Blumenfeld, Regional Administrator, EPA Region 9 (transmitting air
district regulations to EPA as California SIP revisions).
    \340\ CARB Staff Report, Table 8, p. 20; see also http://www.arb.ca.gov/regact/2015/simw2015/simw2015.htm.
---------------------------------------------------------------------------

    With respect to the outstanding emission reduction commitments
(also called ``aggregate commitments''), Tables 9 and 10 of the CARB
Staff Report, as amended by CARB's Technical Clarifications, identify
nine specific State and District control measures that, according to
CARB, achieved emission reductions beyond those already credited toward
the 2008 PM2.5 Plan and that satisfy the State's remaining
2014 emission reduction obligations. These measures are identified in
Table 6.

   Table 6--2008 PM2.5 Plan Aggregate Commitment--State and District-
                           Identified Measures
------------------------------------------------------------------------
                                             2014 Emission reductions
                                               (annual average tpd)
                 Measure                 -------------------------------
                                                NOX        Direct PM2.5
------------------------------------------------------------------------
Rule 4320 (Advanced Emission Reduction               1.8             0.0
 Options for Boilers, Steam Generators,
 and Process Heaters Greater than 5.0
 MMBtu/hr)..............................
Rule 9510 (Indirect Source Review)......             1.0             0.1
Woodstove Replacements..................             0.0             0.1
District Funded Incentive-Based Emission             1.5             0.1
 Reduction Measures.....................
Rule 9410 (Employer Based Trip                       0.3             0.0
 Reduction).............................
Rule 4901 (Wood Burning Fireplaces and               0.0             1.3
 Wood Burning Heaters)..................
State Funded Incentive-Based Emission                7.8             0.2
 Reduction Measures.....................
CARB Cleaner In-Use Heavy Duty Trucks               11.5             0.1
 Measure................................
CARB Portable Equipment Registration                 2.5             0.2
 Program (PERP) and Portable Engine ATCM
                                         -------------------------------
    Total Emission Reductions...........            26.4             2.1
------------------------------------------------------------------------
Source: CARB Staff Report, pp. 21, 22 and Technical Clarifications, pp.
  2 to 4.

    We have reviewed the State's demonstration with respect to each of
these nine measures and, for the reasons provided below, we propose to
find that all but one may be credited toward the State's outstanding
2014 emission reduction obligations.
    First, with respect to SJVUAPCD's Rule 4320 (``Advanced Emission
Reduction Options for Boilers, Steam Generators, and Process Heaters
Greater than 5.0 MMBtu/hr''), also called the ``AERO Rule,'' the EPA
approved this rule as adopted October 2008 into the

California SIP on March 25, 2011 \341\ but did not credit the rule with
any emission reductions as part of the attainment demonstration in the
2008 PM2.5 Plan.\342\ In the proposal to approve this rule
into the SIP, the EPA stated that because this rule allows regulated
entities to pay a fee in lieu of meeting NOX emission
limits, the State would need to demonstrate that the fee provisions
achieve emission reductions that are quantifiable, surplus,
enforceable, and permanent consistent with EPA guidance before relying
on this rule for credit in an attainment plan.\343\
---------------------------------------------------------------------------

    \341\ 76 FR 16696 (March 25, 2011).
    \342\ 2008 PM2.5 Plan TSD at pp. 93-94, Table F-4
(September 30, 2011); see also CARB Staff Report, Appendix B at p.
B-7 and Table B-8.
    \343\ 75 FR 68294 at 68295 (November 5, 2010).
---------------------------------------------------------------------------

    In the CARB Staff Report, the State explained that it now has
documentation showing that operators of 472 of the units subject to
Rule 4320 chose to pay fees and that operators of the remaining 692
units subject to the rule chose to retrofit their equipment to comply
with the NOX emission limits in the rule.\344\ CARB also
explained that, based on these enforceable emission limits, the
District estimated that the operators of the 692 units that did not pay
fees had achieved 1.8 tpd of actual NOX emission reductions
by the beginning of 2014, based on an operating capacity of 50% or
75%.\345\ We find this documentation adequate to credit Rule 4320 with
1.8 tpd of NOX emission reductions toward the State's
outstanding 2014 emission reduction obligation.
---------------------------------------------------------------------------

    \344\ CARB Staff Report, Appendix B at p. B-7.
    \345\ Id. at p. B-8, Table B-8.
---------------------------------------------------------------------------

    Second, with respect to SJVUAPCD's Rule 9510 (``Indirect Source
Review''), the EPA approved this rule as adopted December 2005 into the
California SIP on May 9, 2011 \346\ but did not credit the rule with
any emission reductions as part of the attainment demonstration in the
2008 PM2.5 Plan.\347\ In the final rule to approve Rule 9510
into the SIP, the EPA identified a number of concerns about the
enforceability of the rule's provisions, e.g., provisions that allow
project developers to pay a fee instead of implementing on-site
pollution mitigation plans, and noted that the State would need to
resolve these enforceability issues before relying on this rule for
credit in an attainment plan.\348\
---------------------------------------------------------------------------

    \346\ 76 FR 26609 (May 9, 2011).
    \347\ 2008 PM2.5 Plan TSD at pp. 100-101; see also
CARB Staff Report, Appendix B at pp. B-6 and B-7.
    \348\ 76 FR 26609 at 26612-26613 (May 9, 2011).
---------------------------------------------------------------------------

    In the CARB Staff Report, the State explained that it now has
documentation of the number of projects that have complied with the
rule through on-site mitigation (instead of payment of a fee) and the
associated reductions in on-site emissions of NOX and
PM10.\349\ The project information provided in Appendix B-2
of the CARB Staff Report, however, is not adequate for the EPA to
determine what types of mitigation plans were implemented, to verify
that those plans were implemented as proposed, or to estimate the
associated emission reductions. Furthermore, it is unclear whether the
District or any other state or local agency is authorized to enforce
these mitigation plans. We find this documentation insufficient to
credit Rule 9510 with any emission reductions toward the State's
outstanding 2014 emission reduction obligation.
---------------------------------------------------------------------------

    \349\ CARB Staff Report at p. B-6, B-7 (referencing list of
projects in Appendix B-2).
---------------------------------------------------------------------------

    Third, with respect to wood stove replacements, the CARB Staff
Report explains that the District implements a voluntary wood stove
replacement program that provides funding for residents to replace less
efficient wood stoves with more efficient gas-burning devices.\350\
CARB also notes that the District has provided a list of wood stoves
replaced through this program as of December 31, 2013, together with
documentation of the calculation methodologies and related emission
factors that it used to calculate the direct PM2.5 emission
reductions achieved by these wood stove replacements.\351\ All wood
stoves are installed by a District contracted retailer, with pre- and
post-installation photographs provided to the District. Old wood or
pellet inserts/stoves are removed and surrendered to a licensed
recycling/dismantling facility within 60 days of installation.\352\ We
find this documentation adequate to credit the District's wood stove
replacement program with 0.1 tpd of direct PM2.5 emission
reductions toward the State's outstanding 2014 emission reduction
obligation.
---------------------------------------------------------------------------

    \350\ Id. at pp. B-5.
    \351\ Id. at pp. B-5, B-6 and Appendix B-1.
    \352\ See SJVAPCD Burn Cleaner Voucher Guidelines, dated
December 2014, available at: http://valleyair.org/grants/documents/burncleaner/2014/BC_Guidelines.pdf; and SJVAPCD Burn Cleaner Voucher
Application--Phase 1, dated December 2014, available at: http://valleyair.org/grants/documents/burncleaner/2014/BC_VoucherApp.pdf.
---------------------------------------------------------------------------

    Fourth, with respect to District-funded incentive programs, CARB
provided a list of stationary and portable agricultural engines and
off-road agricultural equipment that were repowered, retrofitted with
controls, or replaced with newer equipment through incentive funds
disbursed by the District pursuant to the Carl Moyer Memorial Air
Quality Standards Attainment Program (Carl Moyer Program).
Specifically, the CARB Staff Report documents the State's bases for
concluding that a total of 824 incentive projects implemented in the
SJV between January 2009 and December 2013 in accordance with specified
portions of the Carl Moyer Program Guidelines have achieved a total of
1.8 tons per day (tpd) of NOX emission reductions and 0.1
tpd of PM2.5 emission reductions in the SJV, which may be
credited toward the State's 2014 emission reduction commitment.\353\
The EPA previously reviewed the identified portions of the Carl Moyer
Program Guidelines and found that they adequately address the EPA's
recommended integrity elements for economic incentive programs.\354\ We
find this documentation sufficient to credit these District-funded
projects with 1.8 tpd of NOX emission reductions and 0.1 tpd
of direct PM2.5 emission reductions toward the State's
outstanding 2014 emission reduction obligation.
---------------------------------------------------------------------------

    \353\ CARB Staff Report, pp. B-9 to B-12; Technical
Clarifications at 2-4; and Revised Appendix B-3.
    \354\ The specified portions of the guidelines that apply to the
identified projects are contained in The Carl Moyer Program
Guidelines, Approved Revision 2005; The Carl Moyer Program
Guidelines, Approved Revision 2008; and The Carl Moyer Program
Guidelines, Approved Revision 2011. See CARB Staff Report at Table
B-10. EPA has reviewed these portions of the Carl Moyer Program
Guidelines and found that they adequately address EPA's recommended
integrity elements for economic incentive programs. 79 FR 29327 (May
22, 2014); see also 80 FR 51147 (August 24, 2015).
---------------------------------------------------------------------------

    Fifth, with respect to SJVUAPCD's Rule 9410 (``Employer Based Trip
Reduction''), CARB submitted this rule as adopted December 2009 to the
EPA as a revision to the California SIP on May 17, 2010, and on
December 11, 2015, the EPA fully approved the rule into the SIP.\355\
Accordingly, the emission reductions that the State and District have
attributed to this rule (0.3 tpd of NOX emission reductions)
are creditable toward the State's outstanding 2014 emission reduction
obligation. As part of the EPA's proposed action on Rule 9410, the EPA
evaluated the District's estimates of emission reductions achieved by
the rule and found the District's calculations to be technically sound
and

generally consistent with the planning assumptions in the 2008
PM2.5 Plan.\356\
---------------------------------------------------------------------------

    \355\ EPA, Final rule, ``Approval and Promulgation of
Implementation Plans; California; San Joaquin Valley Unified Air
Pollution Control District; Employer Based Trip Reduction
Programs,'' pre-publication notice signed December 11, 2015.
    \356\ 80 FR 51153 (August 24, 2015).
---------------------------------------------------------------------------

    Sixth, with respect to SJVUAPCD's Rule 4901 (``Wood Burning
Fireplaces and Wood Burning Heaters''), the EPA approved this rule as
adopted October 2008 into the California SIP on November 10, 2009 \357\
and credited the rule with 1.08 tpd of direct PM2.5 emission
reductions in 2014 as part of the attainment demonstration in the 2008
PM2.5 Plan.\358\ In the CARB Staff Report, the State
explained that it now has documentation of additional direct
PM2.5 emission reductions achieved by this rule based on an
updated methodology for calculating emission reductions from its
curtailment program. Specifically, the District reviewed ambient air
quality data for a more recent period (2009-2013) to determine the
number of ``No Burn'' days that would have been required under the
mandatory curtailment level (30 [micro]g/m\3\) in the October 2008
version of Rule 4901. This updated air quality data resulted in a
larger number of ``No Burn'' days compared to the District's prior
calculation, which was based on 2006 air quality data.\359\ We find
this documentation adequate to credit Rule 4901 with 1.3 tpd of direct
PM2.5 emission reductions toward the State's outstanding
2014 emission reduction obligation.
---------------------------------------------------------------------------

    \357\ 74 FR 57907 (November 10, 2009).
    \358\ 2008 PM2.5 Plan TSD at p. 93, Table F-4
(September 30, 2011); see also 76 FR 69896 at 69921, Table 1
(November 9, 2011).
    \359\ 2015 PM2.5 Plan, Technical Clarifications, p.
1; and CARB Staff Report, Appendix B, p. B-7.
---------------------------------------------------------------------------

    Seventh, with respect to State Funded Incentive-Based Emission
Reduction Measures, CARB submitted the ``Report on Reductions Achieved
from Incentive-based Emission Reduction Measures in the San Joaquin
Valley'' (Emission Reduction Report) to the EPA as a revision to the
California SIP on November 17, 2014,\360\ and on August 24, 2015, the
EPA proposed to fully approve this report into the SIP.\361\ As part of
this proposal, the EPA evaluated the State's demonstration that
specified portions of the Carl Moyer Program and Prop 1B Program
guidelines adequately address the EPA's recommended integrity elements
for economic incentive programs and that the identified projects funded
pursuant to these guidelines achieved 7.8 tpd of NOX
emission reductions and 0.2 tpd of direct PM2.5 emission
reductions by the beginning of 2014.\362\ Upon final approval of this
demonstration into the California SIP, these emission reductions would
be creditable toward the State's 2014 emission reduction obligation.
Thus, final action by the EPA to fully approve the Emission Reduction
Report before or concurrent with our final action on the 2015
PM2.5 Plan would suffice to credit these state-funded
projects with 7.8 tpd of NOX emission reductions and 0.2 tpd
of direct PM2.5 emission reductions toward the State's
outstanding 2014 emission reduction obligation.
---------------------------------------------------------------------------

    \360\ CARB Staff Report, Appendix B at p. B-2.
    \361\ 80 FR 51147 (August 24, 2015).
    \362\ Id.
---------------------------------------------------------------------------

