circumstances, can be considered exceptional events. The preamble to
the 2007 Exceptional Events Rule, however, used unclear or undefined
fire-related terminology, making the preparation of some fire-related
demonstrations particularly challenging. Recognizing some of these
unique challenges associated with fires on wildland, we proposed a
number of fire-related revisions to the Exceptional Events Rule for
wildfires and prescribed fires that occur on wildland.\57\
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    \57\ While we proposed, and are finalizing, provisions only for
fires that occur predominantly on wildland, we did not intend to
restrict wildfires on other types of land from receiving similar
treatment as wildfires on wildland. 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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    These revisions included proposed regulatory language for certain
fire-related definitions, clarification and associated regulatory text
related to using SMP and BSMP to satisfy exceptional events
demonstration and program implementation elements, and new Exceptional
Events Rule provisions to specifically address prescribed fire
exceptional events issues. We provide additional detail in the separate
sections on wildfires (Section IV.F.2.a of this preamble) and
prescribed fire (Section IV.F.2.b of this preamble).
    As we implement the changes we are promulgating in this regulatory
action,

we remain committed to working with federal, state, local, tribal and
private land owners/land managers and state, tribal and local air
quality agencies to effectively manage prescribed fire use to reduce
the impact of catastrophic wildfire-related emissions on ozone,
PM10 and PM2.5.
a. Wildfires
    Summary of Proposal. The EPA proposed the following guidance,
clarifications and rule revisions to assist air agencies preparing
exceptional events demonstrations for wildfires.
    (i) Definition of wildland and wildfire. The EPA proposed to codify
in regulatory language the definition of ``wildland'' by using the
October 2014 National Wildfire Coordinating Group (NWCG) Glossary of
Wildland Fire Terminology \58\ 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 noted in the
proposal, wildland can include forestland,\59\ shrubland,\60\ grassland
\61\ and wetlands.\62\ This proposed definition of wildland includes
lands that are predominantly wildland, such as land in the wildland-
urban interface.63 64
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    \58\ National Wildfire Coordinating Group. Glossary of Wildland
Fire Terminology, PMS 205. October 2014. We are retaining our
proposed definition of the wildland although the NWCG has revised
its October 2014 glossary. The October 2015 glossary, which became
available after the November 2015 exceptional events proposal, is
available at http://www.nwcg.gov/glossary-of-wildland-fire-terminology.
    \59\ 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/glossary.
    \60\ Shrubland is land on which the vegetation is dominated by
shrubs. Definition available at https://globalrangelands.org/glossary/.
    \61\ Grassland is land on which the vegetation is dominated by
grasses, grass like plants, and/or forbs. This definition has
changed since the EPA proposed the definition of grassland. We are
retaining the proposed definition. The current Global Rangelands
definition is available at https://globalrangelands.org/glossary.
    \62\ 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.
    \63\ 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. We are
retaining our proposed definition of the wildland and our proposed
description of the wildland-urban interface although the NWCG has
revised its October 2014 glossary. The October 2015 glossary, which
became available after the November 2015 exceptional events
proposal, is available at http://www.nwcg.gov/glossary-of-wildland-fire-terminology.
    \64\ 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
document. We do not expect a small prescribed fire in an interface
area (e.g., a prescribed fire ignited by a single landowner on his/
her personal property) to generate emissions that would raise
exceptional events issues.
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    The proposed definition for wildland considered the types of human
intervention that could affect whether a land is considered a
``wildland'' and stated that the presence of fences to limit the
movement of grazing animals, or of infrastructure to provide water to
grazing animals, would not prevent a land area from being wildland. The
proposal further clarified that 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 and 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. The proposed rule
indicated that managed timberlands \65\ could be considered wildland if
they have a complex ecosystem affected by only limited human entrance
and intervention. We invited comment on incorporating these examples of
land use types into the regulatory definition of wildland.
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    \65\ Timberland is land on which the natural potential
vegetation is forest. It may be managed primarily for the production
and harvest of timber. Definition available at https://globalrangelands.org/glossary/.
---------------------------------------------------------------------------

    We also proposed in regulatory text, the following definition of
``wildfire,'' 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.''
    (ii) Not reasonably controllable or preventable. As proposed and as
with other natural events, the ``not reasonably controllable or
preventable'' criterion applies to wildfires. The proposed rule
articulated that 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/wildfire responders to
support a position that such efforts were reasonable. The EPA therefore
proposed in regulatory language a rebuttable presumption that every
wildfire on wildland satisfies the ``not reasonably controllable or
preventable'' criterion unless evidence in the record demonstrates
otherwise and that satisfying this criterion for wildfires on wildland
would involve referencing the appropriate regulatory citation in the
demonstration. The proposal further indicated that in situations in
which a fire manager could have suppressed or contained a wildfire but
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, that we would expect the
fire manager to employ appropriate BSMP as described in Section
IV.F.2.b of this preamble when possible.
    (iii) Coordinated communications. As stated in the proposal,
regardless of the 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.\66\ 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.\67\ Fuel load minimization steps can consist of
both prescribed fire and mechanical treatments, such as using
mechanical equipment to reduce accumulated understory.
---------------------------------------------------------------------------

    \66\ 72 FR 13575 (March 22, 2007).
    \67\ 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 in the docket for this action (see EPA-HQ-
OAR-2013-0572, Wildland Fire Air Quality Response Program).
---------------------------------------------------------------------------

    Final Rule. We are finalizing, as proposed, for the reasons
discussed in our proposal and herein, and as supported by several
commenters, the following definition of wildland: ``Wildland means an
area in which human activity and development are essentially non-
existent, except for roads, railroads, power lines, and similar
transportation facilities. Structures, if any, are widely scattered.''
In finalizing this definition, we are retaining, as guidance, the
proposed examples of land use types and types of human intervention
that are considered wildland (or not) in the preamble of this final
rule. Many commenters supported this approach while others preferred
incorporating land use types and specifically allowable types of
structures (e.g., fences to limit the movement of grazing animals) into
the regulatory definition. We have determined that because the
presented land use types and clarifications regarding allowable
structures and human intervention are only examples, and not an all-
inclusive list of all lands that could be considered ``wildland,''
guidance is more appropriate for these details than rule. We also
clarify, at the request of one commenter, that we would generally
consider lands like state and national parks and wildlife refuges
(provided they are primarily wild and natural and provided hunting, if
allowed, is limited) to be wildland. We are not including the
modifications suggested by several commenters that would change the
phrase ``development is essentially non-existent'' to ``development is
limited in scope.'' First, the language ``limited in scope'' in the
phrase ``development is limited in scope'' is subjective and would
create additional uncertainty and ambiguity, which is not intended in
this action. Additionally, when considering the term ``wildland,'' the
word ``wild,'' by definition, implies a natural, uncultivated or
uninhabited region. Conversely, ``development'' implies growth,
construction and, potentially, groupings of buildings. Modifying the
definition as proposed by the commenters could be interpreted to mean
that parcels of land with some empty space between groupings of
buildings (e.g., cultivated and inhabited areas) could be wildland.
This is not our intent. Another commenter suggested that because
``wild'' implies minimal ongoing ecological impacts from human activity
and not an infrequent presence of humans and their structures that we
change the regulatory definition to ``wildland means an area where the
impact on the ecosystem from human development and agriculture is
essentially nonexistent, except for widely separated roads, railroads
and power lines.'' While we agree with the commenter's perspective
regarding very limited human impact on the ecosystem, we believe that
the definition we are promulgating conveys similar intent and will have
the same practical effect.
    Also related to the definition of wildland, several states asked
that we specifically address prescribed fires on cultivated cropland
and other agricultural lands. As we proposed and as we are finalizing
in this rule, the fire-related provisions apply specifically to fires
that occur predominantly on wildland. Air agencies contemplating
preparing fire-related exceptional events demonstrations for fires not
on wildland, should consult with their reviewing EPA Regional office.
The EPA will review submitted demonstrations on a case-by-case basis
considering the specific merits of each event.
    Comments and Responses. After consideration of the public comments,
we are finalizing a modified version of our proposed definition of
wildfire: ``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 developed into a wildfire. A wildfire that predominantly
occurs on wildland is a natural event.'' The final revised definition
includes ``a prescribed fire that has developed into a wildfire''
instead of the proposed language ``a prescribed fire that has been
declared to be a wildfire.''
    Some commenters supported the original proposed definition, but
others recommended deleting the phrase ``a prescribed fire that has
been declared to be a wildfire'' from the definition because they
disagree with allowing burners to ``declare'' a prescribed fire to be a
wildfire. Commenters noted that burn managers might make such a
declaration for reasons other than their unanticipated inability to
control the deliberately ignited fire. We note that the proposed
definition of wildfire did not require that the objective be to put out
such a fire for it to meet the definition. When an unplanned fire on
wildland does not threaten catastrophic consequences (e.g.,
consequences to public health, safety or property) and when the
wildfire is burning on land that would otherwise be identified for
ecosystem management (e.g., fuels management through prescribed
burning), it may be appropriate to allow the fire to continue burning
under managed conditions. This fire management scenario was not our
intended focus in proposing the ``declaration'' language. Rather, as
stated in the proposal, ``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 an unplanned way such
that its management challenges are essentially the same as if it were a
wildfire. The federal, state and tribal wildland fire management
community uses the terminology ``prescribed fire declared wildfire'' to
describe the infrequent and significant instances when meteorological
and/or other environmental conditions, resource availability, or other
unforeseen circumstances lead the burn manager to make such a
declaration to protect the health and safety of fire management staff
and the public. For example, if the prescribed fire has escaped secure
containment lines and requires suppression along all or part of its
boundary or if it no longer meets the resource objectives (e.g., smoke
impact, flame height). It was not our intention to allow categorical
re-definition of some types of prescribed fire to be wildfires. Our
intent was to clearly identify those fires that could be considered
wildfires and those that would be considered prescribed fires. In doing
this, we also identified the applicable demonstration requirements
under the Exceptional Events Rule. That is, wildfires and prescribed
fires on wildland have different requirements for exceptional events
demonstrations based on the practicality of prevention/control (i.e.,
the approach to addressing the not reasonably controllable or
preventable criterion) and on the natural versus anthropogenic origin
of the fire (i.e., the human activity that is unlikely

