Document ID: EPA-R09-OAR-2017-0490-0003
Agency: epa
Document Type: Proposed Rule
Title: Air Quality State Implementation Plans; Approvals and Promulgations: California; South Coast  Serious Area Plan for the 2006 Fine Particulate Matter National Ambient Air Quality Standards
Posted Date: 2018-10-03T04:00Z

[Federal Register Volume 83, Number 192 (Wednesday, October 3, 2018)]
[Proposed Rules]
[Pages 49872-49894]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2018-21560]

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ENVIRONMENTAL PROTECTION AGENCY

40 CFR Part 52

[EPA-R09-OAR-2017-0490; FRL-9984-91--Region 9]

Approval and Promulgation of Implementation Plans; California; 
South Coast Serious Area Plan for the 2006 PM2.5 NAAQS

AGENCY: U.S. Environmental Protection Agency (EPA).

ACTION: Proposed rule.

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SUMMARY: The Environmental Protection Agency (EPA) is proposing to 
approve state implementation plan (SIP) revisions submitted by 
California to address Clean Air Act (CAA or ``Act'') requirements for 
the 2006 24-hour fine particulate matter (PM2.5) national 
ambient air quality standards (NAAQS or ``standards'') in the Los 
Angeles-South Coast air basin (South Coast) Serious PM2.5 
nonattainment area. The EPA is also proposing to approve 2017 and 2019 
motor vehicle emissions budgets for transportation conformity purposes 
and inter-pollutant trading ratios for use in transportation conformity 
analyses.

DATES: Any comments must arrive by November 2, 2018.

ADDRESSES: Submit your comments, identified by Docket ID No. EPA-R09-
OAR-2017-0490 at https://www.regulations.gov, or via email to 
[email protected]. For comments submitted at Regulations.gov, follow 
the online instructions for submitting comments. Once submitted, 
comments cannot be edited or removed from Regulations.gov. For either 
manner of submission, the EPA may publish any comment received to its 
public docket. Do not submit electronically any information you 
consider to be Confidential Business Information (CBI) or other 
information whose disclosure is restricted by statute. Multimedia 
submissions (audio, video, etc.) must be accompanied by a written 
comment. The written comment is considered the official comment and 
should include discussion of all points you wish to make. The EPA will 
generally not consider comments or comment contents located outside of 
the primary submission (i.e., on the web, cloud, or other file sharing 
system). For additional submission methods, please contact the person 
identified in the FOR FURTHER INFORMATION CONTACT section. For the full 
EPA public comment policy, information about CBI or multimedia 
submissions, and general guidance on making effective comments, please 
visit http://www2.epa.gov/dockets/commenting-epa-dockets.

FOR FURTHER INFORMATION CONTACT: Wienke Tax, Air Planning Office (AIR-
2), EPA Region IX, (415) 947-4192, [email protected].

SUPPLEMENTARY INFORMATION: Throughout this document, ``we,'' ``us'' and 
``our'' refer to the EPA.

Table of Contents

I. Background
II. Summary of the 2016 PM2.5 Plan
III. Completeness Review of the 2016 PM2.5 Plan
IV. Clean Air Act Requirements for PM2.5 Serious Area 
Plans
V. Review of South Coast Serious Area Plan Addressing the 2006 
PM2.5 NAAQS
    A. Emissions Inventory
    B. PM2.5 Precursors
    C. Best Available Control Measures
    D. Attainment Demonstration and Modeling
    E. Reasonable Further Progress and Quantitative Milestones
    F. Contingency Measures
    G. Major Stationary Source Control Requirements Under CAA 
Section 189(e)
    H. Motor Vehicle Emission Budgets
VI. Summary of Proposed Actions and Request for Public Comment
VII. Statutory and Executive Order Reviews

I. Background

    On October 17, 2006, the EPA revised the 24-hour NAAQS for 
PM2.5, particulate matter with a diameter of 2.5 microns or 
less, to provide increased protection of public health by lowering the 
level from 65 micrograms per cubic meter ([micro]g/m\3\) to 35 
[micro]g/m\3\.\1\ Epidemiological studies have shown statistically 
significant correlations between elevated PM2.5 levels and 
premature mortality. Other important health effects associated with 
PM2.5 exposure include aggravation of respiratory and 
cardiovascular disease (as indicated by increased hospital admissions, 
emergency room visits, absences from school or work, and

[[Page 49873]]

restricted activity days), changes in lung function and increased 
respiratory symptoms. Individuals particularly sensitive to 
PM2.5 exposure include older adults, people with heart and 
lung disease, and children.\2\ PM2.5 can be emitted directly 
into the atmosphere as a solid or liquid particle (``primary 
PM2.5'' or ``direct PM2.5'') or can be formed in 
the atmosphere as a result of various chemical reactions among 
precursor pollutants such as nitrogen oxides, sulfur oxides, volatile 
organic compounds, and ammonia (``secondary PM2.5'').\3\
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    \1\ 40 CFR 50.13 and 71 FR 61144 (October 17, 2006). The EPA 
first established NAAQS for PM2.5 on July 18, 1997 (62 FR 
38652), including annual standards of 15.0 [micro]g/m\3\ based on a 
3-year average of annual mean PM2.5 concentrations and 
24-hour (daily) standards of 65 [micro]g/m\3\ based on a 3-year 
average of 98th percentile 24-hour concentrations (40 CFR 50.7). In 
2012, the EPA revised the annual standards to lower them to 12 
[micro]g/m\3\ (78 FR 3086, January 15, 2013, codified at 40 CFR 
50.18). Unless otherwise noted, all references to the 
PM2.5 standards in this notice are to the 2006 24-hour 
NAAQS of 35 [micro]g/m\3\ codified at 40 CFR 50.13.
    \2\ 78 FR 3086 at 3088 (January 15, 2013).
    \3\ 72 FR 20586, 20589 (April 25, 2007).
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    Following promulgation of a new or revised NAAQS, the EPA is 
required by CAA section 107(d) to designate areas throughout the nation 
as attaining or not attaining the NAAQS. On November 13, 2009, the EPA 
designated the South Coast as nonattainment for the 2006 24-hour 
PM2.5 standards.\4\ This designation became effective on 
December 14, 2009.\5\ The South Coast area is also designated 
nonattainment for the 1997 annual and 24-hour PM2.5 
standards.\6\ On June 2, 2014, the EPA classified the South Coast area 
as ``Moderate'' nonattainment for both the 1997 PM2.5 
standards and the 2006 PM2.5 standards under subpart 4 of 
part D, title I of the Act.7 8 California submitted a plan 
addressing the Moderate area attainment planning requirements for the 
2006 PM2.5 NAAQS in the South Coast on February 13, 2013, 
and submitted a supplement to this plan on March 4, 2015.\9\
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    \4\ 74 FR 58688 (November 13, 2009).
    \5\ 40 CFR 81.305.
    \6\ 70 FR 944 (January 5, 2005) and 40 CFR 81.305. In November 
2007, California submitted the 2007 PM2.5 Plan to provide 
for attainment of the 1997 PM2.5 standards in the South 
Coast. In November 2011, the EPA approved all but the contingency 
measures in the 2007 PM2.5 Plan (76 FR 69928, November 9, 
2011). In November 2011 and April 2013, the State submitted a 
revised contingency measure plan, which the EPA approved on October 
29, 2013 (78 FR 64402).
    \7\ 79 FR 31566.
    \8\ The EPA took this action in response to a decision of the 
Court of Appeals for the D.C. Circuit finding that the EPA had erred 
in implementing the PM2.5 NAAQS pursuant solely to the 
general implementation provisions of subpart 1 of Part D, Title I of 
the Act, without also considering the particulate matter-specific 
provisions of subpart 4 of Part D. Natural Resources Defense Council 
(NRDC) v. EPA, 706 F.3d 428 (D.C. Cir. 2013).
    \9\ Letter from James N. Goldstene, Executive Officer, 
California Air Resources Board (CARB), to Jared Blumenfeld, Regional 
Administrator, EPA Region IX, with attachments (transmitting 2012 
PM2.5 Plan), February 13, 2013, and letter from Richard 
W. Corey, Executive Officer, CARB, to Jared Blumenfeld, Regional 
Administrator, EPA Region IX, with attachments (transmitting 2015 
supplement to 2012 PM2.5 Plan), March 4, 2015.
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    On January 13, 2016, the EPA published a December 22, 2015 final 
rule reclassifying the South Coast area as ``Serious'' nonattainment 
under subpart 4, based on the EPA's determination that the area could 
not practicably attain the 2006 PM2.5 standards by the 
December 31, 2015 attainment date.\10\ This reclassification became 
effective on February 12, 2016. The reclassification was based upon the 
EPA's evaluation of ambient air quality data from the 2013-2015 period, 
indicating that it was not practicable for certain monitoring sites 
within the South Coast area to show PM2.5 design values at 
or below the level of the 2006 PM2.5 NAAQS by December 31, 
2015.\11\ On April 14, 2016, we partially approved and partially 
disapproved California's Moderate area plan for the 2006 
PM2.5 NAAQS in the South Coast.\12\ On February 12, 2018, we 
determined that California had corrected the deficiencies identified in 
our prior partial disapproval of this plan and terminated all sanction 
clocks triggered by that action.\13\
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    \10\ 81 FR 1514 (January 13, 2016).
    \11\ Id. at 1514; see also proposed rule, 80 FR 63640 (October 
20, 2015). Air quality data for 2013-2015 indicated that the highest 
monitors in the South Coast area had a design value of 38 [micro]g/
m\3\ for the 24-hour standard.
    \12\ 81 FR 22025 (April 14, 2016).
    \13\ 83 FR 5923 (February 12, 2018).
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    The South Coast PM2.5 nonattainment area is home to 
about 17 million people, has a diverse economic base, and contains one 
of the highest-volume port areas in the world. For a precise 
description of the geographic boundaries of the South Coast 
PM2.5 nonattainment area, see 40 CFR 81.305. The local air 
district with primary responsibility for developing a plan to attain 
the 2006 PM2.5 NAAQS in this area is the South Coast Air 
Quality Management District (``District'' or SCAQMD). The District 
works cooperatively with the California Air Resources Board (CARB) in 
preparing these plans. Authority for regulating sources in the South 
Coast is split between the District, which has responsibility for 
regulating stationary and most area sources, and CARB, which has 
responsibility for regulating most mobile sources and some categories 
of consumer products.
    As a consequence of its reclassification as a Serious 
PM2.5 nonattainment area, the South Coast area became 
subject to a new attainment date under CAA section 188(c)(2) and the 
requirement to submit a Serious area plan that satisfies the 
requirements of part D of title I of the Act, including the 
requirements of subpart 4, for the 2006 PM2.5 NAAQS.\14\ 
Under subpart 4, the attainment date for an area classified as Serious 
is as expeditiously as practicable, but no later than the end of the 
tenth calendar year following designation. As explained in the EPA's 
final reclassification action, the Serious area plan for the South 
Coast must include provisions to assure that the best available control 
measures (BACM) for the control of direct PM2.5 and 
PM2.5 precursors shall be implemented no later than 4 years 
after the area is reclassified (CAA section 189(b)(1)(B)), and a 
demonstration (including air quality modeling) that the plan provides 
for attainment as expeditiously as practicable but no later than 
December 31, 2019, which is the latest permissible attainment date 
under CAA section 188(c)(2).\15\
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    \14\ 81 FR 1514, 1518 (January 13, 2016).
    \15\ Id.
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    Given the December 31, 2019 outermost attainment deadline for the 
South Coast area under section 188(c)(2), the EPA required the State to 
adopt and submit a Serious area plan for the South Coast within 18 
months of the reclassification, well before the statutory SIP 
submission deadlines in CAA section 189(b)(2).\16\
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    \16\ Id.
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II. Summary of the 2016 PM2.5 Plan

    We are proposing action on portions of two California SIP 
submissions that address the 2006 24-hour PM2.5 NAAQS 
Serious area plan requirements in the South Coast. The first submission 
is the ``Final 2016 Air Quality Management Plan (March 2017),'' adopted 
by the SCAQMD Governing Board on March 3, 2017 (``2016 AQMP''). CARB 
submitted the 2016 AQMP to the EPA on April 27, 2017.\17\ The second 
submission, also submitted to the EPA on April 27, 2017, is CARB's 
``2016 State Strategy for the State Implementation Plan (March 2017)'' 
(``2016 State Strategy'').\18\ We refer to these SIP submissions 
collectively as the ``2016 PM2.5 Plan'' or ``Plan.''
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    \17\ Letter from Richard Corey, Executive Officer, CARB, to 
Alexis Strauss, Acting Regional Administrator, EPA Region IX, with 
enclosures, April 27, 2017.
    \18\ Id.
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    The 2016 AQMP is organized into eleven chapters, each addressing a 
specific topic. We summarize below each of the chapters relevant to the 
2006 PM2.5 NAAQS.\19\ Chapter 1,

[[Page 49874]]

``Introduction,'' introduces the 2016 AQMP, including its purpose, 
historical air quality progress in the South Coast, and the District's 
approach to air quality planning. Chapter 2, ``Air Quality and Health 
Effects,'' discusses current air quality in comparison with federal 
health-based air pollution standards. Chapter 3, ``Base Year and Future 
Emissions,'' summarizes emissions inventories, estimates current 
emissions by source and pollutant, and projects future emissions with 
and without growth. Chapter 4, ``Control Strategy and Implementation,'' 
presents the control strategy, specific measures, and implementation 
schedules to attain the air quality standards by the specified 
attainment dates. Chapter 5, ``Future Air Quality,'' describes the 
modeling approach used in the 2016 AQMP and summarizes the South 
Coast's future air quality projections with and without the control 
strategy. Chapter 6, ``Federal and State Clean Air Act Requirements,'' 
discusses specific federal and State requirements as they pertain to 
the South Coast, including anti-backsliding requirements for revoked 
standards. Chapter 11, ``Public Process and Participation,'' describes 
the District's public outreach effort associated with the development 
of the 2016 AQMP. A ``Glossary'' is provided at the end of the 
document, presenting definitions of commonly used terms found in the 
2016 AQMP.
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    \19\ The following chapters in the 2016 AQMP are not relevant to 
the 2006 PM2.5 NAAQS and were not reviewed as part of 
today's action: Chapter 7, ``Current and Future Air Quality--Desert 
Nonattainment Areas,'' describes the air quality status of the 
Coachella Valley, including emissions inventories, designations, and 
current and future air quality; Chapter 8, ``Looking Beyond Current 
Requirements,'' assesses the South Coast air basin's status with 
respect to the 2015 8-hour ozone standard of 70 ppb; Chapter 9, 
``Air Toxic Control Strategy,'' examines the ongoing efforts to 
reduce health risk from toxic air contaminants, co-benefits from 
reducing criteria pollutants, and potential future actions; and 
Chapter 10, ``Climate and Energy,'' provides a description of 
current and projected energy demand and supply issues in the South 
Coast air basin, and the relationship between air quality 
improvement and greenhouse gas mitigation goals.
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    The 2016 AQMP also includes numerous technical appendices, listed 
below:
     Appendix I (Health Effects) presents a summary of 
scientific findings on the health effects of ambient air pollutants.
     Appendix II (Current Air Quality) contains a detailed 
summary of the air quality in 2014, along with prior year trends, in 
both the South Coast and the Coachella Valley.
     Appendix III (Base and Future Year Emission Inventory) 
presents the 2012 base year emissions inventory and projected emission 
inventories of air pollutants in future attainment years for both 
annual average and summer planning inventories.
     Appendix IV-A (SCAQMD's Stationary and Mobile Source 
Control Measures) describes SCAQMD's proposed stationary and mobile 
source control measures to attain the federal ozone and 
PM2.5 standards.
     Appendix IV-B (CARB's Mobile Source Strategy) describes 
CARB's proposed 2016 strategy to attain health-based federal air 
quality standards.
     Appendix IV-C (Regional Transportation Strategy and 
Control Measures) describes the Southern California Association of 
Governments' (SCAG) ``Final 2016-2040 Regional Transportation Plan/
Sustainable Communities Strategy'' and transportation control measures 
included in the 2016 PM2.5 Plan.
     Appendix V (Modeling and Attainment Demonstrations) 
provides the details of the regional modeling for the attainment 
demonstration.
     Appendix VI (Compliance with Other Clean Air Act 
Requirements) provides the District's demonstration that the 2016 AQMP 
complies with specific federal and California Clean Air Act 
requirements.
    The additional documents adopted by CARB on March 23, 2017 
supplement the analysis and demonstrations adopted by the SCAQMD on 
March 3, 2017. In particular, the ``CARB Staff Report, ARB Review of 
2016 AQMP for the South Coast Air Basin and Coachella Valley,'' (``CARB 
Staff Report''), includes in Appendix D a weight of evidence analysis 
for the SCAQMD's attainment demonstration for the 24-hour and annual 
PM2.5 NAAQS. In addition, the 2016 State Strategy discusses 
additional statewide measures, including mobile source measures, that 
will help the area reach attainment of the 2006 PM2.5 
standards by the Serious area attainment date of December 31, 2019.
    We present our evaluation of the 2016 PM2.5 Plan in 
Section V of this proposed rule.

III. Completeness Review of the 2016 PM2.5 Plan

    CAA sections 110(a)(1) and (2) and 110(l) require each state to 
provide reasonable public notice and opportunity for public hearing 
prior to the adoption and submission of a SIP or SIP revision to the 
EPA. To meet this requirement, every SIP submission should include 
evidence that adequate public notice was given and an opportunity for a 
public hearing was provided consistent with the EPA's implementing 
regulations in 40 CFR 51.102.
    Both the District and CARB satisfied applicable statutory and 
regulatory requirements for reasonable public notice and hearing prior 
to adoption and submission of the 2016 PM2.5 Plan. The 
District conducted numerous public workshops, provided a public comment 
period, and held a public hearing prior to the adoption of the 2016 
AQMP on March 3, 2017.\20\ CARB provided the required public notice and 
opportunity for public comment prior to its March 23, 2017 public 
hearing and adoption of the 2016 AQMP and the 2016 State Strategy.\21\ 
Each submission includes proof of publication of notices for the 
respective public hearings, and transcripts for the public 
hearings.\22\ We find, therefore, that the 2016 PM2.5 Plan 
meets the procedural requirements for public notice and hearing in CAA 
sections 110(a) and 110(l).
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    \20\ SCAQMD, Notice of Public Hearing, Proposed 2016 Air Quality 
Management Plan for the South Coast Air Quality Management District 
and Report on the Health Impacts of Particulate Matter Air Pollution 
in the South Coast Air Basin, December 14, 2016.
    \21\ CARB, ``Notice of Public Meeting to Consider Adopting the 
2016 Air Quality Management Plan for Ozone and PM2.5 for 
the South Coast Air Basin and the Coachella Valley,'' March 6, 2017.
    \22\ See Memorandum from Denise Garzaro, Clerk of the Board, 
SCAQMD, to Arlene Martinez, Administrative Secretary, Planning, Rule 
Development, and Area Sources, SUBJECT: SIP Documentation, January 
24, 2017. See also California Air Resources Board, Notice of Public 
Meeting to Consider Adopting the 2016 Air Quality Management Plan 
for Ozone and PM2.5 for the South Coast Air Basin and the 
Coachella Valley, March 6, 2017.
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    CAA section 110(k)(1)(B) requires the EPA to determine whether a 
SIP submission is complete within 60 days of receipt. This section also 
provides that any plan that the EPA has not affirmatively determined to 
be complete or incomplete will become complete by operation of law six 
months after the date of submission. The EPA's SIP completeness 
criteria are found in 40 CFR part 51, Appendix V. The 2016 
PM2.5 Plan, which CARB submitted on April 27, 2017, became 
complete by operation of law on October 27, 2017.