    Eighth, with respect to CARB's Cleaner In-Use Heavy Duty Trucks
measure (also called the Truck and Bus Regulation and Drayage Truck
Regulation), the EPA approved these rules as adopted September 2011
into the California SIP on April 4, 2012 \363\ and credited the rules
with 1.1 tpd of NOX emission reductions and 1.7 tpd of
direct PM2.5 emission reductions in 2014 as part of the
attainment demonstration in the 2008 PM2.5 Plan.\364\ In the
CARB Staff Report, the State explained that it now has documentation of
additional NOX and direct PM2.5 emission
reductions achieved by these rules by the beginning of 2014, based on
current compliance reports indicating that diesel particulate filters
(DPFs) are more efficient than original estimates and that a larger
than expected number of truck and bus owners had purchased new vehicles
(which are cleaner than retrofits) rather than installing retrofit
DPFs.\365\ We find this documentation adequate to credit CARB's Cleaner
In-Use Heavy Duty Trucks measure with 11.5 tpd of NOX
emission reductions and 0.1 tpd of direct PM2.5 emission
reductions toward the State's outstanding 2014 emission reduction
obligation.
---------------------------------------------------------------------------

    \363\ 77 FR 20308 (April 4, 2012).
    \364\ 2008 PM2.5 Plan TSD, Table F-8, p. 99
(September 30, 2011).
    \365\ CARB Staff Report, Appendix B, pp. B-2 to B-4.
---------------------------------------------------------------------------

    Finally, with respect to CARB's Portable Equipment Registration
Program (PERP) and Portable Engine Airborne Toxic Control Measure
(Portable Engine ATCM), CARB adopted these programs in 1997 and 2004,
respectively, to reduce pollution by requiring the removal of
uncertified engines from the registered fleet of nonroad engines
operating in California.\366\ The EPA did not credit either of these
programs with emission reductions as part of the attainment
demonstration in the 2008 PM2.5 Plan.\367\ On December 6,
2012, the EPA granted California's request for authorization under CAA
section 209(e)(2) to implement both the PERP and the Portable Engine
ATCM.\368\ On August 14, 2015, CARB submitted these measures to the EPA
for SIP approval and on November 12, 2015, the EPA proposed to approve
both measures as revisions to the California SIP.\369\ Upon final
approval of these measures into the SIP, their requirements will be
federally enforceable and the associated emission reductions will be
creditable for attainment planning purposes in the SJV. Thus, final
action by the EPA to fully approve the PERP and the Portable Engine
ATCM before or concurrent with our final action on the 2015
PM2.5 Plan would suffice to credit these measures with 2.5
tpd of NOX emission reductions and 0.2 tpd of
PM2.5 reductions toward the State's outstanding 2014
emission reduction obligation.
---------------------------------------------------------------------------

    \366\ Id. at pp. B-4, B-5 and Technical Clarifications, p. 3.
    \367\ 2008 PM2.5 Plan TSD, Table F-8, p. 99
(September 30, 2011).
    \368\ 77 FR 72846 and 77 FR 72851 (December 6, 2012).
    \369\ Letter dated August 14, 2015, from Richard W. Corey,
Executive Officer, California Air Resources Board, to Jared
Blumenfeld, Regional Administrator, EPA Region 9, with attachments.
80 FR 69915 (November 12, 2015).
---------------------------------------------------------------------------

    According to the CARB Staff Report, implementation of these control
measures resulted in NOX emission reductions that exceeded
the State's outstanding NOX commitment by 13.9 tpd by the
beginning of 2014.\370\ Citing air quality modeling conducted as part
of the 2008 PM2.5 Plan, CARB stated that a reduction of 9
tpd of NOX emissions provides an air quality improvement
equivalent to a 1 tpd reduction in directly emitted PM2.5.
On this basis, CARB concluded that an 8.1 tpd portion of the 13.9 tpd
of surplus NOX reductions achieved through implementation of
the identified State and District measures adequately covered the small
shortfall (0.9 tpd) in required reductions of direct
PM2.5.\371\
---------------------------------------------------------------------------

    \370\ CARB Staff Report at pp. 21, 22.
    \371\ Id.
---------------------------------------------------------------------------

    Table 7 identifies the State and District measures that the EPA is
proposing to credit toward the State's outstanding 2014 emission
reduction obligations, the amount of SIP-creditable emission reductions
for each measure, and the 9:1 NOX for PM2.5
trading ratio \372\ calculation that the EPA is proposing to accept for
this purpose. The total amount of SIP-creditable NOX
emission reductions associated with the identified control measures
(25.4 tpd) exceeds the State's outstanding NOX emission
reduction commitment (12.9

tpd) by 12.5 tpd.\373\ We believe the technical bases for a 9:1
NOX for PM2.5 trading ratio are generally sound
and have therefore used this trading ratio to credit the State with 1
additional tpd of PM2.5 emission reduction (based on 9 tpd
of ``excess'' NOX emission reductions) toward its
outstanding 2014 commitment. In evaluating the interpollutant trading
used for the aggregate commitments (as well as for Reasonable Further
Progress and for Motor Vehicle Emissions Budgets for conformity), the
EPA considered the regulatory basis for allowing interpollutant
trading, 24-hour and annual averaging times, the pollutant trading
direction, the geographical extent of emissions, the conservativeness
and the numerical stability of the ratio, and the geographical
variation of the trading ratio. For further discussion of our
evaluation of the 9:1 NOX to PM2.5 trading ratio
for purposes of the aggregate commitment, please see section IV.C of
the EPA's ``Technical Support Document for EPA's Evaluation of
Interpollutant Trading Ratios For Fine Particulate Matter Emissions in
the San Joaquin Valley Air Pollution Control District,'' January 2016
(``Interpollutant Trading Ratios TSD'').
---------------------------------------------------------------------------

    \372\ We use ``trading ratio'' in this action to refer to the
extent to which reductions of one pollutant are substituted for
necessary reductions of another pollutant.
    \373\ As explained in this section, we find CARB's documentation
insufficient to credit Rule 9510 with any emission reductions toward
the State's outstanding 2014 emission reduction obligation and,
therefore, do not entirely agree with CARB's conclusion that it
achieved 13.9 tpd of NOX emission reductions in excess of
its outstanding commitments. The difference between the 25.4 tpd of
NOX emission reductions achieved by the control measures
identified in Table 7 and the State's outstanding 12.9 tpd
NOX emission reduction commitment is 12.5 tpd of
``excess'' NOX emission reductions.

  Table 7--2008 PM2.5 Plan Aggregate Commitment--EPA Proposed Emission
     Reduction Credits for Measures in CARB Compliance Demonstration
------------------------------------------------------------------------
                                             2014 emission reductions
                                               (annual average tpd)
                 Measure                 -------------------------------
                                                NOX        Direct PM2.5
------------------------------------------------------------------------
Rule 4320 (Advanced Emission Reduction               1.8             0.0
 Options for Boilers, Steam Generators,
 and Process Heaters Greater than 5.0
 MMBtu/hr)..............................
Rule 9510 (Indirect Source Review)......             0.0             0.0
Woodstove Replacements..................             0.0             0.1
District Funded Incentive-Based Emission             1.5             0.1
 Reduction Measures.....................
Rule 9410 (Employer Based Trip                       0.3             0.0
 Reduction).............................
Rule 4901 (Wood Burning Fireplaces and               0.0             1.3
 Wood Burning Heaters)..................
State Funded Incentive-Based Emission                7.8             0.2
 Reduction Measures.....................
CARB Cleaner In-Use Heavy Duty Trucks               11.5             0.1
 Measure................................
CARB Portable Equipment Registration                 2.5             0.2
 Program (PERP) and Portable Engine ATCM
                                         -------------------------------
    Total SIP-Creditable Emission                   25.4             2.0
     Reductions from State and District
     Measures...........................
NOX to PM2.5 Emissions Equivalence (9:1)            -9.0             1.0
                                         -------------------------------
    Total Emission Reductions Achieved..            16.4             3.0
------------------------------------------------------------------------

    In sum, the CARB Staff Report demonstrates that implementation of
State and District measures achieved a total of 16.4 tpd of
NOX emission reductions and 3.0 tpd of direct
PM2.5 emission reductions that have not previously been
credited as part of the attainment demonstration in the 2008
PM2.5 Plan and that may, therefore, be credited toward the
State's outstanding obligation to achieve 12.9 tpd of NOX
emission reductions and 3.0 tpd of direct PM2.5 emission
reductions by the beginning of 2014.
    Based on these evaluations, we propose to determine that California
has complied with all requirements and commitments pertaining to the
SJV area in the implementation plan.
4. Demonstration That the Implementation Plan Includes the Most
Stringent Measures
    We interpret this criterion to mean that the State must demonstrate
to the EPA's satisfaction that its serious area plan includes the most
stringent measures that are included in the implementation plan of any
state, or achieved in practice in any state, and can feasibly be
implemented in the area.
    As discussed above in section V.D, because of the substantial
overlap in the source categories and controls evaluated for BACM and
those evaluated for MSM, we present our evaluation of the 2015
PM2.5 Plan's provisions for including MSM alongside our
evaluation of the Plan's provisions for implementing BACM for each
identified source category. For the reasons provided in section V.D and
further in the EPA's SJV Rules TSD, we propose to determine that the
2015 PM2.5 Plan provides for the implementation of MSM for
sources of direct PM2.5 and PM2.5 precursors as
expeditiously as practicable, in accordance with the requirement in CAA
section 188(e).
5. Demonstration of Attainment by the Most Expeditious Alternative Date
Practicable
    Section 189(b)(1)(A) of the CAA requires that each Serious area
plan include a demonstration (including air quality modeling) that the
plan provides for attainment of the PM2.5 NAAQS by the
applicable attainment date or, where the State is seeking an extension
of the attainment date under section 188(e), a demonstration that
attainment by that date is impracticable and that the plan provides for
attainment by the most expeditious alternative date practicable. We
discuss below our evaluation of the modeling approach in the Plan, the
State's basis for excluding one 24-hour data point from the modeling
analysis, and the control strategy in the Plan for attaining the 1997
annual and 24-hour PM2.5 NAAQS by the most expeditious
alternative dates practicable.
Evaluation of Air Quality Modeling Approach and Results
    The EPA's PM2.5 modeling guidance \374\ (``Modeling
Guidance'' and

``Modeling Guidance Update'') recommends that a photochemical model,
such as CAMx or CMAQ, be used to simulate a base case, with
meteorological and emissions inputs reflecting a base case year, to
replicate concentrations monitored in that year. The model application
to the base case year undergoes a performance evaluation to ensure that
it satisfactorily agrees with concentrations monitored in that year.
The model may then be used to simulate emissions occurring in other
years required for a plan, namely the base year (which may differ from
the base case year) and future year.\375\ The modeled response to the
emission changes between those years is used to calculate Relative
Response Factors (RRFs), which are applied to the design value in the
base year to estimate the projected design value in the future year for
comparison against the NAAQS. Separate RRFs are estimated for each
chemical species component of PM2.5, and for each quarter of
the year, to reflect their differing responses to seasonal
meteorological conditions and emissions. Since each species is handled
separately, before applying an RRF the base year design value must be
speciated using available chemical species measurements, that is, each
day's measured PM2.5 comprising the design value must be
split into its species components. The Modeling Guidance provides
additional detail on the recommended approach.\376\
---------------------------------------------------------------------------

    \374\ ``Guidance on the Use of Models and Other Analyses for
Demonstrating Attainment of Air Quality Goals for Ozone,
PM2.5, and Regional Haze,'' EPA-454/B-07-002, April 2007
(``Modeling Guidance''); and ``Update to the 24 Hour
PM2.5 NAAQS Modeled Attainment Test,'' Memorandum from
Tyler Fox, Air Quality Modeling Group, OAQPS, EPA to Regional Air
Program Managers, EPA, June 28, 2011 (``Modeling Guidance Update'').
    \375\ In this section, we use the terms ``base case,'' ``base
year'' or ``baseline,'' and ``future year'' as described in section
3.5 of the EPA's Modeling Guidance. The ``base case'' modeling
simulates measured concentrations for a given time period, using
emissions and meteorology for that same year. The modeling ``base
year'' (which can be the same as the base case year) is the
emissions starting point for the plan and for projections to the
future year, both of which are modeled for the attainment
demonstration. See Modeling Guidance at pp. 33-34. Note that CARB
sometimes uses ``base year'' synonymously with ``base case'' and
``reference year'' instead of ``base year.''
    \376\ Modeling Guidance Update at 43 ff.
---------------------------------------------------------------------------

    The attainment demonstration in the 2015 PM2.5 Plan is
based on modeling performed for the 2008 PM2.5 Plan, but
that modeling is used in a streamlined way, by employing scaling. The
attainment demonstration approach in the 2015 PM2.5 Plan is
covered in its Chapter 4 (``Classification and Attainment'') and
Appendix F (``Attainment Demonstration''), with several further details
in Appendix A (``Weight of Evidence Analysis'') of the CARB Staff
Report. For the modeling used in this Plan, the base case year was
2000, the base year was 2012, and the future years were 2018 and 2020
for the 24-hour and annual PM2.5 standards, respectively.
CARB scaled the results from modeling performed for the 2008
PM2.5 Plan, assuming the same relative response to emission
changes applies in the time frame for the current Plan. Starting from
the RRFs from the 2008 PM2.5 Plan, which reflect the
emission changes from the base year to the future year in that plan
(2005 to 2014), CARB scaled those RRFs to reflect the current 2015
PM2.5 Plan's base year to future year emission changes (2012
to 2020 for the annual standard, and 2012 to 2018 for the 24-hour
standard).
    The formula in the 2015 PM2.5 Plan \377\ for scaling an
RRF is based on the definition of an RRF as (modeled future
concentration)/(modeled base year concentration), and on the assumption
that the modeled percent change in concentration per percent change in
emissions is the same for the 2015 PM2.5 Plan as it was for
the 2008 PM2.5 Plan. As shown in section IV.A of the EPA's
General TSD for this action, these assumptions lead to the Plan
formula. Since the RRF includes the modeled effect of emission changes,
accounting for their temporal and spatial distribution and their
chemistry, the scaling approach used in the 2015 PM2.5 Plan
differs from a simple ``rollback'' scaling (which would merely assume
that the percent concentration change is identical to the percent
emissions change).
---------------------------------------------------------------------------

    \377\ 2015 PM2.5 Plan, Chapter 4, p. 4-8, and
Appendix F, p. F-4.
---------------------------------------------------------------------------