to recur or a natural event). When considering prevention/control for
purposes of exceptional event categorization, a prescribed fire
effectively becomes like a wildfire when, for example, the prescribed
fire escapes secure containment due to unforeseen circumstances (e.g.,
a sudden shift in prevailing winds). In these instances, the burn
manager would no longer control the path of the fire. Thus, the fact
that the initial fire was deliberately ignited should not result in the
entire burn (e.g., the duration and extent of the burn) needing to
follow the rule requirements for prescribed fires on wildland. Given
these potential circumstances, we proposed to rely on the burn
manager's (or another individual familiar with the circumstances of the
fire) declaration that the prescribed fire has become a wildfire.
Because many commenters expressed concern with the ``declaration''
language, we have changed the phrase to ``a prescribed fire that has
developed into a wildfire,'' by which we mean that has developed in an
unplanned way such that its management challenges are essentially the
same as if it had been initiated by an unplanned ignition.'' We believe
that this revised language conveys our original intent. In showing that
a prescribed fire ``hasdeveloped into a wildfire,'' air agencies should
include the following documentation when addressing the ``human
activity unlikely to recur at a particular location or a natural
event'' criterion in their demonstration: (1) News reports or
notifications to the public characterizing the nature of the fire and
(2) the demonstration submitter's explanation of the origin and
evolution of the fire.
    All commenters providing feedback on the EPA's proposal to grant a
rebuttable presumption that every wildfire on wildland satisfies the
``not reasonably controllable or preventable'' criterion unless
evidence in the record demonstrates otherwise agreed with the EPA's
proposed regulatory language. We have therefore finalized the provision
at 40 CFR 50.14(b)(4) that 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 . . . regarding the not reasonably
controllable or preventable criterion.''
b. Prescribed Fires
    The proposal stated, and this final rule repeats, the EPA's
recognition that use of prescribed fire on wildland can influence the
occurrence, severity, behavior and effects of catastrophic wildfires
and 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 \68\ that federal, state, local, tribal
and private land owners/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 catastrophic wildfires to the public.
---------------------------------------------------------------------------

    \68\ 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.
---------------------------------------------------------------------------

    Summary of Proposal. The EPA proposed the following guidance,
clarifications and rule revisions to assist air agencies preparing
exceptional events demonstrations for prescribed fire on wildland.
    (i) Definition of a prescribed fire. We proposed to adopt in rule
language a modified version of the then-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 land or resource management objectives.''
In this definition, ``management'' refers to the owner or manager of
the land area to which prescribed fire is applied. The proposal
replaced the original NWCG language ``specific objectives'' with
``specific land or resource management objectives.''
    (ii) Events caused by human activity. We proposed regulatory
language stating that prescribed fires are events caused by human
activity and, therefore, 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. The proposed rule
set forth generally applicable guidelines to clarify both ``unlikely to
recur'' and ``at a particular location.'' In this action, we discussed
these guidelines for most events caused by human activity in Section
IV.E.1 of this preamble, but we also clarified that specific approaches
apply for prescribed fires on wildland, which we discuss here.
    Our proposed rule indicated that when characterizing the ``human
activity that is unlikely to recur at a particular location''
criterion, a demonstration for a prescribed fire on wildland could use
one of two benchmarks to describe the expected frequency of prescribed
fires on wildland: \69\ (1) The natural fire return interval as
articulated in the 2007 preamble or (2) the prescribed fire frequency
needed to establish, restore and/or maintain a sustainable and
resilient wildland ecosystem. The proposal also stated that multi-year
land or resource management plans prepared by the land management
agency or any private property owner generally include documentation of
these established fire intervals. Considering these two concepts, we
proposed rule text that considered a demonstration's referencing of a
multi-year land or resource management plan \70\ (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. The proposal noted that referencing 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 can
also satisfy the ``unlikely to recur at a particular location''
criterion.
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    \69\ The EPA will assess benchmarks for the expected frequency
of prescribed fires not on wildland on a case-by-case basis.
    \70\ These plans could also include fire management plans,
prescribed fire on wildland management plans, landscape management
plans or equivalent public planning documents.
---------------------------------------------------------------------------

    (iv) Not reasonably controllable or preventable. The proposed rule
stated that, consistent with current practice and 2007 preamble and
rule language, the EPA considers it appropriate for air agencies to
rely on an in-place and implemented state-certified SMP or 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. We also proposed that,
provided there is no compelling evidence to the contrary in the record,
an air agency could rely upon, comply with 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 to satisfy the
preventability prong of the ``not reasonably controllable or
preventable'' criterion. We provide further context from our proposed
action in the paragraphs that follow.
    Because the 2007 Exceptional Events Rule used the terms SMP and
BSMP without defining them, our proposed rule provided clarity. With
respect to a SMP, the proposal noted that 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. We also
indicated that ``certification'' requires that a responsible state or
delegated local agency certify in a letter to the Administrator of the
EPA, or a Regional Administrator, that it has adopted and is
implementing a SMP. We solicited comment on incorporating these SMP
elements into rule text language.
    The proposal continued the discussion of SMP by noting that states
with certified SMP 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.
For these reasons, the EPA proposed to accept the testimony of the air
agency submitting the 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.
    The proposed rule provided similar detail for BSMP by identifying
in the rule text six BSMP as being generally appropriate, and generally
endorsed and followed by federal, state and local agencies and private
landowners, for exceptional events purposes for prescribed fires on
wildland as well as for other prescribed fires. The six BSMP (i.e.,
evaluating smoke dispersion conditions, monitoring effects on air
quality, recordkeeping/maintaining a burn or smoke journal,
communicating, considering emission reduction techniques, and sharing
the airshed) came from guidance on BSMP for prescribed fires provided
by the USDA Forest Service and USDA NRCS.\71\ The proposal noted that
while the BSMP are broadly stated, burn managers use site-specific
considerations to select the exact actions of each type and apply them
to specific burn projects. The EPA proposed to accept as evidence of
the use of BSMP the burn manager's statement that he or she employed
applicable BSMP for a prescribed fire. The proposal noted that
documentation of evidence could consist of a copy of the routine post-
burn report or a letter prepared by the burn manager. While the EPA
asserted in the proposal that we would work collaboratively with other
federal agencies to make post-burn reports available to the air
agencies that need them, we also encouraged land managers and other
organizations employing prescribed fire to work with states and tribes
to develop an efficient process to coordinate fire planning activities,
issue public health advisories, if needed, and share relevant fire-
related documentation, including pre-and post-burn reports.
---------------------------------------------------------------------------

    \71\ 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.
---------------------------------------------------------------------------

    The proposal provided similar detail with respect to addressing the
``prevention'' prong of the ``not reasonably controllable or
preventable'' criterion stating that because prescribed fires are
intentionally ignited, clarifying preventability is particularly
relevant. The proposal noted that because both SMP and BSMP generally
apply to the planning, execution and follow-up once the decision has
been made to ignite a burn, they, therefore, do not specifically
address prevention or deciding not to burn. The proposal stated that an
affected agency should conclude a prescribed fire to be not reasonably
preventable based on the benefits that would be foregone if the fire
were not conducted. We articulated ``forgone benefits'' as those
objectives in a multi-year fire management plan that establish, restore
and/or maintain a sustainable and resilient wildland ecosystem. The
proposed regulatory text intended to rely on the benefits in these
plans as satisfying the not reasonably preventable prong of the not
reasonably controllable or preventable criterion provided there is no
compelling evidence to the contrary in the record when the EPA approves
the associated exceptional events demonstration. The proposal provided
additional detail regarding the development of these multi-year land or
resource management plans.
    The proposal also removed 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 in the 2007 Exceptional Events
Rule read, ``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.''
    Final Rule. We are finalizing in regulatory language, as proposed
and for the reasons discussed in our proposal and herein, the following
definition of prescribed fire: A ``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.''
    We are also finalizing our proposal that a prescribed fire can
satisfy the human activity unlikely to recur at a particular location
criterion if certain requirements are met and provided there is no
compelling evidence to the contrary in the record. Specifically, the
air agency must describe the actual burn frequency, but may rely on
either 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 \72\ 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. As we noted in the proposal, 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. We also recognize 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.
Thus, we acknowledge that a multi-year 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 may
include general targets for the frequency of prescribed fire use and
that management may deviate from the general plan due to unexpected
differences between planned and actual fire behavior, landscape or
ecosystem characteristics, fuel loading patterns and weather patterns.
As a result, 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, provided, of course, that
the demonstration met all other Exceptional Events Rule criteria. Also,
as we discussed in more detail in the proposal and consistent with our
recognition of the ecosystem benefits of prescribed fire, ``sustainable
and resilient wildland ecosystem'' could include maintaining a
regenerated forest in a healthy condition able to withstand and/or
diminish the effects of catastrophic wildfire.
---------------------------------------------------------------------------

