to bring the area into attainment will be implemented as expeditiously
as practicable.
    The second step in developing an RFP plan under this second
proposed option would be for the state to calculate the emissions
reductions that would be achieved by all measures implemented on
sources in the area corresponding with quantitative milestone dates
(i.e., by 4.5 years and 7.5 years after designation of the area). These
are the dates by which milestones for the area must be met, after which
a report is due to the EPA from the state to verify that

the area has met the milestones identified for the area and thereby has
also met the RFP requirements for the area. The EPA proposes that the
state must calculate the emissions reductions to be achieved at each
milestone year on a pollutant-by-pollutant basis.
    The third step under this proposed option would be for the state to
conduct modeling or employ another quantitative method to predict the
overall PM2.5 concentrations in the nonattainment area in
each milestone year. This air quality target could simply be
interpolated between the design value at the time of the area's
designation and the design value in the projected attainment year.
These air quality target values would serve as a points of comparison
for the monitored ambient air data that the EPA is proposing that the
state must submit as part of the milestone report due after the area
reaches each milestone date.
    This simplified approach to determining RFP for a Moderate
nonattainment area could apply equally well to areas that can
demonstrate attainment with the relevant NAAQS by the statutory
attainment date and those that cannot. See proposed 40 CFR 51.1012(c).
In addition, the EPA believes it offers a reasonable approach to ensure
that RFP is generally being met in the area without requiring extensive
quantitative analysis so long as it is generally linear for purposes of
achieving annual emissions reductions. The EPA seeks comment on these
two options proposed for states to meet the statutory RFP requirements.
3. RFP Inventories for RFP Analyses
    The EPA proposes that a state with a Moderate PM2.5
nonattainment area must submit one or more emissions projections as
part of the RFP plan (the ``RFP inventory'') for the area that, at a
minimum, includes projected emissions by different source types
corresponding to the quantitative milestone date(s) for the area,
described in greater detail in Section IV.H of this preamble.
Specifically, the EPA proposes that the RFP plan for any Moderate area
must contain a projected RFP inventory for each calendar year in which
quantitative milestones for a Moderate nonattainment area must be met.
For example, as explained in Section IV.H of this preamble, a state
must identify as part of the attainment plan submission for a Moderate
nonattainment area quantitative milestones to be achieved every 3 years
from the Moderate area attainment plan due date, or 4.5 years from the
effective date of designation of the area.\135\ For example, the first
round of designations for the 2012 PM2.5 NAAQS become
effective in April 2015; Moderate area attainment plans for these areas
will thus be due 18 months later, or in October 2016. The first
quantitative milestones for each of these areas would then have to be
met in October 2019; the second quantitative milestones, in October
2022; and so on, until the area attains the NAAQS. Under the EPA's
proposed approach for projected emissions inventories for RFP analyses,
the state would be required to submit such inventories as part of the
Moderate area attainment plan due in October 2016 that project
emissions from sources in the nonattainment area for the same calendar
years as those for which quantitative milestones would be due.
---------------------------------------------------------------------------

    \135\ According to section 189(a)(2)(B), Moderate area
attainment plans are due to the EPA 18 months after designation.
---------------------------------------------------------------------------

    The transportation conformity rule requires that attainment plans
establish motor vehicle emissions budgets. RFP plans submitted as part
of an attainment plan submission would therefore be required to
establish motor vehicle emissions budgets for direct PM2.5
and any relevant PM2.5 precursor.\136\ A motor vehicle
emissions budget for the purposes of a PM2.5 RFP plan is
that portion of the total allowable emissions allocated to on-road
sources as defined in the submitted RFP plan for the relevant years as
described above.\137\ Such motor vehicle emissions budgets would be
calculated using the latest planning assumptions and the latest
approved motor vehicle emissions model available at the time that the
attainment plan is developed.\138\
---------------------------------------------------------------------------

    \136\ For more information on PM2.5 precursor
requirements, see section 93.102(b)(2)(iv) and (v) of the
transportation conformity rule. See also the May 6, 2005, final
transportation conformity rule that addressed requirements for
PM2.5 precursors. (70 FR 24280).
    \137\ A state would also establish motor vehicle emissions
budgets for an area's attainment year. Those budgets would be the
motor vehicle emissions that the SIP establishes as being necessary
to attain the NAAQS.
    \138\ If an area includes re-entrained road dust in the motor
vehicle emissions budget, the latest approved version of AP-42
should be used unless the EPA has approved an alternative model for
the area.
---------------------------------------------------------------------------

4. Geographic Coverage of Emission Sources for RFP
    The EPA is proposing that the RFP demonstration to be included with
a state's PM2.5 nonattainment area plan must include
emissions only for sources located in the nonattainment area, and not
from an area larger than the nonattainment area. This policy approach
differs from the remanded 2007 PM2.5 implementation rule.
This section describes the evolution of policy on a similar RFP issue
in the ozone NAAQS implementation program, and it discusses the
reasoning behind this revised approach for PM2.5.
    In the preamble to the remanded 2007 PM2.5
Implementation Rule, the EPA allowed states to incorporate reductions
of NOX and SO2 emissions up to 200 km from
outside the nonattainment area (and potentially for reductions of VOC
or ammonia) into their RFP plan when certain conditions were met. This
policy was included in the 2007 PM2.5 Implementation Rule in
part to be consistent with a similar RFP policy for NOX and
VOC that was included in the November 2005 Phase 2 ozone NAAQS
implementation rule which provided guidance for states on implementing
the 1997 ozone NAAQS.\139\
---------------------------------------------------------------------------

    \139\ See Phase 2 Ozone Implementation rule, 70 FR 71612
(November 29, 2005).
---------------------------------------------------------------------------

    Under the policy in the 2007 PM2.5 NAAQS implementation
rule, if a state intended to include emissions reductions from outside
the nonattainment area in the RFP plan, the state would need to take on
the additional work associated with developing: (i) An expanded
baseline emissions inventory for the entire geographic area (i.e., the
nonattainment area plus the additional area outside the nonattainment
area) that characterizes emissions for all stationary, area and mobile
sources (rather than for just a select few stationary sources) in the
overall area; and, (ii) a projected attainment year inventory for this
expanded area outside the boundaries of the designated nonattainment
area. By requiring inclusion of all types of sources in these
``expanded area'' emissions inventories, the EPA intended for this
approach to reflect the projected net emissions reductions in this area
(the difference between the ``expanded area'' base year inventory and
the projected attainment year inventory). However, it should be noted
that development of these more extensive inventories would likely have
involved a substantial amount of additional time and resources. In
addition, the state would have needed to have provided information
supporting its decision regarding how far outside the nonattainment
area the RFP inventory should extend. While this ``outside the
nonattainment area'' RFP approach was theoretically available to states
in developing their PM2.5 attainment plans due in 2008,
there were no states to the agency's knowledge that elected to follow
this approach.

    Both the 2005 Phase 2 ozone implementation rule and the 2007
PM2.5 Implementation Rule were challenged on several issues.
With regard to the Phase 2 ozone implementation rule, the EPA granted a
petition for reconsideration and ultimately issued a final notice of
reconsideration in June 2007. In November 2008, the U.S. Court of
Appeals for the DC Circuit heard oral argument concerning multiple
petitions for judicial review of the Phase 2 ozone rule and the notice
of reconsideration. One of the issues in this case involved whether
compliance by EGUs with a regional emissions trading program could be
considered to meet the RACT requirement for those sources located in a
nonattainment area. In its July 2009 decision, the court emphasized
that: ``the RACT requirement calls for reductions in emissions from
sources in the area; reductions from sources outside the nonattainment
area do not satisfy the requirement . . . Accordingly, participation in
the NOX SIP call would constitute RACT only if participation
entailed at least RACT-level reductions in emissions from sources
within the nonattainment area.''
    In light of this court decision, the EPA has determined that the
best reading of the statute would be to interpret the term ``sources in
the area'' in the same manner where it appears in different
nonattainment provisions for ozone. The term appears in CAA section 182
(requirements for ozone nonattainment areas) with regard to RFP as well
as RACT. The decision on the Phase 2 ozone rule found that section
182(b)(2) requires that a SIP must provide for implementation of RACT
(under section 172(c)) for emissions sources ``in the area,'' meaning
in the nonattainment area. Similarly, the EPA believes that when
section 182(b)(1)(A)-(B) defines baseline emissions for RFP as ``the
total amount of actual VOC or NOX emissions from all
anthropogenic sources in the area,'' this also means sources in the
nonattainment area.
    With regard to the 2007 PM2.5 Implementation Rule, the
EPA received a petition for reconsideration in June 2007 that raised
objections on several issues. One such issue dealt with the EPA's
interpretation of the statutory RFP requirements to allow a state to
take ``credit'' for emissions reductions from outside the nonattainment
area when addressing RFP in its attainment plan.\140\ The EPA granted
the petition for reconsideration on this issue in 2010, after the D.C.
Circuit issued its decision on the Phase 2 Ozone Implementation
Rule.141 142
---------------------------------------------------------------------------

    \140\ This same petition raised concerns regarding the criteria
used to determine the economic feasibility of controls being
considered for RACT for the 1997 PM2.5 NAAQS. See
``Petition for Reconsideration,'' filed by Paul Cort, Earthjustice,
on behalf of the American Lung Association, Medical Advocates for
Healthy Air, Natural Resources Defense Council, and the Sierra Club
(June 25, 2007). A copy of the petition is in the docket for this
action.
    \141\ Letter dated May 13, 2010, from Gina McCarthy to David S.
Baron and Paul Cort, Earthjustice. A copy of the letter is located
in the docket for this action.
    \142\ See NRDC v. EPA, 571 F.3d 1245 (D.C. Cir. 2009).
---------------------------------------------------------------------------

    Specifically, the EPA believes that the DC Circuit's interpretation
of the phrase ``sources in the area'' applies to RACT and RFP
requirements for both the ozone NAAQS and the PM2.5 NAAQS.
In particular, for PM2.5, the statutory language at section
171(1) defines RFP in terms of ``reductions in emissions'' required in
an attainment plan, which the EPA interprets as being directly linked
to the baseline emissions inventory for sources located in a
PM2.5 nonattainment area. The baseline emissions inventory
is the foundation for the attainment plan. The emissions inventory
requirement of section 172(c)(3) explicitly requires that the
attainment plan inventory include all sources of the relevant
pollutants ``in such area,'' which is a clear reference to the
designated nonattainment area. Given that the baseline inventory must
reflect the emissions ``in such area,'' and that this inventory
provides the starting point for a state's RFP analysis, in which the
state must calculate generally linear progress in emissions reductions
that will lead to attainment of the NAAQS in the area, the EPA believes
it is appropriate that a state should focus on sources located within
the nonattainment area when conducting its analysis to determine the
annual emissions reductions necessary for demonstrating RFP.
    The EPA believes that the most appropriate approach with regard to
the geographic area required to be covered for demonstrating RFP in a
PM2.5 attainment plan also should be limited to the
nonattainment area for two other reasons. First, EPA believes that it
makes policy sense for the PM2.5 implementation rule
approach to be consistent with the approach in the ozone implementation
rule. In the past, a number of areas have been designated as
nonattainment for both standards, and the nonattainment area boundaries
often are the same. For such areas, a common policy approach for the
geographic area covered by the RFP plan will be more efficient to
implement and would be expected to be less burdensome for the air
agency than if the geographic areas covered by RFP plans for the two
pollutants differed.
    Second, a policy allowing the geographic area of the RFP plan to be
larger than the nonattainment area would conflict with a key provision
of subpart 4 which requires annual incremental reductions in emissions
from sources within the nonattainment area. Under subpart 4, an area
that fails to attain the standard by the Serious area attainment date
is then subject to the provisions of section 189(d). Section 189(d)
specifies that the state must submit a plan revision within 12 months
which provides for ``an annual reduction in PM10 or
PM10 precursor emissions within the area of not less than 5
percent of the amount of such emissions as reported in the most recent
inventory prepared for such area'' (emphasis added). The EPA does not
believe the rule should include an RFP policy approach which would not
be consistent with section 189(d).
    After reconsideration of the approach to RFP that was opposed in
the petition for reconsideration of the 2007 PM2.5
Implementation Rule, and in light of the DC Circuit decision on the
Ozone Phase 2 Implementation Rule, the EPA believes the best reading of
the statute is that the CAA does not allow for a state to include
emissions reductions from sources outside a nonattainment area when
developing the plan to meet the CAA section 172(c)(2) RFP requirements
for a PM2.5 nonattainment area. The EPA seeks comment on
this proposed approach.
5. Other RFP Considerations
    In general, the EPA seeks to ensure that PM2.5
nonattainment areas that are shared by more than one state or tribe
meet RFP requirements as a whole. States and tribes that share a
nonattainment area should therefore consult with one another to develop
the RFP analysis and control strategy implementation schedule for the
area as a whole. Such states and tribes should work with the EPA region
or regions that oversee them to confirm that their collective approach
is appropriate for RFP.
    The EPA's proposed approach for states to meet the RFP requirement
is designed to ensure emissions reductions will yield incremental
improvements in air quality on the path to attainment, while being
sufficiently flexible to accommodate the range of control strategies
necessary to address the complex mixtures of pollutants comprising
PM2.5 in different areas. The EPA seeks comment on all of
its proposed requirements and options for

RFP plans and analyses for Moderate PM2.5 attainment plans.

