Document ID: EPA-R09-OAR-2019-0440-0005
Agency: epa
Document Type: Proposed Rule
Title: Air Quality State Implementation Plans; Approvals and Promulgations: 2008 8-Hour Ozone Nonattainment Area Requirements; Western Nevada County, CA
Posted Date: 2021-01-12T05:00Z

[Federal Register Volume 86, Number 7 (Tuesday, January 12, 2021)]
[Proposed Rules]
[Pages 2318-2337]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2020-28885]

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ENVIRONMENTAL PROTECTION AGENCY

40 CFR Part 52

[EPA-R09-OAR-2019-0440; FRL-10018-44-Region 9]

Clean Air Plans; 2008 8-Hour Ozone Nonattainment Area 
Requirements; Western Nevada County, California

AGENCY: Environmental Protection Agency (EPA).

ACTION: Proposed rule.

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SUMMARY: The Environmental Protection Agency (EPA) is proposing to 
approve, or conditionally approve, all or portions of a state 
implementation plan (SIP) revision submitted by the State of California 
to meet Clean Air Act (CAA or ``Act'') requirements for the 2008 8-hour 
ozone national ambient air quality standards (NAAQS or ``standards'') 
in the Nevada County (Western part), California ozone nonattainment 
area (``Western Nevada County''). The SIP revision is the ``Ozone 
Attainment Plan, Western Nevada County, State Implementation Plan for 
the 2008 Primary Federal 8-Hour Ozone Standard of .075 ppm'' (``2018 
Western Nevada County Ozone Plan'' or ``Plan''). The 2018 Western 
Nevada County Ozone Plan addresses the Serious nonattainment area 
requirements for the 2008 ozone NAAQS, including the requirements for 
emissions inventories, attainment demonstration, reasonable further 
progress, reasonably available control measures, and contingency 
measures, among others; and establishes motor vehicle emissions 
budgets. The EPA is proposing to approve the 2018 Western Nevada County 
Ozone Plan as meeting all the applicable ozone nonattainment area 
requirements except for the contingency measures requirement, for which 
the EPA is proposing conditional approval. In addition, the EPA is 
beginning the adequacy process for the 2020 motor vehicle emissions 
budgets in the 2018 Western Nevada County Ozone Plan through this 
proposed rulemaking.

DATES: Written comments must arrive on or before February 11, 2021.

ADDRESSES: Submit your comments, identified by Docket ID No. EPA-R09-
OAR-2019-0440 at https://www.regulations.gov. For comments submitted at 
Regulations.gov, follow the online instructions for submitting 
comments. Once submitted, comments cannot be edited or removed from 
Regulations.gov. The EPA may publish any comment received to its public 
docket. Do not submit electronically any information you consider to be 
Confidential Business Information (CBI) or other information whose 
disclosure is restricted by statute. Multimedia submissions (audio, 
video, etc.) must be accompanied by a written comment. The written 
comment is considered the official comment and should include 
discussion of all points you wish to make. The EPA will generally not 
consider comments or comment contents located outside of the primary 
submission (i.e., on the web, cloud, or other file sharing system). For 
additional submission methods, 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 https://www.epa.gov/dockets/commenting-epa-dockets. If you need assistance in a 
language other than English or if you are a person with disabilities 
who needs a reasonable accommodation at no cost to you, please contact 
the person identified in the FOR FURTHER INFORMATION CONTACT section.

FOR FURTHER INFORMATION CONTACT: T. Khoi Nguyen, Air Planning Office 
(AIR-2), EPA Region IX, 75 Hawthorne Street, San Francisco, CA 94105, 
(415) 947-4120, or by email at nguyen.thien@epa.gov.

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

Table of Contents

I. Regulatory Context
    A. Ozone Standards, Area Designations, and SIPs
    B. The Western Nevada County Ozone Nonattainment Area

[[Page 2319]]

    C. CAA and Regulatory Requirements for 2008 Ozone Nonattainment 
Area SIPs
II. The 2018 Western Nevada County Ozone Plan
    A. Summary of Submission
    B. Clean Air Act Procedural Requirements for Adoption and 
Submission of SIP Revisions
III. Evaluation of the 2018 Western Nevada County Ozone Plan
    A. Emissions Inventories
    B. Emissions Statements
    C. Reasonably Available Control Measures Demonstration
    D. Attainment Demonstration
    E. Rate of Progress Plan and Reasonable Further Progress 
Demonstration
    F. Contingency Measures
    G. Motor Vehicle Emissions Budgets for Transportation Conformity
    H. Other Clean Air Act Requirements Applicable to Serious Ozone 
Nonattainment Areas
IV. Proposed Action
V. Statutory and Executive Order Reviews