    \72\ 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.
---------------------------------------------------------------------------

    We are finalizing our proposed regulatory language that a
prescribed fire must be conducted under an adopted and implemented
certified SMP or must have used appropriate BSMP to satisfy the
controllable prong of the not reasonably controllable or preventable
criterion. As we indicated in the proposal, ``certification'' requires
that a responsible state or delegated local agency certify in a letter
to the Administrator of the EPA, or a Regional Administrator,\73\ that
it has adopted and is implementing a SMP.\74\ Past certifications
provided to the EPA through this process are sufficient to meet the
``certified'' SMP language in this final action. An air agency with a
current SMP that has not been certified according to this process could
pursue certification of its existing SMP. SMPs that have been
incorporated into a SIP are ``certified.'' We are retaining Table 3,
which identifies generally appropriate BSMP, in the regulatory text. To
the proposed version of the table, we have added a footnote to indicate
that the listing of BSMP is not intended to be all-inclusive. Burn
managers can consider other appropriate BSMP as they become available
due to technological advancement or programmatic refinement. While not
in regulatory text, we also incorporate into this final rule preamble,
as guidance, Table 4, which includes example content for a burn report.
The preamble to this final rule identifies burn reports as one example
of documentation that air agencies can use in their exceptional events
demonstrations for prescribed fires to show the implementation of BSMP.
After incorporating commenter feedback into the descriptions of some of
these components, we are retaining in the preamble, as guidance, the
following components of a certified SMP: \75\
---------------------------------------------------------------------------

    \73\ As discussed in more detail in Section IV.G.7 of this
preamble, concurrent with these rule revisions, the EPA has revised
the delegation of authority for exceptional events decision making
to allow for redelegation from the EPA Regional Administrator to the
Regional Air Division Director or equivalent highest manager who
exclusively oversees air programs. If an EPA Regional office elects
to pursue redelegation, then a state could ``certify'' its SMP by
sending a letter to the delegated official in the EPA Regional
office.
    \74\ 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.
    \75\ The EPA is adapting the language associated with the six
basic components of a certifiable SMP from the 1998 Interim Air
Quality Policy on Wildland and Prescribed Fires. Although states may
have developed and implemented a certified SMP that addresses
prescribed fire not on wildland, this regulatory action focuses on
the elements of a certified SMP as applied to managing smoke from
prescribed fires on wildland. In this context, the EPA expects burn
managers to consider actions and approaches where appropriate.
---------------------------------------------------------------------------

     Authorization to Burn--Includes a process for authorizing
or granting approval to manage prescribed fires on wildland within a
region, state or on Indian lands and identifies a central authority
responsible for implementing the program. The authorization process
could, but is not required to, include burn permits or other forms of
instruction for conducting burns that consider air quality and the
ability of the airshed to disperse emissions.
     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 appropriate
emission reduction techniques.
     Smoke Management Components of Burn Plans--If the smoke
management program requires burn plans, then the burn plan should
include the following components: Actions to minimize fire emissions,
approaches to 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 compliance with the terms of the SMP.
     Program Evaluation--Provides for periodic review by
interested stakeholders of the SMP effectiveness and program revision
as necessary. A review of effectiveness should consider the role of
prescribed fire in meeting the goals in a multi-year 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. Effectiveness reviews should
also consider air quality impacts as well as any received post-burn
reports, which may describe implemented contingency plans due to smoke
impacts or use of BSMP and recommendations for future improvements. SMP
procedures for re-evaluation should address a frequency of review
(e.g., every 3 to 5 years, or as needed); participants in the review
process (e.g., original program developers to include land owners/
managers, air quality managers, the public, etc.); and program
objectives over the review period (e.g., acres burned, anticipated/
desired future acres burned, needed modifications).

 Table 3--Summary of Basic Smoke Management Practices, Benefit Achieved
                With the BSMP, and When It Is Applied \a\
------------------------------------------------------------------------
                                                        When the BSMP is
    Basic smoke management      Benefit achieved with   applied--before/
         practice \b\                  the BSMP         during/after the
                                                              burn
------------------------------------------------------------------------
Evaluate Smoke Dispersion       Minimize smoke         Before, During,
 Conditions.                     impacts.               After.
Monitor Effects on Air Quality  Be aware of where the  Before, During,
                                 smoke is going and     After.
                                 degree it impacts
                                 air quality.
Record-Keeping/Maintain a Burn/ Retain information     Before, During,
 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 Burning.   burns in the area to   After.
                                 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.
\b\ The listing of BSMP in this table is not intended to be all-
  inclusive. Not all BSMP are appropriate for all burns. Goals for
  applicability should retain flexibility to allow for onsite variation
  and site-specific conditions that can be variable on the day of the
  burn. Burn managers can consider other appropriate BSMP as they become
  available due to technological advancement or programmatic refinement.

   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.....................  Include...........  Include.
Permit number (if appropriate)..  Include...........  Include.
Latitude/longitude and physical   Include...........  Include.
 description.
Date of burn, ignition time and   Include...........  Include.
 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           Actual conditions
 conditions, wind speed and        conditions          (including actual
 direction, dispersion).           (including          dispersion).
                                   predicted
                                   dispersion).
Smoke Impacts...................  Anticipated smoke   Observed or
                                   impacts.            reported smoke
                                                       impacts (include
                                                       nature, duration,
                                                       spatial extent
                                                       and copies of
                                                       received
                                                       complaints).
BSMP actions to reduce impacts..  Expected BSMP       Actual BSMP
                                   actions.            actions.
Recommendations for future burns  ..................  Include.
 in similar areas.
Analytics (modeled/actual fire    ..................  Include.
 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, state, and date in which the burn occurred (e.g., County
  X, State Y Prescribed Fire on Date Z) if no other name has been
  assigned.

    Also as proposed, and for the previously summarized reasons, we are
removing the phrase ``and must include consideration of development of
a SMP'' from the sentence that in 40 CFR 50.14(b)(3) of the 2007
Exceptional Events Rule that read, ``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.''
    With respect to the not reasonably preventable prong of the not
reasonably controllable or preventable criterion, after considering
public comments, we are finalizing our reliance on 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.
    While our proposal encouraged all agencies and managers/owners
involved in land, air quality and fire management to communicate and
collaborate regarding fire use practices in general and plans for
specific prescribed fires with use of BSMP, we did not propose to
require this communication. Commenters provided both general and
specific feedback related to the EPA's encouragement of these
collaborative fire communications. From a holistic perspective,
commenters noted that a shared understanding regarding the goals of a
specific prescribed fire helps both air quality and land managers meet
their respective air quality objectives and land and resource
management objectives. Some state and regional planning organization
commenters also responded that it is inappropriate to allow federal
land managers, who are not directly accountable for managing air
quality, to independently make decisions for which air agencies are
responsible. As we have noted previously in this preamble, federal land
managers do play an important role

in helping states and tribes improve the air quality in those areas
that do not meet the NAAQS. Regardless of whether the provisions in the
General Conformity Rule \76\ apply, commenters specifically asked the
EPA to ensure that burn managers using BSMP consult with the air agency
or air agencies within whose jurisdiction the burn is being conducted
regarding the selection and use of BSMP to ensure that those BSMP are
appropriate and address local air quality and public health issues.
Some land managers have offered the counter-perspective that pre-burn
approval on a fire-by-fire basis could consume resources from all
parties and have no practical effect regarding actual measures taken
before, during or after a fire. These same land managers also
articulated that requiring extensive pre-burn discussions between
burners and air agencies could have the unintended result of burners
not using BSMP.
---------------------------------------------------------------------------

    \76\ The General Conformity Rule requires that federal agencies
work with state, tribal and local governments in nonattainment and
maintenance areas to ensure that federal actions conform to any
applicable SIP, FIP or TIP.
---------------------------------------------------------------------------