G. Quantitative Milestones

1. Statutory Requirements and Existing Guidance
    Section 189(c)(1) requires that a PM10 NAAQS attainment
plan submission has ``quantitative milestones which are to be achieved
every 3 years until the area is redesignated to attainment and which
demonstrate reasonable further progress . . . toward attainment by the
applicable date.'' Section 189(c)(2) further requires that, within 90
days of each milestone, each affected state must submit a demonstration
that all measures to assure RFP have been implemented and that the
quantitative milestone has been met. Thus, the CAA imposes requirements
upon states not only to make ``reasonable further progress'' toward
attainment, but also to identify objective means (i.e., quantitative
milestones) by which to measure this reasonable further progress every
3 years, and to submit them as part of the attainment plan for the
nonattainment area. In addition, according to section 189(c)(2), states
must, within 90 days of the passage of each such milestone, submit to
the EPA a demonstration that control measures have been implemented
according to the approved RFP plan schedule and the milestone has been
met.
    The EPA has previously described its interpretation of the
requirements under section 189(c) for the PM10 NAAQS in the
General Preamble and the Addendum and believes that these
interpretations should also apply both in developing plans that
demonstrate RFP and include appropriate quantitative milestones, and in
demonstrating that those milestones have been met for the
PM2.5 NAAQS.143 144 The EPA's guidance in the
Addendum also noted that: ``Section 189(c) provides that the
quantitative milestones submitted by a State for an area also must be
consistent with RFP for the area. Thus, EPA will determine an area's
compliance with RFP in conjunction with determining its compliance with
the quantitative milestone requirement. Because RFP is an annual
emission reduction requirement and the quantitative milestones are to
be achieved every 3 years, when a state demonstrates an area's
compliance with the quantitative milestone requirement, it should also
demonstrate that RFP has been achieved during each of the relevant 3
years.'' \145\
---------------------------------------------------------------------------

    \143\ See the Federal Register published on April 16, 1992,
General Preamble (57 FR 13498 and 13539).
    \144\ See the Federal Register published on August 16, 1994,
Addendum to General Preamble (59 FR 41998, 42015, 42016 and 42017).
    \145\ Ibid.
---------------------------------------------------------------------------

    The EPA's existing guidance in the Addendum with respect to the
quantitative milestone requirements of CAA section 189(c) thus includes
several important features: (i) That the control measures comprising
the RFP plan should be implemented and in place to meet the statutory
quantitative emissions reductions milestone requirement; (ii) that it
is reasonable for the 3-year periods for quantitative milestones to run
from the statutory due date for the Moderate area attainment plan
submission; and, (iii) that the precise form that the quantitative
milestones should take is not specified, but the state must choose
milestones that will allow it to quantify or measure, track and report
progress adequately and objectively.
    The EPA's proposed approach to identifying quantitative milestones
for any Moderate PM2.5 nonattainment area and demonstrating
compliance with the milestones is generally consistent with the
existing guidance, as described in the following sections.
2. Proposed Approach
    The statute at section 189(c) is clear that quantitative milestones
must be achieved every 3 years, however it does not make clear the
starting date for counting the 3 year periods. In the General Preamble,
the agency proposed that quantitative milestones must be achieved every
3 years starting from the attainment plan submission due date (i.e.,
because the Moderate area attainment plan is due no later than 18
months after designation of the area, the first set of milestones would
need to be achieved 4.5 years after the area's designation) until the
attainment date.\146\ The EPA proposes to maintain this approach for
the PM2.5 NAAQS. Specifically, the EPA proposes that the
attainment plan for a Moderate area that can demonstrate attainment by
the statutory Moderate area attainment date must identify appropriate
quantitative milestones to be achieved by 4.5 years following
designation of the area. For a Moderate area that cannot practicably
attain the relevant PM2.5 NAAQS within the statutory
timeframe for a Moderate area, the EPA proposes that a state must
submit two sets of quantitative milestones--one set to be achieved at
year 4.5 from designation and the second set to be achieved at year 7.5
from designation. The EPA believes that this proposed requirement will
help to ensure that the state maintains progress toward bringing the
area into attainment during the period in which such area is
reclassified to Serious, the state works to develop a Serious area
attainment plan for the area, and the EPA approves it. Pursuant to the
statute, the EPA must reclassify a Moderate area for which a state
submits an attainment impracticability demonstration within 18 months
after the Moderate area attainment plan due date, or no later than 3
years after the date of designation of the area. Even under a scenario
in which the state develops and submits a Serious area attainment plan
18 months after being reclassified to Serious, the milestone date of
4.5 years after designation would likely come and go before the area
had a new set of approved quantitative milestones with which to
demonstrate compliance. Similarly, the milestone date of 7.5 years
after designation could also come and go before the EPA is able to
fully approve the Serious area plan and any quantitative milestones
contained therein. Because of the timing of the various steps involved
in reclassifying a Moderate area to Serious and a state developing a
new Serious area plan, the EPA believes that requiring a state to
identify quantitative milestones that the area must achieve 4.5 years
and 7.5 years after designation as elements of its Moderate area
attainment plan is reasonable and seeks comment on this proposed
requirement.
---------------------------------------------------------------------------

    \146\ General Preamble, 57 FR 13498 (April 16, 1992), at page
13539.
---------------------------------------------------------------------------

    The EPA is also proposing that the quantitative milestones
contained in the attainment plan for a Moderate nonattainment area must
be constructed such that they can be tracked, quantified and/or
measured adequately in order for the state to meet its milestone
reporting obligations, which come due 90 days after a given milestone
date. In the Addendum, the EPA suggested some possible metrics that
``support and demonstrate how the overall quantitative milestones
identified for an area may be met,'' such as percent implementation of
control strategies, percent compliance with implemented control
measures, and adherence to a compliance schedule. This list was not
exclusive or exhaustive but reflected the EPA's view that the purpose
of the quantitative milestone requirement is to provide an objective
way to assess that the state is making the necessary progress towards
attainment in the area by the applicable attainment date.\147\ The EPA
continues to believe that the quantitative milestone requirement

should be interpreted to allow states to devise milestones that are
suitable for the specific facts and circumstances of the attainment
plan for a particular area, so long as they provide an objective means
to measure RFP.
---------------------------------------------------------------------------

    \147\ Addendum to the General Preamble, 59 FR 41998 (August 16,
1994), at page 42016.
---------------------------------------------------------------------------

    The EPA therefore proposes to require that states select the
quantitative milestones that are appropriate and quantifiable and that
will provide for objective evaluation of progress toward attainment in
their Moderate PM2.5 nonattainment area, whether the area
can practicably attain the PM2.5 NAAQS by the statutory
attainment date or not. For this approach, the EPA is not proposing to
require that such quantitative milestones must take any particular
form, merely that they provide a means to evaluate progress (i.e.,
demonstrate RFP) meaningfully. The EPA, in its attainment plan approval
process, will determine if the specific quantitative milestones
developed by the state for a specific nonattainment area satisfy the
statutory requirements. The EPA recommends that states confer with
their respective EPA regional office to develop appropriate
quantitative milestones. See proposed 40 CFR 51.1013(a)(1).
    In addition to this general proposed approach for selecting
quantitative milestones for a Moderate nonattainment area, the EPA is
proposing and seeks comment on a requirement that, at a minimum, states
must include in all attainment plans for Moderate PM2.5
nonattainment areas a metric to confirm that all control measures
identified and adopted as RACM and RACT for the area have been fully
implemented within 4 years of designation. This metric specifically
derives from the statutory provision that applies to all Moderate areas
and thus represents a milestone that all Moderate areas must meet
regardless of whether it is listed explicitly as an individual
milestone. The EPA believes it would be appropriate to include it as a
metric that any state with a Moderate nonattainment area would need to
demonstrate compliance with when they submit their milestone report as
described below, and thus seeks comment on this proposal.
3. Milestone Report Submittal
    Under the quantitative milestone requirement of section 189(c)(2),
a state must demonstrate to the EPA that the RFP plan for the area and
its approved milestones are being met within 90 days after the
milestone due date. The EPA then has 90 days to determine whether or
not a state's demonstration is adequate. Specifically, section
189(c)(2) requires that: ``Not later than 90 days after the date on
which a milestone applicable to the area occurs, each State in which
all or part of such [nonattainment] area is located shall submit to the
Administrator a demonstration that all measures in the plan approved
under this section have been implemented and that the milestone has
been met. A demonstration under this subsection shall be submitted in
such form and manner, and shall contain such information and analysis,
as the Administrator shall require.''
    In the event a state fails to submit a milestone demonstration
report by the due date or the EPA determines that a milestone was not
met, the state must submit a SIP revision within 9 months of either the
missed reporting deadline or the EPA's determination of the state's
failure to meet a milestone. According to the statutory requirements of
section 189(c)(3), the new SIP revision must assure ``that the State
will achieve the next milestone (or attain the national ambient air
quality standard . . ., if there is no next milestone) by the
applicable date.'' If a state fails to make a SIP submission to correct
a failure to meet RFP expeditiously, sanctions under sections 110(m)
and 179(b) may apply. If a state is unable to correct a failure to meet
RFP, this may be evidence that the state cannot practicably attain the
NAAQS by the applicable attainment date and may serve as a basis for
reclassification of the area to Serious under the agency's
discretionary authority. See proposed 40 CFR 51.1013(c).
    Because the statute does not define the parameters of these
demonstrations, the statute grants the EPA discretion to determine the
components of the required demonstration and the form and manner for
submission. In the Addendum, the EPA offered guidance about what the
milestone report should contain: ``This report must contain technical
support sufficient to document completion statistics for appropriate
milestones. For example, the demonstration should graphically display
RFP over the course of the relevant 3 years and indicate how the
emission reductions achieved to date compare to those required or
scheduled to meet RFP and the required [quantitative] milestones. The
calculations (and any assumptions made) necessary to determine the
emission reductions to date should also be submitted. The demonstration
should also contain an evaluation of whether the PM10 NAAQS
will be attained by the projected attainment date.'' \148\ The EPA
believes this guidance is still appropriate for states demonstrating
compliance with RFP and quantitative milestones for PM2.5
NAAQS and hereby proposes under the authority of section 301(a) to
require that the milestone report submission must include the following
four components:
---------------------------------------------------------------------------

    \148\ Ibid. at 42017.
---------------------------------------------------------------------------

    First, the report must include a certification by the Governor or
Governor's designee that the state's attainment plan control strategy,
including the RFP plan, is being implemented as described in the
applicable attainment plan. Second, as described in the Addendum, the
report must contain technical support, including calculations,
sufficient to document completion statistics for appropriate milestones
and to demonstrate that the quantitative milestones have been satisfied
and how the emissions reductions achieved to date compare to those
required or scheduled to meet RFP. Third, the state must submit an air
quality screening analysis to determine if measured air quality
progress is consistent with the expected air quality improvement target
correlated with the RFP emissions reductions for the previous 3-year
period. Fourth, the report must contain an evaluation of whether the
PM2.5 NAAQS will be attained by the projected attainment
date for the area. In addition, the EPA proposes that the milestone
report must include a description and schedule for any remedial actions
the state has taken or will take to address any failure to meet a
quantitative milestone, including the implementation status of
contingency measures for failing to meet RFP in the area. See proposed
40 CFR 51.1013(b). The EPA seeks comment on these proposed components
to a milestone report.
    The EPA stated in the Addendum that the milestone report must be
submitted from the Governor or Governor's designee to the Regional
Administrator of the respective EPA Regional Office serving the
submitting state, and that the EPA will notify the state of its
determination (regarding whether or not the state's report is adequate)
by sending a letter to the appropriate Governor or Governor's designee.
The EPA believes that it would be appropriate for states to submit
milestone reports, including supporting documents, through the agency's
electronic SIP (eSIP) submission system in order to simplify the
process and reduce resource burden on all sides. The EPA seeks comment
on how electronic reporting could facilitate a state's submittal of the
required milestone report, how it could accommodate the various
narrative and

data-dependent components that the EPA is proposing be part of such a
submittal, and what particular system features might be desirable to
accommodate milestone report submissions through the eSIP system.

