 40 CFR part 50 and published annually by EPA's Office of
Air Quality Planning and Standards. Design values are available at
http://www.epa.gov/airtrends/values.html.
\24\ In some cases where the EPA has revised a NAAQS by
strengthening it, the default AQS query will exclude data for the
more recent, revised NAAQS, but may include concurred data for the
historical NAAQS.
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The EPA accepts the exclusion of these data for the
purposes of selecting appropriate background concentrations for PSD air
quality analyses \25\ and for transportation conformity hot spot
analyses.\26\
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\25\ If the EPA is the permitting authority, the EPA will
propose permits on this basis. If the EPA is commenting on another
permitting authority's proposed action, the EPA's comments will be
consistent with the determinations in this guidance document and any
applicable New Source Review (NSR) permitting and/or modeling
guidance.
\26\ Transportation conformity hot spot analysis is applicable
only to PM10 and PM2.5. ``Transportation
Conformity Guidance for Quantitative Hot-spot Analyses in
PM2.5 and PM10 Nonattainment and Maintenance
Areas,'' EPA-420-B-10-040, U.S. EPA Office of Transportation and Air
Quality, December 2010, page 98.
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The EPA accepts the exclusion of these data for the
purposes of selecting appropriate ambient data for projecting future
year concentrations as part of a modeled attainment demonstration.
The data continue to be publicly available, but the EPA's
publications and public information statements on the status of air
quality in the affected area generally do not reflect these data in any
summary statistic of potential regulatory application, unless such
inclusion is specifically noted.\27\
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\27\ These data may be included in statistics intended to
describe current status and trends in actual air quality in the area
for public information purposes including reporting of the Air
Quality Index.
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Thus, the EPA has maintained that once data are excluded under the
Exceptional Events Rule, these same data should be excluded from the
above-identified calculations and activities. The EPA has not clearly
addressed whether approval for exclusion under the Exceptional Events
Rule means that the data may or must be excluded for the purpose of
other types of actions that use monitoring data but are not included in
the list above. The EPA has also not clearly addressed whether data
that have not been approved for exclusion under the Exceptional Events
Rule can nevertheless under some other principle or interpretation be
excluded from any of the various types of calculations and activities.
The current situation is further complicated by the fact that the
conditions for data exclusion in CAA section 319(b) and the Exceptional
Events Rule, while logical when applied to determinations of NAAQS
exceedances or violations occurring in the past, may not be logical
when applied to predictions of future exceedances or violations. The
EPA recognizes, and acknowledged in Question 13 of the Interim Q&A
document, that an event may have made a past air concentration
significantly higher than it would have been in the absence of the
event contribution, and thus elevated an exceedance for a NAAQS
pollutant to an even greater degree of exceedance. This same event-
influenced concentration may not be eligible for exclusion under the
2007 Exceptional Events Rule because the ``but for'' criterion is not
satisfied because either (1) there would have been a 3-year violation
with or without the event or (2) there would not have been a violation
either with or without the event. The 2007 Exceptional Events Rule does
not explicitly authorize the exclusion of data associated with such an
event because the event fails to meet the clear causal relationship
criterion and ``but for'' criterion. Retaining the event-influenced
data could, however, have regulatory implications that seem contrary to
the purpose of CAA section 319(b). For example, retaining such data in
the calculation of the historical design value for a nonattainment area
can make it seem that the area needs more emissions reduction to attain
the NAAQS than is actually the case, and could lead to the EPA's
disapproval of an attainment demonstration that is in fact adequate,
and thus require the state to adopt additional emission controls.\28\
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\28\ The attainment demonstration would be adequate in the sense
that if a similar event does not occur during the period on which
actual attainment will be based, there would be no monitored NAAQS
violation, and if a similar event were to occur during that period
the event-affected data could be excluded and thus there would be no
``official'' violation.
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As another example, events can make past air concentrations higher
without causing an actual NAAQS exceedance or violation. However,
retaining such data in the calculation of background concentrations
used in air quality analysis for a PSD permit may suggest that there
will be a NAAQS violation after construction of a new source and
[[Page 72853]]
thus could prevent the permitting authority from issuing the
permit.\29\
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\29\ If a similar event were to occur after completion of
construction, the event-affected data could be excluded and thus
there would be no ``official'' violation.
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2. Proposed Changes
To remove the ambiguities described in the preceding section and to
provide greater regulatory certainty, the EPA proposes in regulatory
language to interpret the CAA section 319(b) phrase ``determinations by
the Administrator with respect to exceedances or violations of national
ambient air quality standards'' to encompass determinations of current
\30\ or historical NAAQS exceedances/violations or non-exceedances/non-
violations and determinations of the air quality ``design value'' at
particular receptor sites when made as part of the basis for any of the
following five types of regulatory actions:
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\30\ The term ``current'' denotes the determination at issue in
the current analysis. In actual practice, such determinations are
based on historical data and thus reflect a past actual condition.
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An action to designate or redesignate an area as
attainment, unclassifiable/attainment, nonattainment or unclassifiable
for a particular NAAQS. Such designations rely on a violation at a
monitoring site in or near the area being designated.
The assignment or re-assignment of a classification
category (marginal, moderate, serious, etc.) to a nonattainment area to
the extent this is based on a comparison of its ``design value'' to the
established framework for such classifications.
A determination regarding whether a nonattainment area has
actually attained a NAAQS by its CAA deadline.
A determination that an area has had only one exceedance
in the year prior to its deadline and thus qualifies for a 1-year
attainment date extension, if applicable.
A finding of SIP inadequacy leading to a SIP call to the
extent the finding hinges on a determination that the area is violating
a NAAQS.
For these types of actions, the EPA proposes to interpret the CAA to
require that data be excluded only if the requirements of section
319(b) and the Exceptional Events Rule are satisfied. In addition, we
propose that when one of these determinations is based on a combination
of monitoring data and air quality modeling, the criterion requiring
that there be a clear causal relationship between the event and a NAAQS
exceedance or violation will apply to the combined estimate of air
pollution levels rather than directly to the monitored background air
quality data. That is, the event would not be required to have caused
an actual exceedance or violation at the background ambient monitoring
site, but rather to have made the critical difference in the combined
estimate of air pollution levels (background plus source impact)
resulting in a NAAQS exceedance or violation, because the event
increased the background levels that are added to the air quality
modeling output.
When the EPA designates or redesignates areas as attainment or
nonattainment for the NAAQS; initially classifies ozone nonattainment
areas as marginal, moderate, serious, severe or extreme; grants a
request for a 1-year NAAQS attainment date extension where applicable;
or determines whether areas designated nonattainment for the NAAQS have
attained the respective NAAQS by the applicable attainment date, it
does so based on monitoring data (where available) or modeling of
actual air quality, or a combination thereof, as the evidence of the
occurrence or non-occurrence of a NAAQS exceedance or violation and, in
the case of classification actions, the degree of violation.\31\ In the
case of reclassifying an ozone nonattainment area to a higher
classification, the new classification is based on the design value
either at the time of the determination of attainment by the attainment
deadline under CAA section 181(b)(2), or at the time of the EPA's grant
of a voluntary request for reclassification from a state under CAA
section 181(b)(3).\32\ This proposal, if finalized, would in effect
apply the exceptional events process in the same way across these
related types of determinations and across the NAAQS, which we believe
is an appropriate interpretation of the CAA 319(b) phrase
``determinations by the Administrator with respect to exceedances or
violations of national ambient air quality standards.'' For these types
of determinations, the EPA proposes to exclude event-affected data only
if an air agency satisfies the procedural (e.g., event identification,
opportunity for public comment, demonstration submission) and
substantive (i.e., clear causal relationship, not reasonably
controllable or preventable, and human activity not likely to recur or
natural event) requirements of the exceptional events process. As
indicated previously, the EPA has maintained to this point that once
data are excluded under the Exceptional Events Rule, these same data
also should be excluded from (i) design value estimates and AQS user
reports (unless the AQS user specifically indicates that they should be
included), (ii) selecting appropriate background concentrations for PSD
air quality analyses and transportation conformity hot spot analyses,
and (iii) selecting appropriate ambient data for projecting future year
concentrations as part of a modeled attainment demonstration. As
described below, we intend that EPA approval for exclusion of data
under the Exceptional Events Rule continue to mean that the same data
may be excluded for the three applications listed in the previous
sentence, but that there should be other pathways for exclusion for the
second and third of these applications (and others) as well.
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\31\ The EPA's initial area designations process also makes use
of other information relevant to the CAA criteria for designations,
such as pollution contributions between nearby areas.
\32\ Reclassification of PM10 and PM2.5
nonattainment areas, by contrast, do not exclusively rely on area
design values (and thus, past monitored violations) but can also
result from the Administrator's determination that an area cannot
practicably attain a standard by the attainment date. See CAA
section 188(b)(1).
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This action proposes to require that data exclusion associated with
the five actions in the above bulleted list (i.e., initial area
designations, classifications, attainment determinations,
determinations regarding requests for attainment date extensions and
findings of SIP inadequacy leading to a SIP call) must follow the
provisions in the Exceptional Events Rule. It does not, however, mean
that the EPA would never exclude or agree to exclude event-affected
data from other types of regulatory determinations. For example, while
the EPA would exclude concurred-upon event-affected data from the five
types of regulatory actions discussed in V.C.1, the EPA would not
exclude these same data when setting priority classifications for
emergency plans under 40 CFR 51.150 as the EPA believes that
implementing the CAA principle at section 319(b)(3)(A) that
``protection of public health is the highest priority'' may necessitate
that an air agency address in its emergency plan the appropriate
planned response for any elevated concentration known to be possible
because it has already been observed, although the appropriate type of
response may depend on the cause(s) of the elevated concentration. The
concept that the EPA does not consider CAA section 319(b) and the
revised Exceptional Events Rule to be the necessary or sole governing
authorities for all data exclusions will be discussed further in
upcoming, new draft guidance on excluding (or in some cases not
excluding) data, independent of the Exceptional Events Rule, from
several
[[Page 72854]]
types of determinations and regulatory actions. The EPA is currently
developing a supplementary guidance document, Draft Guidance for
Excluding Some Ambient Pollutant Concentration Data from Certain
Calculations and Analyses for Purposes Other than Retrospective
Determinations of Attainment of the NAAQS, which will describe the
appropriate additional pathways that we intend to make available for
data exclusion for some monitoring data applications (e.g., predicting
future attainment that is the basis for approval of an attainment
demonstration in the SIP for a nonattainment area, preparing required
air quality analyses in an application for a PSD permit or preparing
required air quality analysis for the purposes of transportation
conformity). The EPA intends to post the draft guidance on the
exceptional events Web site at http://www2.epa.gov/air-quality-analysis/treatment-data-influenced-exceptional-events and expects to
finalize the document when we finalize these rule revisions. We intend
that this guidance will recommend exclusion of data for PSD,
transportation conformity and certain other applications in any
situation in which exclusion has already been approved under the
Exceptional Events Rule, as well as in applications in which the facts
would support exclusion under the criteria of the Exceptional Events
Rule even if an EPA determination has not yet been made under the
Exceptional Events Rule and in some other situations that we will
describe in the guidance.
D. What is a natural event?
1. Current Situation
The CAA definition at section 319(b)(1)(iii) specifies that an
exceptional event ``is an event caused by human activity that is
unlikely to recur at a particular location or a natural event.'' Thus,
the statute limits the expected occurrence frequency of an event caused
by human activity as ``unlikely to recur'' but does not limit the
occurrence frequency of a natural event. Natural events may recur, even
frequently.\33\ Air agencies can request, and the EPA can agree, to
exclude data affected by a natural event if an air agency's
demonstration meets the other requirements of the Exceptional Events
Rule. Thus, considering whether an event was a natural event or was
caused by human activity is important to the content within and to the
approval of a demonstration.
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\33\ See as examples, Hawaii's exceptional events demonstration
for volcanic activity affecting PM2.5 concentrations in
2011-2012 and California Air Resources Board's demonstration for
wildfire events affecting PM2.5 concentrations in 2008,
both available at http://www2.epa.gov/air-quality-analysis/exceptional-events-submissions-table.
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As previously discussed, to be considered an exceptional event, an
event, whether natural or anthropogenic in origin, must affect air
quality at the affected monitor. 40 CFR 50.1(k) defines a natural event
as one in which human activity plays little or no direct causal role in
the generation of emissions. In some cases, such as stratospheric ozone
intrusions or volcanic eruptions, the EPA recognizes that human
activity plays no role in the magnitude of emissions or level of air
pollution that occurs. In other cases, past or current human activity
does influence the magnitude of emissions and hence the level of air
pollution. For example, in high wind dust events, the pollution from
the event may originate from a mixture of natural lands (e.g.,
undisturbed soil), soil that has been disturbed by human activity and
has been made more prone to wind-generated dust emissions (e.g., recent
construction activity), and materials accumulated and stored by human
activity (e.g., sand and gravel facilities).
The EPA generally considers human activity to have played little or
no direct role in causing emissions if anthropogenic emission sources
that contribute to the event emissions are reasonably controlled at the
time of the event, regardless of the magnitude of emissions generated
by these reasonably controlled anthropogenic sources and regardless of
the relative contribution of these emissions and emissions arising from
natural sources in which human activity has no role.34 35
Thus, the event could be considered a natural event. In such cases, the
EPA applies the reasonable interpretation that the anthropogenic source
had ``little'' direct causal role. If anthropogenic emission sources
that contribute to the event emissions can be reasonably controllable
but reasonable controls were not implemented at the time of the event,
then the event would not be considered a natural event. The EPA
explained this concept in the preamble to the 2007 Exceptional Events
Rule.\36\ However, the rule text did not reflect the identified
concept. This has resulted in some regulatory uncertainty as to whether
the EPA's interpretation of the CAA and the 2007 Exceptional Events
Rule as described here is appropriate.
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\34\ For example, if an area affected by a high wind dust event
has adequate rules or ordinances for sources of windblown dust
(e.g., rules that establish restrictions for operating vehicles on
unpaved property, rules that control windblown dust emissions
associated with lands disturbed by construction, earthwork and land
development) and the air agency can provide evidence of
implementation and enforcement, then the EPA would generally
consider human activity to have played little or no direct causal
role in causing the event-related emissions.
\35\ The EPA considers wildfires to be natural events even
though some wildfires are initiated by human actions and to some
degree the frequency and scale of wildfires may be influenced by
prior land management practices. The EPA believes this
interpretation best implements the Congressional intent and is a
more appropriate approach than expecting air agencies to determine
the initial cause of each wildfire of interest and classifying it as
natural or anthropogenic based on that cause. In addition, land
owners and managers and government public safety agencies are
strongly motivated to reduce the frequency and severity of human-
caused wildfires and the EPA believes they can be presumed to make
reasonable efforts to avoid them.
\36\ 72 FR 13565-13566 (March 22, 2007).
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2. Proposed Changes
Based on the discussion above, the EPA proposes to revise the
definition of natural event to clarify that anthropogenic emission
sources that contribute to the event emissions that are reasonably
controlled do not play a ``direct role'' in causing emissions. Thus, an
event with a mix of natural emissions and reasonably controlled human-
affected emission sources may be considered a natural event. However,
an event resulting from only reasonably controlled human affected
emissions may not be considered a natural event. This proposal is
consistent with statements made in the preamble to the 2007 Exceptional
Events Rule, and including it in the rule text provides more regulatory
certainty to all parties.
When addressing the not reasonably controllable or preventable
criterion for this same event type consisting of a mix of natural
emissions and human-affected emission sources (e.g., a high wind event
affecting both open desert areas and urbanized lands), air agencies
must assess reasonable controls for both the contributing natural and
anthropogenic sources. While air agencies must ``assess'' reasonable
controls for most types of contributing natural sources because this
statutory factor applies to all events, they do not necessarily need to
implement controls for these same sources. Additionally, because the
rule revisions propose a categorical presumption of not reasonably
controllable for wildfires and large-scale, high-energy and/or sudden
high wind dust events, ``assessing'' these events would involve
referencing the appropriate regulatory citation. As we explain in more
detail in section V.E.2, for natural sources, we do not think that air
agencies need to have implemented any controls for windblown dust from
never-disturbed,
[[Page 72855]]
large-scale natural landscapes. Therefore, lack of controls on natural
sources that contribute to event-related emissions would not disqualify
the event from being considered as an exceptional event. When assessing
the contribution from anthropogenic sources, similar to the analyses
involved in determining whether these same sources play a ``direct
role'' in causing event-related emissions, the air agency should
identify the contributing anthropogenic sources, explain why the
controls specified in rules or ordinances are reasonable, and provide
evidence of implementation and enforcement. Also as explained in
section V.E.2, in our view an event is ``not reasonably controllable''
if an exceedance or violation occurs even when reasonable controls were
actually in place and any further control would have been beyond what
was reasonable. The EPA intends to consider these aspects when applying
the concept of ``reasonable controls'' on anthropogenic sources to
determine whether the event can be considered a natural event and to
evaluate the not reasonably controllable or preventable criterion.
With respect to determining whether anthropogenic emission sources
that contribute to the event emissions were reasonably controlled at
the time of the event, the EPA also proposes to revise the definition
of a natural event to indicate that the reasonableness of available
controls should be assessed as of the date of the event. The EPA does
not believe that information related to the cost and effectiveness of
control measures, or related to the frequency of events, that became
available to the air agency after the date of the event should affect
the assessment of whether anthropogenic sources were reasonably
controlled and thus the identification of an event as natural or caused
by human activity.
When addressing this criterion as part of an exceptional events
demonstration, the EPA recommends that the submitting air agency
clearly identify whether the event is natural or was a human activity
that is unlikely to recur at a particular location. If purely natural
(e.g., lightning-ignited wildfire, volcanic or seismic activity,
stratospheric ozone intrusion), the EPA recommends that the submitting
air agency identify the purely natural status in the ``human activity/
natural event'' section of its demonstration; provide the type/source
of event, the resulting emissions, and the documented frequency of the
event; and affirmatively state that in characterizing the event, the
submitting air agency has satisfied the human activity/natural event
criterion.
E. Technical Criteria for the Exclusion of Data Affected by Events
As described in section V.B, the EPA proposes to return to the core
statutory elements and implicit concepts of CAA section 319(b): That
the event affected air quality in such a way that there exists a clear
causal relationship between the specific event and the monitored
exceedance or violation, the event was not reasonably controllable or
preventable, and the event was caused by human activity that is
unlikely to recur at a particular location or was a natural event. All
exceptional events demonstrations, regardless of event type or relevant
NAAQS, must address each of these technical criteria. This section
describes the EPA's proposals for rule revisions and guidance regarding
each of these technical criteria. Section V.G discusses additional
process-related components of exceptional events demonstration
packages.
1. Human Activity Unlikely To Recur at a Particular Location or a
Natural Event
The concept of recurrence applies to human activity; the statements
in this section are not relevant for natural events. Section V.D
includes a detailed discussion of a ``natural event.''
a. Current Situation
According to both the regulatory and statutory definitions, an
exceptional event must be ``an event caused by human activity that is
unlikely to recur at a particular location or a natural event''
(emphasis added). For clarity, in this section, the EPA focuses on the
language ``unlikely to recur at a particular location.''
The ``unlikely to recur at a particular location'' requirement of
CAA section 319(b) does not define ``unlikely to recur.'' Thus, this
language requires interpretation on a case-by-case or event type-by-
event type basis. The term ``unlikely'' implies consideration of the
expected future frequency of events similar to the event that has
already happened, but does not convey any particular benchmark for what
frequency should be low enough to be considered ``unlikely.'' Also, the
term ``at a particular location'' requires interpretation, as it could
refer to the exact area or only to the general area of the event, to
the location of the ambient monitoring station or stations that were
affected by the event or to the combination of both.
The EPA's 1986 Guideline on the Identification and Use of Air
Quality Data Affected by Exceptional Events stated that events can be
considered exceptional if they are not expected to ``recur routinely at
a given location.'' \37\ This document did not further define or give
specific examples of ``routinely.''
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\37\ Guideline on the Identification and Use of Air Quality Data
Affected by Exceptional Events (the Exceptional Events Policy), U.S.
EPA, OAQPS, EPA-450/4-86-007, July 1986.
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The preamble to the 2007 Exceptional Events Rule did not provide
specific guidance on the unlikely to recur criterion, except to say
that recurrence is event-specific and should be assessed on a case-by-
case basis and that in the particular case of prescribed fires a
comparison to the natural fire return interval is a relevant
consideration for this criterion.
The CAA section 319(b) and the 2007 Exceptional Events Rule do not
specifically address temporary, but multi-day or multi-year activities,
such as construction projects. However, Question 16 in the Interim Q&A
document noted that the 2007 Exceptional Events Rule does not
explicitly place a limit on the duration of a single event and that a
submitting agency could make a showing that a prolonged activity (e.g.,
a multi-year road construction project) is a single event that is not
likely to recur at the location in question. The Interim High Winds
Guidance document addressed recurrence for high wind events, as
summarized in section V.F.4 of this document. Other than this, the
Interim Exceptional Events Implementation Guidance did not provide any
specific guidance on the unlikely to recur criterion.
b. Proposed Changes
While we believe that it is appropriate to consider recurrence to
be event-specific and for the unlikely to recur criterion to be
assessed on a case-by-case basis, we also believe that this proposed
action presents an opportunity to clarify certain points. This section
provides general clarifications with respect to the meaning of
``unlikely to recur.'' Section V.F.2 addresses this criterion for
wildland fires (specifically prescribed fires on wildland) and section
V.F.4 specifically addresses this criterion for high wind dust events.
Also, under CAA section 319(b) and the 2007 Exceptional Events Rule,
air pollution related to source noncompliance is not an exceptional
event regardless of its frequency.
The EPA proposes, as guidance, to recommend the following
boundaries on the interpretation of the unlikely to recur criterion. If
an event type has not previously occurred within a given air
[[Page 72856]]
quality control region (AQCR) \38\ in the 3 years preceding the
submittal of an exceptional events demonstration, the EPA will consider
this to be a ``first'' event and will generally consider it to be
unlikely to recur in the same location. Similarly, a ``second'' event
within the 3 years preceding the submittal of an exceptional events
demonstration would also generally be considered unlikely to recur in
the same location. If there have been two prior events of a similar
type within a 3-year period in an AQCR, that would generally indicate
the third event, for which the demonstration is being prepared (or
would be prepared), does not satisfy the ``human activity that is
unlikely to recur at a particular location'' criterion and, thus, would
not qualify as an exceptional event. The terms ``first'' and ``second''
events refer to events that affect the same AQCR, even if they have not
affected the same monitor.\39\ This proposed guidance is consistent
with the approach taken to recurrence in our Interim High Winds
Guidance document in which we identified non-recurring events as being
less than one event per year in a given area.\40\ In the Interim High
Winds Guidance, we did not define area other than to differentiate
areas by attainment status or jurisdiction (i.e., intrastate versus
interstate or international).
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\38\ Air Quality Control Regions are defined in 40 CFR part 81,
subpart B, Designation of Air Quality Control Regions.
\39\ The EPA will consider previously flagged exceedances within
AQS with their associated descriptions to be ``events'' regardless
of whether the EPA has received or acted on event demonstrations.
The EPA also notes that a single event could influence
concentrations on multiple days.
\40\ See footnote 27 in table 2 of Interim Guidance on the
Preparation of Demonstrations in Support of Requests to Exclude
Ambient Air Quality Data Affected by High Winds Under the
Exceptional Events Rule. U.S. EPA. May 2013. Available at http://www2.epa.gov/sites/production/files/2015-05/documents/exceptevents_highwinds_guide_130510.pdf.
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The EPA solicits comment on this proposed guidance regarding
recurrence at a particular location, specifically the use of an AQCR to
define the bounds for an area subject to event recurrence given that
some AQCRs may be quite large. The EPA also solicits comments on
whether this benchmark of three events in 3 years should be
incorporated into the rule text, rather than being provided only as
guidance.
The EPA proposes, as guidance, that to satisfy the documentation
requirements for the ``human activity that is unlikely to recur at a
particular location'' criterion, the submitting air agency should
document and discuss, in a distinct ``human activity/natural event''
section of the demonstration, the type/source of event (e.g., a
particular type of chemical spill or other industrial accident or a
fire in a particular type of structure), the resulting emissions and
the documented frequency of the event in the prior 3 years. The
demonstration should affirmatively state that in characterizing the
event, the submitting air agency has satisfied the ``human activity
unlikely to recur at a particular location or a natural event''
criterion.
2. Not Reasonably Controllable or Preventable
The CAA section 319(b) does not restrict the not reasonably
controllable or preventable criterion to apply only to events caused by
human activity. It also applies to natural events. Accordingly, the
Exceptional Events Rule applies this criterion to all types of events.
This section discusses the criterion in general terms. We discuss the
criterion's applicability to fire events on wildland in section V.F.2
and to high wind dust events in section V.F.4.
a. Current Situation
As noted in section V.B of this document, the definition of an
exceptional event at 40 CFR 50.1(j) repeats the CAA definition and
includes the requirement at section 319(b)(1)(A)(ii) that an
exceptional event, whether natural or caused by human activity, is one
that ``is not reasonably controllable or preventable.'' Neither the
rule text of the 2007 Exceptional Events Rule nor the preamble to the
final rule provided additional clarification regarding this statutory
element. Rather, the preamble to the final rule stated, ``[w]e are not
finalizing more detailed requirements for determining when an event is
`not reasonably controllable or preventable' because we believe that
such determinations will necessarily be dependent on specific facts and
circumstances that cannot be prescribed by rule.'' \41\ While we
maintain that determining whether or not an event is not reasonably
controllable or preventable is event-specific and necessarily requires
judgment by the air agency and the EPA, we also believe that some
concepts regarding this criterion are broadly applicable.
---------------------------------------------------------------------------
\41\ 72 FR 13564 (March 22, 2007).
---------------------------------------------------------------------------
To begin, the statutory requirement that an exceptional event is
one that ``is not reasonably controllable or preventable'' contains two
factors: Prevention and control. Within the context of the Exceptional
Events Rule, we intend that ``prevent'' means to stop or avert the
event, and ``control'' means to reduce the magnitude and impact of
event-related emissions. We interpret CAA section 319(b) to mean that
to qualify as an exceptional event, the event cannot be reasonably
preventable and cannot be reasonably controllable, rather than that
only one of the two elements must be satisfied. It would be contrary to
the emphasis of section 319(b) on protection of public health if there
were no requirement for reasonable control for an event merely because
the event could not be reasonably prevented from happening. It is
possible for an event to not be reasonably preventable, but to be
reasonably controllable.\42\ In this case, if emissions were reasonably
controlled, then the event could be considered for concurrence as an
exceptional event. It is also possible that an event be neither
preventable nor its air quality impacts to be controllable to any
degree, such as potential increases in SO2 concentrations
associated with volcanic eruptions.
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\42\ For example, in section V.F.2, we propose that under
certain circumstances a prescribed fire may not be reasonably
preventable because of the safety or ecosystem benefits that would
be foregone, but emissions and air quality impacts from the fire may
be reasonably controllable through the application of basic smoke
management practices.
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The EPA considers the statutory requirement that an exceptional
event be ``not reasonably preventable'' to mean that if a set of
prevention measures should reasonably have been in place for
anthropogenically-influenced emission sources that contribute to the
event emissions, then those measures must have been in place for the
event to qualify as an exceptional event under the Exceptional Events
Rule. Similarly, we consider the statutory requirement that an
exceptional event be ``not reasonably controllable'' to mean that if a
set of control measures should reasonably have been in place for
emission sources that contribute to the event emissions, then those
controls must have been in place for the event to qualify as an
exceptional event under the Exceptional Events Rule. Satisfying the not
reasonably controllable element necessitates a showing of reasonable
controls. Whether a set of controls constitutes ``reasonable controls''
is event-, time-, and place-dependent, and involves judgment by the air
agency when preparing the demonstration and by the EPA when reviewing
the demonstration.\43\ We stated in the
[[Page 72857]]
Interim Exceptional Events Implementation Guidance, and we reiterate in
this action, that it may not be reasonable to apply any prevention or
control efforts for some events.
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\43\ The EPA has many resources to help states identify
appropriate control technologies and includes links to some of these
sources on the Control Strategies Web site available at http://www3.epa.gov/airquality/aqmportal/management/control_strategies.htm.
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In the course of implementing the 2007 Exceptional Events Rule,
both the EPA and air agencies have expressed concern regarding the
determination of ``reasonable'' prevention or control efforts for
particular events. When an air agency prepares a demonstration, it
attempts to show that whatever efforts were made were all that were
reasonable to make. When the EPA reviews a demonstration, we are
responsible for determining if the demonstration is credible and
convincing. The EPA has been unable to make this determination
regarding reasonableness for some demonstrations because the content
regarding the use and implementation of control measures is
insufficient. Given the elasticity of the concept of ``reasonable,'' it
is not surprising that disagreements have arisen. We have in the past
few years, particularly since issuing the Interim Exceptional Events
Implementation Guidance, worked with states to reach mutual
understandings of what efforts are reasonable and to have those efforts
in place before events happen. However, situations will likely occur in
the future, as they have in the past, in which an assessment of
reasonableness must be made retrospectively, when it is too late for
the air agency to have applied greater efforts. The EPA recognizes that
our action on the air agency's demonstration may have important
regulatory consequences for the area in question.
The EPA has stated that for all types of events, we consider
reasonableness in light of the technical information available to the
air agency at the time the event occurred. An air agency ``caught by
surprise'' by an event of a given type (or by an unexpected number of
such events in a period over which NAAQS compliance is evaluated,
typically 3 years) should not be expected to have implemented the same
controls prior to an event as an air agency that has been aware that
events of a certain type occur with regularity and cause NAAQS
exceedances or violations. The EPA anticipates that nonattainment (or
maintenance) areas have technical information needed to understand
those measures that constitute reasonable control of anthropogenic
sources in their jurisdiction for recurring events of the type(s) that
cause or contribute to nonattainment (or that did previously). In
contrast, the EPA generally does not expect areas identified as
attainment, unclassifiable/attainment or unclassifiable for a NAAQS to
have the same understanding or to have adopted the same level of event-
relevant controls as areas that are nonattainment (or maintenance) for
the same NAAQS. Also, if an area has been recently designated to
nonattainment but is still developing its SIP and has not yet reached a
deadline to implement controls, the EPA expects the level of controls
that is appropriate for that planning stage.\44\ Regardless of
attainment status or natural/anthropogenic source contribution, each
demonstration package should address the question of reasonable
controls within the not reasonably controllable or preventable portion
of the demonstration.
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\44\ The CAA provides different timeframes for developing and
implementing SIPs depending on the NAAQS and the nonattainment
area's classification (e.g., severity of the nonattainment problem).
The EPA recognizes that within the SIP development and
implementation process, some measures may be implemented relatively
quickly (e.g., transportation conformity, new source review) whereas
other programs, such as development or rules for particular source
types, can take time and involve state legislative processes.
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The not reasonably controllable or preventable criterion is a
source of particular complexity when an event occurs outside the
jurisdiction of the state that is requesting that data be excluded. The
area outside a state's jurisdiction may be in an area of Indian
country, in another state, or in a foreign country. For these cases,
the air agency requesting data exclusion, and other government
authorities in the state, generally do not have regulatory authority
over those who might have been able to prevent or control the event.
Therefore, the EPA believes that event-related emissions that originate
outside of the boundaries of the state within which the concentration
at issue was monitored are generally ``not reasonably controllable or
preventable'' even if no party has made any effort to control or
prevent them. To date, we have advised air agencies that an exceptional
events demonstration for such a case must nevertheless explicitly
address the question of reasonable efforts towards prevention and
control. For these situations, we have suggested template language to
the effect that satisfying the not reasonably controllable or
preventable element could consist of an air agency stating that because
the event occurred outside of its jurisdiction, the not reasonably
controllable or preventable criterion is satisfied.
Because the reasonableness of controls for event-related emissions
is case-specific, the EPA has not issued guidance that particular
controls are reasonable or are not reasonable. The Interim High Winds
Guidance document indicates sources of information that identify
measures that an air agency and the EPA should consider. In that
guidance, we said that if the EPA has approved a SIP revision to
windblown dust controls within the past 3 years of the event, then an
air agency can rely on the SIP-approved controls to satisfy a portion
of a ``prospective controls analysis.'' \45\ By this, we meant that we
would agree with the air agency that for any high wind dust events in
the next 3 years, implementation of the controls in the SIP would be
sufficient to establish that those events are not reasonably
controllable. In our discussions during the development of these
proposed revisions of the Exceptional Events Rule, air agencies have
urged us to give more deference to relevant controls in the EPA-
approved SIPs. Some air agencies have recommended that we always accept
that the controls in the approved SIP are all that should have
reasonably been in place at the time of the event (and/or that we
accept no controls if there are no controls in the approved SIP). We
understand at least some of those recommending this approach to mean it
to apply both to nonattainment and maintenance areas that have approved
attainment or maintenance plans and to areas whose SIPs have been
approved only with respect to less specific infrastructure SIP
requirements.
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\45\ Interim Guidance on the Preparation of Demonstrations in
Support of Requests to Exclude Ambient Air Quality Data Affected by
High Winds Under the Exceptional Events Rule. U.S. EPA. May 2013.
Available at http://www2.epa.gov/sites/production/files/2015-05/documents/exceptevents_highwinds_guide_130510.pdf.