    The EPA must balance the concerns raised by the states during the
comment period on the NPRM with the concerns identified by other
federal agencies with which we have consulted in the development of
this action. To effect this balance, the EPA is incorporating preamble
language and rule text that requires that air agencies, federal land
managers and other agencies as appropriate, periodically discuss with
the burn managers operating within their jurisdiction and document the
process by which air agencies and land managers will work together to
protect public health and manage air quality impacts during the conduct
of prescribed fires on wildland. Consistent with operational protocols
within the fire management community, these discussions must include
outreach and education regarding general expectations for the selection
and application of appropriate BSMP and goals for advancing strategies
and increasing adoption and communication of the benefits of
appropriate BSMP. As with other components of this final rule, we are
not defining the mechanism by which air agencies and land managers will
conduct and document these discussions nor are we prescribing the full
scope of these discussions. Rather, we are finalizing regulatory text
that, after an initial implementation period, the EPA will not concur
with a request to exclude data that have been influenced by a
prescribed fire on wildland if the air agency(ies), federal land
managers and burn managers have not discussed and documented a process
that includes outreach and education regarding general expectations for
the selection and application of appropriate BSMP and goals for
advancing strategies and increasing adoption and communication of the
benefits of appropriate BSMP. The initial implementation period is
defined as 2 years from the effective date of this action. This time
will allow air agencies and land managers to develop and incorporate
the collaboration process into operational management.
    The EPA expects that the mechanism under which these discussions
are conducted and documented could be formal, such as a Memorandum of
Understanding or an Interagency Agreement, or it could be a letter
agreement. Similarly, in indicating that discussions occur
``periodically,'' we mean that discussions could occur annually at the
beginning of a burn season, prior to initiating burns on identified
tracts of land, or on some other identified frequency. We do not expect
discussions prior to each prescribed fire on wildland. The EPA also
expects that discussions will include outreach and education regarding
general expectations for the selection and application of appropriate
BSMP and goals for advancing strategies and increasing adoption and
communication of the benefits of appropriate BSMP and not the
initiation or timing of the prescribed fire (except in those cases
where a BSMP specifies certain factors related to the timing). Not all
BSMP are appropriate for all burns. Goals for applicability should
remain flexible to allow for onsite variation and site-specific
conditions that can be variable on the day of the burn. Where states
have an existing, documented process or program under which air
agencies, federal land managers, state fire agencies and other entities
engage with burn managers regarding the protection of public health and
air quality and general expectations for the selection, application and
benefits of appropriate BSMP, they may rely upon and reference this
process or program when addressing the not reasonably controllable or
preventable criterion for an exceptional events demonstration for a
prescribed fire.
    Also related to air agency and land manager collaboration, we have
clarified the regulatory language at 40 CFR 50.14(b)(3)(ii)(A) to
require that when a NAAQS exceedance or violation occurs when a
prescribed fire is employing an appropriate BSMP approach that the air
agency and the burn manager conduct a retrospective review of the
prescribed fire event and the employed BSMP to ensure the protection of
air quality and public health and progress towards restoring and/or
maintaining a sustainable and resilient wildland ecosystem. Either the
air agency or the burn manager could initiate such a retrospective
review. This regulatory language previously indicated that the ``State
must undertake a review of its approach. . . .'' The added regulatory
text clarifies our intent in using the term ``approach.'' We are also
requiring that if the prescribed fire becomes the subject of an
exceptional events demonstration, the demonstration must include
documentation of the post-burn review. The EPA may be unable to concur
on a demonstration that does not include documentation of the post-burn
review. Together, the regulatory language at 40 CFR 50.14(b)(3)(ii) now
requires both proactive discussions focused on education and outreach
regarding BSMP and a ``lessons learned'' review of events that occur
with the use of BSMP. We note that this required collaborative
proactive and retrospective approach does not affect any land manager's
ability to conduct a prescribed fire, only whether a prescribed fire
conducted after the effective date of this action is eligible for
consideration as an exceptional event. The mandatory provisions for
these required discussions do not apply where a burner is operating
under a developed and implemented certified SMP.
    Comments and Responses. The EPA received many comments expressing
agreement with the EPA's recognition of the importance of prescribed
fire on wildland and welcoming continued dialogue among state, tribal
and local air agencies, the EPA and other federal agencies to ensure
that land managers have adequate available tools to manage ecosystem
development and restoration and manage wildland vegetation, including
use of planned prescribed fires and letting some wildfires proceed
naturally, and to ensure that use of these tools is protective of
public health and does not result in unhealthy air. No commenters
disagreed with this objective, but, as described in the following
paragraphs, some commenters provided feedback regarding applying the
specific aspects of prescribed fire on wildland to the exceptional
events process.
    Some commenters supported the proposed definition of prescribed
fire, while others offered suggestions for revision. Several commenters
recommended that we include within the regulatory definition the
concept

that prescribed fire on wildland must be conducted using either SMP or
BSMP principles. While we agree that either a SMP or BSMP are required
for a prescribed fire to be eligible for consideration under the
Exceptional Events Rule, as indicated in this preamble and in the
regulatory text at 40 CFR 50.14(b)(3)(ii)(A), we have not added either
SMP or BSMP to the regulatory definition of a prescribed fire because
to do so would have the effect of excluding from the definition of
prescribed fire those deliberately ignited fires that do not use BSMP
or SMP. That is, we would not have terminology to define intentionally
ignited fires not using BSMP or SMP, which the land management
community refers to as prescribed fires. We believe that promulgating a
regulatory definition that is substantively different than the common
usage would create confusion. Moreover, the definition of prescribed
fire that we are promulgating combined with the specific exceptional
events provisions for prescribed fire on wildland (e.g., the
requirement that the fire must have been conducted under a SMP or have
BSMP applied) will achieve the same goal as the suggested revision to
the definition of prescribed fire.
    Another commenter suggested that the definition of prescribed fire
also include the caveat that that ``applicable laws, policies, and
regulations'' (1) actually exist (2) are enforceable by or through
delegated authority from the state air quality management entity, and
(3) are intended to adequately control emissions and impacts at all
downwind locations. We have not incorporated the commenter's suggested
language. Under the CAA, states, exclusive of tribal lands, are
primarily responsible for the administration of air quality management
programs within their borders. As the responsible entity, states
promulgate laws and regulations, where needed, and ensure they are
followed and are enforceable (states also develop policies, but
policies are generally not enforceable). We note that in some states,
legislation gives the leadership of fire management to a forestry or
public safety agency rather than to an air agency. As pointed out by
one commenter, the EPA cannot mandate that states grant air agencies
the authority or purview to regulate or enforce public health and
safety. We can, however, require coordination as a condition for the
EPA's approval for the exclusion of event-influenced ambient data,
which is what we have done with the regulatory language at 40 CFR
50.14(b)(3)(ii)(A).
    As previously noted, after considering public comments, we are
finalizing that to satisfy the human activity unlikely to recur at a
particular location criterion, the air agency may rely on either 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.
While a few commenters agreed with the language as proposed, several
commenters asked for clarification regarding recurrence and the
development of land management plans. Specifically, commenters asked
how the recurrence frequency identified in land management plans as
being needed to achieve land management goals or defined by the natural
fire return interval compares to the recurrence frequency generally
established for the human activity unlikely to recur at a particular
location criterion. In discussing the concept of recurrence in Section
IV.E.1 of this preamble, we note that the general benchmark for
recurrence (i.e., three events in 3 years) does not apply to prescribed
fires. Rather than using this general benchmark for prescribed fire on
wildland, we are promulgating in 40 CFR 50.14(b)(3)(iii), that
recurrence for prescribed fires is defined by either 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. Thus, the
recurrence frequency for prescribed fire is specific to the ecosystem
and resource needs of the affected area. Several additional commenters
requested that we codify language allowing either the natural fire
cycle or the fire frequency needed to meet ecological objectives to be
defined by scientific literature. We are not codifying the concept that
recurrence can be defined by scientific literature, but we are
including this clarification in the final rule preamble.\77\ Two
additional commenters asked that we clarify how an event spanning
multiple days counts towards recurrence. As we discuss in Section
IV.E.1 of this preamble, the EPA recognizes that a single event,
natural or caused by human activity (to include prescribed fire
events), can span multiple days and result in an air agency flagging
multiple monitor-day values in AQS (i.e., multiple exceedances of a
given NAAQS at a single monitor in a single day or multiple NAAQS
exceedances at multiple monitors on multiple days). The EPA considers a
single discrete event to be one occurrence.
---------------------------------------------------------------------------

    \77\ As a general matter, this preamble provides non-binding
guidance and recommendations for satisfying specific rule criteria.
This does not mean that these recommendations are the only way to
address a given issue. The preamble guidance only precludes other
approaches when the rule language identifies a specific condition as
being necessary to satisfy a given requirement.
---------------------------------------------------------------------------