I. Regulatory Context

A. Ozone Standards, Area Designations, and SIPs

    Ground-level ozone pollution is formed from the reaction of 
volatile organic compounds (VOC) and oxides of nitrogen 
(NOX) in the presence of sunlight.\1\ These two pollutants, 
referred to as ozone precursors, are emitted by many types of sources, 
including on-and off-road motor vehicles and engines, power plants and 
industrial facilities, and smaller area sources such as lawn and garden 
equipment and paints.
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    \1\ The State of California refers to reactive organic gases 
(ROG) rather than VOC in some of its ozone-related SIP submissions. 
As a practical matter, ROG and VOC refer to the same set of chemical 
constituents, and for the sake of simplicity, we refer to this set 
of gases as VOC in this proposed rule.
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    Scientific evidence indicates that adverse public health effects 
occur following exposure to ozone, particularly in children and adults 
with lung disease. Breathing air containing ozone can reduce lung 
function and inflame airways, which can increase respiratory symptoms 
and aggravate asthma or other lung diseases.\2\
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    \2\ ``Fact Sheet--2008 Final Revisions to the National Ambient 
Air Quality Standards for Ozone'' dated March 2008.
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    Under section 109 of the CAA, the EPA promulgates NAAQS for 
pervasive air pollutants, such as ozone. The NAAQS are concentration 
levels that, the attainment and maintenance of which, the EPA has 
determined to be requisite to protect public health and welfare. 
Section 110 of the CAA requires states to develop and submit SIPs to 
implement, maintain, and enforce the NAAQS.
    In 1979, the EPA established the 1-hour ozone NAAQS of 0.12 parts 
per million (ppm) (referred to herein as the ``1-hour ozone 
NAAQS'').\3\ All of Nevada County was designated ``Unclassifiable/
Attainment'' for the 1-hour standard on November 15, 1990.\4\
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    \3\ 44 FR 8202 (February 8, 1979).
    \4\ 56 FR 56694 (November 6, 1991).
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    In 1997, the EPA revised the NAAQS for ozone, setting it at 0.08 
ppm averaged over an 8-hour timeframe (referred to herein as the ``1997 
ozone NAAQS'') to replace the existing 1-hour ozone NAAQS.\5\ In 2004, 
the EPA initially designated and classified Western Nevada County as a 
``Subpart 1'' nonattainment area for the 1997 ozone NAAQS.\6\ In 
response to a decision of the United States Court of Appeals for the 
District of Columbia Circuit vacating the EPA's subpart 1 designations, 
the EPA in 2012 revised the area's classification for the 1997 ozone 
NAAQS to ``Moderate,'' with an outermost attainment date of June 15, 
2011.\7\ In 2011, the design value for the area was 0.079 ppm, and the 
EPA published a clean data determination on December 3, 2012, 
suspending attainment-related planning requirements for the 1997 ozone 
NAAQS.\8\
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    \5\ 62 FR 38856 (July 18, 1997). The 1-hour ozone standard was 
revoked effective June 15, 2005. See 70 FR 44470 (August 3, 2005).
    \6\ 69 FR 23857 (April 30, 2004).
    \7\ 77 FR 28423 (May 14, 2012). For more details on the revised 
classification, see 77 FR 56775, 56776 (September 14, 2012).
    \8\ 77 FR 71551 (December 3, 2012).
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    In 2008, the EPA lowered the 8-hour ozone NAAQS to 0.075 ppm 
(referred to herein as the ``2008 ozone NAAQS'') to replace the 1997 
ozone NAAQS of 0.08 ppm.\9\ In 2012, the EPA designated Western Nevada 
County as nonattainment for the 2008 ozone NAAQS and classified the 
area as Marginal.\10\ Areas classified as Marginal must attain the 
NAAQS within 3 years of the effective date of the nonattainment 
designation. For Western Nevada County, the applicable Marginal area 
attainment date was as expeditiously as practicable but no later than 
July 20, 2015. The area failed to attain the 2008 ozone NAAQS by this 
date, and the EPA published a reclassification to Moderate on May 4, 
2016.\11\ Upon reclassification, Western Nevada County was required to 
attain the 2008 ozone NAAQS as expeditiously as practicable but no 
later than July 20, 2018.
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    \9\ 73 FR 16436 (March 27, 2008). The EPA further tightened the 
8-hour ozone NAAQS to 0.070 ppm in 2015, but today's proposed action 
relates to the requirements for the 2008 ozone NAAQS only. 
Information on the 2015 ozone NAAQS is available at 80 FR 65292 
(October 26, 2015).
    \10\ 77 FR 30088 (May 21, 2012).
    \11\ 81 FR 26697 (May 4, 2016).
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    In November 2018, pursuant to CAA section 181(b)(2), the EPA 
proposed to determine that the Western Nevada County Moderate 
nonattainment area failed to attain the 2008 ozone NAAQS by the 
Moderate area attainment date.\12\ Additionally, following the EPA's 
November 2018 proposal, the California Air Resources Board (CARB) 
submitted a request under CAA section 181(b)(3) to voluntarily 
reclassify the Western Nevada County nonattainment area from Moderate 
to Serious nonattainment for the 2008 ozone standards accompanied by a 
SIP revision to address planning elements for a Serious area.\13\
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    \12\ 83 FR 56781 (November 14, 2018).
    \13\ See letter dated December 2, 2018, from Richard W. Corey, 
Executive Officer, CARB, to Michael Stoker, Regional Administrator, 
EPA Region IX, and letter dated November 14, 2018 from Gretchen 
Bennitt, Executive Director, NSAQMD, to Richard W. Corey, Executive 
Officer, CARB, subject ``Submittal of the Northern Sierra Air 
Quality Management District Ozone Attainment Plan for the 2008 
Federal 8-hour Ozone Standard.''
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    In a final rule dated August 23, 2019, the EPA found that Western 
Nevada County failed to attain the 2008 ozone NAAQS by the applicable 
attainment date, and reclassified the area as Serious by operation of 
law, effective September 23, 2019.\14\ Once reclassified to Serious, 
the area is required to attain the standard as expeditiously as 
practicable, but no later than 9 years after the initial designation as 
nonattainment, i.e., July 20, 2021.
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    \14\ 84 FR 44238. The notice for this action acknowledges CARB's 
request for voluntary reclassification, and notes that the EPA's 
determination resulted in the same outcome as would occur with an 
approval of that request.
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    The SIP revision that is the subject of today's proposed action 
addresses the Serious nonattainment area requirements that apply to 
Western Nevada County for the 2008 ozone NAAQS.

B. The Western Nevada County Ozone Nonattainment Area

    The Western Nevada County nonattainment area for the 2008 ozone 
NAAQS consists of the portion of Nevada County west of the ridge of the 
Sierra Nevada mountains. Western Nevada County encompasses an area of 
approximately 800 square miles. The nonattainment area is bounded on 
the north by the Middle Yuba River and most of the southern border is 
defined by the Bear River. The eastern boundary is a line running 
north/south that generally follows the ridge of the Sierra

[[Page 2320]]

Nevada mountains.\15\ The population of the Western Nevada County 
nonattainment area is about 83,000 people.\16\
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    \15\ For a precise definition of the boundaries of the Western 
Nevada County 2008 ozone nonattainment area, see 40 CFR 81.305.
    \16\ 2018 Western Nevada County Ozone Plan, page 12.
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    Air quality in Western Nevada County is regulated jointly by the 
Northern Sierra Air Quality Management District (NSAQMD or 
``District'') and CARB. The Nevada County Transportation Commission 
(NCTC) is the regional transportation planning agency for the County of 
Nevada. For transportation planning purposes, the area is an isolated 
rural area.\17\
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    \17\ Isolated rural nonattainment and maintenance areas are 
defined in 40 CFR 93.101 as areas that do not contain or are not 
part of any metropolitan planning area as designated under the 
transportation planning regulations.
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C. CAA and Regulatory Requirements for 2008 Ozone Nonattainment Area 
SIPs

    States must implement the 2008 ozone NAAQS under title I, part D of 
the CAA, including sections 171-179B of subpart 1, ``Nonattainment 
Areas in General,'' and sections 181-185 of subpart 2, ``Additional 
Provisions for Ozone Nonattainment Areas.'' To assist states in 
developing effective plans to address ozone nonattainment problems, in 
2015, the EPA issued a SIP Requirements Rule (SRR) for the 2008 ozone 
NAAQS (``2008 Ozone SRR'') that addressed implementation of the 2008 
standards, including attainment dates, requirements for emissions 
inventories, attainment and reasonable further progress (RFP) 
demonstrations, among other SIP elements, as well as the transition 
from the 1997 ozone NAAQS to the 2008 ozone NAAQS and associated anti-
backsliding requirements.\18\ The 2008 Ozone SRR is codified at 40 CFR 
part 51, subpart AA. We discuss the CAA and regulatory requirements for 
the elements of 2008 ozone plans relevant to this proposal in more 
detail in Section III of this document.
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    \18\ 80 FR 12264 (March 6, 2015).
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    The EPA's 2008 Ozone SRR was challenged, and on February 16, 2018, 
the U.S. Court of Appeals for the D.C. Circuit (``D.C. Circuit'') 
published its decision in South Coast Air Quality Management. District 
v. EPA (``South Coast II'') \19\ vacating portions of the 2008 Ozone 
SRR. The only aspect of the South Coast II decision that relates to 
this proposed action is the vacatur of the alternative baseline year 
for RFP plans. More specifically, the 2008 Ozone SRR required states to 
develop the baseline emissions inventory for RFP plans using the 
emissions inventory for the most recent calendar year for which states 
submit a triennial inventory to the EPA under subpart A, ``Air 
Emissions Reporting Requirements,'' of 40 CFR part 51, which was 2011. 
The 2008 Ozone SRR, however, allowed states to use an alternative year, 
between 2008 and 2012, for the baseline emissions inventory provided 
the state demonstrated why the alternative baseline year was 
appropriate. In the South Coast II decision, the D.C. Circuit vacated 
the provisions of the 2008 Ozone SRR that allowed states to use an 
alternative baseline year for demonstrating RFP.
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    \19\ South Coast Air Quality Management District v. EPA, 882 
F.3d 1138 (D.C. Cir. 2018). The term ``South Coast II'' is used in 
reference to the 2018 court decision to distinguish it from a 
decision published in 2006 also referred to as ``South Coast.'' The 
earlier decision involved a challenge to the EPA's Phase 1 
implementation rule for the 1997 ozone NAAQS. South Coast Air 
Quality Management Dist. v. EPA, 472 F.3d 882 (D.C. Cir. 2006).
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II. The 2018 Western Nevada County Ozone Plan