IV. Clean Air Act Requirements for PM2.5 Serious Area Plans

A. PM2.5 Serious Area Plan Requirements

    Upon reclassification of a Moderate nonattainment area as a Serious 
nonattainment area under subpart 4, the CAA requires a state to submit 
the following Serious area SIP elements: \23\
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    \23\ See 81 FR 1514 (January 13, 2016) and 81 FR 58010 (August 
24, 2016).
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    1. A comprehensive, accurate, current inventory of actual emissions 
from all sources of PM2.5 and PM2.5 precursors in 
the area (CAA section 172(c)(3));
    2. Provisions to assure that BACM, including best available control 
technology (BACT), for the control of direct PM2.5 and 
PM2.5 precursors shall

[[Page 49875]]

be implemented no later than 4 years after the area is reclassified 
(CAA section 189(b)(1)(B));
    3. A demonstration (including air quality modeling) that the plan 
provides for attainment as expeditiously as practicable but no later 
than December 31, 2019 (CAA sections 188(c)(2) and 189(b)(1)(A));
    4. Plan provisions that require reasonable further progress (RFP) 
(CAA section 172(c)(2));
    5. Quantitative milestones that are to be achieved every 3 years 
until the area is redesignated attainment and that demonstrate RFP 
toward attainment by the applicable date (CAA section 189(c));
    6. Provisions to assure that control requirements applicable to 
major stationary sources of PM2.5 also apply to major 
stationary sources of PM2.5 precursors, except where a state 
demonstrates to the EPA's satisfaction that such sources do not 
contribute significantly to PM2.5 levels that exceed the 
standard in the area (CAA section 189(e));
    7. Contingency measures to be implemented if the area fails to meet 
RFP or to attain by the applicable attainment date (CAA section 
172(c)(9)); and
    8. A revision to the nonattainment new source review (NSR) program 
to lower the applicable ``major stationary source'' thresholds from 100 
tons per year (tpy) to 70 tpy (CAA section 189(b)(3)).\24\
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    \24\ For any Serious area, the terms ``major source'' and 
``major stationary source'' include any stationary source that emits 
or has the potential to emit at least 70 tons per year of 
PM10 (CAA section 189(b)(3)).
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    Serious area PM2.5 plans must also satisfy: The 
requirements for Moderate area plans in CAA section 189(a), to the 
extent those requirements have not already been satisfied in the 
Moderate area plan submitted for the area; the general requirements 
applicable to all SIP submissions under section 110 of the CAA; the 
requirement to provide necessary assurances that the implementing 
agencies have adequate personnel, funding and authority under CAA 
section 110(a)(2)(E); and the requirements concerning enforcement 
provisions in CAA section 110(a)(2)(C).
    The EPA provided its preliminary interpretations of the CAA's 
requirements for particulate matter plans under part D, title I of the 
Act in the following guidance documents: (1) ``State Implementation 
Plans; General Preamble for the Implementation of Title I of the Clean 
Air Act Amendments of 1990'' (``General Preamble''); \25\ (2) ``State 
Implementation Plans; General Preamble for the Implementation of Title 
I of the Clean Air Act Amendments of 1990; Supplemental'' 
(``Supplement''); \26\ and (3) ``State Implementation Plans for Serious 
PM-10 Nonattainment Areas, and Attainment Date Waivers for PM-10 
Nonattainment Areas Generally; Addendum to the General Preamble for the 
Implementation of Title I of the Clean Air Act Amendments of 1990'' 
(``Addendum'').\27\
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    \25\ 57 FR 13498 (April 16, 1992).
    \26\ 57 FR 18070 (April 28, 1992).
    \27\ 59 FR 41998 (August 16, 1994).
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    Additionally, in an August 24, 2016 final rule entitled, ``Fine 
Particulate Matter National Ambient Air Quality Standards: State 
Implementation Plan Requirements'' (``PM2.5 SIP Requirements 
Rule''),\28\ the EPA established regulatory requirements and provided 
further interpretive guidance on the statutory SIP requirements that 
apply to areas designated nonattainment for the PM2.5 
standards. We discuss these regulatory requirements and interpretations 
of the Act as appropriate in our evaluation of the 2016 
PM2.5 Plan in section V of this proposed rule.
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    \28\ 81 FR 58010.
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V. Review of the South Coast Serious Area Plan Addressing the 2006 
PM2.5 NAAQS

A. Emissions Inventory

1. Requirements for Emissions Inventories
    CAA section 172(c)(3) requires that each SIP include a 
comprehensive, accurate, current inventory of actual emissions from all 
sources of the relevant pollutant or pollutants in the nonattainment 
area. This base year emissions inventory should provide a state's best 
estimate of actual emissions from all sources of the relevant 
pollutants in the area, i.e., all emissions that contribute to the 
formation of a particular NAAQS pollutant. For the PM2.5 
NAAQS, the base year inventory must include direct PM2.5 
emissions, separately reported filterable and condensable 
PM2.5 emissions, and emissions of all chemical precursors to 
the formation of secondary PM2.5 nitrogen oxides 
(NOX), sulfur dioxide (SO2), volatile organic 
compounds (VOC), and ammonia (NH3).\29\
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    \29\ 40 CFR 51.1008.
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    A state must include in its SIP submission documentation explaining 
how the emissions data were calculated. In estimating mobile source 
emissions, a state should use the latest emissions models and planning 
assumptions available at the time the SIP is developed. A state is also 
required to use the EPA's Compilation of Air Pollutant Emission Factors 
(``AP-42'') road dust method for calculating re-entrained road dust 
emissions from paved roads.30 31 The latest EPA-approved 
version of California's mobile source emission factor model for 
estimating tailpipe, brake and tire wear emissions from on-road mobile 
sources is EMFAC2014.\32\
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    \30\ The EPA released an update to AP-42 in January 2011, which 
revised the equation for estimating paved road dust emissions based 
on an updated data regression that included new emission tests 
results. See 76 FR 6328 (February 4, 2011). CARB used the revised 
2011 AP-42 methodology in developing on-road mobile source 
emissions; see https://www.arb.ca.gov/ei/areasrc/fullpdf/full7-9_2016.pdf.
    \31\ AP-42 is the EPA's Compilation of Air Pollutant Emission 
Factors, and has been published since 1972 as the primary source of 
the EPA's emission factor information. It contains emission factors 
and process information for more than 200 air pollution source 
categories. A source category is a specific industry sector or group 
of similar emitting sources. The emission factors have been 
developed and compiled from source test data, material balance 
studies, and engineering estimates.
    \32\ 80 FR 77337 (December 14, 2015). EMFAC is short for 
EMission FACtor. The EPA announced the availability of the EMFAC2014 
model for use in state implementation plan development and 
transportation conformity in California on December 14, 2015. The 
EPA's approval of the EMFAC2014 emissions model for SIP and 
conformity purposes was effective on the date of publication of the 
notice in the Federal Register. EMFAC2014 must be used for all new 
regional emissions analyses and CO, PM10 and 
PM2.5 hot-spot analyses that are started on or after 
December 14, 2017, which is the end of the grace period for 
EMFAC2014.
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    In addition to the base year inventory submitted to meet the 
requirements of CAA section 172(c)(3), the State must also submit a 
projected attainment year inventory and emissions projections for each 
reasonable further progress (RFP) milestone year.\33\ These future 
emissions projections are necessary components of the attainment 
demonstration required under CAA section 189(a)(1) and (b)(1) and the 
demonstration of RFP required under section 172(c)(2).\34\ Emissions 
projections for future years (referred to in the 2016 PM2.5 
Plan as ``baseline inventories'' or ``future baseline inventories'') 
should account for, among other things, the ongoing effects of economic 
growth and adopted emissions control requirements. The SIP should 
include documentation to

[[Page 49876]]

explain how the emissions projections were calculated.
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    \33\ See 40 CFR 51.1008 and 51.1012; see also U.S. EPA, 
``Emissions Inventory Guidance for Implementation of Ozone and 
Particulate Matter National Ambient Air Quality Standards (NAAQS) 
and Regional Haze Regulations'' (July 2017), available at https://www.epa.gov/air-emissions-inventories/air-emissions-inventory-guidance-implementation-ozone-and-particulate.
    \34\ See 40 CFR 51.1004, 51.1008, 51.1011, and 51.1012.
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2. Emissions Inventories in the 2016 PM2.5 Plan
    The annual average daily planning inventories for direct 
PM2.5 and all PM2.5 precursors (NOX, 
SOX, VOC, and ammonia) \35\ for the South Coast 
PM2.5 nonattainment area together with documentation for the 
inventories are found in Chapter 3, Appendix III and Appendix V of the 
2016 AQMP. Appendix V also contains additional inventory documentation 
specific to the air quality modeling inventories. These portions of the 
2016 AQMP contain annual average daily inventories of actual emissions 
for the base year of 2012 and projected inventories for the future RFP 
baseline year of 2017 and the attainment year of 2019, as well as the 
post-attainment RFP year of 2020.\36\ The annual average daily 
inventory is used to evaluate sources of emissions for attainment of 
the 24-hour PM2.5 NAAQS.
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    \35\ The 2016 PM2.5 Plan generally uses ``sulfur 
oxides'' or ``SOX'' in reference to SO2 as a 
precursor to the formation of PM2.5. We use 
``SOX'' and ``SO2'' interchangeably throughout 
this notice.
    \36\ The 2016 PM2.5 Plan includes summer day 
inventories for ozone planning purposes and both a Moderate area 
plan and a Serious area plan for the 2012 PM2.5 NAAQS. 
The 2016 PM2.5 Plan therefore includes annual average and 
summer day inventories for all years between 2017 and 2031, except 
2029.
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    Future emissions forecasts are primarily based on demographic and 
economic growth projections provided by SCAG, the metropolitan planning 
organization (MPO) for the Los Angeles area. Baseline inventories 
reflect all district control measures adopted prior to December 2015 
and CARB rules adopted by November 2015. Growth factors used to project 
these baseline inventories are derived mainly from data obtained from 
SCAG.\37\
---------------------------------------------------------------------------

    \37\ See 2016 AQMP, Appendix III, page III-2-6.
---------------------------------------------------------------------------

    The emissions inventory is divided into two major source 
classifications: Stationary sources and mobile sources, which include 
on-road and non-road sources of emissions. Stationary sources include 
point and area sources. Point sources in the South Coast air basin that 
emit more than 4 tons per year (tpy) or more of VOC, NOX, 
SO2, or PM report annual emissions to the District. Point 
source emissions for the 2012 base year emissions inventory are 
generally based on reported data from facilities using the District's 
Annual Emissions Reporting (AER) program.\38\ Area sources include 
smaller emissions sources distributed across the nonattainment area. 
CARB and the District estimate emissions for about 400 area source 
categories using established inventory methods, including publicly-
available emission factors and activity information. Activity data may 
come from national survey data such as from the Energy Information 
Administration or from local sources such as the Southern California 
Gas Company, paint suppliers, and district databases. Emission factors 
can be based on a number of sources including source tests, compliance 
reports, and the EPA's AP-42.
---------------------------------------------------------------------------

    \38\ See http://www.aqmd.gov/regulations/compliance/annual-emission-reporting.
---------------------------------------------------------------------------

    Emissions inventories are constantly being revised and improved. 
Between the finalization of California's plan addressing Moderate area 
requirements for the 2006 PM2.5 NAAQS in the South Coast 
(``2012 PM2.5 Plan'') and the development of the 2016 
PM2.5 Plan, the District improved and updated its emissions 
estimation methodologies for liquefied petroleum gas combustion 
sources, natural gas combustion sources, NOX emission 
sources subject to the District's Regional Clean Air Incentives Market 
(RECLAIM) program (based on 2015 program amendments), livestock waste 
management operations, gasoline dispensing facilities, composting 
operations, oil and gas production, and architectural coatings.
    On-road emissions inventories are calculated using CARB's EMFAC2014 
model and the travel activity data provided by SCAG in ``The 2016-2040 
Regional Transportation Plan/Sustainable Communities Strategy.'' \39\ 
Re-entrained paved road dust emissions were calculated using the EPA's 
AP-42 road dust methodology.\40\
---------------------------------------------------------------------------

    \39\ See http://scagrtpscs.net/Pages/FINAL2016RTPSCS.aspx.
    \40\ See CARB, Miscellaneous Process Methodology 7.9 Entrained 
Road Travel, Paved Road Dust, (Revised and updated, November 2016) 
available at https://www.arb.ca.gov/ei/areasrc/fullpdf/full7-9_2016.pdf.
---------------------------------------------------------------------------

    CARB provided emission inventories for off-road equipment, 
including construction and mining equipment, industrial and commercial 
equipment, lawn and garden equipment, agricultural equipment, ocean-
going vessels, commercial harbor craft, locomotives, cargo handling 
equipment, pleasure craft, and recreational vehicles. CARB uses several 
models to estimate emissions for more than one hundred off-road 
equipment categories.\41\ Aircraft emissions are developed in 
conjunction with the airports in the region.
---------------------------------------------------------------------------

    \41\ See 2016 PM2.5 Plan, Appendix III, p. III-1-24.
---------------------------------------------------------------------------

    Table 1 provides a summary of the District's 2012 base year 
emissions estimates as annual averages, for direct PM2.5 and 
all PM2.5 precursors. These inventories provide the basis 
for the control measure analysis and the RFP and attainment 
demonstrations in the 2016 PM2.5 Plan. For a more detailed 
discussion of the inventories, see Appendix III of the 2016 AQMP.

                                  Table 1--South Coast 2012 Base Year Emissions
                                           [Annual average, tons/day]
----------------------------------------------------------------------------------------------------------------
                                   Direct PM2.5
                                                        NOX             SO2             VOC           Ammonia
----------------------------------------------------------------------------------------------------------------
Stationary and Area Sources.....              44              70              10             212              63
On-Road Mobile Sources..........              14             317               2             158              18
Off-Road Mobile Sources.........               8             153               6             100               0
                                 -------------------------------------------------------------------------------
    Total.......................              66             540              18             470              81
----------------------------------------------------------------------------------------------------------------
Source: 2016 AQMP, Chapter 3, Table 3-1A. Values may not be precise due to rounding.

Condensable Particulate Matter
    The PM2.5 SIP Requirements Rule states that ``[t]he 
inventory shall include direct PM2.5 emissions, separately 
reported PM2.5 filterable and condensable emissions, and 
emissions of the scientific PM2.5 precursors, including 
precursors that are not PM2.5 plan precursors pursuant to a 
precursor demonstration under Sec.  51.1006.'' \42\ On June 26, 2018, 
SCAQMD submitted a technical supplement containing emissions estimates 
for both condensable and filterable PM2.5 emissions from 
specified sources of

[[Page 49877]]

direct PM2.5 in the South Coast area.\43\ The supplement 
provides filterable and condensable emissions estimates, expressed as 
annual average PM2.5 emissions, for all of the identified 
source categories for the 2012 base year, the 2017 RFP year, and the 
2019 attainment year, as well as subsequent years.\44\
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    \42\ 40 CFR 51.1008(a)(1)(iv).
    \43\ Letter from Philip Fine, Deputy Executive Officer, SCAQMD, 
to Amy Zimpfer, Associate Director, EPA Region IX, regarding 
``Condensable and Filterable Portions of PM2.5 emissions 
in the 2016 AQMP,'' June 26, 2018.
    \44\ Id. at Appendix A.
---------------------------------------------------------------------------

    The 2016 PM2.5 Plan relies on several SIP-approved rules 
that regulate direct PM emissions as part of the PM2.5 
control strategy (e.g., Rule 445 (Wood-Burning Devices), adopted March 
7, 2008, most recently revised May 3, 2013; Rule 1138 (Control of 
Emissions from Restaurant Operations), adopted November 14, 1997; and 
Rule 1155 (Particulate Matter (PM) Control Devices), adopted December 
4, 2009, amended May 2, 2014). As part of our action on any rules that 
regulate direct PM2.5 emissions, we evaluate the emissions 
limits in the rule to ensure that they appropriately address 
condensable PM, as required by 40 CFR 51.1010(e). We note that the SIP-
approved version of Rule 1138 requires testing according to the 
District's protocol, which requires measurement of both condensable and 
filterable PM in accordance with SCAQMD Test Method 5.1.\45\ We also 
note that the SIP-approved version of Rule 1155 requires measurement of 
both condensable and filterable PM in accordance with SCAQMD Test 
Methods 5.1, 5.2, or 5.3 as applicable.46 47
---------------------------------------------------------------------------

    \45\ See Rule 1138 (adopted November 14, 1997, approved July 11, 
2001 at 66 FR 36170), paragraph (c)(1) and (g) and SCAQMD Protocol 
paragraph 3.1, and SCAQMD Protocol, Determination of Particulate and 
Volatile Organic Compound Emissions from Restaurant Operations, 
November 14, 1997 (available at http://yosemite.epa.gov/R9/
R9Testmethod.nsf/0/3D4DEB4D21AB4AAF882570AD005DFF69/$file/
SC%20Rest%20emiss.pdf).
    \46\ See Rule 1155 (adopted December 4, 2009, revised May 2, 
2014, approved into the SIP March 16, 2015 at 80 FR 13495), 
paragraph (e)(6).
    \47\ See SCAQMD Test Method 5.1, Determination of Particulate 
Matter Emissions from Stationary Sources Using a Wet Impingement 
Train, March 1989; SCAQMD Test Method 5.2, Determination of 
Particulate Matter Emissions from Stationary Sources Using Heated 
Probe and Filter, March 1989; and SCAQMD Test Method 5.3, 
Determination of Particulate Matter Emissions from Stationary 
Sources Using an in-Stack Filter, October 2005.
---------------------------------------------------------------------------

3. EPA's Evaluation and Proposed Action
    The emissions inventories in the 2016 PM2.5 Plan were 
made available to the public for comment and were subject to public 
hearing at both the District and State levels.\48\
---------------------------------------------------------------------------

    \48\ See SCAQMD Board Resolution 17-2, p.3 and CARB Resolution 
17-8, p. 4.
---------------------------------------------------------------------------

    The inventories in the 2016 PM2.5 Plan are based on the 
most current and accurate information available to the State and 
District at the time the Plan and its inventories were being developed, 
including the latest EPA-approved version of California's mobile source 
emissions model, EMFAC2014, and the EPA's most recent AP-42 methodology 
for paved road dust.\49\ The inventories comprehensively address all 
source categories in the South Coast and were developed consistent with 
the EPA's inventory guidance. In accordance with 40 CFR 51.1008(b), the 
2012 base year is one of the three years for which monitored data were 
used for reclassifying the area to Serious, and it represents actual 
annual average emissions of all sources within the nonattainment area. 
Direct PM2.5 and all PM2.5 precursors are 
included in the inventories, and filterable and condensable direct 
PM2.5 emissions are identified separately. For these 
reasons, we are proposing to approve the 2012 base year emissions 
inventory in the 2016 PM2.5 Plan as meeting the requirements 
of CAA section 172(c)(3) and 40 CFR 51.1008. We are also proposing to 
find that the future baseline inventories in the Plan provide an 
adequate basis for the BACM, RFP, and attainment demonstrations in the 
2016 PM2.5 Plan.
---------------------------------------------------------------------------