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b. Proposed Changes
The EPA generally plans to continue its past interpretations with
respect to the ``not reasonably controllable or preventable''
criterion. We propose to codify in regulatory language key aspects of
these past interpretations to reduce uncertainty for air agencies and
other parties. Specifically, we are proposing changes to the text of
the Exceptional Events Rule to indicate that:
The not reasonably controllable or preventable criterion
has two prongs, prevention and control. An air agency must demonstrate
that an event was both not reasonably preventable and not reasonably
controllable.
An event is not reasonably preventable if reasonable
measures to prevent the event were applied at the time of the event.
[[Page 72858]]
An event is not reasonably controllable if reasonable
measures to control the impact of the event on air quality were applied
at the time of the event.
The reasonableness of measures is case-specific and is to
be evaluated in light of information available at the time of the
event.
No case-specific justification is needed to support the
``not reasonably controllable or preventable'' criterion for emissions-
generating activity that occurs outside of the boundaries of the state
(or tribal lands) within which the concentration at issue was
monitored.\46\
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\46\ Under the CAA, the EPA generally considers a state (not
including areas of Indian country) to be a single responsible actor.
Accordingly, neither the EPA nor the 2007 Exceptional Events Rule
provides special considerations for intrastate scenarios when an
event in one county affects air quality in another county in the
same state, assuming that the event occurs on land subject to state
authority (versus tribal government authority). The EPA expects
controls appropriate for the designation status of the county (or
portion of the county) in which the emissions originate.
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With regard to the last of these proposed rule text changes, the
EPA maintains that it is not reasonable to expect the downwind air
agency (i.e., the state or tribe submitting the demonstration) to have
required or persuaded the upwind foreign country, state or tribe to
have implemented controls on sources sufficient to limit event-related
air concentrations in the downwind state or tribal lands, nor does the
EPA believe that Congress intended to deny the downwind state or tribe
relief in the form of data exclusion within the context of the
Exceptional Events Rule. Submitting (downwind) air agencies will,
however, need to assess potential contribution from local and state-
wide sources and submit evidence and statements supporting the other
exceptional events criteria (i.e., clear causal relationship and human
activity unlikely to recur or a natural event).
In addition to proposing to codify the five current interpretations
listed above, with regard to this criterion, we are proposing and
requesting comments on changes from our current interpretations and
changes in the rule text that are explained below in more detail.
Natural Events and Natural Sources. The not reasonably controllable
or preventable criterion applies to natural events, including natural
sources and any contributing anthropogenic sources and activities.\47\
The EPA proposes, as guidance, that to satisfy the not reasonably
controllable or preventable criterion for natural events, air agencies
should identify in their demonstration the origin and evolution of the
natural event, describe any local efforts to prevent the event and
explain how any efforts to limit the duration, intensity or extent (and
thus the emissions) from the event were reasonable.
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\47\ An event with a significant contribution from
anthropogenically-influenced emissions sources that have not
themselves been reasonably controlled cannot be considered a natural
event subject to this provision.
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Large-scale natural landscapes, such as deserts, are one type of
natural source from which emissions can originate and contribute to
event-related emissions. We propose, as guidance for these types of
natural sources, that air agencies would not need to have implemented
any controls for windblown dust from never-disturbed, large-scale
natural landscapes. If such a landscape is the only source of wind-
blown dust, the EPA would consider the event in this scenario to be not
reasonably controllable or preventable regardless of the past frequency
of similar events. Other such cases include volcanic releases of
SO2 and stratospheric ozone intrusions. In these cases, the
air agency should affirmatively state that the not reasonably
controllable or preventable criterion is satisfied by the fact that the
natural event was of a character that could not have been prevented or
controlled and that there were no contributions of event-related
emissions from anthropogenic sources.
We also propose, as guidance, for events other than high wind dust
events and wildfire on wildland (for which the proposed rule revisions
take an equivalent approach), to consider the direct effects of remote,
large-scale, high-energy and/or sudden natural events to generally be
not reasonable to prevent or control.\48\ This concept, as it relates
specifically to proposed rule changes addressing high wind dust events,
is discussed in more detail in section V.F.4. Section V.F.2.c discusses
how the same concept relates to proposed rule changes addressing the
``not reasonably controllable or preventable'' criterion for wildfire
on wildland.
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\48\ By ``remote'' events, we mean events that occur in
locations where the application of control measures is either cost-
prohibitive or presents unreasonable risks to worker safety because
of the distance of the source from logistical staging areas, or
absence of roads and/or location on rough or steep terrain. By
``large-scale'' we mean a regional event that involves a significant
expanse of land and/or affects all/most monitors in an area. ``High-
energy'' means an event involving levels of kinetic energy that
feasible human efforts cannot absorb or redirect. Example large-
scale and/or high-energy events might include seismic events,
hurricanes, tornadoes and ``haboobs'' in the southwest where
sustained wind speeds can exceed 40 mph and generate walls of dust
several miles wide and more than a mile high.
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There may, however, be natural events or activities associated with
the clean-up following a natural event where some type of control
effort would be reasonable. For example, while an initial volcanic dust
event may not be controllable or preventable, it may be reasonable to
implement a street cleaning program to control the subsequent re-
entrainment of dust deposited on roadways after the eruption. Also, air
quality impacts during the active period of a weather disaster event
generally cannot be prevented or controlled and it would be reasonable
for no effort to have been made to do so. However, air agencies should
apply reasonable controls, as applicable, in the recovery period after
the event (e.g., during the removal or incineration \49\ of debris
following a hurricane or tornado). There may also be smaller scale
natural sources and events for which some control actions would be
reasonable. We request comment on additional general and event-specific
recommendations that would be consistent with the CAA and the revised
Exceptional Events Rule regarding natural events and sources that the
EPA could include in guidance to provide more certainty and allow air
agencies to efficiently prepare demonstrations.
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\49\ When addressing reasonable controls for the incineration of
debris associated with the recovery period following a natural
disaster, air agencies may want to consider, as appropriate, the
basic smoke management practices discussed in more detail in section
V.F.2.d of this proposal.
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The Role of Past Occurrences. When assessing the controls that
should reasonably have been in place in light of information available
at the time of the event, both the air agency and the EPA should
consider the then-known frequency and severity of recurring events of
the same type as both characteristics should affect decisions regarding
those measures that constitute reasonable controls. A measure may not
be reasonable when the event type and severity was known to occur
infrequently, but such measures may be reasonable if that event type
and severity occurs frequently, because there are greater (more
frequent) benefits to balance against the cost of implementation. If
the event was the area's first experienced event of this type, then the
submitting air agency would note that fact. The air agency could then
rely on measures in the SIP and other controls in place at the time of
the event, if any, to satisfy the not reasonably controllable or
preventable criterion because, at the time of the event, the air agency
did not have a basis for understanding the possible need for better
controls for this type of event. If, however, the area has
[[Page 72859]]
previously experienced events of the type that are the focus of the
demonstration, then the air agency has a basis for understanding the
possible need for better controls.\50\
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\50\ Because a state is considered a single responsible entity
for purposes of SIP development and implementation, there may be
state governmental authorities whose knowledge of the need for an
availability of controls at the time of the event is also relevant,
particularly for in-state sources outside the geographic area
covered by the air agency's regulatory authority.
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We note that this consideration of past recurrence when determining
what controls would have been sufficient to satisfy the not reasonably
controllable or preventable criterion is not the same as the
consideration of the likelihood of future recurrence for the purposes
of the unlikely to recur criterion. Past experiences are a general
guide to future likelihood but the EPA recognizes that future
recurrence may follow a different pattern and may necessitate new
measures to prevent events of a given type.
The Role of the EPA-approved SIP as the Benchmark for Reasonable
Measures--In General. As already mentioned, some air agencies have
urged us to defer to relevant controls in EPA-approved SIPs as always
sufficient to satisfy the not reasonably controllable or preventable
criterion. The EPA could conceivably give ``deference'' to several
different types of SIPs. CAA section 110(a)(1) and 110(a)(2) requires
every state to develop and submit to the EPA an ``infrastructure SIP''
for each NAAQS within 3 years of the promulgation of a new or revised
NAAQS. Infrastructure SIPs address a number of CAA requirements,
including the requirement to contain emission limits to ensure
attainment and maintenance of a NAAQS. However, under the EPA's
interpretation of these CAA sections, infrastructure SIPs are not
required to include attainment or maintenance demonstrations and are
not required to demonstrate that the controls on particular sources are
``reasonable.'' Thus, in general, EPA-approved infrastructure SIPs do
not necessarily constitute a robust assessment of those controls that
are reasonable to have in place to address air quality impacts from
particular types of events that may become the focus of exceptional
events demonstrations.
In contrast, states with areas designated as nonattainment for a
NAAQS must prepare attainment plan SIPs, which must include an
attainment demonstration and reasonably available control measures
(RACM), among other requirements.\51\ Attainment plans for serious
PM10 or PM2.5 areas must also contain best
available control measures (BACM). When a nonattainment area reaches
attainment, it may be redesignated to maintenance area status if it has
implemented all applicable nonattainment area requirements and obtains
the EPA's approval for a maintenance plan for a 10-year period. Thus,
in both maintenance and nonattainment areas with approved attainment
plan SIPs, the air agency and the EPA will have considered what
controls are necessary and reasonable to provide for attainment, based
on information available at the time of plan development and approval.
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\51\ Marginal ozone nonattainment areas are exceptions because
they are not required to submit attainment demonstrations.
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Taken to its furthest limit, the deference recommended by some air
agencies would mean that the EPA would always approve a state air
agency assertion that the control measures in a SIP that has received
full approval by the EPA as meeting currently applicable requirements
related to the event-relevant NAAQS constituted the reasonable set of
controls for the event in question and thus the event was not
reasonably controllable or preventable. We believe that this degree of
deference could, in some cases, result in the approval for data
exclusion contrary to CAA requirements. Deference to the measures in an
EPA-approved SIP is not always appropriate because EPA approval at some
time in the past does not necessarily mean that (1) the control
measures in a current SIP address all event-relevant sources of current
importance, (2) the control measures that were considered by the air
agency and the EPA at the time the EPA last approved the SIP are the
same measures that were known and available at the time of a more
recent event, or (3) that conditions in the area have not changed in a
way that would affect the approvability of the same SIP if it newly
needed the EPA's approval. However, we believe that it may be
consistent with the CAA to revise the Exceptional Events Rule to
identify the conditions under which the EPA and air agencies can rely
upon measures in an EPA-approved SIP to satisfy the not reasonably
controllable or preventable criterion. To clarify these scenarios, the
EPA is proposing, and discusses below, various combinations of rule
provisions and guidance for areas of different designation status.
The best time for air agency and federal officials to exchange both
technical information and views on the balance between costs and
benefits related to the sufficiency of reasonable controls is before an
event happens. To avoid the EPA's retrospective second guessing of an
air agency's consideration of information available to it before an
event occurs, we have identified and described below several proposals,
which would apply when an affected air agency and the EPA have not
reached a mutual understanding regarding reasonable controls prior to
an event.
The Role of the EPA-approved SIP in Nonattainment and Maintenance
Areas. To satisfy the not reasonably controllable or preventable
criterion for nonattainment or maintenance areas, the EPA proposes to
establish by rule a non-rebuttable presumption that, during a 5-year
window (or, alternatively another appropriate timeframe) following
approval of an attainment plan or maintenance plan SIP during which no
subsequent new obligation for the air agency to revise the SIP has
arisen, the control measures included in the SIP that are specific to
the relevant pollutant, sources and event type are sufficient for
purposes of the not reasonably controllable or preventable
criterion.\52\ The EPA believes that 5 years is an appropriate
timeframe upon which to rely for SIP deference for several reasons. As
noted earlier, deference to the measures in an EPA-approved SIP is not
always appropriate because EPA approval at some time in the past does
not necessarily mean that (1) the control measures in a current SIP
address all event-relevant sources of current importance, (2) the
control measures that were considered by the air agency and the EPA at
the time the EPA last approved the SIP are the same measures that were
known and available at the time of a more recent event, or (3) that
conditions in the area have not changed in a way that would affect the
approvability of the same SIP if it newly needed the EPA's approval. A
5-year window provides a reasonable timeframe under which to evaluate
the above-identified potential changes. Additionally, as we discuss in
section V.E.3 of this proposal, we encourage the use of 5 years of data
when developing analyses to support the clear causal relationship
criterion because we believe that 5 years of ambient air data represent
the range of ``normal'' air quality.
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\52\ A request for data exclusion must also show that the event
was not a result of noncompliance with any existing state or local
laws or rules that have not been incorporated into the SIP.
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The EPA would evaluate the not reasonably controllable or
preventable
[[Page 72860]]
criterion on a case-by-case basis for those demonstrations involving an
event affecting a nonattainment or maintenance area with a SIP last
approved more than 5 years prior to the submittal of the subject
demonstration. Because the issue of deference to a SIP is most often
applicable for high wind events, section V.F.4 further illustrates this
proposal.
The Role of the EPA-approved SIP in Attainment, Unclassifiable/
Attainment or Unclassifiable Areas. Attainment, unclassifiable/
attainment and unclassifiable areas should have EPA-approved
infrastructure SIPs in place that the EPA approved within a few years
following the promulgation of a new or revised NAAQS. Infrastructure
SIPs for the 1987 PM10 NAAQS are likely to be many years
old, while infrastructure SIPs for ozone, PM2.5, 1-hour
SO2 and 1-hour NO2 have been approved more
recently.\53\ In addition to the EPA-approved infrastructure SIPs,
these areas may have in place other relevant state or local laws and
rules, a natural events action plan, an SMP and/or other programs based
on voluntary participation.
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\53\ The NAAQS not mentioned here have rarely presented
exceptional events issues.
---------------------------------------------------------------------------
Because the development and the EPA's review of infrastructure SIPs
typically do not involve a robust assessment of needed measures to
prevent or control the effects of particular types of events and
because even in the absence of a pending SIP call the SIP may not
reasonably address events of importance, the EPA does not propose to
establish in rule text or in guidance any form of general deference to
the SIP in attainment, unclassifiable/attainment or unclassifiable
areas. The EPA will review exceptional events demonstrations on a case-
by-case basis, applying the Exceptional Events Rule and the EPA's
guidance. A case-by-case review may conclude that the measures that
were in place under the SIP, a natural events action plan, an SMP or
other state or local programs were sufficient or insufficient to
satisfy the not reasonably controllable or preventable criterion.
If the air agency has historically documented recurring events,
then the EPA would expect the submitting air agency to identify any
anthropogenic emission sources that contribute to the event emissions
and specifically document the controls that were in place for these
sources at the time of the event. It is possible that the air agency
may not be able to make a sufficient showing for the not reasonably
controllable or preventable criterion if it has not implemented
reasonable controls for anthropogenic sources that contribute to
recurring events. In this case, the EPA Regional office may not be able
to concur with an air agency's request for data exclusion. If the air
agency has no such control plans and has no history of recurring
events, then the air agency would note this in the not reasonably
controllable or preventable portion of its demonstration and would rely
on the fact that at the time of the event, the air agency did not have
a basis for understanding the possible need for better reasonable
controls.
Note that in section V.G.7 of this proposed action, ``Timing of the
EPA's Review of Submitted Demonstrations,'' the EPA proposes to work
with air agencies to prioritize exceptional events determinations that
affect near-term regulatory decisions. In an attainment,
unclassifiable/attainment or unclassifiable areas, the only likely non-
discretionary regulatory action would be an initial designation under a
new or revised NAAQS. Possible discretionary actions include a
redesignation under a long-standing NAAQS or a SIP call. Under its
planned prioritization approach, the EPA would not expect to act on
demonstrations for events in an attainment, unclassifiable/attainment
or unclassifiable areas unless the area could become nonattainment
under a new or revised NAAQS, the area is the subject of a planned EPA
discretionary redesignation for a long-standing NAAQS where the
approval of a demonstration affects the basis for the redesignation, or
the area becomes the subject of another EPA discretionary action (e.g.,
a SIP call at the initiative of the EPA or in response to a petition)
that hinges on the approval of a demonstration.
The Role of Prior Communications with the EPA in Case-Specific
Assessments for Not Reasonably Controllable or Preventable. As already
stated, the EPA believes that an air agency must include in its
exceptional events demonstration a retrospective assessment of whether
an event was not reasonably controllable or preventable. The air agency
should base this assessment on information available to relevant
authorities (e.g., the air agency submitting the demonstration and
potentially other government authorities in the state, for example an
upwind air quality control district where the event occurred) that
could have implemented measures to prevent or control the event and its
effects prior to and during the event. We are proposing to adopt the
following approach as guidance to air agencies submitting
demonstrations that will be subject to a case-specific assessment
(i.e., in situations other than when deferring to a nonattainment or
maintenance plan SIP).
To satisfy the not reasonably controllable or preventable criterion
in a case-specific assessment, the EPA proposes to consider
communications between the EPA and the air agency when assessing
``reasonableness'' as part of assessing the technical information
available to the air agency at the time the event occurred and what
should reasonably have been in place at the time of the event for
anthropogenic emission sources that contribute to the event emissions.
It is not the EPA's intent to retroactively apply its current judgments
about the reasonableness of controls for past events. However, it would
also be inappropriate for an air agency to fail to respond to the EPA's
recommendations prior to an event and then claim later in an event
demonstration that it was unaware of a reasonable control issue.
The EPA recognizes that regulations and an area's planning status
are often evolving and changing. The EPA may have recently promulgated
new or revised federal rules requiring controls on particular sources
or promulgated a new or revised nationally applicable standard that
will ultimately result in an air agency's adoption of new control
measures. The planning process to implement these new standards (e.g.,
the SIP or maintenance plan approval process) can be lengthy, sometimes
spanning several years and involving multiple rounds of formal and
informal communications between the affected air agency and the EPA
regarding the appropriateness and completeness of planning elements. In
some cases, discussion of issues regarding appropriate controls,
including what controls would constitute ``reasonable'' controls for
exceptional events purposes, are part of this iterative communications
process. The EPA solicits comment on what form of communication (short
of a SIP call) would be most effective in conveying the EPA's views to
the affected air agency and whether this approach would be most
appropriately addressed through guidance or regulatory text.
Prospective Agreement on Assessments of Not Reasonably Controllable
or Preventable. In the Interim High Winds Guidance, the EPA suggested
that an air agency could develop an assessment showing that the
controls in place for a particular type of event, or a planned
enhancement of those controls, were sufficient to meet the not
reasonably controllable or preventable criterion, and then obtain the
EPA's review and concurrence with
[[Page 72861]]
the assessment prior to more events of that type occurring. This
prospective approach would reduce disagreements that might otherwise
occur over later retrospective assessments. To date, most air agencies
that face recurring event issues have not pursued this option, but the
EPA will work with any air agency expressing an interest in pursuing
this approach.
Summary of Requests for Comments Regarding Not Reasonably
Controllable or Preventable. The EPA solicits comment on the following
clarifications to the ``not reasonably controllable or preventable''
criterion:
The EPA solicits comment on recommending as guidance that
when addressing the ``not reasonably controllable or preventable''
criterion within an exceptional events demonstration, air agencies
should: (1) Identify the natural and anthropogenic sources of emissions
causing and contributing to the event emissions, including the
contribution from local sources, (2) identify the relevant SIP or other
enforceable control measures in place for these sources and the
implementation status of these controls, and (3) provide evidence of
effective implementation and enforcement of reasonable controls, if
applicable.\54\ In identifying natural and anthropogenic sources, the
air agency should assess both potentially contributing local/in-state
and upwind sources. We also request comment on whether we should revise
the rule text to require these elements in a demonstration.
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\54\ The EPA generally expects evidence that the controls
determined to be reasonable, if any, were effectively implemented
and appropriately enforced. This assessment of local sources should
include a review and description of any known nearby facility upsets
or malfunctions that could have resulted in emissions of the
relevant pollutant(s) that influenced the monitored measurements on
the day(s) of the claimed events. In the case of a high wind dust
event, for example, for the identified potentially contributing
local and upwind sources, the analysis should explain how
significant dust emissions occurred despite having reasonable
controls in place (e.g., that controls were overwhelmed by high
wind), if appropriate.
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The EPA proposes to codify rule language to specify that
no case-specific justification is needed to support the ``not
reasonably controllable or preventable'' criterion for emissions-
generating activity that occurs outside of the boundaries of the state
(or tribal lands) within which the concentration at issue was
monitored.
The EPA solicits comment on specific guidance or rule
requirements regarding what constitutes reasonable control of
particular natural events and sources.
The EPA proposes to codify in rule language that, provided
the air agency is not under an obligation to revise the SIP, the EPA
would consider (i.e., give deference to) enforceable control measures
implemented in accordance with a state implementation plan, approved by
the EPA within 5 years of the date of a demonstration submittal, that
address the event-related pollutant and all sources necessary to
fulfill the requirements of the CAA for the SIP to be reasonable
controls with respect to all anthropogenic sources that have or may
have contributed to event-related emissions.
The EPA proposes to codify in rule language the time
period for such deference to be 5 years from the date of the SIP
approval measured to the date of an event at issue, but is taking
comment on whether and what other timeframes might be appropriate. To
the extent an alternative timeframe might be appropriate, comments
should explain how it would address the criteria provided above in
support of the 5-year timeframe.
The EPA proposes to consider communications and planning
status when assessing the status of reasonable controls and proposes to
do this through guidance. The EPA solicits comment on methods to
definitively identify the status of communications and planning efforts
(e.g., formal correspondence or other documentation, timelines for
responding) and whether this approach would be more appropriately
addressed through rule language.
3. Clear Causal Relationship Supported by a Comparison to Historical
Concentration Data
a. Current Situation
The CAA at section 319(b)(3)(B)(ii) requires that ``a clear causal
relationship must exist between the measured exceedances of a national
ambient air quality standard and the exceptional event to demonstrate
that the exceptional event caused a specific air pollution
concentration at a particular air quality monitoring location.'' The
clear causal relationship criterion establishes causality between the
event and a measured exceedance or violation of a NAAQS. As stated in
the preamble to the 2007 Exceptional Events Rule, given the directive
in CAA section 319(b)(3)(B)(ii), it would be unreasonable to exclude
data affected by an exceptional event simply because of a trivial
contribution of an event to air quality.\55\ The EPA does, however,
recognize that distinguishing trivial contributions from more
significant contributions to an exceedance may be difficult. As with
the other exceptional events criteria, the EPA has used a weight of
evidence approach when reviewing analyses to support a causal
relationship between an event and a monitored exceedance.
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\55\ 72 FR 13569 (March 22, 2007).
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Showing that an event and elevated pollutant concentrations
occurred simultaneously may not establish causality. The clear causal
relationship section of an exceptional events demonstration should
include analyses showing that the event occurred and that emissions of
the pollutant of interest resulting from the event were transported to
the monitor(s) recording the elevated concentration measurement(s). The
example analyses to support the clear causal relationship criterion,
shown in Table 1 and first summarized in the EPA's Interim Exceptional
Events Implementation Guidance, are generally appropriate analyses for
most event types.\56\ The EPA does not expect air agencies to include
all of the evidence and analyses identified in the table below, but
rather to use available information to build a weight of evidence
showing. The EPA may accept limited analyses (e.g., a comparison to
historical concentrations in combination with one or two additional
analyses from Table 1) for areas whose monitored ambient air
concentrations are generally well below the NAAQS on non-event days.
Additional analyses are beneficial if they establish a different facet
of the event and/or if they are used in combination with other analyses
with limited data. For example, the EPA expects that areas prone to
frequent elevated ozone (or other pollutant) concentrations, such as
nonattainment areas, to have more sophisticated air quality prediction
tools. We would expect these areas could use these tools when
supporting an exceptional events demonstration and developing analyses
to support a clear causal relationship. Additionally, photochemical or
[[Page 72862]]
regression modeling analyses may be beneficial in situations where the
causality between the event and a measured exceedance of a NAAQS is not
clearly established with evidence and analyses identified in Table 1.
For example, if a fire occurs during the normal high ozone season and
the ozone level associated with the fire is in the range of otherwise-
occurring ozone levels and/or only slightly above the ozone NAAQS, the
causal relationship between the fire and the exceedance or violation
may not be clear. In such a situation, modeling may produce a specific
estimate of the ozone contribution from the fire. Air agencies should
discuss with their EPA Regional office those types of analyses that may
be adequate to satisfy the weight of evidence requirement in individual
exceptional events demonstrations.
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\56\ For purposes of summarizing example clear causal
relationship analyses in one place, the EPA has included an entry
for the comparison to historical concentrations showing in Table 1.
The EPA notes that although the Interim High Winds Guidance and the
Interim Q&A document discussed the comparison to historical
concentrations showing, neither of these guidance documents
presented this showing as part of the clear causal relationship. See
specifically Interim Guidance on the Preparation of Demonstrations
in Support of Requests to Exclude Ambient Air Quality Data Affected
by High Winds Under the Exceptional Events Rule. U.S. EPA. May 2013.
Available at http://www2.epa.gov/sites/production/files/2015-05/documents/exceptevents_highwinds_guide_130510.pdf and Interim
Exceptional Events Rule Frequently Asked Questions. U.S. EPA. May
2013. Available at http://www2.epa.gov/sites/production/files/2015-05/documents/eer_qa_doc_5-10-13_r3.pdf.
Table 1--Example Clear Causal Relationship Evidence and Analyses
------------------------------------------------------------------------
Example of clear causal relationship Types of analyses/information
evidence to support the evidence
------------------------------------------------------------------------
Comparison to Historical Concentrations Analyses and statistics showing
how the observed event
concentration compares to the
distribution or time series of
historical concentrations of
the same pollutant.
Occurrence and geographic extent of the Special weather statements,
event. advisories, news reports,
nearby visibility readings,
measurements from regulatory
and non-regulatory (e.g.,
special purpose, emergency)
monitoring stations throughout
the affected area, satellite
imagery.
Transport of emissions related to the Wind direction data showing
event in the direction of the that emissions from sources
monitor(s) where the measurements were identified as part of the
recorded. ``not reasonably controllable
or preventable'' demonstration
were upwind of the monitor(s)
in question, satellite
imagery, monitoring data
showing elevated
concentrations of other
pollutants expected to be in
the event plume.
Spatial relationship between the event, Map showing likely source area,
sources, transport of emissions and wind speed/direction and
recorded concentrations. pollutant concentrations for
affected area during the time
of the event, trajectory
analyses.
Temporal relationship between the event Hourly time series showing
and elevated pollutant concentrations pollutant concentrations at
at the monitor in question. the monitor in question in
combination with wind speed/
direction data in the area
where the pollutant originated/
was entrained or transported.
Chemical composition and/or size Chemical speciation data from
distribution (for PM2.5 to PM10) of the monitored exceedance(s)
measured pollution that links the and sources, size distribution
pollution at the monitor(s) with data.
particular sources or phenomenon.
Comparison of event-affected day(s) to Comparison of concentration and
specific non-event days. meteorology to days preceding
and following the event,
comparison to high
concentration days in the same
season (if any) without
events, comparison to other
event days without elevated
concentrations (if any),
comparison of chemical
speciation data.
------------------------------------------------------------------------
As explained in additional detail in the EPA's Interim Exceptional
Events Implementation Guidance, what has previously been called the
``historical fluctuations'' showing (i.e., now referred to as the
comparison to historical concentrations) consists of analyses and
statistics showing how the observed event-affected concentration
compares to the distribution or time series of historical
concentrations of the same pollutant.
A demonstration may be less compelling if some evidence is
inconsistent with the description of how the event caused the
exceedance. For example, if an air agency describes an event as a
regional dust storm or wildfire, then the EPA anticipates that most or
all monitors within the same regional scale to be similarly affected by
the event. That is, the EPA expects that the demonstration elements and
factors (e.g., clear causal relationship, reasonable controls,
meteorology, wind speeds) would also support the case for a regional
event. Comparison of concentrations and conditions at other monitors
could thus be very important for the demonstration of a clear causal
relationship. Alternatively, eliminating plausible non-event causes may
also support a causal relationship between the event and the elevated
concentration.
The EPA has been recommending that the clear causal relationship
section of the demonstration should conclude with this type of
statement: ``On [day/time] an [event type] occurred which generated
pollutant X or its precursors resulting in elevated concentrations at
[monitoring location(s)]. The monitored [pollutant] concentrations of
[ZZ] were [describe the comparison to historical concentrations
including the percentile rank over an annual (seasonal) basis].
Meteorological conditions were not consistent with historically high
concentrations, etc.'' and ``Analyses X, Y and Z support Agency A's
position that the event affected air quality in such a way that there
exists a clear causal relationship between the specific event and the
monitored exceedance or violation and thus satisfies the clear causal
relationship criterion.''
b. Proposed Changes
As previously noted, the EPA is proposing to revise the 2007
Exceptional Events Rule text as follows:
To move the ``clear causal relationship'' element into the
list of criteria that explicitly must be met for data to be excluded
To subsume the ``affects air quality'' element into the
``clear causal relationship'' element
To remove the term ``historical fluctuations'' and replace it
with text referring to a comparison to historical concentrations
To clarify that the comparison to historical concentrations is
not a fact that must be proven
To clearly identify the types of analyses that are necessary
and sufficient in a demonstration to address the comparison to
historical concentrations
To remove the ``but for'' element (as discussed in section
V.B.2)
Additionally, the EPA proposes to reiterate in guidance the example
analyses to support the clear causal relationship criterion, shown in
Table 1 above, and first summarized in the
[[Page 72863]]
EPA's Interim Exceptional Events Implementation Guidance. As noted
previously, the EPA does not expect air agencies to include all of the
evidence and analyses identified in Table 2 below, but rather to use
available information to build a weight of evidence showing.
The EPA's rationale for proposing the previously identified changes
to the clear causal relationship criterion is presented in section V.B.
The remainder of this section focuses on the types of analyses that an
air agency must provide in its demonstration to make the comparison to
historical concentrations. As noted in the Current Situation section,
the EPA has included an entry in Table 1 for the comparison to
historical concentrations showing.
The comparison to historical concentrations, referred to as the
``historical fluctuations'' showing in the 2007 Exceptional Events Rule
and the Interim Exceptional Events Implementation Guidance, is a
requirement in the 2007 Exceptional Events Rule but it is not a
statutory requirement. The EPA's intent with this regulatory element
was to require air agencies to present event-influenced concentration
data along with historical data and to quantify the difference, if any,
between the event and the non-event concentrations. Comparing event-
influenced concentrations to historical concentrations bolsters the
weight of evidence within the clear causal relationship determination.
The EPA proposes to re-phrase and incorporate the current regulatory
requirement at 40 CFR 50.14(c)(3)(iv)(C), which requires that a
demonstration to justify data exclusion provide evidence that ``[t]he
event is associated with a measured concentration in excess of normal
historical fluctuations, including background,'' within the ``clear
causal relationship'' criterion. In using this approach, we propose to
remove from the regulatory text the ``in excess of normal historical
fluctuations, including background'' phrase and to subsume the concept
of historical comparisons into what will effectively be a
``completeness'' requirement within the ``clear causal relationship''
criterion. As noted above, we specifically propose to remove the phrase
``in excess of normal historical fluctuations, including background''
as we believe this language is vague and provides no additional value
to historical concentration comparisons.
To aid the EPA's review, reduce our need to request additional
information from air agencies and facilitate our understanding of the
air agency's position, we are proposing rule text changes to indicate
that an air agency submitting a demonstration must provide the
following types of statistics, graphics and explanatory text regarding
comparisons to past data. The rule change would also indicate that this
information is sufficient to satisfy the rule's requirement regarding
the comparison to historical concentration data. Table 2 below
identifies appropriate analyses and examples for comparing event-
related concentrations to historical concentrations within the clear
causal relationship criterion.
Table 2--Evidence and Analyses for the Comparison to Historical Concentrations
----------------------------------------------------------------------------------------------------------------
Historical concentration evidence Types of analyses/supporting information Required or optional?
----------------------------------------------------------------------------------------------------------------
1. Comparison of concentrations on the Seasonal (appropriate if exceedances occur Required seasonal and/or
claimed event day with past historical primarily in one season, but not in annual analysis
data. others). (depending on which is
more appropriate).
Use all available seasonal data
over the previous 5 years (or more, if
available).
Discuss the seasonal nature of
pollution for the location being
evaluated.
Present monthly maximums of the
NAAQS relevant metric (e.g., maximum
daily 8-hour average ozone or 1-hr SO2)
vs monthly or other averaged daily data
as this masks high values.
Annual (appropriate if exceedances are
likely throughout the year).
Use all available data over the
previous 5 years (or more, if available).
Seasonal and Annual Analyses
Provide the data in the form
relevant to the standard being considered
for data exclusion.
Label ``high'' data points as
being associated with concurred
exceptional events, suspected exceptional
events, other unusual occurrences, or
high pollution days due to normal
emissions.
Describe how emission control
strategies have decreased pollutant
concentrations over the 5-year window, if
applicable.
Include comparisons omitting
known or suspected exceptional events
points, if applicable.
See examples at http://www.epa.gov/ttn/analysis/docs/IdeasforShowingEEEvidence.ppt and
Question 3 in the Interim Q&A document
provides additional detail. \a\
2. Comparison of concentrations on the Include neighboring days at the Optional analysis.
claimed event day with a narrower set same location (e.g., a time series of two
of similar days. to three weeks) and/or other days with
similar meteorological conditions
(possibly from other years) at the same
or nearby locations with similar
historical air quality along with a
discussion of the meteorological
conditions during the same timeframe. \b\
Use this comparison to
demonstrate that the event caused higher
concentrations than would be expected for
given meteorological and/or local
emissions conditions.