A. Summary of Submission

    On December 2, 2018, CARB submitted the 2018 Western Nevada County 
Ozone Plan to the EPA as a revision to the California SIP to address 
the nonattainment area requirements for Western Nevada County for the 
2008 ozone NAAQS.\20\ The 2018 Western Nevada County Ozone Plan 
includes various chapters and appendices, described further below, plus 
the District's resolution of adoption for the Plan (District Resolution 
2018-07) and CARB's resolution of adoption of the Plan as a revision to 
the California SIP (CARB Resolution 18-36).\21\ The Plan addresses the 
CAA requirements for emissions inventories, air quality modeling 
demonstrating attainment, reasonably available control measures (RACM), 
RFP, and motor vehicle emissions budgets, among other requirements.
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    \20\ Letter dated December 2, 2018, from Richard Corey, 
Executive Officer, CARB, to Mike Stoker, Regional Administrator, 
U.S. Environmental Protection Agency Region 9.
    \21\ NSAQMD Board Resolution 2018-7, October 22, 2018; CARB 
Board Resolution 18-36, 2018 Ozone Attainment Plan for Western 
Nevada County.
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    The 2018 Western Nevada County Ozone Plan begins with an executive 
summary, an introductory section discussing ozone pollution and the 
Western Nevada County nonattainment area generally, a discussion about 
specific challenges in meeting air quality standards in the area, and a 
formal request to reclassify the area to Serious for the 2008 ozone 
NAAQS. Chapters IV through XIII address specific planning elements for 
a Serious area, including emissions inventory, transportation 
conformity budgets, emissions statements, new source review (NSR), 
RACM, RFP, attainment demonstration, and contingency measures. The Plan 
also includes eight appendices providing additional information on 
emissions inventories, CARB control measures, CARB analysis of key 
mobile source regulations and programs, a mobile sources and consumer 
products RACM demonstration, and the modeled attainment demonstration, 
a modeling emissions inventory for the nonattainment area, a 
description of the conceptual model for the nonattainment area, and 
CARB's modeling protocol used for the photochemical modeling.
    Additionally, to further supplement the contingency measures 
element of the 2018 Western Nevada County Ozone Plan, CARB forwarded an 
October 26, 2020 letter from the District \22\ committing to adopt as a 
rule the most recent Architectural Coatings Suggested Control Measure 
(SCM) developed and approved by CARB to serve as a contingency measure 
that would be triggered if the area fails to meet an RFP milestone for 
the 2008 ozone NAAQS or to reach attainment by a July 20, 2021 
attainment date. In the letter forwarding this commitment, dated 
November 16, 2020, CARB commits to submit the new District rule to the 
EPA as a SIP revision within 12 months of the EPA's final action on the 
contingency measures element of the 2018 Western Nevada County Ozone 
Plan.
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    \22\ Letter dated November 16, 2020, from Richard Corey, 
Executive Officer, CARB, to John Busterud, Regional Administrator, 
EPA Region IX. CARB's letter also forwarded the District's 
commitment letter to the EPA. The District's letter is dated October 
26, 2020, from Gretchen Bennitt, NSAQMD Air Pollution Control 
Officer, to Richard Corey, CARB Executive Officer.
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    In a technical memorandum submitted by email on October 27, 2020, 
CARB provided additional information related to the motor vehicle 
emissions budgets in the 2018 Western Nevada County Ozone Plan.\23\ 
Additionally, CARB has provided a copy of the 2019 emissions inventory 
for the

[[Page 2321]]

nonattainment area,\24\ and clarifications to emissions tables in the 
Plan.\25\
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    \23\ See attachment to email dated October 27, 2020 from 
Nesamani Kalandiyur, CARB, to Khoi Nguyen and Karina O'Connor, EPA 
Region 9.
    \24\ Email dated May 14, 2020 from Earl Withycombe, CARB, to 
Khoi Nguyen, EPA Region 9, for attachment of the 2019 emission 
inventory for the nonattainment area.
    \25\ Email dated August 17, 2020 from Webster Tasat, CARB, to 
Khoi Nguyen, EPA Region 9, for clarifications of the emission 
tables.
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B. Clean Air Act Procedural Requirements for Adoption and Submission of 
SIP Revisions

    CAA sections 110(a) and 110(l) require a state to provide 
reasonable public notice and opportunity for public hearing prior to 
the adoption and submission of a SIP or SIP revision. To meet this 
requirement, every SIP submittal 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 have satisfied the applicable statutory 
and regulatory requirements for reasonable public notice and hearing 
prior to the adoption and submittal of the 2018 Western Nevada County 
Ozone Plan. On September 21, 2018, the District published a notice in 
the local newspaper of a public hearing to be held on October 22, 2018, 
for the adoption of the 2018 Western Nevada County Ozone Plan.\26\ The 
District adopted the Plan through Resolution #2018-07 at the October 
22, 2018 hearing, and directed the Executive Director to forward the 
Plan to CARB for inclusion in the California SIP.\27\
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    \26\ Affidavit of Publication from Nevada County Publishing 
Company including a copy of the proof of publication and of the 
September 21, 2018 notice for the October 22, 2018 public hearing.
    \27\ See NSAQMD Resolution #2018-07, October 22, 2018.
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    CARB also provided public notice and opportunity for public comment 
on the 2018 Western Nevada County Ozone Plan. On October 12, 2018, CARB 
released for public review its Staff Report for the Plan and published 
a notice of public meeting to be held on November 15, 2018, to consider 
adoption.\28\ At the November 15, 2018 hearing, CARB adopted the Plan 
as a revision to the California SIP, excluding those portions not 
required to be submitted to the EPA, and directed the Executive Officer 
to submit the Plan to the EPA for approval into the California SIP. On 
December 2, 2018, the Executive Officer of CARB submitted the Plan to 
the EPA, including the CARB Board resolution adopting the 2018 Western 
Nevada County Ozone Plan.\29\ On June 20, 2019, the EPA determined that 
certain portions of this submittal applicable to the 2008 ozone NAAQS 
were complete.\30\
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    \28\ Notice of Public Meeting to Consider the Ozone Attainment 
Plan for Western Nevada County, signed by Richard Corey, Executive 
Officer, CARB, October 12, 2018.
    \29\ CARB Resolution 18-36.
    \30\ Letter dated June 20, 2019, from Elizabeth Adams, Director, 
Air and Radiation Division, EPA Region IX, to Richard Corey, 
Executive Officer, CARB. The Plan was deemed complete by operation 
of law on June 2, 2019, 6 months after submittal, but the EPA 
completeness finding for the following SIP elements: Contingency 
measures for VOC and NOX; emissions statement; ozone 
attainment demonstration; and RFP demonstration for VOC and 
NOX for moderate nonattainment areas was necessary to 
stop clocks for mandatory sanctions in the Western Nevada 
nonattainment area under section 179(a) of the CAA resulting from a 
December 11, 2017 finding of failure to submit. See 82 FR 58118.
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    Based on information provided in the SIP revision summarized above, 
the EPA has determined that all hearings were properly noticed. 
Therefore, we find that the submittal of the 2018 Western Nevada County 
Ozone Plan meets the procedural requirements for public notice and 
hearing in CAA sections 110(a) and 110(l) and 40 CFR 51.102.