    Commenters also asked for clarification regarding the development
of land and resource management plans. Specifically, commenters note
that while the description and content of the plans identified in the
preamble to our proposed rule may be appropriate for federal agencies,
the description and content of land and resource management plans was
not appropriate for private landowners who burn at the landscape level.
Commenters asked that we clarify that prescribed fires undertaken by
private landowners or on lands managed by multiple parties that are
consistent with their management plans be considered under the
exceptional events process. We disagree with the commenters on this
point. The existence of identified objectives in a state or private
management plan may not be sufficient under the exceptional events
process. Rather, the stated objectives must include those identified in
this rule. The EPA is promulgating regulatory provisions that describe
the process and requirements by which emissions from prescribed fires
on wildland causing an exceedance or violation of a NAAQS can be
considered for exclusion under the Exceptional Events Rule. In
finalizing these rule revisions, our intent is to clearly articulate
the components needed to satisfy the statutory requirements under CAA
section 319(b) and the Exceptional Events Rule. It is not our intent to
exclude specific event types or scenarios from consideration. Rather,
the EPA will review each event on a case-by-case basis considering the
merits of each specific case. We recognize that addressing the
prescribed fire-related components may be more difficult in some states
than others (or more difficult for some land areas within a state than
other land areas within the same state) because of the

state legislative authority for fire management or because of the
nature and management/ownership of lands considered to be wildland. We
further recognize that successfully implementing these rule revisions
will require the coordination, cooperation and compromise of all
involved parties, including federal, state, local, tribal, and private
land owners/land managers; state, tribal and local air quality
agencies; and the EPA.
    Commenters provided a similar level of detailed feedback regarding
the not reasonably controllable or preventable criterion. Most
commenters agreed with the EPA's now final provision that, to be
considered under the provisions of the Exceptional Events Rule,
prescribed fires must be conducted under an adopted and implemented
certified SMP or using appropriate BSMP. One commenter asked that we
clarify in rule text that if a certified SMP is in place for an area,
then all prescribed fires conducted in the area must first comply with
the provisions in a SMP. In response to the commenter's suggestion, we
note in this preamble that if a state has adopted and implemented a
certified SMP, then a prescribed fire on lands included within the
scope of the SMP should be conducted under the terms of the SMP. We
note, however, that some SMP may allow individual burners to
voluntarily adhere to the terms of the SMP. If this is the case, or in
situations in which a state has developed, but not implemented, a SMP,
then burn managers may use BSMP to address the provisions of the
Exceptional Events Rule. States are responsible for implementing and
ensuring conformance with the terms of their SMP.
    Our proposal solicited comment on whether to include SMP elements
in the final rule revisions as rule text. We received comments
supporting retaining the SMP elements in the preamble as guidance, and
we received other comments supporting including the SMP elements in
regulatory language. As previously noted in this preamble, we are
retaining the SMP elements in the preamble as guidance. When the SMP
elements were developed for the 1998 Interim Air Quality Policy on
Wildland and Prescribed Fires, the language reflected actions
consistent with addressing three types of wildland fire (i.e.,
wildfire, prescribed fire and wildland fire use fire). Fire terminology
now recognizes two types of wildland fire: Wildfire and prescribed
fire. We chose not to include provisions in regulatory text that do not
reflect current terminology. Additionally, in the 1998 Interim Air
Quality Policy on Wildland and Prescribed Fires, we recommended that
all state-certified SMP include the six identified elements. However,
because the elements were only recommended versus being required, not
all states adopted all six elements. Requiring the six SMP elements in
the rule text could result in some states needing to revise their SMP.
Where a state has incorporated the SMP into a SIP, the effects of
including the SMP elements in the final rule text could include
revising the SIP if the state intends to rely on the SMP path to
address the controllable prong of the not reasonably controllable or
preventable criterion. As we note in this preamble, based on commenter
feedback, we have slightly modified the descriptions of some of these
components. For example, several commenters noted that the
authorization to burn component appears to attempt to require burn
permits. We have clarified that while this component must include a
process for authorizing or granting approval to manage prescribed fires
on wildland, this authorization process may or may not include burn
permits.\78\ Also in response to commenter feedback, we have clarified
the program evaluation component including ``periodic review'' by
interested stakeholders of the SMP effectiveness and program revision
as necessary.
---------------------------------------------------------------------------

    \78\ By ``burn permit,'' we mean a document or communication
saying that a particular party may conduct a prescribed fire in a
particular area on a particular day or range of days. Acceptable
alternative approaches to burn permits include communicating more
broadly where and when landowners may conduct prescribed fires.
However, we do not consider a program that authorizes prescribed
fire across broad areas throughout an entire season with no regard
for meteorological or pollution conditions on specific days to be a
SMP.
---------------------------------------------------------------------------

    Several commenters expressed support for our proposal to remove the
phrase ``and must include consideration of development of a SMP'' from
the sentence that in 40 CFR 50.14(b)(3) of the 2007 Exceptional Events
Rule that read, ``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.'' As we noted in the proposal,
while the EPA supports states considering the development of a SMP when
an event occurs while using BSMP, we believe states have had many
opportunities to develop SMP since 2007. The language in the 2007 rule
effectively requires an ongoing consideration to develop a 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 under CAA
section 319(b). We maintain 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 or more frequent or intensive use of BSMP
to minimize smoke impacts. In addition, we believe that a 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 the sentence we proposed to remove. For
these reasons, as supported by commenter feedback, we are removing the
language from the rule text.
    Four states and one national organization agreed with our proposal
to include BSMP in rule text. One national forestry association
indicated its preference to include BSMP in the preamble as guidance.
As noted, we are including the table identifying BSMP in regulatory
text. While not in regulatory text, we are also incorporating into this
final rule, as guidance in the preamble, Table 4, which includes
example content in a burn report. Although one commenter asked that
this table be included in regulatory text, we are not doing this
because the table provides example content of a burn report, which is
only a single example of the type of documentation that air agencies
can use in their exceptional events demonstrations for prescribed fires
to show the implementation of BSMP. It is not our intent to convey as
required documentation either burn reports or the identified content.
    Several commenters supported, and no commenters opposed, the
presumption that a prescribed fire should be considered not reasonably
preventable based on the benefits that would be foregone if the burn
did not take place. As we have noted, we have incorporated this concept
into the final rule preamble and finalized associated regulatory text,
which allows states to rely on 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 to satisfy the preventability prong of the not
reasonably controllable or preventable criterion.
3. Stratospheric Ozone Intrusions
    The section of the proposal addressing exceedances due to

stratospheric ozone intrusions did not propose any new guidance or
specific regulatory language. Rather, it provided a general
(meteorological) description of stratospheric ozone intrusions,
indicated that stratospheric ozone intrusions are purely natural
events, and provided general guidance on applying the Exceptional
Events Rule criteria when preparing demonstrations for stratospheric
ozone intrusion events. Because we intend to develop a supplementary
guidance document, Draft Guidance on the Preparation of Exceptional
Events Demonstrations for Stratospheric Ozone Intrusions, which will
apply the final rule provisions to the development of demonstrations
for stratospheric ozone intrusion events and will include example
analyses, conclusion statements and technical tools that air agencies
can use in their demonstrations, we are not repeating in this final
action the language that appeared as guidance in the proposal. We
intend to post the draft guidance and instructions for providing public
comment on the exceptional events Web site at http://www2.epa.gov/air-quality-analysis/treatment-data-influenced-exceptional-events shortly
after finalizing these rule revisions.
    After consideration of the public comments, as discussed more fully
in the paragraph that follows, we are finalizing a rule provision
related to satisfying the not reasonably controllable or preventable
criteria for stratospheric ozone intrusions. While the not reasonably
controllable or preventable criterion applies to natural events, the
EPA has stated that air agencies generally have no obligation to
specifically address reasonable controls if the event was natural. We
applied this concept when proposing (and, in this action, finalizing) a
categorical presumption of not reasonably controllable for wildfires
that would involve referencing the appropriate regulatory citation in
the demonstration. The proposal preamble repeatedly acknowledges that,
similar to wildfires, stratospheric ozone events are purely natural
events. The proposal also stated in the not reasonably controllable or
preventable section that ``In these cases [volcanic releases of
SO2 and stratospheric ozone intrusions], 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.'' As a natural outgrowth of our proposal, and as
specifically suggested by one commenter, we are extending this
categorical presumption to satisfying the not reasonably controllable
or preventable criterion to stratospheric ozone intrusion events by
promulgating regulatory language at 40 CFR 50.14(b)(6).
4. High Wind Dust Events
a. Summary of Proposal
    The EPA proposed as guidance in the preamble and/or as changes to
regulatory text concepts and language that first appeared in the
Interim High Winds Guidance document. These changes included adding
regulatory definitions for high wind dust events and a high wind
threshold, determining the scenarios under which a high wind dust event
could be considered ``natural'' for purposes of the Exceptional Events
Rule, identifying that remote, large-scale, high-energy and/or sudden
high wind dust events, such as ``haboobs,'' would generally satisfy the
not reasonably controllable or preventable criterion with streamlined
documentation, and incorporating best management practices (i.e., soil
conservation management practices) as reasonable controls. We solicited
comment on all of these concepts and discuss each in more detail in the
following paragraphs.
    Definition of an Event. Consistent with the EPA's proposed revision
of the regulatory definition of an exceptional event to include both
the event and its associated resulting emissions, the EPA proposed 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. We also proposed, consistent with the nullified language in the
2007 Exceptional Events Rule preamble, the PM10 Natural
Events Policy and the Interim High Winds Guidance, 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 level of evidence needed to demonstrate not reasonably controllable
or preventable, the EPA proposed 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 proposed 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 reviewed a demonstration. The proposal
noted that if we received specific information based on relevant
studies that suggest a different high wind threshold for an identified
area, the EPA would notify the affected air agency so that the agency
may consider basing its demonstration on that threshold value. The
proposal also indicated that the EPA would consider such information as
part of the weight of evidence analysis for a submitted demonstration.
As we had previously articulated in the Interim High Winds Guidance,
the proposal stated that air agencies could, as an alternative to the
25 mph high wind threshold, identify and use an area-specific high wind
threshold that is more representative of local/regional conditions.
    The proposal explained that we would use the high wind threshold
concept when assessing the not reasonably controllable or preventable
criterion for all high wind dust exceptional events demonstrations
except for those events in which the source of the emissions is
entirely natural (i.e., windblown dust from natural undisturbed lands)
or where a large-scale and high-energy high wind dust event generates
emissions that cause an exceedance or violation. In the case of a
large-scale and high-energy high wind dust event, no assessment of
reasonable controls is needed to satisfy the controllability prong of
the ``not reasonably controllable or preventable'' criterion.
    Large-Scale and High-Energy High Wind Dust Events. The EPA proposed
rule language to apply a general 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 provided that if an event met the criteria for a large-scale and
high-energy event, then it would be considered not reasonably
preventable or controllable. Therefore, a demonstration limited to such
event(s) will not need to substantively address this criterion.
    Best Management Practices. The EPA solicited comment on whether, 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. The preamble repeated the EPA's
previous guidance that USDA/NRCS-approved BMPs designed to effectively
reduce fugitive dust 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.\79\ 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.
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    \79\ 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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b. Final Rule
    After consideration of the public comments received, and for the
reasons discussed in our proposed rule section and response to such
comments, we are finalizing regulatory language defining high wind dust
events and high wind threshold; determining the scenarios under which a
high wind dust event could be considered ``natural'' for purposes of
the Exceptional Events Rule; identifying that large-scale and high-
energy high wind dust events, such as ``haboobs,'' would generally
satisfy the not reasonably controllable or preventable criterion with
streamlined documentation; and providing guidance related to
incorporating best management practices (i.e., conservation management
practices) as reasonable controls.
    Definition of an Event. We are promulgating, as proposed, that a
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. No
commenters opposed this definition.
    Also as proposed, we are promulgating regulatory text that we
consider high wind dust events as ``natural events'' in cases where
windblown dust is solely from natural sources or where all significant
anthropogenic sources of windblown dust have been reasonably
controlled.\80\ While we discuss this concept (and related comments and
responses) in more detail in Section IV.D of this preamble, we note
here that this long-standing policy was first established in the
PM10 Natural Events Policy, which provided that:
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    \80\ As identified in Section IV.D of this preamble, 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 PM10 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
measures (BACM).\81\
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    \81\ Areas Affected by PM-10 Natural Events (the PM10
Natural Events Policy), memorandum from Mary D. Nichols, Assistant
Administrator for Air and Radiation, to the EPA Regional offices,
May 30, 1996.