    CARB's procedure for using emissions from the two plans in the RRF
scaling formula differed to some extent between the two plans due to
data availability, even though ideally they would be treated in the
same way. The reason the scaling is being done rather than new modeling
is that modeling inventories were not available for the base and future
years of the 2015 PM2.5 Plan. Only the planning inventories
are available; they cover all the source categories, but do not reflect
the allocation of the emissions to all the grid squares in the modeling
domain and to all the hours of the year, a considerable undertaking
necessary for input to the model. Absent the future modeling
inventories, the most consistent way to perform the scaling would be to
use planning inventories from both the new and old plans. Because the
scaling is done for each chemical species, the inventories used should
also be speciated using the same procedure, by applying speciation
profiles for the various emission source categories. Unfortunately, the
old speciation profiles for the 2008 PM2.5 Plan were not
available, so the planning inventory from the 2008 PM2.5
Plan could not be speciated in the same way as the 2015
PM2.5 Plan planning inventory could. Therefore, CARB used
the modeling inventory from the 2008 PM2.5 Plan, which did
have a speciation procedure comparable to that available for the 2015
PM2.5 Plan planning inventory. In sum, in calculating the
RRF scaling factors, CARB used the modeling inventory to compute
percent emission changes for the 2008 PM2.5 Plan and used
the planning inventory for emission changes for the 2015
PM2.5 Plan.378 379
---------------------------------------------------------------------------

    \378\ 2015 PM2.5 Plan, Appendix F, p. F-4.
    \379\ Modeling the ambient PM2.5 components of
elemental carbon (EC) and organic carbon (OC) and geological
material requires emissions for those, derived from speciation
profiles of the various emission source categories. The RRF scaling
also requires separate EC and OC emissions. But planning
inventories, such as that available for the 2008 plan, generally
report only direct PM2.5 emissions, the total of these
species.
---------------------------------------------------------------------------

    CARB's modeling domain is somewhat larger than the SJV
nonattainment area, so emission totals differ between the modeling
inventory and the planning inventory. But we expect that percent
changes are comparable because both the modeling inventories and
planning inventories reflect emissions from the same types of sources
and in similar proportions. The inventories also reflect similar
controls, for example statewide motor vehicle emissions controls, where
motor vehicles are the main source of NOX. We also expect
the ratios of the percent changes, i.e., the RRF scaling factors
themselves, to be comparable given discrepancies between the modeling
and planning inventories would typically be similar for the two plans
used in the ratio, and hence canceled out to an extent.
    The 2015 PM2.5 Plan provided several bases to support
the use of a scaling approach premised on the 2008 PM2.5
Plan model response. The base case in the previous modeling was based
on extensive measurements during the 2000 CRPAQS study,\380\ and the
underlying meteorological conditions leading to high PM2.5
concentrations in the 2000-2001 winter were similar to those in the
2013-2014 winter, including persistent pressure ridges, surface
inversions, cool temperatures,

and low winds.\381\ Also, the 2004-2006 PM2.5 species
composition data that CARB used for speciating PM2.5
concentrations in the 2008 PM2.5 Plan show a similar
composition to 2011-2013 speciation measurements that CARB used in the
2015 PM2.5 Plan to speciate design values prior to applying
RRFs, as seen in composition pie charts for Bakersfield, Fresno,
Modesto, and Visalia.\382\
---------------------------------------------------------------------------

    \380\ 2000 California Regional Particulate Air Quality Study
(CRPAQS); descriptive documents available on CARB's ``Central
California Air Quality Studies'' Web site at http://www.arb.ca.gov/airways.
    \381\ 2015 PM2.5 Plan, Appendix F, p. F-4, and WOEA,
p. A-5.
    \382\ 2015 PM2.5 Plan, Appendix F, Attachment A, p.
F-8 to F-10.
---------------------------------------------------------------------------

    These observations indicate that the 2013 PM2.5 design
values for the current 2015 PM2.5 Plan would respond in a
way similar to the 2008 PM2.5 Plan modeling. An alternative
would have been to use modeling from the 2012 PM2.5 Plan,
which had a 2007 meteorology and emissions base case, which is more
recent than that in the 2008 PM2.5 Plan. However, it modeled
only the first and fourth quarters, the only quarters needed to address
the 24-hour NAAQS; the 2008 PM2.5 Plan modeled the entire
year, and so was suitable for assessing both the 24-hour and the annual
PM2.5 NAAQS.
    CARB calculated an RRF from the scaling formula using the
concentration of each PM2.5 chemical species, with emissions
from the corresponding precursor. CARB used percent changes in
emissions of NOX, SOX, Organic Carbon (OC),
Elemental Carbon (EC), and other (direct PM2.5 less OC and
EC), to scale the RRF for the corresponding ambient PM2.5
component: Nitrate (NO3-), sulfate
(SO4-2), OC, EC, and geological material (also
called ``other'' or ``dust''). For the ammonium component, which is
present in ammonium nitrate and ammonium sulfate, a choice must be made
as to which precursor emissions, either NOX or
SO2, should be used in scaling ammonia; CARB used
NOX.
    This is in line with information in the Plan indicating that
ammonium nitrate formation responds far more to NOX emission
changes than to ammonia changes. The Plan also noted that sulfate is a
much smaller ambient component than nitrate, so that ammonium scales
more with NOX than with SO2.\383\ Conceivably
some combination of precursor emissions could have been used for
scaling ammonium, but that would require a plausibility argument about
how to reflect the actual chemistry involved, a complication that would
obscure both the relative simplicity of direct scaling and the more
comprehensive consideration of chemistry already present in the
modeling being scaled. Another point about the choice of NOX
is that ammonium concentrations were independent of ammonia emissions,
since the latter was not used, and so inherently cannot respond to
increases or decreases of ammonia that occur during the planning
period.
---------------------------------------------------------------------------

    \383\ 2015 PM2.5 Plan, Appendix F, p. F-5.
---------------------------------------------------------------------------

    As discussed in section V.C of this notice, modeling for the 2012
PM2.5 Plan showed that there is a small ambient response to
ammonia changes. Additionally, annual average ammonia emissions in the
planning inventory increase by 8.6% from 2012 to 2020, which suggests
that the ammonium contribution to projected design values may be higher
than stated in the Plan. However, this is of little concern since the
pre-scaled RRFs for ammonium, nitrate, and sulfate were based on actual
modeling for the 2008 PM2.5 Plan; they take into account the
atmospheric chemistry and the ambient effects due to ammonia changes
during 2005-2014, when the annual average ammonia emissions increased
by 18.1%.
    Aside from the RRFs themselves, the procedure that CARB followed in
the 2015 PM2.5 Plan for projecting design values is
consistent with the recommendations in the Modeling Guidance. The steps
included using daily speciation data and the SANDWICH approach \384\ to
split daily measured PM2.5 concentrations into their
chemical components, taking quarterly averages (of all days for the
annual standard, and of the highest 10% or so of days for the 24-hour
standard), applying RRFs to get future component concentrations,
summing to total PM2.5, and finally averaging over quarters
and years to estimate the future design value.
---------------------------------------------------------------------------

    \384\ Sulfate, Adjusted Nitrate, Derived Water, Inferred
Carbonaceous mass material balance approach: Modeling Guidance, p.
47; Frank, N., 2006: ``Retained Nitrate, Hydrated Sulfates, and
Carbonaceous Mass in Federal Reference Method Fine Particulate
Matter for Six Eastern U.S. Cities,'' J. Air Waste Management
Assoc., 56, 500-511.
---------------------------------------------------------------------------

    Two aspects of the Plan's approach to modeling differ from the
Modeling Guidance recommendations. First, for the 24-hour
PM2.5 NAAQS, the RRFs were applied to a single high value
per quarter to represent the potential 98th percentile, as opposed to
applying RRFs to multiple high individual days in each quarter, and
then choosing the 98th percentile. The former approach is consistent
with the original Modeling Guidance, before it was updated to the
latter approach by the June 28, 2011 Modeling Guidance Update.\385\ The
latter approach is intended to allow for the shifting of high days
between quarters as emission controls are applied: a day that has a
concentration in the top 10% in the autumn may more strongly respond to
controls and no longer be in the top 10%, while a summer day may
respond less to controls and end up being in the post-control top 10%.
Because winter PM2.5 concentrations are significantly higher
than those in the other seasons, such shifting is very unlikely to be
an issue in the SJV.
---------------------------------------------------------------------------

    \385\ Modeling Guidance, p. 58 and Modeling Guidance Update, p.
B-2 (Steps 1, 4, and 5).
---------------------------------------------------------------------------

    Second, the Modeling Guidance recommends that RRFs be applied to
the average of three three-year design values \386\ (e.g. using data in
2010-2012, 2011-2013, and 2012-2014), whereas the Plan used just the
single 2013 design value (2011-2013 data). The 2011-2013 period for the
2013 design value is centered on the Plan's 2012 base year, as the
Modeling Guidance recommends. One reason for the longer period in EPA's
recommendation is that the additional averaging provides some stability
in the estimate.
---------------------------------------------------------------------------

    \386\ Modeling Guidance, p. 22; and Modeling Guidance Update, p.
B-1.
---------------------------------------------------------------------------

    Although the Plan's procedure is not entirely consistent with EPA
guidance, we find it acceptable in this context given the time
constraints imposed by EPA's April 2015 reclassification of the SJV
area \387\ and the available modeling analyses. Despite the presence of
scaling at a key step, CARB's approach remains a modeled attainment
demonstration as required by section 189(b)(1)(A) of the Act. It relies
on photochemical modeling that EPA reviewed and approved \388\ for the
2008 PM2.5 Plan, and which remains sufficiently
representative of PM2.5 formation in the SJV.
---------------------------------------------------------------------------

    \387\ 80 FR 18528 at 18530 (April 7, 2015) (noting unusually
short timeframe for State's development and submission of a plan to
provide for attainment of the 1997 PM2.5 NAAQS by the
Serious area attainment date, which is December 31, 2015).
    \388\ ``Technical Support Document for the Proposed Action on
the San Joaquin Valley 2008 PM2.5 Plan and the San
Joaquin Valley Portions of the Revised 2007 State Strategy,'' EPA
Region 9, November 8, 2010, for proposed approval in 75 FR 74518
(November 30, 2010); final approval was in 76 FR 69896 (November 9,
2011).
---------------------------------------------------------------------------

    Three other considerations give some reassurance of the
acceptability of a scaling approach. First, EPA's 2014 draft modeling
guidance explicitly recognizes that ``there may be plausible
alternative means of calculating the relative response factors [RRFs]
that can differ from the approaches recommended.'' \389\ While this
2014 draft guidance does not

specifically address the alternative of scaled RRFs, it indicates, as
does the Modeling Guidance, that alternatives to the recommended
procedures are acceptable where adequately supported. Second, even the
recommended RRF procedure involves model sensitivity derived from one
period being applied to another: RRFs are computed using a single
year's modeled response to emissions changes, but are assumed to be
applicable to all five years composing the average over three design
values. This consideration makes the 2015 PM2.5 Plan's
application of the model response from one period to another analogous
to the application more broadly envisioned by the Modeling Guidance.
---------------------------------------------------------------------------

    \389\ ``Modeling Guidance for Demonstrating Attainment of Air
Quality Goals for Ozone, PM2.5, and Regional Haze'',
DRAFT December 2014, EPA OAQPS, p. 99.
---------------------------------------------------------------------------

    Finally, while scaling itself is relatively crude, the scaling of
RRFs is less so. The procedure is not a simple scaling of an emission
total, but reflects the geographic and temporal distribution of the
emissions sources and the emission changes, since it is based on
modeling. The pattern of emission changes during the span of the 2015
PM2.5 Plan does not exactly match the changes modeled for
the span of the 2008 PM2.5 Plan, but many of the emission
reductions continue the effect of existing controls on the same types
of sources, so the patterns of the emissions changes are unlikely to be
very different. For example, continued vehicle NOX emission
reductions occur over much the same roadway network and direct
PM2.5 reductions from controls on wood burning are largely
achieved from the same residential areas.
    Late in EPA's review process, EPA and CARB found that the scaling
factor for EC had been applied to the RRF for OC and the product used
as the RRF for EC, and vice versa.\390\ Because the original RRFs for
OC were larger than those for EC, and remained so after scaling,
applying the smaller EC scaled RRFs to OC made the projected OC
concentration smaller than it should have been. Conversely, projected
EC was larger than it should have been. Because OC has a larger ambient
contribution than EC, the OC effect dominates. The net result of the
EC-OC reversal is that the projected design values for the attainment
demonstration were underestimated. CARB estimates that the 2020 annual
design value for Madera increased from the 2015 PM2.5 Plan's
original 15.0 [micro]g/m\3\ to a corrected value of 16.2 [micro]g/
m\3\,\391\ which is above the 1997 annual PM2.5 NAAQS.
---------------------------------------------------------------------------

    \390\ Letter from K. Magliano, CARB to K. Drake, EPA Region 9,
August 12, 2015. See also, Memo to file, ``Call with California Air
Resources Board regarding letter about reversal of elemental and
organic carbon,'' S. Bohning, EPA Region 9, September 18, 2015.
    \391\ Id., Attachment A (``Revised San Joaquin Valley
PM2.5 Design Values'').
---------------------------------------------------------------------------