III. Evaluation of the 2018 Western Nevada County Ozone Plan

A. Emissions Inventories

1. Statutory and Regulatory Requirements
    CAA sections 172(c)(3) and 182(a)(1) require states to submit for 
each ozone nonattainment area a ``base year inventory'' that is a 
comprehensive, accurate, current inventory of actual emissions from all 
sources of the relevant pollutant or pollutants in the area. In 
addition, the 2008 Ozone SRR requires that the inventory year be 
selected consistent with the baseline year for the RFP demonstration, 
which is the most recent calendar year for which a complete triennial 
inventory is required to be submitted to the EPA under the Air 
Emissions Reporting Requirements.\31\
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    \31\ 2008 Ozone SRR at 40 CFR 51.1115(a) and the Air Emissions 
Reporting Requirements at 40 CFR part 51, subpart A.
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    The EPA has issued guidance on the development of base year and 
future year emissions inventories for ozone and other pollutants.\32\ 
Emissions inventories for ozone must include emissions of VOC and 
NOX and represent emissions for a typical ozone season 
weekday.\33\ States should include documentation explaining how the 
emissions data were calculated. In estimating mobile source emissions, 
states should use the latest emissions models and planning assumptions 
available at the time the SIP is developed.\34\
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    \32\ ``Emissions Inventory Guidance for Implementation of Ozone 
and Particulate Matter National Ambient Air Quality Standards 
(NAAQS) and Regional Haze Regulations,'' EPA-454/B-17-002, May 2017. 
At the time the 2018 Western Nevada County Ozone Plan was developed, 
the following EPA emissions inventory guidance applied: ``Emissions 
Inventory Guidance for Implementation of Ozone and Particulate 
Matter National Ambient Air Quality Standards (NAAQS) and Regional 
Haze Regulations,'' EPA-454-R-05-001, August 2005.
    \33\ 40 CFR 51.1115(a) and (c), and 40 CFR 51.1100(bb) and (cc).
    \34\ 80 FR 12264, at 12290 (March 6, 2015).
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    Future baseline emissions inventories must reflect the most recent 
population, employment, travel and congestion projections for the area. 
In this context, future ``baseline'' emissions inventories refer to 
emissions estimates for a given year and area that reflect rules and 
regulations and other measures that are already adopted and that 
consider expected growth. Future baseline emissions inventories are 
necessary to show the projected effectiveness of SIP control measures. 
Both the base year and future year inventories are necessary for 
photochemical modeling to demonstrate attainment.
2. Summary of State's Submission
    The 2018 Western Nevada County Ozone Plan includes base year (2011) 
and future year (2012, 2014, 2017, 2020, and 2021) baseline inventories 
for NOX and VOC for the Western Nevada County ozone 
nonattainment area. Documentation for the inventories are found in 
Chapter IV, ``Emissions Inventory Background,'' Chapter V, ``Summary of 
Emissions Inventory Methodologies,'' Appendix A, ``Emissions 
Inventories for 2011, 2012, 2014, 2017, 2020 and 2021,'' and Appendix 
F, ``Modeling Emission Inventory for the 8-Hour Ozone State 
Implementation Plan in Western Nevada County Non-attainment Area 
(WNNA).''
    The emissions inventories represent average summer day emissions, 
consistent with the observation that higher ozone levels in Western 
Nevada County typically occur from May through October. The 2011 base 
year and future year inventories in the 2018 Western Nevada County 
Ozone Plan reflect District rules and CARB regulations submitted 
through November 2016.\35\ The mobile source portions of both base year 
and projected future year inventories were developed using California's 
EPA-approved mobile source emissions model, EMFAC2014,

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for estimating on-road motor vehicle emissions.\36\
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    \35\ ``Staff Report: CARB Review of the Ozone Attainment Plan 
for Western Nevada County,'' CARB, October 12, 2018, page 6 (``CARB 
Staff Report'').
    \36\ EMFAC is short for EMission FACtor. In December 2015, the 
EPA approved EMFAC2014 for SIP development and transportation 
conformity purposes in California. 80 FR 77337 (December 14, 2015). 
EMFAC2014 was the most recently approved version of the EMFAC model 
that was available at the time of preparation of the Western Nevada 
County Ozone Attainment Plan. The EPA recently approved an updated 
version of the EMFAC model, EMFAC2017, for future SIP development 
and transportation purposes in California. 84 FR 41717 (August 15, 
2019).
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    Emissions estimates of VOC and NOX in the 2018 Western 
Nevada County Ozone Plan are grouped into three categories: (1) 
Stationary point sources, (2) areawide sources, (3) on-road and other 
mobile sources. Stationary point sources refer to larger sources that 
have a fixed geographic location, such as power plants, industrial 
engines, and oil storage tanks. This inventory includes emissions from 
stationary internal combustion engines and gasoline dispensing 
facilities; these are not inventoried individually but estimated as a 
group and reported as an aggregated total. Areawide sources are 
emissions sources occurring over a wide geographic area, such as 
consumer products and architectural coatings. The on-road sources 
include light-duty automobiles, light-, medium-, and heavy-duty trucks, 
and motorcycles. Other mobile (off-road) sources include aircraft, 
recreational boats, and off-road equipment.
    For the 2018 Western Nevada County Ozone Plan, stationary point 
source emissions for the 2011 base year emissions inventory are based 
on reported data from all stationary point sources in Western Nevada 
County using the District's annual emissions reporting program, which 
applies under District Rule 513, ``Emissions Statements and 
Recordkeeping,'' to stationary sources that emit VOC or 
NOX.\37\ Areawide sources include smaller emissions sources 
distributed across the nonattainment area. CARB and the District 
estimate emissions for areawide sources using the most recent models 
and methodologies, including publicly available emission factors and 
activity information. CARB also reviewed the growth profiles for point 
and areawide source categories and updated them as necessary to ensure 
that the emission projections are based on data that reflect historical 
trends, current conditions, and recent economic and demographic 
forecasts. Growth forecasts for most point and areawide sources were 
developed by CARB.
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    \37\ The Air Pollution Control Officer of the NSAQMD may waive 
the applicability of the reporting required by District Rule 513 for 
certain classes or categories of sources with actual emissions or 
potential to emit less than 10 tons per year of actual facility-wide 
VOC or NOX emissions if the emissions for the class or 
category of source are included in the base year and periodic 
emission inventories and the emissions are calculated using emission 
factors established by the EPA or other methods acceptable to the 
EPA. As described in Section B of this document, this approach is 
consistent with CAA section 182(a)(3)(B)(ii).
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    On-road emissions inventories in the 2018 Western Nevada County 
Ozone Plan are based on 2012 travel activity data provided by the 
California Department of Motor Vehicles. CARB provided emissions 
inventories for off-road equipment, including locomotives, pleasure 
craft and recreational vehicles, in-use off-road equipment, transport 
refrigeration units, cargo handling equipment, diesel agricultural 
equipment, and fuel storage and handling. Emissions from off-road 
sources were estimated using a suite of category-specific models or, 
where a new model was not available, the OFFROAD2007 model. A detailed 
list of the updates made to specific emissions inventory categories can 
be found in Chapter V.
    CARB developed the emission forecasts in the 2018 Western Nevada 
County Ozone Plan by applying growth and control profiles to the base 
year inventory. Growth profiles for stationary point and areawide 
sources are derived from surrogates such as economic activity, fuel 
usage, population, housing units, etc. Growth projections were obtained 
from government entities with expertise in developing forecasts for 
specific sectors, and from econometric models. Control profiles, which 
account for emissions reductions resulting from adopted rules and 
regulations, are derived from data provided by the regulatory agencies 
responsible for the affected emission categories.\38\
---------------------------------------------------------------------------