3. Percentile rank of concentration when Provide the percentile rank of Required analysis when
compared to annual data. \c\ the event-day concentration relative to comparison is made on an
all measurement days over the previous 5 annual basis (see item
years to ensure statistical robustness #1).
and capture non-event variability over
the appropriate seasons or number of
years. \d\
[[Page 72864]]
Use the daily statistic (e.g., 24-
hour average, maximum daily 8-hour
average, or maximum 1-hour) appropriate
for the form of the standard being
considered for data exclusion.
4. Percentile rank of concentration Provide the percentile rank of Required analysis when
relative to seasonal data. \c\ the event-day concentration relative to comparison is made on a
all measurement days for the season (or seasonal basis (see item
appropriate alternative 3-month period) #1).
of the event over the previous 5 years.
Use the same time horizon as used
for the percentile rank calculated
relative to annual data, if appropriate.
----------------------------------------------------------------------------------------------------------------
\a\ Interim Exceptional Events Rule Frequently Asked Questions. U.S. EPA. May 2013. Available at http://www2.epa.gov/sites/production/files/2015-05/documents/eer_qa_doc_5-10-13_r3.pdf.
\b\ If an air agency compares the concentration on the claimed event day with days with similar meteorological
conditions from other years, the agency should also verify and provide evidence that the area has not
experienced significant changes in wind patterns, and that no significant sources in the area have had
significant changes in their emissions of the pollutant of concern.
\c\ The EPA does not intend to identify a particular historical percentile rank point in the seasonal or annual
historical data that plays a critical role in the analysis or conclusion regarding the clear causal
relationship.
\d\ Section 8.4.2.e of appendix W (proposed revisions at 80 FR 45374, July 29, 2015) recommends using 5 years of
adequately representative meteorology data from the National Weather Service to ensure that worst-case
meteorological conditions are represented. Similarly, for exceptional events purposes, the EPA believes that 5
years of ambient air data, whether seasonal or annual, better represent the range of ``normal'' air quality
than do shorter periods.
As with other evidence in an exceptional events demonstration
submittal, the EPA will use a holistic weight of evidence approach in
reviewing submitted demonstration packages and will consider the
``clear causal relationship'' information, including the comparison to
historical concentrations showing, along with evidence supporting the
other Exceptional Events Rule criteria.
F. Treatment of Certain Events Under the Exceptional Events Rule
As we stated in the preamble to the 2007 Exceptional Events Rule,
we maintain that air quality data affected by the following event types
are among those that could meet the definition of an exceptional event
and qualify for data exclusion provided all requirements of the rule
are met: (1) Chemical spills and industrial accidents,\57\ (2)
structural fires, (3) terrorist attacks, (4) volcanic and seismic
activities, (5) natural disasters and associated cleanup and (6)
fireworks.\58\ We are not proposing any changes to the definition or
discussion of these event types. The AQS database contains a more
detailed list of other similar events that may be identified for
special consideration. The EPA will consider other types of events on a
case-by-case basis.
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\57\ A malfunction at an industrial facility could be considered
to be an exceptional event if it has not resulted in source
noncompliance, which is statutorily excluded from consideration as
an exceptional event, see CAA 319(b)(1)(b)(iii), and if it otherwise
meets the requirements of the Exceptional Events Rule.
\58\ Of these noted event types, only fireworks are currently
identified in the regulatory language at 40 CFR 50.14. We are not
proposing any revisions to the exclusion at 40 CFR 50.14(b)(2) for
fireworks that are demonstrated to be significantly integral to
traditional national, ethnic, or other cultural events.
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Based on our implementation experience, the following other
potential exceptional events categories warrant additional discussion:
Exceedances due to transported pollution, wildland fires including
wildfires and prescribed fires, stratospheric ozone intrusions and high
wind dust events. We discuss each of these event categories in the
following sections.
1. Exceedances Due to Transported Pollution
a. Current Situation
The 2007 Exceptional Events Rule implements one important CAA
provision related to transported pollution. Certain events, national or
international in origin and from natural or anthropogenic sources, may
cause exceedances that are eligible for exclusion under the 2007
Exceptional Events Rule if an air agency satisfies the rule criteria.
We discuss in this section our position regarding exceedances due to
event-related transported pollution. We also clarify in part c of this
section how the Exceptional Events Rule provisions currently relate to
other CAA mechanisms that address or involve transported pollution. We
are not proposing any changes to these relationships.
The EPA believes that the Exceptional Events Rule will often be the
most appropriate mechanism to use when addressing transported emissions
from out-of-state natural events and/or events due to human activity
that is unlikely to recur at a particular location, because the
Exceptional Events Rule may be used during the initial area
designations process and may make a difference between an attainment
versus a nonattainment designation. It is important to note, however,
that the transported natural emissions must be event-related (e.g.,
wildfires or stratospheric ozone intrusion) versus ongoing on a daily
basis.
b. Proposed Changes
If an air agency determines that the Exceptional Events Rule is the
most suitable approach to address contributions from transported
emissions, then the air agency must consider the point of origin and
the sources contributing to the exceedance or violation to determine
how to address individual Exceptional Events Rule criteria,
specifically the not reasonably controllable or preventable criterion
and the human activity unlikely to recur or a natural event criterion.
The analyses to satisfy the clear causal relationship criterion (which
would subsume the CAA's affects air quality criterion, if promulgated
as proposed and discussed in section V.B) are largely independent of
whether the point of origin and contributing sources are within the air
agency's jurisdiction. The EPA first addressed these concepts in its
Interim Q&A document and now proposes to clarify these intrastate and
interstate scenarios.
Under the CAA, the EPA generally considers a state (not including
areas of Indian country) to be a single responsible actor. Accordingly,
neither the EPA nor the 2007 Exceptional Events Rule provides special
considerations for intrastate scenarios when an event in one part of a
state, such as a county or air district, affects air quality in another
part of the same
[[Page 72865]]
state, assuming that the event occurs on land subject to state
authority (versus tribal government authority). For cases involving
intrastate transport, the state or local air agency should evaluate
whether contributing event emissions from all parts of the state were
not reasonably controllable or preventable. Section V.E.2 discusses the
assessment of the not reasonably controllable or preventable criterion.
Because there may be special considerations regarding air agencies'
authority to regulate activity on federally-owned and managed lands
(e.g., national parks within the state), states and tribes should
consult with the appropriate FLM or other federal agency and their EPA
Regional office early in the development of an exceptional events
demonstration package if they believe that sources on federally-owned
and managed land contributed event-related emissions to a degree that
raises issues of reasonable control.
Interstate and international transport events are different than
intrastate events. As noted in section V.E.2, the EPA maintains that it
is not reasonable to expect the downwind air agency (i.e., the state or
tribe submitting the demonstration) to have required or persuaded the
upwind foreign country, state or tribe to have implemented controls on
sources sufficient to limit event-related air concentrations in the
downwind state nor does the EPA believe that Congress intended to deny
the downwind state or tribe of relief in the form of data exclusion. As
with any demonstration submittal, the submitting (downwind) state
should identify all natural and anthropogenic contributing sources of
emissions (both local/in-state and out-of-state) to show the causal
connection between an event and the affected air concentration values.
A submitting state may provide a less detailed characterization of
sources in the upwind state or foreign country than of sources within
its jurisdiction. After completing the source characterization, the
submitting state should assess whether emissions from sources within
its state were not reasonably controllable or preventable (see section
V.E.2 of this proposal). Although the downwind state must still assess
potential contribution from in-state sources, we propose that the
event-related emissions that were transported in the downwind state are
``not reasonably controllable or preventable'' for purposes of data
exclusion. The EPA does not expect air agencies to submit analyses to
satisfy the not reasonably controllable or preventable criterion for
those upwind, out-of-state sources that contribute to the exceedance as
part of a submitted demonstration. Rather, with respect to this element
for such sources, an air agency would merely point to the relevant
provision we propose to add to the Exceptional Events Rule. Submitting
states are, however, still required to assess the contribution and
potential controls from local/in-state sources and submit evidence/
statements supporting the other exceptional events criteria (i.e.,
clear causal relationship, human activity unlikely to recur or a
natural event). If the event-related emissions are international in
origin and affect monitors in multiple states or regions, the EPA may
assist affected agencies in identifying approaches for evaluating the
potential impacts of international transport and determining the most
appropriate information and analytical methods for each area's unique
situation.
The EPA proposes a similar approach to significant out-of-state
anthropogenic sources in the case of a mixed natural/anthropogenic
event that the submitting state wishes to have treated as a natural
event on the grounds that all significant anthropogenic sources were
reasonably controlled. That is, if a mixture of natural and
anthropogenic sources in an upwind state contributed to an event, the
downwind state is not required to demonstrate that the anthropogenic
sources in the upwind state were reasonably controlled for those
sources to be considered to not have directly caused the event. The
submitting state could consider the event to be a natural event based
on the situation within the state requesting the data exclusion (that
is, the contributing sources within the jurisdiction of the submitting
state were either natural or reasonably controlled anthropogenic
sources).
As with all exceptional events demonstrations, the EPA will
evaluate the information on a case-by-case basis based on the facts of
a particular exceptional event including any information and arguments
presented in public comments received by the state in its public
comment process or by the EPA in a notice-and-comment regulatory action
that depends on the data exclusion.
c. Relationship Between Exceptional Events Rule Provisions and Other
CAA Transport Mechanisms
Two provisions of the CAA other than section 319(b) also provide
regulatory relief for transported pollution, for different
circumstances than those addressed by the 2007 Exceptional Events Rule.
These provisions are briefly described here as context for
understanding the role of the Exceptional Events Rule itself.
CAA section 179B, International Transport--CAA section
179B allows states to consider in their attainment demonstrations
whether a nonattainment area might have met the NAAQS by the attainment
date ``but for'' emissions contributing to the area originating outside
the U.S. This provision addresses sources of emissions originating
outside of the U.S. and provides qualifying nonattainment areas some
regulatory relief from otherwise-applicable additional planning and
control requirements should the area fail to reach attainment by its
deadline. It does not provide a pathway for regulatory relief from
designation as a nonattainment area.
CAA section 182(h), Rural Transport Areas--CAA section
182(h) authorizes the EPA Administrator to determine that an ozone
nonattainment area can be treated as a rural transport area, which
provides relief from more stringent requirements associated with higher
nonattainment area classifications (i.e., classifications above
Marginal). Under CAA section 182(h), a nonattainment area may qualify
as a Rural Transport Area if it does not contain emissions sources that
make a significant contribution to monitored ozone concentrations in
the area or in other areas, and if the area does not include and is not
adjacent to a Metropolitan Statistical Area. Generally, an area
qualifies as a Rural Transport Area because it does not contribute to
its own or another area's nonattainment problem; rather, ozone
exceedances are due to transported emissions, which could be
international, interstate or intrastate in origin. The Rural Transport
Area determination can be made during or after the initial area
designations and classifications process.
Two additional provisions of the CAA specifically address and
appropriately regulate transported pollution that does not qualify for
data exclusion under the Exceptional Events Rule or for regulatory
relief under CAA section 179B or CAA section 182(h). These provisions
are briefly described here as context for understanding the role of the
Exceptional Events Rule itself.
CAA section 110(a)(2)(D)(i)(I), Interstate Transport--CAA
section 110(a)(2)(D)(i)(I) requires states to develop and implement
SIPs to address the interstate transport of emissions. Specifically,
this provision requires each state's SIP to prohibit ``any source or
other type of emissions activity within the State from emitting any air
pollutant in amounts which will significantly contribute to
[[Page 72866]]
nonattainment'' of any NAAQS in another state, or which will
``interfere with maintenance'' of any NAAQS in another state. When the
EPA promulgates or revises a NAAQS, each state is required to submit a
SIP addressing this interstate transport provision as to that NAAQS
within 3 years. The EPA interprets this interstate transport provision
to address anthropogenic sources of emissions from other states; we
believe that is not intended to address natural sources of emissions.
CAA section 126, Interstate Transport--CAA section 126
provides states and political subdivisions with a mechanism to petition
the Administrator for a finding that ``any major source or group of
stationary sources emits or would emit any air pollution in violation
of the prohibition of CAA 110(a)(2)(D)(i).'' \59\ Where the EPA grants
such a petition, an existing source may operate beyond a 3-month period
only if the EPA establishes emissions limitations and compliance
schedules to bring about compliance with CAA section 110(a)(2)(D)(i) as
expeditiously as practicable, but no later than 3 years after such
finding. Similar to our interpretation above for CAA section
110(a)(2)(D)(i), the EPA interprets the reference to ``major source or
group of stationary sources'' in section 126 to refer to anthropogenic
sources of emissions from other states. The EPA's interpretation is
that this provision is not intended to address natural sources of
emissions. This mechanism is available to all downwind states, and
political subdivisions, regardless of area designations, that may be
affected by anthropogenic sources of emissions from upwind states in
violation of the prohibition in CAA section 110(a)(2)(D)(i).
---------------------------------------------------------------------------
\59\ The text of section 126 codified in the United States Code
cross references section 110(a)(2)(D)(ii) instead of section
110(a)(2)(D)(i). The courts have confirmed that this is a
scrivener's error and the correct cross reference is to section
110(a)(2)(D)(i), See Appalachian Power Co. v. EPA, 249 F.3d 1032,
1040-44 (D.C. Cir. 2001).
---------------------------------------------------------------------------
As noted previously, in most cases, the mechanisms in the
Exceptional Events Rule often provide the most regulatory flexibility
in that air agencies can use these provisions to seek relief from
designation of an area as nonattainment. The CAA section 179B
(International Transport) and section 182(h) (Rural Transport Areas)
apply following, or concurrent with, the initial area designations
process.
2. Wildland Fires
Fires on wildland play an important ecological role across the
globe, benefiting those plant and animal species that depend upon
natural fires for propagation, habitat restoration and reproduction.
Wildland can include forestland,\60\ shrubland,\61\ grassland \62\ and
wetlands.\63\ Fires on wildland can be of two types: wildfire
(unplanned) and prescribed fire (intentionally ignited for management
purposes). Since promulgation of the 2007 Exceptional Events Rule, the
EPA has received and acted upon exceptional events demonstrations for
both wildfires and prescribed fires. The EPA anticipates receiving
increasing numbers of fire-related demonstrations in the future due to
the natural accumulation of fuels in the absence of fire, due to
climate change that is leading to increased incidence of wildfire,\64\
which may necessitate land managers employing prescribed fire more
frequently to manage fuel loads and achieve other benefits as described
below,\65\ \66\ and due to the potential for fire-related
demonstrations to affect near-term regulatory decisions such as the
initial area designations decisions associated with a revised 8-hour
ozone NAAQS. Consequently, the EPA is proposing revisions to the 2007
Exceptional Events Rule and developing additional guidance to make the
preparation and review of demonstrations for wildland fire events more
efficient and predictable for all parties.
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\60\ Forestland is land on which the vegetation is dominated by
trees or, if trees are lacking, the land shows historic evidence of
former forest and has not been converted to other uses. Definition
available at https://globalrangelands.org/rangelandswest/glossary.
\61\ Shrubland is land on which the vegetation is dominated by
shrubs. Definition available at https://globalrangelands.org/rangelandswest/glossary.
\62\ Grassland is land on which the vegetation is dominated by
grasses, grass like plants, and/or forbs. Definition available at
https://globalrangelands.org/rangelandswest/glossary.
\63\ Wetlands, as defined in 40 CFR 230.3(t), means those areas
that are inundated or saturated by surface or ground water at a
frequency and duration sufficient to support, and that under normal
circumstances do support, a prevalence of vegetation typically
adapted for life in saturated soil conditions. Wetlands generally
include swamps, marshes, bogs and similar areas.
\64\ The Administrator's finding on the adverse effects of
greenhouse gases included the observation that wildfires have
increased, and that there are potential serious adverse impacts from
further wildfire occurrence. 74 FR 66530 (December 15, 2009).
\65\ Climate Change in the United States: Benefits of Global
Action, U.S. EPA, EPA-430-R-15-001, June 2015. Available at http://www2.epa.gov/cira.
\66\ The National Strategy: The Final Phase in the Development
of the National Cohesive Wildland Fire Management Strategy, Report
to Congress developed by the U.S. Department of Agriculture and the
U.S. Department of the Interior, April 2014. Available at http://www.forestsandrangelands.gov/strategy/thestrategy.shtml.
---------------------------------------------------------------------------
Wildfire emissions account for a large portion of direct
PM2.5 emissions nationally and can contribute to periodic
high PM2.5 and PM10 levels. Wildfires also emit
volatile organic compounds (VOC) and nitrogen oxides (NOX),
which are precursors to PM2.5, PM10 and ozone.
Besides their effect on air quality, wildfires pose a direct threat to
public safety. Changes in wildfire risk and occurrence are closely
associated with the lack of periodic fire in fire-dependent ecosystems,
demographic changes and associated infrastructure investment at the
margins of wildland and, as already noted, climate change and climate
variability. The threat from wildfires can be mitigated through
management of wildland vegetation. Attempts to suppress wildfires have
resulted in unintended consequences, especially the buildup of fuel
loads, which can create a lingering fire liability that will eventually
find resolution, unplanned or planned. Unplanned fires in areas with
high fuel loads present high risks to both humans and ecosystems.\67\
Planned prescribed fires and letting some wildfires proceed naturally
(typically those with lower fire intensity and severity) are tools that
land managers can use to reduce fuel load, unnatural understory and
tree density, thus helping to reduce the risk of catastrophic
wildfires. Allowing some wildfires to continue to burn even though they
could be suppressed and the thoughtful use of prescribed fire can
influence the occurrence, size and severity of catastrophic wildfires,
which may lead to improved public safety, improved protection of
property and an overall reduction in fire-induced smoke impacts and
subsequent health effects. Thus, appropriate use of prescribed fire may
help manage the contribution of wildfires to both background and peak
PM and ozone air pollution. However, prescribed fires themselves can
affect monitored air quality at some times and places affecting public
health, and thus give rise to exceptional events issues. This action
proposes a workable approach to addressing these prescribed fire
exceptional events issues.
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\67\ Indeed, ``fire policy that focuses on [wildfire]
suppression only, delays the inevitable, promising more dangerous
and destructive future . . . fires.'' Stephens, SL; Agee, JK; Fule,
PZ; North, MP; Romme, WH; Swetnam, TW. (2013). Managing Forests and
Fire in Changing Climates. Science 342: 41-42.
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In addition to reducing wildfire risks to humans and ecosystems and
wildfire contributions to air pollution, prescribed fires can have
benefits to those plant and animal species that
[[Page 72867]]
depend upon natural fires for propagation, habitat restoration and
reproduction, as well as benefits to a myriad of ecosystem functions
(e.g., carbon sequestration, maintenance of water supply systems and
endangered species habitat maintenance). The EPA understands the
importance of prescribed fire, which mimics a natural process necessary
to manage and maintain fire-adapted ecosystems and climate change
adaptation, while reducing risk to public safety and the risk of
uncontrolled emissions and ecosystem damage from catastrophic
wildfires. The EPA is committed to working with federal land managers,
other federal agencies, tribes, states and private landowners to
effectively manage prescribed fire use to reduce the impact of
catastrophic wildfire-related emissions on ozone, PM10 and
PM2.5.
a. Current Situation
When the EPA promulgated the 2007 Exceptional Events Rule, we
included definitions for fire-related terms (e.g., wildfire, prescribed
fire and wildland) in the preamble and attributed these definitions to
the National Wildland Fire Coordinating Group (now the National
Wildfire Coordinating Group or NWCG) Glossary of Wildland Fire
Terminology, 2003. The EPA did not, however, codify these definitions
in regulatory text. Since promulgation of the 2007 Exceptional Events
Rule, the NWCG has modified some of its recommended definitions and the
EPA used slightly different definitions in its Interim Exceptional
Events Implementation Guidance, creating some confusion for air
agencies and other entities working with air agencies who have tried to
use fire-related definitions and concepts when preparing and submitting
exceptional events demonstrations for fires.
The preamble to the 2007 Exceptional Events Rule discussed how the
EPA expected to apply the rule to wildfires and prescribed fires. The
EPA stated that wildfires would be considered natural events, while
prescribed fires would be considered events caused by human activity.
As events caused by human activity, prescribed fires are subject to the
``not likely to recur'' criterion, and the preamble to the rule
discussed the considerations that would apply for this criterion.
Section V.F.2.d provides a more detailed summary of the current
situation and planned changes for this criterion.
Demonstrations for wildfires and those prescribed fires claimed to
be exceptional events must also address the ``not reasonably
controllable or preventable'' criterion. Neither the 2007 Exceptional
Events Rule nor its preamble addressed this criterion in any depth for
wildfires. Since promulgating the rule in 2007, the EPA has concluded
that short, general statements in demonstrations for fire events
satisfy this criterion. The EPA has been advising air agencies that
when documenting the ``not reasonably controllable or preventable''
criterion in a wildfire exceptional events demonstration submittal, air
agencies should identify the origin and evolution of the wildfire,
describe local efforts to prevent fires due to unauthorized activity or
accidental human-caused actions (if relevant given the origin of the
fire) and explain any efforts to limit the duration or extent (and thus
the emissions) of the wildfire.68 69 70 We have also advised
air agencies that if the wildfire originated outside of the
jurisdiction of the air agency submitting the exceptional events
demonstration, then the submitting air agency should identify this fact
in its demonstration.\71\
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\68\ Interim Exceptional Events Rule Frequently Asked Questions.
U.S. EPA. May 2013. Available at http://www2.epa.gov/sites/production/files/2015-05/documents/eer_qa_doc_5-10-13_r3.pdf. See
question 20b.
\69\ Prevention/control efforts could include posting High Fire
Danger signs to make people more careful and prevent accidental
fires, and/or taking reasonable action to contain a fire once it has
started.
\70\ Example language to limit the duration and extent of the
wildfire might include, ``During wildfires, fire management
resources were deployed to the fire event giving first priority to
protecting life and property.''
\71\ Interim Exceptional Events Rule Frequently Asked Questions.
U.S. EPA. May 2013. Available at http://www2.epa.gov/sites/production/files/2015-05/documents/eer_qa_doc_5-10-13_r3.pdf.
---------------------------------------------------------------------------
The 2007 Exceptional Events Rule and its preamble gave more
extensive treatment to the not reasonably controllable or preventable
criterion for prescribed fires. The rule text tied the eligibility of
prescribed fires as approved exceptional events to the air agency
having a ``certified'' SMP in place or, in the alternative, to using
BSMP for the prescribed fire(s) in question. In the preamble, the EPA
did not provide detailed guidance on SMPs or BSMP, but committed to
defining and developing these concepts when we updated the guidance
contained in the 1998 Interim Air Quality Policy on Wildland and
Prescribed Fires.\72\ However, the EPA has not revised this guidance
document. Although some states have developed demonstrations that
incorporate BSMP employed for a specific prescribed fire and/or have
referenced BSMP in their SMPs, the EPA has not in any other more recent
guidance clarified what it means for an air agency or burner to have a
certified SMP in place and/or to implement BSMP. Like the inconsistency
that has developed since 2007 in fire-related definitions, the absence
of further clarifying guidance on SMPs and BSMP has created confusion
for air agencies trying to develop these plans and/or apply these
practices for purposes of developing and submitting exceptional events
demonstrations for prescribed fires.
---------------------------------------------------------------------------
\72\ Interim Air Quality Policy on Wildland and Prescribed
Fires. U.S. EPA. April 23, 1998. Available at http://www.epa.gov/ttn/oarpg/t1/memoranda/firefnl.pdf.
---------------------------------------------------------------------------
b. Proposed Changes
In this action, the EPA proposes to codify in regulatory language
certain fire-related definitions and SMP/BSMP factors necessary for
exceptional events demonstration and program implementation purposes.
Codifying these definitions in 40 CFR 50.1 will promote understanding
and standardize terminology for the purposes of characterizing an event
for exceptional events demonstration purposes.
Finalizing these proposed changes will also decouple implementation
of the exceptional events process from potential future revisions to
the Interim Policy on Wildland and Prescribed Fires. Although the EPA
solicits comment on the regulatory process associated with developing
exceptional events demonstrations for fire-related events, the EPA does
not intend to take comment on any aspects of the 1998 Interim Policy on
Wildland and Prescribed Fires as part of this effort to revise the
Exceptional Events Rule.
The proposed new definitions, along with other proposed changes,
are described in detail in the separate sections on wildfires (section
V.F.2.c) and prescribed fire (section V.F.2.d) that follow immediately
below this section.
c. Wildfires
Current Situation. The preamble to the 2007 Exceptional Events Rule
defined a wildfire as ``an unplanned, unwanted wildland fire (such as a
fire caused by lightning), [to] include unauthorized human-caused fires
(such as arson or acts of carelessness by humans), escaped prescribed
fire projects (escaped control due to unforeseen circumstances), where
the appropriate management response includes the objective to suppress
the fire.'' The 2007 Exceptional Events Rule preamble also defined a
``wildland fire use'' as ``the application of the appropriate
management response to a naturally-ignited (e.g., as the result of
lightning) wildland fire to accomplish specific resource management
objectives in predefined and designated areas
[[Page 72868]]
where fire is necessary and outlined in fire management or land
management plans.'' The 2007 Exceptional Events Rule preamble further
clarified that the EPA believed that both wildfires and wildland fire
use fires fall within the meaning of ``natural events'' as that term is
used in CAA section 319(b).
In the 2013 Interim Q&A Document, after consulting with other
federal agencies that manage wildfires and prescribed fires, the EPA
defined a wildfire as ``[a]ny fire started by an unplanned ignition
caused by lightning; volcanoes; unauthorized activity; accidental,
human-caused actions; and escaped prescribed fires.'' \73\
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\73\ Interim Exceptional Events Rule Frequently Asked Questions.
U.S. EPA. May 2013. Available at http://www2.epa.gov/sites/production/files/2015-05/documents/eer_qa_doc_5-10-13_r3.pdf.
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Building off of the principles in the February 2009 Guidance for
Implementation of Federal Wildland Fire Management Policy,\74\ the NWCG
defines ``wildland'' as ``an area in which development is essentially
non-existent, except for roads, railroads, power lines, and similar
transportation facilities. Structures, if any, are widely scattered.''
\75\
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\74\ Guidance for Implementation of Federal Wildland Fire
Management Policy, developed cooperatively by the Fire Executive
Council, February 13, 2009. Available at http://wildfiretoday.com/documents/Federal%20Wildland%20Fire%20Management%20Policy%2002-13-2009.pdf.
\75\ National Wildfire Coordinating Group. Glossary of Wildland
Fire Terminology, PMS 205. October 2014. Available at http://www.nwcg.gov/sites/default/files/products/pms205.pdf.
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Proposed Changes. Although the EPA has previously approved
exceptional events demonstrations for wildfires,\76\ the EPA recognizes
air agencies preparing exceptional events demonstrations for future
wildfires will benefit from additional clarification and guidance
related to wildfire terminology. This section discusses the EPA's
proposed changes.
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\76\ See submitted exceptional events demonstrations available
on the EPA's Web site at http://www2.epa.gov/air-quality-analysis/exceptional-events-submissions-table.
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(i) Definition of wildland and wildfire. For purposes of this
action, the EPA proposes to codify in regulatory language the
definition of ``wildland'' by using the October 2014 NWCG Glossary
definition that a wildland is ``an area in which human activity and
development is essentially non-existent, except for roads, railroads,
power lines, and similar transportation facilities. Structures, if any,
are widely scattered.'' As previously noted, wildland can include
forestland, shrubland, grassland and wetlands. This proposed definition
of wildland would include lands that are predominantly wildland, such
as land in the wildland-urban interface.77 78
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\77\ The wildland-urban interface is the line, area or zone
where structures and other human development meet or intermingle
with undeveloped wildland or vegetative fuels. The term describes an
area within or adjacent to private and public property where
mitigation actions can prevent damage or loss from wildfire. See,
Glossary of Wildland Fire Terminology, PMS 205. October 2014.
Available at http://www.nwcg.gov/sites/default/files/products/pms205.pdf.
\78\ We would generally treat a large prescribed fire in a
wildland-urban interface area as a prescribed fire on wildland,
subject to the prescribed fire provisions described in this
proposal. We do not expect a small prescribed fire in an interface
area (e.g., a prescribed burn ignited by a single landowner on his/
her personal property) to generate emissions that would raise
exceptional events issues.
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In proposing this definition for wildland, the EPA considered the
types of human intervention that could affect whether a land is
considered a ``wildland.'' In our view and the view of other federal
agencies with which we have consulted in the development of this
proposed action, the presence of fences to limit the movement of
grazing animals, or of infrastructure to provide water to grazing
animals, does not prevent a land area from being wildland. Cultivated
cropland (i.e., a field that is plowed or disked or from which crops
are removed on an annual or more frequent basis) is not wildland. Land
areas on which nursery stock is grown to marketable size (e.g.,
Christmas tree farms) are generally not wildland unless they are
``wild'' in terms of a having only limited human entrance and
intervention for management or removal purposes thereby resulting in a
complex ecosystem. Generally, managed timber lands may be considered
wildland if they have a complex ecosystem affected by only limited
human entrance and intervention. The EPA invites comment on whether it
would be appropriate to incorporate these examples of land use types
that can be considered to be (or not to be) wildland into the
regulatory definition of wildland or whether or it is adequate to
discuss them in the preamble only.
Also for purposes of this action, the EPA proposes to codify in
regulatory language the following definition of ``wildfire,'' which
slightly modifies the definition of ``wildfire'' with respect to
prescribed fires that appeared in the Interim Q&A document.
A wildfire is any fire started by an unplanned ignition caused
by lightning; volcanoes; other acts of nature; unauthorized
activity; or accidental, human-caused actions; or a prescribed fire
that has been declared to be a wildfire. A wildfire that
predominantly occurs on wildland is a natural event.
This proposed definition of wildfire does not require that the
objective be to put out a fire for the fire to be categorized as a
wildfire. When an unplanned fire on wildland does not threaten
catastrophic consequences, it may be very appropriate to allow it to
continue. The proposed definition therefore encompasses the type of
activity previously referred to as a wildland fire use (i.e., a
situation in which a fire manager deliberately allows a wildfire to
continue to burn over a certain land area rather than immediately
extinguish it or block its progress into that area). This inclusion is
consistent with the approach taken in 2007 that all types of wildfire
were considered to be natural. We note here, as guidance, that the part
of the proposed definition referring to a prescribed fire that has been
declared to be a wildfire refers to specific instances in which the
conditions of a particular prescribed fire have developed in a way that
leads the fire manager to decide that the fire should be treated as a
wildfire, for example if it has escaped secure containment lines and
requires suppression along all or part of its boundary or no longer
meets the resource objectives (e.g., smoke impact, flame height). It is
not the intention that land managers may categorically re-define some
types of prescribed fire to be wildfires.
Because the EPA is proposing in rule text that all wildfires on
wildland are always considered natural events, the proposed definition
of wildland will in turn determine which fires are considered to be
natural events. This is consistent with the approach in the 2007
Exceptional Events Rule. The EPA realizes that some wildfires are
initiated by human actions (e.g., careless use of campfires or leaf and
brush pile fires). The EPA also realizes that past human activity in
the form of decades of suppressing wildfires has influenced the size
and emissions of wildfires that do occur. However, wildfire is mostly
dominated by natural factors, and the EPA believes that treating all
wildfires on wildland as natural events is in keeping with
Congressional intent and not contradictory to any plain meaning of CAA
section 319(b). Therefore, because a wildfire on wildland is a natural
event and because natural events can recur, an air agency would not
need to address event recurrence in the ``human activity unlikely to
recur at a particular location or a natural event'' portion of its
exceptional events demonstration.
(ii) Not reasonably controllable or preventable. Although a
wildfire is unplanned, the ``not reasonably
[[Page 72869]]
controllable or preventable'' criterion still applies. Another function
of the definition of wildland is that the EPA is proposing that the
treatments of wildfires and prescribed fires on wildland with regard to
the not reasonably controllable or preventable criterion have a number
of common aspects, as described here and below in the section on
prescribed fires, because a wildland situation presents particular
considerations applicable to both fire types with respect to what
prevention or control measures may be reasonable. The EPA is not
proposing any general approach for wildfires or prescribed fires that
are not on wildland.\79\
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\79\ While we are proposing special provisions only for fires
that occur predominantly on wildland, we do not intend to restrict
fires on other types of land from receiving similar treatment. In
addressing the not reasonably controllable or preventable criterion
in a demonstration for a wildfire that is not on wildland, air
agencies should state that available resources were reasonably aimed
at suppression and avoidance of loss of life and property and that
no further efforts to control air emissions from the fire would have
been reasonable.
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Because wildfires on wildland are unplanned, fire management
agencies generally have either no advanced notice or limited and
uncertain notice, of wildfire ignition and location. In addition, many
areas of wildland are very remote and rugged, and thus not easily
reached and traversed. These factors generally limit preparation time
and on-site resources to prevent or control the initiation, duration or
extent of a wildfire. Also, by their nature, catastrophic wildfires
typically present some risk of property damage, ecosystem damage and/or
loss of life (of the public or firefighters), which is a strong
motivation for appropriate suppression and control efforts. The EPA
believes that land managers and other fire management entities have the
motivation and the best information for taking action to reasonably
prevent and limit the extent of wildfires on wildland, thus also
controlling the resulting emissions. Therefore, the EPA believes that
it is not useful to require air agencies to include in their individual
wildfire exceptional events demonstrations descriptions of prevention
and control efforts employed by burn managers to support a position
that such efforts were reasonable. To increase the efficiency of the
exceptional events process, the EPA proposes a new approach for
wildfires on wildland, under which there would be a rebuttable
presumption that every wildfire on wildland satisfies the ``not
reasonably controllable or preventable'' criterion, unless evidence in
the record demonstrates otherwise. Applying this categorical
presumption of not reasonably controllable for wildfires would involve
referencing the appropriate regulatory citation in the demonstration.