    \49\ CARB submitted the EMFAC2014 model to the EPA on May 21, 
2015, and the EPA approved the model for use in California SIPs. 80 
FR 77337 (December 14, 2015).
---------------------------------------------------------------------------

B. PM2.5 Precursors

1. Requirements for the Control of PM2.5 Precursors
    The composition of PM2.5 is complex and highly variable 
due in part to the large contribution of secondary PM2.5 to 
total fine particle mass in most locations, and to the complexity of 
secondary particle formation processes. A large number of possible 
chemical reactions, often non-linear in nature, can convert gaseous 
SO2, NOX, VOC, and ammonia to PM2.5, 
making them precursors to PM2.5.\50\ Formation of secondary 
PM2.5 may also depend on atmospheric conditions, including 
solar radiation, temperature, and relative humidity, and the 
interactions of precursors with preexisting particles and with cloud or 
fog droplets.\51\
---------------------------------------------------------------------------

    \50\ EPA, Air Quality Criteria for Particulate Matter (EPA/600/
P-99/002aF, October 2004), Chapter 3.
    \51\ EPA, Regulatory Impact Analysis for the Final Revisions to 
the National Ambient Air Quality Standards for Particulate Matter 
(EPA/452/R-12-005, December 2012), p. 2-1.
---------------------------------------------------------------------------

    The 2007 PM2.5 Implementation Rule contained rebuttable 
presumptions concerning the four PM2.5 precursors applicable 
to attainment plans and control measures related to those plans.\52\ 
Although the rule included presumptions that states should address 
SO2 and NOX emissions in their attainment plans, 
it also included presumptions that regulation of VOCs and ammonia was 
not necessary. Specifically, in 40 CFR 51.1002(c) (as effective July 1, 
2007), the EPA provided, among other things, that a state was ``not 
required to address VOC [and ammonia] as . . . PM2.5 
attainment plan precursor[s] and to evaluate sources of VOC [and 
ammonia] emissions in the state for control measures,'' unless the 
state or the EPA provided an appropriate technical demonstration 
showing that emissions from sources of these pollutants ``significantly 
contribute'' to PM2.5 concentrations in the nonattainment 
area.\53\
---------------------------------------------------------------------------

    \52\ 40 CFR 51.1002(c) (as effective July 1, 2007).
    \53\ 40 CFR 51.1002(c)(3), (4) (as effective July 1, 2007). See 
also 2007 PM2.5 Implementation Rule, 72 FR 20586 at 
20589-97 (April 25, 2007).
---------------------------------------------------------------------------

    In NRDC, however, the United States Court of Appeals for the D.C. 
Circuit (``D.C. Circuit'') remanded the EPA's 2007 PM2.5 
Implementation Rule in its entirety, including the presumptions 
concerning VOC and ammonia in that rule.\54\ Although the court 
expressly declined to decide the specific challenge to these 
presumptions concerning precursors,\55\ the court cited CAA section 
189(e) \56\ to support its observation that ``[a]mmonia is a precursor 
to fine particulate matter, making it a precursor to both 
PM2.5 and PM10'' and that ``[f]or a 
PM10 nonattainment area governed by subpart 4, a precursor 
is presumptively regulated.'' \57\ Consistent with the NRDC decision, 
the EPA now interprets the Act to require that under subpart 4, a state 
must evaluate all PM2.5 precursors for regulation unless, 
for any given PM2.5 precursor, it demonstrates to the 
Administrator's satisfaction that such precursor does not contribute

[[Page 49878]]

significantly to PM2.5 levels that exceed the NAAQS in the 
nonattainment area.
---------------------------------------------------------------------------

    \54\ NRDC v. EPA, 706 F.3d 428 (D.C. Cir. 2013).
    \55\ Id. at 437, n. 10.
    \56\ Section 189(e) of the CAA states that ``[t]he control 
requirements applicable under plans in effect under this part for 
major stationary sources of PM10 shall also apply to 
major stationary sources of PM10 precursors, except where 
the Administrator determines that such sources do not contribute 
significantly to PM10 levels which exceed the standard in 
the area.''
    \57\ 706 F.3d at 436, n. 7 (D.C. Cir. 2013).
---------------------------------------------------------------------------

    The provisions of subpart 4 do not define the term ``precursor'' 
for purposes of PM2.5, nor do they explicitly require the 
control of any specifically identified PM precursor. The statutory 
definition of ``air pollutant,'' however, provides that the term 
``includes any precursors to the formation of any air pollutant, to the 
extent the Administrator has identified such precursor or precursors 
for the particular purpose for which the term `air pollutant' is 
used.'' \58\ The EPA has identified SO2, NOX, 
VOC, and ammonia as precursors to the formation of PM2.5. 
Accordingly, the attainment plan requirements of subpart 4 apply to 
emissions of all four precursor pollutants and direct PM2.5 
from all types of stationary, area, and mobile sources, except as 
otherwise provided in the Act (e.g., CAA section 189(e)).
---------------------------------------------------------------------------

    \58\ See CAA section 302(g).
---------------------------------------------------------------------------

    Section 189(e) of the Act requires that the control requirements 
for major stationary sources of direct PM10 also apply to 
major stationary sources of PM10 precursors, except where 
the Administrator determines that such sources do not contribute 
significantly to PM10 levels that exceed the standard in the 
area. Section 189(e) contains the only express exception to the control 
requirements under subpart 4 (e.g., requirements for reasonably 
available control measures (RACM) and reasonably available control 
technology (RACT), BACM and BACT, most stringent measures (MSM), and 
NSR) for sources of direct PM2.5 and PM2.5 
precursor emissions. Although section 189(e) explicitly addresses only 
major stationary sources, the EPA interprets the Act as authorizing it 
also to determine, under appropriate circumstances, that regulation of 
specific PM2.5 precursors from other source categories in a 
given nonattainment area is not necessary. For example, under the EPA's 
longstanding interpretation of the control requirements that apply to 
stationary, area, and mobile sources of PM10 precursors in 
the nonattainment area under CAA section 172(c)(1) and subpart 4,\59\ a 
state may demonstrate in a SIP submission that control of a certain 
precursor pollutant is not necessary in light of its insignificant 
contribution to ambient PM10 levels in the nonattainment 
area.\60\
---------------------------------------------------------------------------

    \59\ General Preamble, 57 FR 13498 at 13539-42 (April 16, 1992).
    \60\ Courts have upheld this approach to the requirements of 
subpart 4 for PM10. See, e.g., Assoc. of Irritated 
Residents v. EPA, et al., 423 F.3d 989 (9th Cir. 2005).7
---------------------------------------------------------------------------

    The PM2.5 SIP Requirements Rule recognizes that the 
treatment of PM2.5 precursors is an important issue in 
developing a PM2.5 attainment plan.\61\ The rule provides 
flexibility for areas where a particular PM2.5 precursor or 
precursors may not contribute significantly to PM2.5 levels 
that exceed the NAAQS. The rule provides for optional precursor 
demonstrations that a state may choose to submit to the EPA to 
establish that sources of particular precursors need not be regulated 
for purposes of attainment planning or in the nonattainment NSR (NNSR) 
permitting program for a specific nonattainment area.
---------------------------------------------------------------------------

    \61\ See, e.g., 81 FR 58010 at 58017.
---------------------------------------------------------------------------

    We are evaluating the 2016 PM2.5 Plan in accordance with 
the presumption embodied within subpart 4 that all PM2.5 
precursors must be addressed in the State's evaluation of potential 
control measures, unless the State adequately demonstrates that 
emissions of a particular precursor or precursors do not contribute 
significantly to ambient PM2.5 levels that exceed the 
PM2.5 NAAQS in the nonattainment area. In reviewing any 
determination by the State to exclude a PM2.5 precursor from 
the required evaluation of potential control measures, we consider both 
the magnitude of the precursor's contribution to ambient 
PM2.5 concentrations in the nonattainment area and the 
sensitivity of ambient PM2.5 concentrations in the area to 
reductions in emissions of that precursor.
2. Evaluation of Precursors in the 2016 PM2.5 Plan
    The 2016 PM2 Plan discusses the five primary pollutants 
that contribute to the mass of the ambient aerosol (i.e., ammonia, 
NOX, SO2, VOC, and directly emitted 
PM2.5) and states that various combinations of reductions in 
these pollutants could all provide a path to clean air.\62\ The 2016 
PM2.5 Plan assesses and presents the relative effectiveness 
of each ton of precursor emission reductions, considering the resulting 
ambient improvements in PM2.5 air quality measured in 
micrograms per cubic meter.\63\ As presented in the weight of evidence 
discussion in the 2016 PM2.5 Plan, trends of 
PM2.5 and NOx emissions suggest a direct response between 
lower emissions and improved air quality. The Community Multiscale Air 
Quality Modeling System (CMAQ) simulations in the 2016 PM2.5 
Plan provide a set of response factors for direct PM2.5, 
NOX, SO2 and VOCs, based on improvements to 
ambient 24-hour PM2.5 levels resulting from reductions of 
each pollutant. The contribution of ammonia emissions is embedded as a 
component of the SO2 and NOX factors because 
ammonium nitrate and ammonium sulfate are the resultant particulate 
species formed in the atmosphere.
---------------------------------------------------------------------------

    \62\ 2016 PM2.5 Plan, Appendix VI, p. VI-F-1, as well 
as Appendix V, p. V-5-51 and Appendix V, Attachment 8, Relative 
Contributions of Precursor Emissions Reductions to Simulated 
Controlled Future-Year 24-hour PM2.5 Concentrations.
    \63\ 2016 PM2.5 Plan, Appendix V, Attachment 8, 
Relative Contributions of Precursor Emissions Reductions to 
Simulated Controlled Future-Year 24-hour PM2.5 
Concentrations.
---------------------------------------------------------------------------

    The 2016 PM2.5 Plan describes how reductions in 
NOX, SO2, VOC and ammonia precursor emissions 
contribute to attainment of the PM2.5 standard in the South 
Coast area and contain the District's evaluation of available control 
measures for all four of these PM2.5 precursor pollutants, 
in addition to direct PM2.5, consistent with the regulatory 
presumptions under subpart 4. The 2016 PM2.5 Plan also 
contains a discussion of the control requirements applicable to major 
stationary sources under CAA section 189(e).\64\
---------------------------------------------------------------------------

    \64\ See 2016 PM2.5 Plan at Appendix VI-F. In a 
separate rulemaking to approve revisions to SCAQMD's nonattainment 
New Source Review (NNSR) program, the EPA determined that the 
control requirements applicable under the SCAQMD SIP to major 
stationary sources of direct PM2.5 also apply to major 
stationary sources of NOX, SO2, and VOC, and 
that major stationary sources of ammonia do not contribute 
significantly to PM2.5 levels which exceed the 
PM2.5 standards in the area. See 80 FR 24821 (May 1, 
2015). This rulemaking addressed the control requirements of CAA 
section 189(e) only for NNSR purposes and not for attainment 
planning purposes under subpart 1 and 4 of part D, title I of the 
Act.
---------------------------------------------------------------------------

3. Proposed Action
    Based on a review of the information provided in the 2016 
PM2.5 Plan and other information available to the EPA, we 
agree with the State's conclusion that all four chemical precursors to 
PM2.5 must be regulated for purposes of attaining the 2006 
PM2.5 NAAQS in the South Coast area. We discuss the state's 
evaluation of potential control measures for direct PM2.5, 
NOX, SO2, VOC and ammonia in section V.C below.

C. Best Available Control Measures

1. Requirements for Best Available Control Measures
    For any serious PM2.5 nonattainment area, section 
189(b)(1)(B) of the Act requires that a state submit provisions to 
assure that BACM for the control of PM2.5 and 
PM2.5 precursors shall be implemented no later than four 
years after the date the area is reclassified as a serious area. The 
EPA defines BACM as, among other things, the maximum

[[Page 49879]]

degree of emissions reduction achievable for a source or source 
category, which is determined on a case-by-case basis considering 
energy, environmental, and economic impacts.\65\ We generally consider 
BACM a control level that goes beyond existing RACM-level controls, for 
example by expanding the use of RACM controls or by requiring 
preventative measures instead of remediation.\66\ Indeed, as 
implementation of BACM and BACT is required when a Moderate 
nonattainment area is reclassified as Serious due to its inability to 
attain the NAAQS through implementation of ``reasonable'' measures, it 
is logical that ``best'' control measures should represent a more 
stringent and potentially more costly level of control.\67\
---------------------------------------------------------------------------

    \65\ Addendum at 42010, 42013.
    \66\ Id. at 42011, 42013.
    \67\ Id. at 42009-42010.
---------------------------------------------------------------------------

    Section 189(b)(1)(B) of the Act allows states, in appropriate 
circumstances, to delay implementation of BACM until the date four 
years after reclassification. Because the EPA reclassified the South 
Coast area as a Serious area for the 2006 PM2.5 NAAQS 
effective February 12, 2016, the date four years after reclassification 
is February 12, 2020. In this case, however, all BACM for 
PM2.5 and PM2.5 precursors in the South Coast 
must be implemented no later than December 31, 2019, the outermost 
statutory attainment date for the South Coast area under section 
188(c)(2).\68\
---------------------------------------------------------------------------

    \68\ CAA section 189(b)(1)(B) establishes an outermost deadline 
(``no later than four years after the date the area is 
reclassified'') and does not preclude an earlier implementation 
deadline for BACM where necessary to satisfy the attainment 
requirements of the Act.
---------------------------------------------------------------------------

    Under the PM2.5 SIP Requirements Rule, control measures 
that can be implemented in whole or in part by the end of the fourth 
year following an area's reclassification as a Serious area are 
considered BACM, and control measures that can only be implemented 
after this period but before the attainment date are considered 
``additional feasible measures.'' \69\ The EPA has defined ``additional 
feasible measures'' as ``those measures and technologies that otherwise 
meet the criteria for BACM/BACT but that can only be implemented in 
whole or in part beginning 4 years after reclassification of an area, 
but no later than the statutory attainment date for the area.'' \70\ 
Given that the statutory attainment date is less than three years from 
the effective date of the reclassification of the South Coast area, 
additional feasible measures are not required in this particular case.
---------------------------------------------------------------------------

    \69\ 40 CFR 51.1010(a)(4). ``Additional feasible measures'' may 
be necessary in certain circumstances to implement the requirements 
of CAA section 172(c)(6), which states that nonattainment area plans 
shall include enforceable emission limitations and such other 
control measures, means or techniques, as well as schedules and 
timetables for compliance, as may be necessary or appropriate to 
provide for attainment of the NAAQS by the applicable attainment 
date.
    \70\ 40 CFR 51.1000.
---------------------------------------------------------------------------

    The Addendum and the PM2.5 SIP Requirements Rule discuss 
the following steps for determining BACM:
    1. Develop a comprehensive emission inventory of the sources of 
directly-emitted PM2.5 and PM2.5 precursors;
    2. Identify potential control measures;
    3. Determine whether an available control measure or technology is 
technologically feasible; and
    4. Determine whether an available control technology or measure is 
economically feasible.\71\
---------------------------------------------------------------------------

    \71\ Addendum. at 42012-42014, and 81 FR 58010 (August 24, 2016) 
at 58084-58085.
---------------------------------------------------------------------------

    Once these analyses are complete, a state must use this information 
to develop enforceable control measures and submit them to the EPA for 
evaluation under CAA section 110. We use these steps as guidelines in 
our evaluation of the BACM measures and related analyses in the 2016 
PM2.5 Plan.
2. BACM Analysis in the 2016 PM2.5 Plan
a. Identifying the Sources of PM2.5 and PM2.5 
Precursors
    The first step in determining BACM is to develop a detailed 
emissions inventory of the sources of direct PM2.5 and 
PM2.5 precursors that can be used with modeling to determine 
the effects of these sources on ambient PM2.5 levels. As 
discussed in section V.A of this proposed rule, Chapter 3 and Appendix 
III of the 2016 AQMP contain the planning inventories for direct 
PM2.5 and all PM2.5 precursors (NOX, 
SO2, VOC, and ammonia) for the South Coast PM2.5 
nonattainment area together with documentation to support these 
inventories. Based on these inventories, the District identified the 
following source categories as key emission sources in the South Coast 
nonattainment area:

 Residential Fuel Combustion--Wood Combustion--Wood Stoves
 Farming Operations--Livestock Wastes
 Paved Road Dust--Paved Road Travel Dust--Local Streets
 Cooking--Commercial Charbroiling
 Other (Miscellaneous Processes)--Other \72\
---------------------------------------------------------------------------

    \72\ This source category includes ammonia emissions from 
humans, pets, diapers and household ammonia use. See electronic mail 
from Kalam Cheung, SCAQMD, to Wienke Tax, EPA Region IX, September 
29, 2017.
---------------------------------------------------------------------------

 Light-Duty Passenger-- Catalyst Hot Stabilized
 Light-Duty Passenger--Catalyst Brake Wear
 Light-Duty Trucks 2--Catalyst Hot Stabilized
 Medium-Duty Trucks--Catalyst Hot Stabilized
 Medium-Heavy-Duty Diesel Trucks--Diesel Hot Stabilized
 Heavy-Heavy-Duty Diesel Trucks--Diesel Hot Stabilized
 Commercial/Industrial Mobile Equipment--Construction and 
Mining.\73\
---------------------------------------------------------------------------

    \73\ 2016 AQMP, Appendix VI, p. VI-A-14, Table VI-A-6.

Of these 12 source categories, the District identified four categories 
---------------------------------------------------------------------------
that it has the authority to regulate:

 Residential Fuel Combustion--Wood combustion--Wood stoves
 Farming operations--Livestock Waste
 Paved Road dust--Paved Road Travel Dust--Local Streets
 Cooking--Commercial Charbroiling.\74\
---------------------------------------------------------------------------

    \74\ Id.