H. Contingency Measures

    States with PM2.5 nonattainment areas must include
contingency measures in their attainment plans consistent with section
172(c)(9). Contingency measures are additional control measures to be
implemented in the event that an area fails to meet RFP requirements or
fails to attain the PM2.5 standard by the applicable
attainment date. These measures must be fully adopted rules or control
measures that are ready to be implemented quickly upon failure to meet
RFP or failure of the area to meet the standard by its attainment date,
and such measures are required to take effect without further action by
the state or the EPA. The EPA provided extensive guidance on
contingency measures in the General Preamble and Addendum, including
the following: ``States must show that their contingency measures can
be implemented with minimal further action on their part and with no
additional rulemaking actions such as public hearings or legislative
review. After the EPA determines that a moderate PM10
nonattainment area has failed to attain the PM10 NAAQS, the
EPA generally expects all actions needed to effect full implementation
of the measures to occur within 60 days after the EPA notifies the
state of the area's failure. The state should ensure that the measures
are fully implemented as expeditiously as practicable after they take
effect.'' \149\
---------------------------------------------------------------------------

    \149\ Ibid. at 42015.
---------------------------------------------------------------------------

    The EPA does not believe that the D.C. Circuit's decision in NRDC
v. EPA affects the overall contingency measure requirements that were
finalized in the remanded 2007 PM2.5 Implementation Rule,
because section 172(c)(9) imposes the contingency measure requirement
for attainment plans for the PM2.5 NAAQS and it is not
superseded or subsumed by any specific contingency measure requirements
under subpart 4. Although section 172(c)(9) requires contingency
measures, the provision does not specify exactly what parameters such
measures must meet. The EPA has longstanding interpretations of the
statute with respect to the contingency measure requirement, both for
PM and for other pollutants, in the General Preamble and Addendum. The
EPA proposes to adopt an approach to contingency measures for the
PM2.5 NAAQS similar to that recommended in earlier EPA
guidance, but seeks comment on particular proposed approaches that
differ in important ways from earlier guidance on contingency measures
for the PM2.5 NAAQS. The EPA believes that it may be
necessary to adopt a different approach to contingency measures for
PM2.5 attainment plans due to proposed changes in
determining RFP for a PM2.5 nonattainment area and in order
to accommodate Moderate PM2.5 nonattainment areas that
cannot practicably attain the standard by the statutory Moderate area
attainment date.
    The EPA is proposing and seeking comment on the following general
requirements for contingency measures to be approvable as part of a
state's Moderate area attainment plan submission for the
PM2.5 NAAQS:
    1. Contingency measures must be fully adopted rules or control
measures that are ready to be implemented quickly upon a determination
by the Administrator of the nonattainment area's failure to meet RFP or
failure to meet the standard by its attainment date.
    2. The state's attainment plan submission must contain trigger
mechanisms for the contingency measures, specify a schedule for
implementation, and indicate that the measures will be implemented with
minimal further action by the state or by the EPA.
    3. Contingency measures must consist of control measures that are
not otherwise included in the control strategy for the attainment plan.
    4. Contingency measures must provide for emissions reductions
approximately equivalent to 1 year's worth of reductions needed for
RFP, based on the overall level of reductions needed to demonstrate
attainment divided by the number of years from the base year to the
attainment year, or approximately equivalent to 1 year's worth of air
quality improvement or emissions reductions proportional to the overall
amount of air quality improvement or emissions reductions to be
achieved by the area's attainment plan. See proposed 40 CFR 51.1014.
    The EPA interprets the contingency measure requirement of section
172(c)(9) to require control measures that are not already included in
the attainment plan for other purposes, such as to meet RACM and RACT
requirements. However, suitable contingency measures may be measures
that were technologically and economically feasible for the area, but
did not qualify as RACM or RACT or additional reasonable measures for
one or more reasons. For example, a candidate contingency measure may
have been deemed technologically and economically feasible, but it was
not needed to achieve expeditious attainment in a Moderate area for
which the state could demonstrate attainment by the statutory
attainment date and therefore was not included as part of the
attainment demonstration for the area. The agency believes it is
important that states make decisions concerning contingency measures in
conjunction with their determination of the overall control strategy
for bringing the area into expeditious attainment, and that states
first must identify those control measures needed in order to
demonstrate expeditious attainment of the standards; any remaining
measures should then be considered as candidates for contingency
measures.
    For Moderate areas that cannot practicably attain the NAAQS by the
statutory attainment date, the EPA is proposing that states must
implement all control measures that they determine to be reasonable for
sources in the area. In such cases, the EPA expects that contingency
measures for such nonattainment areas would necessarily exceed the
criteria for determining whether a measure is reasonable (i.e.,
technologically and economically feasible) as described in Section IV.D
of this preamble. Such contingency measures would only be triggered in
the event the area fails to meet RFP; the EPA does not interpret the
requirement for contingency measures for failing to attain the NAAQS by
the applicable attainment date to apply to a Moderate area that a state
demonstrates cannot practicably attain the NAAQS by the statutory
attainment date. Rather, the EPA believes it is appropriate for the
state to identify and adopt contingency measures for failing to attain
the NAAQS in a timely way as part of the Serious area attainment plan
that it will develop once the EPA reclassifies such an area.
    The EPA proposes that for any Moderate PM2.5
nonattainment area, contingency measures can include measures that
achieve emissions reductions on sources located outside the
nonattainment area as well as from sources within the nonattainment
area, provided that the measures are factually demonstrated to produce
the appropriate air quality impact within the nonattainment area. The
EPA continues to believe it appropriate that a state might choose to
rely on federal measures (e.g. federal mobile source measures based on
the incremental turnover of the motor vehicle fleet each year) and
local measures already scheduled for implementation for

purposes other than meeting attainment plan requirements, such as RACM
and RACT, as meeting part or all of the contingency measure
requirements, as the purpose of the contingency measures is to provide
a cushion while the attainment plan for the area is being revised to
meet the missed attainment milestone. The EPA has approved numerous
attainment plans under an interpretation that one or more federal or
local measures that are in place and provide reductions in the year
following a failure to attain the relevant NAAQS or meet RFP in excess
of the reductions required by the attainment demonstration or RFP plan
can meet the contingency measure requirements.150 151
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    \150\ See, e.g., 62 FR 15844 (April 3, 1997); 62 FR 66279
(December 18, 1997); 66 FR 30811 (June 8, 2001); 66 FR 586 and 66 FR
634 (January 3, 2001).
    \151\ A court ruling upheld contingency measures for ozone
attainment plans that were previously required and implemented where
they were in excess of the attainment demonstration and RFP SIP. See
LEAN v. EPA, 382 F.3d 575 (5th Cir., 2004).
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    The EPA recognizes that some states have historically relied on
emissions reductions achieved through the implementation of control
measures in excess of what was determined to be necessary to meet RFP
in certain PM2.5 nonattainment areas in order to satisfy the
contingency measure requirement in such areas. The EPA believes that
this approach is reasonable for Moderate PM2.5 nonattainment
areas that can demonstrate attainment by the statutory attainment date,
as the state would calculate the emissions reductions needed for RFP
separately from the control strategy determination for such an area.
However, crediting an area for ``excess'' emissions reductions to
satisfy the contingency measure requirement would not be possible for a
Moderate area that cannot practicably attain by the statutory
attainment date under the EPA's proposed approach for calculating RFP
for such areas, as RFP would be calculated directly from the projected
emissions reductions from all control measures identified for the area
(as RACM and RACT or additional reasonable measures), such that there
would be no difference between emissions reductions estimated from
control measures and those estimated for demonstrating RFP.
    As mentioned earlier, contingency measures should represent a
portion of the actual emissions reductions necessary to bring about
attainment in the area. Consistent with the EPA's past approach for
contingency measures for PM2.5 nonattainment areas, the EPA
proposes to require that the emissions reductions anticipated by
imposition of the contingency measures must be equal to approximately 1
year's worth of emissions reductions while the state is revising its
attainment plan for the area. The EPA has historically applied a policy
of equating 1 year's worth of emissions reductions for contingency
measures with those annual reductions determined to be necessary to
achieve RFP for the area, unless the state demonstrates that some
smaller reduction is appropriate. As described in Section IV.F of this
preamble, the EPA is proposing an approach for interpreting the
statutory RFP requirement that would require demonstrating RFP based on
reductions from sources located inside the nonattainment area. Keeping
with the historic linkage between RFP and contingency measures, the EPA
is also proposing and seeking comment on a similar approach for
calculating 1 year's worth of emissions reductions for purposes of
adopting appropriate contingency measures. That is, the EPA's proposed
approach for determining the level of emissions reductions for
contingency measure purposes is to calculate the annual reductions in
emissions of direct PM2.5 and PM2.5 precursors
needed from sources located inside the nonattainment area. The EPA
seeks comment on this proposed approach.
    The CAA requires that states must implement contingency measures
after the EPA determines that the area has either failed to meet RFP
requirements, or failed to attain the standards by the applicable
attainment date. The purpose of the contingency measure provision is to
ensure that corrective measures are put in place automatically at the
time that the EPA makes its determination that an area has either
failed to meet RFP or failed to meet the standard by its attainment
date. The EPA is required to determine within 90 days after receiving a
state's milestone demonstration, and within 6 months after the
attainment date for an area, whether these requirements have been met.
The consequences for states with areas that fail to attain the NAAQS or
to meet RFP are described in section 179(d) of the CAA and discussed in
Section V of this preamble.
    As noted earlier in this section, the EPA proposes to require that
states must submit contingency measures at the same time as the rest of
the Moderate area attainment plan elements, i.e., within 18 months
after designation. Section 172(b) requires the Administrator to
``establish a schedule according to which the State containing such
[nonattainment] area shall submit a plan or plan revision (including
the plan items) meeting the applicable [subpart 1 nonattainment plan]
requirements. . . Such schedule shall, at a minimum, include a date or
dates, extending no later than 3 years from the date of the
nonattainment designation . . .'' The EPA believes it is reasonable to
require the submittal of contingency measures for Moderate
PM2.5 nonattainment areas on the same schedule as the other
Moderate area attainment plan requirements because of the close
relationship between an area's control strategy, RFP analysis and
selection of quantitative milestones, and contingency measures. The EPA
seeks comment on this proposed due date for submission of contingency
measures.

I. Attainment Dates

1. Statutory Requirements
    Section 188 establishes the attainment dates for Moderate and
Serious PM10 nonattainment areas, which also apply to
Moderate and Serious PM2.5 nonattainment areas. Section
188(c)(1) provides that for a Moderate area, ``the attainment date
shall be as expeditiously as practicable but no later than the end of
the sixth calendar year after the area's designation as
nonattainment.'' The EPA has the responsibility for determining whether
a nonattainment area has attained the standard by its applicable
attainment date. Section 179(c)(1) requires the EPA to make
determinations of attainment no later than 6 months following the
attainment date for the area. Under section 179(c)(2), the EPA must
publish a notice in the Federal Register identifying those areas which
failed to attain by the applicable attainment date. The statute further
provides that the EPA may revise or supplement its determination of
attainment for the affected areas based upon more complete information
or analysis concerning the air quality for the area as of the area's
attainment date.
    Section 179(c)(1) provides that the EPA is to base the attainment
determination for an area upon an area's ``air quality data as of the
attainment date.'' The EPA will make the determination of whether an
area's air quality is meeting the PM2.5 NAAQS by the
applicable attainment date based upon data gathered from the air
quality monitoring sites which have been entered into the EPA's Air
Quality System (AQS) database. No special or additional attainment plan
submission will be required from the state for this determination.
    A Moderate PM2.5 nonattainment area's air quality status
is determined in accordance with Appendix N of 40 CFR