As previously stated, there will be situations in which a fire
manager could have suppressed or contained a wildfire but has allowed
the fire to continue burning through an area with a current, in-place
land management plan calling for restoration through natural fire or
mimicking the natural role of fire. The EPA recognizes that this
scenario could occur when a fire manager has a plan for acquiring
personnel and equipment to address the wildfire (either coincidentally
or because the wildfire was originally a prescribed fire) but the
manager determines that allowing the wildfire to continue burning is
safe and will conserve overall fire management resources compared to
suppressing or containing the current wildfire and then conducting a
separate prescribed burn at a later time. In such a scenario, even
though the fire would meet the definition of a wildfire and even though
we are proposing that in general wildfires will not need to be reviewed
individually against the not reasonably controllable or preventable
criterion, we would expect the fire manager to employ appropriate BSMP
as described in section V.F.2.d when possible.
(iii) Coordinated communications. Regardless of the above
considerations for wildfires, the EPA urges land managers and air
agencies to coordinate, as appropriate, in developing plans and
appropriate public communications regarding public safety and reducing
exposure in instances where wildfires are potential exceptional events
and contribute to exceedances of the NAAQS. Coordinated efforts can
help air agencies satisfy the Exceptional Events Rule obligation at 40
CFR 51.930 that air agencies must provide public notice and public
education and must provide for implementation of reasonable measures to
protect public health when an event occurs.\80\ Also, when wildfire
impacts are frequent and significant in a particular area, land
managers, land owners, air agencies and communities may be able to
lessen the impacts of wildfires by working collaboratively to take
steps to minimize fuel loading in areas vulnerable to fire.\81\ Fuel
load minimization steps can consist of both prescribed fire and
mechanical treatments, such as using mechanical equipment to reduce
accumulated understory.
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\80\ 72 FR 13575 (March 22, 2007).
\81\ One example of this collaborative approach is the evolving
interagency Wildland Fire Air Quality Response Program, which has
developed resources to help address and predict smoke impacts from
wildfires to reduce public exposure to wildfire smoke. Additional
information is available at http://www.westar.org/Docs/Business%20Meetings/Spring14/Boise/12.3%20Lahm_WFAQRP_5_28_14.pdf.
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d. Prescribed Fires
As noted previously, the EPA recognizes and acknowledges the
potential significant impact on air quality posed by catastrophic
wildfires. The use of prescribed fire on wildland can influence the
occurrence, severity, behavior and effects of catastrophic wildfires,
which may help manage the contribution of wildfires to measured ambient
pollutant levels (particularly ozone and PM concentrations).
Additionally, prescribed fires can benefit the plant and animal species
that depend upon natural fires for propagation, habitat restoration and
reproduction, as well as a myriad of ecosystem functions (e.g., carbon
sequestration, maintenance of water supply systems and endangered
species habitat maintenance). The EPA formally recognized in the 1998
Interim Air Quality Policy on Wildland and Prescribed Fires that
federal, tribal and state owners and land managers use prescribed fire
on wildland to achieve some of these resource benefits, to correct the
undesirable conditions created by past wildfire suppression management
strategies and to reduce the risk of wildfires to the public. Although
the 1998 Interim Air Quality Policy on Wildland and Prescribed Fires
focused on the role of federal, tribal and state owners/land managers,
it also recognized that prescribed fires on private lands achieve some
of the same goals. These concepts, also noted in the preamble to the
2007 Exceptional Events Rule, are summarized in more detail immediately
below. In recent regulatory actions,\82\ the EPA has continued to
express an understanding of the importance of prescribed fire, noting
that it can be used to mimic the natural process necessary to manage
and maintain existing fire-adapted ecosystems and/or return an area to
its historical ecosystem (or another natural ecosystem if the
historical ecosystem is no longer attainable) while reducing the risk
to public safety and the risk of uncontrolled emissions from
catastrophic wildfires.
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\82\ See, for example, National Ambient Air Quality Standards
for Ozone; Proposed Rule (79 FR 75234, December 17, 2014) and
Implementation of the 2008 National Ambient Air Quality Standards
for Ozone: State Implementation Plan Requirements; Final Rule (80 FR
12264, March 6, 2015).
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Current Situation. The 2007 Exceptional Events Rule recognized the
benefits of prescribed fire as
[[Page 72870]]
summarized earlier in this section and included provisions for these
event types in both the preamble to the final rule and in regulatory
language. The preamble to the 2007 Exceptional Events Rule defined a
prescribed fire as ``a fire ignited by management objectives to meet
specific resource management needs.'' This was consistent with the
definition of prescribed fire in general use by the fire management
community at the time.\83\ Also in the preamble language, the EPA
explained that prescribed fire cannot be classified as natural given
the extent of the direct human causal connection. However, the preamble
explained that a prescribed fire that causes or contributes to an
exceedance or violation of an ambient air quality standard could still
be considered an exceptional event if it satisfies all core statutory
elements of CAA section 319(b), including the ``human activity that is
unlikely to recur at a particular location'' and the ``not reasonably
controllable or preventable'' criteria.
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\83\ The October 2014 NWCG definition of ``prescribed fire'' is
similar but includes the concept that the fire is not illegal:
``[a]ny fire intentionally ignited by management actions in
accordance with applicable laws, policies, and regulations to meet
specific objectives.''
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The 2007 Exceptional Events Rule preamble further explained that
air agencies should take into account the natural fire return interval
\84\ as part of the basis for establishing that the human activity
(i.e., the prescribed fire) is ``unlikely to recur at a particular
location.'' The preamble acknowledged that the natural fire return
interval can vary widely and range from once every year to less
frequently than once every 200 years.
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\84\ The natural fire return interval is the typical number of
years between two successive naturally-occurring fires in a
specified area or ecosystem. The historical rate of return of these
fires resulted in plant communities that evolved with recurring fire
and therefore became dependent on fire for maintenance.
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When addressing the ``not reasonably controllable or preventable''
criterion, the 2007 Exceptional Events Rule preamble instructed
agencies to examine whether there are ``reasonable alternatives,'' such
as mechanical or other (e.g., chemical) treatments to the use of
prescribed fire. The preamble language recognized that, although case-
and area-specific, any number of conditions could exist that would
favor the use of prescribed fire rather than alternate treatments. Such
scenarios identified in the preamble included: significant build-up of
forest fuels in a particular area that if left unaddressed would pose
an unacceptable risk of catastrophic wildfire; pest or disease
outbreak; natural species composition dependent on a specific fire
return interval; and legal requirements precluding the use of
mechanical fuel reduction methods.
The 2007 Exceptional Events Rule also indicated, in both preamble
discussion and rule text, that to further satisfy the ``not reasonably
controllable or preventable'' criterion for prescribed fires and to
address the principle at section 319(b)(3)(A) of the CAA that the
protection of public health is the highest priority, a prescribed fire
would be considered to be an exceptional event only if the state has
certified to the EPA that it has adopted and is implementing a SMP or
the state has ensured that the burner has employed BSMP. While the EPA
did not identify in the 2007 Exceptional Events Rule the necessary
components of an SMP or what SMP certification entails, the preamble
cited the 1998 Interim Air Quality Policy on Wildland and Prescribed
Fires.\85\ This policy identified the following basic components of a
certifiable SMP: \86\
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\85\ The discussion of the 1998 Interim Air Quality Policy on
Wildland and Prescribed Fires recommendations regarding SMPs appears
in the preamble to the 2007 Exceptional Events Rule at 72 FR 13567
(March 22, 2007).
\86\ The language associated with the six basic components of a
certifiable SMP was taken directly from the 1998 Interim Air Quality
Policy on Wildland and Prescribed Fires. For context, the EPA notes
that the identified components of a certifiable SMP apply to
managing smoke from prescribed fires managed for resource benefits.
The EPA would expect burn managers to consider actions and
approaches where applicable or where appropriate rather than in all
prescribed fire scenarios.
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Authorization to Burn--includes a process for authorizing
or granting approval to manage fires for resource benefits within a
region, state or on Indian lands and identify a central authority
responsible for implementing the program. The authorization process
could include burn plans that consider air quality and the ability of
the airshed to disperse emissions from all burning activities on the
day of the burn.
Minimizing Air Pollutant Emissions--encourages wildland
owners/managers to consider and evaluate alternative treatments to
fire, but if fire is the selected approach to follow emission reduction
techniques.
Smoke Management Components of Burn Plans--identifies the
following components if the SMP requires burn plans: Actions to
minimize fire emissions, evaluate smoke dispersion, public notification
and exposure reduction procedures and air quality monitoring.
Public Education and Awareness--establishes the criteria
for issuing health advisories when necessary and procedures for
notifying potentially affected populations.
Surveillance and Enforcement--includes procedures to
ensure that wildland owners/managers comply with the SMP.
Program Evaluation--provides for periodic review by all
stakeholders of the SMP effectiveness and program revision as
necessary.
The 1998 Interim Air Quality Policy on Wildland and Prescribed
Fires also noted, regarding the certification process for SMPs, that to
receive special consideration for air quality data whose concentrations
were influenced by prescribed fires, ``[t]he State/tribal air quality
manager must certify in a letter to the Administrator of EPA that at
least a basic [smoke management] program has been adopted and
implemented . . . .'' The 1998 Interim Air Quality Policy on Wildland
and Prescribed Fires further identified that federal agencies intending
to use prescribed fire should operate under an approved prescribed fire
plan and meet the National Environmental Policy Act (NEPA)
requirements, where applicable, prior to ignition.\87\
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\87\ In specifying the basic components of certifiable SMPs that
would include the requirement for agency approval of prescribed fire
plans, the 1998 Interim Air Quality Policy on Wildland and
Prescribed Fires noted that SMPs can mitigate the nuisance and
public safety hazards associated with smoke from prescribed fires
intruding into populated areas, prevent deterioration of air quality
and NAAQS violations and address visibility impacts in mandatory
Class I Federal areas. Since the EPA issued the Interim Policy in
1998, some federal agencies have reported to us their assessment
that some states and/or local air agencies have managed their SMP
(or other regulatory programs) in such a way as to exclude the use
of prescribed fires in areas to such an extent that fuels have
continued to accumulate to levels that increase the likelihood of
catastrophic wildfires.
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The EPA did not use the preamble to the 2007 Exceptional Events
Rule to expand on the concept of using BSMP in lieu of an SMP. Rather,
the EPA only noted that burners could use BSMP to minimize emissions
and control the impacts of fire. Although the EPA identified several
example BSMP in a footnote in the preamble (footnote 12 at 72 FR
13567), we also committed to developing the concept when we updated the
guidance in the 1998 Interim Air Quality Policy on Wildland and
Prescribed Fires. The EPA has not revised this guidance and does not
currently plan to do so. Although some states have developed
demonstrations that incorporate BSMP employed for a specific prescribed
fire and/or referenced BSMP in their SMPs, the EPA has not in any other
more recent guidance clarified what it means for an
[[Page 72871]]
air agency or burner to have a certified SMP in place and/or to
implement BSMP.
In addition to conditioning the approval of a prescribed fire as an
exceptional event on the existence and implementation of a certified
SMP or the actual use of BSMP, as described above, the 2007 Exceptional
Events Rule also requires that ``[i]f an exceptional event occurs using
the basic smoke management practices approach, the State must undertake
a review of its approach to ensure public health is being protected and
must include consideration of development of a SMP.'' To date, air
agencies have submitted few exceptional events demonstrations for
prescribed fires. One recent submission came from Kansas, a state
already operating an SMP.\88\
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\88\ Treatment of Data Influenced by Exceptional Events:
Exceptional Events Submissions Table. U.S. Environmental Protection
Agency, Research Triangle Park, NC. See links associated with
``April 2011 Fires'' in the ozone section of the table available at
http://www2.epa.gov/air-quality-analysis/exceptional-events-submissions-table.
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The 2007 Exceptional Events Rule at 40 CFR 50.14(b)(3) allows for
the exclusion of data where a state demonstrates to the EPA's
satisfaction that emissions from prescribed fires caused a specific air
pollution concentration in excess of one or more NAAQS at a particular
air quality monitoring location and otherwise satisfies the
requirements in the Exceptional Event Rule. The regulatory language
also requires that the subject prescribed fire meets the definition in
40 CFR 50.1(j) and requires that the state has certified to EPA that it
has adopted and is implementing a Smoke Management Program or the state
has ensured that the burner employed basic smoke management practices.
The definition of an exceptional event at 40 CFR 50.1(j) includes the
requirement that an event ``is not reasonably controllable or
preventable.'' Thus, the EPA has interpreted that a demonstration for a
prescribed fire independently address both the SMP/BSMP element and the
not reasonably controllable or preventable criterion. We have not
indicated that meeting the SMP/BSMP condition is sufficient to satisfy
the not reasonably controllable or preventable criterion.
Proposed Changes. As previously noted, the EPA has not to date
clarified fire-related definitions or its expectations regarding SMPs
or BSMP in rule or preamble form. This uncertainty has created
confusion for air and fire management agencies trying to develop fire-
related plans and/or apply fire management practices for prescribed
fires. It has also created confusion for air agencies when developing
and submitting exceptional events demonstrations for both wildfires and
prescribed fires.
To assist air agencies in documenting an exceptional events package
for a prescribed fire on wildland, the EPA proposes to clarify its
expectations for a satisfactory demonstration, as follows.
(i) Definition of a prescribed fire. We are proposing to adopt in
rule language the current NWCG-recommended definition of a prescribed
fire: ``[a]ny fire intentionally ignited by management actions in
accordance with applicable laws, policies and regulations to meet
specific objectives.'' In this definition, ``management'' refers to the
owner or manager of the land area to which prescribed fire is applied,
and ``specific objectives'' refers to specific land or resource
management objectives.
(ii) Events caused by human activity. We are proposing to say in
rule form that prescribed fires are events caused by human activity.
Thus, to be considered an exceptional event, every prescribed fire
demonstration must address the ``human activity unlikely to recur at a
particular location'' criterion.
(iii) Unlikely to recur at a particular location. As discussed in
more detail in section V.E.1 of this proposal, this requirement of CAA
section 319(b) is not specific and requires interpretation on a case-
by-case or event type-by-event type basis. The term ``unlikely''
implies consideration of the expected future frequency of events
similar to the event that has already happened, but does not convey any
particular benchmark for what frequency should be low enough to be
considered ``unlikely.'' Also, the term ``at a particular location''
requires interpretation, as it could refer to the exact area or only to
the general area of the event, to the location of the ambient
monitoring station or stations that were affected by the event or to
the combination of both.
As was our position in 2007, we continue to believe that the
natural fire return interval is a useful and appropriate benchmark for
a satisfactory demonstration that a prescribed fire is unlikely to
recur at a particular location, in the sense that if a planned program
of prescribed fire calls for the application of prescribed fire at a
similar interval to the natural fire return interval at given locations
then each prescribed fire conducted in that program can be considered
not likely to recur at its particular location. However, we now believe
based on experience and further consideration that the natural fire
return interval is not the only appropriate benchmark. It can be
difficult in some cases to determine what fire return interval
prevailed under natural conditions, which may not have existed for
decades or even hundreds of years in a particular area. Also, in some
cases environmental conditions may have changed, for example due to
climate change, such that the original natural ecosystem cannot
realistically be restored and the well-considered land management goal
instead may be the development and maintenance of a sustainable and
resilient ecosystem that is different than what historically existed
and that will likely reduce the risk of catastrophic wildfire. In such
a case, the frequency of prescribed fire needed to establish or restore
such an ecosystem during a transitional period and/or the frequency
needed to sustain the resilient ecosystem may be different than the
natural fire return interval that once prevailed. It is also important
to consider issues of fire personnel and public safety and protection
of nearby property. Land managers may need to apply prescribed fire at
a frequency that maintains the accumulation of fuel loading between
prescribed fires at a level that does not create the risk of a
dangerous wildfire.
Accordingly, the first proposed change for prescribed fires on
wildland is to include in the rule text two benchmarks for the expected
future frequency of prescribed fires on wildland to meet the not likely
to recur criterion: (1) The natural fire return interval as articulated
in the 2007 preamble and (2) the prescribed fire frequency needed to
establish, restore and/or maintain a sustainable and resilient wildland
ecosystem. If finalized, an air agency could include information
provided by the land manager with respect to the appropriate benchmark
for a prescribed fire on wildland as the basis for satisfying the human
activity unlikely to recur at a particular location criterion in its
exceptional events demonstration.\89\
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\89\ The benchmarks for the expected frequency of prescribed
fires not on wildland would be assessed on a case-by-case basis.
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Successfully implementing one of these benchmarks for prescribed
fire frequency necessitates that the air agency and the land manager
collaborate to establish and document the appropriate fire return
interval or frequency in a submitted demonstration. Federal agencies
that use prescribed fire to manage lands for which they are responsible
generally prepare multi-year plans for the use of prescribed fire in a
given national park, national forest, armed forces base or other land
area. Many of these plans include an
[[Page 72872]]
objective to establish, restore and/or maintain a sustainable and
resilient wildland ecosystem and incorporate the best science available
to determine what prescribed fire cycle will accomplish this.\90\ Some
tribes, private landowners (and federal, state and local agencies
working with private landowners) and state agencies that manage state-
owned lands (e.g., state parks) also prepare multi-year management
plans. While plans developed by public agencies (i.e., state and
federal agencies) often undergo public comment prior to being
finalized, the plans developed by tribes and private landowners may not
follow a public comment process. However, public agencies often work
with tribes and private owners to develop these plans, which are based
on conservation practices and standards that have often undergone
public comment as part of the state or federal agency process.
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\90\ An example of a federal land management plan that considers
the need for the use of prescribed fire is the Land and Resource
Management Plan for the Kaibab National Forest, Coconino, Yavapai,
and Mojave Counties, Arizona, USDA Forest Service Southwestern
Region, MB-R3-07-17, February 2014, available at http://www.fs.usda.gov/Internet/FSE_DOCUMENTS/stelprd3791580.pdf.
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The EPA understands that multi-year plans incorporate factors
relevant to identifying and selecting the areas and times under which
management will initiate a specific prescribed fire. The EPA also
recognizes that evaluating the behavior and results of prior prescribed
fires aids in determining the frequency and need for future prescribed
fire in a given area. In addition, personnel and equipment must be
available on site, which cannot be specifically planned far in advance.
Thus, it is typical for multi-year plans to identify somewhat general
targets for the frequency of prescribed fire use and for specific burn
plans. Even then, unexpected differences between planned and actual
fire behavior, landscape or ecosystem characteristics, fuel loading
patterns and weather patterns may cause management to deviate from the
general plan and/or the specific burn plan. Therefore, when the EPA
reviews an exceptional events demonstration for a prescribed fire
conducted under a wildland management plan, we intend to compare the
actual time pattern of prescribed fires on the land with the pattern
described in the applicable multi-year plan in a general way, rather
than treating the multi-year plan as containing a specific schedule to
which management must adhere. For example, if the wildland management
plan identified an approximate 5-year burn interval, the EPA would not
disapprove a demonstration if the burn occurred on a 4-year or a 6-year
interval.
Therefore, we are proposing in rule text that we will consider a
demonstration's referencing of a multi-year land or resource management
plan \91\ (and including either a copy or an internet link to the plan)
with a stated objective to establish, restore and/or maintain a
sustainable and resilient wildland ecosystem and/or to preserve
endangered or threatened species that also identifies the subject area
as a candidate for prescribed fire to be dispositive evidence that a
particular fire conducted in accordance with such a plan satisfies the
``unlikely to recur at a particular location'' criterion. We would also
consider a demonstration's referencing of a fire management plan for
tribal or private lands that has been reviewed and certified by the
appropriate fire and/or resource management professionals and agreed to
and followed by the land owner/manager to be sufficient evidence
satisfying the ``unlikely to recur at a particular location''
criterion.
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\91\ These plans could also include fire management plans,
prescribed fire on wildland management plans, landscape management
plans or equivalent public planning documents.
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(iv) Not reasonably controllable or preventable. Consistent with
current practice and 2007 preamble/rule language, the EPA considers it
appropriate to allow air agencies to rely on an in-place and
implemented state-certified SMP to satisfy the controllability prong of
the ``not reasonably controllable or preventable'' criterion. The EPA
proposes to incorporate the six elements of SMPs discussed in the 1998
Interim Air Quality Policy on Wildland and Prescribed Fires and
referenced in the preamble to the 2007 Exceptional Events Rule into the
preamble of the final rule for this proposal, where it would serve as
guidance. That is, at a minimum, a state-certified SMP would include
provisions for (i) authorization to burn, (ii) minimizing air pollutant
emissions, (iii) smoke management components of burn plans, (iv) public
education and awareness, (v) surveillance and enforcement, and (vi)
program evaluation. Certification would require that the air agency
certify in a letter to the Administrator of the EPA, or a Regional
Administrator, that it has adopted and is implementing a SMP.\92\
Alternatively, the EPA solicits comment on incorporating these SMP
elements into rule text language. The EPA proposes to accept as
sufficient the testimony of the air agency submitting an exceptional
events demonstration that the SMP is being implemented, provided that
prior to the EPA's acting on a demonstration, the record contains no
clear evidence to the contrary.
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\92\ The EPA anticipates that any person within an air agency
responsible for submitting exceptional events demonstrations or SIP
revisions could also be responsible for certifying a Smoke
Management Program.
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Consistent with current practice and 2007 preamble and rule
language, the EPA also considers it appropriate to allow air agencies
to rely on a burn manager's use of BSMP that minimize emissions and
control impacts, in lieu of a state-certified SMP, to satisfy the
controllability prong of the ``not reasonably controllable or
preventable'' criterion. To provide clarity and reduce uncertainty for
air agencies and burn managers, the EPA proposes to identify in the
rule text six BSMP practices as being generally applicable for
exceptional events purposes for prescribed fires on wildland as well as
other prescribed fires. The six BSMP, listed and described in more
detail in Table 3, come from guidance on BSMP for prescribed burns
provided by the U.S. Department of Agriculture (USDA) Forest Service
(USFS) and USDA Natural Resources Conservation Service (NRCS).\93\ Land
managers of other federal, state and local agencies and private land
owners generally endorse and follow this BSMP guidance.\94\ While the
listed practices are broadly stated, fire managers use site-specific
considerations to select the exact actions of each type and apply them
to specific burn projects. There may be situations in which one or more
of the six BSMP is clearly not applicable for a particular prescribed
burn--for example, if a prescribed fire is so remote that there are no
neighbors to be notified. The EPA generally does not intend to
challenge a burn manager's selection of the intensity or specific
measure within the BSMP categories when we review a particular
exceptional events demonstration. As part of the on-going assessment of
our
[[Page 72873]]
regulatory programs, we intend to generally review those practices
commonly employed by federal agencies and other users of prescribed
fire.
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\93\ USDA Forest Service and Natural Resources Conservation
Service, Basic Smoke Management Practices Tech Note, October 2011,
http://www.nrcs.usda.gov/Internet/FSE_DOCUMENTS/stelprdb1046311.pdf.
\94\ The EPA also addressed how federal agencies may use basic
smoke management practices to establish a presumption of conformity
in the preamble to the EPA's General Conformity Rule at 40 CFR
93.153(g)-(i) (75 FR 17264, April 5, 2010). The six practices
identified in Table 3 are not a presumed to conform action for
purposes of a federal agency satisfying their General Conformity
responsibilities. For basic smoke management practices to provide a
presumption of conformity, the identified basic smoke management
practices must be publicly and state reviewed as part of a presumed
to conform action under 40 CFR 93.153(g) or (f) of the General
Conformity Rule.
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As another component of the approach for prescribed fires on
wildland, the EPA is proposing to accept as evidence of the actual use
of BSMP the fire manager's statement that he or she employed applicable
BSMP for a prescribed fire. Documentation of such statement for an
exceptional events demonstration could consist of a copy of the routine
post-burn report or a letter prepared by the fire manager (see example
content of a burn report in Table 4). The EPA and other federal
agencies will work collaboratively to provide access to such post-burn
reports by air agencies that need them. We encourage land managers and
other organizations that employ prescribed fires to work with states
and tribes to develop an efficient process to provide air agencies with
documentation that BSMP were employed for particular prescribed fires.
Table 3--Summary of Basic Smoke Management Practices, Benefit Achieved
With the BSMP, and When It Is Applied
[before, during or after ignition of the burn] \a\
------------------------------------------------------------------------
When the BSMP is
Basic smoke management Benefit achieved applied--before/
practice with the BSMP during/after the
burn
------------------------------------------------------------------------
Evaluate Smoke Dispersion Minimize smoke Before, During,
Conditions. impacts. After.
Monitor Effects on Air Be aware of where Before, During,
Quality. the smoke is going After.
and degree it
impacts air quality.
Record-Keeping/Maintain a Retain information Before, During,
Burn/Smoke Journal. about the weather, After.
burn and smoke. If
air quality
problems occur,
documentation helps
analyze and address
air regulatory
issues.
Communication--Public Notify neighbors and Before, During.
Notification. those potentially
impacted by smoke,
especially
sensitive receptors.
Consider Emission Reduction Reducing emissions Before, During,
Techniques. through mechanisms After.
such as reducing
fuel loading can
reduce downwind
impacts.
Share the Airshed-- Coordinate multiple Before, During,
Coordination of Area burns in the area After.
Burning. to manage exposure
of the public to
smoke.
------------------------------------------------------------------------
\a\ The EPA believes that elements of these BSMP could also be practical
and beneficial to apply to wildfires for areas likely to experience
recurring wildfires.
Table 4--Elements That may be Included in Burn Plans and Post-Burn
Reports for Prescribed Fires Submitted as Exceptional Events
------------------------------------------------------------------------
Element Burn plan Post-burn report
------------------------------------------------------------------------
Fire Name \a\............... X................... X.
Permit number (if X................... X.
appropriate).
Latitude/longitude and X................... X.
physical description.
Date of burn, ignition time X................... X.
and completion time
(duration of burn).
AQI status on burn day, if Predicted........... Actual.
available (both in the
vicinity of the fire and in
the affected upwind area).
Acres burned................ Planned............. Actual (blackened).
Description of fuel loading. Estimated........... Actual (tons
consumed).
Meteorological data (weather Predicted conditions Actual conditions
conditions, wind speed and (including (including actual
direction, dispersion). predicted dispersion).
dispersion).
Smoke Impacts............... Anticipated smoke Observed or reported
impacts. smoke impacts
(include nature,
duration, spatial
extent and copies
of received
complaints).
BSMP actions to reduce Expected BSMP Actual BSMP actions.
impacts. actions.
Recommendations for future .................... X.
burns in similar areas.
Analytics (modeled/actual .................... X.
fire spread, satellite
imagery and analysis,
webcam/video, PM/ozone
concentrations over the
course of the fire).
------------------------------------------------------------------------
\a\ The ``Fire Name'' should be unique and referenced, to the greatest
extent possible, in all exceptional events-related documentation,
including the event name in AQS. The fire name could simply consist of
the county and state in which the burn occurred (e.g., County X, State
Y Prescribed Burn on Date Z) if no other name has been assigned.
States with certified SMPs typically have robust communications
between officials concerned with air quality impacts and officials and
members of the public who use prescribed fire. These groups communicate
during the development of the SMP, during the day-to-day burn
authorization process and in the periodic review and potential revision
of the SMP. States that instead rely on fire managers employing BSMP on
a more individual basis may not have
[[Page 72874]]
such regularly occurring communications processes, particularly in
states in which state legislation gives the leadership of fire
management to a forestry or public safety agency rather than to an air
agency. We encourage all agencies and managers/owners involved in land,
air quality and fire management to develop good communications about
both fire use practices in general and plans for specific prescribed
fires with use of BSMP. This will, among other benefits, allow them to
better coordinate on public air quality notice efforts and, if
necessary, public health advisories should smoke enter an inhabited
area. Additionally, the EPA encourages the development of ``prescribed
fire councils,'' comprised of federal, state, tribal, private and other
stakeholders to coordinate activities involving fire planning issues
and, thus, minimize or prevent smoke impacts while using prescribed
fire to accomplish land management objectives.\95\ However, we are not
proposing that notifications between prescribed fire users and specific
types of state agencies be a condition for approval of a prescribed
fire as an exceptional event.
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\95\ See additional information on prescribed fire councils on
the Coalition of Prescribed Fire Councils, Inc. Web site at http://www.prescribedfire.net/membership/state-councils.
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As previously stated, to date we have considered the existence and
implementation of a SMP or the use of BSMP to be a necessary part of
the supporting evidence needed to satisfy the not reasonably
controllable or preventable criterion, but we have not clearly
addressed what conditions are minimally sufficient to satisfy the
criterion. The remainder of this section focuses on that issue.
Because prescribed fires are intentionally initiated, clarifying
the minimal conditions for the not reasonably preventable prong is
particularly relevant. The detailed USFS/NRCS guidance on the fifth
listed BSMP, Consider Emission Reduction Techniques, includes the
potential to reduce the fuel loading. It does not suggest that it may
be reasonable to not ignite a particular prescribed fire (i.e., that
the fire be prevented), because this guidance is aimed at those fires
that are already planned to happen. Similarly, SMPs address
coordination of previously planned prescribed fires and typically do
not ask SMP participants to consider whether particular prescribed
fires are reasonably preventable. Therefore, we do not believe that the
existence of an SMP or the use of BSMP is a sufficient basis for
concluding that a prescribed fire is not reasonably preventable. A
prescribed fire should be concluded to be not reasonably preventable on
the basis of the benefits that would be foregone if it were not
conducted, as described below.
For federal agencies, the planning of prescribed fire programs
typically happens through the development of multi-year plans that
focus on specific land or resource management objectives. This planning
process, and the resulting multi-year plan, typically considers the
importance of a prescribed fire program to achieving land management
goals, which may include an objective to establish, restore and/or
maintain a sustainable and resilient wildland ecosystem, in light of
the availability, cost and effectiveness of other approaches to fuel
management. The final multi-year plans thus generally identify the
level of prescribed fire use necessary to achieve those goals. As noted
previously, some tribes, private landowners (and federal, state and
local agencies working with private landowners) and state agencies that
manage state-owned lands (e.g., state parks) also prepare multi-year
management plans. While plans developed by public agencies (i.e., state
and federal agencies) often undergo public comment prior to being
finalized,\96\ the plans developed by tribes and private landowners may
not follow a public comment process. However, public agencies often
work with tribes and private owners to develop these plans, which are
based on conservation practices and standards that have often undergone
public comment as part of the state or federal agency process. Not
conducting the prescribed fire programs described in such plans could
mean forgoing important ecosystem services and other benefits.
Accordingly, the EPA is proposing in rule text form to consider a
prescribed fire on wildland conducted in accordance with a multi-year
fire management plan that has an objective to establish, restore and/or
maintain a sustainable and resilient wildland ecosystem to be not
reasonably preventable, provided there is no compelling evidence to the
contrary in the record when the EPA approves the associated exceptional
events demonstration.\97\
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\96\ Many multi-year plans developed by state and federal
agencies are available electronically online or can be requested
directly from the preparing agency. Interested parties can also
request electronic versions of project level plans, if they are not
available online.
\97\ On a case-by-case basis, in the absence of a multi-year
plan, the EPA would also consider a prescribed fire on wildland
conducted on a fire return interval established according to
scientific literature to satisfy the not reasonably controllable or
preventable criterion provided the prescribed fire was also
conducted with the objective to establish, restore and/or maintain a
sustainable and resilient wildland ecosystem and conducted in
compliance with either a state-certified SMP or BSMP. This case-by-
case approach is similar to the approach currently used under the
2007 Exceptional Events Rule.
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We also propose in rule text that compliance with either a state-
certified SMP or BSMP is sufficient to establish that a prescribed fire
was not reasonably controllable, provided there is no compelling
evidence to the contrary in the record when the EPA concurs with the
associated exceptional events demonstration. This is an appropriate
approach to implementing CAA section 319(b), because SMPs and BSMP aim
to reasonably control the air quality impacts of prescribed fires.\98\
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\98\ With respect only to the not reasonably controllable prong,
we also believe that the SMP and BSMP approach each is sufficient
for prescribed fires that are not on wildland.
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This two-part categorical approach would reduce the length of
exceptional events demonstrations for prescribed fires on wildland and
make the demonstration preparation and review process more resource
efficient. In summary, to satisfy the not reasonably controllable or
preventable criterion for a prescribed fire on wildland, a
demonstration would need to identify that the prescribed burn was
conducted in accordance with a multi-year plan that has an objective of
the establishment, restoration and/or maintenance of a sustainable and
resilient wildland ecosystem and was conducted in compliance with
either a state-certified SMP or BSMP.