    \38\ 2018 Western Nevada County Ozone Plan, page 23.
---------------------------------------------------------------------------

    Table 1 provides a summary of the District's 2011 base year, 2012 
baseline year for modeling, and 2020 attainment year baseline VOC and 
NOX emissions estimates in tons per day (tpd) for an average 
summer day. All inventory years in the 2018 Western Nevada County Ozone 
Plan are derived from the 2011 base year inventory, except that 2012 is 
used as the baseline year for attainment modeling. These inventories 
provide the basis for the control measure analysis and the attainment 
demonstration in the Plan. Based on the inventory for 2011, mobile 
sources are the predominant sources for both VOC and NOX 
emissions. For a more detailed discussion of the inventories, see 
Appendix A of the Plan.

                 Table 1--Western Nevada 2011 Base Year, 2012 Baseline Year for Modeling, and 2020 Attainment Year Emissions Inventories
                                                            [Summer planning inventory, tpd]
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                       2011                            2012                            2020
                        Category                         -----------------------------------------------------------------------------------------------
                                                                VOC             NOX             VOC             NOX             VOC             NOX
--------------------------------------------------------------------------------------------------------------------------------------------------------
Stationary..............................................          0.7620          0.0999          0.7006          0.0997          0.7843          0.0918
Area Sources............................................          1.4109          0.1452          1.3946          0.1349          1.5150          0.1377
On-Road and Other Mobile Sources........................          3.3227          5.4415          3.1131          4.9124          1.9559          2.8886
                                                         -----------------------------------------------------------------------------------------------
    Total for Western Nevada County Nonattainment Area..          5.4956          5.6866          5.2083          5.1470          4.2552          3.1181
--------------------------------------------------------------------------------------------------------------------------------------------------------
Source: 2018 Western Nevada County Ozone Plan, Appendix A. The sum of the emissions values may not equal the total shown due to rounding of the numbers.

3. The EPA's Review of the State's Submission
    We have reviewed the 2011 base year emissions inventory in the 2018 
Western Nevada County Ozone Plan and the inventory methodologies used 
by the District and CARB for consistency with CAA requirements and EPA 
guidance. First, as required by EPA regulation, we find that the 2011 
inventory includes estimates for VOC and NOX for a typical 
ozone season

[[Page 2323]]

weekday, and that the Plan provides adequate documentation explaining 
how the emissions are calculated.
    Second, we find that the 2011 base year emissions inventory in the 
Plan reflects appropriate emissions models and methodologies, and, 
therefore, represents a comprehensive, accurate, and current inventory 
of actual emissions during that year in the Western Nevada County 
nonattainment area. Therefore, the EPA is proposing to approve the 2011 
emissions inventory in the 2018 Western Nevada County Ozone Plan as 
meeting the requirements for a base year inventory set forth in CAA 
section 182(a)(1) and 40 CFR 51.1115.
    With respect to future year baseline projections, we have reviewed 
the growth and control factors and find them acceptable and conclude 
that the future baseline emissions projections in the 2018 Western 
Nevada County Ozone Plan reflect appropriate calculation methods and 
the latest planning assumptions.
    Furthermore, we note that the future year baseline projections take 
into account emissions reductions from control measures in adopted 
state and local rules and regulations. As a general matter, the EPA 
will approve a SIP revision that takes emissions reduction credit for 
such control measures only where the EPA has approved the control 
measures as part of the SIP. See Appendix B of the 2018 Western Nevada 
County Ozone Plan, ``CARB Control Measures, 1985 to 2016,'' 2018 
Western Nevada County Ozone Plan for the list of control measures.
    With respect to mobile sources, the EPA has taken action in recent 
years to approve CARB mobile source regulations into the California 
SIP.\39\ We therefore find that the future year baseline projections in 
the 2018 Western Nevada County Ozone Plan are properly supported by 
SIP-approved stationary and mobile source control measures.
---------------------------------------------------------------------------

    \39\ See 81 FR 39424 (June 16, 2016), 82 FR 14446 (March 21, 
2017), and 83 FR 23232 (May 18, 2018).
---------------------------------------------------------------------------

B. Emissions Statements

1. Statutory and Regulatory Requirements
    Section 182(a)(3)(B)(i) of the Act requires each state to submit a 
SIP revision requiring owners or operators of stationary sources of VOC 
or NOX to provide the state with statements of actual 
emissions from such sources. Statements must be submitted at least 
every year and must contain a certification that the information 
contained in the statement is accurate to the best knowledge of the 
individual certifying the statement. Section 182(a)(3)(B)(ii) of the 
Act allows states to waive the emissions statement requirement for any 
class or category of stationary sources that emit less than 25 tpy of 
VOC or NOX, if the state provides an inventory of emissions 
from such class or category of sources as part of the base year or 
periodic inventories required under CAA sections 182(a)(1) and 
182(a)(3)(A), based on the use of emission factors established by the 
EPA or other methods acceptable to the EPA.
    The preamble of the 2008 Ozone SRR states that if an area has a 
previously approved emissions statement rule for the 1997 ozone NAAQS 
or the 1-hour ozone NAAQS that covers all portions of the nonattainment 
area for the 2008 ozone NAAQS, such rule should be sufficient for 
purposes of the emissions statement requirement for the 2008 ozone 
NAAQS.\40\ The state should review the existing rule to ensure it is 
adequate and, if so, may rely on it to meet the emission statement 
requirement for the 2008 ozone NAAQS. Where an existing emissions 
statement program is still adequate to meet the requirements of this 
rule, states can provide the rationale for that determination to the 
EPA in a written statement in the SIP to meet this requirement. States 
should identify the various requirements and how each is met by the 
existing emissions statement program. Where an emissions statement 
requirement is modified for any reason, states must provide the 
revision to the emissions statement as part of its SIP.
---------------------------------------------------------------------------

    \40\ 80 FR 12264, at 12291 (March 6, 2015).
---------------------------------------------------------------------------