    Appendix VI of the 2016 AQMP identifies the stationary, area, and 
mobile sources of direct PM2.5, NOX, VOC, 
SO2 and ammonia in the South Coast that are subject to State 
or District emissions control measures, or transportation control 
measures implemented by the SCAG. Table VI-A-6 of the 2016 AQMP lists 
the key source categories together with each source category's 2012 
emissions levels expressed as ``PM2.5-equivalent'' emissions 
in tons per day (tpd).
    Based on this identification of stationary, area, and mobile 
sources of direct PM2.5, NOX, VOC, SO2 
and ammonia in the South Coast, we believe the 2016 PM2.5 
Plan appropriately identifies all emission sources and source 
categories that must be subject to evaluation for potential control 
measures consistent with the requirements of subpart 4.
b. Identification and Implementation of BACM
    As part of its process for identifying candidate BACM and 
considering the technical and economic feasibility of additional 
control measures, CARB, the District and SCAG reviewed the EPA's 
guidance documents on BACM, guidance documents on control measures for 
direct PM2.5, NOX, VOC, ammonia and 
SO2 emissions sources, and control measures implemented in 
other ozone and PM2.5 nonattainment areas in California and 
other states. The State, District, and SCAG's evaluations of potential 
BACM for each source category identified above are found in

[[Page 49880]]

Appendix IV-A, Appendix IV-B, Appendix IV-C, and Appendix VI of the 
2016 AQMP. In the following sections, we review key components of the 
State, District, and SCAG's demonstrations concerning BACM for the 
identified sources of direct PM2.5, NOX, VOC, 
SO2 and ammonia emissions in the South Coast. We provide a 
more detailed evaluation of several of the District's regulations in 
our technical support document (TSD),\75\ together with recommendations 
for possible improvements to these rules.
---------------------------------------------------------------------------

    \75\ US EPA Region 9, Technical Support Document for the 
Proposed Approval of South Coast AQMD's Serious Area Plan for the 
2006 PM2.5 National Ambient Air Quality Standards (Docket 
Number EPA-R09-OAR-2017-0490), September 2018.
---------------------------------------------------------------------------

    Based on our evaluation of these demonstrations, we propose to 
determine that the 2016 PM2.5 Plan provides for the 
implementation of BACM for sources of direct PM2.5 and 
PM2.5 precursors as expeditiously as practicable, for the 
purposes of the 2006 PM2.5 NAAQS in the South Coast area in 
accordance with the requirements of CAA section 189(b)(1)(B) and 40 CFR 
51.1010.
i. State and District Measures for Stationary and Area Sources
    The District's BACM process and control measure evaluations are 
described in detail in Appendix IV-A and Appendix VI of the 2016 AQMP. 
For each identified source category, the District identified both its 
adopted control measures and potential additional control measures 
based on measures implemented in other areas, measures identified in 
EPA regulations or guidance (e.g., in control technique guidelines 
(CTGs), alternative control technique documents (ACTs), new source 
performance standards (NSPSs), or in the EPA's ``Menu of Control 
Measures for NAAQS Implementation''), or measures identified in prior 
EPA rulemaking documents (e.g., recommendations in the EPA's technical 
support documents for prior SIP actions).\76\ \77\ The District 
evaluated these potential additional control measures to determine 
whether implementation of the measures would be technologically and 
economically feasible in the South Coast.\78\ In addition, the District 
considered other available control options (beyond those included in 
other SIPs or identified in federal/state regulations or guidance), 
such as measures that the State or District have previously considered 
``beyond RACM.'' The District also evaluated these potential control 
measures to determine whether implementation would be technologically 
and economically feasible in the South Coast.
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    \76\ 2016 AQMP, Appendix VI, pp. VI-A-12 to VI-A-36.
    \77\ The Menu of Control Measures can be found at https://www.epa.gov/air-quality-implementation-plans/menu-control-measures-naaqs-implementation.
    \78\ 2016 AQMP, Appendix VI, pp. VI-A-32 to VI-A-40.
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Residential Wood-Burning Devices

    SCAQMD Rule 445 (``Wood-Burning Devices''), amended May 3, 2013, 
establishes requirements for the sale, operation, and installation of 
wood-burning devices within the South Coast air basin that are designed 
to reduce PM emissions from such devices. The EPA approved Rule 445, as 
amended, into the California SIP on September 26, 2013.\79\
---------------------------------------------------------------------------

    \79\ 78 FR 59249.
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    Under Rule 445, persons who manufacture, sell, or install wood-
burning devices, commercial firewood sellers, and property owners or 
tenants who operate wood-burning devices are subject to specific 
requirements concerning the types of wood-burning devices that may be 
manufactured, sold, or installed, the types of fuels that may be burned 
in such devices, and labeling requirements. Rule 445 also establishes a 
mandatory winter wood-burning curtailment whenever the Executive 
Officer declares that ambient PM2.5 levels are forecasted to 
exceed 30 [micro]g/m\3\ at specified source receptor areas.
    The District compared the requirements of Rule 445 to several rules 
implemented elsewhere in California that are designed to limit PM 
emissions from residential wood-burning devices. Based on this review, 
the District concludes that Rule 445 is generally equivalent to these 
other rules. Rule 445 does not require the removal of old wood stoves 
upon resale of a home, as do rules implemented in several other areas, 
but it does contain a categorical prohibition on the installation of 
any wood-burning device in new residential developments. Several other 
air districts prohibit or limit the installation of non-certified wood-
burning devices but allow for installation of EPA-certified devices in 
new developments.
    Based on our evaluation of the information provided in the 2016 
AQMP and additional information obtained during our review of the Plan, 
we agree with the SCAQMD's conclusion that Rule 445 implements BACM for 
the control of PM2.5 from residential wood-burning devices.
Confined Animal Facilities and Livestock Waste
    SCAQMD Rule 1127 (``Emission Reductions from Livestock Waste''), 
adopted August 6, 2004, and Rule 223 (``Emission Reduction Permits for 
Large Confined Animal Facilities''), adopted June 2, 2006, together 
establish requirements to reduce emissions of ammonia, VOCs, and other 
pollutants emitted from confined animal facilities and related 
operations. The EPA approved Rule 1127 and Rule 223 into the California 
SIP on May 23, 2013 and July 13, 2015, respectively.\80\
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    \80\ 78 FR 30768 and 80 FR 39966.
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    Rule 1127 applies to dairy farms with 50 or more cows, heifers, 
and/or calves and to manure processing operations, such as composting 
operations and anaerobic digesters. The rule requires operators of 
dairy farms and manure processing operations to use specified best 
management practices to reduce pollutant emissions during the removal 
and disposal of manure from corrals, among other things. Rule 223 
applies to large confined animal facilities (LCAFs) and prohibits 
owners/operators of such facilities from building, altering, replacing 
or operating an LCAF without first obtaining a permit from the 
District. The permit application must include, among other things, an 
emissions mitigation plan that identifies the mitigation measures to be 
implemented at the facility. For each source category covered by the 
rule, owners/operators must implement a prescribed number of mitigation 
measures among a list of options or as approved by the District, CARB, 
and the EPA.
    The District compared the key requirements of Rule 1127 and Rule 
223 to analogous requirements implemented in other parts of California 
and in Idaho. Based on this evaluation, the District concludes that 
Rule 1127 and Rule 223 together establish requirements for confined 
animal facilities and related operations that are generally equivalent 
to the requirements in these other areas. The District also considered 
several additional control methods to further reduce ammonia emissions 
from livestock waste, including application of acidifiers (sodium 
bisulfate), dietary manipulation, feed additives, manure slurry 
injection, and microbial/manure additives. The 2016 AQMP contains a 
commitment by the District to adopt in 2019 an additional ammonia 
control measure for livestock waste to be implemented in 2020. The 
proposed measure is identified in the plan as BCM-04.\81\
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    \81\ See 2016 AQMP, Chapter 4, Table 4-7; 2016 AQMP, Appendix 
IV-A, pp. IV-A-202 to IV-A-209 (describing BCM-04); and SCAQMD, 
Governing Board Resolution No. 17-2 (March 3, 2017), at p. 9.

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[[Page 49881]]

    Based on our evaluation of the information provided in the 2016 
AQMP and additional information obtained during our review of the Plan, 
we agree with the SCAQMD's conclusion that Rule 1127 and Rule 223 
together implement BACM for the control of ammonia and VOCs from 
confined animal facilities and related operations.
Paved and Unpaved Roads and Livestock Operations
    Rule 1186 (``PM10 Emissions from Paved and Unpaved 
Roads, and Livestock Operations''), amended July 11, 2008, establishes 
requirements to reduce the entrainment of particulate matter as a 
result of vehicular travel on paved and unpaved public roads and 
livestock operations. The EPA approved Rule 1186 into the California 
SIP on March 7, 2012.\82\
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    \82\ 77 FR 13495.
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    Under Rule 1186, owners and operators of paved roads with average 
daily vehicle trips exceeding certain thresholds must remove visible 
roadway accumulation within specified periods of time and provide 
curbing or paved shoulders of certain widths when constructing new or 
widened roads. Rule 1186 also requires local government agencies that 
own or maintain paved roads to procure only certified street sweeping 
equipment for routine street sweeping; establishes requirements for 
owners and operators of certain unpaved roads to pave, apply chemical 
stabilization, or install signs to reduce vehicular speeds; and 
requires owners and operators of livestock operations to cease hay 
grinding activities during certain times of day, if visible emissions 
extend more than 50 feet from a hay grinding source.
    The District compared the key requirements of Rule 1186 to 
analogous requirements implemented in other parts of California and in 
Nevada. Based on this evaluation, the District concludes that Rule 1186 
is generally equivalent to the requirements in these other areas. To 
further reduce PM2.5 emissions in areas with high vehicular 
activity, the District also considered several additional control 
techniques, such as increasing the frequency of street sweeping with 
certified equipment and specifying the most effective track out 
prevention measures. The District concludes that an increase in the 
required frequency of street sweeping is not economically feasible at 
this time because most areas in the South Coast air basin already 
require regular street sweeping and a requirement to conduct more 
frequent street sweeping would achieve only minimal emission 
reductions.
    Based on our evaluation of the information provided in the 2016 
AQMP and additional information obtained during our review of the Plan, 
we agree with the SCAQMD's conclusion that Rule 1186 implements BACM 
for the control of PM2.5 from paved and unpaved roads and 
livestock operations.
Commercial Charbroiling
    SCAQMD Rule 1138 (``Control of Emissions from Restaurant 
Operations''), adopted November 14, 1997, establishes control 
requirements to reduce PM and VOC emissions from ``chain-driven'' 
charbroilers at commercial cooking operations. The rule does not apply 
to ``under-fired'' charbroilers. EPA approved Rule 1138 into the 
California SIP on July 11, 2001.\83\
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    \83\ 66 FR 36170.
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    Under Rule 1138, chain-driven charbroilers that cook more than 875 
pounds of meat per week are required to be equipped and operated with a 
catalytic oxidizer control device that has been tested and certified by 
the Executive Officer to reduce PM and VOC emissions. The District 
compared the requirements of Rule 1138 to several rules implemented in 
other parts of California and in other states that are designed to 
limit PM and/or VOC emissions from commercial charbroilers. Based on 
its review of analogous regulations implemented in these other areas, 
the District concludes that Rule 1138 is generally equivalent to those 
regulations.
    Several times over the past 20 years and most recently in 2009, the 
District considered amending Rule 1138 to regulate PM emissions from 
under-fired charbroilers, but to date the District has not identified 
control measures for under-fired charbroilers that are both 
technologically and economically feasible for implementation in the 
South Coast. Although three other local agencies have adopted control 
requirements that apply to under-fired charbroilers (the Bay Area Air 
Quality Management District, the New York City Department of 
Environmental Protection, and the City of Aspen, Colorado), no 
commercially-available control devices for under-fired charbroilers 
have yet been found to meet these control requirements.\84\ The 2016 
AQMP contains a commitment by the District to adopt a control measure 
in 2018 that requires controls on under-fired charbroilers by 2025. The 
proposed measure is identified in the Plan as BCM-01.\85\
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    \84\ See Technical Support Document for the Proposed Approval of 
South Coast AQMD's Serious Area Plan for the 2006 PM2.5 National 
Ambient Air Quality Standards (Docket Number EPA-R09-OAR-2017-0490), 
at pp. 13-14; see also 2016 AQMP, Appendix IV-A, pp. IV-A-186 to IV-
A-190.
    \85\ See 2016 AQMP, Chapter 4, Table 4-7; Appendix IV-A, pp. IV-
A-186 to IV-A-192 (describing BCM-01); and SCAQMD, Governing Board 
Resolution No. 17-2 (March 3, 2017), at p. 9.
---------------------------------------------------------------------------

    Based on our evaluation of the information provided in the 2016 
AQMP and additional information obtained during our review of the Plan, 
we agree with the SCAQMD's conclusion that Rule 1138 and BCM-01 
together implement BACM for the control of PM2.5 from 
commercial charbroilers.
Consumer Products
    CARB and the SCAQMD both have well-established programs to regulate 
VOC emissions from consumer products used by both household and 
institutional consumers, including detergents; cleaning compounds; 
polishes; floor finishes; cosmetics; personal care products; home, 
lawn, and garden products; disinfectants; sanitizers; aerosol paints; 
and automotive specialty products. Specifically, CARB has adopted three 
regulations that establish VOC and reactivity limits for 129 consumer 
product categories.\86\ The first regulation (Article 1) covers the 
categories of antiperspirants and deodorants. The second regulation 
(Article 2) covers numerous categories and is simply called the 
``General Consumer Products Regulation.'' The third regulation (Article 
3) covers categories of aerosol coatings. The EPA approved amendments 
to these regulations into the California SIP on October 17, 2014.\87\
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    \86\ These regulations are codified in the California Code of 
Regulations, Title 17, Division 3, Chapter 1, Subchapter 8.5--
Consumer Products; Article 2--Consumer Products.
    \87\ 79 FR 62346 (October 17, 2014).
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    The SCAQMD also regulates certain categories of consumer products, 
including architectural coatings, wood products, solvents and 
degreasers, consumer paint thinners, and inks.\88\ For example, South 
Coast's implementation of Rule 1113

[[Page 49882]]

(``Architectural Coatings'') establishes emission limits for paints and 
other architectural coating products that have achieved VOC emission 
reductions in the South Coast area. The EPA approved Rule 1113, as 
amended June 3, 2011, into the California SIP on March 26, 2013.\89\
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    \88\ See, e.g., South Coast Rule 1107, Coating of Metal Parts 
and Products, approved into the SIP on November 24, 2008 (73 FR 
70883); South Coast Rule 1122, Solvent Degreasers, approved into the 
SIP on February 8, 2006 (71 FR 6350); and South Coast Rule 1130, 
Graphic Arts, approved into the SIP on July 14, 2015 (80 FR 40915).
    \89\ 78 FR 18244 (March 26, 2013).
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    Based on our evaluation of the information about these programs in 
the 2016 AQMP, we agree with the State's and District's conclusion that 
these SIP-approved regulations implement BACM for the control of VOCs 
from consumer products.
ii. State Measures for Mobile Sources
    The 2016 AQMP identifies light-duty passenger vehicles, light-duty 
trucks, medium-duty trucks, medium-heavy-duty diesel trucks, heavy-
heavy-duty diesel trucks, and commercial/industrial mobile equipment 
(construction and mining equipment) as key mobile sources of emissions 
of PM2.5 and PM2.5 precursors. CARB describes the 
mobile source control measures that regulate PM2.5 and 
PM2.5 precursor emissions from these sources in Appendix VI-
A, Attachment VI-A-3, and Attachment VI-C-1 of the 2016 AQMP.
    Under the CAA, the EPA is charged with establishing national 
emissions limits for mobile sources. States are generally preempted 
from establishing such limits except for California, which can 
establish these limits subject to EPA waiver or authorization under CAA 
section 209 (referred to herein as ``waiver measures''). Over the 
years, the EPA has issued waivers (for on-road vehicles and engines 
measures) or authorizations (for non-road vehicle and engine measures) 
for many mobile source regulations adopted by CARB. California 
attainment and maintenance plans, including the 2016 PM2.5 
Plan for the South Coast, rely on emissions reductions from 
implementation of the waiver measures through the use of emissions 
models such as EMFAC2014.
    Historically, the EPA has allowed California to take into account 
emissions reductions from CARB regulations for which the EPA has issued 
waiver or authorizations under CAA section 209, notwithstanding the 
fact that these regulations have not been approved as part of the 
California SIP. However, in response to the decision by the United 
States Court of Appeals for the Ninth Circuit (``Ninth Circuit'') in 
Committee for a Better Arvin v. EPA, the EPA has since approved mobile 
source regulations for which waiver authorizations have been issued as 
revisions to the California SIP.\90\
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    \90\ See, e.g., 81 FR 39424 (June 16, 2016), 82 FR 14447 (March 
21, 2017), and 83 FR 23232 (May 18, 2018). See also Committee for a 
Better Arvin, 786 F.3d 1169 (9th Cir. 2015).
---------------------------------------------------------------------------

    Given the need for significant emissions reductions from mobile 
sources to meet the NAAQS in California nonattainment areas, CARB has 
been a leader in the development of stringent control measures for on-
road and off-road mobile sources and fuels.\91\ CARB's mobile source 
program extends beyond regulations that are subject to the waiver or 
authorization process set forth in CAA section 209 to include standards 
and other requirements to control emissions from in-use heavy-duty 
trucks and buses, gasoline and diesel fuel specifications, and many 
other types of mobile sources. Generally, these regulations have been 
submitted and approved as revisions to the California SIP.\92\
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    \91\ California regulations use the term ``off-road'' to refer 
to ``nonroad'' vehicles and engines.
    \92\ See, e.g., the EPA's approval of standards and other 
requirements to control emissions from in-use heavy-duty diesel-
powered trucks, at 77 FR 20308 (April 4, 2012), revisions to the 
California on-road reformulated gasoline and diesel fuel regulations 
at 75 FR 26653 (May 12, 2010), and revisions to the California motor 
vehicle I/M program at 75 FR 38023 (July 1, 2010).
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    In addition to waiver measures, CARB has adopted operational 
requirements for in-use vehicles, rules that limit the amount of 
pollutants allowed in transportation fuels, and incentive programs that 
provide funding to replace or retrofit older, dirtier vehicles and 
equipment with cleaner technologies.\93\
---------------------------------------------------------------------------

    \93\ 2016 AQMP, Appendix VI-A, Attachment VI-A-3, pp. VI-A-108-
109.
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    The EPA previously determined that California's mobile source 
control programs constituted BACM for PM10 purposes in the 
San Joaquin Valley.\94\ Since then, the State has adopted additional 
mobile source control measures including the Advanced Clean Cars (ACC) 
program, heavy-duty vehicle idling rules, revisions to the State's 
vehicle inspection and maintenance (I/M) program, in-use rules for on-
road and non-road diesel vehicles, and emissions standards for non-road 
equipment, farm and cargo handling equipment, and recreational 
vehicles.\95\
---------------------------------------------------------------------------

    \94\ 69 FR 5412 at 5419 (February 4, 2004).
    \95\ 2016 AQMP, Appendix VI-A, Attachment VI-A-3, p. VI-A-103.
---------------------------------------------------------------------------

    CARB's BACM analysis provides a discussion of the measures adopted 
and implemented for each of the source categories identified in Table 
VI-A-6 of the 2016 AQMP that are not under district jurisdiction. We 
discuss each of these mobile source categories below.
Light and Medium-Duty Vehicles
    This category includes light-duty passenger cars, light-duty 
trucks, and medium-duty trucks. The source category's base year 
emissions are approximately 119 tpd NOX, 129 tpd VOC, 1.7 
tpd SO2, 17.1 tpd ammonia, and 8.2 tpd direct 
PM2.5.\96\
---------------------------------------------------------------------------

    \96\ 2016 AQMP, Appendix III, Attachment A.
---------------------------------------------------------------------------

    CARB has a long history of adopting programs for reducing emissions 
from this source category. Light-duty and medium-duty motor vehicles 
are currently subject to California's ``Low-Emission Vehicle III'' (LEV 
III) standards as well as a ``Zero Emission Vehicle'' (ZEV) 
requirement. The LEV III standards are consistent, or harmonized, with 
the subsequently adopted national Tier 3 standards for the same 
vehicles. California's ZEV program, however, does not have a national 
counterpart and results in additional emissions reductions as it phases 
in a requirement that 15% of new light-duty vehicle sales consist of 
ZEV or partial ZEV.\97\ Light and medium-duty vehicles are also 
regulated under California's ACC program. We approved the ACC into the 
SIP on June 16, 2016.\98\ Taken as a whole, California's standards for 
light and medium-duty vehicles are more stringent than the federal 
standards.
---------------------------------------------------------------------------