part 50. To show attainment of the current 24-hour and annual standards
for PM2.5, the most recent 3 consecutive years' data prior
to the area's attainment date must show that PM2.5
concentrations over the prior 3-year period are at or below the levels
of the standards. A complete year of air quality data, as described in
part 50, Appendix N, is comprised of all 4 calendar quarters with each
quarter containing data from at least 75 percent of the scheduled
sampling days.
    The EPA will begin processing and analyzing data related to the
attainment of Moderate PM2.5 nonattainment areas after the
applicable attainment date for the affected areas. Current EPA
regulations, under 40 CFR part 58, set the deadline for the state to
submit air quality data into the AQS database as no later than 90 days
after the end of the calendar year.
    While the EPA may determine that an area's air quality data
indicates that an area may be meeting the PM2.5 NAAQS for a
specified period of time, this does not eliminate the state's
responsibility under the Act to adopt and implement an approvable
attainment plan. If the area's monitored data indicates that the area
is factually attaining the NAAQS, however, the EPA may issue a ``clean
data determination'' which will suspend the obligation of the state to
submit the elements of the attainment plan for the area that are
related to planning requirements, as discussed in Section IX.C of this
preamble. If the EPA determines that an area has attained the standard
as of its attainment date, the area will remain classified as
nonattainment until the state has requested, and the EPA has approved,
redesignation to attainment for the area.
    In order for an area to be redesignated as attainment, the state
must comply with the five requirements listed under section
107(d)(3)(E) of the CAA. Briefly, this section requires that:
     The EPA has determined that the area has met the
PM2.5 NAAQS;
     The EPA has fully approved the applicable state
implementation plan;
     The improvement in air quality is due to permanent and
enforceable reductions in emissions;
     The EPA has fully approved a maintenance plan for the
area; and,
     The state(s) containing the area or portions of the area
have met all applicable requirements under section 110 and part D.
2. Proposed Approach
    As noted earlier, section 188(c)(1) states that for a Moderate
area, ``the attainment date shall be as expeditiously as practicable
but no later than the end of the sixth calendar year after the area's
designation as nonattainment.'' For purposes of clarity, the EPA
proposes to interpret the reference to ``the area's designation'' in
this provision as meaning ``the area's effective date of designation,''
consistent with the agency's approach for implementing the 1997 and
2006 PM2.5 NAAQS and with its approach for implementing
NAAQS for other criteria pollutants under part D, title I of the CAA.
See proposed 40 CFR 51.1000. As discussed elsewhere in this preamble,
the effective date of designation is April 15, 2015, for areas
designated nonattainment in the first round of designations for the
2012 PM2.5 NAAQS. For these areas, the Moderate area
attainment date would be as expeditious as practicable, but no later
than December 31, 2021 (i.e., the end of the sixth calendar year after
designation). The EPA seeks comment on this proposed interpretation of
the date of designation of a PM2.5 NAAQS nonattainment area
and the resulting attainment date for such areas.
    As described in Sections IV.D and IV.E of this preamble, in the
case of a Moderate PM2.5 nonattainment area for which a
state can demonstrate attainment by the end of the sixth calendar year
following designation, the state must follow a two-step process for
determining the appropriate attainment date for the area. First, the
state must demonstrate through air quality modeling that the area can
attain the relevant NAAQS by the latest statutory attainment date and
determine which control measures and technologies are needed for the
area to attain by that date. Second, the state must determine whether
implementing other reasonable controls (i.e., those not needed for
attainment by the latest possible date but that are technologically and
economically feasible) can cumulatively advance the attainment date for
the area by at least 1 year. In the event that a state determines that
the area can attain the relevant NAAQS earlier through the application
of other measures, the state must propose the earlier date as part of
the attainment plan submission for the area. When the EPA takes action
to approve the different elements of the attainment plan for the area,
one of the elements that the agency will take action on will be the
state's proposed attainment date for the area. If the EPA approves an
attainment date for the area that is earlier than the latest date
allowed by statute, then the applicable attainment date for the area
will be the approved date. See proposed 40 CFR 51.1004(a)(1)(i). If the
area ultimately needs additional time to attain the relevant NAAQS, the
state may request an attainment date extension for the Moderate
nonattainment area under section 188 as long as certain conditions are
met, as described in Section IV.J.
    The EPA's approach to approving an attainment date for a
PM2.5 nonattainment area will be different for a Moderate
area that cannot practicably attain the relevant PM2.5 NAAQS
by the end of the sixth calendar year after designation. Given that the
agency will reclassify any such area to Serious and thereby trigger
additional Serious area requirements for the area, the EPA will approve
an attainment date for the area when it takes action on the Serious
area attainment plan submitted for the area. In the interim, before the
EPA takes action to reclassify the area, the statutory Moderate area
attainment date will continue to apply to such an area. See proposed 40
CFR 51.1000 and 51.1004(a)(1)(ii). When the EPA reclassifies the area,
then the presumptive attainment date for the area will be as
expeditious as practicable, but no later than the end of the tenth
calendar year following designation. A complete discussion of Serious
area attainment dates is provided in Section VI.H of this preamble.

J. Attainment Date Extensions

1. Statutory Requirements
    The CAA under subpart 4 provides the EPA with authority to grant
extensions of the attainment date for a Moderate area that otherwise
could be found to have failed to attain the relevant PM2.5
NAAQS, if the area can meet specific statutory criteria related to the
implementation of measures contained in the attainment plan for the
area, and to monitored air quality in the area. Specifically, under
section 188(d), a state may apply to the EPA for an extension of a
Moderate area's attainment date of one additional year (the ``Extension
Year'') if ``(1) the state has complied with all requirements and
commitments pertaining to the area in the applicable implementation
plan; and (2) no more than one exceedance of the 24-hour [NAAQS] level
for PM10 has occurred in the area in the year preceding the
Extension Year, and the annual mean concentration of PM10 in
the area for such year is less than or equal to the standard level.''
Section 188(d) limits the number of 1-year extensions that the EPA may
grant for a Moderate nonattainment area to two.
    The provisions of section 188(d) thus allow a state an opportunity
to demonstrate that a Moderate area should continue to be classified as

Moderate and not be reclassified to Serious even if the area exceeded
the level of the applicable PM2.5 NAAQS in one or both of
the 2 calendar years preceding the year in which the area is otherwise
required to attain the NAAQS. Although section 188(d) provides the
criteria for such an extension, the EPA believes that there are some
ambiguities in the statutory language that warrant interpretation and
clarification through regulations for the PM2.5 NAAQS. The
EPA is thus proposing a preferred interpretation of section 188(d) to
provide clarity to states about how and when they may qualify for a
Moderate area attainment date extension for purposes of the
PM2.5 NAAQS.
2. Proposed Interpretations of Attainment Date Extension Criteria
    With respect to the criterion in section 188(d)(1) that requires
that ``the state has complied with all requirements and commitments
pertaining to the area in the applicable implementation plan,'' the EPA
proposes to interpret this provision to mean that the state has
implemented the control measures in the SIP submission it made to
address the attainment plan requirements for the applicable
PM2.5 NAAQS, and not to require the area to have a fully
approved attainment plan that meets all of the CAA's requirements for
Moderate areas. This proposed interpretation is based on the plain
language of section 188(d) that does not explicitly require that the
state comply with all requirements pertaining to the area in the CAA,
but merely requires that the state comply with all requirements in the
applicable SIP.\152\ In other words, the EPA believes that section
188(d)(1) should be interpreted to mean that so long as the state has
submitted the necessary attainment plan for the area for the applicable
PM2.5 NAAQs and is implementing the control measures in the
submission, the fact that the EPA has not yet acted on such submission
to make it an approved part of the applicable SIP should not be a
barrier to the state obtaining an extension of the attainment date
under section 188(d)(1). For the same reason, the EPA also proposes to
read this provision not to bar an extension if all or part of an area's
Moderate area plan is disapproved or has been promulgated by the EPA as
a federal implementation plan (FIP). In the case that the ``applicable
implementation plan'' is a FIP (or combination of SIP and FIP), then
the EPA proposes that the state must have implemented the control
measures contained therein in order to meet the statutory criteria at
section 188(d)(1) for a Moderate area attainment date extension. The
EPA seeks comment on this proposed interpretation of section 188(d)(1).
See proposed 40 CFR 51.1005(a)(2).
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    \152\ This interpretation as applied to section 188(e) for
Serious area attainment date extensions was upheld by the Ninth
Circuit Court of Appeals in Vigil v. Leavitt, 366 F.3d 1025, amended
at 381 F.3d 826 (9th Cir. 2004).
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    The EPA also proposes and seeks comment on an alternative
interpretation of section 188(d)(1) that would require a state to have
a Moderate area attainment plan fully approved by the EPA as meeting
the applicable attainment plan requirements under sections 172 and 189
for a Moderate PM2.5 nonattainment area before the state
obtains an extension. Given that Moderate area attainment plans are due
18 months from the date of designation, and that RACM and RACT must be
implemented within 4 years after designation, states should have
sufficient time under the statutory schedule to satisfy all applicable
requirements in advance of seeking a Moderate area attainment date
extension. Under this alternative approach, the EPA proposes that a
state subject to a FIP (or SIP and FIP) for a Moderate PM2.5
nonattainment area could qualify for an attainment date extension for
the area if it had implemented all requirements and commitments of the
FIP (or SIP and FIP), as the FIP (or SIP and FIP) would be the
``applicable implementation plan'' for the area. Although this
alternative interpretation could also be a reasonable reading of this
criterion of section 188(d)(1), the EPA considers it less appropriate
than the preferred interpretation because this approach could foreclose
states from obtaining an otherwise appropriate extension merely because
of logistical and timing considerations that might have prevented the
EPA from acting on the state's attainment plan by the requisite point
in time. Nevertheless, the EPA seeks comment on this alternative
interpretation of section 188(d)(1).
    The second criterion that states must meet to qualify for an
extension relates to the monitored ambient air in a nonattainment area
in the year prior to the attainment date for the area. If a state has
met the requirements of section 188(d)(1), the EPA may grant an
extension of a Moderate area's attainment date if the state also
satisfies the requirements of section 188(d)(2) that ``no more than one
exceedance of the 24-hour national ambient air quality standard level
for PM10 has occurred in the area in the year preceding the
Extension Year, and the annual mean concentration of PM10 in
the area for such year is less than or equal to the standard level.''
Again, the EPA may grant up to two such 1-year extensions and thus this
criterion would apply to the calendar year prior to the applicable
attainment date and to the Extension Year, in the case of a second
extension.
    The EPA believes that the references to the ambient air quality
standards in section 188(d)(2) are ambiguous in two significant ways in
the context of the PM2.5 NAAQS implementation. First, the
statutory language explicitly sets ambient air quality conditions for
an attainment date extension in terms that relate factually to the 24-
hour PM10 NAAQS that was in effect at the time of the 1990
Amendments of the CAA, which has a statistical form that is
substantially different from the 24-hour PM2.5 NAAQS.
Specifically, the form of the 24-hour PM10 NAAQS allows for
no more than one ``exceedance'' of the standard per year on average
over 3 years, and if there is more than one such exceedance on average
over 3 years the area is violating the NAAQS. Thus, as a means of
limiting extensions to areas that are close to attaining the NAAQS in
the calendar year prior to the applicable attainment date, section
188(d)(2) imposes the criterion of having ``no more than one exceedance
of the 24-hour . . . standard level'' as a way of demonstrating that a
nonattainment area has ``clean data'' for the year prior to the
attainment date.\153\ This statutory language does not translate
readily to the PM2.5 NAAQS, which postdate the creation of
section 188(d) and are not structured with the same mathematical form.
For example, the 2006 24-hour PM2.5 NAAQS incorporates a 3-
year average of the 98th percentile form, which means that an area with
valid monitored ambient readings every day (or almost every day) could
have seven readings above the numerical level of the standard (i.e.,
``exceedances'') in any given year and still have ``clean data'' for
that year. A literal interpretation of section 188(d)(2) to permit only
one exceedance of the 24-hour PM2.5 NAAQS, rather than the
number of exceedances that is relevant for purposes of determining
attainment of such NAAQS, is illogical. In light of the different form
of the PM2.5 NAAQS, the statutory language of section
188(d)(2) is thus ambiguous in how it should apply to implementation of
the 24-hour PM2.5 NAAQS.
---------------------------------------------------------------------------

    \153\ The 24-hour PM10 NAAQS, set at 150 [mu]g/m\3\,
cannot be exceeded more than once per year on average, over 3 years.
---------------------------------------------------------------------------

    Additionally, the language of section 188(d)(2) may be considered
ambiguous

as to how it should apply to the PM2.5 NAAQS to the extent
that it does not specify whether the air quality criteria for an
attainment date extension apply equally for a Moderate area designated
nonattainment for both the 24-hour and annual standards, or for just
one of the standards. In practice, most areas designated nonattainment
for the PM10 NAAQS following passage of the 1990 CAA
Amendments were designated nonattainment only for the 24-hour
PM10 NAAQS, with a few designated for only the annual
PM10 NAAQS or for both the 24-hour and the annual
PM10 NAAQS. The 24-hour NAAQS has served as the
``controlling'' (i.e., functionally more stringent) PM10
standard, such that the agency's experience to date in granting
PM10 Moderate area attainment date extension requests has
been limited to extending the attainment date for the 24-hour
PM10 NAAQS.\154\
---------------------------------------------------------------------------