Finally, we are proposing to remove the phrase ``and must include
consideration of development of a SMP'' from the sentence of the
existing text of 40 CFR 50.14(b)(3) that reads, ``If an exceptional
event occurs using the basic smoke management practices approach, the
State must undertake a review of its approach to ensure public health
is being protected and must include consideration of development of a
SMP.'' While the EPA supports states considering the development of a
SMP in the situation described in this sentence, we believe states have
had ample opportunity to develop such a program since 2007. This rule
language effectively requires an ongoing consideration to develop an
SMP every time a prescribed fire causes a NAAQS exceedance or violation
that merits exclusion as an exceptional event. We do not believe
Congress intended this ongoing consideration to be a requirement
flowing from CAA section 319(b). In addition, we believe that an
[[Page 72875]]
SMP is most appropriate when multiple parties wish to employ prescribed
fire at about the same time in the same airshed, which is a more narrow
situation than specified in this sentence. We also do not want our
rules to be open to an inference that development of a SMP should only
be considered following a NAAQS exceedance or violation, because the
impacts from fires may affect public health in areas without NAAQS-
compliance air monitoring stations. Also, we believe that when air
agencies observe NAAQS exceedances or violations attributed to a
prescribed fire, air agencies should consider a wide range of
alternatives including, but not limited to, the development of a SMP.
For example, agencies might also consider the more frequent or
intensive use of BSMP to limit the fuel available to burn in each fire.
The EPA solicits comment on all aspects of the identified fire-
related approaches.
3. Stratospheric Ozone Intrusions
a. Current Situation
Stratospheric ozone intrusions are natural events that occur when a
parcel of air originating in the stratosphere is re-entrained into the
troposphere, and in some cases mixes directly to the surface of the
earth. These relatively rare events can create elevated ozone
concentrations that affect areas ranging from a single monitoring site
to a wider area as the air mass with a high ozone concentration moves
across the landscape.
Normally, the tropopause, the temperature inversion layer of air
that separates the troposphere from the stratosphere, limits the
transport of stratospheric air into the troposphere, the lowest layer
of the Earth's atmosphere.\99\ In some cases, however, parcels or
ribbons of ozone-rich air from the stratosphere can be transported
rapidly to the surface during deep mixing events, such as thunderstorms
or strong frontal passages, by a process known as tropopause folding.
Although this ``folding'' process can occur throughout the year, it is
typically associated with frontal passages and upper level low pressure
systems during the spring season.100 101 The ozone
transported through these ``folds,'' or through other less significant
mechanisms, may disperse within and be destroyed in the upper
troposphere or it may mix down to the surface.\102\ The ``intrusion''
of stratospheric ozone is identified most frequently at high elevation
sites where upper tropospheric air is more likely to reach the surface
than at lower elevation sites where more downward movement would be
needed for a monitoring site to be affected. At these high elevation
sites in particular, stratospheric ozone intrusion has been estimated
to contribute about 20 to 25 percent of the total tropospheric ozone
budget and can cause relatively short-term (i.e., ranging from several
hours to 2-3 days in duration) increases of surface ozone of 10 to 50
ppb above normal background levels.\103\ Stratospheric intrusions with
short-lived surface ozone concentrations of several hundred ppb have
also been observed, although these events are extremely rare.
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\99\ The height of the tropopause varies with latitude and
season but the average height at mid-latitudes is about 11
kilometers (km) (7 miles or 36,000 feet). The stratosphere, the
second layer of the Earth's atmosphere, is located above the
tropopause at 13 to 50 km (8-31 miles or 43,000 to 160,000 feet)
above the Earth's surface.
\100\ Pan, L. L., et al. (2014), ``Thunderstorms enhance
tropospheric ozone by wrapping and shedding stratospheric air.''
Geophys. Res. Lett., 41, 7785-7790, doi:10.1002/2014GL061921.
\101\ A. O. Langford, K. C. Aikin, C. S. Eubank and E. J.
Williams. Stratospheric Contribution to High Surface Ozone in
Colorado During Springtime, Geophysical Research Letters, Vol. 36,
Issue 12, June 2009.
\102\ Other mechanisms by which stratospheric ozone is
transported into the troposphere include cutoff cyclones, streamers
(long filamentary structures that often roll into vortices), and
clear air turbulence (see http://www.atmos.umd.edu/~dkuhl/documents/
Kuhl_Tropopause_Folding.ppt).
\103\ Integrated Science Assessment of Ozone and Related
Photochemical Oxidants (Final Report). U.S. EPA.Washington, DC EPA/
600/R-10/076F. Available at: http://www3.epa.gov/ttn/naaqs/standards/ozone/s_o3_2008_isa.html.
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Because stratospheric intrusion events are relatively infrequent
and because identifying and monitoring these events are challenging,
there have been few direct measurements showing that a given parcel of
surface air contains stratospheric ozone (versus ozone generated by
local natural or anthropogenic sources). Interpreting these direct
measurements is also challenging. One approach to confirm the presence
of stratospheric ozone in surface air is through the use of the
beryllium tracers, beryllium isotopes Be-7 and Be-10, which are
produced primarily in the stratosphere by cosmic ray collisions with
atmospheric gas atoms.\104\ Beryllium isotope measurements are,
however, rare and expensive, and, consequently not normally available.
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\104\ Cristofanelli, P. A 6-year analysis of stratospheric
intrusions and their influence on ozone at Mt. Cimone (2165 m above
sea level). Journal of Geophysical Research, Vol. 111, D03306,
doi:10.1029/2005JD006553, 2006.
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More common approaches to identify stratospheric ozone in surface
air can include evaluating measurements at the potentially influenced
ozone monitoring site for very low concentrations of CO and/or relative
humidity. Both can be strong indicators of stratospheric air because,
relative to tropospheric air, stratospheric air has very low relative
humidity and very low concentrations of other air pollutants such as
CO, NOX and PM. The concurrent impacts on CO and relative
humidity can be subtle, however, when stratospheric air has mixed with
tropospheric air as the mixing process dilutes the ozone enhancement
and increases CO and water vapor concentrations relative to
stratospheric conditions. Typical CO monitors used for ambient air
monitoring have operational ranges of 500 to 50,000 ppb (0.5 to 50 ppm)
and are not sufficiently sensitive to reliably measure the very low CO
levels found in stratospheric air (50 to 150 ppb). Additionally, few
rural high altitude monitoring sites have both ozone and CO
monitors.\105\ The EPA urges air agencies to provide concurrent
readings of ozone and CO and/or relative humidity in their exceptional
events demonstrations if they have these data. The EPA will evaluate
these data as a part of a weight of evidence showing alongside other
qualitative evidence in a clear causal relationship showing.
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\105\ A recent review of AQS data revealed 216 sites in the
United States with collocated ozone and carbon monoxide monitors in
operation after January 1, 2014. Most of these sites are located in
either urban or suburban locations. In these settings, local
emissions would likely hide the stratospheric CO suppression.
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A third measurement-based approach to identifying stratospheric
ozone could include measurements of ozone above ground level (i.e.,
measurements in the troposphere). This approach is also uncommon.
Currently, five sites in the U.S. conduct ozone sonde (balloon)
launches two or more times per week and an additional few research
locations operate ozone lidars to vertically measure ozone
profiles.106 107
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\106\ Lidar, which stands for Light Detection and Ranging, is a
remote sensing method that uses light in the form of a pulsed laser
to measure ranges (variable distances) to the Earth. These light
pulses, combined with other data recorded by the airborne system,
generate precise, three-dimensional information about the shape of
the Earth and its surface characteristics. See, NOAA definition at
http://oceanservice.noaa.gov/facts/lidar.html.
\107\ See NOAA data available at ftp://aftp.cmdl.noaa.gov/data/ozwv/Ozonesonde. On April 30, 2015, NOAA's site identified the
following five sites in the U.S. that conduct bi-weekly ozone sonde
launchings: Hilo, HI; Huntsville, AL; Narragansett, RI; Trinidad
Head, CA; and Boulder, CO. Additional launchings occur in Pago Pago,
American Samoa, and outside of the U.S. in Greenland, Antarctica and
Fiji.
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In the absence of direct measurements of stratospheric tracers at
ground level,
[[Page 72876]]
meteorological models can indicate conditions under which stratospheric
air parcels may reach the surface. Meteorological models such as the
National Oceanic and Atmospheric Administration (NOAA)/National Weather
Service (NWS) North American Mesoscale Forecast System (NAM) or the
NOAA Rapid Update Cycle (RUC) models simulate parameters characteristic
of stratospheric air such as isentropic potential vorticity (IPV) and
potential temperature (PT) that can be used to identify tropopause
folding. Visualization tools using the model output can show spatially
where stratospheric air is located in proximity to or in contact with
the surface. Similarly, atmospheric chemistry models, such as the
National Aeronautics and Space Administration (NASA)/NOAA Real-time Air
Quality Modeling System (RAQMS) \108\ can provide both real time
intrusion forecasting and retrospective analysis of ozone from
intrusions. Finally, satellite observation of atmospheric ozone and CO
can be used to validate predictions based on atmospheric modeling.
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\108\ See http://raqms-ops.ssec.wisc.edu/.
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Although as of the date of this proposal the EPA has concurred with
only one stratospheric ozone intrusion exceptional events demonstration
prepared under the provisions of the 2007 Exceptional Events Rule (and
disapproved none),\109\ the EPA has been communicating that we consider
it appropriate to use the previously mentioned stratospheric ozone
tools with other event/pollutant exceptional events analyses (e.g.,
seasonal analysis of ozone data, comparison of event days with non-
event days, trajectory analysis, ozone measurement time series and
spatial distribution analysis, meteorological analysis to show the
presence of weather systems associated with typical intrusions and
balloon soundings of the NWS Upper Air Observation Program to detect
parcels of dry air aloft) to successfully demonstrate stratospheric
ozone exceptional events.
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\109\ Wyoming Department of Environmental Quality, Air Quality
Division. Big Piney and Boulder, Wyoming Ozone Standard Exceedance,
June 14, 2012. Available at http://www2.epa.gov/air-quality-analysis/exceptional-events-submissions-table.
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b. Proposed Changes
As is true for all exceptional events and pollutant combinations,
when submitting a demonstration for stratospheric ozone intrusion
events, air agencies must address all of the Exceptional Events Rule
criteria. As noted in this action, the EPA proposes to return to the
core statutory elements and implicit concepts of CAA section 319(b):
That the event affected air quality in such a way that there exists a
clear causal relationship between the specific event and the monitored
exceedance or violation, the event was not reasonably controllable or
preventable and the event was a human activity that is unlikely to
recur at a particular location or was a natural event. The EPA suggests
the following approach when addressing these technical criteria for an
ozone exceedance or violation caused by a stratospheric intrusion.
An air agency should begin by showing the geographic extent of
elevated or exceedance-level ozone concentrations associated with the
intrusion event in conjunction with an evaluation of the historical
measured surface ozone levels for the same season (see section V.E.3 of
this proposal for example analyses of how to present the comparison to
historical concentrations within the clear causal relationship
criterion). If the intrusion happened at a time of year when local or
transported photochemical ozone is generally low, evidence that the
intrusion affected ground level air quality may be relatively brief and
still be sufficient, compared to an intrusion occurring at the height
of the historical ozone season.
If intrusion claims coincide with historically high photochemistry
seasons, then the air agency may need additional evidence to support
the clear causal relationship criterion by showing the relative
contribution estimates to the exceedance from local and transported
anthropogenic pollutants compared to the intrusion contribution. An air
agency can provide additional analyses supporting the clear causal
relationship by showing that an intrusion occurred at or near the
location of an identified monitor by using atmospheric models such at
RAQMS, NAM or RUC, with additional data from satellite observations of
total column ozone and CO.
The EPA intends to accept a short statement in a demonstration that
because stratospheric ozone intrusions are purely natural events and
are large in scale, they are not reasonably controllable or
preventable.
4. High Wind Dust Events
a. Current Situation
The 2007 Exceptional Events Rule preamble noted that ``[t]he EPA's
final rule concerning high wind events states that ambient particulate
matter concentrations due to dust being raised by unusually high winds
will be treated as due to uncontrollable natural events where (1) The
dust originated from nonanthropogenic sources, or (2) the dust
originated from anthropogenic sources within the State, that are
determined to have been reasonably well-controlled at the time that the
event occurred, or from anthropogenic sources outside the State.'' As
noted in section IV.B of this document, although this language still
reflects the EPA's interpretation of what might be appropriate under
the Exceptional Events Rule, the D.C. Circuit determined the language
to be a legal nullity because the EPA did not specifically address high
winds or ambient particulate matter concentrations in the promulgated
regulatory language in 40 CFR 50.14.
The preamble to the 2007 Exceptional Events Rule also noted that
because ``. . . the conditions that cause or contribute to high wind
events vary from area to area with soil type, precipitation, and the
speed of wind gusts, [air agencies] should provide appropriate
documentation which indicates what types of circumstances contributed
to the exceedances or violation at the monitoring site in question.''
The EPA declined to identify a specific high wind threshold to qualify
as being an exceptional event and instead relied on air agencies to
submit appropriate documentation supporting their position.
Because of the uncertainty associated with these high wind
statements and stakeholder feedback asking the EPA to interpret this
language and provide examples of applying the provisions in the 2007
Exceptional Events Rule to high wind dust events, the EPA clarified
many concepts related to high wind dust events in its May 2013 Interim
Exceptional Events Implementation Guidance, specifically the Interim
High Winds Guidance document.\110\ In this guidance, the EPA defined a
high wind dust event as including the high wind and the dust that the
wind entrains and transports to a monitoring site, clarified our
expectations regarding ``reasonable controls'' for high wind events
with contribution from both natural and anthropogenic sources and
introduced the concept of establishing a value for a high wind
threshold, up to which reasonable windblown dust controls are
[[Page 72877]]
expected to be effective in the absence of site specific data or
analyses.
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\110\ Interim Guidance on the Preparation of Demonstrations in
Support of Requests to Exclude Ambient Air Quality Data Affected by
High Winds Under the Exceptional Events Rule. U.S. EPA. May 2013.
Available at http://www2.epa.gov/sites/production/files/2015-05/documents/exceptevents_highwinds_guide_130510.pdf.
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As identified in the Interim High Winds Guidance document, dust
phenomena are experienced primarily in the western U.S. where rainfall
is seasonal, creating dry and dusty landscapes.\111\ In high wind dust
events, the meteorological phenomenon (i.e., wind) is purely natural,
but the pollution from the event may be a mixture of natural sources
(e.g., undisturbed soil) and anthropogenic sources (e.g., soil
disturbed by human activity, emissions from sand and gravel facilities,
etc.). The EPA generally classifies high wind dust events as ``natural
events'' in cases where windblown dust is entirely from natural sources
or where all significant anthropogenic sources of windblown dust have
been reasonably controlled.\112\ This long-standing policy was first
established in the PM10 Natural Events Policy, which
provided that:
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\111\ We use ``Western U.S.'' to refer to states in the Great
Plains (North Dakota, South Dakota, Nebraska, Kansas, Oklahoma and
Texas) and those farther west including Arizona, California,
Colorado, Nevada, New Mexico, Utah, and Wyoming.
\112\ As identified in section V.D of this proposal, the EPA
will generally consider human activity to have played little or no
direct role in causing emissions of the dust generated by high wind
for purposes of the regulatory definition of ``natural event'' if
contributing anthropogenic sources of the dust are reasonably
controlled, regardless of the amount of dust coming from these
reasonably controlled anthropogenic sources, and thus the event
could be considered a natural event. In such cases, the EPA believes
that it would generally be a reasonable interpretation to find that
the anthropogenic source had ``little'' direct causal role. If
anthropogenic sources of windblown dust that are reasonably
controllable but that did not have those reasonable controls applied
at the time of the high wind event have contributed significantly to
a measured concentration, the event would not be considered a
natural event.
Ambient PM-10 concentrations due to dust raised by unusually
high winds will be treated as due to uncontrollable natural events
under the following conditions: (1) The dust originated from
nonanthropogenic sources, or (2) the dust originated from
anthropogenic sources controlled with best available control
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measures (BACM).\113\
\113\ Areas Affected by PM-10 Natural Events (the
PM10 Natural Events Policy), memorandum from Mary D.
Nichols, Assistant Administrator for Air and Radiation, to EPA
Regional Offices, May 30, 1996.
Also integral to definition of a high wind dust event is that the
wind speed be ``high,'' or, as indicated in the PM10 Natural
Events Policy, ``unusually high.'' Only ``high wind'' dust events are
exceptional events and ``high'' is area-specific.
Typically, undisturbed desert landscapes in the western U.S. have a
natural crust that protects the surface and tends to limit emissions of
windblown dust. The wind speed capable of causing emissions from these
natural undisturbed areas varies by location, depending on
characteristics of the local landscape (e.g., soil type and
characteristics, vegetation). Numerous studies have been conducted to
determine the minimum wind speed capable of causing emissions from
natural undisturbed areas and/or overwhelming reasonable controls on
anthropogenic sources.\114\ In the Interim High Winds Guidance, the EPA
called the minimum threshold wind speed capable of causing emissions
from natural undisturbed areas or overwhelming reasonable controls on
anthropogenic sources the ``high wind threshold.''
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\114\ See Appendix A1 of the Interim Guidance on the Preparation
of Demonstrations in Support of Requests to Exclude Ambient Air
Quality Data Affected by High Winds Under the Exceptional Events
Rule. U.S. EPA. May 2013. Available at http://www2.epa.gov/sites/production/files/2015-05/documents/exceptevents_highwinds_guide_130510.pdf.
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In the Interim High Winds Guidance, the EPA articulated its
expectations regarding the development and application of high wind
thresholds. In this guidance, the EPA encouraged air agencies to
identify an appropriate high wind threshold for each area experiencing
high wind dust events within their exceptional events submissions for
high wind dust events.\115\ The guidance recommended that these
thresholds should consider local conditions and specify a minimum wind
speed capable of causing emissions from those natural undisturbed areas
or overwhelming reasonable controls on contributing anthropogenic
sources (see section V.E.2 for additional discussion regarding
reasonable controls). This approach was consistent with the
PM10 Natural Events Policy in which the EPA recommended that
air agencies define the conditions in which BACM level controls were
overwhelmed. The area-specific high wind threshold should be
representative of conditions (i.e., sustained wind speeds \116\) that
are capable of overwhelming reasonable controls (whether RACM, BACM or
other) on anthropogenic sources and/or causing emissions from natural
undisturbed areas. The threshold was not intended to represent the
minimum wind speed at which any level of emissions could occur (e.g.,
aerodynamic entrainment), but rather when significant emissions begin
due to reasonable controls or natural undisturbed areas becoming
overwhelmed. We have stated that if an agency is unable to develop an
area-specific high wind threshold, we generally will accept a threshold
of a sustained wind of 25 mph for areas in the western U.S. provided
the agencies support this as the level at which they expect stable
surfaces (i.e., controlled anthropogenic and undisturbed natural
surfaces) to be overwhelmed.\117\ We did not indicate what form such
support could take. We also have said that if we receive specific
information based on relevant studies to choose an alternative high
wind threshold for an identified area, we will notify the affected air
agency.
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\115\ See Appendices A2 and A3 in the Interim Guidance on the
Preparation of Demonstrations in Support of Requests to Exclude
Ambient Air Quality Data Affected by High Winds Under the
Exceptional Events Rule. U.S. EPA. May 2013. Available at http://www2.epa.gov/sites/production/files/2015-05/documents/exceptevents_highwinds_guide_130510.pdf for additional information
on the development of a high wind threshold.
\116\ Section 6.3.2.2 in the Interim Guidance on the Preparation
of Demonstrations in Support of Requests to Exclude Ambient Air
Quality Data Affected by High Winds Under the Exceptional Events
Rule. U.S. EPA. May 2013. Available at http://www2.epa.gov/sites/production/files/2015-05/documents/exceptevents_highwinds_guide_130510.pdf for details on the
calculation of sustained wind speed. Generally, the EPA will accept
that high winds could be the cause of a high 24-hour average
PM10 or PM2.5 concentration if there was at
least one full hour in which the hourly average wind speed was above
the area-specific high wind threshold.
\117\ The 25 mph threshold is based on studies conducted on
natural surfaces. See additional information relevant to
establishing this threshold in Appendix A1 in the Interim Guidance
on the Preparation of Demonstrations in Support of Requests to
Exclude Ambient Air Quality Data Affected by High Winds Under the
Exceptional Events Rule. U.S. EPA. May 2013. Available at http://www2.epa.gov/sites/production/files/2015-05/documents/exceptevents_highwinds_guide_130510.pdf.
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Also as noted in the Interim High Winds Guidance document, the EPA
has expected air agencies to provide relevant wind data (e.g., wind
speed and direction) as part of an exceptional events submission for
high wind dust events. Wind speed data consist of analyses and
statistics showing how the observed high wind dust event wind speed
compares to the distribution of historical wind speeds and the
established high wind threshold. The EPA has recommended that air
agencies show these historical comparisons on an annual and/or seasonal
basis, depending on which is more appropriate, using a format similar
to the recommended format of the comparison to historical
concentrations showing as part of the clear causal relationship
criterion discussed in section V.E.3 of this proposal. The EPA has
encouraged air agencies to discuss wind direction in the narrative and
to present wind direction information graphically in
[[Page 72878]]
maps/plots in the clear causal relationship section of the high wind
dust exceptional events demonstration.
In considering past high wind dust event demonstrations, the EPA
has found that the ``not reasonably controllable or preventable'' and
the ``clear causal relationship'' (to include the comparison to
historical concentrations showing) criteria play significant roles in
the supporting exceptional events documentation. The EPA has generally
found that for high wind dust events, air agencies can meet the ``human
activity or natural event'' criterion by satisfying the requirements
for not reasonably controllable or preventable and clear causal
relationship as well as addressing the additional components of
exceptional events demonstration packages as discussed in section V.G.
As is the case with all demonstration packages, air agencies with
agricultural sources that potentially contribute to high wind event-
related emissions should address the question of source contribution
and associated reasonable controls on these sources within the not
reasonably controllable or preventable portion of the demonstration.
The EPA has noted in previous guidance that when considering the
anthropogenic sources that contribute to event-related emissions and
the appropriate ``reasonable controls'' on these sources, air agencies
should be aware of USDA/NRCS-approved Best Management Practices (BMPs)
(also referred to as conservation management practices) that are
designed to effectively reduce fugitive dust air emissions and prevent
soil loss in agricultural applications.\118\ We have stated that these
BMPs could be included in the collection of controls determined to
constitute reasonable controls for wind-blown dust events in areas in
which they have been implemented.
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\118\ Reference Guide for Cropping Systems and General Land
Management. USDA, NRCS and U.S. EPA. October 2012. Available at
http://www.nrcs.usda.gov/Internet/FSE_DOCUMENTS/stelprdb1049502.pdf.
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b. Proposed Changes
The EPA proposes to include in the preamble to the final rule for
this action a modified version of some of the language that first
appeared in the Interim High Winds Guidance document and to incorporate
into the rule text the revisions proposed in this section. We also
intend to revise the Interim High Winds Guidance to be consistent
following promulgation of final Exceptional Events Rule revisions.
Definition of an Event. Consistent with the EPA's proposal to
revise the regulatory definition of an exceptional event to include
both the event and its associated resulting emissions, the EPA proposes
to define a high wind dust event as an event that includes the high-
speed wind and the dust that the wind entrains and transports to a
monitoring site. Consistent with the nullified language in the 2007
Exceptional Events Rule preamble, the PM10 Natural Events
Policy and the Interim High Winds Guidance, the EPA proposes to define
high wind dust events in the rule text as ``natural events'' in cases
where windblown dust is entirely from natural sources or where all
significant anthropogenic sources of windblown dust have been
reasonably controlled.
High Wind Threshold. To facilitate clearer expectations regarding
the evidence needed to demonstrate which controls constitute
``reasonable controls,'' the EPA proposes to codify in rule language
the definition of ``high wind threshold'' as the minimum threshold wind
speed capable of causing particulate matter emissions from natural
undisturbed lands in the area affected by a high wind dust event. The
EPA proposes to accept a threshold of a sustained wind of 25 mph for
areas in the western U.S. provided this value is not contradicted by
evidence in the record when we review a demonstration. If the EPA
receives specific information based on relevant studies that suggest a
different high wind threshold for an identified area, the EPA will
notify the affected air agency so that the agency may consider basing
its demonstration on that threshold value. The EPA would consider such
information as part of the weight of evidence analysis for a submitted
demonstration. In lieu of using the default 25 mph high wind threshold,
air agencies would have the option to identify an area-specific high
wind threshold that is more representative of local/regional
conditions.
The high wind threshold concept will continue to apply to the
review of demonstrations for events in a nonattainment or maintenance
area for which the dust controls in a recently approved SIP are
generally accepted as sufficient to satisfy the not reasonably
controllable criterion. For such a demonstration, the controls
specified in the SIP should be considered reasonable, while
acknowledging the possibility that the controls are not being complied
with and that uncontrolled anthropogenic sources of PM could be the
contributing to the exceedance. For events with sustained wind speeds
above the high wind threshold, it is very plausible that SIP controls
were being implemented and the high PM concentrations are due to
emissions generated from sources in the area despite implementation of
the SIP measures. Conversely, for events with sustained wind speeds
below the high wind threshold, it becomes more plausible that there may
be noncompliance with control measures or that uncontrolled
anthropogenic sources are contributing to the exceedance. Therefore,
the comparison of sustained wind speeds during an event to the high
wind threshold will help the EPA Regional offices determine what
evidence is required to be included in a demonstration regarding
reasonable controls, the possibility of non-compliance, or non-event
sources.
Large-Scale or High-Energy High Wind Dust Events. The EPA proposes
to codify in rule language to apply a case-specific approach when
considering reasonableness of controls for remote, large-scale, high-
energy and/or sudden high wind dust events, such as ``haboobs'' in the
southwest where sustained wind speeds can exceed 40 mph and generate
walls of dust several miles wide and more than a mile high. The
proposed rule text provides that in these situations, the event will be
considered not reasonably preventable or controllable. Therefore, a
demonstration limited to such event(s) will not need to substantively
address this criteria. The EPA solicits comment on this proposed, case-
specific approach when considering reasonableness of controls for
remote, large-scale, high-energy and/or sudden high wind dust events.
Other Types of High Wind Dust Events. Any demonstration for a non-
high-energy event would be evaluated on a case-by-case basis. In doing
so, the EPA would consider what controls are reasonable in light of an
area's attainment status and associated CAA control requirements, the
frequency, and range of non-high energy wind events known (at the time
of the particular event that is the subject of the demonstration) to
occur in the area.
The Role of the EPA-approved SIP in Nonattainment and Maintenance
Areas. As stated in section V.E.2, the EPA proposes to establish by
rule a non-rebuttable presumption that, during a 5-year window (or,
alternatively another appropriate timeframe) following approval of an
attainment plan or maintenance plan SIP during which no subsequent new
obligation for the air agency to revise the SIP has arisen, the control
measures included in the SIP that are specific to the relevant
pollutant, sources and event type satisfy the not reasonably
controllable or
[[Page 72879]]
preventable criterion.\119\ Otherwise, the air agency and the EPA would
evaluate the not reasonably controllable or preventable criterion on a
case-by-case basis.
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\119\ A request for data exclusion must also show that the event
was not a result of noncompliance with any existing state or local
laws or rules that have not been incorporated into the SIP.
---------------------------------------------------------------------------
We describe below one potential scenario in which deference to the
SIP for purposes of ``reasonable controls'' (versus a case-by-case
analysis) satisfies the not reasonably controllable or preventable
criterion. We also provide two other scenarios needing a case-by-case
analysis for purposes of satisfying the not reasonably controllable or
preventable criterion. We identify these scenarios below and then
discuss them in more detail in sequence.
Nonattainment Area Scenario 1--The EPA approved the SIP
with the enforceable control measures as meeting attainment or
maintenance planning requirements within 5 years of the date of
submittal of the event AND the air agency is not under an obligation to
revise the SIP for the reason listed in Scenario 2 or any other reason.
Additionally, the sustained winds during the event are above the high
wind threshold. The SIP includes enforceable control measures that
address the event-related pollutant and all sources necessary to
fulfill the requirements of the CAA for the SIP that have or may have
contributed to event-related emissions. This indicates that in the
development and approval of the SIP, both the EPA and the state
considered what event-related controls were sufficient to meet the
attainment or maintenance plan requirements of the CAA.
Nonattainment Area Scenario 2--The air agency is under an
obligation to revise the SIP as a result of a SIP call based on failing
to provide for attainment and maintenance of the relevant NAAQS as
evidenced by current violations.\120\
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\120\ Other possible reasons for an area to be in a Scenario 2
situation would be if it has been designated nonattainment for a
revised NAAQS for the relevant pollutant or is subject to a SIP call
for the relevant pollutant following the EPA's determination that
the SIP is inadequate for some other reason.
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Maintenance Area Scenario 3--The EPA approved the SIP more
than 5 years prior to the date of submittal of a demonstration.
Details for Nonattainment Area Scenario 1
In this scenario, where the sustained winds during the event are
above the high wind threshold, the EPA would apply a non-rebuttable
presumption that the controls in the existing SIP represent reasonable
measures to prevent or control any event of the given type that occurs
in the 5-year window. To satisfy the not reasonably controllable or
preventable criterion, the EPA would expect the submitting air agency
to identify the emission sources that contribute to the event emissions
and exceedance and identify the associated SIP controls plus any other
enforceable control measures required by state laws or rules. The air
agency would also identify the implementation status of these controls
and provide evidence of effective implementation and enforcement.
Example: An air agency submits a demonstration for a high wind dust
event in a PM10 nonattainment area that occurred in October
2015. The air agency has an EPA-approved attainment plan SIP for the
affected area that was approved in October 2010 and that SIP includes
enforceable controls implemented in accordance with the SIP that
address the event-related pollutant (i.e., PM) and all sources
necessary to fulfill the requirements of the CAA. The sustained winds
during the event were above the high wind threshold. In the not
reasonably controllable or preventable portion of its high wind dust
demonstration, the air agency would describe the event-related wind
characteristics and identify the natural and anthropogenic emission
sources that contributed to the event emissions and the associated SIP
and other control measures. The air agency would then describe the
implementation status of these controls and provide evidence of
effective implementation and enforcement. The air agency would conclude
the ``not reasonable controllable or preventable'' portion of the
demonstration by affirmatively stating that because the EPA had
approved the SIP within 5 years of the event and because the SIP
measures and other measures specific to the pollutant and at least some
anthropogenic emission sources that contributed to the event emissions
were implemented, the agency has satisfied the not reasonably
controllable or preventable criterion.
In reviewing the demonstration in this scenario, the EPA would
generally concur that the air agency met the not reasonably
controllable or preventable criterion during the 5-year period provided
the SIP was implemented and the event was not attributable to
noncompliance. Thus, assuming the demonstration also satisfied the
remaining technical and procedural elements in the Exceptional Events
Rule, the EPA would concur with the air agency's request to exclude
data for purposes of regulatory actions within the scope of the final
revised Exceptional Events Rule. If, however, the air agency
experienced an exceedance or violation during the 5-year period for
reasons other than those attributable to the successful exceptional
events demonstration (e.g., industrial source noncompliance or another
type of event), the EPA may take one of these actions. In addition, the
EPA may issue a SIP call because the SIP is inadequate with regard to a
requirement of the CAA that is not tied to the occurrence of NAAQS
violations related to exceptional events. If the EPA issues a SIP call
during the 5-year window, the situation would switch to Scenario 2.
Details for Nonattainment Area Scenario 2
In this scenario (where the SIP is being revised to respond to a
SIP call involving the PM10 or PM2.5 NAAQS), the
existing SIP controls should not be presumed to satisfy the not
reasonably controllable or preventable criterion regardless of whether
the event-related wind speeds are above or below the high wind
threshold. The EPA recommends that as the first step in preparing an
exceptional events demonstration, the air agency should assess the
case-specific effectiveness of the controls that were in place at the
time of the event and consider potential controls that are more
comprehensive and effective than those in the SIP that the agency could
have implemented before or during the event. This case-specific
assessment should apply the concept that if a set of control measures
should reasonably have been in place for emission sources that
contribute to the event emissions in light of the information in the
record of the EPA action that has created the obligation to revise the
SIP, then those controls must have been in place for the event to
satisfy the not reasonably controllable or preventable criterion.
The submitting air agency preparing a case-specific assessment
should first identify the natural and anthropogenic emission sources
that significantly contribute to the event emissions and exceedance.
The air agency should categorize sources as those that are addressed
through SIP or other state or local laws or rules and those sources
that are not addressed by SIP measures or other measures. Where the
contributing source has SIP or other controls, the air agency would
identify the implementation status of these controls and provide
evidence of effective implementation and
[[Page 72880]]
enforcement. The air agency should also consider whether those SIP
controls should have been made more stringent and effective prior to
the event. For emission sources that contribute to the event emissions
but are not specifically addressed in the SIP or other laws or rules,
the air agency should identify and document why it was reasonable to
have not implemented controls.
We invite comment on whether there should be a grace or
grandfathering period before a SIP call involving a relevant NAAQS has
the effect of ending the deference that applied prior to the SIP call,
such that for an event occurring during the grace period the SIP would
be given the deference described for the first scenario. We believe
that such a grace period should not extend beyond the due date for the
required SIP revision in response to the SIP call.
Example: An air agency has an EPA-approved attainment plan SIP for
a PM10 nonattainment area that was approved in 1994 and
includes controls for some of the anthropogenic emission sources that
contribute fugitive dust during high wind events. The nonattainment
area did not include fugitive dust controls for gravel operations in
its 1994 SIP and has not required any controls of these operations in
the years since SIP approval. The area does not have an approved
maintenance plan, in part because it has been experiencing unresolved
exceedances since 1994. The air agency alerts the reviewing EPA
Regional office that it wishes to submit an exceptional events
demonstration for a high wind dust event that occurred in 2015 and
affected several of the area's monitoring sites. This is the second
high wind dust event associated with an exceedance in the past 3 years.