    High Wind Threshold. We are also promulgating, as proposed, that
the definition of a high wind dust threshold is 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. No
commenters opposed this definition. In concert with this definition, we
are also finalizing a modified version of our proposed regulatory text
that we will 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. Several commenters
supported this definition either as proposed or with the clarification
that air agencies could develop as an alternative to the 25 mph high
wind threshold, their own area-specific high wind threshold that is
more representative of local/regional conditions. Although we included
this language in the proposal preamble, we did not include this
language in the proposed regulatory text. We are including this
language in the final regulatory text as a result of commenter
feedback.
    We also repeat language from the proposal that any area-specific
high wind threshold should be representative of conditions (i.e.,
sustained wind speeds \82\) 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 the
wind speed at which significant emissions begin to occur due to
reasonable controls on disturbed soil or the natural wind resistance of
undisturbed areas becoming overwhelmed. We further note that we
included guidance on both threshold development and determining wind
speeds in the Interim High Winds Guidance.\83\ While we believe this
guidance is still appropriate with respect to determining wind speed
characteristics and developing a wind speed threshold, we intend to
revise the guidance to incorporate the provisions of this final action.
We note that areas with Natural Events Action Plans that include a high
wind threshold that meets the criteria identified in the Interim High
Winds Guidance may be able to use the previously developed threshold as
an area-specific high wind threshold. The proposal also accepted
information on different high wind thresholds for identified areas (see
80 FR 72878). After evaluating comments advocating that the EPA
consider area-specific high wind thresholds, the EPA is codifying this
provision in the final rule. The EPA recognizes, however, that there
are likely to be limited situations in those areas in the western
U.S.\84\ where this threshold applies in which exceptional events occur
at wind speeds

less than 25 mph.\85\ Air agencies should consult with their EPA
Regional office when developing alternate high wind thresholds for a
particular area.
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    \82\ Section <IP_ADDRESS> 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.
    \83\ 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.
    \84\ See rule language that we are promulgating at 40 CFR
50.14(b)(5)(iii).
    \85\ The default threshold of 25 mph was based on extensive
windblown dust emissions research performed by the Department of
Civil and Environmental Engineering at the University of Nevada, Las
Vegas under contract to the Clark County Department of Air Quality
and Environmental Management. See 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, and Refined PM10
Aeolian Emission Factors for Native Desert and Disturbed Vacant Land
Areas. Final Report, June 30, 2006.
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    The EPA will continue to consider an area's high wind threshold
when reviewing demonstrations for events in a nonattainment or
maintenance area where the EPA has approved a SIP, TIP or FIP within 5
years of the date of the event. For a demonstration in such a case, the
not reasonably controllable criterion hinges only on implementation of
the control measures in the SIP, TIP or FIP, not on the content of
those measures. For events with sustained wind speeds above the high
wind threshold that occur simultaneously with high monitored PM
concentrations, it is very plausible that SIP, TIP or FIP controls were
being implemented and the high PM concentrations resulted from
emissions generated by sources in the area despite implementation of
those controls. 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 anthropogenic sources
unrelated to the event (e.g., dust from traffic for a special event)
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 must be included
in a demonstration. Specifically, it will inform the evidence required
for the not reasonably controllable or preventable criteria, the
possibility of noncompliance, or emissions from non-event sources.
    Similarly, the high wind threshold also aids in determining whether
a high wind dust event that includes emissions from anthropogenic
sources can be considered a natural event. We have clarified that
natural events can recur, sometimes frequently, and that we consider
reasonably controlled anthropogenic emissions sources to play little or
no direct role in causing emissions. For high wind dust events, if
sustained wind speeds are above the high wind threshold and the
anthropogenic emissions sources are reasonably controlled, it is more
likely that human activity plays little or no direct role in causing
emissions. Conversely, if sustained wind speeds are below the high wind
threshold it is more likely that human activity does have a direct role
in causing emissions because significant emissions under low wind
conditions only occur if the area has been disturbed by human activity
and those sources have not been reasonably controlled.
    As noted in the proposed rule preamble and in the Interim High
Winds Guidance, as part of an exceptional events demonstration for high
wind dust events, the EPA expects air agencies to provide relevant wind
data (e.g., wind speed and direction). Wind speed data consist of
analyses and statistics showing how the observed sustained wind speed
compares to the established high wind threshold and demonstrates a
relationship between the sustained wind speeds and measured PM
concentrations at a particular monitoring location. The EPA has
recommended that air agencies show these analyses as part of the clear
causal relationship criterion discussed in Section IV.E.3 of this
preamble. The EPA has encouraged air agencies to discuss wind direction
in the narrative and to present wind direction data graphically in
maps/plots in the clear causal relationship section of the high wind
dust events demonstration.
    The EPA will review any demonstration for a high wind dust event
not meeting the criteria for a ``large-scale and high-energy''
described in the next paragraph on a case-by-case basis. In doing so,
the EPA will consider what controls are reasonable in light of an
area's attainment status and associated CAA control requirements, the
frequency, and range of typical high wind dust events known (at the
time of the particular event that is the subject of the demonstration)
to occur in the area.
    Large-Scale and High-Energy High Wind Dust Events. Many commenters
supported the EPA's proposed 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,'' where sustained wind speeds can exceed 40 mph and generate
walls of dust several miles wide and more than a mile high. As a
result, we are finalizing this provision with several clarifying
changes to the proposed language at 40 CFR 50.14(b)(5)(vi), which read,
``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 reasonably
controllable criterion of paragraph (c)(3)(iv)(D) of this section.'' We
have changed this terminology to ``a large-scale and high-energy high
wind dust event.'' We have removed the phrase ``such as haboobs in the
southwest'' as a result of commenter feedback identifying that
``haboobs'' occur in places other than the ``southwest.'' We agree with
the commenter. We removed the descriptive terms ``remote'' and
``sudden'' because we found that these words do not effectively change
the characteristics of the type of event that we intend to include as
``a large-scale and high-energy'' high wind dust event. Thus, provided
the event meets the identified criteria for a ``large-scale and high-
energy'' high wind dust event, it could qualify for case-specific
treatment with respect to the not reasonably controllable or
preventable criterion.
    Some areas of the country may claim that, because of local
topography and meteorology, each PM exceedance that occurs in their
jurisdiction would qualify as a ``large-scale and high-energy'' high
wind dust event. While we acknowledge that large-scale and high-energy
high wind dust events in a particular area may be associated with
meteorological conditions unique to that area, we also believe that to
qualify for the specific exclusion at 40 CFR 50.14(b)(5)(vi), a large-
scale and high-energy high wind dust event must: Be associated with a
dust storm,\86\ have sustained wind speeds greater than or equal to 40
mph, have reduced visibility equal to or less than 0.5 miles,\87\ be
the focus of a ``Dust Storm Warning'' issued by the NWS (or a similar
scientifically-based government entity) and include NWS (or a similar
scientifically-based government entity) observations of dust storms and
blowing dust. In addition, the event must be associated with measured
exceedances occurring at multiple monitoring sites over a large
geographic area unless the area has only a single PM monitor or if the
area has monitors operating on a sampling frequency that does not
coincide with the timing of the event.
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    \86\ The NWS defines a dust storm as a severe weather condition
characterized by strong winds and dust-filled air over an extensive
area. See definition at http://w1.weather.gov/glossary/.
    \87\ Many NWS distributed alerts and advisories include
visibility estimates. In addition, many airports provide estimates
of surface visibility. Air agencies may also be able to use
nephelometers to determine visibility.