    \154\ For examples of the EPA actions to extend attainment dates
for Moderate PM10 areas, see 61 FR 20730 (May 8, 1996),
61 FR 66602 (December 18, 1996), and 66 FR 32752 (June 18, 2001).
---------------------------------------------------------------------------

    The situation is distinctly different for PM2.5
nonattainment areas, as the specific facts and circumstances of a
particular area may warrant a nonattainment designation for either the
24-hour standard or the annual standard, but often not both. In most
cases, for instance, the current nonattainment areas for
PM2.5 are designated either for the 1997 annual NAAQS or for
the 2006 24-hour NAAQS, but not both.\155\ For example, the EPA
recently promulgated designations for areas violating only the annual
PM2.5 NAAQS revised in 2012, not the 24-hour NAAQS which was
retained at the level established during the 2006 p.m. NAAQS review. If
a PM2.5 nonattainment area is designated only for the 24-
hour or only for the annual PM2.5 NAAQS, this situation
raises the question of how section 188(d)(2) air quality criteria for
both standards should apply to such a PM2.5 NAAQS
nonattainment area if the state seeks an extension of the applicable
attainment date for such area.
---------------------------------------------------------------------------

    \155\ Nonattainment areas designated for both the 24-hour and
annual PM2.5 NAAQS are located in central and southern
CA.
---------------------------------------------------------------------------

    Due to the ambiguities associated with applying this subpart 4
requirement to current and future PM2.5 NAAQS, the agency
believes it is important to propose a reasonable interpretation of the
statutory requirement and seek public comment on this preferred
interpretation as well as two alternative interpretations specifying
the PM2.5 standard or standards for which a state would need
to demonstrate a Moderate nonattainment area met the air quality
criteria of section 188(d)(2) in order to qualify for an attainment
date extension. The agency also believes it is important to clarify how
the air quality criteria of section 188(d)(2) apply specifically for
the 24-hour PM2.5 NAAQS. For this reason, the EPA is
proposing a preferred interpretation of section 188(d)(2) for
application to current and future PM2.5 NAAQS, and is
seeking comment on two alternative interpretations that the agency
considers less appropriate.
    The preferred proposed approach would only require a state to
demonstrate that in the year prior to the applicable attainment date
for the area, a Moderate area did not exceed the level of (i.e., had
clean data for) the specific PM2.5 NAAQS for which the area
is designated nonattainment (the ``applicable NAAQS'') and for which
the state is seeking the extension of the attainment date. The second
approach, on which the EPA seeks comment, would require that a state
demonstrate that in the year prior to the applicable attainment date
for an area, the Moderate area did not exceed the level of the specific
PM2.5 NAAQS for which the area is designated nonattainment
(the applicable NAAQS), and did not exceed the most stringent level of
any other PM2.5 NAAQS in effect nationally at the time the
area was designated for the applicable NAAQS. The third approach, on
which the EPA also seeks comment, would require that a state
demonstrate that in the year prior to the applicable attainment date
for an area, the Moderate area did not have more than one exceedance of
the level of the 24-hour PM2.5 standard, and that the annual
mean concentration of PM2.5 in the area for the attainment
year was less than or equal to the annual standard, regardless of the
NAAQS for which the state is seeking an attainment date extension.
    The EPA prefers the proposed interpretation (described in more
detail later in this section) for implementing the Moderate area
attainment date extension criteria of section 188(d)(2) considering the
fact that, due to the specific atmospheric conditions and source-
dependent nature of PM2.5 problems in different areas around
the country, the EPA has historically designated, and may continue to
designate, PM2.5 nonattainment areas for either the annual
or the 24-hour NAAQS. As discussed earlier, the agency's designations
processes for the 2006 revised 24-hour PM2.5 NAAQS and the
2012 revised annual PM2.5 NAAQS have each been conducted to
address only one standard individually. In addition, the current 24-
hour PM2.5 NAAQS does not have a ``one exceedance'' form of
the standard, as cited in section 188(d)(2). Nevertheless, the EPA
requests comment on the second and third interpretations of section
188(d)(2) described later in this section because they more closely
reflect the specific statutory wording.
    a. Proposed approach: the EPA preferred option. The EPA's proposed
interpretation of section 188(d)(2) would simply require that a state
demonstrate that in the year prior to the applicable attainment date
for the area, a Moderate nonattainment area had clean data for the
specific PM2.5 NAAQS for which the state was seeking an
attainment date extension (the applicable NAAQS). Under this proposed
approach, a state seeking an attainment date extension for a Moderate
nonattainment area for a 24-hour PM2.5 NAAQS would be
required to demonstrate that the area had clean data for that
particular standard in the calendar year prior to the applicable
attainment date for the area, rather than demonstrating that the area
necessarily had no more than one exceedance of the 24-hour
PM2.5 NAAQS.
    For example, under this proposed interpretation of section
188(d)(2), in the case of a state seeking an extension of the
attainment date for a Moderate area designated nonattainment for the
2006 24-hour PM2.5 NAAQS, the state would need to
demonstrate that the area had no more than the allowable number of
valid monitored readings exceeding 35[mu]g/m\3\ to meet the 98th
percentile statistical form of the standard in the year prior to the
area's attainment date. The state would not have to demonstrate that
the area also had clean data for any other PM2.5 NAAQS,
including any annual PM2.5 NAAQS or later revision of the
24-hour PM2.5 NAAQS.
    Likewise under the EPA's preferred approach, a state seeking an
attainment date extension for a Moderate nonattainment area for an
annual PM2.5 NAAQS would be required to demonstrate that the
area had clean data for that particular standard in the calendar year
prior to the applicable attainment date for the area. For example, in
the case of a state seeking an extension of the attainment date for a
Moderate area designated nonattainment for the 2012 annual
PM2.5 NAAQS, the state would need to demonstrate that the
annual mean concentration of PM2.5 at each monitor in the
area as analyzed in accordance with Appendix N to 40 CFR part 50 for
the year prior to the area's attainment date was less than or equal to
12.0 [mu]g/

m\3\. Again, under this proposed approach, the state would not have to
demonstrate that the area had clean data for any other PM2.5
NAAQS.
    Under the EPA's preferred approach, if a state were to have an area
that is designated nonattainment for both the 24-hour and the annual
PM2.5 NAAQS, with the same applicable attainment date, then
a state seeking attainment date extensions for both NAAQS would need to
meet the ambient air quality criterion for both NAAQS. The EPA notes
that this would not be a common occurrence, but under this
interpretation, these would be the only circumstances under which a
state should be required to have clean data for both NAAQS in order to
qualify for an extension of the applicable attainment date under
section 188(d)(2). If a state has a nonattainment area that is only
designated for either the 24-hour or the annual PM2.5 NAAQS,
the EPA believes that the state need only meet the air quality
criterion of section 188(d)(2) for the NAAQS relevant to the attainment
date at issue. See proposed 40 CFR 51.1005(a)(1)(ii) and (iii).
    The EPA believes this preferred interpretation of section 188(d)(2)
is appropriate for two reasons. First, as discussed above, while most
PM10 nonattainment areas were designated nonattainment for
either just the 24-hour PM10 NAAQS or for both the 24-hour
and annual PM10 NAAQS, the majority of current
PM2.5 nonattainment areas are designated for either the 24-
hour or the annual PM2.5 NAAQS, and should arguably only
need to demonstrate clean data for the NAAQS for which the area is
designated nonattainment. For those few PM2.5 nonattainment
areas designated for 24-hour and annual PM2.5 NAAQS, the EPA
believes it may also be appropriate that a state must only demonstrate
clean data for the specific NAAQS for which the state is seeking an
attainment date extension because such an approach is consistent with
the statute's overall approach to designating nonattainment areas and
implementing control strategies for each separate PM2.5
NAAQS.
    Second, as discussed earlier, the statutory language that requires
that a nonattainment area have ``no more than one exceedance of the 24-
hour'' NAAQS level reflects a statistical form for the 24-hour
PM10 standard that is different from the current form of the
24-hour PM2.5 NAAQS. This difference, and the fact that the
form could be subject to further revision in the future, leads the EPA
to conclude that it is appropriate to describe this particular
criterion more broadly so that it can apply to any 24-hour
PM2.5 NAAQS, now or in the future regardless of the specific
statistical form any such NAAQS may take. The EPA seeks comment on this
preferred proposed approach.
    b. Alternative approach 1. The EPA also seeks comment on two
alternative interpretations of section 188(d)(2). The EPA's first
alternative interpretation of section 188(d)(2) would require that a
state seeking an attainment date extension for a Moderate
PM2.5 nonattainment area would have to demonstrate that the
area met the level of the PM2.5 NAAQS for which it is
seeking the attainment date extension, as well as met the numerical
level of the most stringent PM2.5 NAAQS in effect at the
time the area was designated nonattainment. That is, under this
approach, the area would need to have clean data for the year preceding
the attainment date for the PM2.5 NAAQS for which the state
is seeking an attainment date extension and for the other
PM2.5 NAAQS that were part of the same suite of
PM2.5 standards (i.e., both the 24-hour and the annual
PM2.5 NAAQS) in effect at the time the EPA designated the
area nonattainment.
    For example, if a state seeks an extension of the attainment date
for an area designated nonattainment only for the 2012 annual
PM2.5 NAAQS, it would have to demonstrate that the annual
mean concentration of PM2.5 at each monitor in the Moderate
area as analyzed in accordance with Appendix N to 40 CFR part 50 in the
attainment year was less than or equal to 12.0 [mu]g/m\3\.
Additionally, the state would have to demonstrate that the 98th
percentile of valid 24-hour monitored readings in the area for the year
preceding the attainment date did not exceed 35 [mu]g/m\3\, the level
of the 24-hour PM2.5 NAAQS set in 2006 and retained with the
2012 p.m. NAAQS review as part of the suite of PM NAAQS, even if the
area was not designated nonattainment for the 2006 24-hour
PM2.5 NAAQS.\156\ As with the agency's preferred approach, a
state seeking an attainment date extension for a Moderate nonattainment
area for a 24-hour PM2.5 NAAQS would be required to
demonstrate that the area had clean data for that particular standard
in the calendar year prior to the applicable attainment date for the
area in accordance with the statistical form of the 24-hour
PM2.5 NAAQS, rather than demonstrating that the area had no
more than one exceedance of the 24-hour PM2.5 NAAQS.
---------------------------------------------------------------------------

    \156\ Given the rounding provisions specified in 40 CFR part 50,
Appendix N, these criteria would be satisfied if the concentrations
before final rounding are less than an annual average of 12.05
[mu]g/m\3\ and a 24-hour value of 35.5 [mu]g/m\3\.
---------------------------------------------------------------------------

    The EPA presents this first alternative interpretation of the
statute for two reasons. First, as noted earlier, the statute at
section 188(b)(2) does not specify whether the air quality criteria for
an attainment date extension apply for Moderate areas designated
nonattainment for both the 24-hour and annual PM10
standards, or for just one of the standards. Read literally, however,
the statute seems to require that an area seeking an extension of a
Moderate area attainment date for any PM10 NAAQS must be
meeting the level of both the 24-hour standard and the annual standard,
even if it was only designated for just one of the standards. Under
this interpretation of the statute for purposes of implementing the
PM2.5 NAAQS, even though an area may be designated
nonattainment for only one PM2.5 NAAQS and therefore seeking
an attainment date extension only for that particular NAAQS, it would
also have to meet the level of the other PM2.5 standards. As
explained above, the EPA does not consider this the most appropriate
interpretation of section 188(d). However, under this alternative
interpretation the agency would take the position that the other
PM2.5 standards whose level the state must show the Moderate
nonattainment area met in the year preceding its attainment date would
be the most stringent PM2.5 NAAQS in effect nationally at
the time the area was designated nonattainment. For example, if the EPA
were to strengthen the 24-hour PM2.5 standard below the
current 35 [mu]g/m\3\ prior to December 31, 2021 (the anticipated
statutory Moderate area attainment date for the 2012 PM2.5
NAAQS), then an area seeking an extension of the Moderate area
attainment date for the 2012 PM2.5 NAAQS would have to
demonstrate that the area met the most stringent 24-hour
PM2.5 NAAQS that applied at the time it was designated (35
[mu]g/m\3\), and not the less stringent 24-hour NAAQS set in 1997 (65
[mu]g/m\3\) or any more stringent standard set after designation but
before the attainment date.
    Second, as with the proposed approach to interpreting section
188(d)(2), the EPA believes it is appropriate to interpret the
statutory language regarding ``no more than one exceedance of the 24-
hour'' NAAQS level broadly to mean that the area had clean data for the
24-hour PM2.5 NAAQS, consistent with the form of the NAAQS
at issue, so that the requirement can apply to any 24-hour
PM2.5 NAAQS, now or in the future. Even if it were
appropriate to interpret section