After the first event, the EPA issued a SIP call for the air agency to
revise its PM10 SIP, but the air agency has not yet
submitted a new SIP. Because the EPA issued a SIP call, the air agency
is required to show on a case-specific basis that the not reasonably
controllable or presentable criterion has been met. Applying the
concept that if a set of control measures should reasonably have been
in place for emission sources that contribute to the event emissions to
the information in the record supporting the SIP call would likely
result in a determination that those controls must have been in place
for the event to satisfy the not reasonably controllable or preventable
criterion. Because the gravel operations are not controlled and because
the high wind dust event was the second in 3 years, the air agency had
a basis for understanding the possible need for better controls. Given
the air agency's knowledge of recurring events, the air agency may not
be able to make a sufficient showing for the not reasonably
controllable or preventable criterion and the reviewing EPA Regional
office may not be able to concur with the air agency's request to
exclude data. If, however, the air agency can show that the gravel
operations did not contribute to the event-related emissions, the
reviewing EPA Regional office might be able to concur with the air
agency's request to exclude data.
Details for Maintenance Area Scenario 3
In this scenario (where the SIP was approved more than 5 years
prior to the date of submittal of a demonstration and the air agency is
not under an obligation to revise the SIP), because of the passage of
time the SIP controls should not be presumed to satisfy the not
reasonably controllable or preventable criterion regardless of whether
the event-related wind speeds are above or below the high wind
threshold. In this case, the air agency should complete a case-specific
assessment of the reasonableness of controls to satisfy the not
reasonably controllable or preventable criterion. The assessment should
consider controls beyond those required by the existing SIP and other
state or local laws and rules. The case-specific assessment should
apply the concept that if a set of control measures should reasonably
have been in place for emission sources that contribute to the event
emissions, then those controls must have been in place for the event to
satisfy the not reasonably controllable or preventable criterion. The
submitting air agency should first identify the natural and
anthropogenic emission sources that contribute to the event emissions
and exceedance. The air agency should categorize sources as those that
are addressed through SIP or other state or local laws or rules and
those sources that are not addressed by SIP measures or other measures.
Where the contributing source has SIP or other controls, the air agency
would identify the implementation status of these controls and provide
evidence of effective implementation and enforcement. The air agency
should also consider whether those SIP controls should have been made
more stringent and effective prior to the event. For emission sources
that contribute to the event emissions but are not specifically
addressed in the SIP or other laws or rules, the air agency should
identify and document why it was reasonable to have not implemented
controls.
Example: An air agency has an EPA-approved attainment plan SIP for
a PM10 former nonattainment area that was approved in 2008
and includes controls for anthropogenic emission sources that
contribute fugitive dust during high wind events. The area has an
approved maintenance plan. Between 2008 and 2014 it has not been
experiencing exceedances related to high winds. In 2014 there is a
single high wind dust event with sustained wind speeds above the high
wind threshold that results in two exceedance days, sufficient to
constitute a 3-year NAAQS violation. The air agency submits a
demonstration covering both exceedances. In the not reasonably
controllable or preventable portion of its demonstration, the air
agency would identify all sources contributing to the event emissions,
including natural sources, sources identified and controlled in the
SIP, and any sources not controlled by the SIP. The air agency would
then identify the applicable controls, the implementation status of
these controls and evidence of enforcement. The air agency should also
consider whether those SIP controls should have been made more
stringent and effective prior to the event. Given the area's past
history of not having events and the fact that the sustained wind speed
during the event was above the high wind threshold, it is likely that
the air agency could make a sufficient showing for the not reasonably
controllable or preventable criterion. In this case, provided the air
agency satisfies the other rule criteria, the EPA Regional office would
likely concur with an air agency's request for data exclusion.
However, in this maintenance area scenario, another possible
outcome of an event that causes an exceedance or violation is that the
EPA determines that the not reasonably controllable or preventable
criterion is not met and the event-affected data are retained for
regulatory actions within the scope of the Exceptional Events Rule.
This may lead to the EPA taking an action that places the air agency
under an obligation to revise the SIP, in which case the situation
would change into the second scenario for any later events of the same
type.
Best Management Practices. The EPA solicits comment on whether or
not, as part of the assessment of local sources and reasonable
controls, USDA/NRCS-approved BMPs constitute sufficient reasonable
controls in any or in all high wind event-affected areas and whether
these measures should therefore be specifically and categorically
identified in preamble or rule language as constituting reasonable
controls. As discussed in the ``Current Situation'' section, the EPA
has noted in previous guidance that USDA/NRCS-approved BMPs designed to
effectively reduce
[[Page 72881]]
fugitive dust air emissions and prevent soil loss in agricultural
applications could be included in the collection of controls determined
to constitute reasonable controls for wind-blown dust events in areas
in which they have been implemented.\121\ Although the EPA has
addressed the sufficiency of BMPs in decisions on individual
exceptional events demonstrations when the BMPs were part of a SIP-
approved BACM determination, we have not previously addressed whether
or not BMPs individually or in some combination with each other
constitute sufficient reasonable controls nationally or in any
particular types of areas. We recognize that this question may be
difficult to answer because BMPs often describe general types of
practices (e.g., installing wind breaks) rather than specifying the
penetration, scale or intensity of use of these practices by the
landowners who adopt them. Therefore we also solicit comment on the
evidence for degree of penetration, scale and intensity that would be
appropriate in demonstrations to consider BMPs individually or in some
combination with each other to be reasonable controls.
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\121\ Interim Guidance on the Preparation of Demonstrations in
Support of Requests to Exclude Ambient Air Quality Data Affected by
High Winds Under the Exceptional Events Rule. U.S. EPA. May 2013.
Available at http://www2.epa.gov/sites/production/files/2015-05/documents/exceptevents_highwinds_guide_130510.pdf and Interim
Guidance to Implement Requirements for the Treatment of Air Quality
Monitoring Data Influenced by Exceptional Events. U.S. EPA. May
2013. Available at http://www2.epa.gov/sites/production/files/2015-05/documents/exceptevents_guidememo_130510.pdf.
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G. Other Aspects of Flagging Exceptional Events-Influenced Data and
Demonstration Submittal and Review
1. Who may submit a demonstration and request for data exclusion?
a. Current Situation
Before addressing the schedule and mechanics of flagging event-
influenced data and preparing demonstrations, the EPA believes it is
necessary to first clarify which parties can submit an exceptional
events demonstration package to the EPA. The CAA language at section
319(b)(3)(B)(i) states that ``the occurrence of an exceptional event
must be demonstrated by reliable, accurate data that is promptly
produced and provided by Federal, State, or local government
agencies.'' As noted in section V.A of this proposal, state, local and
some tribal agencies administer air quality management programs within
their jurisdiction, which includes monitoring and analyzing ambient air
quality and submitting monitoring data to the EPA, which are then
stored in the EPA's AQS database. Also, FLMs and other federal agencies
operate air quality monitoring stations on some lands they manage, and
some of these monitors meet the technical specifications and quality
assurance requirements for their data to be used in regulatory
determinations. As operators of regulatory monitors, each of these
agencies can flag their own data within AQS for consideration as an
exceptional event.
As discussed in section V.F.1 of this proposed action, however, the
EPA generally considers a state, exclusive of tribal lands, to be a
single responsible actor, and, as the state is the entity primarily
responsible for administering air quality planning and management
activities, the state has been ultimately responsible for submitting
exceptional events demonstrations for exceedances that occur at all
regulatory monitoring sites within the boundary of the state, including
exceedances occurring at monitoring sites operated by local air quality
agencies to whom a state has delegated relevant responsibilities or at
regulatory monitoring sites operated by any other entity within the
state, such as FLMs of Class I areas, other federal agencies and/or
industrial facilities. Although the state is responsible, a local
agency, an FLM, another federal agency or another entity operating a
regulatory monitor with an event-influenced exceedance can develop a
demonstration for submittal by the state. If a state disagrees with the
local agency's, FLM's, other federal agency's or other entity's
exceptional events claim, the state can decide not to act on or forward
that submittal to the EPA. A state can request that operators of other
regulatory monitors experiencing event-influenced exceedances prepare
or assist in the preparation of demonstration analyses for ultimate
submittal by the state.
Because some tribal air quality agencies also operate regulatory
ambient air quality monitoring sites and submit these data to the EPA's
AQS database, as appropriate, these tribal agencies may also submit
exceptional events demonstrations for exceedances that occur at their
monitoring sites.
b. Proposed Changes
As indicated in section V.A of this proposal, because FLMs and
other federal agencies may operate regulatory monitors and submit
collected data to the EPA's AQS database and these same monitors could
be affected by emissions from exceptional events, the EPA proposes to
allow FLMs and other federal agencies to prepare and submit exceptional
events demonstrations and data exclusion requests directly to the EPA.
The EPA solicits comment on this proposed addition to the rule text,
which appears at the end of this document. Based on comments received,
the EPA may retain, modify or not include this provision in the final
promulgated rule. This provision would apply only to FLMs and other
federal agencies that manage land on which an exceptional event
originates or that operate a monitor that has been affected by an
event. The provision would allow such FLMs and other federal agencies
to provide demonstrations directly to the EPA only after a discussion
with the state in which the monitor is operated. This discussion might
instead result in an agreement that the federal agency (or another
party) will provide a draft demonstration document to the appropriate
state air agency for adoption and submission by the state air agency to
the EPA, as is currently allowed. Regardless of who ultimately submits
the demonstration, the EPA encourages collaboration between the FLMs
and other federal agencies and the appropriate state air agency during
the event identification and demonstration development process. If the
provision for direct submission to the EPA is included in the final
action, demonstrations prepared by FLMs or other federal agencies would
be required to meet all provisions in the Exceptional Events Rule,
including the requirement for a public comment period on a prepared
demonstration \122\ and the requirements related to schedules and
procedures for demonstration package submittal (see sections V.G.4,
V.G.5 and V.G.6) that apply to state agencies that operate monitors.
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\122\ A public comment opportunity is important prior to
submission to the EPA because under the Exceptional Events Rule the
EPA is not required to provide a public comment opportunity prior to
concurring with an air agency's request to exclude data. The EPA
generally provides a public comment opportunity before we use air
quality data, with or without such exclusions, in a final regulatory
action. States typically provide an opportunity for public comment
by posting draft demonstrations on a Web site. Federal agencies
could do the same.
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2. Aggregation of Events for NAAQS With Periods Longer Than 24 Hours
and Demonstrations With Respect to Multiple NAAQS for the Same
Pollutant
a. Current Situation
The EPA's AQS database houses ambient air quality monitoring and
related data. The data in AQS are maintained as individual reported
measurements, which can range from 5-minute maximum concentrations per
hour for SO2, to hourly data for ozone,
[[Page 72882]]
CO, NO2, SO2 and some PM measurements to 24-hour
measurements for lead and other particulate matter measurements. Air
agencies identify and the EPA concurs with exceptional event-related
data in AQS that are reported as individual measurements.
Some NAAQS have long averaging periods, such that multiple
independent events may affect the period-average concentration of the
NAAQS pollutant. In the aggregate, a clear causal relationship may
exist between the events and an exceedance or violation, but no single
event satisfies the clear causal relationship criterion because each
event has too small of an effect on the longer-period metric to do so
by itself. CAA section 319(b) and the 2007 Exceptional Events Rule do
not clearly allow the aggregation of events for purposes of the clear
causal relationship criterion, yet aggregation seems consistent with
the intent of section 319(b). The EPA has not to date indicated that
actual aggregation of events is permitted. However, Question 30 in the
Interim Q&A document provided guidance that can be of some help in this
situation. This guidance was that 24-hour concentrations of Pb,
NO2, or SO2 can be individually compared to the
NAAQS level defined for a longer period, for purposes of meeting ``but
for'' with respect to both the 24-hour NAAQS, if applicable, and for
purposes of meeting ``but for'' with respect to the NAAQS with the
longer averaging period. This guidance focused on the intention of a
passage in the preamble to the 2007 Exceptional Events Rule addressing
the PM2.5 NAAQS in particular, and extended the approach of
the 2007 preamble to other cases of NAAQS for the same pollutant that
have different averaging periods. The practical effect of this approach
is that several events that individually have effects too small to have
a causal connection to a longer-period exceedance or violation might be
excluded one-by-one, and the net effect of the exclusions may make a
difference to compliance with the longer-period NAAQS. As guidance,
however, the Interim Q&A document does not provide full certainty that
an air agency may rely on the recommended approach.
As noted in section IV.B of this proposal, the 2007 Exceptional
Events Rule requires that for data exclusion, among other requirements,
an air agency must demonstrate that there would have been no exceedance
or violation of the NAAQS ``but for'' the event. The ``but for''
criterion necessarily requires comparing the individual measurements in
AQS to the averaging period of the relevant NAAQS to determine whether
an exceedance or violation occurred. When the averaging period for the
NAAQS is the same as the measurement duration period, this comparison
is relatively straightforward. For example, air agencies and the EPA
can directly compare 1-hour ozone, 1-hour CO, 1-hour SO2,
and 1-hour NO2 measurements to the respective 1-hour NAAQS.
This comparison becomes more complicated, however, when there is a
difference between the pollutant measurement duration and the averaging
time of the NAAQS, which is the case when comparing a 1-hour
measurement to an 8-hour, 24-hour, 3-month or annual NAAQS (or in the
case of 1-hour ozone the previously existing NAAQS). In fact, the EPA
devoted Questions 29-31 in the Interim Q&A document to explaining how
to make these complicated comparisons.\123\ The Interim Q&A document
also explained that because these comparisons are NAAQS-specific, air
agencies should request and support the exclusion of a measured air
concentration separately for each NAAQS that applies to the pollutant
and the EPA will similarly provide separate concurrences. Under the
2007 Exceptional Events Rule provisions, this means, for example, that
an air agency with several 24-hour measurements of event-influenced
PM2.5 data measuring 75 micrograms per cubic meter ([mu]g/
m\3\) would need to separately flag the data within AQS on a NAAQS-
specific basis, and submit separate requests, analyses and
demonstration components to support exclusion of the identified event-
influenced data for the 1997 annual secondary PM2.5 NAAQS of
15 [mu]g/m\3\, the 2012 annual primary PM2.5 NAAQS of 12
[mu]g/m\3\ and the 2006 primary and secondary 24-hour PM2.5
NAAQS of 35 [mu]g/m\3\. Depending on the outcome of the ``but for''
criterion with respect to each PM2.5 NAAQS, it could be that
the data would be excluded for purposes of determinations with respect
to only some of these NAAQS.
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\123\ Interim Exceptional Events Rule Frequently Asked
Questions. U.S. EPA. May 2013. Available at http://www2.epa.gov/sites/production/files/2015-05/documents/eer_qa_doc_5-10-13_r3.pdf.
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This current situation can result in complicated demonstrations for
air agencies seeking data exclusion from determinations with respect to
multiple NAAQS for the same pollutant. This complexity may make it more
difficult for the public to comment, and requires time for the EPA to
review such a demonstration.
b. Proposed Changes
The EPA is taking comment on proposed rule text allowing 24-hour
concentrations of any NAAQS pollutant to be compared to a NAAQS level
defined for a longer period as part of a weight of evidence showing for
the clear causal relationship with respect to the NAAQS with the longer
period. This approach would be more amenable to less quantified weight
of evidence demonstrations, since only one day would be examined at a
time.
The EPA is also proposing that for NAAQS with averaging or
cumulative periods longer than 24 hours, events occurring on different
days may be aggregated for the purpose of determining whether their
collective effect has caused an exceedance or violation, without regard
to whether the events are of the same type (e.g., stratospheric ozone
intrusion followed by a wildfire). The EPA notes that such aggregation
may be very difficult if the effects of the individual events on their
individual days are not fully quantified. Proposed rule text for this
change is provided for comment.
Finally, to simplify some demonstrations, the EPA is also taking
comment on whether a successful demonstration with respect to any NAAQS
for a given pollutant would suffice to qualify the data in question for
exclusion with respect to all NAAQS for that pollutant. The EPA
believes it is useful to invite public comment on this ``approved for
one NAAQS approved for all NAAQS for the same pollutant'' concept.
The EPA will carefully consider the comments it receives on these
concepts and may finalize all, some or none of the three proposals
described in this section.
3. Exclusion of Entire 24-Hour Value Versus Partial Adjustment of the
24-Hour Value for Particulate Matter
a. Current Situation
As indicated in Question 29 of the Interim Q&A document, we have
advised air agencies preparing demonstrations to support requests to
exclude PM2.5 and PM10 data obtained via monitor
instruments that provide 1-hour measurements that they should flag all
24 1-hour values within a given event-affected day, even if the event
did not last all these hours. If concurred upon, flagging all 1-hour
values will ultimately result in the same available remaining data for
regulatory analysis and calculation as would be the case had the 24-
hour PM2.5 or PM10 measurement data been
collected from filter-based (24-hour) monitoring
[[Page 72883]]
instruments.\124\ Another reason we have taken the position that
flagging all 24 1-hour values is appropriate is because flagging only
peak or selected hours could result in the remaining 1-hour values
still meeting the data completeness requirements because flagged and
excluded data do not count against completeness even though they cannot
be used in calculating an average concentration for a 24-hour period.
Under the rules for data interpretation, exclusion of only the event-
affected 1-hour concentrations could result in AQS calculating a
seemingly valid 24-hour concentration that is actually highly uncertain
because it is based on only a few hours and thus may be biased.\125\
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\124\ Filter based instruments typically record a single value
within a 24-hour period while continuous monitors typically collect
24 1-hour measurements. Because AQS can calculate a valid 24-hour
average concentration with as few as 18 hours, it may be necessary
to exclude hours not actually affected by the event to ensure the
same data exclusion outcome as if the measurement had been made with
a 24-hour filter.
\125\ The form of the 24-hour PM2.5 NAAQS of 35
[mu]g/m\3\ is 98th percentile averaged over 3 years. The form of the
primary annual PM2.5 NAAQS of 12 [mu]g/m\3\ is an annual
mean averaged over 3 years. The form of the 24-hour PM10
NAAQS of 150 [mu]g/m\3\ is not to be exceeded more than once per
year on average over 3 years. Biased concentrations can potentially
skew the determination of the 98th percentile and/or the annual mean
for PM2.5 and the averages for PM2.5 or
PM10 calculated to determine compliance with the relevant
NAAQS.
---------------------------------------------------------------------------
b. Proposed Changes
The EPA solicits comment on codifying its current approach in the
rule text to eliminate any regulatory uncertainty. If finalized, this
modification to the data handling procedures will be made to occur
automatically within AQS.
4. Flagging of Data
While neither the preamble to nor the rule text contained within
the 2007 Exceptional Events Rule discuss data handling within AQS,
explaining certain AQS processes and functions will be useful to an
understanding of the data flagging situation that has developed in
implementing the requirements in 40 CFR 50.14(c)(2) and why we are
proposing changes.
a. Current Situation
Within AQS, monitoring agencies can use two types of data
validation, or data qualifier, codes related to exceptional events: The
Request Exclusion flags (R) and the Informational Only flags (I).\126\
The EPA has advised air agencies to use the I series flags when
identifying informational data and the R series flags to identify data
points for which the agency intends to request an exceptional events
exclusion and the EPA's concurrence. As an example, air agencies may
currently use an I series flag to initially identify values they
believe were affected by an event. Once the air agency collects
additional supporting data, it may change the flag to an R series flag
and submit an initial event description. Or, the air agency may find
that additional information does not support flagging the data as an
exceptional event, and the air agency may, therefore, delete the flag
or retain the I series flag. Air agencies may also use the I series
flags simply to note activities or conditions occurring on the data
collection day that are unrelated to exceptional events or that do not
result in an exceedance or violation of a NAAQS. Air agencies have
previously indicated that they generally see little value in the use of
I series flags.\127\
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\126\ ``Flag'' is the common terminology for a data qualifier
code in the EPA's AQS. Unless explicitly noted, the process of
``flagging'' data refers to adding Request Exclusion (R) data
qualifier codes to selected data in AQS. R flags are the only AQS
flags that satisfy the 2007 Exceptional Events Rule requirement for
initial data flagging. The current design of the AQS software is
such that EPA can act/concur only on an R flag.
\127\ Responses to Significant First-Round Comments on the Draft
Guidance Documents on the Implementation of the Exceptional Events
Rule, U.S. EPA, June 2012. Available in Docket No. EPA-HQ-OAR-2011-
0887.
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Flagging of event-influenced data has traditionally also involved
associating a one- or two-character code with a monitored value within
AQS indicating that the data have potentially been influenced by a
particular type of exceptional event (e.g., ``RT'' is the character
code used to request exclusion for data that have been influenced by
wildfires in the U.S.). The 2007 Exceptional Events rule added a
requirement to include a more detailed initial description of the
particular event associated with such a character code. This
description consists of text of variable length.
The EPA does not review or concur on the I series flags. Rather, an
air agency must use an R flag to request data exclusion. The language
at 40 CFR 50.14(c)(2), Flagging of Data, requires that an air agency
notify the EPA of its intent to exclude one or more measured
exceedances of an applicable NAAQS as being due to an exceptional event
by placing a flag and an initial event description in the appropriate
fields in AQS for the data record(s) of concern no later than July 1 of
the calendar year following the year in which the flagged measurement
occurred. Only R flags fulfill this requirement. This ``general''
schedule date of July 1 applies unless the data are associated with the
initial area designations process for a new or revised NAAQS in which
case the specific schedule in Sec. 50.14(c)(2)(vi) applies.
Air agencies have previously expressed concern that the timelines
for event flagging and demonstration submittal are not always
appropriate.\128\ While the EPA has historically promulgated revised
flagging and demonstration submittal schedules in the regulatory
actions for new and revised NAAQS for those data years that might be
used in the initial area designations process for those NAAQS, the EPA
does not promulgate revised schedules for other regulatory actions such
as clean data or attainment determinations. Rather, the EPA has relied
upon the ``general'' flagging and demonstration submittal schedules in
40 CFR 50.14(c)(2) and (c)(3)(i). Meeting the requirement at 40 CFR
50.14(c)(2)(iii) to submit R flags and an initial description of the
event ``not later than July 1st of the calendar year following the year
in which the flagged measurement occurred'' can be difficult in the
case of an annual standard where an air agency needs all 12 months of
data to calculate an annual average and then needs 3 years of annual
averages to identify whether or not the event-influenced data results
in a violation of a 3-year design values. An air agency may not know
that data influenced by an exceptional event caused the design value to
become a NAAQS violation until 3 years after the event occurred.
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\128\ Responses to Significant First-Round Comments on the Draft
Guidance Documents on the Implementation of the Exceptional Events
Rule, U.S. EPA, June 2012. Available in Docket No. EPA-HQ-OAR-2011-
0887.
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Some air agencies have used and applied I and R flags in AQS
inconsistently with this intended scheme, by including applying
numerous R flags in AQS with no real intention to submit an exceptional
events demonstration. Also, R flags may be set immediately before a
demonstration is submitted or even as late as when the EPA needs to
indicate in AQS our approval of a request for data exclusion. As a
result, neither the presence nor the absence of these flags provide the
EPA with an indication of anticipated exceptional events
demonstrations.
b. Proposed Changes
As part of this action, the EPA proposes to revise the ``general''
schedule language contained within 40 CFR 50.14(c)(2) by removing the
timelines associated with initial event flagging. The EPA also proposes
to modify the associated data flagging process within AQS to correspond
with
[[Page 72884]]
these proposed regulatory changes. These proposed changes would include
eliminating the use of the current exceptional events data validation/
data qualifier codes: The Request Exclusion flags (R) and the
Informational Only flags (I). The one- or two-character event type
codes would be retained. The EPA solicits comment on the approach that
is discussed below in additional detail.
The EPA is proposing to change the definition and process for
flagging exceptional event data. Flagging would in effect become the
application of the one- or two-character event type and event
description text as described below, along with a concurrent or
subsequent request for data exclusion communicated to the EPA through
other channels.
Because the flagging of data necessarily begins with the
identification of an event, the EPA proposes to retain, with
modifications, the AQS free-form text field for an initial event
description. As is currently the practice, we request that air agencies
use the ``initial event description'' to identify a unique, real-world
event. We propose that this ``initial event description'' be expanded
to contain a unique event name; the type of the event (e.g., high wind
dust, volcanic eruption, other); a brief description of the event; and,
to the extent known, the scope of the event in terms of geography and
time (e.g., likely affected area using latitude and longitude and a
radius of influence and beginning day/time and ending day/time).\129\
AQS would also be modified to allow the air agency to associate
specific AQS sites and potentially affected monitors and specific data
points with a given event as so described. This will enable air
agencies and the EPA to ``flag'' or add qualifier codes to selected
data in a single step rather than adding this information or the
necessary codes on a per entry basis. Historically, when events have
influenced the concentrations at multiple monitors for multiple days,
the air agency has added initial event descriptions and set flags on
each monitored concentration, sometimes resulting in hundreds of
identical individual entries. ``Associating'' monitors with an event
defined in time and space will save resources.
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\129\ The EPA is proposing that air agencies select the ``type
of event'' from a pre-set list of event types, which would likely
consist of those event types currently identified by existing
Informational and Request Exclusion flags within AQS.
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Once an air agency has identified an event and created the initial
event description within AQS, the agency should begin the process of
requesting exclusion for identified data, which will consist of two
discrete operations: (1) Indicating in a separate communication to the
EPA that specific ambient air quality measurements are affected by a
defined event (see section V.G.5 related to Initial Notification of
Potential Exceptional Event), and (2) requesting that these identified
ambient air quality measurements be excluded from regulatory actions
according to the terms of the revised Exceptional Events Rule and EPA
guidance for other applications of air quality data. AQS would retain a
field to allow the EPA to concur or not concur with a given request for
exclusion for one or more of the data points associated with a
described event, once review of the air agency's request and
demonstration is completed.
In addition to the proposed AQS modifications described above, the
EPA is proposing to remove the ``general'' flagging schedule in 40 CFR
50.14(c)(2)(iii). This regulatory language currently requires that air
agencies submit [R] flags and an initial description of the event by
July 1 of the calendar year following the year in which the flagged
measurement occurred or by the other deadlines identified with
individual NAAQS. As noted earlier in this section, an air agency may
not know that data influenced by an exceptional event caused a
violation of a NAAQS until after the initial event flagging deadline
has passed. The EPA proposes to remove and reserve the current language
at 40 CFR 50.14(c)(2)(iii). Additional changes to the regulatory
language in 40 CFR 50.14(c)(2) will be discussed in the next section.
The EPA notes that the recent ozone NAAQS action \130\ also removed
and reserved the subsequent sections at 40 CFR 50.14(c)(2)(iv) and (v),
which addressed the submittal of exceptional events demonstrations that
could affect regulatory determinations associated with initial area
designations for the 2006 24-hour PM2.5 NAAQS and the 2010
Lead NAAQS and were made obsolete by the passage of time. The EPA will
retain these removed and reserved sections as promulgated in the ozone
NAAQS and proposes no additional changes to these sections.
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\130\ 80 FR 65292 (October 26, 2015).
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5. Initial Notification of Potential Exceptional Event
a. Current Situation
As the EPA acknowledged in the Interim Exceptional Events
Implementation Guidance and in discussions with stakeholders, the EPA
understands that the initial identification of data affected by
exceptional events and the subsequent preparation, submittal and review
of demonstration packages is a resource intensive process both for the
preparing air agency and the reviewing EPA Regional office.\131\ Delays
in processing and making decisions on submitted packages create
regulatory uncertainty and potentially increase the workload for both
the submitting air agency and the EPA. In addition, the backlog of
pending actions makes selection of the best information to support new
submittals potentially more uncertain. Further, air agencies and the
EPA often face timelines by which they must make regulatory decisions
that can be affected by the inclusion or exclusion of event-affected
data. In the Interim Exceptional Events Implementation Guidance and
through the EPA's best practices discussions identified in section
IV.E, the EPA committed to work with air agencies as they prepare
complete demonstration packages and we developed some guidelines to
increase the efficiency of the process.
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\131\ Interim Guidance to Implement Requirements for the
Treatment of Air Quality Monitoring Data Influenced by Exceptional
Events. Memorandum from Stephen D. Page, U.S. EPA Office of Air
Quality Planning and Standards, to Regional Air Directors, Regions
I-X. May 10, 2013. Available at http://www2.epa.gov/sites/production/files/2015-05/documents/exceptevents_guidememo_130510.pdf.
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One of the efficiency-increasing measures we suggested in the
Interim Exceptional Events Implementation Guidance was the Letter of
Intent. The guidance explained that the Letter of Intent was a
voluntary process by which the submitting air agency notifies the
reviewing EPA Regional office of the air agency's intent to submit a
demonstration for an identified exceptional event. The purpose of the
letter was to promote early communication between the submitting air
agency and the reviewing EPA Regional office. In the time since issuing
the Interim Exceptional Events Implementation Guidance, several air
agencies and the EPA Regional offices have successfully used this
voluntary process to discuss expectations regarding specific
exceptional events demonstrations.
b. Proposed Changes
As part of the best practices for communications during the
exceptional events process and to aid all agencies in resource planning
and prioritization, the EPA proposes that air agencies and the EPA
engage in regular communications
[[Page 72885]]
to identify those data that have been potentially influenced by an
exceptional event, to determine whether the identified data affect a
regulatory determination, and to discuss whether an air agency should
develop and submit an exceptional events demonstration. In most
instances, these discussions will be between individual air agencies
and the reviewing EPA Regional office. In other cases, the EPA regional
office, or an individual air agency within the purview of the EPA
Regional office, may initiate and/or host a general discussion with all
air agencies in the region followed by individual discussions, as
needed. In still other cases, such as where large events cross state
lines and when two or more states are pursuing exclusion for the same
event(s), the EPA region or regions may initiate discussions will all
potentially affected states/agencies to assist in coordinating states
affected by regional events.
For purposes of this proposed action, the EPA is referring to these
communications as the ``Initial Notification of Potential Exceptional
Event'' (Initial Notification) process. The EPA has changed the name of
this process from the Letter of Intent in recognition of the fact that
effective communication may have multiple formats and does not
necessarily consist of a formal, written letter to convey important
information. As with the voluntary Letter of Intent, the ultimate
purpose of the Initial Notification process is to initiate
conversations between an air agency and the EPA if not already on-
going, or engage in more detailed discussions if a process is currently
in place, regarding specific data and whether the identified data are
ripe for submittal as exceptional events. As stakeholders have
repeatedly expressed and as the EPA acknowledges, the identification of
data affected by exceptional events and the subsequent preparation,
submittal and review of demonstration packages is a resource intensive
process both for the preparing air agency and the reviewing EPA
Regional office.
However, in considering the exceptional events process, it is
important to note that if these data do not have regulatory
significance, then engaging in the development and review of an
exceptional events demonstration is generally not an efficient use of
an air agency's or the EPA's limited resources. The Initial
Notification process will focus efforts on the relevant data and
provide the EPA with the opportunity to convey to the affected air
agency our initial thoughts regarding the identified event and analyses
that may or may not be appropriate for inclusion in a demonstration,
and, with respect to regulatory significance, which demonstrations the
EPA will consider for review. We believe that this approach will help
air agencies make the best use of their available resources.
As noted earlier, the Initial Notification could include any form
of communication (e.g., letter, email, in-person meeting with an
attendees' list and discussion summary or phone conversation with
follow-up email) that ultimately identifies the potential need to
develop an exceptional events demonstration and communicates key
information related to the data identified for potential exclusion.
Where an air agency independently identifies event-affected data and
the need to submit an exceptional events demonstration outside of its
regular, on-going communications with the EPA Regional office, the air
agency could prepare a letter or email communicating its Initial
Notification. Generally, the EPA anticipates that air agencies would
develop and provide an Initial Notification as soon as the agency
identifies event-influenced data that potentially influence a
regulatory decision or when an agency wants the EPA's input on whether
or not to prepare a demonstration.\132\ The EPA further proposes that
each Initial Notification would include the following components:
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\132\ The EPA recognizes that air agencies can immediately
identify those events that result in an exceedance of a NAAQS with a
short averaging time (e.g., 1-hour, 8-hour or 24-hour standards) but
may need additional time for an annual average standard. An air
agency could also submit an annual Initial Notification if annual
submittal makes sense for resource planning or for recurring
seasonal events.
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Unique event name (field in AQS)--facilitates future
communication and understanding between the submitting air agency and
the reviewing EPA Regional office, particularly if an air agency has
submitted multiple exceptional events demonstration packages.
Initial event description (field in AQS)--provides a brief
narrative of the event that could also include maps or graphs similar
to what an air agency might include in the proposed conceptual model
discussed in section V.G.6 of this proposed action; the event
description would include a qualitative description of the event and,
at a minimum, briefly describe the agency's current understanding of
interaction of emissions with the event, transport and meteorology
(e.g., wind patterns such as strength, convergence, subsidence,
recirculation) and pollutant formation in the area.
Affected regulatory decision--provides a description of
the regulatory action or actions potentially affected by the claimed
event-influenced data and the anticipated timing of this action.
Proposed target date for demonstration submittal--
identifies the proposed target date by which the air agency would
submit a demonstration package to the reviewing EPA Regional office.