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    Best Management Practices. After consideration of the public
comments, as discussed more fully in this paragraph, we are finalizing
here as guidance that, on a source or area-specific basis, we would
accept as ``reasonable controls'' for purposes of satisfying the not
reasonably controllable or preventable criterion for a particular
potentially contributing source, those USDA/NRCS-approved BMPs designed
to effectively reduce fugitive dust air emissions and prevent soil loss
in agricultural applications in cases where these measures have been
incorporated into an EPA-approved SIP, FIP or TIP or incorporated into
state laws, regulations or local ordinances and where those measures
consist of controls specific to the pollutant and potentially
contributing source.
    As we discuss in Section IV.E.2.b of this preamble, 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 monitored exceedance or violation, including the contribution
from local sources, (2) identify the relevant, 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. For example,
applying this approach to farm- and operation-specific BMPs for a high
wind dust event that occurs during harvest time, an air agency would
identify the potentially contributing agricultural source (e.g.,
harvesting operations of crop X), identify the relevant BMP (e.g.,
baling, which reduced PM emissions from residue burning and chopping)
and provide evidence of penetration, scale and intensity (e.g., baling
applied at X of Y acres).
c. Comments and Responses
    We noted in the final rule portion of the High Winds Dust Events
section of this preamble that we did not receive comments related to
the definition of either high wind dust event or high wind threshold.
We further noted in the previous discussion that commenters did provide
feedback regarding establishing, in rule, a high wind threshold of 25
mph. Several commenters supported this definition either as proposed or
with the clarification that air agencies could develop as an
alternative to the 25 mph high wind threshold, their own area-specific
high wind threshold that is more representative of local/regional
conditions. As already indicated, we have included this clarification
in the regulatory text. Several of the commenters suggesting this
revision also asked that the regulatory language include a provision
that exceptional events can still occur at wind speeds less than 25
mph. We have not included this change as we believe that allowing areas
to establish their own threshold will largely address this potential
issue. Additionally, as stated in the proposal and in this final
action, the EPA will review other events on a case-by-case basis
considering the merits of each specific case. Still more commenters
recommended keeping the high wind threshold as guidance rather than
rule as it is ``overly restrictive.'' The EPA believes these revisions
provide sufficient additional flexibility to address this concern.
    Another commenter asked that we include in this final action
language from our Interim High Winds Guidance, which stated ``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.'' We still believe this is an accurate statement, and
we are noting this point in this final action.
    As we noted previously, many commenters supported the EPA's
proposed rule language to apply a case-specific approach when
considering reasonableness of controls for large-scale and high-energy
high wind dust events, such as ``haboobs.'' Another commenter noted
that haboobs should not have special treatment under the rule
revisions. This same commenter asked that we define large-scale and
high-energy events, which we have done in the discussion of the final
rule. Regarding special treatment of these types of events, we maintain
that some events are of a scale and intensity that they would have
overwhelmed all reasonable controls and other efforts to minimize wind-
blown dust emissions. We maintain that such events warrant different
treatment under the Exceptional Events Rule. We do, however, note that
air agencies will need to provide evidence that the claimed event
satisfied all of the other Exceptional Events Rule criteria.
    We have incorporated relevant commenter feedback regarding BMP into
our discussion of BMP in the final rule section of this action. We note
that one additional commenter asked that we clarify whether the
fugitive dust control plans included in approved air quality permits
are or can represent reasonable controls for permitted sources. While
we are not addressing this comment here, we note that we discuss the
relationship between BACM or fugitive dust control plans and reasonable
controls in our comments and responses section of the not reasonably
controllable or preventable portion of this final action (see Section
IV.E.2.c of this preamble).

G. Other Aspects of Identifying Exceptional Events-Influenced Data and
Demonstration Submittal and Review

    This portion of the proposed rule discussed the eight topics
identified in the following sections, as well as a ninth topic
addressing who may submit a demonstration for data exclusion. Because
we identify, discuss and respond to questions regarding those entities
that are allowed to submit a demonstration in Section IV.A of this
preamble and because the proposal contained no additional items needing
clarification, we omit that topic in this part of the final action.
1. Aggregation of Events
a. Summary of Proposal
    The EPA proposed and solicited comment on guidance in the preamble
and 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 and the NAAQS with the
shorter period. This proposed approach allowed for examining one day at
a time. For example, if an event were demonstrated to have caused a 24-
hour concentration of SO2 to exceed the level of the annual
SO2 NAAQS, the air agency and the EPA would consider this to
be a demonstration that the event caused an ``exceedance or violation''
with respect to the 24-hour NAAQS and the annual NAAQS. This would
avoid the need to determine if the 1-day effect of the event was enough
to cause the annual average concentration of SO2 to exceed
the level of the annual SO2 NAAQS. It would also allow the
data from a day to be excluded from calculation of the design value for
the 24-hour SO2 NAAQS even if the event did not cause an
exceedance of the level of the 24-hour SO2 NAAQS. However,
such exclusion would be unlikely to be material to compliance with the
24-hour SO2 NAAQS if there was no such exceedance of the
level of the 24-hour SO2 NAAQS.
    The EPA also proposed to allow air agencies to aggregate either
similar or dissimilar events (e.g., stratospheric ozone intrusion
followed by a wildfire

or two distinct wildfires) that influence the same NAAQS but that occur
on different days for the purpose of determining whether their
collective effect has caused an exceedance or violation. The proposed
event aggregation process would apply only for NAAQS with averaging or
cumulative periods longer than 24 hours. Although we proposed this
approach to event aggregation, we also indicated that it may be
difficult to implement if the effects of the individual events on their
individual days are not fully quantified. We proposed rule text and
solicited comment on this approach.
b. Final Rule
    After consideration of the public comments, as discussed more fully
in the subsequent section, we are finalizing, as proposed and as
supported by several commenters, rule language that will allow an air
agency to compare a 24-hour concentration of any NAAQS pollutant to the
NAAQS for the same pollutant with a longer averaging period as part of
a weight of evidence showing for the clear causal relationship with
respect to the NAAQS with the longer period. As we discussed in the
proposal, 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, CO, NO2,
SO2 and some PM measurements, to 24-hour measurements for
lead and other PM measurements. Under the 2007 Exceptional Events Rule,
air agencies identify individual measurements in AQS and compare these
measurements to the subject 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, which may still
apply in certain areas). The provision that we are finalizing allows an
air agency to compare a 24-hour concentration of any NAAQS pollutant to
the NAAQS for the same pollutant with a longer averaging period as part
of the clear causal relationship showing. Using Table Q30-2 in the
Interim Q&A document \88\ as a guide, this rule revision will allow an
air agency to compare a 24-hour averaging period for PM2.5
to either the 24-hour PM2.5 NAAQS or the annual NAAQS.
(Note: If air agencies desire to exclude the identified concentration
for both the 24-hour and the annual PM2.5 NAAQS, they need
to specifically request exclusion for both NAAQS, assuming regulatory
significance for both standards.) Air agencies could also compare a 24-
hour lead measurement to the rolling 3-month averaging period. A number
of commenters supported the provision as proposed. One commenter,
however, indicated that comparing a 24-hour concentration of any NAAQS
pollutant to the NAAQS for the same pollutant with a longer averaging
period is an ``apples to oranges'' analysis that could increase
uncertainty and decrease the quality of the demonstration. The EPA
acknowledges the commenter's perspective, but believes that
clarification is needed regarding the comparison of measured
concentrations to ambient air quality standards because, as we have
explained, the measurement time frames do not often agree with the
averaging period of the NAAQS. In preparing demonstrations, air
agencies have often asked the EPA Regional offices whether such
comparisons are allowed under the Exceptional Events Rule, and, if they
are, how to present such comparisons in a demonstration. Our preamble
discussion about these comparisons and our promulgation of associated
rule language responds to these comments and provides clarity. We also
note that the 2007 rule preamble discussed and allowed this type of
comparison for the specific case of the PM2.5 annual NAAQS
and the 24-hour PM2.5 NAAQS. We are extending this concept
to all similar NAAQS comparisons.\89\
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    \88\ 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.
    \89\ 72 FR 13570 (March 22, 2007).
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    We are also finalizing regulatory language allowing air agencies to
aggregate either similar or dissimilar events (e.g., stratospheric
ozone intrusion followed by a wildfire or two distinct wildfires) that
influence the same NAAQS but that occur on different days for the
purpose of determining whether their collective effect has caused an
exceedance or violation of a NAAQS with an averaging or cumulative
period longer than 24 hours.\90\ That is, when considered individually,
each event would not separately need to result in an exceedance or
violation of a given NAAQS. The collective effect of the aggregated
events would, however, need to cause an exceedance or violation of a
NAAQS with an averaging or cumulative period longer than 24 hours.
Also, as part of this aggregation approach, the air agency must show
that each identified event separately satisfies each of the three
technical rule criteria (i.e., human activity/natural event, not
reasonably controllable or preventable, and clear causal relationship).
For the clear causal relationship showing, the air agency would need to
definitively show that each discrete event contributed to the elevated
concentrations and that, together, the cumulative effect of the events
caused the exceedance or violation of a NAAQS with an averaging or
cumulative period longer than 24 hours. We do not intend our approach
for event aggregation to allow for the aggregation of unnamed events or
events that occur over the course of an extended timeframe. Two
commenters urged the EPA to remain silent on this provision and not
include it in rule language, while several other state, local, tribal
and association commenters supported the provision as proposed. To
clarify, the final rule text also includes a statement that air
agencies may aggregate events occurring on the same day and compare the
cumulative effects to a NAAQS with an averaging period of 24 hours or
less. As previously noted, for the clear causal relationship showing,
the air agency would need to definitively show that each discrete event
contributed to the elevated concentrations and that, together, the
cumulative effect of the events caused the exceedance or violation of
the NAAQS and that each identified event separately satisfies each of
the three technical rule criteria (i.e., human activity/natural event,
not reasonably controllable or preventable, and clear causal
relationship).
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    \90\ See 80 FR 72882, which proposed allowing event aggregation
occurring on different days for NAAQS with averaging or cumulative
periods longer than 24 hours. It is not appropriate to aggregate the
effects of events occurring over more than a 24-hour period to a
standard that is less than or equal to 24 hours.
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    We provide a specific approach to aggregating wildfire-related
events that occur in different locations on the same day in the
Wildfire Guidance, which we are releasing concurrently with this
action. The aggregation methodology in the Wildfire Guidance applies
for purposes of determining whether a given wildfire could use a tiered