188(d)(2) to require that a state meet the air quality criterion for
both the 24-hour and the annual PM2.5 NAAQS, the EPA
believes that the statutory provision concerning the number of
exceedances must still be read in light of the different form of the
24-hour PM2.5 NAAQS. The EPA seeks comment on this first
alternative interpretation of section 188(d)(2).
    c. Alternative approach 2. The EPA's second alternative
interpretation of section 188(d)(2) would require that a state
demonstrate that a Moderate area did not have more than one exceedance
of the applicable 24-hour PM2.5 standard level, and the
annual mean concentration of PM2.5 in the area was less than
or equal to the applicable annual PM2.5 standard level, in
the year preceding the applicable attainment date for the area. In
other words, the EPA would not interpret the air quality criterion with
respect to the 24-hour PM2.5 NAAQS in light of the
significantly different form of the PM2.5 NAAQS.
Furthermore, as with the first alternative interpretation, the
``applicable'' PM2.5 standards would be those that applied
at the time the Moderate area was designated for a given
PM2.5 NAAQS, even if the area was not designated
nonattainment for all of them. This interpretation would mean that
regardless of the form of the applicable 24-hour PM2.5
standard, the Moderate area seeking an attainment date extension could
not have more than one exceedance of the numerical level of the
applicable 24-hour standard in order to qualify for a Moderate area
attainment date extension. This requirement would be more stringent--
and in some cases considerably so--than under the preferred proposed
and first alternative interpretations, given the current statistical
form of the 24-hour PM2.5 NAAQS. Additionally, under this
reading of section 188(d)(2), any future changes to the
PM2.5 NAAQS in terms of form or averaging time would also
not be addressed, potentially creating confusion with respect to how a
PM2.5 Moderate area could qualify for an attainment date
extension in the future.
    The EPA believes that, while this interpretation of section
188(d)(2) may appear to be a straightforward reading of the statutory
language, it does not reasonably account for the important differences
between the statistical form of the PM10 and
PM2.5 NAAQS or between the EPA's longstanding convention for
designating PM10 and PM2.5 nonattainment areas
generally. The EPA therefore seeks comment on its preferred proposed
approach and two alternative approaches for interpreting the air
quality criteria of section 188(d)(2) that a state would need to
demonstrate compliance with in order for the EPA to consider granting
an extension of a Moderate PM2.5 area attainment date.
3. Proposed Process for Attainment Date Extension Request Submittals
    Regardless of which interpretation of section 188(d)(1) the EPA
finalizes as part of this rulemaking, the EPA proposes to require
states to submit sufficient information to demonstrate that they have
complied with applicable requirements and commitments in the applicable
implementation plan. This information would be needed in order for the
EPA to make a decision on whether to grant a 1-year attainment date
extension. The EPA would not be authorized to grant an attainment date
extension to an area unless the state can demonstrate that it has met
all of the requirements and commitments contained in the state's
applicable implementation plan for the area. Under the EPA's first
proposed approach for interpreting section 188(d)(1), a state would
have to demonstrate that control measures have been submitted in the
form of a SIP revision and that RACM and RACT and additional reasonable
measures for sources in the area have been implemented. Under the
agency's alternative proposal for interpreting section 188(b)(1), the
attainment plan submitted by the state would have to have been fully
approved by the EPA and the state would have to be in compliance with
any elements required under any applicable FIP for the area. In
addition, under the EPA's second proposed approach, the state would
have to demonstrate that: (i) RACM and RACT and additional reasonable
measures for sources in the area have been implemented, and (ii) the
area has made emissions reductions progress that represents RFP toward
attainment of the NAAQS and has met its quantitative milestones, and
the state has submitted a milestone compliance demonstration (milestone
report) to that effect if due. Any decision made by the EPA to extend
the attainment date for an area would be based on facts specific to the
nonattainment area at issue.
    Section 188(d) does not specify the process by which the EPA should
evaluate and act upon requests from states for an extension of the
Moderate area attainment date. However, the EPA proposes that an
attainment date extension would only be granted after the agency
provides notice in the Federal Register and an opportunity for the
public to comment. This notice-and-comment process would allow for
appropriate evaluation of the relevant criteria and facts in order to
assure that the extension is granted or denied after full evaluation.
This process also is consistent with past practice by the EPA in
granting attainment date extensions, most recently for ozone
nonattainment areas. In addition, for ease of implementation, the EPA
proposes to interpret section 188(d) to authorize the EPA to stipulate
that any extension would begin on January 1 and end on December 31 of
the extension year and these dates would not depend on when the state
submitted its request for an extension or was granted the extension by
the EPA. The EPA believes this is a reasonable approach as the
applicable attainment date for the area will either be the end of the
sixth calendar year following designation of the area, or the end of an
earlier calendar year if the state could advance attainment of the area
by at least 1 year through the implementation of extra control
measures. In addition, compliance with the relevant NAAQS will be
evaluated based on monitored data collected over a full calendar year
(i.e., over the period beginning January 1 and ending December 31), so
starting the extension year on January 1 is logical.
    Because air quality criteria are part of the conditions that must
be met in order for the EPA to grant a Moderate area attainment date
extension, the EPA proposes to require that a state seeking such an
extension must submit its complete attainment date extension request,
including any available preliminary data for the year preceding the
area's applicable Moderate attainment date, on or before the area's
attainment date. The EPA also proposes to require that the state
requesting such an extension must submit to the respective EPA Regional
Office certified ambient PM2.5 monitoring data for the year
preceding the attainment date for the area in question by no later than
February 28 of the year following the area's attainment date.
Submission of the necessary data by this date will allow the EPA to
review the state's request and take appropriate action on the request
prior to the date by which the EPA is required to make a determination
that the area failed to attain by its Moderate area attainment date,
i.e., within 6 months of the applicable attainment date (see the
discussion of reclassification in Section V of this preamble). The EPA
seeks comment on these proposed deadlines for a state to request an
extension of a Moderate area's attainment date and submit certified air
quality data as required under CAA section 188(d)(2).

    As noted earlier in this discussion of Moderate area attainment
date extensions, the statute at section 188(d) provides that a state
may seek up to two 1-year extensions of the Moderate area attainment
date if it meets the applicable criteria of sections 188(d)(1) and
188(d)(2). The statute makes no distinction between the criteria that
must be met for the first 1-year extension and the criteria for the
second 1-year extension, therefore the EPA plans to apply the same
interpretations of the statutory criteria proposed throughout this
section, including the proposed deadlines for the state to submit the
extension request and the certified air quality data, for purposes of a
state seeking a second 1-year attainment date extension for a Moderate
nonattainment area.
    The EPA seeks comment on the proposed approaches described above
for interpreting the criteria of section 188(d)(1) and 188(d)(2) and
establishing a process for states to request attainment date extensions
for Moderate areas.

V. How would a PM2.5 Moderate nonattainment area be
reclassified to Serious?

    As discussed elsewhere in this preamble, subpart 4, part D of title
I of the CAA establishes a two-tier classification system for areas
designated nonattainment for the PM2.5 NAAQS. While all
areas designated nonattainment are initially classified as Moderate,
section 188(b) describes two pathways by which the EPA has the
authority or the duty to reclassify a Moderate nonattainment area to a
Serious nonattainment area. Pursuant to section 188 (b)(1), the EPA has
general discretionary authority to reclassify from Moderate to Serious
any area that the Administrator determines cannot practicably attain
the NAAQS by the applicable Moderate area attainment date. Pursuant to
section 188(b)(2), the EPA has a mandatory duty to reclassify from
Moderate to Serious any area that fails to attain the NAAQS by the
applicable Moderate area attainment date. Both of these pathways are
more fully described below.

A. Discretionary Authority

    The EPA's discretionary authority to reclassify a Moderate area to
Serious derives from language in section 188(b)(1) of the CAA which
provides that: ``The Administrator may reclassify as a Serious
PM10 nonattainment area . . . any area that the
Administrator determines cannot practicably attain the [NAAQS] . . . by
the attainment date . . . for Moderate Areas.'' The use of this
discretionary authority thus would be triggered by the EPA making a
determination that the Moderate area in question could not practicably
attain by its statutory attainment date.
    The CAA does not specify the basis on which the EPA may make the
determination that the area cannot practicably attain by the applicable
attainment date. In the General Preamble, the EPA explained that the
agency could base this determination upon whatever factors are
pertinent and do so whether or not the state in question has submitted
a Moderate area attainment plan, and whether or not the state has made
the demonstration contemplated in section 189(a)(1)(B).\157\ The EPA
may make such a determination based on evaluation of the attainment
plan for the Moderate area in question or other facts known to the
agency. As discussed earlier in this preamble, the attainment plan that
a state would submit for a Moderate nonattainment area must include
either a demonstration that the area will attain the NAAQS by the
statutory Moderate area attainment date or a demonstration that
attaining by the statutory Moderate area attainment date is
impracticable. If the state makes and the EPA concurs with an
impracticability demonstration submitted as part of the attainment
plan, then the demonstration could serve as the basis for the EPA
initiating a notice-and-comment rulemaking to reclassify the area to
Serious. However, the CAA does not specify the basis for the EPA's
exercise of its discretionary authority and does not require the EPA to
make its determination based on a submission from the state. Indeed,
such a prerequisite would be illogical in the case of a state that
fails to make any attainment plan submission or fails to address the
issue of the need for reclassification in such submission.
---------------------------------------------------------------------------

    \157\ See the Federal Register published on April 16, 1994 (57
FR 13498, 13537 and 13538).
---------------------------------------------------------------------------

    Section 188(b)(1)(B) does establish mandatory timeframes by which
EPA must act if it intends to exercise its discretionary authority to
reclassify areas as appropriate following the Moderate area attainment
plan due date, stating that ``the Administrator shall reclassify
appropriate areas within 18 months after the required date for the
state's submission of a SIP for the Moderate Area.'' In the case of
areas designated nonattainment for the 2012 PM2.5 NAAQS in
the first round of designations, states will be required by statute to
submit a Moderate area attainment plan within 18 months of the date of
designation (April 2015), or no later than October 2016. Pursuant to
section 188(b)(1)(B), the EPA would then have until April 2018 (18
months following the Moderate area attainment plan submission deadline)
to use its discretionary authority to reclassify any area that the EPA
determines at that time cannot practicably attain by the Moderate area
attainment date of December 2021.
    As noted above, the EPA believes that while a Moderate area
impracticability demonstration as contemplated in section 189(a)(1)(B)
is desirable in order to help the agency make a determination that the
area cannot practicably attain by its attainment date, such a
demonstration is not necessary to trigger action by the EPA to
reclassify a Moderate area to Serious. The statute does not prohibit
the EPA from using the weight of available evidence, including
information available in the public record of a state, to make such a
determination, even in the absence of a complete attainment plan
submission. Thus, the EPA expressed in the General Preamble that:

. . . under the plain meaning of the terms of section 188(b)(1) EPA
has general discretion to reclassify at any time before the
applicable attainment date any area EPA determines cannot
practically attain the standards by such date. Accordingly, CAA
section 188(b)(1) is a general expression of delegated rulemaking
authority. In addition, subparagraphs (A) and (B) of CAA section
188(b)(1) mandate that the EPA reclassify at specified timeframes
any areas it determines appropriate for reclassification at those
dates. These subparagraphs do not restrict the general authority but
simply specify that, at a minimum, it must be exercised at certain
times.\158\
---------------------------------------------------------------------------

    \158\ Ibid. at 13537.

The EPA continues to consider this the correct interpretation of the
statutory requirements concerning its authority to reclassify a
Moderate nonattainment area to Serious at any time prior to the area's
Moderate area attainment date, if the agency determines that the area
cannot practicably attain the relevant PM2.5 NAAQS by that
date.
    The EPA emphasizes that states with an area designated as
nonattainment for the PM2.5 NAAQS are required to meet all
Moderate area attainment plan requirements, even after the EPA
reclassifies the area to Serious. Section 189(b)(1) states clearly that
``in addition to'' the Moderate area attainment plan requirements,
states with areas reclassified to Serious must also meet Serious area
attainment plan requirements, i.e., the reclassification does not
eliminate the statutory obligation to meet Moderate area

attainment plan requirements.\159\ Thus, the EPA believes that
reclassifying Moderate areas to Serious at any time under its
discretionary authority does not reward areas who delay development and
implementation of control measures by excusing states from meeting
substantive Moderate area attainment plan requirements or by extending
the applicable attainment date. The EPA articulated this position in
the General Preamble, explaining that this interpretation:
---------------------------------------------------------------------------

    \159\ See, Vigil v. Leavitt, 366 F.3d 1025, amended at 381 F.3d
826 (9th Cir. 2004).