    However, CARB presents compelling reasons for discounting this high
Madera projected 2020 annual design value. The starting point for the
scaled modeling projection is the 2013 design value--the average of
annual means during 2011-2013. The 2011 monitoring data included within
that 2013 design value appears anomalous, as documented in the WOEA at
Appendix A2 (``Assessment of the Representativeness of 2011
PM2.5 Beta Attenuation Monitor Data from Madera'') and
Attachment B to CARB's Technical Clarifications of August 12, 2015
(``Attachment B''). We refer herein to figures and tables in Appendix
A2 of the WOEA as ``S.R. App. A2, Figure 2.''
    EPA's regulations require that monitoring data for comparison to
the NAAQS be collected using specific equipment and procedures to
ensure accuracy and reliability.\392\ For each NAAQS, the default
monitoring equipment and the procedures for operating it are termed the
Federal Reference Method (FRM); an alternative approach, termed a
Federal Equivalent Method (FEM) may also be used if it is demonstrated
to give results comparable to an FRM monitor. The Met One Beta
Attenuation Monitor (BAM) 1020 is an example of an FEM that provides
continuous hourly PM2.5 concentrations compared to the FRM's
24-hour average PM2.5 concentrations. This is useful for a
number of purposes, including real-time forecasting for deciding when
to issue public advisories and wood burning restrictions, as well as
for evaluating air quality model performance. BAMs are deployed at
multiple sites in the SJV, including Madera (the ``Madera-City'' site,
AQS ID 06-039-2010).\393\
---------------------------------------------------------------------------

    \392\ 40 CFR parts 53 and 58.
    \393\ 2015 PM2.5 Plan, Chapter 4, Table 4-3
(``Projected 2020 Annual and 2018 24-hour Design Values''), p.4-9.
---------------------------------------------------------------------------

    As described in the S.R. App. A2, 2011 was the first full year of
data collected by the Madera BAM, and the concentrations were
unexpectedly high in comparison with other monitoring sites, including
both BAMs and FRM monitor sites. During 2011-2013, annual
concentrations at Madera were some 30% higher than at Fresno, and as
much as 100% higher during the summer, historically the season with the
lowest PM2.5.\394\ This was unexpected because historically
there has been a north-to-south increasing gradient of concentrations,
with northern sites like Stockton and Merced at the low end, and
southern sites like those in Bakersfield at the high end, and with
central sites like Fresno somewhere in between.\395\ This gradient is
consistent with the greater potential for ventilation at the northern
end of the SJV, nearest the opening to the ocean at the Golden Gate,
and the lower ventilation at the southern end, surrounded by mountains.
Madera and Fresno concentrations are highly correlated,\396\ suggesting
common meteorological influences at the two sites, as opposed to
additional emission sources contributing at Madera.
---------------------------------------------------------------------------

    \394\ S.R. App. A2, Figures 3 and 4, and Tables 1 and 2.
    \395\ S.R. App. A2, Figure 2.
    \396\ S.R. App. A2, Figure 3.
---------------------------------------------------------------------------

    Various checks on the monitor and its operation were made over time
without affecting the high readings, but in April 2014, adjustments
were made as a result of checking the zero point of the instrument
using outdoor air, rather than indoor air (both are permissible;
outdoor air could be more representative of the conditions the
instrument normally operates under).\397\ After that time, Madera
concentrations shifted to lower values,\398\ conformed better to the
known north-south gradient,\399\ and tracked closely with the monitored
data from the Merced-Coffee Road site about 30 miles to the North,
which is expected given the two monitors' proximity to one another and
similar geographic conditions.\400\ They also agreed better with
measurements at a new FRM installed in July 2014 at the Madera
site.\401\ ARB concluded that the 2011 ``BAM data at Madera appear to
be biased high due to sampling artifacts . . . not representative of
air quality in the central portion of the Valley''.\402\
---------------------------------------------------------------------------

    \397\ ``BAM 1020 Particulate Monitor Operation Manual, BAM-1020-
9800 Rev K'', Met One Instruments, Inc. 2008; Memorandum from Tim
Hanley, Office of Air Quality Planning and Standards, EPA to Met One
BAM Users, ``RE: Zero Tests on the Met One BAM 1020,'' October 5,
2012.
    \398\ S.R. App. A2, Figure 8.
    \399\ S.R. App. A2, Figure 9.
    \400\ Letter from K. Magliano, CARB to A. Steckel, EPA Region 9,
August 12, 2015, Attachment B, p. 2.
    \401\ S.R. App. A2, Figures 12 and 13.
    \402\ S.R. App. A2, p.A2-9.
---------------------------------------------------------------------------

    The 2015 PM2.5 Plan nevertheless included the 2011
Madera data and 2013 design value in the attainment demonstration,
because up until recently the issue appeared to be moot, as despite the
high starting point concentration the modeling predicted a 2020 annual
concentration of 15.0 [micro]g/m\3\, which attains the 1997 annual
PM2.5 NAAQS. The discovery of the EC-OC reversal described
above brings the issue to the fore because there is no

room for the increase it causes in the 2020 Madera design value.
    The fact that 2011-2013 Madera BAM concentrations are higher than
values at the Fresno FRM and other sites does not in itself prove they
are incorrect; it is conceivable that unknown sources were contributing
there. Also, the later agreement between the lower Madera BAM and FRM
concentrations could be explained as sources that are now emitting
less, or that are contributing less at the monitor due to different
wind patterns. Nevertheless, the mismatch with the historical gradient
pattern, the unexpectedly but only temporarily high readings that
declined after an adjustment in operation, and the current lower FRM
readings do suggest that the 2011 Madera concentrations were anomalous.
EPA believes that the 2011-2013 readings at the Madera site are not
known to be representative of air quality for Madera and not
sufficiently certain to drive the SJV control strategy, or to
invalidate the conclusion of the attainment demonstration that the SJV
will attain the 1997 annual NAAQS in 2020.
    CARB explored two alternative scenarios to estimate annual average,
ambient PM2.5 values in 2020 for the Madera site.\403\ Under
the first scenario, CARB substituted the 2014 design value of 15.8
[micro]g/m\3\ at the Madera site for its 2013 design value and
estimated that the 2020 Madera design value would be 14.1 [micro]g/
m\3\. For the second scenario, CARB substituted the annual 2011 data
from the Merced-Coffee Road site, adjusted upward to reflect the
typically slightly higher values at Madera, resulting in an estimated
2020 Madera design value of 14.9 [micro]g/m\3\. Both scenarios are
reasonable alternatives to estimating the 2020 Madera design value for
the SJV attainment planning purposes for the 1997 annual
PM2.5 NAAQS. Accordingly, the Bakersfield-Planz site, which
would have a corrected 2020 design value of 15.0 [micro]g/m\3\, would
become the design value monitor for the SJV, as would be expected under
the historic observation of a north-to-south increasing gradient of
concentrations.\404\
---------------------------------------------------------------------------

    \403\ Letter from K. Magliano, CARB to A. Steckel, EPA Region 9,
August 12, 2015, Attachment B, pp. 3-4.
    \404\ Note that if the unexpectedly high concentrations seen in
2011-2013 are due to real phenomena affecting air quality, then they
would be expected to occur again at some point in the intervening
years between now and the projected attainment year of 2020. If they
do occur again, then they would influence the monitored attainment
status at that time, and hence any request for SJV to be designated
attainment.
---------------------------------------------------------------------------

    EPA accepts the scaled modeling approach of the attainment
demonstration in the 2015 PM2.5 Plan, which was the product
of extended discussion between EPA, ARB, and SJVUAPCD. Based on our
review of the modeling approach and results, we propose to conclude
that the 2015 PM2.5 Plan adequately demonstrates that the
SJV area will attain the 1997 annual PM2.5 NAAQS by December
31, 2020 and attain the 1997 24-hour PM2.5 NAAQS by December
31, 2018. We recommend that CARB reassess the status of the modeled
attainment of the 1997 24-hour and annual PM2.5 NAAQS as
part of the new modeling required for SIP revisions addressing the 2006
and 2012 PM2.5 NAAQS.
Evaluation of Bakersfield-Planz Data Exclusion for May 5, 2013
    As described in the 2015 PM2.5 Plan, the State and
District based the attainment demonstration on ambient measurements
during 2011-2013.\405\ The 24-hour PM2.5 concentration of
167.3 [micro]g/m\3\ measured at the Bakersfield-Planz monitoring site
(AQS ID: 06-029-0016) on May 5, 2013 was not included in the attainment
demonstration analyses due to its unrepresentativeness for purposes of
attainment planning for the SJV as a whole. Therefore, the modeled
projections for the 2020 annual PM2.5 design values and 2018
24-hour design values \406\ and the discussion of the modeling results
in Appendix F, section F.4 of the Plan are based on data that exclude
the May 5, 2013 24-hour data point from the Bakersfield-Planz
monitoring site.
---------------------------------------------------------------------------

    \405\ 2015 PM2.5 Plan, Appendix F, p F-4.
    \406\ 2015 PM2.5 Plan, Appendix F, Table F-1.
---------------------------------------------------------------------------

    The Plan provides an assessment of the representativeness of this
data for purposes of inclusion in the attainment demonstration analyses
\407\ and concludes that:
---------------------------------------------------------------------------

    \407\ 2015 PM2.5 Plan, Appendix F, Attachment B:
Assessment of the Representativeness of the PM2.5 Value
Recorded at the Bakersfield-Planz Monitoring Site on May 5, 2013.
---------------------------------------------------------------------------

    ``In summary, comparison of the 167.3 [micro]g/m\3\ concentration
measured on May 5, 2013, to values typical for this season as well as
comparison to values measured throughout the Valley on the same day,
combined with the record high fugitive dust and elemental species
concentrations, indicate that the monitor was impacted by microscale
sources that are not representative of the neighborhood spatial scale
the monitor is intended to represent. Therefore, this value is not
included in modeling analysis for the San Joaquin Valley 2015
PM2.5 Plan.''
    The assessment provided in the Plan \408\ based this conclusion on:
(1) Representativeness of Bakersfield-Planz PM2.5 data;
\409\ (2) potential fugitive dust sources affecting the Bakersfield-
Planz site; \410\ and (3) meteorology at the Bakersfield-Planz
site.\411\
---------------------------------------------------------------------------

    \408\ 2015 PM2.5 Plan, Appendix F, Attachment B.
    \409\ 2015 PM2.5 Plan, Appendix F, Attachment B,
Section B.
    \410\ 2015 PM2.5 Plan, Appendix F, Attachment B,
Section C.
    \411\ 2015 PM2.5 Plan, Appendix F, Attachment B,
Section D.
---------------------------------------------------------------------------

    Information provided regarding the representativeness of
Bakersfield-Planz data included analyses of San Joaquin Valley seasonal
PM2.5 concentrations \412\ and elemental species
composition.\413\ The assessment provided PM2.5 data on the
highest concentrations throughout the Valley since 2000 and shows that
the May 5, 2013 Bakersfield-Planz value was unusually high compared to
historical trends since 2000. Further, this data point was also
unusually high compared to other sites in the San Joaquin Valley on the
same day.\414\ The species composition analyses show that the primary
content of the particulate matter was fugitive dust and that the level
of the dust was over four times higher than the next highest value
observed in the entire California network based on 14 years of
available data. In addition, total elemental species and other chemical
species were found to be unusually high.
---------------------------------------------------------------------------

    \412\ 2015 PM2.5 Plan, Appendix F, pp. F-11 to F-13.
    \413\ Id., pp. F-13 to F-14.
    \414\ Id., pp. F-12 to F-13.
---------------------------------------------------------------------------

    The State and District's assessment of potential fugitive dust
sources affecting the Bakersfield-Planz site was based on an evaluation
of aerial photos to identify sources and field investigation by
District enforcement staff.\415\ The assessment found no documented
dust violations at any nearby sources and identify the likely source of
the dust was from the open areas immediately adjacent to the monitor,
suggesting a localized microscale impact.
---------------------------------------------------------------------------

    \415\ Id., pp. F-14 to F-16.
---------------------------------------------------------------------------

    The third part of the assessment evaluated meteorology at the
Bakersfield-Planz Monitoring Site.\416\ Wind speeds on May 5, 2013 were
compared to other days in May 2013 and also to other high wind days at
the Bakersfield-Planz site. The wind speeds were in excess of 25 mph
for over eight hours on May 5, 2013. The meteorology indicates that
Bakersfield-Planz experienced a high wind event on May

5, 2013 that was unusual in terms of wind speed and duration.
---------------------------------------------------------------------------

    \416\ Id., pp. F-17 to F-18.
---------------------------------------------------------------------------

    Overall, EPA agrees with the evidence provided that the
Bakersfield-Planz monitor was affected by an unusual high wind dust
event on May 5, 2013 that resulted in anomalous PM2.5
concentrations on that day. EPA believes that it is appropriate to omit
this data point from the attainment demonstration based on EPA's 2013
guidance on exceptional events.\417\ Regarding the inclusion of event-
affected data for attainment demonstrations, EPA's 2013 guidance says:
---------------------------------------------------------------------------

    \417\ Memorandum from Steven D. Page, Director Office of Air
Quality Planning and Standards, to Regional Air Directors, I-X,
``Interim Guidance to Implement Requirements for the Treatment of
Air Quality Monitoring Data Influenced by Exceptional Events,'' May
10, 2013 (``2013 Exceptional Events Guidance'').
---------------------------------------------------------------------------

    ``An air agency incorporating the event-related concentration in a
design value used for a prospective attainment demonstration might seem
to need more emission reductions to attain the NAAQS by its attainment
deadline than is actually the case. The EPA plans to more formally
address this topic on a pollutant/NAAQS basis, the first of which will
be ozone guidance in the preamble of a soon-to-be-proposed rulemaking
on SIP requirements for areas designated nonattainment for the 2008
ozone NAAQS. Until the planned guidance for a pollutant and NAAQS of
interest is issued, air agencies should consult with their EPA regional
office if they face this situation.'' \418\
---------------------------------------------------------------------------

    \418\ Id.
---------------------------------------------------------------------------

    EPA reviewed PM2.5 data in AQS for the SJV since 2010
and identified four days flagged with high wind exceptional event
requests for exclusion. These PM2.5 high wind dust events do
not appear to be recurring events and their inclusion in the attainment
demonstration therefore would not accurately reflect the effect of
controls during more typical conditions at the Bakersfield-Planz
monitoring site.\419\ Based on these reviews, EPA agrees with the
State's and District's assertion that the May 5, 2013 concentrations at
Bakersfield-Planz were due to an unusual PM2.5 high wind
dust event that would not be appropriate to include in the attainment
demonstration.
---------------------------------------------------------------------------