2. Summary of the State's Submission
    The 2018 Western Nevada County Ozone Plan addresses compliance with 
the emissions statement requirement in CAA section 182(a)(3)(B) for the 
2008 ozone NAAQS by reference to District Rule 513, ``Emission 
Statements and Recordkeeping,'' which, among other things, requires 
emissions reporting from all stationary sources of NOX and 
VOC greater than or equal to 10 tpy. The EPA approved District Rule 513 
as a revision to the California SIP on June 21, 2017, finding that Rule 
513 fulfills the relevant emissions statement requirements of CAA 
section 182(a)(3)(B)(i).\41\
---------------------------------------------------------------------------

    \41\ 82 FR 28240.
---------------------------------------------------------------------------

3. The EPA's Review of the State's Submission
    We find that District Rule 513 applies within the entire ozone 
nonattainment area; applies to all stationary sources emitting 
NOX and VOC, except those emitting less than 10 tpy for 
which the District has waived the requirement (consistent with CAA 
section 182(a)(3)(B)(ii)); and requires reporting, on an annual basis, 
of total emissions of VOC and NOX. Also, as required under 
CAA section 182(a)(3)(B), District Rule 513 requires certification that 
the information provided to the District is accurate to the best 
knowledge of the individual certifying the emissions data.
    Therefore, for the reasons described in the preceding paragraph, we 
propose to find that District Rule meets the emissions statement 
requirements for the 2008 ozone NAAQS under CAA section 182(a)(3)(B).

C. Reasonably Available Control Measures Demonstration

1. Statutory and Regulatory Requirements
    CAA section 172(c)(1) requires that each attainment plan provide 
for the implementation of all RACM as expeditiously as practicable 
(including such reductions in emissions from existing sources in the 
area as may be obtained through implementation of reasonably available 
control technology (RACT)), and also provide for attainment of the 
NAAQS. The 2008 Ozone SRR requires that, for each nonattainment area 
required to submit an attainment demonstration, the state concurrently 
submit a SIP revision demonstrating that it has adopted all RACM 
necessary to demonstrate attainment as expeditiously as practicable and 
to meet any RFP requirements.\42\
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    \42\ 40 CFR 51.1112(c).
---------------------------------------------------------------------------

    The EPA has previously provided guidance interpreting the RACM 
requirement in the General Preamble for the Implementation of the CAA 
Amendments of 1990 (``General Preamble'') and in a memorandum entitled 
``Guidance on the Reasonably Available Control Measure Requirement and 
Attainment Demonstration Submissions for Ozone Nonattainment Areas.'' 
\43\ In short, to address the requirement to adopt all RACM, states 
should consider all potentially reasonable control measures for source 
categories in the nonattainment area to determine whether they are 
reasonably available for implementation in that area and whether they 
would, if implemented individually or collectively, advance the area's

[[Page 2324]]

attainment date by one year or more.\44\ Any measures that are 
necessary to meet these requirements that are not already either 
federally promulgated, or part of the state's SIP, must be submitted in 
enforceable form as part of the state's attainment plan for the 
area.\45\
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    \43\ See General Preamble, 57 FR 13498 at 13560 (April 16, 1992) 
and memorandum dated November 30, 1999, from John Seitz, Director, 
OAQPS, to Regional Air Directors, titled ``Guidance on the 
Reasonably Available Control Measure Requirement and Attainment 
Demonstration Submissions for Ozone Nonattainment Areas.''
    \44\ Id. See also 44 FR 20372 (April 4, 1979), and memorandum 
dated December 14, 2000, from John S. Seitz, Director, OAQPS, to 
Regional Air Directors, titled ``Additional Submission on RACM From 
States with Severe One-Hour Ozone Nonattainment Area SIPs.''
    \45\ For ozone nonattainment areas classified as Moderate or 
above, CAA section 182(b)(2) also requires implementation of RACT 
for all major sources of VOC and for each VOC source category for 
which the EPA has issued a control techniques guideline. CAA section 
182(f) requires that RACT under section 182(b)(2) also apply to 
major stationary sources of NOX. In Serious areas, a 
major source is a stationary source that emits or has the potential 
to emit at least 50 tpy of VOC or NOX (see CAA section 
182(c) and (f)). Under the 2008 Ozone SRR, states were required to 
submit SIP revisions meeting the RACT requirements of CAA sections 
182(b)(2) and 182(f) no later than 24 months after the effective 
date of designation for the 2008 Ozone NAAQS and to implement the 
required RACT measures as expeditiously as practicable but no later 
than January 1 of the 5th year after the effective date of 
designation (see 40 CFR 51.1112(a)). California submitted the CAA 
section 182 RACT SIP for Western Nevada County for the 2008 ozone 
NAAQS on June 7, 2018. Although Western Nevada County was classified 
as Moderate nonattainment for the 2008 ozone NAAQS at the time of 
submittal, the RACT SIP evaluated the area for compliance with 
applicable RACT requirements based on the 50 tpy Serious major 
source thresholds, in anticipation of the area's reclassification to 
the higher classification. The EPA found this submission complete on 
November 29, 2018 (see letter dated November 29, 2018 from Elizabeth 
Adams, Acting Director, Air Divison, EPA Region IX, to Richard 
Corey, Executive Officer, California Air Resources Board, and 
finalized the RACT SIP submission on January 15, 2020 (85 FR 2313).
---------------------------------------------------------------------------

2. Summary of the State's Submission
    For the 2018 Western Nevada County Ozone Plan, the District and 
CARB each undertook a process to identify and evaluate potential RACM 
that could contribute to expeditious attainment of the 2008 ozone NAAQS 
in Western Nevada County. We describe each agency's efforts below.
a. District's RACM Analysis
    The District's RACM demonstration for the 2008 ozone NAAQS is 
described in Chapter X, ``Reasonably Available Control Measures 
Demonstration,'' of the 2018 Western Nevada County Ozone Plan. This 
discussion summarizes the District's analysis of potential additional 
control measures for stationary sources conducted in the District's 
RACT SIP,\46\ and describes additional controls in place for 
``areawide'' source categories, such as architectural and automotive 
coatings. Chapter X and Appendices B-D discuss CARB's mobile source and 
consumer products RACM assessment. The District concludes that there 
are no additional control measures reasonably available in the area 
that can advance attainment by a year or more.
---------------------------------------------------------------------------

    \46\ The EPA approved the District's RACT SIP on January 15, 
2020. 85 FR 2313.
---------------------------------------------------------------------------

    The District's RACM analysis builds upon a foundation of District 
rules developed for earlier ozone plans and approved as part of the 
SIP.\47\ The District has adopted rules to address various source 
categories of NOX and VOC. We provide a list of the 
District's NOX and VOC rules approved into the California 
SIP in Table 1 of our December 3, 2020 memorandum to file in the docket 
for this proposed action. The SIP-approved District VOC or 
NOX rules listed in Table 1 of our memorandum establish 
emission limits or other types of emissions controls for a wide range 
of sources, including incinerator burning, orchard or citrus heaters, 
fossil fuel steam generator facilities, gas stations, and more. These 
rules have already provided significant and ongoing reductions toward 
attainment of the 2008 ozone NAAQS by 2021.
---------------------------------------------------------------------------

    \47\ 2018 Western Nevada County Ozone Plan, page 42.
---------------------------------------------------------------------------