. . . creates an incentive for the timely submittal and effective
implementation of moderate area SIP requirements and facilitates the
PM10 attainment objective. For example, if an area that
fails to submit a timely moderate area SIP is reclassified, this does
not obviate the requirement that the area submit and implement RACM
consistent with the moderate area schedule. Accordingly, the area could
be subject to sanctions for its delay in submitting the RACM SIP
requirement . . . Further, reclassification before the applicable
attainment date will ensure that additional control measures (i.e., in
addition to RACM, serious areas must implement best available control
measures (BACM)), are implemented sooner and will expedite the
application of more stringent new source review requirements to the
area . . . Similarly, where an area submits a timely moderate area SIP,
EPA may not discover that the area cannot practicably attain until
sometime after it begins implementing its moderate area control
measures. The EPA then may want to reclassify the area in order to
facilitate the development and implementation of BACM.\160\
---------------------------------------------------------------------------

    \160\ 57 FR 13498 (April 16, 1992), at page 13537.

    The EPA considers this the correct interpretation of the statutory
requirements and proposes to apply this longstanding interpretation of
section 188(b)(1) to nonattainment areas for the PM2.5
NAAQS.

B. Mandatory Duty

    In addition to the EPA's discretionary authority to reclassify a
Moderate area to Serious under certain circumstances, the CAA also
directs the EPA to do so under other circumstances. The alternative
circumstances under which the EPA will reclassify an area from Moderate
to Serious are if that area fails to attain the relevant NAAQS by the
applicable Moderate area attainment date, including any extension of
that date under section 188(d) for which the area qualifies. Under such
circumstances, the EPA has a mandatory duty to identify any area that
fails to attain the PM2.5 NAAQS by the applicable Moderate
area attainment date. Reclassification under such circumstances would
happen by operation of law when the EPA determines that the area failed
to attain the NAAQS by the applicable attainment date, in accordance
with section 188(b)(2)(A). Section 188(b)(2) requires that ``within six
months following the applicable attainment date for a PM10
nonattainment area, the Administrator shall determine whether the area
attained the standard by that date'' and publish its determination in
the Federal Register. The EPA proposes that the date of
reclassification for an area reclassified under the EPA's mandatory
duty to reclassify an area would be the effective date of the Federal
Register document announcing that the area had not attained the
relevant PM2.5 NAAQS and is therefore reclassified by
operation of law. Thus, for example in the case of the 2012
PM2.5 NAAQS, assuming a Moderate PM2.5
nonattainment area fails to attain the standard by its approved
attainment date of December 31, 2021, the EPA would be required to
publish in the Federal Register no later than June 30, 2022 its
determination that the area failed to attain the NAAQS and is therefore
reclassified as Serious by operation of law. The date of
reclassification for the area would be the effective date of the
Federal Register document, or sometime after June 30, 2022. To meet the
requirements of section 189(b)(2), the Serious area attainment plan for
the area would be due within 18 months thereafter, or no later than
December 2023.
    An alternative approach for setting the date of reclassification
for an area reclassified to Serious under the EPA's mandatory authority
could be to make it the same date as the missed attainment date for the
area. Applying this approach in the example above would yield an
earlier date of reclassification of December 31, 2021, and an earlier
Serious area attainment plan due date of June 30, 2023.
    Although section 188(b)(2) does not explicitly address this issue,
the EPA believes that its proposed approach is a reasonable
interpretation of statutory ambiguity in section 188(b)(2) and
preferable over the alternative approach for two reasons. First, the
statute at section 189(b)(2) gives a state 18 months from the date of
reclassification of an area to submit for the EPA's approval an
attainment demonstration with air quality modeling and provisions to
assure timely implementation of BACM and BACT on sources in the
nonattainment area. The EPA believes that it is reasonable for a state
with a Serious PM2.5 nonattainment area to have 18 months
plus the additional time needed by the EPA to issue a Federal Register
document announcing the area's failure to attain by the applicable
Moderate area attainment date and subsequent reclassification (up to 6
additional months) to ensure that the state has time to develop and
submit a thorough, complete and accurate Serious area attainment plan
that will provide for timely attainment of the NAAQS. Second, the
statutory attainment date for a Serious area reclassified under any
circumstances is as expeditious as practicable but no later than the
end of the tenth year following designation of the area, and is thus
independent of the date of reclassification of the area. Allowing a
state some additional amount of time beyond 18 months from the missed
attainment date to develop and submit a complete Serious area
attainment plan, including adopting BACM and BACT, will not change the
statutory obligation on the state for the area to attain the relevant
NAAQS by the applicable attainment date. On the contrary, the EPA
believes that the extra time may in fact help the area timely attain
the relevant NAAQS by allowing the state to develop a more effective
attainment plan for the area.
    The EPA seeks comment on its proposed approach of basing the date
of reclassification for an area reclassified under the agency's
mandatory duty in section 188(b)(2) on the effective date for the
Federal Register document in which the EPA announces that the area
failed to attain the PM2.5 NAAQS by the applicable Moderate
area attainment date and is reclassified by operation of law. The EPA
intends to make determinations of whether or not an area attained the
relevant NAAQS pursuant to section 188(b)(2) via notice-and-comment
rulemaking.

VI. What are the EPA's proposed requirements for Serious area
attainment plans?

    Sections 189(b) and (c) of the CAA include the following
requirements for Serious area attainment plan submissions: (i) An
attainment demonstration (section 189(b)(1)(A)); (ii) provisions for
the implementation of best available control measures (BACM) no later
than 4 years after reclassification of the area to Serious (section
189(b)(1)(B)); (iii) quantitative milestones that will be used to
evaluate compliance with the requirement to

demonstrate RFP (section 189(c)); and, (iv) regulation of
PM2.5 precursors (in general to meet attainment and control
strategy requirements and as specifically required for major stationary
sources by section 189(e)). Other subpart 1 requirements for attainment
plans not otherwise superseded under subpart 4 also apply to Serious
areas for the PM2.5 NAAQS, including: (i) A description of
the expected annual incremental reductions in emissions that will
demonstrate RFP (section 172(c)(2)); (ii) emissions inventories
(section 172(c)(3)); (iii) other control measures (besides BACM and
BACT) needed for attainment (section 172(c)(6)); and, (iv) contingency
measures (section 172(c)(9)).
    Additionally, section 189(b)(1) requires that ``in addition'' to
the attainment plan requirements specific to Serious areas, states must
also meet all Moderate area attainment plan requirements. The EPA
interprets the statutory language of section 189(b)(1) to require
states with areas that are reclassified to Serious to meet Moderate
area attainment plan requirements, including any areas that the EPA
reclassifies through rulemaking under its discretionary authority, even
if that occurs before the area has met all of its Moderate area
attainment plan requirements.\161\
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    \161\ See Vigil v. Leavitt, 366 F.3d 1025, amended at 381 F.3d
826 (9th Cir. 2004).
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    The remainder of this section presents the EPA's proposed
regulatory approaches to implement the requirements for attainment plan
submissions for Serious areas.

A. Plan Due Dates

    The timing of Serious area attainment plan elements is dictated by
two provisions of the CAA: Section 189(b)(2) for certain subpart 4
elements and section 172(b) for subpart 1 elements not superseded by
subpart 4 requirements. Section 189(b)(2) addresses the due dates for
Serious area attainment demonstrations due under section 189(b)(1)(A)
and provisions for BACM and BACT implementation under section
189(b)(1)(B). Specifically, section 189(b)(2) stipulates two
alternative schedules for states to submit Serious area attainment
demonstrations, depending upon the statutory authority invoked by the
EPA to reclassify the area from Moderate to Serious. For an area
reclassified to Serious by operation of law under section 188(b)(2)
upon a determination by the EPA that the area failed to attain the
relevant NAAQS by the applicable Moderate area attainment date, a state
must submit a new attainment demonstration for the area no later than
18 months after reclassification. For an area reclassified to Serious
pursuant to the agency's discretionary authority provided under section
188(b)(1), a state must submit a new attainment demonstration no later
than 4 years after reclassification of the area.\162\ For all Serious
nonattainment areas, section 189(b)(2) requires a state to submit
within 18 months of an area's reclassification ``provisions to assure
that the best available control measures [BACM] for the control of
PM10 shall be implemented no later than 4 years after the
date the area is classified (or reclassified) as a Serious Area.''
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    \162\ Section V of this preamble provides a more detailed
discussion of the process for reclassifying areas with severe
nonattainment problems to Serious.
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    In contrast, section 172(b) provides the EPA discretion to set a
due date for subpart 1 attainment plan elements that is no later than 3
years after designation of the area. In the Addendum, the EPA
interpreted the date of reclassification of an area to Serious to be
analogous to the date of designation of the area to nonattainment
generally.\163\ If the EPA selects the proposed option, discussed later
in this section, to adopt this convention, the subpart 1 attainment
plan elements of provisions to demonstrate RFP, emissions inventories,
additional control measures beyond BACM and BACT needed for expeditious
attainment of the PM2.5 NAAQS, and contingency measures
could in theory be due as late as 3 years after reclassification of an
area to Serious. For the reasons discussed below, the EPA believes that
it is necessary to harmonize the submission dates of the various
elements of a Serious are attainment plan for the PM2.5
NAAQS to provide for more effective evaluation of such attainment plan
submissions by states, the EPA and members of the general public.
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    \163\ Addendum to the General Preamble, 59 FR 41998 (August 16,
1994), at page 42015.
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    As with Moderate area attainment plans consisting of both subpart 1
and 4 elements, the EPA presumes that simultaneous development and
submission of most, if not all, of the Serious area attainment plan
elements will be most effective, both for the state in developing the
plan and for the EPA in reviewing the state's submission, given the
interplay between all plan elements in the formation of a successful
control strategy for the area. Just as importantly, a complete
attainment plan submission facilitates the general public's review of
the entire control strategy adopted by the state. Therefore where there
is ambiguity in the statutory provisions, the EPA is proposing one or
more approaches to schedule submission of the various elements of
Serious area attainment plans in a way that will facilitate better
development and evaluation of such attainment plan submissions. The
EPA's proposed options for due dates for specific elements of a Serious
area attainment plan are described below.
1. Area Reclassified to Serious After Failing To Attain the
PM2.5 NAAQS
    If the EPA reclassifies a Moderate area to Serious because of a
failure to attain the relevant NAAQS by the applicable attainment date,
section 189(b)(2) requires that the state must submit both the
attainment demonstration for the area and provisions to ensure timely
BACM and BACT implementation to the EPA within 18 months after
reclassification. Because an up-to-date base year emissions inventory,
required under section 172(c)(3), will serve as the foundation of a
state's BACM and BACT determination, and additional control measures
(beyond BACM and BACT) that are necessary for expeditious attainment of
the PM2.5 NAAQS as required under section 172(c)(6) will
need to be identified in order to complete the control strategy for the
area, the EPA proposes that both the base year inventory and additional
control measures (beyond BACM and BACT) needed for expeditious
attainment must also be submitted within 18 months after
reclassification of the area to Serious by operation of law.
    The EPA also proposes and seeks comment on two possible due dates
for the remaining Serious area attainment plan elements for areas that
failed to attain the NAAQS by the applicable Moderate area attainment
date. Those plan elements are provisions for RFP, quantitative
milestones and contingency measures. The first proposed due date for
these remaining Serious area attainment plan elements would be no later
than 18 months after reclassification of the area, consistent with the
due date for the plan elements already described above. As noted above,
the EPA maintains that requiring states to submit all elements of an
attainment plan by the same date is reasonable because it allows for a
complete review of the state submission by the EPA, regulated entities,
and the general public, and it also may prove most efficient for
states. See proposed 40 CFR 51.1003(b)(2)(ii).
    The alternate proposed due date for the remaining elements would be
3 years following reclassification to