    \419\ EPA also reviewed PM10 data in AQS for the SJV
since 2010 and identified eight days flagged with high wind
exceptional event request for exclusion, which indicate that
PM10 high wind dust events recur and should be subject to
reasonable controls in accordance with the 2013 Exceptional Events
Guidance.
---------------------------------------------------------------------------

    In addition to EPA's 2013 guidance on exceptional events, EPA also
considered the monitoring requirements for PM2.5. In
particular, 40 CFR part 58, Appendix D, section 4.71(b) specifies for
PM2.5:
    ``The required monitoring stations or sites must be sited to
represent area-wide air quality. These sites can include sites
collocated at PAMS. These monitoring stations will typically be at
neighborhood or urban-scale; however, micro-or middle-scale
PM2.5 monitoring sites that represent many such locations
throughout a metropolitan area are considered to represent area-wide
air quality.''
    Based on the information provided in the Plan, EPA agrees that the
Bakersfield-Planz concentrations on May 5, 2013 appear to have been
affected by a localized event; therefore, it was neither representative
of neighborhood scale concentrations, nor occurring at many locations.
EPA agrees with the State and District that the May 5, 2013
concentrations at Bakersfield-Planz were not representative of area-
wide, typical PM2.5 concentrations in San Joaquin Valley.
    Based on the technical analyses provided in the Plan and EPA
guidance and requirements as cited in this section, EPA agrees with the
State and District that the May 5, 2013 Bakersfield-Planz 24-hour
PM2.5 data point resulted from a localized, anomalous event
that can be omitted from the attainment demonstration analyses.
Evaluation of Control Strategy
    The attainment control strategy in the 2015 PM2.5 Plan
consists of State and District baseline measures that continue to
achieve emission reductions and four additional control measures that
the District either recently revised or, in one case, has committed to
revise in 2016. With respect to baseline measures for stationary and
area sources, the District identified the source categories under its
jurisdiction and their projected emission levels in Appendix B, section
B.2.2 (``Emissions Inventory Documentation'') and described each of the
District measures that apply to these source categories in section
B.2.2.3 of the Plan (``Control Profiles'').\420\ All but one of the 55
District control measures listed in section B.2.2.3 of the Plan have
been approved into the California SIP.\421\
---------------------------------------------------------------------------

    \420\ 2015 PM2.5 Plan, Appendix B, pp. B-23 to B-31.
See also, within this section, Table B-8 (``District Rules Included
in the SIP Inventory'').
    \421\ See EPA Region 9's Web site for information on District
control measures that have been approved into the California SIP,
available at: http://yosemite.epa.gov/r9/r9sips.nsf/Agency?ReadForm&count=500&state=California&cat=San+Joaquin+Valley+Unified+APCD-Agency-Wide+Provisions. Of the District measures
identified in Appendix B of the Plan, only Rule 4691 (``Vegetable
Oil Processing Operations''), which limits VOC emissions from
vegetable oil processing operations, is not currently approved into
the California SIP. EPA approved a previous version of this rule
(Rule 461.2) into the SIP on January 18, 1994 (59 FR 2535).
---------------------------------------------------------------------------

    With respect to mobile sources, the State identified the source
categories and described the EMFAC2014 emission factor model used to
project their future emission levels in Appendix B, sections B.2.2.4
through B.2.2.7 of the Plan.\422\ As explained in section V.D of this
proposed rule, in a separate rulemaking, EPA is proposing to approve
CARB's submitted waiver measures into the SIP and intends to finalize
that rulemaking before taking final action on the 2015 PM2.5
Plan.
---------------------------------------------------------------------------

    \422\ 2015 PM2.5 Plan, Appendix B, pp. B-31 to B-35.
---------------------------------------------------------------------------

    Table 8 below summarizes the emission reductions needed in the SJV
to attain the 1997 24-hour and annual PM2.5 NAAQS by the end
of 2018 and 2020, respectively.

     Table 8--Summary of Direct PM2.5 and NOX Emission Reductions Needed for the 2015 PM2.5 Plan Attainment
                                                  Demonstration
----------------------------------------------------------------------------------------------------------------
                                                  24-hour Standard Attainment by   Annual Standard Attainment by
                                                     2018 (tpd annual average)       2020 (tpd winter average)
                                                 ---------------------------------------------------------------
                                                       PM2.5            NOX            PM2.5            NOX
----------------------------------------------------------------------------------------------------------------
A 2012 emissions inventory \a\..................            61.0           318.5            66.0           332.2
B Emissions inventory after baseline measures...            57.7           213.9            62.8           206.9
C Emissions inventory needed to attain..........            54.4           213.7            60.8           206.5
D Total emission reductions needed by attainment             6.6           104.8             5.2           125.7
 year (A--C)....................................
----------------------------------------------------------------------------------------------------------------
Source: 2015 PM2.5 Plan, CARB Staff Report, Tables 1 and 2, p. 9, except as otherwise noted.
\a\ 2015 PM2.5 Plan, Appendix B, Tables B-1 and B-2.

    The Plan identifies four District measures that will achieve
additional emission reductions beyond baseline measures and contribute
to expeditious attainment of the 1997 PM2.5 NAAQS.\423\
First, Rule 4308 (``Boilers, Steam Generators, and Process Heaters
0.075 to <2 MMBtu/hr''), as amended November 14, 2013, limits
NOX emissions from boilers, steam generators, and process
heaters sized between 0.075 and 2 MMBtu/hr and is projected to achieve
0.0007 tpd of NOX emission reductions by 2018 and 0.0011 tpd
of NOX emission reductions by 2020.\424\ EPA approved this
rule into the California SIP on February 12, 2015.\425\
---------------------------------------------------------------------------

    \423\ 2015 PM2.5 Plan, CARB Staff Report, Tables 1
and 2, p. 9.
    \424\ 2015 PM2.5 Plan, Chapter 7, p. 7-3 and CARB
Staff Report at p. 9.
    \425\ 80 FR 7803 (February 12, 2015).
---------------------------------------------------------------------------

    Second, the District has committed to amend Rule 4692 (``Commercial
Charbroiling'') in 2016 to add requirements for under-fired
charbroilers, with an anticipated compliance date in 2017.\426\ Rule
4692, as approved into the SIP on November 3, 2011, regulates emissions
from chain-driven charbroilers but does not regulate under-fired
charbroilers.\427\ The District projects that its anticipated revisions
to Rule 4692 to regulate under-fired charbroilers will achieve an
additional 0.4 tpd of direct PM2.5 emission reductions in
2018 and 2020.\428\ EPA recently proposed to approve this commitment
into the California SIP.\429\
---------------------------------------------------------------------------

    \426\ 2015 PM2.5 Plan, Chapter 7, section 7.1.2, p.
7-6 and SJVUAPCD Governing Board Resolution 15-4-7A (April 16, 2015)
at paragraph 7.
    \427\ 76 FR 68103 (November 3, 2011).
    \428\ 2015 PM2.5 Plan, Chapter 7 at p. 7-6.
    \429\ 80 FR 1816 at 1833 and 1844 (January 13, 2015).
---------------------------------------------------------------------------

    Emission reductions of 0.4 tpd of direct PM2.5 represent
6.1% of the total PM2.5 emission reductions needed to attain
the 1997 24-hour standard by 2018 and 7.7% of the total
PM2.5 emission reductions needed to attain the 1997 annual
standard by 2020.\430\ These are limited portions of the total
PM2.5 emission reductions needed for expeditious attainment
of the 1997 PM2.5 standards in the SJV. Based on the
District's history of timely meeting similar rule commitments (see
section V.E.3 of this preamble), we find that the District is capable
of fulfilling this commitment. We also find that the commitment to
adopt the amended rule by 2016 is for a reasonable and appropriate
timeframe given the need for PM2.5 emission reductions to
attain by 2018 and 2020. Accordingly, we propose to approve this rule
commitment as part of the control strategy in the 2015 PM2.5
Plan. For a more detailed discussion of this commitment and the
District's evaluations to date, see the EPA's SJV Rules TSD.
---------------------------------------------------------------------------

    \430\ 2015 p.m.2.5 Plan, CARB Staff Report, Tables 1 and 2, p.
9, and Appendix B (``Emissions Inventory''), Tables B-1 and B-2.
---------------------------------------------------------------------------

    Third, the District projects that Rule 4901 (``Wood Burning
Fireplaces and Wood Burning Heaters''), as amended September 18, 2014,
will achieve 2.9 tpd of direct PM2.5 emission reductions by
2018 and 1.6 tpd of direct PM2.5 emission reductions by
2020. Specifically, the District's 2014 rule amendment to lower the
rule's ``no burn threshold'' from 30 [micro]g/m\3\ to 20 [micro]g/m\3\
(24-hour average ambient PM2.5 concentration) for non-EPA
certified, non-District registered wood burning devices is projected to
achieve a winter 24-hour average of 2.2 tpd of direct PM2.5
emission reductions by 2018 and an annual average of 1.1 tpd of direct
PM2.5 emission reductions by 2020.\431\ The 2015
PM2.5 Plan relies on Rule 4901 for an additional 0.7 tpd of
direct PM2.5 emission reductions (winter 24-hour average) by
2018 and an additional 0.5 tpd of direct PM2.5 emission
reductions (annual average) by 2020 resulting from homeowners replacing
high-emitting fireplaces and stoves with low-emitting, EPA-certified
devices.\432\ The EPA recently proposed to approve Rule 4901 into the
California SIP.\433\
---------------------------------------------------------------------------

    \431\ The District calculated these estimates using its
estimates of direct PM2.5 emission reductions for the
120-day wood burning season covered by the rule and ratios of 120/
365 days and 120/180 days for the annual average and winter (24-
hour) average emission reductions, respectively. See SJVUAPCD,
``Final Staff Report for Amendments to the District's Residential
Wood Burning Program,'' Appendix B, (``Emission Reduction Analysis
Amendments to Residential Wood Burning Program'') at B-12, September
18, 2014.
    \432\ The 0.7 tpd and 0.5 tpd emission reduction estimates
assume that 14% of devices subject to Rule 4901 will be replaced by
2018 and that 20% of such devices will be replaced by 2020,
respectively. For a more detailed discussion of these emission
reduction estimates, see the EPA's SJV Rules TSD.
    \433\ 80 FR 58637 (September 30, 2015).
---------------------------------------------------------------------------

    Finally, the District projects that Rule 4905 (``Natural Gas-Fired,
Fan-Type Residential Central Furnaces''), as amended January 22, 2015,
will achieve 0.2 tpd of NOX emission reductions by 2018 and
0.4 tpd of NOX emission reductions by 2020.\434\ This rule
includes a mitigation fee option that allows manufacturers to sell non-
compliant furnaces for 36-month transition periods ranging from 2015 to
2021, depending on unit type.\435\ Based on information in the
District's staff report on Rule 4905, the District estimates emission
reductions of 0.105 tpd of NOX per year from three of the
four types of units, which have compliance dates ranging from April 1,
2015 through October 1, 2016.\436\
---------------------------------------------------------------------------

    \434\ 2015 p.m.2.5 Plan, CARB Staff Report, Tables 1 and 2, p.
9.
    \435\ SJVUAPCD, ``Final Staff Report Amendments to Rule 4905
(Natural Gas-Fired, Fan-Type Central Furnaces,'' January 22, 2015,
p. 9. See also EPA's proposed rule on Rule 4905. 80 FR 68484
(November 5, 2015).
    \436\ SJVUAPCD Rule 4905 as amended January 22, 2015, Table 1
(``NOX Emission Limits and Compliance Schedule''). See
also, SJVUAPCD, ``Final Staff Report Amendments to Rule 4905
(Natural Gas-Fired, Fan-Type Central Furnaces,'' January 22, 2015,
Appendix B, pp. B-9.
---------------------------------------------------------------------------

    The EPA recently proposed to approve Rule 4905 into the California
SIP.\437\ Because the sale of non-compliant units is allowed to varying
degrees in 2018 by manufacturers paying mitigation fees, we propose to
credit Rule 4905 with 0.035 tpd of NOX emission reductions
in 2018 rather than the 0.105 tpd of emission reductions identified in
the District's staff report for the rule. The amount we propose to not
credit (i.e., 0.16 tpd of NOX) represents only 0.2% of the
total winter average NOX reduction from 2012 to 2018.\438\
Using the 24-hour PM2.5 sensitivity of 0.08 [micro]g/m\3\
per ton of NOX emission reduction at the projected 2018
design value site of Bakersfield-California St., as modeled for the
2012 PM2.5 Plan,\439\ this would result in an ambient 24-
hour PM2.5 concentration increase of about 0.013 [micro]g/
m\3\.\440\ This represents a minimal effect on ambient PM2.5
levels and, therefore, does not undermine the Plan's demonstration of
attainment of the 1997 24-hour PM2.5 standard by December
31, 2018.
---------------------------------------------------------------------------

    \437\ 80 FR 68484 (November 5, 2015).
    \438\ Percent of total winter average NOX emission
reductions = 0.16 tpd/104.8 tpd = 0.2%.
    \439\ 2015 PM2.5 Plan, WOEA, Table B-2 (``Modeled
PM2.5 air quality benefit per ton of valley-wide
precursor emission reductions''), p. A-27.
    \440\ Increase in ambient 24-hour PM2.5 concentration
= (0.08 [micro]g/m\3\/ton of NOX emission reduction) *
(0.16 tpd) = 0.013 [micro]g/m\3\.
---------------------------------------------------------------------------

    In sum, the attainment demonstration in the 2015 PM2.5
Plan relies on numerous State and District baseline regulations and
four additional District measures that EPA has either approved or
proposed to approve into the California SIP, all of which collectively
are projected to achieve emission reductions sufficient for the SJV
area to attain the 1997 24-hour PM2.5 standard by 2018 and
the 1997 annual PM2.5 standard by 2020. Table 9 provides a
summary of the emission reductions from the four additional District
measures that we propose to credit toward the Plan's attainment control
strategy.