    \97\ 78 FR 2112 at 2119 (January 9, 2013).
    \98\ 81 FR 39424 (June 16, 2016).
---------------------------------------------------------------------------

    California has also adopted regulations for gasoline fuel 
(California Reformulated Gasoline or ``CaRFG'') that reduce emissions 
from light-duty and medium-duty vehicles. The EPA approved the CaRFG 
regulations into the California SIP on May 12, 2010.\99\ In our action 
proposing to approve CaRFG3, we noted that the EPA had previously 
determined that emissions reductions from CaRFG3 would be equal to or 
greater than the emissions reductions from the corresponding federal 
RFG program.\100\
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    \99\ 75 FR 26653 (May 12, 2010).
    \100\ 74 FR 33196 at 33198 (July 10, 2009).
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Heavy-Duty Vehicles
    This category includes heavy-heavy-duty diesel vehicles, heavy-duty 
gas and diesel trucks, heavy-duty gas and diesel urban buses, school 
buses and motor homes. The emissions from this category are 
approximately 195 tpd NOX, 6.23 tpd direct PM2.5, 
12.47 tpd VOC, 0.29 tpd, SO2, and 0.97 tpd ammonia.\101\
---------------------------------------------------------------------------

    \101\ 2016 AQMP, Appendix III, Attachment A.
---------------------------------------------------------------------------

    California has the most stringent heavy-duty vehicle emissions 
control measures in the nation, including engine standards for diesel 
and gasoline

[[Page 49883]]

vehicles, idling requirements, certification procedures, on-board 
diagnostic requirements, and verification measures for emissions 
control devices. Many of these control measures are subject to the CAA 
waiver process and have also been submitted for inclusion in and 
approved into the SIP.\102\
---------------------------------------------------------------------------

    \102\ See 81 FR 39424 (June 16, 2016), 82 FR 14446 (March 21, 
2017), and 83 FR 23232 (May 18, 2018).
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    California has also adopted many in-use requirements to help reduce 
emissions from the vehicles already on the road, which may remain in 
use for many years. Among the most recently adopted in-use requirements 
are the Truck and Bus Regulation and Drayage Truck Regulation (often 
referred to as the ``Cleaner In-Use Heavy-Duty Trucks Measure''), which 
became effective in 2011 and the EPA approved into the SIP in 
2012.\103\ The Truck and Bus Regulation and Drayage Truck Regulation 
are designed to reduce emissions of diesel PM, NOX, and 
other pollutants from in-use trucks and buses and establish, among 
other things, phased-in PM control requirements from 2014 through 2023 
based on truck engine mode year. These and other regulations applicable 
to heavy-duty diesel trucks (HDDTs) will continue to reduce emissions 
of diesel PM and NOX through the RFP and attainment planning 
years. For instance, model year (MY) 1994 and 1995 HDDT engines must be 
upgraded to meet the 2010 model year truck engine emissions standards 
by 2016, and MY 1996-1999 engines must be upgraded by January 1, 
2020.\104\ The emissions reductions from these rules represent a large 
portion of the NOX emissions reductions upon which the 
Plan's RFP and attainment demonstration rely.
---------------------------------------------------------------------------

    \103\ 77 FR 20308, April 4, 2012.
    \104\ 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 the EPA's final rule approving 
CARB's Truck and Bus Rule. 77 FR 20308 at 20309-20310 (April 4, 
2012).
---------------------------------------------------------------------------

    Finally, California has adopted regulations for diesel fuel that 
further reduce emissions from heavy-duty trucks. The EPA approved these 
diesel fuel regulations into the California SIP on May 12, 2010.\105\
---------------------------------------------------------------------------

    \105\ See 75 FR 26653.
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Off-Road Vehicles and Engines
    This category includes off-road compression ignition (diesel) 
engines and equipment, small spark ignition (gasoline) off-road engines 
and equipment less than 25 horsepower (hp) (e.g., lawn and garden 
equipment), off-road large gasoline engines and equipment greater than 
25 hp (e.g., forklifts, portable generators), and airport ground 
service equipment. The emissions from this category total approximately 
66 tpd NOX, 4 tpd direct PM2.5, 51.5 tpd VOC, 
0.07 tpd SO2, and 0.09 tpd ammonia.\106\
---------------------------------------------------------------------------

    \106\ 2016 AQMP, Appendix III, Attachment A.
---------------------------------------------------------------------------

    As it has done for the on-road categories discussed above, CARB has 
adopted stringent new emissions standards subject to EPA authorization 
under CAA section 209(e) and in-use measures or requirements for this 
source category (e.g., incentives for early introduction of cleaner 
engines and equipment and requirements to limit vehicle idling). CARB 
has been regulating off-road equipment since the 1990s, and its new 
engine standards for off-road vehicles and engines are generally as 
stringent as the corresponding federal standards. For larger off-road 
equipment, which can have a slow turnover rate, CARB adopted an in-use 
off-road regulation in 2007 that requires owners of off-road equipment 
in the construction and other industries to retrofit or replace older 
engines/equipment with newer, cleaner models. The off-road regulation 
imposes idling limitations.\107\ CARB's off-road emissions control 
program also includes comprehensive in-use requirements for legacy 
fleets.\108\
---------------------------------------------------------------------------

    \107\ Id.
    \108\ 2016 AQMP, Appendix VI-A, p. VI-A-104, also Appendix VI-C, 
pp. VI-C-21 to VI-C-22.
---------------------------------------------------------------------------

    Title 13, Section 2449 of the California Code of Regulation (CCR), 
``Regulation for In-Use Off-Road Diesel-Fueled Fleets (Off-Road 
Regulation)'' was adopted by CARB in July 2007 and requires off-road 
diesel vehicle fleets to reduce emissions by meeting NOX and 
PM fleet average standards. A provision of the Off-Road Regulation 
(Title 13, CCR, Section 2449.2) allows air districts to opt-in and 
requires the largest fleets to apply for funding to meet more stringent 
NOX targets. In 2008, SCAQMD developed the Surplus Off-Road 
Opt-In for NOX (SOON) Program. The SOON Program is designed 
to achieve additional NOX reductions beyond those that would 
be obtained from the State's In-Use Off-Road Vehicle Regulation. The 
program provides funding to large fleets for the purchase of 
commercially-available low-emission heavy-duty engines to achieve near-
term reduction of NOX emissions from in-use off-road diesel 
vehicles. Fleets that participate in the SOON Program can apply for 
funding for NOX exhaust retrofits, repowers or equipment 
replacements. We approved the SCAQMD SOON program into the SIP on 
November 21, 2016.\109\
---------------------------------------------------------------------------

    \109\ 81 FR 83154.
---------------------------------------------------------------------------

iii. Local Jurisdiction Transportation Control Measures
    Transportation control measures (TCMs) are, in general, measures 
designed to reduce emissions from on-road motor vehicles through 
reductions in vehicle miles traveled (VMT) or traffic congestion. TCMs 
can reduce PM2.5 emissions in both the on-road motor vehicle 
exhaust and paved road dust source categories by reducing VMT and 
vehicle trips. They can also reduce vehicle exhaust emissions by 
relieving congestion. EPA guidance states that where mobile sources 
contribute significantly to PM2.5 violations, ``the state 
must, at a minimum, address the transportation control measures listed 
in CAA section 108(f) to determine whether such measures are achievable 
in the area considering energy, environmental and economic impacts and 
other costs.'' \110\
---------------------------------------------------------------------------

    \110\ Addendum at 42013.
---------------------------------------------------------------------------

    Appendix IV-C, ``Regional Transportation Strategy and Control 
Measures,'' contains SCAG's BACM analysis for TCMs. Consistent with EPA 
guidance, SCAG addressed the TCMs listed in CAA section 108(f) 
following a four-step process. SCAG first reviewed ongoing 
implementation of TCMs in the South Coast air basin. SCAG also reviewed 
TCMs implemented in all other Moderate and Serious PM2.5 and 
PM10 nonattainment areas throughout the country (e.g., Salt 
Lake City, Utah; Fairbanks, Alaska; and San Joaquin Valley, California) 
and compared them to the TCMs being implemented in the South 
Coast.\111\ SCAG then reviewed the TCMs not being implemented in the 
SCAG region and provided a reasoned justification for any TCMs not 
implemented in the SCAG region.\112\ Finally, SCAG concluded that its 
TCM program provides a BACM level of control.
---------------------------------------------------------------------------

    \111\ See 2016 AQMP, Appendix IV-C, pp. IV-C-38 and IV-C-39, 
Table 8.
    \112\ See 2016 AQMP, Appendix IV-C, pp. IV-C-42 to IV-C-50, 
Table 9.
---------------------------------------------------------------------------

    TCMs in the South Coast air basin fall into three main categories: 
(1) Transit, intermodal facilities, and nonmotorized transportation 
mode facilities (i.e., bike/pedestrian facilities), (2) high occupancy 
vehicle (HOV) lanes, high occupancy toll (HOT) lanes, and pricing 
alternatives, and (3) information-based TCM strategies. Between 2012 
and 2020, SCAG estimates a 23% increase in HOV, HOT and toll lanes, a 
7.4% increase in operation miles of regular transit buses, a 10% 
increase in operation miles of

[[Page 49884]]

rapid transit and express buses, a 38.8% increase in operation miles of 
transit rail, and a 40% increase in Class 1-4 bikeway miles.\113\ TCM 
funding is guaranteed through the timeframe of the 2016 
PM2.5 Plan and beyond, with transportation sales tax 
measures through 2039 and 2040 in the four counties in the South Coast 
air basin.\114\ The county-specific sales tax revenue provides a 
guaranteed funding source for more than 50% of the TCM projects.\115\ 
In addition, SCAG has a standardized program for selecting cost-
effective control measures.
---------------------------------------------------------------------------

    \113\ See 2016 AQMP, Appendix IV-C, p. IV-C-34.
    \114\ Id.
    \115\ See 2016 AQMP, Appendix IV-C, p. IV-C-36.
---------------------------------------------------------------------------

3. The EPA's Evaluation and Conclusion
    We have reviewed the District's determination in the 2016 AQMP that 
its stationary and area source control measures represent BACM for 
PM2.5 and PM2.5 precursors. In our review, we 
also considered our previous evaluations of the District's rules in 
connection with our approval of the SCAQMD's RACT SIP demonstration for 
the 2008 ozone NAAQS.\116\ Based on this review, we believe the 
District's rules provide for the implementation of BACM for stationary 
and area sources of PM2.5 and PM2.5 precursors.
---------------------------------------------------------------------------

    \116\ 82 FR 43850 (September 20, 2017).
---------------------------------------------------------------------------

    With respect to mobile sources, we recognize that CARB's current 
program addresses the full range of mobile sources in the South Coast 
through regulatory programs for both new and in-use vehicles. With 
respect to transportation controls, we note that SCAG has adopted a 
program to fund cost-effective TCMs. Overall, we believe that the 
programs developed and administered by CARB and SCAG provide for the 
implementation of BACM for PM2.5 and PM2.5 
precursors in the South Coast nonattainment area.
    For these reasons, we propose to find that the 2016 
PM2.5 Plan provides for the implementation of BACM for all 
sources of direct PM2.5 and PM2.5 precursors as 
expeditiously as practicable, for purposes of the 2006 PM2.5 
NAAQS in the South Coast area, in accordance with the requirements of 
CAA section 189(b)(1)(B) and 40 CFR 51.1010.

D. Attainment Demonstration and Modeling

    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 a 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, and 
the control strategy in the Plan for attaining the 24-hour 
PM2.5 NAAQS by the most expeditious date practicable.
Evaluation of Air Quality Modeling Approach and Results
    The EPA's PM2.5 modeling guidance \117\ (``Modeling 
Guidance'' and ``Modeling Guidance Update'') recommends that a 
photochemical model, such as CAMx \118\ 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.\119\ 
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. Because each chemical 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 design value must be split into its species 
components. The Modeling Guidance provides additional detail on the 
recommended approach.\120\
---------------------------------------------------------------------------

    \117\ ``Draft Modeling Guidance for Demonstrating Attainment of 
Air Quality Goals for Ozone, PM2.5, and Regional Haze'' 
Memorandum from Richard Wayland, Air Quality Assessment Division, 
OAQPS, EPA to Regional Air Program Managers, EPA, December 3, 2014 
(``Modeling Guidance''), ``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'').
    \118\ CAMx is a multi-scale photochemical modeling system for 
gas and particulate air pollution.
    \119\ In this section, we use the terms ``base case,'' ``base 
year'' or ``baseline,'' and ``future year'' as described in section 
2.3 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.''
    \120\ Modeling Guidance Update at 43 ff.
---------------------------------------------------------------------------

24-Hour PM2.5 Modeling Approach
    The CMAQ simulations were conducted for each day in the 2012 base 
year.\121\ A set of species-specific RRFs was generated for the 2019 
future year simulation from the top 10% of modeled PM2.5 
days. RRFs were generated for the ammonium ion, nitrate ion, sulfate 
ion, organic carbon, elemental carbon, sea salt, and a combined 
grouping of other primary PM2.5 material. Future year 
concentrations of each of the seven component species were calculated 
by applying the model-generated quarterly RRFs to the speciated 24-hour 
PM2.5 data for each of the five years used in the design 
value calculation.\122\ The speciation fractions used to generate 24-
hour speciated PM2.5 values were determined from the 
``high'' days.\123\ A weighted average of the resulting future year 
98th percentile concentrations for each of the five years was used to 
calculate future design values for the attainment demonstration.\124\ 
Future year PM2.5 24-hour average design values were 
projected for 2019, the Serious area attainment deadline for the 2006 
standard of 35 [mu]g/m\3\.
---------------------------------------------------------------------------

    \121\ CMAQ Version 5.0.2
    \122\ The design value is based on a weighted average of data 
from 2010 to 2014.
    \123\ Particle bound water was determined using the EPA's 
regression model approximation of the Aerosol Inorganics Model (AIM) 
based on simulated concentrations of the ammonium, nitrate and 
sulfate ions (EPA, 2006). A blank mass of 0.5 [mu]g/m\3\ was added 
to each base and future year simulation.
    \124\ The 32 days in each year (8 per quarter) were then 
reranked based on the sum of all predicted PM species to establish a 
new 98th percentile concentration. The 98th percentile value was 
determined based on the FRM sampling frequency. All the SASS sites 
except Fontana have a daily FRM sampling, which gives the 8th 
highest day as the 98th percentile. Fontana has every-three-day 
sampling, thus the 3rd highest day becomes the 98th percentile.
---------------------------------------------------------------------------

Future Air Quality
    A simulation of 2019 baseline emissions (no additional controls) 
was conducted to assess future 24-hour PM2.5 levels in the 
South Coast air basin. The simulation used the projected emissions from 
2012, which reflect all adopted control measures that will be

[[Page 49885]]

implemented by December 31, 2019. Simulation of the 2019 baseline 
emissions indicates that the South Coast air basin will attain the 
federal 24-hour PM2.5 standard in 2019 without additional 
controls. The projected 2019 design value is 32.1 [mu]g/m\3\ at Mira 
Loma, the highest site in the South Coast air basin.
    Table 2 shows future 24-hour PM2.5 air quality 
projections at the South Coast air basin design site (Mira Loma) and 
the four other PM2.5 monitoring sites equipped with 
comprehensive particulate species characterization. Shown in the table 
are the base year design values for 2012 along with projections for 
2019. All of the sites are projected to meet the 24-hour 
PM2.5 standard by 2019 without additional reductions beyond 
already adopted control measures.

    Table 2--Future 24-Hour PM2.5 Air Quality Projections at Selected
              Monitoring Sites in the South Coast Air Basin
------------------------------------------------------------------------
                                                         24-hour PM 2.5
                                      24-hour PM 2.5    98th percentile
                                     98th percentile     concentration
                                      concentration        total mass
     Monitoring site location         total mass for     projected for
                                     base year, 2012     2019 ([mu]g/m
                                      ([mu]g/m \3\)           \3\)
 
------------------------------------------------------------------------
Anaheim...........................              25.82              23.46
Fontana...........................              32.74              28.01
Los Angeles.......................              30.52              27.60
Mira Loma.........................              36.52              31.36
Rubidoux..........................              33.16              28.27
------------------------------------------------------------------------

    The EPA's regulations require that monitoring data for comparison 
to the NAAQS be collected using specific equipment and procedures to 
ensure accuracy and reliability.\125\ For each NAAQS, the default 
monitoring equipment and the required procedures for operating it are 
termed the Federal Reference Method (FRM); an alternative approach, 
termed a Federal Equivalent Method may also be used if it is 
demonstrated to give results comparable to an FRM monitor.
---------------------------------------------------------------------------

    \125\ 40 CFR parts 53 and 58.
---------------------------------------------------------------------------

Evaluation of Control Strategy
    The attainment control strategy in the 2016 PM2.5 Plan 
consists of state and district baseline measures that continue to 
achieve emission reductions between the Plan's base year of 2012 and 
the attainment year of 2019. With respect to baseline measures for 
stationary and area sources, the District identified the District rules 
and their projected emission levels in Appendix VI, section VI-C of the 
2016 AQMP and described each of the District measures that contribute 
to RFP and attainment.\126\ The District control measures listed in 
this section of the Plan have been approved into the California 
SIP.\127\
---------------------------------------------------------------------------

    \126\ See 2016 AQMP, Appendix VI, Table VI-C-4, p. VI-C-8.
    \127\ See EPA Region 9's website for information on district 
control measures that have been approved into the California SIP, 
available at: https://www.epa.gov/sips-ca/epa-approved-south-coast-air-district-regulations-california-sip.
---------------------------------------------------------------------------

    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 Chapter 3 and Appendix III of 
the 2016 AQMP.\128\
---------------------------------------------------------------------------

    \128\ 2016 AQMP, pages III-2-73 and Attachment D-1 to Appendix 
III.
---------------------------------------------------------------------------

    Table 3 below summarizes the emission reductions needed in the 
South Coast to attain the 2006 24-hour PM2.5 NAAQS by the 
end of 2019.

  Table 3--Summary of Direct PM2.5 and Precursor Emission Reductions Needed for the 2006 PM2.5 NAAQS Attainment
                                                  Demonstration
----------------------------------------------------------------------------------------------------------------
                                           2006 24-hour standard attainment by 2019 (tpd annual average)
                                 -------------------------------------------------------------------------------
                                       PM2.5            NOX             SO2             VOC             NH3
----------------------------------------------------------------------------------------------------------------
A. 2012 emissions inventory.....              66             540              18             470              81
B. 2019 baseline emissions                    64             353              17             376              74
 inventory......................
C. 2019 controlled emissions                  64             353              17             376              74
 inventory......................
D. Total emission reductions                   2             187               1              94               7
 needed by attainment year (A -
 C).............................
----------------------------------------------------------------------------------------------------------------
Source: 2016 PM2.5 Plan, Chapter 3, and Appendix VI, Table VI-C-5.