    Tables 2 and 3 of the December 3, 2020 memorandum provide a 
crosswalk of the area's top-emitting stationary and area source 
categories of NOX and VOC with related District control 
rules. As shown in these tables, the area's 2020 stationary and area 
source emissions inventory includes about 0.23 tpd of NOX 
and 2.20 tpd of VOC. The top NOX source categories for this 
year are residential fuel combustion (0.13 tpd; 4.26 percent of 2020 
inventory) and service/commercial fuel combustion (0.04 tpd; 1.25 
percent of 2020 inventory); all other categories each represent less 
than 1 percent of the 2020 inventory.\48\ The top VOC source categories 
for this year are consumer products (0.44 tpd; 10.28 percent of 2020 
inventory), asphalt paving/roofing (0.38 tpd; 8.98 percent of 2020 
inventory), and architectural coatings (0.32 tpd; 7.55 percent of 2020 
inventory).
---------------------------------------------------------------------------

    \48\ For a further breakdown of the area's NOX and 
VOC sources, see Table 3 of the EPA's December 3, 2020 memorandum to 
file.
---------------------------------------------------------------------------

    The District's October 26, 2020 commitment letter for contingency 
measures includes further analysis of potential additional controls for 
regulated high-emission source categories. As mentioned above, the two 
largest NOX source categories are residential fuel 
combustion and service/commercial fuel combustion. For residential fuel 
combustion, the District evaluated Sacramento Metropolitan Air Quality 
Management District (SMAQMD) Rule 414 for water heaters, boilers, and 
process heaters rated less than a million BTU per hour. Based on its 
analysis, and considering especially the low population in the 
nonattainment area, the District concluded that potential cumulative 
reductions in NOX from a similar rule in the District would 
produce only about 0.0005 tpd each year, and that these reductions 
would occur too slowly to make any meaningful difference in attainment. 
For service/commercial fuel combustion, the District evaluated SMAQMD 
Rule 419 for miscellaneous combustion units. The District concluded 
that emission reductions from applying Rule 419 controls in the area 
would be approximately zero, because applying the rule would not be 
feasible for two of the three sources in the nonattainment area that 
would be subject to the rule and would not result in a more stringent 
emissions limit for the last applicable source in the nonattainment 
area. For VOC reductions, the District evaluated state measures for 
architectural coatings and automotive coatings,\49\ and found that 
reductions would be equivalent to 0.010 tpd and 0.003 tpd, 
respectively. The District found that the estimated reductions for 
automotive coatings was negligible and not cost effective but committed 
to adopting a rule for architectural coatings as a contingency 
measure.\50\
---------------------------------------------------------------------------

    \49\ Architectural coatings is Western Nevada County's third 
largest VOC source category. The largest VOC source categories in 
the area are consumer products and asphalt paving/roofing, and they 
are already regulated, respectively, by multiple CARB regulations 
and District Rule 227. See Table 3 of our December 3, 2020 
memorandum to file.
    \50\ The emission reductions from the adopting an architectural 
coatings rule for VOC (0.010 tpd) is less than the value needed to 
advance attainment by a year for VOC (0.075 tpd), as calculated 
below in Section III.C.3.
---------------------------------------------------------------------------

    Transportation Control Measures (TCMs) are projects that reduce air 
pollutants from transportation sources by reducing vehicle use, traffic 
congestion, or vehicle miles traveled. The Nevada County Regional 
Transportation Plan 2015-2035 (``Transportation Plan''), prepared by 
NCTC in January 2018, summarizes and highlights TCMs in Nevada County, 
including the Western portion of Nevada County, and is included in the 
docket for this action. Sample measures in Western Nevada County are 
included within the TCM categories of CAA section 108(f)(1)(A). They 
include proposed bikeways, for example, in Grass Valley,\51\ a 511 
traveler

[[Page 2325]]

information system that provides information on ridesharing and directs 
drivers to other regional resources for carpools and vanpools,\52\ and 
programs for improved public transit,\53\ including improvements and 
maintenance for bus stops and shelters.
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    \51\ Transportation Plan, Appendix D, page D-1.
    \52\ Transportation Plan, page 126.
    \53\ Transportation Plan, Tables 42-46.
---------------------------------------------------------------------------

    As explained above, the District identified potential candidate 
measures for RACM based upon categories with high NOX and 
VOC emissions and relevant local or state measures. This analysis was 
included in the District's commitment letter for contingency measures 
and is further described in Section III.F.2. Based on its evaluation of 
all available measures and the NOX-limited nature of the 
nonattainment area, the District concludes that the District's existing 
rules for stationary and area sources are generally as stringent as, or 
more stringent than the analogous rules in other districts. Further, 
the District concludes that, based on its comprehensive review and 
evaluation of potential candidate measures, the District meets the RACM 
requirement for the 2008 ozone NAAQS for all sources under the 
District's jurisdiction.
b. CARB's RACM Analysis
    CARB's RACM analysis is contained in Chapter X as well as 
Appendices B-D of the 2018 Western Nevada County Ozone Plan. CARB's 
RACM analysis provides a general description of CARB's existing mobile 
source programs. A more detailed description of CARB's mobile source 
control program, including a comprehensive table listing on- and off-
road mobile source regulatory actions taken by CARB since 1985, is 
contained in Appendix A. The RACM assessment contains CARB's evaluation 
of mobile source and other statewide control measures that reduce 
emissions of NOX and VOC in Western Nevada County.
    Source categories for which CARB has primary responsibility for 
reducing emissions in California include most new and existing on- and 
off-road engines and vehicles, motor vehicle fuels, and consumer 
products.
    Given the need for substantial emissions reductions from mobile and 
area sources to meet the NAAQS in California nonattainment areas, CARB 
has established stringent control measures for on-road and off-road 
mobile sources and the fuels that power them. California has authority 
under CAA section 209 (subject to a waiver by the EPA) to adopt and 
implement new emission standards for many categories of on-road 
vehicles and engines, and new and in-use off-road vehicles and engines.
    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.\54\
---------------------------------------------------------------------------

    \54\ 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 inspection and maintenance program at 75 FR 38023 (July 1, 
2010).
---------------------------------------------------------------------------

    CARB's Consumer Products Program has established regulations that 
limit VOC emissions from 129 consumer product categories, which apply 
in Western Nevada County.\55\ The EPA has approved many CARB measures 
into the California SIP that limit VOC emissions from a wide array of 
products, including antiperspirants and deodorants, aerosol coating 
products, and other consumer products.\56\
---------------------------------------------------------------------------

    \55\ 2018 Western Nevada County Ozone Plan, page 51 and Appendix 
D, ``Reasonably Available Control Measures Assessment for Mobile 
Sources and Consumer Products.''
    \56\ CARB's consumer product measures are found in Title 17 
California Code of Regulations section 94500 et seq. The compilation 
of such measures that have been approved into the California SIP, 
including Federal Register citations, is available at: https://www.epa.gov/sips-ca/epa-approved-regulations-california-sip. EPA's 
most recent approval of amendments to California's consumer products 
regulations was in 2014. 79 FR 62346 (October 17, 2014).
---------------------------------------------------------------------------

    CARB's RACM analysis determines that, with the current mobile 
source program and proposed measures, there are no additional RACM that 
would advance attainment of the 2008 ozone NAAQS in Western Nevada 
County. As a result, CARB concludes that California's mobile source 
programs fully meet the RACM requirement.\57\
---------------------------------------------------------------------------