 Table 9--Summary of EPA Proposed Emission Reduction Credits for Additional District Control Measures Needed for
                                  the 2015 PM2.5 Plan Attainment Demonstration
----------------------------------------------------------------------------------------------------------------
                                                   Annual Standard Attainment by  24-hour Standard Attainment by
                                                     2020 (tpd annual average)       2018 (tpd winter average)
            District control measure             ---------------------------------------------------------------
                                                       PM2.5            NOX            PM2.5            NOX
----------------------------------------------------------------------------------------------------------------
Rule 4308.......................................             0.0          0.0011             0.0          0.0007
Rule 4692.......................................             0.4             0.0             0.4             0.0
Rule 4901.......................................             1.6             0.0             2.9             0.0
Rule 4905.......................................             0.0             0.4             0.0           0.035
----------------------------------------------------------------------------------------------------------------
Source: 2015 PM2.5 Plan, CARB Staff Report, Tables 1 and 2, p. 9.

Conclusion
    As discussed above, the 2015 PM2.5 Plan's air quality
modeling demonstrates that the SJV will attain the 1997 24-hour
PM2.5 standard of 65 [micro]g/m\3\ by December 31, 2018 and
the 1997 annual PM2.5 standard of 15.0 [micro]g/m\3\ by
December 31, 2020. This demonstration is based on expeditious
implementation of the State's and District's BACM and MSM control
strategy for stationary, area, and mobile sources in the 2015
PM2.5 Plan, together with the District's commitment to
achieve additional PM2.5 emission reductions from under-
fired charbroilers through amendments to Rule 4692. Based on these
evaluations, we propose to determine that the 2015 PM2.5
Plan provides for attainment of the 1997 24-hour and annual
PM2.5 standards by the most expeditious alternatives dates
practicable, consistent with the requirements of CAA sections
189(b)(1)(A).

F. Reasonable Further Progress and Quantitative Milestones

1. Requirements for Reasonable Further Progress and Quantitative
Milestones
    CAA section 172(c)(2) requires nonattainment area plans to provide
for reasonable further progress (RFP). In addition, CAA section 189(c)
requires PM2.5 nonattainment area SIPs to include
quantitative milestones to be achieved every three years until the area
is redesignated to attainment and which demonstrate reasonable further
progress (RFP), as defined in CAA section 171(1). Section 171(1)
defines RFP as ``such annual incremental reductions in emissions of the
relevant air pollutant as are required by [Part D] or may reasonably be
required by the Administrator for the purpose of ensuring attainment of
the applicable [NAAQS] by the applicable date.'' Neither subpart 1 nor
subpart 4 of part D, title I of the Act requires that a set percentage
of emissions reductions be achieved in any given year for purposes of
satisfying the RFP requirement.
    RFP has historically been met by showing annual incremental
emission reductions sufficient generally to maintain at least linear
progress toward attainment by the applicable deadline.\441\ As
discussed in EPA guidance in the Addendum, requiring linear progress in
reductions of direct PM2.5 and any individual precursor in a
PM2.5 plan may be appropriate in situations where:
---------------------------------------------------------------------------

    \441\ Addendum at 42015.
---------------------------------------------------------------------------

     the pollutant is emitted by a large number and range of
sources,
     the relationship between any individual source or source
category and overall air quality is not well known,
     a chemical transformation is involved (e.g., secondary
particulate significantly contributes to PM2.5 levels over
the standard), and/or
     the emission reductions necessary to attain the
PM2.5 standard are inventory-wide.\442\
---------------------------------------------------------------------------

    \442\ Id.
---------------------------------------------------------------------------

    The Addendum states that requiring linear progress may be less
appropriate in other situations, such as:
     where there are a limited number of sources of direct
PM2.5 or a precursor,
     where the relationships between individual sources and air
quality are relatively well defined, and/or
     where the emission control systems utilized (e.g., at
major point sources) will result in swift and dramatic emission
reductions.
    In nonattainment areas characterized by any of these latter
conditions, RFP may be better represented as step-wise progress as
controls are implemented and achieve significant reductions soon
thereafter. For example, if an area's nonattainment problem can be
attributed to a few major sources, EPA guidance indicates that ``RFP
should be met by `adherence to an ambitious compliance schedule' which
is likely to periodically yield significant emission reductions of
direct PM2.5 or a PM2.5 precursor.'' \443\
---------------------------------------------------------------------------

    \443\ Addendum at 42015.
---------------------------------------------------------------------------

    Plans for PM2.5 nonattainment areas should include
detailed schedules for compliance with emission regulations in the area
and provide corresponding annual emission reductions to be realized
from each milestone in the schedule.\444\ In reviewing an attainment
plan under subpart 4, EPA evaluates whether the annual incremental
emission reductions to be achieved are reasonable in light of the
statutory objective of timely attainment. Although early implementation
of the most cost-effective control measures is often appropriate,
states should consider both cost-effectiveness and pollution reduction
effectiveness when developing implementation schedules for their
control measures and may implement measures that are more effective at
reducing PM2.5 earlier to provide greater public health
benefits.\445\
---------------------------------------------------------------------------

    \444\ Addendum at 42016.
    \445\ Id.
---------------------------------------------------------------------------

    Section 189(c) requires that attainment plans include quantitative
milestones in order to demonstrate RFP. The purpose of the quantitative
milestones is to allow periodic evaluation of the area's progress
towards attainment of the NAAQS through the RFP requirements. Thus, the
EPA determines 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 three years, when a
state demonstrates compliance with the quantitative milestone
requirement, it will demonstrate that RFP has been achieved during each
of the relevant three years. Quantitative milestones should provide an
objective means to evaluate progress toward attainment meaningfully,
e.g., through imposition of emission controls in the attainment plan
and the requirement to quantify those required emission reductions. The
CAA also requires milestone reports (due 90 days after each milestone),
and these reports should include calculations and any assumptions made
concerning how RFP

has been met, e.g., through quantification of emission reductions to
date.\446\
---------------------------------------------------------------------------

    \446\ Id. at 42016, 42017.
---------------------------------------------------------------------------

    The CAA does not specify the starting point for counting the three-
year periods for quantitative milestones under CAA section 189(c). In
the General Preamble and Addendum, EPA interpreted the CAA to require
that the starting point for the first three-year period be the due date
for the Moderate area plan submission.\447\ In keeping with this
historical approach, EPA is proposing to establish December 31, 2014 as
the starting point for the first 3-year period under CAA section 189(c)
for the 1997 PM2.5 standards in the SJV. This date was the
due date established in the EPA's June 2, 2014 Deadline and
Classification Rule for the State's submission of any additional
attainment-related SIP elements necessary to satisfy the subpart 4
Moderate area requirements for the 1997 PM2.5 standards in
the SJV area.\448\ December 31, 2017 and December 31, 2020 would then
be the milestone dates that the Serious Area plan must address, at
minimum. The EPA believes that establishing December 31, 2017 as the
first quantitative milestone date is an appropriate means for
implementing the requirements of subpart 4 prospectively.
---------------------------------------------------------------------------

    \447\ General Preamble at 13539, Addendum at 42016.
    \448\ 79 FR 31566 (June 2, 2014) (final rule establishing
subpart 4 moderate area classifications and deadline for related SIP
submissions) (``Classification and Deadline Rule''). Although the
Classification and Deadline Rule did not affect any action that EPA
had previously taken under CAA section 110(k) on a SIP for a
PM2.5 nonattainment area, EPA noted that states may need
to submit additional SIP elements to fully comply with the
applicable requirements of subpart 4, even for areas with previously
approved PM2.5 attainment plans, and that the deadline
for any such additional plan submissions was December 31, 2014. Id.
at 31569.
---------------------------------------------------------------------------

2. RFP Demonstration and Quantitative Milestones in the 2015
PM2.5 Plan
    The RFP demonstration and quantitative milestones appear in Chapter
6, section 6.3 (pp. 6-6 to 6-8) of the 2015 PM2.5 Plan.
Further discussion of the RFP demonstration, particularly with respect
to ammonia, and the establishment of dates, content, and a reporting
commitment for quantitative milestones, appears in CARB's Staff Report
(pp. 25-26). In addition, by letter dated December 15, 2015, CARB's
Executive Officer committed to submit a SIP revision to supplement the
quantitative milestone portion of the 2015 PM2.5 Plan by
December 31, 2016 (``QM Letter'').\449\
---------------------------------------------------------------------------

    \449\ Letter from R. Corey, Executive Officer, CARB to J.
Blumenfeld, Regional Administrator, U.S. EPA Region 9, December 15,
2015.
---------------------------------------------------------------------------

    The Plan estimates that emissions of direct PM2.5,
NOX, and SOX will decline from the 2012 base year
to 2020 and states that emissions of each of these pollutants will
remain below the levels needed to show ``generally linear progress''
from 2012 to 2020, the year that the Plan projects to be the earliest
practicable attainment date for the 1997 annual PM2.5
standard.\450\ The Plan's emissions inventory shows that direct
PM2.5, NOX, and SOX are emitted by a
large number and range of sources in the SJV and the emission
reductions needed for these pollutants are inventory wide.\451\ The
District followed the procedures in the 2007 PM2.5
Implementation Rule to calculate 2014 and 2017 RFP targets (or
``benchmark'' emission levels) for direct PM2.5,
NOX, and SOX and then concluded that projected
emission levels for each pollutant, based on its adopted control
strategy, would be below those targets in both milestone years.\452\
---------------------------------------------------------------------------

    \450\ 2015 PM2.5 Plan, Chapter 6, Table 6-8 (``RFP
Target Demonstration (2014 and 2017)''), p. 6-8.
    \451\ 2015 PM2.5 Plan, Appendix B.
    \452\ 2015 PM2.5 Plan, pp. 6-6 to 6-8.
---------------------------------------------------------------------------

    The BACM control strategy that provides the basis for these
emissions projections is described in Chapters 5 and 7 and Appendices C
and D of the Plan. For stationary and area sources, the Plan highlights
several rules that are projected to contribute to attainment of the
PM2.5 standards.\453\ For example, Rule 4354 (``Glass
Melting Furnaces'') controls emissions of NOX,
SOX, and PM from industrial glass manufacturing--the largest
source of SOX emissions in the San Joaquin Valley--and its
emissions projections are presented in Appendix C as part of the Plan's
BACM and MSM analysis.\454\ Similarly, Rule 4901 (``Wood Burning
Fireplaces and Wood Burning Heaters'') controls emissions from
residential wood burning and addresses the largest combustion source of
direct PM2.5.\455\ Measures to control dust sources of
direct PM2.5 are also presented in the Plan's BACM and MSM
analyses and reflected in the Plan's baseline emission projections.
Examples of such measures include Rule 4550 (``Conservation Management
Practices'') \456\ and Rule 8061 (``Paved and Unpaved Roads'').\457\
For mobile sources, the Plan lists numerous CARB regulations and
discusses the key regulations that limit the emission of direct
PM2.5 and NOX from on-road and non-road mobile
sources.\458\ For instance, the regulations that apply to the two
largest sources of NOX in the San Joaquin Valley--heavy,
heavy-duty diesel trucks and farm equipment--are discussed in Appendix
C and their emission projections are presented in the Plan's emissions
inventory.\459\
---------------------------------------------------------------------------

    \453\ 2015 PM2.5 Plan, Chapter 7, Section 7.1.1, pp.
7-2 to 7-6.
    \454\ 2015 PM2.5 Plan, Chapter 7, pp. 7-3 to 7-4 and
Appendix C, p. C-102.
    \455\ 2015 PM2.5 Plan, Chapter 7, p. 7-4 and Appendix
C, p. C-157.
    \456\ 2015 PM2.5 Plan, Appendix C, p. C-108.
    \457\ 2015 PM2.5 Plan, Appendix C, p. C-194.
    \458\ 2015 PM2.5 Plan, Chapter 7, Section 7.1.3, pp.
7-6 to 7-13.
    \459\ 2015 PM2.5 Plan, Appendix D, pp. D-8 to D-12
(for heavy heavy duty trucks) and D-15 (for farm equipment) and
Appendix B, p. B-7.
---------------------------------------------------------------------------

    With respect to ammonia, the 2015 PM2.5 Plan projects an
increase in annual average ammonia emissions from 329.5 tpd in 2012 to
358.0 tpd in 2020.\460\ The Plan states that both NOX and
ammonia participate in forming ammonium nitrate (i.e., secondary
PM2.5) but that NOX emission reductions are an
order of magnitude more effective at reducing ambient PM2.5
than ammonia reductions.\461\ Based on the relative insensitivity of
ambient PM2.5 levels to ammonia reductions compared to
NOX reductions, the Plan states that ammonia is not a
significant precursor to ambient PM2.5 in the SJV \462\ and
thus that an RFP demonstration for ammonia is not required.\463\ The
Plan also states that NOX emission levels are projected to
be well below the levels needed to show generally linear progress
toward attainment. The CARB Staff Report provides additional analysis
by converting the increase in ammonia emissions into ``NOX
equivalent'' emission levels (using a ``NOX equivalency''
calculation method) and demonstrating that the ``NOX
equivalent'' emissions level continues to show linear progress toward
attainment from 2012 to 2020.\464\
---------------------------------------------------------------------------

    \460\ 2015 PM2.5 Plan, Appendix B, p. B-19.
    \461\ Id. See also, 2015 PM2.5 Plan, Chapter 2, p. 2-
27, which concludes the District's analysis of the relationship
between ammonia emissions and ambient PM2.5 levels by
stating that ``ammonia reductions at the Bakersfield-California site
are only. . . 10% as effective as NOX reductions.''
    \462\ 2015 PM2.5 Plan, Chapter 2, section 2.6
(``Insignificant Precursors to PM2.5 Concentrations in
the Valley'').
    \463\ 2015 PM2.5 Plan, CARB Staff Report, p. 26.
    \464\ 2015 PM2.5 Plan, CARB Staff Report, pp. 25-26.
---------------------------------------------------------------------------