    The Plan identifies several district and state measures that will 
achieve emission reductions and contribute to expeditious attainment of 
the 2006 PM2.5 NAAQS. These are described in the sections of 
this proposed rulemaking on BACM and RFP.
    In sum, the attainment demonstration in the 2016 PM2.5 
Plan relies on numerous state and district baseline regulations that 
collectively are projected to achieve emission reductions sufficient 
for the South Coast area to attain the 2006 24-hour PM2.5 
standard by the end of 2019.
EPA's Evaluation and Proposed Action
    As discussed above, the 2016 PM2.5 Plan's air quality 
modeling demonstrates that the South Coast will attain the 2006 24-hour 
PM2.5 standard of 35 [micro]g/m\3\ by December 31, 2019. 
This demonstration is based on expeditious implementation of the 
state's and district's BACM control strategy for

[[Page 49886]]

stationary, area, and mobile sources in the 2016 PM2.5 Plan 
and ongoing reductions from state and local control measures already 
approved into the SIP. Based on our evaluation, we propose to determine 
that the 2016 PM2.5 Plan provides for attainment of the 2006 
24-hour PM2.5 standards by the most expeditious date 
practicable, consistent with the requirements of CAA section 
189(b)(1)(A) and 40 CFR 51.1011(b).

E. Reasonable Further Progress and Quantitative Milestones

1. Requirements for Reasonable Further Progress and Quantitative 
Milestones
    Section 172(c)(2) of the Act states that all nonattainment area 
plans shall require RFP. In addition, CAA section 189(c) requires that 
all PM2.5 nonattainment area SIPs contain quantitative 
milestones to be achieved every three years until the area is 
redesignated to attainment and which demonstrate RFP, as defined in CAA 
section 171(1). Section 171(1) of the Act defines RFP as the annual 
incremental reductions in emissions of the relevant air pollutant as 
are required by part D, title I of the Act or as may reasonably be 
required by the Administrator for the purpose of ensuring attainment of 
the 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 
emissions reductions sufficient generally to maintain at least linear 
progress toward attainment by the applicable deadline.\129\ 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:
---------------------------------------------------------------------------

    \129\ 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.\130\
---------------------------------------------------------------------------

    \130\ 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 states that RFP may be 
met by ``adherence to an ambitious compliance schedule'' that is likely 
to periodically yield significant reductions of direct PM2.5 
or a PM2.5 precursor.\131\
---------------------------------------------------------------------------

    \131\ Id.
---------------------------------------------------------------------------

    Plans for PM2.5 nonattainment areas should include 
detailed schedules for compliance with emission control measures in the 
area and provide corresponding annual emission reductions to be 
achieved by each milestone in the schedule.\132\ In reviewing an 
attainment plan under subpart 4, the EPA considers whether the annual 
incremental emissions 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 control measures and may implement measures that are more 
effective at reducing PM2.5 earlier to provide greater 
public health benefits.\133\
---------------------------------------------------------------------------

    \132\ Id. at 42016.
    \133\ Id.
---------------------------------------------------------------------------

    The PM2.5 SIP Requirements Rule establishes specific 
regulatory requirements for purposes of satisfying the Act's RFP 
requirements and provides related guidance in the preamble to the rule. 
Specifically, under the PM2.5 SIP Requirements Rule, each 
PM2.5 attainment plan must contain an RFP plan that 
includes, at minimum, the following four components: (1) An 
implementation schedule for control measures; (2) RFP projected 
emissions for direct PM2.5 and all PM2.5 plan 
precursors for each applicable milestone year, based on the anticipated 
control measure implementation schedule; (3) a demonstration that the 
control strategy and implementation schedule will achieve reasonable 
progress toward attainment between the base year and the attainment 
year; and (4) a demonstration that by the end of the calendar year for 
each milestone date for the area, pollutant emissions will be at levels 
that reflect either generally linear progress or stepwise progress in 
reducing emissions on an annual basis between the base year and the 
attainment year.\134\
---------------------------------------------------------------------------

    \134\ 40 CFR 51.1012(a).
---------------------------------------------------------------------------

    The preamble to the PM2.5 SIP Requirements Rule provides 
that emissions from one or more PM2.5 plan precursors may 
increase over the attainment planning period, provided the state 
demonstrates that reductions of direct PM2.5 combined with 
the aggregate reductions of PM2.5 plan precursors support 
expeditious attainment of the applicable PM2.5 NAAQS. This 
approach recognizes the fact that different precursors have different 
impacts on PM2.5 concentrations depending upon the 
atmospheric chemistry specific to each area.\135\
---------------------------------------------------------------------------

    \135\ 81 FR 58010 at 58057 (August 24, 2016).
---------------------------------------------------------------------------

    Section 189(c) of the Act requires that PM2.5 attainment 
plans include quantitative milestones that demonstrate RFP. The purpose 
of the quantitative milestones is to allow periodic evaluation of the 
area's progress towards attainment of the PM2.5 NAAQS 
consistent with RFP requirements. 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 should also 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 
emissions controls in the attainment plan and the requirement to 
quantify those required emissions reductions. The CAA also requires 
states to submit, within 90 days after each milestone date, milestone 
reports that include technical support sufficient to document 
completion statistics for appropriate milestones, e.g., calculations 
and any assumptions made concerning emission reductions to date.\136\
---------------------------------------------------------------------------

    \136\ Addendum 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, the EPA interpreted the CAA to 
require that the starting point for the first three-year period be the 
due

[[Page 49887]]

date for the Moderate area plan submission.\137\ In keeping with this 
historical approach, the EPA established December 31, 2014, as the 
starting point for the first 3-year period under CAA section 189(c) for 
the 2006 PM2.5 standards in the South Coast. 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 2006 PM2.5 NAAQS in the 
South Coast area.\138\ Thus, December 31, 2017 and December 31, 2020, 
are 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 for the 2006 
PM2.5 NAAQS.
---------------------------------------------------------------------------

    \137\ General Preamble at 13539, Addendum at 42016.
    \138\ 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 the 
EPA had previously taken under CAA section 110(k) on a SIP for a 
PM2.5 nonattainment area, the 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.
---------------------------------------------------------------------------

    The PM2.5 SIP Requirements Rule also requires that 
Serious area attainment plans contain one additional quantitative 
milestone to be met in the three-year period following the Serious area 
attainment date.\139\ If the area fails to attain, this additional 
milestone provides the EPA with the tools necessary to monitor the 
area's continued progress toward attainment while the state develops a 
new attainment plan under CAA section 189(d).
---------------------------------------------------------------------------

    \139\ 40 CFR 51.1013(a)(4).
---------------------------------------------------------------------------

2. RFP Plan and Quantitative Milestones in the 2016 PM2.5 
Plan
    The RFP plan and quantitative milestones are discussed in Appendix 
VI, section VI-C (pp. VI-C-5 to VI-C-8) of the 2016 AQMP. The Plan 
estimates that emissions of direct PM2.5, NOX, 
VOC, SO2 and ammonia will generally decline from the 2012 
base year to 2019 and states that emissions of each of these pollutants 
will remain below the levels needed to show ``generally linear 
progress'' from 2012 to 2019, the year that the Plan projects to be the 
earliest practicable attainment date for the 2006 PM2.5 
NAAQS.\140\ The Plan's emissions inventory shows that direct 
PM2.5, NOX, VOC, SO2 and ammonia are 
emitted by a large number and range of sources in the South Coast and 
that the emission reductions needed for each of these pollutants are 
inventory wide.\141\ Table VI-C-4 of the 2016 AQMP contains an 
implementation schedule for District control measures and Table VI-C-3 
of the 2016 AQMP (reproduced in Table 4 below) contains RFP projected 
emissions for each quantitative milestone year and the attainment year. 
Based on these analyses, the District concludes that its adopted 
control strategy will achieve, for each pollutant, projected emission 
levels at or below the RFP, quantitative milestone, and attainment year 
target emission levels (see Table 5 below).\142\
---------------------------------------------------------------------------

    \140\ 2016 AQMP, Appendix VI-C, p. VI-C-7, Tables VI-C-3 and VI-
C-3A.
    \141\ 2016 AQMP, Chapter 4 and Appendices IV-A, VI-B and VI-C.
    \142\ 2016 AQMP, Appendix VI-C, p. VI-C-6.

                     Table 4--24-Hour PM2.5 Baseline Emissions for Base and Milestone Years
                                              [Annual average tpd]
----------------------------------------------------------------------------------------------------------------
                                                                2017                                  2020
              Pollutant                      2012          (Quantitative     2019 (Attainment    (Quantitative
                                                             milestone)         deadline)          milestone)
----------------------------------------------------------------------------------------------------------------
PM2.5...............................               66.4               63.8               63.9               63.9
NOX.................................                540                398                353                330
SO2.................................               18.4               17.1               16.6               16.7
VOC.................................                470                392                376                370
NH3.................................               81.1               75.5               74.0               73.3
----------------------------------------------------------------------------------------------------------------
Source: 2016 AQMP, Appendix VI-C, Table VI-C-3.

                               Table 5--Summary of 24-Hour PM2.5 RFP Calculations
                                              [Annual average tpd]
----------------------------------------------------------------------------------------------------------------
     Row       Calculation step        PM2.5            NOX             SO2             VOC             NH3
----------------------------------------------------------------------------------------------------------------
1...........  2012 base year                66.4             540            18.4             470            81.1
               emissions.
2...........  Annual percent                0.55             4.9             1.4             2.9             1.2
               change needed to
               show linear
               progress (%).
3...........  2017 Target Needed            64.6             406            17.1             403            76.0
               to show linear
               progress (tpd).
4...........  2017 Baseline                 63.8             398            17.1             392            75.5
               emissions (tpd).
5...........  Projected                        0               0               0               0               0
               shortfall (tpd).
6...........  Surplus in 2017               0.85             8.6            0.05            10.4            0.48
               (tpd).
7...........  Emissions                     0.36            26.7            0.25            13.5             1.0
               Equivalent to 1
               Year's Worth of
               RFP.
8...........  2019 Baseline                 63.9             353            16.6             376            74.0
               Emissions (tpd).
----------------------------------------------------------------------------------------------------------------
Source: 2016 AQMP, Appendix VI-C, Table VI-C-3A.

    The 2016 PM2.5 Plan documents the State's conclusion 
that all BACM and BACT for these pollutants are being implemented as 
expeditiously as practicable and identifies projected levels of direct 
PM2.5, NOX, VOC, ammonia, and SO2 
emissions in 2017 and 2019 that reflect full implementation of the 
state, district,

[[Page 49888]]

and SCAG's BACM/BACT control strategy for these pollutants.\143\ The 
BACM control strategy that provides the basis for these emissions 
projections is described in Chapter 4, Appendix IV, and Appendix VI of 
the 2016 AQMP.
---------------------------------------------------------------------------

    \143\ 2016 AQMP, Appendix VI-C, pp. VI-C-5 to VI-C-11; see also 
evaluation of BACM/BACT in section V.C of this proposed rule.
---------------------------------------------------------------------------

Direct PM2.5
    The District has several stationary and area source rules that are 
projected to contribute to RFP and attainment of the PM2.5 
standards.\144\ For example, Rule 444 (Open Burning) achieved 
reductions of direct PM2.5 from the base year of 2012 to the 
2017 RFP year. In addition, Rule 445 (Wood-Burning Devices) was amended 
in 2013 by lowering the mandatory winter burning curtailment program 
threshold for residential wood burning and extending the curtailment to 
the entire South Coast air basin, thereby further limiting emissions 
from one of the largest combustion sources of direct PM2.5 
in the South Coast nonattainment area.\145\ These rule amendments 
provide part of the incremental emission reductions of direct 
PM2.5 from the 2012 base year to the 2017 RFP milestone 
year.\146\ Measures to control sources of direct PM2.5 are 
also presented in the Plan's BACM analyses and reflected in the Plan's 
baseline emission projections.
---------------------------------------------------------------------------

    \144\ 2016 AQMP, Appendix VI-A, p. VI-A-34.
    \145\ 2016 AQMP, Appendix III; see also 78 FR 59249 (September 
26, 2013).
    \146\ 2016 AQMP, Appendix VI-C, p. VI-C-1, Table VI-C-4.
---------------------------------------------------------------------------

    The Plan highlights on-road and other mobile source control 
measures as the primary means for achieving direct PM2.5 
emission reductions. CARB's implementation of the Truck and Bus 
Regulation (referred to in the Plan as the ``On-Road Heavy-Duty Diesel 
Vehicles (In-Use) Regulation'') achieved PM2.5 emissions 
reductions beginning in 2012.\147\ Lighter trucks and buses were 
required to replace 1995 and older engines with a 2010 MY by 2015. The 
2010 MY engines include particulate filters. CARB's LEV II program 
includes particulate matter emissions limits by MY for 2016, and the 
LEV III program has stricter emission limits for 2017 and beyond. For 
off-road vehicles, CARB adopted the In-Use Off Road Diesel-Fueled 
Fleets Regulation (``Off-Road Regulation'') in 2007. The Off-Road 
Regulation requires owners to replace older vehicles or engines with 
newer, cleaner models to either (1) retire older vehicles or reduce 
their use, or (2) to apply retrofit exhaust controls. Off-road fleets 
are required to meet increasingly strict fleet average indices over 
time.\148\ These indices reflect a fleet's overall emissions rate of PM 
and NOX for model year and horsepower combinations. Fleets 
were also banned from adding Tier 0 off-road engines as of January 1, 
2014.\149\ CARB implemented a similar ban on Tier 1 engines between 
January 1, 2014 (large fleets) and January 1, 2016 (small fleets).
---------------------------------------------------------------------------

    \147\ The State's quantitative milestone report for the 2017 
milestone indicates that the requirement for heavier trucks to 
install diesel particulate filters was fully implemented by 2016. 
See SCAQMD, ``2017 Quantitative Milestone Report for 2006 24-hour 
PM2.5 National Ambient Air Quality Standard,'' March 2018 
(``2017 QM Report''), p. 11.
    \148\ A fleet average index is an indicator of a fleet's overall 
emissions rate of particulate matter and NOx based on the horsepower 
and model year of each engine in the fleet.
    \149\ Tier 0 engines meet 1995 to 1999 emission standards, 
depending on engine size and horsepower. See https://www.assocpower.com/eqdata/tech/US-EPA-Tier-Chart_1995-2004.php.
---------------------------------------------------------------------------

Nitrogen Oxides
    The District regulates numerous NOX emission sources 
such as residential space and water heating devices, stationary 
internal combustion engines, and various sizes of boilers, steam 
generators, and process heaters used in industrial settings. The 2016 
AQMP identifies the following South Coast regulations as measures that 
achieve ongoing NOX reductions with compliance dates during 
the RFP and attainment years of the Plan: Rule 1111 (Reductions of 
NOX from Natural Gas-Fired, Fan-Type Central Furnaces), Rule 
1110.2 (Emissions from Gaseous- and Liquid-Fueled Engines), Rule 1121 
(Control of Nitrogen Oxides from Residential-Type, Natural Gas-Fired 
Water Heaters), Rule 1146 (Emission of Oxides of Nitrogen from 
Industrial, Institutional, Commercial Boilers, Steam Generators, and 
Process Heaters), Rule 1146.1 (Emission of Oxides of Nitrogen from 
Small Industrial, Institutional, Commercial Boilers, Steam Generators, 
and Process Heaters), Rule 1146.2 (Emission of Oxides of Nitrogen from 
Large Water Heaters and Small Boilers and Process Heaters), and Rule 
1147 (NOX Reductions from Miscellaneous Sources).\150\ \151\
---------------------------------------------------------------------------

    \150\ 2016 AQMP, Appendix VI-C, Table VI-C-4 and p. VI-C-8.
    \151\ Rule 1111 was mistakenly listed as Rule 1110 in the 2016 
AQMP, Appendix VI, Table VI-C-4. See 2017 QM Report at p. 6, 
footnote 1.
---------------------------------------------------------------------------

    For on-road and non-road mobile sources, which represent the 
largest sources of NOX emissions in the nonattainment area, 
the 2016 AQMP lists numerous CARB regulations and discusses the key 
regulations that limit emissions of direct PM2.5 as well as 
NOX, VOC, SO2 and ammonia from these 
sources.\152\ For example, the regulations that apply to the three 
largest sources of NOX in the South Coast--heavy-duty diesel 
trucks, light- and medium-duty passenger vehicles, and off-road 
equipment--are discussed in the 2016 AQMP at Appendix VI-C, Attachment 
VI-C-1, ``California Existing Mobile Source Control Program,'' and 
CARB's emission projections for these sources are presented in the 
Plan's emissions inventory.\153\ The Plan also shows that 
NOX emission levels in each milestone year and the 
attainment year are projected to be well below the levels needed to 
show generally linear progress toward attainment.
---------------------------------------------------------------------------

    \152\ 2016 AQMP, Appendix IV-C, Attachment VI-C-1.
    \153\ 2016 AQMP, Appendix IV-C, Attachment VI-C-1, pp. VI-C-19-
21.
---------------------------------------------------------------------------

    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.\154\ For example, MY 1994 and 1995 heavy-duty diesel truck 
engines were required to be upgraded to meet the 2010 MY truck engine 
emission standards by 2016, and MY 1996-1999 engines must be upgraded 
by January 1, 2020.\155\ The emission reductions from these rules 
represent the largest portion of the NOX emission reductions 
upon which the 2016 PM2.5 Plan's attainment and RFP 
demonstrations rely.\156\ Emission reductions between 2012 and 2017 
were achieved through the requirements for particulate filters and 
cleaner engine standards.
---------------------------------------------------------------------------

    \154\ 2016 AQMP, Appendix IV-C, p. VI-C-20.
    \155\ 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 77 FR 20308 at 20309-20310 
(April 4, 2012) (final rule approving CARB's Truck and Bus Rule into 
California SIP).
    \156\ 2016 AQMP, Appendix III, Attachment B.
---------------------------------------------------------------------------

    California also has the authority under the CAA to regulate light- 
and medium-duty vehicle engines. A key control program for these 
vehicles is the ACC program.\157\ The ACC program implements a variety 
of regulations including the LEV III program, with criteria pollutant 
emission limits for non-methane organic gases (NMOG) \158\

[[Page 49889]]

and NOX as well as particulate matter, which phased in 
starting in 2014 and continues through the RFP year of 2017 and beyond.
---------------------------------------------------------------------------

    \157\ See 81 FR 39424, June 16, 2016.
    \158\ NMOG means the combination of organic gases other than 
methane as calculated in 40 CFR 1066.635. Note that for this part, 
the organic gases are summed on a mass basis without any adjustment 
for photochemical reactivity.
---------------------------------------------------------------------------

    CARB's Cleaner In-Use Off-road Equipment regulation was first 
approved in 2007 to reduce PM2.5 and NOX 
emissions from in-use off-road heavy-duty diesel vehicles in California 
such as those used in construction, mining, and industrial operations. 
The regulation reduces emissions of PM2.5 and NOX 
by targeting the existing fleet and imposing idling limits, 
restrictions on use of older vehicles, and requirements to retrofit or 
replace the oldest engines. For example, Tier 0 engines could not be 
added to fleets after January 1, 2014, and Tier 1 engines could not be 
added after January 1, 2016. The regulation is phased in between 
January 1, 2014 and January 1, 2019.\159\
---------------------------------------------------------------------------