Most recent design value including and excluding the
event-affected data (optional)--the air agency's assessment of the most
recent design value both with and without the identified event(s) is
helpful when assessing regulatory significance. The EPA cannot
calculate this value (and therefore may not be able to determine
significance) if the air agency has flagged more data than it intends
to include in an exceptional events demonstration.
Information specific to each monitored day--see Table 5,
which would be developed by the submitting air agency and generated
from the initial event description in AQS (see discussion in section
V.G.4).
Table 5--Initial Notification Information Specific to Each Monitored Day
--------------------------------------------------------------------------------------------------------------------------------------------------------
Monitor AQS
Agency/planning area State County Event name Type of NAAQS ID and site Date(s) of Monitor exceedance
in AQS event name event concentration
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............ ............ ............ ............ ............ ............ ............ ....................
-----------------------------------
............ ............ ............ ............ ............ ............ ............ ....................
-----------------------------------
............ ............ ............ ............ ............ ............ ............ ....................
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[[Page 72886]]
The EPA anticipates promptly acknowledging an air agency's Initial
Notification and then formally responding within 90 days of receipt via
letter, email or in-person meeting with an attendees' list and
discussion summary. We also anticipate having informal phone
conversations with the air agency prior to this formal response. As
previously discussed, the EPA will generally prioritize exceptional
events determinations that affect near-term regulatory decisions.\133\
Where the data are to be used in initial area designations, the EPA
proposes to rely on the promulgated documentation submission schedule
in Table 1 at Sec. 50.14(c)(2)(vi). Where the data will influence
another near-term regulatory decision, the EPA proposes to rely on the
case-by-case timelines by which the air agency should submit the
demonstration. For case-by-case demonstrations, the EPA's recommended
date for demonstration submittal would consider the nature of the
event, the anticipated timing of the regulatory decision, and would
allow time for both an air agency's preparation of the demonstration
and the EPA's review. The EPA may not be able to review and act on
demonstrations submitted after the recommended submittal date.
Additionally, the EPA will request in its response that, if the
submitting air agency has not already identified the affected data
within AQS, that it undertake this effort according to the process
described in section V.G.4. If the data identified in the Initial
Notification do not have regulatory significance (and there is no
compelling reason for excluding data), then the EPA will indicate this
in its correspondence back to the air agency and will discourage the
air agency from devoting resources to developing a demonstration
because the EPA will likely not review or act upon the submittal.
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\133\ ``Regulatory decisions'' include findings as to whether
the area has met the applicable NAAQS, classification
determinations, attainment demonstrations, the development of
Limited Maintenance Plans and clean data findings.
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If after discussing the content of a submitted Initial Notification
and/or receiving the EPA's response to the Initial Notification, the
EPA acknowledges that identified data have regulatory significance (or
some other compelling reason for excluding data), then the air agency
should proceed with the development of a technical demonstration
package that satisfies the requirements in 40 CFR 50.14 and accounts
for any case-specific advice from the EPA and additional information in
the EPA's guidance documents.\134\ Although air agencies can submit
demonstrations for events that do not affect a regulatory action, the
EPA will likely not review or act on such submittals.
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\134\ Interim Guidance to Implement Requirements for the
Treatment of Air Quality Monitoring Data Influenced by Exceptional
Events. Memorandum from Stephen D. Page, U.S. EPA Office of Air
Quality Planning and Standards, to Regional Air Directors, Regions
I-X. May 10, 2013. Available at http://www2.epa.gov/sites/production/files/2015-05/documents/exceptevents_guidememo_130510.pdf.
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For these reasons described in this section and in section V.G.4,
the EPA proposes to revise the language in 40 CFR 50.14(c)(2)(i) as
follows: ``A State shall notify EPA of its intent to request exclusion
of one or more measured exceedances of an applicable ambient air
quality standard as being due to an exceptional event by creating an
initial event description and flagging the associated data that have
been submitted to the AQS database and by engaging in the Initial
Notification of Potential Exceptional Event process.'' Specific steps
in the Initial Notification process are identified in rule text at the
end of this document. The EPA solicits comment on the proposed rule
text revision (in 40 CFR 50.14(c)(2)) to require an Initial
Notification of Potential Exceptional Event, with a provision that the
EPA can waive the Initial Notification requirement on a case-by-case
basis. Alternatively, the EPA solicits comment on making the Initial
Notification of Potential Exceptional Event a voluntary process.
Additional proposed revisions would continue at (ii): ``The data
shall not be excluded from determinations with respect to exceedances
or violations of the national ambient air quality standards unless and
until, following the State's submittal of its demonstration pursuant to
paragraph (c)(3) of this section and EPA review, EPA notifies the State
of its concurrence by placing a concurrence flag in the appropriate
field for the data record in the AQS database.''
As noted in section V.G.4, the EPA is proposing to remove the
``general'' flagging schedule in 40 CFR 50.14(c)(2)(iii). The EPA seeks
comments on these proposed changes to the language at 40 CFR
50.14(c)(2), which more clearly identify the process for flagging data
in AQS and requesting exclusion of one or more measured exceedances of
an applicable ambient air quality standard.
The EPA notes that the recent final rule to revise the ozone NAAQS
also removed and reserved the subsequent sections at 40 CFR
50.14(c)(2)(iv) and (v), which addressed the submittal of exceptional
events demonstrations that could affect regulatory determinations
associated with initial area designations for the 2006 24-hour
PM2.5 NAAQS and the 2010 Lead NAAQS and were made obsolete
by the passage of time. The EPA will retain these removed and reserved
sections as promulgated in the ozone NAAQS and proposes no additional
changes to these sections.
6. Submission of Demonstrations
a. Current Situation
With the recent ozone NAAQS, the EPA proposed and promulgated
changes to the current exceptional events regulatory language at 40 CFR
50.14(c)(2) and (3) to include finalizing exceptional events flagging
and demonstration submittal schedules related to implementing the
revised ozone standards and future revised NAAQS and removing obsolete
regulatory language for expired exceptional events deadlines. Sections
V.G.4 and V.G.5 discuss the current situation and additional proposed
changes to 40 CFR 50.14(c)(2). This section discusses the current
situation and proposed revisions to 40 CFR 50.14(c)(3).
As part of the recent final rule to revise the ozone NAAQS, the
regulatory language at 40 CFR 50.14(c)(3)(i) now refers to a revised
exceptional events flagging and demonstration submittal schedule for
data that could be used in initial area designation decisions following
promulgation of any future revised NAAQS. However, the language at 40
CFR 50.14(c)(3)(i) still requires air agencies to ``. . . submit a
demonstration to justify data exclusion to EPA not later than the
lesser of, 3 years following the end of the calendar quarter in which
the flagged concentration was recorded or, 12 months prior to the date
that a regulatory decision must be made by EPA.''
As identified in section V.G.4 of this proposal, air agencies have
previously expressed concern that the timelines for event flagging and
demonstration submittal are not always appropriate because an air
agency may not know that data influenced by an exceptional event caused
the design value exceedance until 3 years after the event
occurred.\135\ The EPA acknowledges that this scenario can occur.
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\135\ Responses to Significant First-Round Comments on the Draft
Guidance Documents on the Implementation of the Exceptional Events
Rule, U.S. EPA, June 2012. Available in Docket No. EPA-HQ-OAR-2011-
0887.
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[[Page 72887]]
In addition to establishing a general schedule for demonstration
submittal, the regulatory language at 40 CFR 50.14(c)(3)(i) requires
that ``A State must submit the public comments it received along with
its demonstration to EPA.'' Although this language is included in 40
CFR 50.14(c)(3)(i), it refers to the regulatory language at 40 CFR
50.14(c)(3)(v), which requires the air agency to document, and submit
with its demonstration, evidence that it followed the public comment
process. Regarding this requirement to ``document that the public
comment process was followed,'' neither the Exceptional Events Rule
language in 40 CFR 50.14 nor the preamble to the promulgated 2007
Exceptional Events Rule specifies a minimum timeframe for public
comment. Many air agencies have been posting draft demonstrations for
public review on their Web sites. The EPA has reviewed several of these
postings and identified 30-days as an often cited timeframe for public
comment on a draft exceptional events demonstration submittal.
The current rule also provides at 40 CFR 50.14(c)(3)(iv) that the
demonstration to justify data exclusion shall provide evidence that the
event satisfies the definition of an exceptional event provided at 40
CFR 50.1(j); that there is a clear causal relationship between the
monitored exceedance and the event that is claimed to have affected the
air quality in the area; that the event is associated with a measured
concentration in excess of normal historical fluctuations, including
background; and that there would have been no exceedance or violation
but for the event. Air agencies have found this section of the 2007
Exceptional Events Rule to be confusing because it contains a mix of
statutory requirements and regulatory language without clearly
identifying the components that the EPA expects to see in an
exceptional events demonstration. As the EPA expressed in the Interim
Exceptional Events Implementation Guidance, all parties would benefit
from clear expectations regarding demonstration components.
The EPA further believes, and recommended in the Interim High Winds
Guidance document, that each demonstration begin with a conceptual
model, or narrative, describing the event(s) causing the exceedance or
violation and a discussion of how emissions from the event(s) led to
the exceedance at the affected monitor(s). As described in the Interim
High Winds Guidance document, the narrative conceptual model could
include varying levels of detail depending on the event complexity, but
in all cases would provide a qualitative description of the event,
interaction of the event-generated emissions with transport and
meteorology (e.g., wind patterns such as strength, convergence,
subsidence, recirculation) and pollutant formation in the area with the
exceeding monitor. Because, in some cases, monitored data or technical
analyses may seem to contradict the event claim, particularly the clear
causal relationship, an air agency can use the conceptual model to
explain, with a weight of evidence approach, why the majority of the
data or analyses are consistent with the event's impact on a measured
exceedance or violation (for example, for a wildfire, why most of the
meteorology would have indicated a lower ozone day without the fire
emissions, even if the temperature were high). A useful conceptual
model also includes (1) a description of the regulatory decision
impacted by the exceptional event, (2) a summary table of the data
requested for exclusion and (3) maps and/or summary tables of event-
related information including location; size and extent; point and
explanation of origin. A conceptual model can additionally include
examples of media coverage of the event.\136\ Since releasing the
Interim High Winds Guidance document in 2013, the EPA has received
several demonstrations that included a conceptual model. The EPA has
found it very helpful to understand the event formation and the event's
influence on monitored pollutant concentrations before beginning to
review the individual technical evidence to support the requested data
exclusion.
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\136\ The EPA expects that air agencies could use some of the
same information and tables in both the conceptual model and the
Initial Notification of Potential Exceptional Event, which is
discussed in section V.G.5 of this proposal.
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b. Proposed Changes
For the previously mentioned reasons, the EPA is proposing and
soliciting comment on the following changes to the regulatory language
in 40 CFR 50.14(c)(3) regarding the submission of demonstrations:
Removing the general schedule provisions in 40 CFR
50.14(c)(3)(i) for submitting demonstrations.
Moving the language requiring a state to include the
comments it received during the public comment period for the subject
demonstration from 40 CFR 50.14(c)(3)(i) to 40 CFR 50.14(c)(3)(v).
Modifying the language at 40 CFR 50.14(c)(3)(iv) to more
clearly identify the required elements of an exceptional events
demonstration to include (1) a narrative conceptual model and (2)
demonstrations and analysis that address the core statutory technical
criteria [the event affected air quality in such a way that there
exists a clear causal relationship between the specific event and the
monitored exceedance or violation (as indicated by the comparison to
historical concentrations showing and other analyses), the event was a
human activity that is unlikely to recur at a particular location or
was a natural event, the event was not reasonably controllable or
preventable].
Modifying the language at 40 CFR 50.14(c)(3)(v) to
identify that a demonstration submittal must include (1) documentation
that the air agency conducted a public comment process on its draft
exceptional events demonstration that was a minimum of 30 days, which
could be concurrent with the EPA's review, (2) any public comments
received during the public comment period and (3) an explanation of how
the air agency addressed the public comments.
To elaborate on removing the general schedule provisions in 40 CFR
50.14(c)(3)(i), the EPA proposes to remove the provision in 40 CFR
50.14(c)(3)(i) that requires air agencies to submit a demonstration
``not later than the lesser of 3 years following the end of the
calendar quarter in which the flagged concentration was recorded or 12
months prior to the date that a regulatory decision must be made by
EPA.'' In place of this language, the EPA proposes to rely on the
promulgated documentation submission schedule in Table 1 at
50.14(c)(2)(vi) in those cases where the data are to be used in initial
area designations. If the data could influence a regulatory
determination other than initial area designations, the EPA proposes to
rely on the case-by-case timelines established by the reviewing EPA
Regional office as part of the Initial Notification of Potential
Exceptional Event process.
With respect to the public comment provisions for a developed
demonstration, for the reasons stated previously, the EPA proposes to
move the language requiring an air agency to include the comments it
received during the public comment period for the subject demonstration
from 40 CFR 50.14(c)(3)(i) to 40 CFR 50.14(c)(3)(v) to consolidate the
required elements of the public comment process for exceptional events
demonstrations within a single regulatory provision. The EPA also
proposes to specify a minimum 30-day public comment process, which
provides sufficient time for exchange between the reviewing public and
the
[[Page 72888]]
air agency. Shorter comment periods may not provide necessary time for
the public to research the identified event and associated supporting
data while longer timeframes may not be possible where a near-term
regulatory decision relies on an exceptional events decision. The EPA
notes that in very limited cases where the air agency is relying on
exceptional events claims as part of a near-term regulatory action,
such as a demonstration for events in the third year of a 3-year design
value that will be used in initial area designations for a new or
revised NAAQS under a 2-year designation schedule, the public comment
period could be concurrent with the EPA's review provided the
submitting air agency sends any public comments and responses to the
EPA by a specified date should comments be submitted. If an air agency
receives public comment disputing the technical elements of a
demonstration during a comment period that runs concurrent with the
EPA's review and these comments result in the air agency's need to
reanalyze or reassess the validity of a claimed event, a second public
comment period may be necessary.
The EPA also proposes to revise the language at 40 CFR
50.14(c)(3)(iv) so that it more clearly identifies the required
elements of an exceptional events demonstration. As previously
described, the EPA proposes that each demonstration begin with a
narrative conceptual model, which summarizes the event in question and
provides context for required statutory technical criteria analyses.
The EPA further proposes, consistent with other proposed changes in
this action, that an air agency include in its demonstration to justify
data exclusion evidence that the following statutory technical criteria
are satisfied:
The event was a human activity that is unlikely to recur
at a particular location or was a natural event.
The event was not reasonably controllable or preventable.
The event affected air quality in such a way that there
exists a clear causal relationship between the specific event and the
monitored exceedance or violation (supported in part by the comparison
to historical concentrations and other analyses).
The EPA seeks comments on the identified proposed changes to the
language at 40 CFR 50.14(c)(3)(i), (iv) and (v), which more clearly
identify the required elements of an exceptional events demonstration.
The EPA notes that the recent final rule to revise the ozone NAAQS
also removed and reserved the subsequent sections at 40 CFR
50.14(c)(3)(ii) and (iii), which addressed the submittal of exceptional
events demonstrations that could affect regulatory determinations
associated with initial area designations for the 2006 24-hour
PM2.5 NAAQS and the 2010 Lead NAAQS and were made obsolete
by the passage of time. The EPA will retain these removed and reserved
sections as promulgated in the ozone NAAQS and proposes no additional
changes to this language.
7. Timing of the EPA's Review of Submitted Demonstrations
a. Current Situation
Since promulgation of the Exceptional Events Rule in 2007,
stakeholders have questioned the process by which the EPA reviews
submitted demonstrations.\137\ Specifically, stakeholders have
expressed concern that the EPA has a backlog of submittals but acts
only on EPA-prioritized packages. Stakeholders have stated that because
the EPA has not acted on all submissions, the air quality values used
for planning and regulatory purposes are higher than they would be if
the effects of non-controllable emissions were removed from the data
set. Air agencies have also noted that without feedback, they do not
know the EPA's expectations regarding future submittals.
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\137\ See comment letters in Docket ID No. EPA-HQ-OAR-2011-0887
for the July 2012 notice of availability for the Draft Exceptional
Events Implementation Guidance, which the EPA has incorporated into
the record for this action.
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The EPA addressed these questions and comments in the Interim
Exceptional Events Implementation Guidance. In Question 27 of the
Interim Q&A document, the EPA identified the general process and timing
for demonstration reviews. In this document, the EPA clarified the
process by which it prioritizes submittals and indicated that we may
not act on submittals with no regulatory significance. The guidance
also presented the voluntary Letter of Intent concept as a mechanism to
aid in planning and prioritization. Additionally, we stated that we
intend to make a decision regarding concurrence with an air agency's
request to exclude data as expeditiously as necessary following
submittal of a complete package if required by a near-term regulatory
action. We also indicated our intent to communicate with the submitting
agency, as needed, during the demonstration review period.
b. Proposed Changes
In this proposal, the EPA is clarifying some of our previous
statements regarding the prioritization and submittal of
demonstrations. As noted in several subsections within section V.G of
this proposal, we also propose to codify in regulatory language
approaches to increase the efficiency of preparing, submitting and
reviewing exceptional events demonstrations. Although the EPA is not
proposing to codify in regulatory language any changes pertaining to
the timing of the EPA review process, the EPA offers the following
discussion to clarify expectations and facilitate communications, which
are at the center of timing-related issues.
As noted in the Interim Exceptional Events Implementation Guidance
and in the EPA's best practices discussions described in section IV.E,
the EPA is committed to working with air agencies as they prepare
complete demonstration packages. The EPA encourages ongoing discussions
between the reviewing EPA Regional office and the submitting air agency
from the onset of the Initial Notification of Potential Exceptional
Event process through official package submittal. Since renewing our
focus on improved communications, the EPA has received positive
feedback from engaged agencies that have used this approach.
Additionally, these communications have resulted in decreased instances
of submissions containing insufficient or unnecessary information.
In reviewing submitted demonstration packages, the EPA will
generally give priority to exceptional events determinations that may
affect near-term regulatory decisions, such as EPA action on SIP
submittals, NAAQS designations and clean data determinations. The EPA
intends to make a decision regarding event status expeditiously
following submittal of a complete package if required by a near-term
regulatory action. If during the review process the EPA identifies the
need for additional information to determine whether the exceptional
events criteria are met, the EPA will notify the submitting air agency
and encourage the agency to provide the supplemental information. If
the information needed is minor and a natural outgrowth of what was
previously submitted, the EPA will not require the air agency to
undergo an additional public notice-and-comment process. However, if
the needed information is significant, the EPA may request that the air
agency re-notice the demonstration before resubmitting it to the EPA,
thus requiring an additional
[[Page 72889]]
EPA review following resubmittal. The EPA will work with air agencies
on supplemental timeframes; however, the mandatory timing of the EPA
actions may limit the response time the EPA allows. The EPA proposes to
include as rule text a requirement for the air agency to submit
additional information within 12 months. If additional information is
not received in 12 months, then the EPA will consider the submitted
demonstration inactive, and will not continue the review or take
action. In effect, an air agency's lack of response within a 12-month
period will ``void'' the submittal. In these cases, the EPA does not
intend to issue a formal notice of deferral. If the air agency later
decides to pursue the exceptional events claim after a 12-month period
of inactivity, it may re-initiate the exceptional events process by
submitting a new Initial Notification of Potential Exceptional Event
followed by a new demonstration, which could simply be revising the
original submittal to include the additional information previously
requested by the EPA.
At the conclusion of the EPA's review, the EPA will make a
determination regarding the status of a submitted exceptional events
demonstration. The EPA's decision could result in concurrence,
nonconcurrence or deferral.\138\ In acting on a submitted demonstration
covering multiple event days and/or multiple flags, the EPA could
concur with part of a demonstration and nonconcur or defer other
flagged values. If the EPA determines that the events addressed in an
exceptional events demonstration are not anticipated to affect any
future regulatory decision, the EPA could defer review of these events
and notify the submitting agency if a subsequent review results in a
determination that the events do affect a regulatory decision.\139\
Formal mechanisms for deferral could include the EPA's indicating this
decision by letter, by email to a responsible official or during a
high-level meeting with an attendees' list and discussion summary.
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\138\ The EPA anticipates a reduced number of deferrals and/or
nonconcurrences for demonstrations associated with the Initial
Notification of Potential Exceptional Event process as discussed in
section V.G.5 because the EPA and the affected air agency would have
discussed issues/concerns prior to the EPA's decision on a submitted
demonstration.
\139\ Routine status calls between the reviewing EPA Regional
office and air agencies could include an agenda item to review the
status of all submitted demonstrations, including those that the EPA
has deferred.
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8. Dispute Resolution Mechanisms
Since promulgation of the 2007 Exceptional Events Rule and through
the development of the Interim Exceptional Events Implementation
Guidance, some interested parties have asked the EPA to identify a
process by which submitting air agencies can formally dispute the EPA's
decision regarding requests for additional information to support
submitted demonstration packages and/or decisions regarding
concurrence, nonconcurrence or deferral of submitted demonstration
packages. While the EPA acknowledges the expressed concerns and desire
for a formally identified dispute resolution process, the EPA also
believes that several mechanisms currently exist that air agencies can
use at various points in the exceptional events process. These
mechanisms include engaging in early dialogue with the reviewing EPA
Regional office, submitting requests for reconsideration to the
official who made the determination if a request identifies a clear
error or if the reviewing EPA regional office overlooked information
submitted by the affected air agency, and/or elevating the concern
within the EPA's chain of command. Additionally, air agencies can raise
any unresolved event-related issues during the regulatory process that
relies upon the claimed event-influenced data by participating in
related public notice-and-comment processes and/or challenging in an
appropriate court the regulatory decision subsequently made based in
part on the EPA's exceptional events determination. These currently
available dispute resolution approaches to address exceptional events
decisions are consistent with the mechanisms available for other EPA
actions. With exceptional events decisions, however, the air agency has
opportunities to elevate concerns during two processes: the exceptional
events determination and the subsequent regulatory action that relies
on the exceptional events decision.
The EPA believes that the existing mechanisms identified above
combined with the EPA's commitment to focus on communication and
collaboration with the submitting air agency through the exceptional
events demonstration process, and the clarifications that would be in
effect with these proposed revisions to the 2007 Exceptional Events
Rule and associated guidance, will avoid the need for a formal dispute
resolution mechanism for exceptional events. Therefore, the EPA does
not intend to address dispute resolution within these proposed rule
revisions and does not intend to respond to comments on this issue.
VI. Mitigation
A. Current Situation
Section 319(b)(3)(A) of the CAA identifies five principles for the
EPA to follow in developing implementing regulations for exceptional
events:
(i) Protection of public health is the highest priority;
(ii) Timely information should be provided to the public in any
case in which the air quality is unhealthy;
(iii) All ambient air quality data should be included in a timely
manner in an appropriate federal air quality database that is
accessible to the public;
(iv) Each state must take necessary measures to safeguard public
health regardless of the source of the air pollution; and
(v) Air quality data should be carefully screened to ensure that
events not likely to recur are represented accurately in all monitoring
data and analyses.
The regulatory requirements implementing (iii) and (v) of this part
of the statute are found only in 40 CFR 50.14 while the regulatory
requirements implementing (i) and (iv) are found only in 40 CFR 51.930,
Mitigation of Exceptional Events. Both Sec. Sec. 50.14(c)(1) and
51.930(a)(1) require states to provide notice of events to the public
(the second of the five principles).
The language at 40 CFR 51.930 requires air agencies requesting data
exclusion to ``take appropriate and reasonable actions to protect
public health from exceedances or violations of the NAAQS'' and at a
minimum do each of the following:
Provide for prompt public notification whenever air
quality concentrations exceed or are expected to exceed the NAAQS.
Provide for public education concerning actions that
individuals may take to reduce exposures to unhealthy levels of air
quality during and following an exceptional event.
Provide for the implementation of appropriate measures to
protect public health from exceedances or violations of ambient air
quality standards caused by exceptional events.
The EPA promulgated the existing requirements in 2007 after
considering and proposing several approaches to implementing CAA
section 319(b)(3)(A). Some of the proposed approaches would have
established a more formal structure by which air agencies prepared and
submitted to the EPA mitigation plans to protect public health during
events. These plans would have
[[Page 72890]]
been subject to the EPA's approval and/or the approval of the exclusion
of event-affected data would have been contingent on the approval of
such a plan. Comments on these proposed options varied
widely.140 141
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\140\ The Treatment of Data Influenced by Exceptional Events;
Proposed Rule, 71 FR 12592 (March 10, 2006).
\141\ See Comments and Responses related to ``Requirements for
States To Provide Public Notification, Public Education, and
Appropriate and Reasonable Measures To Protect Public Health'' in
Treatment of Data influenced by Exceptional Events; Final Rule, 72
FR 13574-13576 (March 22, 2007).
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In the final 2007 Exceptional Events Rule, ``mitigation'' measures
\142\ became part of the 2007 Exceptional Events Rule, but they were
not incorporated into the criteria and processes by which data are
excluded from use in regulatory determinations. There is no requirement
to submit such measures to the EPA for either prospective or
retrospective review and approval as a condition for approval for
exclusion of event-affected data. Neither are air agencies required to
notify the EPA of the measures an air agency plans to take or has
taken. In the preamble to the 2007 Exceptional Events Rule, we stated
that states should take ``reasonable and appropriate measures'' to
protect public health related to the occurrence of an event and that
states should determine what measures constitute those that are
``reasonable and appropriate.'' \143\ We did not clarify how measures
should be determined to be ``appropriate'' measures.
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\142\ The term ``mitigation'' does not appear in CAA section
319(b). It appears in the title but not the text of 40 CFR 51.930.
\143\ 72 FR 13574 (March 22, 2007).
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The mitigation measures that the EPA sees states most commonly
practicing are ones related to the requirement that air agencies
``provide for prompt public notification whenever air quality
concentrations exceed or are expected to exceed the NAAQS.'' Often,
these public notifications include public health alerts for high wind
dust events or wildfires. We believe that other aspects of mitigation,
including implementing appropriate measures to protect public health
beyond notification, are also important in implementing the CAA guiding
principle that ``each State must take necessary measures to safeguard
public health regardless of the source of the air pollution.''
B. Proposed Changes
Given the EPA's and the states' experience implementing the 2007
Exceptional Events Rule as indicated above, we consider it appropriate
to consider possible changes to the mitigation-related rule components
with the benefit of additional public input. We are seeking comment on
approaches ranging from retaining the existing rule requirements at 40
CFR 51.930 to the various possible new components described in this
section. We invite comment on these alternatives and on other concepts.
We may make no change; we may adopt all of the described new
components; or we may adopt only some features or variations of the
described options. Note that we are not considering requiring all
states to develop formal mitigation plans. We are seeking comment on
the concept of only some states being required to develop mitigation
plans for their particular ``historically documented'' or ``known
seasonal'' exceptional events, defined below in section VI.B.1; on
recommended elements for such mitigation plans described below in
section VI.B.2; and on options for implementing mitigation plans
described in section VI.B.3. Section VI.B.4 summarizes the EPA's
potential options for mitigation elements for exceptional events
purposes.
1. Defining Historically Documented or Known Seasonal Events
The EPA seeks comment on whether an air agency should develop a
mitigation plan for its particular type of ``historically documented''
or ``known seasonal'' exceptional events, if any. The EPA would
consider ``historically documented'' or ``known seasonal'' exceptional
events to include events of the same type and pollutant (e.g., high
wind dust/PM or wildfire/ozone) that meet any of the following
criteria: an event for which an air agency has previously submitted
exceptional events demonstrations; an event that an air agency has
previously flagged for concurrence in AQS (regardless of whether the
air agency submitted a demonstration); or an event that has been the
subject of local news articles, public health alerts or published
scientific journal articles. The EPA would not require an air agency to
develop a mitigation plan for the first event of a given type (e.g., if
an area is prone to wildfires but has never experienced a high wind
dust event, then it would not be expected to develop a mitigation plan
for its first high wind dust event, but it would be expected to develop
a mitigation plan for wildfires). A second event of a given type within
a 3-year period would subject the area to ``having a history'' and,
therefore, needing a mitigation plan.\144\ This option avoids plan
development for a one-of-a-kind occurrence.\145\ In defining ``first''
and ``second'' events, the EPA could consider events that affect the
same AQCR, but not necessarily the same monitor.\146\ For example, high
wind dust events occur seasonally in the Phoenix, Arizona metropolitan
area, which is part of the Maricopa Intrastate Air Quality Control
Region (see 40 CFR 81.36). These events have influenced particulate
matter concentrations at multiple monitors within the Maricopa
Intrastate AQCR. Under this proposal, high wind dust events in Phoenix
(i.e., the Maricopa Intrastate AQCR) are known events requiring a
mitigation plan. On the other hand, a high wind dust event in Sedona,
Arizona, part of the Northern Arizona Intrastate Air Quality Control
Region (see 40 CFR 81.270), would be a first event and not subject to
the development of a mitigation plan. As a variation of this concept on
which we also seek comment, the EPA could consider a first season of
events as one of three required seasons of events, so that a mitigation
plan would be required only when an event type persists across several
years. For example, an area may not have previously experienced
wildfires in the past 10 years, but then experiences multiple wildfires
and multiple exceedances in a single wildfire season. If these multiple
wildfires affect the same general geographic area and monitors in a
relatively short period of time (e.g. 2-3 months), then they could be
considered a single event for purposes of developing a mitigation plan
and would not trigger the requirement for a mitigation plan.
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\144\ A 3-year period is determined based on the submittal date
of an exceptional events demonstration.
\145\ Because the form of the NAAQS varies by pollutant, it is
possible that multiple events in a 3-year period may not cause a
NAAQS violation. An air agency that identifies multiple events of
the same type (e.g., wildfire/ozone) in AQS, but prepares and
submits a demonstration for only one of these events, would trigger
the proposed requirement to develop a mitigation plan.
\146\ Air Quality Control Regions are defined in 40 CFR part 81,
subpart B, Designation of Air Quality Control Regions.
---------------------------------------------------------------------------
2. Mitigation Plan Components
The EPA solicits comment on the following three plan components
that could be recommended or required in order to implement the
mitigation principles found in section 319(b)(3)(A) of the CAA: Public
notification and education; steps to identify, study and implement
mitigating measures and provision for periodic revision of the
mitigation plan (to include public
[[Page 72891]]
review of plan elements). This section discusses these elements in more
detail. A mitigation plan should address actions that would be taken
within a state's own territory for events that happen within its own
territory or that of another jurisdiction.
a. Public notification to and education programs for affected or
potentially affected communities. Air agencies could be required or
encouraged to include in their mitigation plans steps to activate
public notification and education systems whenever air quality
concentrations exceed or are expected to exceed an applicable national
ambient air quality standard. If possible, air agencies would notify
the public of the actual or anticipated event at least 48 hours in
advance of the event using methods appropriate to the community being
served. Outreach mechanisms could include Web site alerts, National
Weather Service alerts, telephone or text bulletins, television or
radio campaigns or other messaging campaigns. Public notification and
education programs could be encouraged or required to include some or
all of the following actions to support the outreach system: adoption
of methods for forecasting/detection, consultation with appropriate
health department personnel regarding issuing health advisories and
suggested actions for exposure minimization for sensitive populations
(e.g., remain indoors, avoid vigorous outdoor activity, avoid exposure
to tobacco smoke and other respiratory irritants and, in extreme cases,
evacuation or public sheltering procedures).
b. Steps to identify, study and implement mitigating measures,
including approaches to address each of the following:
(i) Mandatory or voluntary measures to abate or minimize
contributing controllable sources of identified pollutants. A state
could be required to include or encouraged to consider full-time or
contingent controls on event-related sources as well as non-event
related sources. For example, these measures might include continuously
operating control measures during an extreme event for identified
sources that normally operate these same controls on an intermittent
basis. It could also involve including work practices (e.g., water
spray for dust suppression) or contingent limits during extreme events
on emissions from non-event related sources that, under non-event
periods, have no or less stringent emissions limits or work practices.
(ii) Methods to minimize public exposure to high concentrations of
identified pollutants.
(iii) Processes to collect and maintain data pertinent to the event
(e.g., to identify the data to be collected, the party responsible for
collecting and maintaining the data and when, how and to whom the data
will be reported).
(iv) Mechanisms to consult with other air quality managers in the
affected area regarding the appropriate responses to abate and minimize
impacts. Consultation could include collaboration between potentially
affected local, state, tribal and federal air quality managers and/or
emergency response personnel.
c. Provision for periodic review and evaluation of the mitigation
plan and its implementation and effectiveness by the air agency and all
interested stakeholders (e.g., public and private land owners/managers,
air quality, agriculture and forestry agencies, the public). For
example, air agencies could be required to use this review process and
to revise, if appropriate, and certify the mitigation plan every 3
years or every three events, whichever is longer. The air agency could
be required to submit a summary and response to the comments received
during the public plan review process to the EPA along with the
recertification statement and/or revised mitigation plan. If the
historically documented or known seasonal exceptional events continue
to result in elevated pollutant concentrations above the relevant
NAAQS, thus showing that the combination of the existing SIP and the
existing mitigation plan does not effectively safeguard public health,
the mitigation plan might need to be strengthened during this review.