    The NOX equivalency method used in the Plan relies on
the sensitivity of ambient PM2.5 levels to decreases in
ammonia emissions compared to decreases in NOX emissions, as
modeled at the Bakersfield-California monitoring site. The Plan states
that in the San Joaquin Valley ammonia emission reductions are only 10%
as effective as NOX emission reductions, with a

relative sensitivity factor of 0.1.\465\ Stated alternatively, this is
a 1:10 NOX for ammonia trading ratio, i.e., it takes 1 tpd
of NOX emissions to match the ambient effect of 10 tpd of
ammonia in this area. The State calculates the change in ammonia
emissions from the base year (2012) to each RFP milestone year \466\
(2014 and 2017), and multiplies it by the trading ratio to calculate a
NOX increase equivalent to the ammonia increase, which the
State then adds to the NOX emissions inventory for each RFP
milestone year to calculate the total NOX decrease and
ammonia increase expressed as ``NOX equivalent'' emission
levels.\467\ The CARB Staff Report states that the total NOX
equivalent emissions levels are below the linear reductions in
NOX necessary to demonstrate RFP and, therefore, that the
RFP requirement is met, despite the projected increase in the ammonia
inventory.
---------------------------------------------------------------------------

    \465\ 2015 PM2.5 Plan, Chapter 2, p. 2-27. Note that
Bakersfield-California is projected to be the design value monitor
for the SJV in 2018 with respect to the 1997 24-hour
PM2.5 standard. 2015 PM2.5 Plan, Appendix F,
Table F-1 (``Projected 2018 and 2020 Design Values''), p. F-7.
    \466\ We use ``RFP milestone year'' to mean each year for which
the Plan provides an RFP analysis and related emissions projections.
    \467\ That is, (NOX emissions) 2017 +
[(NH3 emissions) 2017-(NH3
emissions) 2012] * 0.1 = (total NOX equivalent
emissions) 2017. Using values from the 2015
PM2.5 Plan, the 17.5 tpd increase in ammonia emissions
from 2012 to 2017 is equivalent to a 1.8 tpd increase in
NOX emissions, as follows: 235.7 + [347.0-329.5]*0.1 =
237.5 tpd. See CARB Staff Report, p. 26, Table 12.
---------------------------------------------------------------------------

    Control measures for ammonia sources are described in Appendix C of
the Plan. For example, ammonia controls resulting from Rule 4570
(``Confined Animal Facilities''), Rule 4565 (``Biosolids, Animal
Manure, and Poultry Litter Operations''), and Rule 4566 (``Organic
Material Composting'') are discussed at length in section C.41 of
Appendix C and their emission projections are presented collectively
under farming operations in the Plan's emissions inventory.\468\ We
discuss these control measures more fully in section V.D of this
preamble (``Best Available Control Measures and Most Stringent
Measures'') and in the EPA's SJV Rules TSD.
---------------------------------------------------------------------------

    \468\ 2015 PM2.5 Plan, Appendix C, Section C.41, pp.
C-240 to C-281 and Appendix B, p. B-17.
---------------------------------------------------------------------------

    With respect to quantitative milestones, the CARB Staff Report
states that the Plan identifies RFP emissions levels for direct
PM2.5, NOX, and SOX for 2014 and 2017
that show generally linear progress towards attaining the annual
standard in 2020, and that ``[t]hese emission levels for 2017 along
with the 2020 attainment emission levels serve as the quantitative
milestones required under the Act.'' \469\ CARB addresses the projected
increase in ammonia emissions over the planning period by evaluating
those emissions in light of the atmospheric response to NOX
and ammonia emissions in the San Joaquin Valley area and concluding
that ``the combined emission levels of NOX and ammonia that
are projected to occur through the 2020 attainment year provide for the
required generally linear air quality progress.'' \470\ The CARB Staff
Report also states California's commitment to provide letters to EPA
``reporting that the emission inventory milestones have been met and
the status of any emission reduction commitments,'' and to provide
these letters by March 31, 2018 for the 2017 milestone and by March 31,
2021 for the 2020 milestone.\471\
---------------------------------------------------------------------------

    \469\ 2015 PM2.5 Plan, CARB Staff Report, p. 26.
    \470\ Id.
---------------------------------------------------------------------------

    Additionally, the QM Letter contains the State's commitment to
submit, by December 31, 2016, a SIP revision that supplements the
quantitative milestone portion of the 2015 PM2.5 Plan by
identifying specific quantitative milestones to be achieved by the 2017
RFP milestone year and 2020 attainment year that demonstrate reasonable
further progress toward timely attainment of the PM2.5
NAAQS. The QM Letter states that this SIP revision will include the
following milestones to track implementation of control measures and
emissions levels at each milestone year: (1) A list of measures in the
Plan's BACM/BACT and MSM control strategy and key implementation
requirements through 2017 and 2020, including compliance milestones for
the State's Truck and Bus Rule and the District's residential wood
burning rule (Rule 4901), (2) compliance with the State's and
District's enforceable commitments in the Plan by the 2017 milestone
date, and (3) updated emissions inventories for both 2017 and
2020.\472\ The QM Letter also states that the SIP revision will
identify appropriate air quality quantitative milestones for 2017 and
2020 designed to evaluate air quality progress resulting from
implementation of the Plan's control strategy, including an assessment
of monitored ambient PM2.5 concentrations and other
variables affecting ambient PM2.5 concentrations in each of
those years.\473\
---------------------------------------------------------------------------

    \472\ QM Letter, pp. 1-2.
    \473\ Id., p. 2.
---------------------------------------------------------------------------

3. Evaluation and Proposed Actions
Reasonable Further Progress Demonstration
    With respect to direct PM2.5, NOX, and
SO2, we agree that ``generally linear progress'' is an
appropriate measure of RFP for the 1997 PM2.5 NAAQS in the
SJV area given that, as the Plan documents, direct PM2.5,
NOX, and SOX are emitted by a large number and
range of sources in the SJV, the emission reductions needed for these
pollutants are inventory wide,\474\ and secondary particulates
contribute significantly to ambient PM2.5 levels in the SJV
area.\475\
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    \474\ 2015 PM2.5 Plan, Appendix B.
    \475\ 2015 PM2.5 Plan, Chapter 5, Section 5.4.1
(``Significance Determination Approach'').
---------------------------------------------------------------------------

    The 2015 PM2.5 Plan documents the State's conclusion
that all BACM, BACT, and MSM for these pollutants are being implemented
as expeditiously as practicable and identifies projected levels of
direct PM2.5, NOX, and SOX emissions
in 2014 and 2017 that reflect full implementation of the State's and
District's BACM/BACT and MSM control strategy for these
pollutants.\476\ For example, Rule 4550 (``Conservation Management
Practices'') was adopted in 2004 and its requirements to control
PM10 emissions (including PM2.5) from on-field
crop and animal feeding operations are fully implemented.\477\ These
operations represent the largest dust sources of direct
PM2.5 in the San Joaquin Valley.\478\ More recently,
SJVUAPCD revised Rule 4901 (``Wood Burning Fireplaces and Wood Burning
Heaters'') in September 2014 by strengthening the District's
curtailment program for residential wood burning, thereby further
limiting emissions from San Joaquin Valley's largest combustion source
of direct PM2.5.\479\ These rule amendments provide part of
the incremental emission reductions of direct PM2.5 from the
2014 to 2017 RFP milestone years and through the 2018 and 2020
attainment years.\480\
---------------------------------------------------------------------------

    \476\ 2015 PM2.5 Plan, Chapter 6, Section 6.3, and
Appendix B. See also our discussion of BACM/BACT in section V.D of
this proposed rule.
    \477\ 2015 PM2.5 Plan, Appendix C, pp. C-106 to C-
107.
    \478\ 2015 PM2.5 Plan, Chapter 5, Table 5-2, pp. 5-7
to 5-8. See also 2015 PM2.5 Plan, Appendix B, p. B-2,
    \479\ 2015 PM2.5 Plan, Chapter 7, p. 7-4 and Appendix
C, p. C-156. See also 2015 PM2.5 Plan, Appendix B, p. B-
2.
    \480\ 2015 PM2.5 Plan, CARB Staff Report, p. 9.

---------------------------------------------------------------------------

    The Truck and Bus Regulation and Drayage Truck Regulation became
effective in 2011 and have rolling compliance deadlines based on truck
engine model year. These and other regulations applicable to heavy duty
diesel trucks will continue to reduce emissions of diesel particulate
matter and NOX through the RFP and attainment planning
years.\481\ For instance, model year 1994 and 1995 heavy heavy duty
diesel truck engines must be upgraded to meet the 2010 model year truck
engine emission standards by 2016, and model year 1996-1999 engines
must by upgraded by January 1, 2020.\482\ The emission reductions from
these rules represent the largest portion of the NOX
emission reductions upon which the Plan's attainment and RFP
demonstrations rely.\483\ With respect to SOX emissions,
Rule 4354 (``Glass Melting Furnaces'') was amended in May 2011,
establishing SOX emission limits with compliance deadlines
through January 1, 2014.\484\ This rule will achieve emission
reductions through the 2017 RFP milestone year and 2018 and 2020
attainment years. As explained in section V.D of this preamble, we are
proposing to find that the State and District are implementing these
BACM, BACT and MSM provisions for the 1997 PM2.5 NAAQS as
expeditiously as practicable.
---------------------------------------------------------------------------

    \481\ 2015 PM2.5 Plan, Chapter 7, p. 7-9 to 7-10 and
Appendix D, pp. D-8 to D-11.
    \482\ Title 13, California Code of Regulations, Section 2025
(``Regulation to Reduce Emissions of Diesel Particulate Matter,
Oxides of Nitrogen and Other Criteria Pollutants, from In-Use Heavy-
Duty Diesel-Fueled Vehicles''), paragraphs (e), (f), and (g),
effective December 14, 2011. See also EPA's final rule approving
CARB's Truck and Bus Rule. 77 FR 20308 at 20309-20310 (April 4,
2012).
    \483\ 2015 PM2.5 Plan, Appendix B, p. B-7.
    \484\ 2015 PM2.5 Plan, Chapter 7, pp, 7-3 to 7-4.
---------------------------------------------------------------------------

    Additionally, the method used to calculate RFP target (or
``benchmark'') emission levels for direct PM2.5,
NOX, and SO2 is generally consistent with the
method provided in the 2007 PM2.5 Implementation Rule (40
CFR 51.1009(f)). We note that the 2015 PM2.5 Plan calculates
the 2014 and 2017 RFP benchmark emission levels using 2020 attainment
emissions levels that are not consistent with the attainment targets
presented in CARB's Staff Report.\485\ We have, however, re-calculated
the RFP benchmark emissions levels for these years using the attainment
targets found in the CARB Staff Report,\486\ as shown in Table 10
below. The EPA's calculations indicate that the Plan's projected 2014
and 2017 emission levels for direct PM2.5, NOX,
and SOX are below the RFP benchmark emission levels for
these years.\487\
---------------------------------------------------------------------------

    \485\ 2015 PM2.5 Plan, Chapter 6, Table 6-6, p. 6-7
vs. CARB Staff Report, p. 9.
    \486\ 2015 PM2.5 Plan, CARB Staff Report, Table 1, p.
9.
    \487\ For example, the 2017 RFP benchmark for direct
PM2.5 should account for five years' worth of annual
incremental reductions and is calculated as (2012 emission
inventory)-(annual increment reduction)*5 = 66.0 tpd-(0.65 tpd/yr)*5
= 62.75 tpd. The projected emissions inventory for direct
PM2.5 in 2017 is 62.5 tpd, which is less than this RFP
benchmark.

                                             Table 10--EPA Calculation of 2015 PM2.5 Plan RFP Demonstration
                                                             [tpd, based on annual averages]
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                               2012            2020           Annual                           2014                            2017
                                             Emissions      Attainment      incremental      2014 RFP        Projected       2017 RFP        Projected
                                           inventory \a\     target b      reduction \c\     Benchmark     emissions \d\     Benchmark     emissions \d\
--------------------------------------------------------------------------------------------------------------------------------------------------------
Direct PM2.5............................            66.0            60.8            0.65            64.7            63.3           62.75            62.5
NOX.....................................           332.2           206.5           15.71          300.78           284.2          253.63           235.7
SOX.....................................             8.1             7.8            0.04            8.03             7.4            7.91             7.6
--------------------------------------------------------------------------------------------------------------------------------------------------------
\a\ 2015 PM2.5 Plan, Chapter 6, Table 6-6, p. 6-7.
\b\ 2015 PM2.5 Plan, CARB Staff Report, Table 1, p. 9.
\c\ Annual incremental reduction = (2012 emissions inventory-2020 attainment target)/(2020-2012).
\d\ 2015 PM2.5 Plan, Chapter 6, Table 6-8, p. 6-8.