Serious, which would be consistent with guidance the EPA provided in
the Addendum specific to the due date for contingency measures for
Serious areas.\164\ This guidance references the EPA's discretion under
section 172(b) to establish due dates up to 3 years after designation
for attainment plan elements required under section 172(c), which also
include RFP provisions. Subpart 4 meanwhile requires quantitative
milestones to demonstrate RFP but does not specify a due date for
submitting such milestones as part of the attainment plan for the area
(as separate and distinct from the clear statutory requirements related
to demonstrating compliance with those milestones established in the
attainment plan). When taken together, the EPA believes that these
statutory provisions may be read to permit a state to submit these
three elements of the plan as late as 3 years after reclassification of
the area. While the EPA does not believe that such a reading is as
logical as the agency's first proposed approach, the EPA seeks comment
on this alternative proposed approach to setting due dates for a state
to submit an RFP plan, quantitative milestones and contingency measures
for a Serious area reclassified under the EPA's mandatory authority.
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    \164\ Ibid. at 42015.
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2. Area Reclassified to Serious Due to an Inability To Practicably
Attain the NAAQS by the Statutory Moderate Area Attainment Date
    If the EPA determines that a Moderate area cannot practicably
attain the relevant NAAQS by the applicable attainment date and
reclassifies the area to Serious pursuant to its discretionary
authority under section 188(b)(1), section 189(b)(2) requires the state
to submit provisions to ensure timely implementation of BACM and BACT
to the EPA within 18 months after reclassification. As stated earlier,
because an up-to-date emissions inventory serves as the foundation for
a state's BACM and BACT determination and pursuant to the authority
granted to the EPA under section 172(b), the EPA proposes that the
state must meet the emissions inventory requirement under section
172(c)(3) also within 18 months after reclassification of the area by
submission of an up-to-date emissions inventory.
    With respect to the attainment demonstration requirement for
Serious areas reclassified pursuant to section 188(b)(1), section
189(b)(2) allows the state up to 4 years after reclassification to
submit a new attainment demonstration for an area reclassified to
Serious because it cannot practicably attain the PM2.5 NAAQS
by the applicable Moderate area attainment date. This due date could
generally be appropriate, notwithstanding the related issues discussed
in the following paragraphs, if the EPA finalizes an approach for
determining the overall control strategy for the area in which BACM and
BACT are identified independent of the attainment demonstration for the
area (see proposed Option 1 for BACM and BACT determinations described
in Section VI.D of this preamble).
    However, the EPA is also proposing an alternative approach for
determining the control strategy for a Serious area, under which BACM
and BACT and additional feasible measures would be identified in
conjunction with the attainment demonstration for the area (see
proposed Option 2 for BACM and BACT determinations described in Section
VI.D of this preamble). Under such an approach, the EPA proposes that
the due date for the Serious area attainment demonstration would be no
later than 18 months after reclassification if the EPA finalizes its
proposed Option 2 for determining BACM and BACT for the area, as the
attainment demonstration would be necessary in order for the EPA and
the public to determine whether the control strategy identified for the
area is adequate, and the statute requires that a state submit its BACM
provisions within 18 months after reclassification of an area.
    With respect to other elements of a Serious area attainment plan,
under the EPA's prior interpretation as described in the Addendum, the
EPA had suggested that states could submit contingency measures no
later than 3 years after reclassification of an area to Serious because
of the language of section 172(b).\165\ The EPA believes it may be
appropriate to extend a similar approach to establishing due dates for
some other attainment plan elements required under subpart 1.
Therefore, the EPA proposes to provide a state with the maximum time
permitted under section 172(b)--3 years from the date of
reclassification of the area--to submit the following plan elements:
Provisions to demonstrate RFP, other control measures (beyond BACM and
BACT) needed to bring the area into expeditious attainment, and
contingency measures. The EPA proposes that quantitative milestones,
required under subpart 4 but linked to RFP which is required under
subpart 1, would also be included with the plan elements due 3 years
following reclassification.
---------------------------------------------------------------------------

    \165\ Ibid. at 42015.
---------------------------------------------------------------------------

    The EPA believes that this proposed due date for certain attainment
plan elements required under subparts 1 and 4 would be most appropriate
if finalized in conjunction with proposed Option 2 for BACM and BACT,
which would require the state to submit the attainment demonstration
for the area within 18 months after reclassification of the area to
Serious. However, in the event the EPA finalizes proposed Option 1 for
determining BACM and BACT for a Serious nonattainment area independent
of the attainment demonstration for the area, the attainment
demonstration for the area would be due no later than 4 years after the
date of reclassification of the area to Serious. Given the integral
role that the attainment demonstration plays in helping to identify
additional feasible measures (beyond BACM and BACT) that an area may
need to attain the relevant standard expeditiously (and which are
required under section 172(c)(6)), to calculate emissions reductions
needed on an annual basis to demonstrate RFP, and to calculate the
emissions reductions that contingency measures need to achieve and
identify what controls could constitute such measures, the EPA is
proposing and seeking comment on an alternative submittal deadline for
provisions for RFP and quantitative milestones, additional control
measures needed for expeditious attainment, and contingency measures
that would align their due date with the statutory Serious area
attainment demonstration due date, no later than 4 years from the date
of reclassification. See proposed 40 CFR 51.1003(b)(2)(i). The EPA
believes that coordinating submission of attainment plan elements so
that they may be developed and reviewed together can prove most
efficient for the submitting state, the EPA, and the general public,
and therefore this proposed alternative is the agency's preferred
approach. However, the EPA seeks comment on all of its proposed due
date options for the various elements of a Serious area attainment
plan.

B. Emissions Inventory Requirements

1. What emissions inventory requirements apply to Serious area
attainment plans?
    As with PM2.5 nonattainment areas classified as
Moderate, Congress did not create a specific emissions inventory
requirement in subpart 4 that would supersede the emissions inventory
requirement under subpart 1 for Serious areas. Thus, the statutory
emissions

inventory requirements that apply for Serious area attainment plans
continue to be those of section 172(c)(3), which explicitly requires
``a comprehensive, accurate, and current inventory of actual emissions
of the relevant pollutants'' in the nonattainment area. In addition,
the specific attainment plan requirements for the PM2.5
NAAQS set forth in section 189(a) and associated modeling requirements
make an accurate and up-to-date emissions inventory a critical element
of any viable attainment plan. Finally, the additional attainment plan
requirements for the PM2.5 NAAQS for Serious areas contained
in subpart 4 at section 189(b) have additional requirements that affect
the emissions inventory requirements for Serious areas.\166\
---------------------------------------------------------------------------

    \166\ All definitions described in Section IV.B of this preamble
for areas classified as Moderate apply in this section.
---------------------------------------------------------------------------

    As noted earlier in this preamble, states must use the best
available, current emissions inventory information for attainment plan
development, because complete, high quality emissions inventory data
are essential for the development of an effective control strategy. To
assist states in preparing complete, high quality inventories, the EPA
provides guidance for developing emissions inventories in its SIP
Emissions Inventory Guidance, available at http://www.epa.gov/ttn/chief/eidocs/eiguid/index.html. The EPA recommends that states consult
this guidance while developing emissions inventories to meet
requirements for Serious area attainment plans.
2. How do states meet the inventory requirements for the
PM2.5 NAAQS for areas classified as Serious?
    As with Moderate PM2.5 nonattainment areas, neither
section 172(c)(3) nor the provisions specifically applicable to
attainment plans for the PM2.5 NAAQS in subpart 4 specify
how states should meet statutory emissions inventory requirements for
Serious PM2.5 nonattainment areas. Section 172(c)(3)
requires that states submit ``a comprehensive, accurate, current
inventory of actual emissions from all sources of the relevant
pollutant or pollutants in such area, including such periodic revisions
as the Administrator may determine necessary to assure that the
requirements of this part are met'' (emphasis added). The EPA
interprets this provision to authorize the agency to require states to
revise their base year emissions inventories whenever the state is
required to submit a new attainment plan because of a change in the
nonattainment area's status (e.g. failure to attain by the applicable
attainment date resulting in reclassification). In addition, pursuant
to CAA section 301, the EPA has additional authority to promulgate
regulations as necessary for the implementation of the PM2.5
NAAQS, including requirements pertaining to emissions inventories.
Accordingly, the EPA is proposing specific emissions inventory
requirements it considers necessary to effectuate the attainment plan
requirements of the CAA for the PM2.5 NAAQS.
    Like Moderate areas, there are three key facets of the EPA's
proposed emissions inventory requirements, as laid out below: (i) The
types of inventories required; (ii) the content of these inventories;
and, (iii) the timing of submittal of these inventories. The three
facets are addressed in the following paragraphs.
    First, the EPA proposes that the same two types of inventories
required for Moderate areas are also required for Serious areas. While
these inventories are the same types and names of inventories as for
Moderate areas, they must be created specifically for Serious area
attainment plans in accordance with the applicable Serious area
requirements. The first type of inventory, the ``base year inventory
for the nonattainment area,'' is expressly required by section
172(c)(3). The second type of inventory the EPA is proposing to require
under section 301(a)(1) is necessary to implement the attainment
demonstration requirement of section 189(a)(1)(B). This second
inventory is called the ``attainment projected inventory for the
nonattainment area.'' See proposed 40 CFR 51.1008(b)(1) and (2).
    Second, the EPA proposes that the content of the inventories will
follow the content requirements for Moderate area inventories, with one
exception needed to meet the requirements of section 189(b)(3). For
Serious areas, section 189(b)(3) defines a separate emissions threshold
for major sources in Serious nonattainment areas (70 tpy potential to
emit of PM10), and this major source threshold is used in 40
CFR part 51, subpart A (the AERR) to define which sources must be
reported as point sources for PM10. This threshold is lower
than the 100 tpy potential to emit general requirement for major
sources of PM10, PM2.5 or one of its precursors
that is used for Moderate area emissions inventories. Inventories for
Serious area attainment plans must include these smaller sources as
point sources (rather than the nonpoint source category that would
apply for these in Moderate area plans) using the lower threshold
specified in the CAA and codified in 40 CFR part 51, subpart A. Also as
described above and in 40 CFR part 51, subpart A, this means that all
other smaller stationary sources must be included in the inventory as
nonpoint sources.
    Third, Section VI.A of this preamble describes the EPA's proposal
to require that a state submit the base year inventory for a Serious
nonattainment area at the same time that it submits provisions to
implement BACM and BACT on sources in the area (due no later than 18
months from reclassification of the area pursuant to section 189(b)(2))
as the base year inventory serves as the starting point for conducting
a BACM and BACT determination. On the other hand, because the
attainment projected inventory is more closely related to the Serious
area attainment demonstration, the EPA believes that a state should be
required to submit its attainment projected inventory with the
attainment demonstration for a given Serious area in order to allow
effective evaluation of the attainment plan as a whole. Consequently,
the EPA is proposing to establish the regulatory requirement that
attainment projected emissions inventories be submitted at the same
time as the Serious area attainment demonstration, which would mean no
later than 18 months after reclassification for areas reclassified
after failing to attain the NAAQS by the applicable Moderate area
attainment date, or no later than 4 years after reclassification for
areas reclassified by the EPA because the area cannot practicably
attain the NAAQS by the statutory attainment date if the EPA finalizes
proposed Option 1 for determining BACM and BACT for area. See proposed
40 CFR 51.1008(b)(3) and (4). If the EPA finalizes an approach for
determining BACM and BACT that links the control strategy analysis to
the attainment demonstration, then the attainment demonstration
including the attainment projected emissions inventory would be due no
later than 18 months after reclassification (i.e., at the same time
BACM provisions are due under the statute).
    The EPA seeks comment on these proposed requirements and due dates
for emissions inventories for Serious area attainment plans.

C. Pollutants To Be Addressed in the Plan

    Section III of this preamble includes a detailed discussion about
how states should address PM2.5 precursors in attainment
plans and in the NNSR

program for purposes of implementing current and future
PM2.5 NAAQS. While evaluating sources of direct
PM2.5 for BACM and BACT is an implicit requirement in the
context of implementing the PM2.5 NAAQS under any scenario,
the EPA is proposing and seeking comment on several options for
addressing PM2.5 precursors under the PM2.5 NAAQS
implementation program. The EPA interprets the requirements of the CAA
to allow an air agency to provide a ``precursor demonstration'' that
can seek to make a technical case to the EPA that one or more
PM2.5 precursors need not be subject to control requirements
in a given nonattainment area, whether from sources in general or from
major stationary sources. Section III presented three options
describing different proposed approaches to such precursor
demonstrations, and requested comment on each. The discussion for each
option described how precursors would be addressed for Moderate areas
and for Serious areas.
    In general terms, the three options can be summarized as follows:
     Option 1: Two independent analyses: (a) An attainment
planning analysis demonstrating that control measures for a particular
precursor are not needed for expeditious attainment, meaning that the
precursor can be excluded from measures needed to attain as
expeditiously as practicable for all types of sources; and, (b) a
section 189(e) technical demonstration showing that major stationary
sources of a particular precursor do not contribute significantly to
levels that exceed the PM2.5 standard, meaning that the
precursor can be excluded from control requirements for major sources
and from NNSR permitting. For an area reclassified to Serious, the