If the EPA adopts requirements like those described above, it would
not necessarily mean that all affected air agencies would have to
prepare new plans. If an air agency has developed and implemented a
contingency plan under 40 CFR part 51, subpart H, Prevention of Air
Pollution Emergency Episodes, that meets the requirements of 40 CFR
51.152, and that includes provisions for events that could be
considered ``exceptional events'' under the provisions in 40 CFR 50.14,
then the subpart H contingency plan would likely satisfy the mitigation
requirements described above. If the identified basic elements are
included and addressed, including the element for public comment, then
other types of existing mitigation or contingency plans may satisfy the
possible mitigation plan requirement described above. For example, if
an area has developed a natural events action plan or a high wind
action plan covering high wind dust events, this plan likely would
satisfy mitigation elements for high wind dust events. Smoke management
plans and/or forest management plans might also satisfy the mitigation
elements for prescribed fires and wildfires. Most air agencies
generally have sufficient, established processes that meet the public
notification and education element, which can be easily adapted or
modified to meet the mitigation elements proposed in this action. The
EPA is requesting comment on how much time air agencies should be
allowed to develop a plan.
3. Options for Implementing Mitigation Plans
The EPA is seeking comment on two options for tying the proposed
mitigation plan components discussed in section VI.B.2 to the EPA
review of exceptional events demonstrations. Option 1 includes the
EPA's review for completeness but not substantive approval or
disapproval, while Option 2 includes the EPA's approval of the
substance of the mitigation plan. These options are discussed below in
more detail, but neither option would require a mitigation plan to be
included in a SIP or to be otherwise federally-enforceable.
Under both options, air agencies with historically documented or
known seasonal exceptional events could submit the mitigation plan to
the EPA in advance of an event, or submit a mitigation plan along with
an exceptional events demonstration. The EPA would concur with a
demonstration for the relevant event type only if a mitigation plan has
passed the type of EPA review described in the option. Given that the
air agency would have advance notification of the need to develop a
plan, the air agency could develop and submit the mitigation plan in
advance of any exceptional events demonstration so that the EPA could
pre-review the mitigation plan and take faster action on an exceptional
events submittal once one is submitted.
Option 1: Under this option, the EPA would review for inclusion of
required elements as described above and to ensure that the development
of the mitigation plan included a public comment process. We would not
formally review the substance of the plan in the sense of approving the
details of the specific measures and commitments in the plan.
Option 2: Under this option, EPA approval of the substance of the
mitigation plan would be a precondition for EPA concurrence on an
exceptional events demonstration. Because the EPA would approve the
content, completeness and sufficiency of a mitigation plan, the EPA's
disapproval
[[Page 72892]]
of the plan could result in the EPA's nonconcurrence on a current or
future exceptional events demonstration.
VII. Draft Guidance on the Preparation of Exceptional Events
Demonstrations for Wildfire Events That May Influence Ozone
Concentrations
A. What is this draft guidance about and why is it needed?
The Exceptional Events Rule contains the regulatory requirements
and criteria necessary for the EPA's approval of the exclusion of air
quality data from regulatory determinations related to NAAQS
exceedances or violations. During the implementation of the 2007
Exceptional Events Rule, the EPA and stakeholders have identified a
need for implementation guidance that provides an interpretation of and
examples for addressing the regulatory requirements specific to the
most common event types. One event type that has been identified by the
EPA and stakeholders is wildfire influence on ozone concentrations. In
2013, the EPA finalized the Interim Exceptional Events Implementation
Guidance documents (see section IV.D), which included the Interim High
Winds Guidance document and an Interim Overview document that also
committed to the preparation of a Draft Wildfire Ozone Guidance
document. The EPA intends to address this need and commitment via the
Draft Guidance on the Preparation of Exceptional Events Demonstrations
for Wildfire Events that May Influence Ozone Concentrations (``Draft
Wildfire Ozone Guidance document''), which accompanies this proposed
rule and is also available for comment.
This Draft Wildfire Ozone Guidance document includes example
analyses, conclusion statements and technical tools that air agencies
can use to provide evidence that the wildfire event influenced the
monitored ozone concentration. The Draft Wildfire Ozone Guidance
document also identifies fire and monitor-based characteristics that
might allow for a simpler and less resource-consuming demonstration
package. The EPA has developed the Draft Wildfire Ozone Guidance
document concurrently with the proposed Exceptional Events Rule
revisions so that the Draft Wildfire Ozone Guidance reflects the
proposed rule changes. Once finalized, this guidance will provide the
EPA regional offices and air agencies with guidance on how to prepare
and submit evidence to meet the Exceptional Events Rule requirements
for monitored ozone exceedances caused by wildfires. The guidance, when
finalized, will not be an EPA rule, and in specific cases the EPA may
depart from the guidance for reasons that the EPA will explain at the
time of the action.
B. What scenarios are addressed in the draft guidance?
The EPA has prepared the Draft Wildfire Ozone Guidance document to
provide assistance and example analyses for wildfire events that may
influence ozone concentrations. Though many of the technical analyses
included in the draft document may also be applied to prescribed fire
events, the draft guidance document available for comment at this time
does not provide guidance specific on how prescribed fire events can
address all proposed rule requirements. Limiting the scope to wildfire
events is intended to make the document easier to use for wildfire
events. With this notice, the EPA invites comment on the content of
this guidance document and whether it is appropriate to expand the
scope of the guidance to include prescribed fire events. If commenters
believe it is necessary to expand the scope of the EPA's final new
guidance beyond the scope of the Draft Wildfire Ozone Guidance
document, the EPA seeks comment on whether wildfire and prescribed fire
events should be addressed in a single fire ozone guidance document or
in separate guidance documents.
VIII. Environmental Justice Considerations
The Exceptional Events Rule provides the criteria by which state,
local and tribal air agencies identify air quality data they believe
have been influenced by exceptional events, which by statutory
definition are not reasonably controllable or preventable. Because
these events are not reasonable to prevent or control, they can affect
all downwind populations including minority and low-income populations.
For this reason, in adding section 319(b) to the CAA, Congress
identified as a guiding principle in developing regulations, ``the
principle that protection of public health is the highest priority.''
The 2007 Exceptional Events Rule at 40 CFR 50.14 requires air agencies
to seek public comment on prepared exceptional events demonstrations
prior to submitting them to the reviewing EPA regional office. The
public can also comment on rulemakings that include decisions related
to the exclusion of event-influenced data. The mitigation of
exceptional events language at 40 CFR 51.930 also requires that air
agencies provide public notification and education programs related to
events. To protect all people and communities, notably minority and
low-income populations, air agencies should ensure that notifications
and education programs are communicated using the language (e.g.,
English and Spanish) and media (e.g., radio and postings in local
community centers) best suited to the target audience(s). Additionally,
these proposed revisions are part of a public notice-and-comment
rulemaking effort, which will include a public hearing. These
opportunities for public input and education ensure that all those
residing, working, attending school or otherwise present in areas
affected by exceptional events, regardless of minority and economic
status, are protected.
IX. Statutory and Executive Order Reviews
A. Executive Order 12866: Regulatory Planning and Review and Executive
Order 13563: Improving Regulation and Regulatory Review
This action is a significant regulatory action that was submitted
to the Office of Management and Budget (OMB) for review because it
raises novel policy issues. Any changes made in response to OMB
recommendations have been documented in the docket.
B. Paperwork Reduction Act
This action does not impose any new information collection burden
under the PRA. The information being requested under these proposed
rule revisions is consistent with current requirements related to
information needed to verify the authenticity of monitoring data
submitted to the EPA's AQS database, and to justify exclusion of data
that have been flagged as being affected by exceptional events. OMB has
previously approved the information collection activities for ambient
air monitoring data and other supporting measurements reporting and
recordkeeping activities associated with the 40 CFR part 58 Ambient Air
Quality Surveillance rule and has assigned OMB control number 2060-
0084.
C. Regulatory Flexibility Act (RFA)
I certify that this action will not have a significant economic
impact on a substantial number of small entities under the RFA. This
action will not impose any requirements on small entities. Instead, the
proposed rule revisions provide the criteria and increase the
efficiency of the process by which state, local and tribal air agencies
identify air quality data they believe
[[Page 72893]]
have been influenced by an exceptional event. The proposed rule
revisions also clarify those actions that state, local and tribal air
agencies should take to protect public health during and following an
exceptional event. Because affected air agencies 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 event, the EPA cannot predict the indirect effect of the
rule on sources that may be small entities.
D. Unfunded Mandates Reform Act (UMRA)
This action does not contain an unfunded mandate of $100 million or
more as described in UMRA, 2 U.S.C. 1531-1538, and does not
significantly or uniquely affect small governments. The action imposes
no enforceable duty on any state, local or tribal governments or the
private sector.
E. Executive Order 13132: Federalism
This action does not have federalism implications. The EPA
believes, however, that this action may be of significant interest to
states and to local air quality agencies to whom a state has delegated
relevant responsibilities for air quality management. Consistent with
the EPA's policy to promote communications between the EPA and state
and local governments, the EPA consulted with representatives of state
and local governments early in the process of developing this action to
permit them to have meaningful and timely input into its development. A
summary of the concerns raised during that consultation is provided in
section IV of this preamble.
F. Executive Order 13175: Consultation and Coordination With Indian
Tribal Governments
This action does not have tribal implications as specified in
Executive Order 13175. It would not have a substantial direct effect on
one or more Indian tribes. Furthermore, these proposed regulation
revisions do not affect the relationship or distribution of power and
responsibilities between the federal government and Indian tribes. The
CAA and the TAR establish the relationship of the federal government
and tribes in characterizing air quality and developing plans to attain
the NAAQS, and these revisions to the regulations do nothing to modify
that relationship. Thus, Executive Order 13175 does not apply to this
action.
Although Executive Order 13175 does not apply to this action, the
EPA held public meetings attended by tribal representatives and
separate meetings with tribal representatives to discuss the revisions
proposed in this action. The EPA also provided an opportunity for all
interested parties to provide oral or written comments on potential
concepts for the EPA to address during the rule revision process.
Summaries of these meetings are included in the docket for this
proposed rule. The EPA specifically solicits additional comment on this
proposed action from tribal officials.
G. Executive Order 13045: Protection of Children From Environmental
Health & Safety Risks
The EPA interprets Executive Order 13045 as applying only to those
regulatory actions that concern environmental health or safety risks
that the EPA has reason to believe may disproportionately affect
children, per the definition of ``covered regulatory action'' in
section 2-202 of the Executive Order. This action is not subject to
Executive Order 13045 because it does not concern an environmental
health risk or safety risk.
H. Executive Order 13211: Actions Concerning Regulations That
Significantly Affect Energy Supply, Distribution or Use
This action is not a ``significant energy action'' because it is
not likely to have a significant adverse effect on the supply,
distribution or use of energy. The purpose of this proposed rule is to
provide the criteria, and increase the efficiency of the process, by
which state, local and tribal air agencies may identify air quality
data they believe have been influenced by an exceptional event. The EPA
does not expect these activities to affect energy suppliers,
distributors or users.
I. National Technology Transfer and Advancement Act
This rulemaking does not involve technical standards.
J. Executive Order 12898: Federal Actions To Address Environmental
Justice in Minority Populations and Low-Income Populations
The EPA believes the human health or environmental risk addressed
by this action will not have potential disproportionately high and
adverse human health or environmental effects on minority, low-income
or indigenous populations. The results of this evaluation are contained
in the section of the preamble titled ``Environmental Justice
Considerations.'' This proposed action provides the criteria and
increases the efficiency of the process by which state, local and
tribal air agencies identify air quality data they believe have been
influenced by exceptional events, which, by statutory definition, are
not reasonably controllable or preventable. These proposed regulatory
provisions do, however, provide information concerning actions that
state, local or tribal air agencies might take to uniformly protect
public health once the EPA has concurred with an air agency's request
to exclude data influenced by an exceptional event. The mitigation
component of the proposed rule could ultimately provide additional
protection for minority, low income and other populations located in
areas affected by exceptional events. Therefore, the EPA finds that
this proposed action would not adversely affect the health or safety of
minority or low-income populations, and that it is designed to protect
and enhance the health and safety of these and other populations.
X. Statutory Authority
The statutory authority for this action is provided by 42 U.S.C.
7401, et seq.
List of Subjects in 40 CFR Part 50
Environmental protection, Air pollution control, National parks,
Wilderness areas.
Dated: November 10, 2015.
Gina McCarthy,
Administrator.
For the reasons set forth in the preamble, it is proposed that 40
CFR part 50 be amended as follows:
PART 50--NATIONAL PRIMARY AND SECONDARY AMBIENT AIR QUALITY
STANDARDS
0
1. The authority citation for part 50 continues to read as follows:
Authority: 42 U.S.C. 7401, et seq.
0
2. Amend Sec. 50.1 by:
0
a. Revising paragraphs (j) and (k).
0
b. Adding paragraphs (m), (n), (o), (p), (q) and (r).
The revisions and additions read as follows:
Sec. 50.1 Definitions.
* * * * *
(j) Exceptional event means an event and its resulting emissions
that affect air quality in such a way that there exists a clear causal
relationship between the specific event and the monitored exceedance or
violation, is not reasonably controllable or preventable, is an event
caused by human activity that is unlikely to recur at a particular
location or a natural event, and is determined by the Administrator in
accordance with 40 CFR 50.14 to be an
[[Page 72894]]
exceptional event. It does not include stagnation of air masses or
meteorological inversions, a meteorological event involving high
temperatures or lack of precipitation, or air pollution relating to
source noncompliance.
(k) Natural event means an event and its resulting emissions, which
may recur, in which human activity plays little or no direct causal
role. Anthropogenic sources that are reasonably controlled shall be
considered to not play a direct role in causing emissions.
* * * * *
(m) Prescribed fire is any fire intentionally ignited by management
actions in accordance with applicable laws, policies, and regulations
to meet specific land or resource management objectives.
(n) Wildfire is any fire started by an unplanned ignition caused by
lightning; volcanoes; other acts of nature; unauthorized activity; or
accidental, human-caused actions, or a prescribed fire that has been
declared to be a wildfire. A wildfire that predominantly occurs on
wildland is a natural event.
(o) Wildland means an area in which human activity and development
is essentially non-existent, except for roads, railroads, power lines,
and similar transportation facilities. Structures, if any, are widely
scattered.
(p) High wind dust event is an event that includes the high-speed
wind and the dust that the wind entrains and transports to a monitoring
site.
(q) High wind threshold is the minimum wind speed capable of
causing particulate matter emissions from natural undisturbed lands in
the area affected by a high wind dust event.
(r) Federal land manager means, consistent with the definition in
40 CFR 51.301, the Secretary of the department with authority over the
Federal Class I area (or the Secretary's designee) or, with respect to
Roosevelt-Campobello International Park, the Chairman of the Roosevelt-
Campobello International Park Commission.
0
3. Amend Sec. 50.14, as amended on October 26, 2015, at 80 FR 65452,
effective December 28, 2015, as follows:
0
a. Revise paragraphs (a) and (b);
0
b. Revise paragraphs (c)(1), (c)(2)(i) through (v), and (c)(3).
The revisions read as follows:
Sec. 50.14 Treatment of air quality monitoring data influenced by
exceptional events.
(a) Requirements--(1) Scope. (i) This section applies to the
treatment of data showing exceedances or violations of any national
ambient air quality standard for purposes of the following types of
regulatory determinations by the Administrator:
(A) An action to designate an area, pursuant to Clean Air Act
section 107(d)(1), or redesignate an area, pursuant to Clean Air Act
section 107(d)(3), for a particular national ambient air quality
standard;
(B) The assignment or re-assignment of a classification category to
a nonattainment area where such classification is based on a comparison
of pollutant design values, calculated according to the specific data
handling procedures in 40 CFR part 50 for each national ambient air
quality standard, to the level of the relevant national ambient air
quality standard;
(C) A determination regarding whether a nonattainment area has
attained the level of the appropriate national ambient air quality
standard by its specified deadline;
(D) A determination that an area has had only one exceedance in the
year prior to its attainment deadline and thus qualifies for a 1-year
attainment date extension, if applicable; and
(E) A determination under Clean Air Act section 110(k)(5), if based
on an area violating a national ambient air quality standard, that the
state implementation plan is inadequate to the requirements of Clean
Air Act section 110.
(ii) A State, federal land manager or other federal agency may
request the Administrator to exclude data showing exceedances or
violations of any national ambient air quality standard that are
directly due to an exceptional event from use in determinations by
demonstrating to the Administrator's satisfaction that such event
caused a specific air pollution concentration at a particular air
quality monitoring location.
(A) For a federal land manager or other federal agency to be
eligible to initiate such a request for data exclusion, the federal
land manager or other federal agency must:
(1) Either operate a regulatory monitor that has been affected by
an exceptional event or manage land on which an exceptional event
occurred that influenced a monitored concentration at a regulatory
monitor; and
(2) Initiate such a request only after discussing such submittal
with the State in which the affected monitor is located; and
(B) When initiating such a request, all provisions in this section
that are expressed as requirements applying to a State shall, except as
noted, be requirements applying to the federal land manager or other
federal agency.
(2) A demonstration to justify data exclusion may include any
reliable and accurate data, but must specifically address the elements
in paragraphs (c)(3)(iv) and (v) of this section.
(b) Determinations by the Administrator--(1) Generally. The
Administrator shall exclude data from use in determinations of
exceedances and violations where a State demonstrates to the
Administrator's satisfaction that an exceptional event caused a
specific air pollution concentration in excess of one or more national
ambient air quality standards at a particular air quality monitoring
location and otherwise satisfies the requirements of this section.
(2) Fireworks displays. The Administrator shall exclude data from
use in determinations of exceedances and violations where a State
demonstrates to the Administrator's satisfaction that emissions from
fireworks displays caused a specific air pollution concentration in
excess of one or more national ambient air quality standards at a
particular air quality monitoring location and otherwise satisfies the
requirements of this section. Such data will be treated in the same
manner as exceptional events under this rule, provided a State
demonstrates that such use of fireworks is significantly integral to
traditional national, ethnic, or other cultural events including, but
not limited to, July Fourth celebrations that satisfy the requirements
of this section.
(3) Prescribed fires. (i) The Administrator shall exclude data from
use in determinations of exceedances and violations, where a State
demonstrates to the Administrator's satisfaction that emissions from
prescribed fires caused a specific air pollution concentration in
excess of one or more national ambient air quality standards at a
particular air quality monitoring location and otherwise satisfies the
requirements of this section.
(ii) In addressing the requirements set forth in paragraph
(c)(3)(iv)(D) of this section regarding the not reasonably controllable
or preventable criterion:
(A) With respect to the requirement that a prescribed fire be not
reasonably controllable, the State must either certify to the
Administrator that it has adopted and is implementing a smoke
management plan or the State must demonstrate that the burn manager
employed the generally applicable basic smoke management practices
identified in Table 2 to Sec. 50.14. To make the latter demonstration,
the State may rely on a statement or other documentation provided by
the burn manager that he or she employed those practices. If an
exceptional event occurs using the basic
[[Page 72895]]
smoke management practices approach, the State must undertake a review
of its approach to ensure public health is being protected.
(B) With respect to the requirement that a prescribed fire be not
reasonably preventable, provided the Administrator determines that
there is no compelling evidence to the contrary in the record, the
State may rely upon and reference a multi-year land or resource
management plan for a wildland area with a stated objective to
establish, restore and/or maintain a sustainable and resilient wildland
ecosystem and/or to preserve endangered or threatened species through a
program of prescribed fire, but also provided that the use of
prescribed fire in the area has not exceeded the frequency indicated in
that plan.
(iii) Provided the Administrator determines that there is no
compelling evidence to the contrary in the record, in addressing the
requirements set forth in paragraph (c)(3)(iv)(E) of this section
regarding the human activity unlikely to recur at a particular location
criterion for demonstrations involving prescribed fires on wildland,
the State must describe the actual frequency with which a burn was
conducted, but may rely upon and reference an assessment of the natural
fire return interval or the prescribed fire frequency needed to
establish, restore, and/or maintain a sustainable and resilient
wildland ecosystem contained in a multi-year land or resource
management plan with a stated objective to establish, restore, and/or
maintain a sustainable and resilient wildland ecosystem and/or to
preserve endangered or threatened species through a program of
prescribed fire.
Table 2 to Sec. 50.14--Summary of Basic Smoke Management Practices, Benefit Achieved With the BSMP, and When
It Is Applied Before, During or After Ignition of the Burn \a\
----------------------------------------------------------------------------------------------------------------
Benefit achieved with the When the BSMP is applied--before/during/
Basic smoke management practice BSMP after the burn
----------------------------------------------------------------------------------------------------------------
Evaluate Smoke Dispersion Conditions. Minimize smoke impacts....... Before, During, After.
Monitor Effects on Air Quality....... Be aware of where the smoke Before, During, After.
is going and degree it
impacts air quality.
Record-Keeping/Maintain a Burn/Smoke Retain information about the Before, During, After.
Journal. weather, burn and smoke. If
air quality problems occur,
documentation helps analyze
and address air regulatory
issues.
Communication--Public Notification... Notify neighbors and those Before, During.
potentially impacted by
smoke, especially sensitive
receptors.
Consider Emission Reduction Reducing emissions through Before, During, After.
Techniques. mechanisms such as reducing
fuel loading can reduce
downwind impacts.
Share the Airshed--Coordination of Coordinate multiple burns in Before, During, After.
Area Burning. the area to manage exposure
of the public to smoke.
----------------------------------------------------------------------------------------------------------------
\a\ Elements of these BSMP could also be practical and beneficial to apply to wildfires for areas likely to
experience recurring wildfires.
(4) Wildfires. The Administrator shall exclude data from use in
determinations of exceedances and violations where a State demonstrates
to the Administrator's satisfaction that emissions from wildfires
caused a specific air pollution concentration in excess of one or more
national ambient air quality standard at a particular air quality
monitoring location and otherwise satisfies the requirements of this
section. Provided the Administrator determines that there is no
compelling evidence to the contrary in the record, the Administrator
will determine every wildfire occurring predominantly on wildland to
have met the requirements identified in paragraph (c)(3)(iv)(D) of this
section regarding the not reasonably controllable or preventable
criterion.
(5) High wind dust events. (i) The Administrator shall exclude data
from use in determinations of exceedances and violations, where a State
demonstrates to the Administrator's satisfaction that emissions from a
high wind dust event caused a specific air pollution concentration in
excess of one or more national ambient air quality standards at a
particular air quality monitoring location and otherwise satisfies the
requirements of this section provided that such emissions are from high
wind dust events.
(ii) The Administrator will consider high wind dust events to be
natural events in cases where windblown dust is entirely from
undisturbed natural lands or where all anthropogenic sources are
reasonably controlled as determined in accordance with paragraph (b)(7)
of this section.
(iii) The Administrator will accept a high wind threshold of a
sustained wind of 25 mph for areas in the States of Arizona,
California, Colorado, Kansas, Nebraska, Nevada, New Mexico, North
Dakota, Oklahoma, South Dakota, Texas, Utah, and Wyoming provided this
value is not contradicted by evidence in the record at the time the
State submits a demonstration.
(iv) In addressing the requirements set forth in paragraph
(c)(3)(iv)(D) of this section regarding the not reasonably preventable
criterion, the State shall not be required to provide a case-specific
justification for a high wind dust event.
(v) With respect to the not reasonably controllable criterion of
paragraph (c)(3)(iv)(D) of this section, dust controls on an
anthropogenic source shall be considered reasonable in any case in
which the controls render the anthropogenic source as resistant to high
winds as a natural undisturbed land area. The Administrator may
determine lesser controls reasonable on a case-by-case basis.
(vi) For remote, large-scale, high-energy and/or sudden high wind
dust events, such as ``haboobs'' in the southwest, the Administrator
will generally consider a demonstration documenting the nature and
extent of the event to be sufficient with respect to the not reasonable
controllable criterion of paragraph (c)(3)(iv)(D) of this section.
(6) Determinations with respect to event aggregation and multiple
national ambient air quality standards for the same pollutant. (i)
Where a State demonstrates to the Administrator's satisfaction that for
national ambient air quality standards with averaging or cumulative
periods longer than 24-hours the aggregate effect of events occurring
on different days has caused an exceedance or violation, the
Administrator shall determine such collective data to satisfy the
requirements in paragraph (c)(3)(iv)(B) of this section regarding the
clear causal relationship criterion and otherwise satisfies the
requirements of this section.
[[Page 72896]]
(ii) The Administrator shall accept as part of a demonstration for
the clear causal relationship in paragraph (c)(3)(iv)(B) of this
section, a State's comparison of a 24-hour concentration of any
national ambient air quality standard pollutant to the level of a
national ambient air quality standard for the same pollutant with a
longer averaging period.
(7) Determinations with respect to the not reasonably controllable
or preventable criterion. (i) The Administrator shall determine that an
event is not reasonably preventable if the State shows that reasonable
measures to prevent the event were applied at the time of the event.
(ii) The Administrator shall determine that an event is not
reasonably controllable if the State shows that reasonable measures to
control the impact of the event on air quality were applied at the time
of the event.
(iii) The Administrator shall assess the reasonableness of
available controls for anthropogenic sources based on information
available as of the date of the event.
(iv) Except where a State is obligated to revise its state
implementation plan, the Administrator shall consider enforceable
control measures implemented in accordance with a state implementation
plan, approved by the EPA within 5 years of the date of a demonstration
submittal, that address the event-related pollutant and all sources
necessary to fulfill the requirements of the Clean Air Act for the
state implementation plan to be reasonable controls with respect to all
anthropogenic sources that have or may have contributed to event-
related emissions.
(v) The Administrator shall not require a State to provide case-
specific justification to support the not reasonably controllable or
preventable criterion for emissions-generating activity that occurs
outside of the State's jurisdictional boundaries within which the
concentration at issue was monitored. In the case of a tribe with
treatment as a state status with respect to exceptional events
requirements, the tribe's jurisdictional boundaries for purposes of
requiring or directly implementing emission controls apply. In the case
of a federal land manager or other federal agency submitting a
demonstration under the requirements of this section, the
jurisdictional boundaries that apply are those of the State or the
tribe depending on which has jurisdiction over the area where the event
has occurred.
(c) Schedules and procedures--(1) Public notification. (i) All
States and, where applicable, their political subdivisions must notify
the public promptly whenever an event occurs or is reasonably
anticipated to occur which may result in the exceedance of an
applicable air quality standard.
(ii) [Reserved]
(2) Initial notification of potential exceptional event. (i) A
State shall notify the Administrator of its intent to request exclusion
of one or more measured exceedances of an applicable national ambient
air quality standard as being due to an exceptional event by creating
an initial event description and flagging the associated data that have
been submitted to the AQS database and by engaging in the Initial
Notification of Potential Exceptional Event process as follows:
(A) The State and the appropriate EPA regional office shall engage
in regular communications to identify those data that have been
potentially influenced by an exceptional event, to determine whether
the identified data may affect a regulatory determination and to
discuss whether the State should develop and submit an exceptional
events demonstration according to the requirements in this section;
(B) For data that may affect an anticipated regulatory
determination or where circumstances otherwise compel the Administrator
to prioritize the resulting demonstration, the Administrator shall
respond to a State's Initial Notification of Potential Exceptional
Event with a due date for demonstration submittal that considers the
nature of the event and the anticipated timing of the associated
regulatory decision;
(C) The Administrator may waive the Initial Notification of
Potential Exceptional Event process on a case-by-case basis.
(ii) The data shall not be excluded from determinations with
respect to exceedances or violations of the national ambient air
quality standards unless and until, following the State's submittal of
its demonstration pursuant to paragraph (c)(3) of this section and the
Administrator's review, the Administrator notifies the State of its
concurrence by placing a concurrence flag in the appropriate field for
the data record in the AQS database.
(iii) [Reserved]
(iv) [Reserved]
(v) [Reserved]
* * * * *
(3) Submission of demonstrations. (i) Except as allowed under
paragraph (c)(2)(vi) of this section, a State that has flagged data as
being due to an exceptional event and is requesting exclusion of the
affected measurement data shall, after notice and opportunity for
public comment, submit a demonstration to justify data exclusion to the
Administrator according to the schedule established under paragraph
(c)(2)(i)(B).
(ii) [Reserved]
(iii) [Reserved]
(iv) The demonstration to justify data exclusion must include:
(A) A narrative conceptual model that describes the event(s)
causing the exceedance or violation and a discussion of how emissions
from the event(s) led to the exceedance or violation at the affected
monitor(s);
(B) A demonstration that the event affected air quality in such a
way that there exists a clear causal relationship between the specific
event and the monitored exceedance or violation;
(C) Analyses identified in Table 3 to Sec. 50.14 comparing the
claimed event-influenced concentration(s) to concentrations at the same
monitoring site at other times consistent with Table 3 to Sec. 50.14
to support the requirement at paragraph (c)(3)(iv)(B) of this section.
The Administrator shall not require a State to prove a specific
percentile point in the distribution of data;
(D) A demonstration that the event was both not reasonably
controllable and not reasonably preventable; and
(E) A demonstration that the event was a human activity that is
unlikely to recur at a particular location or was a natural event.
(v) With the submission of the demonstration containing the
elements in paragraph (c)(3)(iv) of this section, the State must:
(A) Document that the public comment process was followed and that
the comment period was open for a minimum of 30 days, which could be
concurrent with the Administrator's review of the associated
demonstration provided the State can meet all requirements in this
paragraph;
(B) Submit the public comments it received along with its
demonstration to the Administrator; and
(C) Address in the submission to the Administrator those comments
disputing or contradicting factual evidence provided in the
demonstration.
(vi) Where the State has submitted a demonstration according to the
requirements of this section and the Administrator has reviewed such
demonstration and requested additional evidence to support one of the
elements in paragraph (c)(3)(iv) of this section, the State shall have
12 months from the date of the Administrator's request to submit such
evidence. At the
[[Page 72897]]
conclusion of this time, if the State has not submitted the requested
additional evidence, the Administrator will consider the demonstration
to be inactive and will not pursue additional review of the
demonstration. After a 12-month period of inactivity, if a State
desires to pursue the inactive demonstration, it must reinitiate its
request to exclude associated data by following the process beginning
with paragraph (c)(2)(i) of this section.
Table 3 to Sec. 50.14. Evidence and Analyses for the Comparison to Historical Concentrations
----------------------------------------------------------------------------------------------------------------
Historical concentration evidence Types of analyses/supporting information Required or optional?
----------------------------------------------------------------------------------------------------------------
1. Comparison of concentrations on the Seasonal (appropriate if exceedances occur Required seasonal and/or
claimed event day with past historical primarily in one season, but not in annual analysis
data. others). (depending on which is
Use all available seasonal data more appropriate).
over the previous 5 years (or more, if
available).
Discuss the seasonal nature of
pollution for the location being
evaluated.
Present monthly maximums of the
NAAQS relevant metric (e.g., maximum
daily 8-hour average ozone or 1-hr SO2)
vs monthly or other averaged daily data
as this masks high values.
Annual (appropriate if exceedances are
likely throughout the year).
Use all available data over the
previous 5 years (or more, if available).
Seasonal and Annual Analyses..............
Provide the data in the form
relevant to the standard being considered
for data exclusion.
Label ``high'' data points as
being associated with concurred
exceptional events, suspected exceptional
events, other unusual occurrences, or
high pollution days due to normal
emissions.
Describe how emission control
strategies have decreased pollutant
concentrations over the 5-year window, if
applicable.
Include comparisons omitting
known or suspected exceptional events
points, if applicable.
2. Comparison of concentrations on the Include neighboring days at the Optional analysis.
claimed event day with a narrower set same location (e.g., a time series of two
of similar days. to three weeks) and/or other days with
similar meteorological conditions
(possibly from other years) at the same
or nearby locations with similar
historical air quality along with a
discussion of the meteorological
conditions during the same timeframe. \a\
Use this comparison to
demonstrate that the event caused higher
concentrations than would be expected for
given meteorological and/or local
emissions conditions.
3. Percentile rank of concentration when Provide the percentile rank of Required analysis when
compared to annual data. \b\ the event-day concentration relative to comparison is made on an
all measurement days over the previous 5 annual basis (see item
years to ensure statistical robustness #1).
and capture non-event variability over
the appropriate seasons or number of
years.\c\
Use the daily statistic (e.g., 24-
hour average, maximum daily 8-hour
average, or maximum 1-hour) appropriate
for the form of the standard being
considered for data exclusion.
4. Percentile rank of concentration Provide the percentile rank of Required analysis when
relative to seasonal data. \b\ the event-day concentration relative to comparison is made on a
all measurement days for the season (or seasonal basis (see item
appropriate alternative 3-month period) #1).
of the event over the previous 5 years.
Use the same time horizon as used
for the percentile rank calculated
relative to annual data, if appropriate.
----------------------------------------------------------------------------------------------------------------
\a\ If an air agency compares the concentration on the claimed event day with days with similar meteorological
conditions from other years, the agency should also verify and provide evidence that the area has not
experienced significant changes in wind patterns, and that no significant sources in the area have had
significant changes in their emissions of the pollutant of concern.
\b\ The EPA does not intend to identify a particular historical percentile rank point in the seasonal or annual
historical data that plays a critical role in the analysis or conclusion regarding the clear causal
relationship.
\c\ Section 8.4.2.e of appendix W (proposed revisions at 80 FR 45374, July 29, 2015) recommends using 5 years of
adequately representative meteorology data from the National Weather Service to ensure that worst-case
meteorological conditions are represented. Similarly, for exceptional events purposes, the EPA believes that 5
years of ambient air data, whether seasonal or annual, better represent the range of ``normal'' air quality
than do shorter periods.
[FR Doc. 2015-29350 Filed 11-19-15; 8:45 am]
BILLING CODE 6560-50-P