    With respect to ammonia, the 2015 PM2.5 Plan shows an
8.6% increase in total ammonia emissions during the 2012 to 2020
period.\488\ Unlike the wide range of sources emitting direct
PM2.5, NOX, and SO2 in the Valley,
emissions of ammonia are almost entirely from three source categories:
confined animal facilities (CAFs), fertilizer application, and
composting, with more than half of all emissions coming from CAFs.\489\
Collectively, these three categories emit 95% of all ammonia emissions
in the 2012 annual average base year inventory.\490\
---------------------------------------------------------------------------

    \488\ 2015 PM2.5 Plan, Appendix B, Table B-5.
    \489\ In the inventories provided in Appendix B of the Plan,
emissions from these sources are found in the categories ``Farming
Operations'', ``Pesticides/Fertilizers'', and ``Other (Waste
Disposal)'', respectively.
    \490\ 2015 PM2.5 Plan, Appendix B, Table B-5
(``Ammonia''), pp. B-16 to B-19. The three categories comprising
this 95% of emissions in the ammonia emission inventory are Other
(Waste Disposal), Pesticides/Fertilizers, and Farming Operations.
---------------------------------------------------------------------------

    Several District measures already in the SIP for the SJV area
control ammonia emissions from two of these source categories. District
Rule 4570 (``Confined Animal Facilities'') required implementation of
control measures to reduce VOCs in 2008 and required full compliance by
affected sources by mid-2012.\491\ Many of the VOC control measures
have an ammonia co-benefit, and the District estimates a 100 tpd
reduction in ammonia from this rule, which have been accounted for in
the emissions inventory of the 2015 PM2.5 Plan.\492\ The
Plan also indicates that implementation of District Rule 4565
(``Biosolids, Animal Manure, and Poultry Litter Operations''), adopted
March 15, 2007,\493\ and Rule 4566 (``Organic Material Composting
Operations''), adopted August 18, 2011,\494\ resulted in some ammonia
reductions, but these reductions are not reflected in the base year or
baseline inventories. As discussed in section V.D of this proposed
rule, we are proposing to determine that each of these measures
implements BACM and MSM for the control of ammonia as a precursor to
PM2.5 in the San Joaquin Valley for purposes of the 1997
PM2.5 NAAQS.
---------------------------------------------------------------------------

    \491\ 2015 PM2.5 Plan, Appendix C, pp. C-240 to C-
243.
    \492\ 2015 PM2.5 Plan, Appendix C, pp. C-240 to C-
241. See also, Memo to file, ``Call with California Air Resources
Board regarding VOC and ammonia emissions inventory,'' R. Mays, EPA
Region 9, September 30, 2015.
    \493\ 2015 PM2.5 Plan, Appendix C, pp. C-276.
    \494\ 2015 PM2.5 Plan, Appendix C, pp. C-272 to C-
273.
---------------------------------------------------------------------------

    The statement in the Plan that ammonia is an insignificant
precursor in the SJV area is based on the State's analysis of the
relative sensitivity of ambient PM2.5 levels to changes in
ammonia emissions as compared to NOX emissions. The State
relies in part on information previously presented in

the 2012 PM2.5 Plan for the 2006 24-hour PM2.5
standard to justify a NOX for ammonia trading ratio of 0.1.
The 2012 PM2.5 Plan contains modeling results and states
that ``reductions in ammonia are approximately nine times less
effective than NOX.'' \495\ The 2012 PM2.5 Plan
also gives ammonia and NOX sensitivities (ambient
PM2.5 changes in [mu]g/m\3\ per tpd of emission reductions),
based on modeling of the ambient effect of a 25% area-wide reduction in
each pollutant.\496\ The ratios of these sensitivities give an ammonia-
NOX relative sensitivity ratio, or NOX for
ammonia trading ratio, of 0.10 for the Bakersfield-California site, and
0.11 (about 1/9) for the Bakersfield-Planz site.\497\
---------------------------------------------------------------------------

    \495\ 2012 PM2.5 Plan, Appendix G (``Weight of
Evidence Analysis''), p. 64.
    \496\ 2012 PM2.5 Plan, Appendix G, Table 7, p. 65.
    \497\ The difference between these two figures is about 0.1%
when carried through in the calculation of the NOX
equivalent of ammonia.
---------------------------------------------------------------------------

    The 2015 PM2.5 Plan similarly reflects the State's
conclusion that ammonia emission reductions are about 10% as effective
as NOX reductions in decreasing ambient PM2.5
concentrations.\498\ We have reviewed the modeling analysis from which
the State and District derived the 0.1 NOX for ammonia
trading ratio and propose to find that this ratio is a reasonable
estimate of the sensitivity of ambient PM2.5 to ammonia
reductions relative to NOX reductions, at least for the
Bakersfield-California and Bakersfield-Planz monitoring sites for which
the analysis was performed. For further discussion of our evaluation of
this trading ratio for purposes of the Plan's RFP demonstration, see
section IV.A of the EPA's Interpollutant Trading Ratios TSD.
---------------------------------------------------------------------------

    \498\ 2015 PM2.5 Plan, Chapter 2, pp. 2-27 (stating
that ``ammonia reductions at the Bakersfield-California site are . .
. only 10% as effective as NOX reductions''); see also
CARB Staff Report, p. 26 and Table 12 (expressing NOX and
ammonia emissions combined as ``NOX equivalent'' emission
levels).
---------------------------------------------------------------------------

    The Bakersfield-California site is projected to be the design value
site for the 1997 24-hour PM2.5 standard in 2018,\499\ which
addresses the requirement of 40 CFR 51.1009(h) that an equivalent
method for demonstrating RFP must do so at the design value monitoring
site within the nonattainment area. As discussed in section V.E.5 of
this proposed rule, although the State had initially projected the
Madera site to be the design value site for the 1997 annual
PM2.5 standard in 2020, based on weight of evidence, it now
appears the Bakersfield-Planz site will most likely be the design value
site for the annual PM2.5 standard in 2020. Either way, the
0.1 ammonia-NOX relative sensitivity factor is adequate for
the RFP demonstration because it is derived from modeling analyses that
account for emission projections at both of these Bakersfield
monitoring sites.
---------------------------------------------------------------------------

    \499\ 2015 PM2.5 Plan, Appendix F, Table F-1
(``Projected 2018 and 2020 Design Values''), p. F-7.
---------------------------------------------------------------------------

    Taking the ammonia emissions increases into account, the
NOX equivalent emission levels presented in the Plan \500\
for the 2014 and 2017 RFP milestone years fall below the benchmark RFP
NOX emissions levels for those same years.\501\ In essence,
the substantial reduction of NOX emissions that is projected
to result from the Plan's control strategy (i.e., 37.8% reduction) from
2012 to 2020 \502\ appears to more than offset the increase in ammonia
emissions (i.e., 8.6% increase) that is projected to occur during that
same period.\503\ More specifically, as shown in Table 11, taking into
account the increase in ammonia emissions during the 2012 to 2020
period, the NOX equivalent emission levels projected in the
Plan for the 2014 and 2017 RFP milestone years are 5-6% lower than the
levels representing generally linear NOX emission reductions
for those same years, thus showing NOX emission reductions
at a rate faster than the benchmark scenario.
---------------------------------------------------------------------------

    \500\ 2015 PM2.5 Plan, CARB Staff Report, p. 26.
    \501\ This approach is consistent with the regulatory option of
40 CFR 51.1009(g)(2) that the RFP plan demonstrate emission levels
that are ``projected to result in a generally equivalent improvement
in air quality by the milestone year as would be achieved under the
benchmark RFP plan.''
    \502\ 2015 PM2.5 Plan, Appendix B, Table B-2, p. B-8
and CARB Staff Report, p. 9. Emissions of NOX are project
to decrease from 332.2 tpd in 2012 to 206.5 tpd in 2020 (i.e., a
decrease of 125.7 tpd or 37.8%).
    \503\ 2015 PM2.5 Plan, Appendix B, Table B-5, p. B-
19. Emissions of ammonia are project to increase 329.5 tpd in 2012
to 358.0 tpd in 2020 (i.e., an increase of 28.5 tpd or 8.6%).

 Table 11--Comparison of NOX Equivalent Emissions to RFP Linear Emissions Level for NOX for RFP Milestone Years
                                               [tpd, except row G]
----------------------------------------------------------------------------------------------------------------
                                                                               2012         2014         2017
----------------------------------------------------------------------------------------------------------------
A.........................................  NOX Emissions................        332.2        284.2        235.7
B.........................................  Ammonia Emissions............        329.5        336.2        347.0
C.........................................  NOX equivalent of ammonia      ...........          0.7          1.8
                                             increase.
D.........................................  Total NOX Equivalent           ...........        284.9        237.5
                                             Emissions (A+C).
E.........................................  RFP Linear Level for NOX.....  ...........        300.9        253.9
F.........................................  Total NOX Equivalent Emission  ...........         16.0         16.4
                                             Reductions Beyond RFP Linear
                                             Level (E-D).
G.........................................  % Below RFP Linear Level (F/   ...........         5.3%         6.5%
                                             E).
----------------------------------------------------------------------------------------------------------------
Source: 2015 PM2.5 Plan, CARB Staff Report, Table 12, p. 26.

    As discussed in section V.C of this proposed rule, we are proposing
to determine that VOCs do not contribute significantly to ambient
PM2.5 levels that exceed the 1997 PM2.5 standards
in the SJV and, accordingly, that no RFP demonstration for VOCs is
necessary for purposes of the 1997 PM2.5 standards in this
area.
    In sum, the 2015 PM2.5 Plan demonstrates that emissions
of direct PM2.5, NOX and SOX will be
reduced at rates representing generally linear progress toward
attainment, and that the increase in ammonia emissions over the 2012-
2020 planning period will be more than offset by substantial
NOX emission reductions exceeding the amounts necessary to
show generally linear progress toward attainment. The Plan also
demonstrates that all BACM, BACT and MSM that provide the bases for the
direct PM2.5, NOX, SOX, and ammonia
emissions projections in the RFP analysis in the Plan are being
implemented as expeditiously as practicable. Accordingly, we propose to
determine that the Plan requires the annual incremental reductions in
emissions of direct PM2.5 and relevant PM2.5
precursors that are necessary for the purpose of ensuring attainment of
the 1997 24-hour and annual PM2.5

standards by 2018 and 2020, respectively, in accordance with the
requirements of CAA sections 171(1) and 172(c)(2).
Quantitative Milestones
    Although the RFP emission levels identified in the Plan for the
2017 and 2020 milestone years represent generally linear progress
toward attainment by 2018 and 2020, the Plan as originally submitted in
June 2015 does not identify an objective means for evaluating the
area's compliance with these emission targets or progress toward
attainment, other than through 2017 and 2020 emissions levels and
CARB's commitment to report on the ``status of any emission reduction
commitments'' in the Plan. We note that the Plan contains only one
emission reduction commitment: To adopt amendments to District Rule
4692 (``Commercial Charbroiling'') in 2016 and to achieve 0.4 tpd of
direct PM2.5 emission reductions through implementation of
this amended rule or a substitute rule achieving equivalent emission
reductions.\504\ Such a milestone would not provide an adequate means
to evaluate progress toward attainment of the PM2.5 NAAQS in
the SJV, consistent with RFP requirements.
---------------------------------------------------------------------------

    \504\ 2015 PM2.5 Plan, Chapter 7, p. 7-6, and
SJVUAPCD Governing Board Resolution 15-4-7A, paragraph 7.
---------------------------------------------------------------------------

    In the QM Letter, however, CARB committed to adopt and submit, no
later than December 31, 2016, a revision to the 2015 PM2.5
Plan that identifies specific milestones demonstrating progress toward
attainment of the 24-hour PM2.5 standard by December 31,
2018 and the annual PM2.5 standard by December 31, 2020. The
QM Letter describes the specific components of this SIP revision that
CARB will adopt and submit by December 31, 2016, including milestones
to track implementation of specific SIP control measures and
commitments, and air quality milestones to be achieved by the 2017 RFP
milestone year and 2020 attainment year. Two of the control measures
identified in the QM Letter are responsible for a significant portion
of the NOX and direct PM2.5 emission reductions
necessary for RFP and attainment: CARB's Truck and Bus Rule and the
District's residential wood burning rule (Rule 4901). Emissions from
heavy heavy duty trucks and residential wood burning are the largest
combustion sources of NOX and direct PM2.5 in San
Joaquin Valley, and the Truck and Bus Rule and Rule 4901 achieve the
largest amounts of NOX and direct PM2.5 emission
reductions, respectively, identified in the Plan's attainment
demonstration.\505\ The District's commitment in the Plan to amend Rule
4692 (``Commercial Charbroiling'') in 2016 and to achieve 0.4 tpd of
direct PM2.5 emission reductions through implementation of
this amended rule or a substitute rule achieving equivalent emission
reductions \506\ also accounts for a portion of the direct
PM2.5 emission reductions necessary for RFP and attainment
in the Plan.\507\ These implementation milestones, together with the
updated emission inventories and air quality milestones for 2017 and
2020 that the State has also committed to identify as quantitative
milestones in the SIP revision, would provide an objective means to
evaluate the area's progress in achieving not only the incremental
emissions reductions but also the incremental air quality improvements
necessary to attain the 24-hour and annual PM2.5 NAAQS by
2018 and 2020, respectively.
---------------------------------------------------------------------------

    \505\ For stationary and area sources, ``Residential Fuel
Combustion'' is the largest combustion source of direct
PM2.5 in San Joaquin Valley (e.g., 9.4 tpd of the total
2012 winter average emissions of 61.0 tpd) and CARB's Staff Report
identifies Rule 4901 as achieving the largest portion of the direct
PM2.5 emission reductions for attaining 1997
PM2.5 NAAQS (e.g., 2.9 tpd of the Plan's 6.6 tpd total
winter average emission reductions from 2012 to 2018). 2015
PM2.5 Plan, Appendix B, p. B-2 and CARB Staff Report, p.
9. For all sources, ``Heavy Heavy Duty Diesel Trucks (HHDV)'' are
the largest source of NOX in the San Joaquin Valley
(e.g., 120.5 tpd of the total 2012 annual average emissions of 332.2
tpd) and the Plan estimates that the largest emission reductions of
NOX during the attainment planning period, for which the
Truck and Bus Rule is a significant driver, will result from this
source category (e.g., 59.2 tpd of the 125.7 tpd annual average
emission reductions from 2012 to 2020). 2015 PM2.5 Plan,
Appendix B, p. B-7 and CARB Staff Report, p. 9.
    \506\ 2015 PM2.5 Plan, Chapter 7, p. 7-6, and
SJVUAPCD Governing Board Resolution 15-4-7A, paragraph 7.
    \507\ The Plan estimates that the amendments to Rule 4692 will
achieve 0.4 tpd of the Plan's 5.2 tpd total annual average emission
reductions of direct PM2.5 from 2012 to 2020. 2015
PM2.5 Plan, CARB Staff Report, p. 9.
---------------------------------------------------------------------------

    Under section 110(k)(4) of the Act, EPA may conditionally approve a
plan revision based on a commitment by the State to adopt specific
enforceable measures by a date certain but not later than 1 year after
the date of the plan approval. Based on CARB's commitments to submit
the specific SIP revisions identified in the QM Letter by December 31,