approach to satisfy the clear causal relationship criterion in a
demonstration for an ozone standard (i.e., either a 1-hour or an 8-hour
standard). The current ozone NAAQS do not meet the pre-conditions for
the aggregation approach discussed here, which requires the averaging
or cumulative period of the standard to be longer than 24 hours.
Additionally, use of the aggregation approach in the Wildfire Guidance
would occur only after an exceedance or violation of the relevant ozone
NAAQS versus the aggregation approach that we are finalizing in rule
text that would allow aggregation to determine whether an exceedance or
violation occurred. For these reasons, the regulatory approach to
aggregation and the specific approach for wildfires that may influence
ozone concentrations cannot be interchanged.
c. Comments and Responses
    We address any additional comments received on this topic in the
Response to Comments document found in the docket for this action.
2. Demonstrations With Respect to Multiple NAAQS for the Same Pollutant
a. Summary of Proposal
    The proposal solicited 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. For example, the ``approved for one NAAQS
approved for all NAAQS for the same pollutant'' concept would have
allowed an air agency to prepare a demonstration for a 1-hour NAAQS
and, if concurred, exclude data for both a 1-hour and an 8-hour NAAQS
for the same pollutant.
b. Final Rule
    Several commenters supported promulgating rule text for the
proposed concept that 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,
but one commenter noted that this pathway is unlawful and would allow
air agencies an easier path to exclude unfavorable data. After
considering the feedback, we are retaining our current approach to
excluding data on a NAAQS-specific basis with the previously identified
clarifications for certain measurements and certain NAAQS. CAA section
319(b)(3)(B)(ii) refers to ``the measured exceedances of a national
ambient air quality standard'' (emphasis added); CAA section
319(b)(3)(B)(iv) references excluding data from use in determinations
with respect to ``exceedances or violations of the national ambient air
quality standards.'' These passages do not clearly say that the EPA
must or may allow data to be excluded for the purposes of all NAAQS for
a given pollutant if the conditions for exclusion are satisfied for one
of the NAAQS but not all of them. Even assuming arguendo that that the
passages permit the EPA to allow such exclusions, we believe that we
would be undermining the public health and welfare purpose of the NAAQS
if we were to allow such broad exclusion. One public commenter provided
a cogent statement of this fact. The CAA also directs that protection
of public health is the highest priority. The commenters in favor of
broad exclusion did not provide a legal or public health protection
basis for their recommendations. Therefore, neither the final rule nor
the preamble to the final rule includes language or guidance for the
proposed ``approved for one NAAQS approved for all NAAQS for the same
pollutant'' concept.
c. Comments and Responses
    We address any additional comments received on this topic in the
Response to Comments document found in the docket for this action.
3. Exclusion of Entire 24-Hour Value Versus Partial Adjustment of the
24-hour Value for Particulate Matter
a. Summary of Proposal
    Citing Question 29 of the Interim Q&A document, the proposal
articulated the EPA's current recommendation that air agencies
preparing demonstrations to support requests to exclude
PM2.5 and PM10 data obtained via monitor
instruments that provide 1-hour measurements should flag all 24 1-hour
values within a given event-affected day and consider the effect of the
event on the 24-hour average concentration, even if the event did not
last all these hours. If concurred upon, flagging all 1-hour values and
considering the effect of the event on the 24-hour average
concentration relative to the level of the 24-hour NAAQS ultimately
results 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 instruments.\91\ We further recommended that
flagging all 24 1-hour values is appropriate because flagging only peak
or selected hours could result in the remaining 1-hour values still
meeting the data completeness requirements, even though there may be
very few remaining 1-hour measurements, 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 relative to the actual
24-hour concentration or the 24-hour concentration that would have
existed in the absence of the event.\92\ The proposal solicited comment
on codifying this approach in rule text to eliminate any regulatory
uncertainty.
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    \91\ 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.
    \92\ 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.
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b. Final Rule
    After considering the public comments we received, and for the
reasons discussed in our proposed rule section, we are finalizing
regulatory language, supported by a number of commenters, to exclude
all 24 1-hour values within a given event-affected day for
PM2.5 and PM10 data obtained via monitor
instruments that provide 1-hour measurements. We believe that the
exclusion of all hours in a given event-affected day is appropriate,
consistent with the approach for filter based analyzers, and will
eliminate the calculation of uncertain and potentially biased daily
values for PM2.5 and PM10 NAAQS. We also agree
with three commenters who suggested that the EPA modify the programming
in AQS to automatically flag all remaining hourly values in the 24-hour
period if an air agency flags only the event-influenced hours within
AQS. The EPA will program the identified changes within AQS.
c. Comments and Responses
    We address any additional comments received on this topic in the
Response

to Comments document found in the docket for this action.
4. Flagging of Data
a. Summary of Proposal
    The EPA proposed to revise the ``general'' schedule language
contained within 40 CFR 50.14(c)(2) by removing the timelines
associated with initial event flagging. We also proposed to modify the
associated data flagging process within AQS to correspond with the
proposed regulatory changes.\93\ Specifically, the revisions proposed
to modify the flagging of exceptional event data by defining
``flagging'' as the application of the one- or two-character event type
and event description text as described in the following paragraph,
along with a concurrent or subsequent request for data exclusion
communicated to the EPA through the Initial Notification of Potential
Exceptional Event process.
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    \93\ ``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 (R flags) 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 the EPA can act/concur only on an R flag.
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    The proposal noted that because the flagging of data necessarily
begins with the identification of an event, the EPA proposed to retain,
with modifications, the AQS free-form text field for an initial event
description. As is currently the practice, we would request that air
agencies use the ``initial event description'' to identify a unique,
real-world event. We proposed to expand this ``initial event
description'' 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).\94\ We proposed to simplify the process in AQS 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.
We noted that this would 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. The
proposal noted that ``associating'' monitors with an event defined in
time and space will save resources.
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    \94\ 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 R flags within AQS.
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    The proposal noted that the process of requesting exclusion for
identified data would 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
IV.G.5 of this preamble 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 Exceptional Events Rule and/or the EPA's guidance for other
applications of air quality data. The proposal indicated that 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.
    As noted previously, we proposed to remove the ``general'' flagging
schedule in 40 CFR 50.14(c)(2)(iii), which 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.
The proposal noted that 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. We proposed to remove the
current language at 40 CFR 50.14(c)(2)(iii) and reserve that section
number.
b. Final Rule
    As proposed, and as supported by numerous commenters, we are
removing the ``general'' flagging schedule in 40 CFR 50.14(c)(2)(iii),
which requires that air agencies submit request exclusion 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. We are making this
change because flagging data by the previously indicated deadlines 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 value. 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. No commenters disagreed with this proposal.
    One commenter requested that AQS retain the ability to incorporate
informational flags in the data identification process. This commenter
noted that informational flagging has uses beyond the exceptional
events process. We are retaining informational flags in AQS.
c. Comments and Responses
    We address any additional comments received on this topic in the
Response to Comments document found in the docket for this action.
5. Initial Notification of Potential Exceptional Event
a. Summary of Proposal
    As part of the best practices for communications \95\ during the