    \159\ 2016 AQMP, Appendix VI-C, Attachment VI-C-1, p. VI-C-23 
and VI-C-24.
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Volatile Organic Compounds
    As with other precursors, the District regulates stationary and 
area sources of VOC, and CARB is largely responsible for both on-road 
and off-road mobile sources. The 2016 AQMP highlights three stationary 
source VOC rules that contribute to RFP: Rule 1114 (Petroleum Refinery 
Coking Operations), Rule 1177 (Liquified Petroleum Gas Transfer and 
Dispensing), and Rule 1113 (Architectural Coatings).\160\
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    \160\ The District projects that revisions to Rule 1113 that it 
adopted after submitting the 2016 AQMP are projected to result in an 
additional 0.88 tpd of VOC reductions by 2019. See 2017 QM Report, 
p. 8.
---------------------------------------------------------------------------

    As with NOX, the majority of VOC emissions reductions 
that occur between the base year of 2012 and the 2017 RFP year come 
from on-road mobile sources and other mobile sources that are under the 
State's jurisdiction. CARB highlights its ACC program, which reduces 
emission from light- and medium-duty vehicles. The ACC program has a 
combined NMOG plus NOx fleet average requirement that began in 2014.
Ammonia
    With respect to ammonia, the Plan states that, while both 
NOX and ammonia participate in forming ammonium nitrate 
(i.e., secondary PM2.5), NOX emission reductions 
are more effective at reducing ambient PM2.5 than ammonia 
reductions.\161\ Control measures for ammonia sources are described in 
Appendix VI of the Plan. For example, South Coast Rules 223 and 1127, 
which regulate confined animal facilities and manure waste from these 
facilities, control ammonia, as do the District's composting measures 
(i.e., Rules 1133, 1133.1, 1133.2 and 1133.3). These rules and the 
methods they use to control ammonia emissions are discussed at length 
in Appendix VI-B of the 2016 AQMP, and their emission projections are 
presented collectively under farming operations (for confined animal 
feeding operations and manure) or waste disposal (for composting 
categories) in the Plan's emissions inventory.\162\ We discuss our 
evaluation of these rules for purposes of satisfying BACM requirements 
in section V.C of this proposed rule.
---------------------------------------------------------------------------

    \161\ 2016 AQMP, Appendix V, p. V-6-61.
    \162\ 2016 AQMP, Appendix IV-A, p. IV-A-98-103.
---------------------------------------------------------------------------

    The District ascribes the reductions in ammonia during the period 
from 2012 to 2017 to decreases in farming operations in the South Coast 
air basin, as well as reductions in emissions from mobile sources 
largely achieved by state regulations for on-road motor vehicles.
Sulfur Dioxide
    Reductions of SO2 in the South Coast nonattainment area 
during the period from 2012 to 2017 were mainly from mobile source 
reductions. The majority of the SO2 reductions come from 
non-road mobile sources, primarily reductions from state regulation of 
ocean-going vessels.
Quantitative Milestones
    The 2016 AQMP identifies a milestone date of December 31, 2017, 
which is the date 3 years after December 31, 2014, and a second 
milestone date of December 31, 2020, which is the milestone date that 
falls within 3 years after the applicable attainment date (December 31, 
2019). The 2016 AQMP also identifies target RFP emissions levels for 
direct PM2.5, NOX, VOC, NH3, and 
SO2 for the 2017 milestone year, the 2019 attainment year, 
and the 2020 post-attainment year milestone, and adopted control 
measures to be implemented by each of these years in accordance with 
the control strategy in the Plan.\163\
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    \163\ 2016 AQMP, Appendix VI-C, pp. VI-C-6 and VI-C-7.
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3. Evaluation and Proposed Actions
    The 2016 PM2.5 Plan describes the control measures for 
direct PM2.5, NOX, SO2, VOC and 
ammonia implemented during each year of the attainment plan and 
demonstrates that these measures, which provide the bases for the 
emissions projections in the RFP plan, are being implemented as 
expeditiously as practicable. Additionally, the Plan contains projected 
RFP emission levels for direct PM2.5 and all 
PM2.5 precursors for the 2017 and 2020 milestone years and 
for the 2019 attainment year, based on the anticipated implementation 
schedule for the attainment control strategy. The Plan also 
demonstrates that the control strategy will achieve RFP toward 
attainment between the 2012 base year and the 2019 attainment year. 
Finally, the 2016 PM2.5 Plan demonstrates that, by the end 
of the calendar year for each milestone date for the area, emissions of 
direct PM2.5 and all PM2.5 precursors will be 
reduced at rates representing generally linear progress toward 
attainment. We agree with the State and District's conclusion that 
generally linear progress is an appropriate measure of RFP for the 2006 
PM2.5 NAAQS in the South Coast area given that 
PM2.5 and its precursors are emitted by a large number and 
range of sources in the South Coast, the emission reductions needed for 
these pollutants are inventory wide,\164\ and secondary particulates 
contribute significantly to ambient PM2.5 levels in the 
South Coast area.\165\
---------------------------------------------------------------------------

    \164\ See generally 2016 AQMP, Appendix IV-A and B and Appendix 
VI-A.
    \165\ See 2016 AQMP, Appendix V, p. V-6-61.
---------------------------------------------------------------------------

    Accordingly, we propose to determine that the 2016 PM2.5 
Plan requires the annual incremental reductions in emissions of direct 
PM2.5 and PM2.5 precursors that are necessary for 
ensuring attainment of the 2006 24-hour PM2.5 NAAQS by 
December 31, 2019, in accordance with the requirements of CAA sections 
171(1) and 172(c)(2) and 40 CFR 51.1012.
    Additionally, the 2016 PM2.5 Plan identifies milestone 
dates that are consistent with the requirements of 40 CFR 51.1013(a)(4) 
and target emissions levels for direct PM2.5 and all 
PM2.5 precursors to be achieved by these milestone dates 
through implementation of the attainment control strategy. These target 
emission levels and associated control requirements provide for 
objective evaluation of the area's progress towards attainment of the 
2006 PM2.5 NAAQS. We propose to determine that these 
quantitative milestones satisfy the requirements of CAA section 189(c) 
and 40 CFR 51.1013.
    On April 2, 2018, CARB submitted the ``2017 Quantitative Milestone 
Report for the 2006 24-Hour PM2.5 National Ambient Air 
Quality Standards (March 2018)'' (``2017 QM Report'') to the EPA.\166\ 
The 2017 QM report includes a

[[Page 49890]]

certification from the Governor's designee that the 2017 quantitative 
milestones for the South Coast PM2.5 nonattainment area have 
been achieved and a demonstration that the adopted control strategy has 
been fully implemented. The 2017 QM Report also contains a 
demonstration of how the emissions reductions achieved to date compare 
to those required or scheduled to meet RFP. The State and District 
conclude in the 2017 QM Report that the South Coast area is on track to 
attain the 2006 p.m.2.5 NAAQS by the projected attainment 
date for the area, which is December 31, 2019. On September 7, 2018, 
the EPA determined that the South Coast 2017 QM Report was 
adequate.\167\
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    \166\ Letter from Richard W. Corey, Executive Officer, CARB, to 
Alexis Strauss, Acting Regional Administrator, EPA Region IX, with 
attachment, April 2, 2018.
    \167\ Letter from Andrew R. Wheeler EPA, Acting Administrator, 
to Richard W. Corey, Executive Officer, CARB, regarding 2017 
Quantitative Milestone Report for 2006 24-hour PM2.5 
National Ambient Air Quality Standards, September 7, 2018.
---------------------------------------------------------------------------

F. Contingency Measures

1. Requirements for Contingency Measures
    Under CAA section 172(c)(9), each SIP for a nonattainment area must 
include contingency measures to be implemented if an area fails to meet 
RFP (``RFP contingency measures'') or fails to attain the NAAQS by the 
applicable attainment date (``attainment contingency measures''). Under 
the PM2.5 SIP Requirements Rule, PM2.5 attainment 
plans must include contingency measures to be implemented following a 
determination by the EPA that the state has failed: (1) To meet any RFP 
requirement in the approved SIP, (2) to meet any quantitative milestone 
in the approved SIP, (3) to submit a required quantitative milestone 
report, or (4) to attain the applicable PM2.5 NAAQS by the 
applicable attainment date. Contingency measures must be fully adopted 
rules or control measures that are ready to be implemented quickly upon 
failure to meet RFP or failure of the area to meet the relevant NAAQS 
by the applicable attainment date.
    The purpose of contingency measures is to continue progress in 
reducing emissions while a state revises its SIP to meet the missed RFP 
requirement or to correct continuing nonattainment. Neither the CAA nor 
the EPA's implementing regulations establish a specific level of 
emissions reductions that implementation of contingency measures must 
achieve, but the EPA has taken the position that contingency measures 
should provide for emissions reductions equivalent to approximately one 
year of reductions needed for RFP. In general, we expect all actions 
needed to effect full implementation of the measures to occur within 60 
days after EPA notifies the state of a failure to meet RFP or to 
attain.\168\
---------------------------------------------------------------------------

    \168\ General Preamble at 13512, 13543-44 and Addendum at 42014-
42015.
---------------------------------------------------------------------------

    To satisfy the requirements of 40 CFR 51.1014, the contingency 
measures adopted as part of a PM2.5 attainment plan must: 
(1) consist of control measures for the area that are not otherwise 
included in the control strategy or that achieve emissions reductions 
not otherwise relied upon in the control strategy for the area (e.g., 
to meet RACM/RACT, BACM/BACT, or MSM requirements), and (2) specify the 
timeframe within which their requirements become effective following 
any of the EPA determinations specified in 40 CFR 51.1014(a).
    The Ninth Circuit recently rejected the EPA's interpretation of CAA 
section 172(c)(9) as allowing for early implementation of contingency 
measures, in a decision called Bahr v. EPA (``Bahr'').\169\ In Bahr, 
the Ninth Circuit concluded that contingency measures must take effect 
at the time the area fails to make RFP or attain by the applicable 
attainment date, not before. Thus, within the geographic jurisdiction 
of the Ninth Circuit, states cannot rely on early-implemented measures 
to comply with the contingency measure requirements under CAA section 
172(c)(9).
---------------------------------------------------------------------------

    \169\ Bahr v. EPA, 836 F.3d 1218, at 1235-1237 (9th Cir. 2016).
---------------------------------------------------------------------------

2. Contingency Measures in the 2016 PM2.5 Plan
    The 2016 PM2.5 Plan addresses the contingency measure 
requirement in Chapter 4 of the 2016 AQMP and in section H of the CARB 
Staff Report. Chapter 4 of the 2016 AQMP addresses contingency measures 
for failure to attain by describing emission reductions to be achieved 
by an adopted measure, South Coast Rule 445 (Wood-Burning Devices). The 
2016 PM2.5 Plan does not specifically address contingency 
measures for failure to meet RFP.
    The CARB Staff Report provides a brief statement acknowledging the 
recent Bahr decision and committing to work with the EPA and the 
District to provide additional documentation or develop any needed SIP 
revisions consistent with that decision.
3. EPA's Evaluation and Proposed Action
    As explained above in Section V.E, on April 2, 2018, CARB submitted 
a quantitative milestone report demonstrating that the 2017 
quantitative milestones in the 2016 PM2.5 Plan have been 
achieved, and the EPA has determined that this milestone report is 
adequate. Because the State and District have demonstrated that the 
South Coast area has met its 2017 quantitative milestones, RFP 
contingency measures for 2017 are no longer needed. Accordingly, we are 
proposing to find that the RFP contingency measure requirement for the 
2017 RFP milestone year is now moot as applied to the South Coast. The 
sole purpose of RFP contingency measures is to provide continued 
progress if an area fails to meet its RFP or quantitative milestone 
requirements. Failure to meet RFP or quantitative milestones for 2017 
would have required California to implement RFP contingency measures 
and to revise the 2016 PM2.5 Plan to assure that it still 
provided for attainment by the applicable attainment date of December 
31, 2019. In this case, however, the 2017 QM Report demonstrates that 
actual emissions levels in 2017 were consistent with the approved 2017 
RFP milestone year targets for direct PM2.5 and all 
precursor pollutants (NOX, SO2, VOCs, and 
ammonia) regulated in the 2016 PM2.5 Plan. Accordingly, RFP 
contingency measures for 2017 no longer have meaning or purpose, and 
the EPA proposes to find that the requirement for them is now moot.
    We are not proposing any action at this time on the attainment 
contingency measure component of the 2016 PM2.5 Plan and 
will act on that component through a subsequent rulemaking, as 
appropriate.

G. Major Stationary Source Control Requirements Under CAA Section 
189(e)

    Section 189(e) of the Act specifically requires that the control 
requirements applicable to major stationary sources of direct 
PM2.5 also apply to major stationary sources of 
PM2.5 precursors, except where the Administrator determines 
that such sources do not contribute significantly to PM2.5 
levels that exceed the standards in the area.\170\ The control 
requirements applicable to major stationary sources of direct 
PM2.5 in a Serious PM2.5 nonattainment area 
include, at minimum, the requirements of a NNSR permit program meeting 
the requirements of CAA sections 172(c)(5) and 189(b)(3).\171\ As part 
of our January 13, 2016 final action to reclassify the

[[Page 49891]]

South Coast area as Serious nonattainment for the 2006 PM2.5 
standards, we established a deadline 18 months from the effective date 
of our reclassification (or August 14, 2017) for the State to submit 
NNSR SIP revisions addressing the requirements of CAA sections 
189(b)(3) and 189(e) of the Act.\172\
---------------------------------------------------------------------------

    \170\ General Preamble at 13539 and 13541-42.
    \171\ CAA section 189(b)(1) (requiring that Serious area plans 
include provisions submitted to meet the requirements for Moderate 
areas in section 189(a)(1)).
    \172\ 81 FR 1514, at 1515 (January 13, 2016).
---------------------------------------------------------------------------

    California submitted NNSR SIP revisions to address the subpart 4 
requirements for Serious PM2.5 nonattainment areas on May 8, 
2017.\173\ We are not proposing any action on this submission at this 
time. We will act on this submission through a subsequent rulemaking, 
as appropriate.
---------------------------------------------------------------------------

    \173\ Letter from Richard W. Corey, Executive Officer, CARB, to 
Alexis Strauss, Acting Regional Administrator, EPA Region IX, May 8, 
2017. California previously submitted NNSR SIP revisions to address 
the subpart 4 requirements for Moderate PM2.5 
nonattainment areas, and the EPA approved these SIP revisions on May 
1, 2015 (80 FR 24821).
---------------------------------------------------------------------------

H. Motor Vehicle Emission Budgets

1. Requirements for Motor Vehicle Emissions Budgets
    Section 176(c) of the CAA requires federal actions in nonattainment 
and maintenance areas to conform to the SIP's goals of eliminating or 
reducing the severity and number of violations of the NAAQS and 
achieving expeditious attainment of the standards. Conformity to the 
SIP's goals means that such actions will not: (1) Cause or contribute 
to violations of a NAAQS, (2) worsen the severity of an existing 
violation, or (3) delay timely attainment of any NAAQS or any interim 
milestone.
    Actions involving Federal Highway Administration (FHWA) or Federal 
Transit Administration (FTA) funding or approval are subject to the 
EPA's transportation conformity rule, codified at 40 CFR part 93, 
subpart A. Under this rule, metropolitan planning organizations (MPOs) 
in nonattainment and maintenance areas coordinate with state and local 
air quality and transportation agencies, the EPA, FHWA, and FTA to 
demonstrate that an area's regional transportation plans (RTP) and 
transportation improvement programs (TIP) conform to the applicable 
SIP. This demonstration is typically done by showing that estimated 
emissions from existing and planned highway and transit systems are 
less than or equal to the motor vehicle emissions budgets (``budgets'' 
or ``MVEB'') contained in all control strategy SIPs. An attainment, 
maintenance, or RFP SIP should include budgets for the attainment year, 
each required RFP milestone year, or the last year of the maintenance 
plan, as appropriate, for direct PM2.5 and PM2.5 
precursors subject to transportation conformity analyses. Budgets are 
generally established for specific years and specific pollutants or 
precursors and must reflect all of the motor vehicle control measures 
contained in the attainment and RFP demonstrations.\174\ Under the 
PM2.5 SIP Requirements Rule, Serious area PM2.5 
attainment plans must define appropriate quantitative milestones and 
include projected RFP emission levels for direct PM2.5 and 
all PM2.5 plan precursors in each milestone year.\175\
---------------------------------------------------------------------------

    \174\ 40 CFR 93.118(e)(4)(v).
    \175\ See 81 FR 58010, 58091-58092.
---------------------------------------------------------------------------

    PM2.5 plans should identify budgets for direct 
PM2.5, NOX and all other PM2.5 
precursors for which on-road emissions are determined to significantly 
contribute to PM2.5 levels in the area for each RFP 
milestone year and the attainment year, if the plan demonstrates 
attainment. All direct PM2.5 SIP budgets should include 
direct PM2.5 motor vehicle emissions from tailpipes, brake 
wear, and tire wear. A state must also consider whether re-entrained 
paved road dust, unpaved road dust, or highway and transit construction 
dust are significant contributors and should be included in the direct 
PM2.5 budget.\176\
---------------------------------------------------------------------------

    \176\ 40 CFR 93.102(b) and 93.122(f); see also conformity rule 
preamble at 69 FR 40004, 40031-40036 (July 1, 2004).
---------------------------------------------------------------------------

    For an area designated nonattainment for the 2006 PM2.5 
NAAQS before January 15, 2015, the attainment plan must contain 
quantitative milestones to be achieved no later than 3 years after 
December 31, 2014, and every 3 years thereafter until the milestone 
date that falls within 3 years after the applicable attainment 
date.\177\ As the EPA explained in the preamble to the PM2.5 
SIP Requirements Rule, it is important to include a post-attainment 
year quantitative milestone to ensure that, if the area fails to attain 
by the attainment date, the EPA can continue to monitor the area's 
progress toward attainment while the state develops a new attainment 
plan.\178\
---------------------------------------------------------------------------

    \177\ 40 CFR 51.1013(a)(4), see also 81 FR 58010, 58058 and 
58063-58064 (August 24, 2016).
    \178\ See 81 FR 58010, 58063-58064 (August 24, 2016).
---------------------------------------------------------------------------

    Transportation conformity trading mechanisms are allowed under 40 
CFR 93.124 where a SIP establishes appropriate mechanisms for such 
trades. The basis for the trading mechanism is the SIP attainment 
modeling that established the relative contribution of each 
PM2.5 precursor pollutant. The applicability of emission 
trading between conformity budgets for conformity purposes is described 
in 40 CFR 93.124(c).
    In general, only budgets in approved SIPs can be used for 
transportation conformity purposes. However, section 93.118(e) of the 
transportation conformity rule allows budgets in a SIP submission to 
apply for conformity purposes before the SIP submission is approved 
under certain circumstances. First, there must not be any other 
approved SIP budgets that have been established for the same year, 
pollutant, and CAA requirement. Second, the EPA must find that the 
submitted SIP budgets are adequate for transportation conformity 
purposes. To be found adequate, the submission must meet the conformity 
adequacy requirements of 40 CFR 93.118(e)(4) and (5).
    The transportation conformity rule allows for replacement of 
previously approved budgets by submitted motor vehicle emissions 
budgets that the EPA has found adequate, if the EPA has limited the 
duration of its prior approval to the period before it finds 
replacement budgets adequate.\179\ However, the EPA will consider a 
state's request to limit the duration of an MVEB approval only if the 
request includes the following elements:
---------------------------------------------------------------------------

    \179\ 40 CFR 93.118(e)(1).
---------------------------------------------------------------------------

     An acknowledgement and explanation as to why the budgets 
under consideration have become outdated or deficient;
     A commitment to update the budgets as part of a 
comprehensive SIP update; and
     A request that the EPA limit the duration of its approval 
to the time when new budgets have been found to be adequate for 
transportation conformity purposes.\180\
---------------------------------------------------------------------------

    \180\ See, e.g., 67 FR 69139 (November 15, 2002), limiting our 
prior approval of budgets in certain California SIPs.
---------------------------------------------------------------------------

2. Motor Vehicle Emissions Budgets in the 2016 PM2.5 Plan
    Consistent with the requirements of 40 CFR 51.1013(a)(4), the 2016 
PM2.5 Plan identifies December 31, 2017, as the first 
quantitative milestone date (i.e., the date 3 years after December 31, 
2014). The second quantitative milestone date is December 31, 2020, and 
is also the last milestone date identified in the Plan because it falls 
within 3 years after the December 31, 2019 attainment date for the 
area.\181\
---------------------------------------------------------------------------

    \181\ Under CAA section 188(c)(2), a Serious PM2.5 
nonattainment area must attain the PM2.5 NAAQS as 
expeditiously as practicable but no later than the end of the tenth 
calendar year after the area is designated as nonattainment. Because 
the South Coast area was designated as nonattainment for the 2006 
PM2.5 NAAQS effective December 14, 2009 (74 FR 58688, 
November 13, 2009), the latest permissible attainment date for the 
area is December 31, 2019.

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

[[Page 49892]]

    The 2016 PM2.5 Plan includes budgets for direct 
PM2.5, NOX, and VOC for 2017 and 2019 (RFP 
milestone year and projected attainment year, respectively) and for 
2020 (post-attainment year quantitative milestone).\182\ The budgets 
were calculated using EMFAC2014, CARB's latest version of the EMFAC 
model for estimating emissions from on-road vehicles operating in 
California, and SCAG's latest modeled VMT and speed distributions from 
the 2016 Regional Transportation Plan/Sustainable Communities Strategy 
adopted in April of 2016. The budgets reflect annual average emissions 
because those emissions are linked with the District's attainment 
demonstration for the 24-hour PM2.5 NAAQS.
---------------------------------------------------------------------------

    \182\ 2016 PM2.5 Plan, Appendix VI-D and Table VI-D-4 
(for 2017, 2019, and 2020 budgets).
---------------------------------------------------------------------------

    The direct PM2.5 budgets include tailpipe, brake wear, 
and tire wear emissions as well as paved road dust, unpaved road dust, 
and road construction dust emissions.\183\ The Plan includes budgets 
for VOC and NOX because they are regulated precursors under 
the Plan. Under 40 CFR 93.102(b)(2)(v), states are not required to 
include budgets for SO2 and/or NH3 unless EPA or 
the state has made a finding that transportation-related emissions of 
any of these precursors within the nonattainment area are significant 
contributors to the PM2.5 nonattainment problem. Neither the 
State nor the EPA has made such a funding. The budgets included in the 
2016 PM2.5 Plan are shown in Table 6 below.
---------------------------------------------------------------------------

    \183\ 2016 PM2.5 Plan, Appendix VI-D, Table VI-D-3, 
p. VI-D-4.
[GRAPHIC] [TIFF OMITTED] TP03OC18.004

    In the submittal letter for the 2016 PM2.5 Plan, CARB 
requested that we limit the duration of our approval of the budgets to 
the period before the effective date of the EPA's adequacy finding for 
any subsequently submitted budgets.\184\
---------------------------------------------------------------------------

    \184\ Letter from Richard W. Corey, Executive Officer, CARB, to 
Alexis Strauss, Acting Regional Administrator, EPA Region IX, page 
3, April 27, 2017.
---------------------------------------------------------------------------

    We found the budgets for the 2017 RFP year and the 2019 attainment 
year adequate in a letter dated December 19, 2017.\185\ In today's 
action, we are proposing to approve these budgets.
---------------------------------------------------------------------------

    \185\ Id.
---------------------------------------------------------------------------

Conformity Trading Mechanism
    The 2016 PM2.5 Plan also includes a proposed trading 
mechanism for transportation conformity analyses that would allow 
future decreases in NOX emissions from on-road mobile 
sources to offset any on-road increases in PM2.5, using the 
ratios shown in Table 7 below.\186\ For the 2006 24-hour 
PM2.5 NAAQS the State is proposing to use the same ratios 
that were submitted for use with that NAAQS in the 2012 
PM2.5 Plan.\187\
---------------------------------------------------------------------------

    \186\ 2016 PM2.5 Plan, Appendix VI-D, Table VI-D-5.
    \187\ 82 FR 22025 (April 14, 2016).

       Table 7--Trading Equivalencies for 2006 24-Hour PM2.5 NAAQS
------------------------------------------------------------------------
                                               NOX      VOC      PM2.5
------------------------------------------------------------------------
NOX........................................        1    3.151     0.067
VOC........................................    0.317        1     0.021
PM2.5......................................   14.833   46.792         1
------------------------------------------------------------------------
Source: 2016 PM2.5 Plan, Appendix VI-D, Table VI-D-5, and letter from
  Phil Fine, Deputy Executive Officer, SCAQMD, to Amy Zimpfer, Associate
  Director, Air Division, EPA Region 9, March 14, 2018.

    To ensure that the trading mechanism does not affect the ability of 
the South Coast to meet the NOX budget, the NOX 
emission reductions available to supplement the PM2.5 budget 
would only be those remaining after the NOX budget has been 
met.\188\ SCAG must clearly document the calculations used in the 
trading when demonstrating conformity, along with any additional 
reductions of NOX, PM2.5 or VOC emissions in the 
conformity analysis. It should be noted that the trading calculations 
are performed prior to the final rounding to demonstrate conformity 
with the budgets.
---------------------------------------------------------------------------

    \188\ 2016 PM2.5 Plan, Appendix VI-D, page VI-D-5.
---------------------------------------------------------------------------

    The District provided a clarification as to how the trading 
mechanism would be implemented in a March 14, 2018 letter.\189\ In that 
letter, the District clarified that the trading mechanism identified in 
the 2012 AQMP for the 2006 PM2.5 24-hour NAAQS, which the 
EPA did not previously act on, is

[[Page 49893]]

included in the 2016 AQMP for approval by the EPA for use by SCAG in 
conformity determinations for the 2006 PM2.5 NAAQS for 
analysis years after the attainment year of 2019. The letter also 
explained why these trading ratios are still appropriate for use in 
conformity determinations even though they are derived from modeling 
conducted for the 2012 AQMP.
---------------------------------------------------------------------------

    \189\ Letter from Philip Fine, Deputy Executive Officer, 
Planning, Rule Development, and Area Sources, SCAQMD, to Amy 
Zimpfer, Associate Director, Air Division, EPA Region IX, regarding 
trading ratios among PM2.5 precursors, March 14, 2018.
---------------------------------------------------------------------------

    The 2016 PM2.5 Plan also provides that SCAG, the MPO 
responsible for demonstrating transportation conformity, shall clearly 
document the calculations used in the trading, along with any 
additional reductions of NOX, PM2.5 or VOC 
emissions in the conformity analysis.
3. EPA's Evaluation and Proposed Actions
    The EPA generally first conducts a preliminary review of budgets 
submitted with an attainment, RFP, or maintenance plan for adequacy, 
prior to acting on the plan itself, and did so with respect to the 
replacement PM2.5 budgets in the 2016 PM2.5 Plan. 
On October 18, 2017, the EPA announced the availability of the 2016 
PM2.5 Plan with budgets and a 30-day public comment period. 
This announcement was posted on EPA's Adequacy website at: https://www.epa.gov/state-and-local-transportation/state-implementation-plans-sip-submissions-currently-under-epa. The comment period for this 
notification ended on November 17, 2017. We did not receive any 
comments during this comment period. We found the budgets adequate on 
December 19, 2017.\190\ A notice of the adequacy finding was published 
in the Federal Register on January 5, 2018.\191\
---------------------------------------------------------------------------

    \190\ Letter from Matthew J. Lakin, Acting Director, Air 
Division, EPA Region IX, to Richard W. Corey, Executive Officer, 
CARB, December 19, 2017.
    \191\ See 83 FR 679, January 5, 2018.
---------------------------------------------------------------------------

    Based on the information about SO2 and ammonia emissions 
in the Plan and in accordance with 40 CFR 93.102(b)(2)(v), we propose 
to find that it is not necessary to establish motor vehicle emissions 
budgets for transportation-related emissions of SO2 and 
ammonia to attain the 2006 PM2.5 standards in the South 
Coast.
    For the reasons discussed in sections V.D. and V.E. of this 
proposed rule, we are proposing to approve the RFP and attainment 
demonstrations in the 2016 PM2.5 Plan. The 2017 RFP and 2019 
attainment budgets, as given in Table 6 of this proposed rule, are 
consistent with these demonstrations, are clearly identified and 
precisely quantified, and meet all other applicable statutory and 
regulatory requirements including the adequacy criteria in 93.118(e)(4) 
and (5). For these reasons, the EPA proposes to approve the budgets 
listed in Table 6 above. We provided a more detailed discussion in our 
adequacy letter, which can be found in the docket for today's action.
    We are not taking action on the 2020 budgets at this time. Although 
the post-attainment year quantitative milestone is a required element 
of the Serious area plan, it is not necessary to demonstrate 
transportation conformity for 2020 or to use the 2020 budgets in 
transportation conformity determinations until such time as the area 
fails to attain the 2006 PM2.5 NAAQS. Additionally, the EPA 
has not yet started the adequacy process for the 2020 budgets. 
Therefore, the EPA is not taking action on the submitted budgets for 
2020 in the 2016 PM2.5 Plan at this time.
    If the EPA were to either find adequate or approve the post-
attainment milestone year budgets now, those budgets would have to be 
used in transportation conformity determinations that are made after 
the effective date of the adequacy finding or approval even if the 
South Coast area ultimately attains the PM2.5 NAAQS by the 
Serious area attainment date. This would mean that SCAG would be 
required to demonstrate conformity for the post-attainment date 
milestone year and all later years addressed in the conformity 
determination (e.g., the last year of the metropolitan transportation 
plan) to the post-attainment date RFP budgets rather than the budgets 
associated with the attainment year for the area (i.e., the budgets for 
2019). The EPA does not believe that it is necessary to demonstrate 
conformity using these post-attainment year budgets in areas that 
either the EPA anticipates will attain by the attainment date or in 
areas that attain by the attainment date. The EPA has found adequate 
the budgets for the first milestone year (2017) and the attainment year 
(2019) for the South Coast PM2.5 nonattainment area.\192\
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    \192\ Letter from Matthew J. Lakin, Acting Director, Air 
Division, EPA Region IX, to Richard W. Corey, Executive Officer, 
CARB, December 19, 2017, and 83 FR 679 (January 5, 2018).
---------------------------------------------------------------------------

    If the EPA determines that the South Coast area has failed to 
attain the 2006 PM2.5 NAAQS by the applicable attainment 
date, the EPA will begin the budget adequacy and approval processes for 
the post-attainment year (2020) budgets. If the EPA finds the 2020 
budgets adequate or approves them, those budgets will have to be used 
in subsequent transportation conformity determinations. The EPA 
believes that initiating the process to act on the submitted post-
attainment year MVEBs following a determination that the area has 
failed to attain by the Serious area attainment date ensures that 
transportation activities will not cause or contribute to new 
violations, increase the frequency or severity of any existing 
violations, or delay timely attainment or any required interim emission 
reductions or milestones in the South Coast nonattainment area, 
consistent with the requirements of CAA section 176(c)(1)(B).
    We have previously approved motor vehicle emissions budgets for the 
1997 annual and 24-hour PM2.5 NAAQS.\193\ These budgets will 
continue to apply for the 1997 PM2.5 NAAQS in the South 
Coast area.
---------------------------------------------------------------------------

    \193\ 76 FR 69928, at 69951 (November 9, 2011).
---------------------------------------------------------------------------

    The EPA has reviewed the trading mechanism described on pages VI-D-
5 and VI-D-6 in Appendix VI-D of the 2016 AQMP and, given the 
clarification letter submitted to the EPA on March 14, 2018, finds this 
trading mechanism appropriate for use in transportation conformity 
analyses in the South Coast for the 2006 PM2.5 NAAQS. We 
agree with the District that these trading ratios are still appropriate 
for use in transportation conformity determinations even though they 
are derived from modeling conducted for the 2012 AQMP. We therefore 
propose to approve the trading mechanism as an enforceable component of 
the transportation conformity program for the South Coast for the 2006 
PM2.5 NAAQS.
    In the submittal letter for the 2016 PM2.5 Plan, CARB 
requested that we limit the duration of our approval of the budgets to 
the period before the effective date of the EPA's adequacy finding for 
any subsequently submitted budgets.\194\ The transportation conformity 
rule allows us to limit the approval of budgets.\195\ CARB's request 
does not, however, contain an acknowledgement and explanation as to why 
the budgets under consideration will become outdated or a commitment to 
update the budgets as part of a comprehensive SIP update. Therefore, we 
are not proposing at this time to limit the duration of our approval of 
the submitted budgets. In order to limit the duration of our approval, 
we would need the information described above to determine whether such 
limitation is reasonable and appropriate in this case. Once CARB has 
provided the necessary information, we intend to review it and

[[Page 49894]]

take appropriate action. If we propose to limit the duration of our 
approval of the budgets in the 2016 PM2.5 Plan, we will 
provide the public an opportunity to comment. The duration of our 
approval of the submitted budgets will not be limited until we complete 
such a rulemaking.
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    \194\ See letter dated April 27, 2017, from Richard W. Corey, 
Executive Officer, CARB, to Alexis Strauss, Acting Regional 
Administrator, EPA Region IX, page 3.
    \195\ 40 CFR 93.118(e)(1).
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VI. Summary of Proposed Actions and Request for Public Comment

    Under CAA section 110(k)(3), the EPA is proposing to approve SIP 
revisions submitted by California to address the Act's Serious area 
planning requirements for the 2006 PM2.5 NAAQS in the South 
Coast nonattainment area. Specifically, the EPA is proposing to approve 
the following elements of the 2016 PM2.5 Plan:
    1. A comprehensive, accurate, current inventory of actual emissions 
from all sources of PM2.5 and PM2.5 precursors in 
the area (CAA section 172(c)(3));
    2. Provisions to assure that BACM, including BACT, for the control 
of direct PM2.5 and PM2.5 precursors shall be 
implemented no later than 4 years after the area is reclassified (CAA 
section 189(b)(1)(B));
    3. A demonstration (including air quality modeling) that the plan 
provides for attainment as expeditiously as practicable but no later 
than December 31, 2019 (CAA sections 188(c)(2) and 189(b)(1)(A));
    4. Plan provisions that require RFP (CAA section 172(c)(2));
    5. Quantitative milestones that are to be achieved every 3 years 
until the area is redesignated attainment and which demonstrate RFP 
toward attainment by the applicable date (CAA section 189(c)); and
    6. 2017 and 2019 motor vehicle emissions budgets, as shown in Table 
6 of this proposed rule, because they are derived from an approvable 
RFP plan and attainment demonstration and meet the requirements of CAA 
section 176(c) and 40 CFR part 93, subpart A.
    The EPA is also proposing to approve the interpollutant trading 
mechanism provided in the 2016 PM2.5 Plan and clarified in a 
March 14, 2018 letter from the District for use in transportation 
conformity analyses for the 2006 PM2.5 NAAQS, in accordance 
with 40 CFR 93.124. We are not proposing any action at this time on the 
attainment contingency measure component of the 2016 PM2.5 
Plan. Finally, the EPA is proposing to find that the requirement for 
contingency measures to be undertaken if the area fails to make 
reasonable further progress under CAA section 172(c)(9) is moot as 
applied to the 2017 milestone year, because the State and District have 
demonstrated to the EPA's satisfaction that the 2017 milestones have 
been met.
    We will accept comments from the public on these proposals for the 
next 30 days. The deadline and instructions for submission of comments 
are provided in the DATES and ADDRESSES sections at the beginning of 
this preamble.

VII. Statutory and Executive Order Reviews

    Under the Clean Air Act, the Administrator is required to approve a 
SIP submission that complies with the provisions of the Act and 
applicable federal regulations. 42 U.S.C. 7410(k); 40 CFR 52.02(a). 
Thus, in reviewing SIP submissions, the EPA's role is to approve state 
choices, provided that they meet the criteria of the Clean Air Act. 
Accordingly, this proposed action merely proposes to approve state law 
as meeting federal requirements and does not impose additional 
requirements beyond those imposed by state law. For that reason, this 
proposed action:
     Is not a ``significant regulatory action'' subject to 
review by the Office of Management and Budget under Executive Orders 
12866 (58 FR 51735, October 4, 1993) and 13563 (76 FR 3821, January 21, 
2011);
     is not an Executive Order 13771 (82 FR 9339, February 2, 
2017) regulatory action because SIP approvals are exempted under 
Executive Order 12866;
     does not impose an information collection burden under the 
provisions of the Paperwork Reduction Act (44 U.S.C. 3501 et seq.);
     is certified as not having a significant economic impact 
on a substantial number of small entities under the Regulatory 
Flexibility Act (5 U.S.C. 601 et seq.);
     does not contain any unfunded mandate or significantly or 
uniquely affect small governments, as described in the Unfunded 
Mandates Reform Act of 1995 (Pub. L. 104-4);
     does not have Federalism implications as specified in 
Executive Order 13132 (64 FR 43255, August 10, 1999);
     is not an economically significant regulatory action based 
on health or safety risks subject to Executive Order 13045 (62 FR 
19885, April 23, 1997);
     is not a significant regulatory action subject to 
Executive Order 13211 (66 FR 28355, May 22, 2001);
     is not subject to requirements of Section 12(d) of the 
National Technology Transfer and Advancement Act of 1995 (15 U.S.C. 272 
note) because application of those requirements would be inconsistent 
with the Clean Air Act; and
     does not provide the EPA with the discretionary authority 
to address disproportionate human health or environmental effects with 
practical, appropriate, and legally permissible methods under Executive 
Order 12898 (59 FR 7629, February 16, 1994).
    In addition, the SIP is not approved to apply on any Indian 
reservation land or in any other area where the EPA or an Indian tribe 
has demonstrated that a tribe has jurisdiction. In those areas of 
Indian country, the rule does not have tribal implications and will not 
impose substantial direct costs on tribal governments or preempt tribal 
law as specified by Executive Order 13175 (65 FR 67249, November 9, 
2000).

List of Subjects in 40 CFR Part 52

    Environmental protection, Air pollution control, Ammonia, 
Incorporation by reference, Intergovernmental relations, Oxides of 
nitrogen, Particulate matter, Reporting and recordkeeping requirements, 
Sulfur oxides, Volatile organic compounds.

    Authority: 42 U.S.C. 7401 et seq.

    Dated: September 24, 2018.
Deborah Jordan,
Acting Regional Administrator, Region 9.
[FR Doc. 2018-21560 Filed 10-2-18; 8:45 am]
 BILLING CODE 6560-50-P