    \57\ Appendix VI-A, Attachment VI-A-3, page VI-A-106.
---------------------------------------------------------------------------

3. The EPA's Review of the State's Submission
    As described above and in our December 3, 2020 memorandum to file 
in the docket for this proposed action, the District has implemented 
rules to reduce VOC and NOX emissions from stationary 
sources in the Western Nevada nonattainment area. For the 2018 Western 
Nevada County Ozone Plan, the District indicates that its ozone 
precursor control strategy focuses on NOX emission 
reductions due to the NOX-limited nature of the 
nonattainment area.\58\
---------------------------------------------------------------------------

    \58\ 2018 Western Nevada County Ozone Plan, page 41. As 
explained in Section III.D.2.a of this document, Western Nevada 
County is ``NOX limited'' because ozone formation in the 
area is driven primarily by NOX emissions. As a result, 
reducing NOX emissions is more effective for reducing 
ozone than reducing VOC emissions.
---------------------------------------------------------------------------

    The District evaluated a range of potentially available measures 
and was unable to find a combination of potential additional control 
measures for RACM. The EPA further calculated the additional reductions 
that would be necessary to advance attainment by a year. Subtracting 
the District's 2020 attainment year emissions inventory from the 2019 
emissions inventory yields a difference of 0.21 tpd NOX and 
0.075 tpd VOC, equivalent to the reductions needed to advance 
attainment by a year.\59\ Based on our review of the District's 
analysis, we agree that no additional control measures are available 
for stationary and area source categories in the nonattainment area 
that would provide the emissions reductions needed to advance 
attainment by a year.
---------------------------------------------------------------------------

    \59\ The Plan's RACM analysis incorrectly identifies the 
necessary year-to-year reductions as 0.06 tpd of VOC and 0.23 tpd of 
NOX, based on a comparison of 2020 and 2021 inventories. 
Given the small discrepancy in these numbers, relative to the 
emission reductions available in the area, we find that the 
District's RACM analysis is adequately supported.
---------------------------------------------------------------------------

    With respect to mobile sources, CARB's current program addresses 
the full range of mobile sources in the Western Nevada County 
nonattainment area through regulatory programs for both new and in-use 
vehicles. With respect to TCMs, we find that the TCMs being implemented 
in Western Nevada County (i.e., the TCMs described in the 
Transportation Plan) are inclusive of all TCM RACM to be reasonably 
justified and supported.
    We also find that CARB's consumer products program comprehensively 
addresses emissions from consumer products in the Western Nevada County 
nonattainment area. CARB measures are more stringent than the EPA's 
consumer products regulation promulgated in 1998,\60\ and generally 
exceed the controls in place throughout other areas of the country.
---------------------------------------------------------------------------

    \60\ 63 FR 48819 (September 11, 1998).
---------------------------------------------------------------------------

    Based on our review of these RACM analyses and the District's and 
CARB's adopted rules, we propose to find that there are, at this time, 
no additional RACM (including RACT) that would advance attainment of 
the 2008 ozone NAAQS in Western Nevada County. For the foregoing 
reasons, we propose to find that the 2018 Western Nevada

[[Page 2326]]

County Ozone Plan provides for the implementation of all RACM as 
required by CAA section 172(c)(1) and 40 CFR 51.1112(c).

D. Attainment Demonstration

1. Statutory and Regulatory Requirements
    Section 182(c)(2)(A) of the CAA requires that a plan for an ozone 
nonattainment area classified Serious or above include a 
``demonstration that the plan . . . will provide for attainment of the 
ozone [NAAQS] by the applicable attainment date. This attainment 
demonstration must be based on photochemical grid modeling or any other 
analytical method determined . . . to be at least as effective.'' The 
attainment demonstration predicts future ambient concentrations for 
comparison to the NAAQS, making use of available information on 
measured concentrations, meteorology, and current and projected 
emissions inventories of ozone precursors, including the effect of 
control measures in the Plan.
    Areas classified Serious for the 2008 ozone NAAQS must demonstrate 
attainment as expeditiously as practicable, but no later than 9 years 
after the effective date of designation as nonattainment. Western 
Nevada County was designated as a Marginal nonattainment area for the 
2008 ozone NAAQS effective July 20, 2012.\61\ It was subsequently 
reclassified to Moderate,\62\ and then to Serious,\63\ and accordingly 
must demonstrate attainment of the standards by no later than July 20, 
2021.\64\ An attainment demonstration must show attainment of the 
standards for a full calendar year before the attainment date, so in 
practice, Serious nonattainment areas must demonstrate attainment for 
the attainment year 2020.
---------------------------------------------------------------------------

    \61\ 77 FR 30088 (May 21, 2012).
    \62\ 81 FR 26697 (April 4, 2015).
    \63\ 84 FR 44238 (August 23, 2019).
    \64\ Nine years after the initial designation, 84 FR 44244.
---------------------------------------------------------------------------

    The EPA's recommended procedures for modeling ozone as part of an 
attainment demonstration are contained in ``Modeling Guidance for 
Demonstrating Attainment of Air Quality Goals for Ozone, 
PM2.5, and Regional Haze'' (``Modeling Guidance'').\65\ The 
Modeling Guidance includes recommendations for a modeling protocol, 
model input preparation, model performance evaluation, use of model 
output for the numerical NAAQS attainment test, and modeling 
documentation. Air quality modeling is performed using meteorology and 
emissions from a base year, and the predicted concentrations from this 
base case modeling are compared to air quality monitoring data from 
that year to evaluate model performance. Once the model performance is 
determined to be acceptable, future year emissions are simulated with 
the model. The relative (or percent) change in modeled concentration 
due to future emissions reductions provides a relative response factor 
(RRF). Each monitoring site's RRF is applied to its monitored base year 
design value to give the future design value for comparison to the 
NAAQS. The Modeling Guidance also recommends supplemental air quality 
analyses, which may be used as part of a weight of evidence (WOE) 
analysis. A WOE analysis corroborates the attainment demonstration by 
considering evidence other than the main air quality modeling 
attainment test, such as trends and additional monitoring and modeling 
analyses.
---------------------------------------------------------------------------

    \65\ ``Modeling Guidance for Demonstrating Attainment of Air 
Quality Goals for Ozone, PM2.5, and Regional Haze,'' EPA 
454/R-18-009, EPA OAQPS, November 2018; available at https://www.epa.gov/scram/state-implementation-plan-sip-attainment-demonstration-guidance. See also December 2014 draft of this 
guidance, available at https://www3.epa.gov/ttn/scram/guidance/guide/Draft-O3-PM-RH-Modeling_Guidance-2014.pdf. The December 2014 
draft guidance was available during development of the Plan; the 
final version differs mainly in organization, and in updates to the 
regional haze portion and to other document references. Additional 
EPA modeling guidance can be found in 40 CFR 51 Appendix W, 
Guideline on Air Quality Models, 82 FR 5182 (January 17, 2017); 
available at https://www.epa.gov/scram/clean-air-act-permit-modeling-guidance.
---------------------------------------------------------------------------

    Unlike the RFP demonstration and the emissions inventory 
requirements, the 2008 SRR does not specify that a specific year must 
be used for the modeled base year for the attainment demonstration. The 
Modeling Guidance also does not require a particular year to be used as 
the base year for 8-hour ozone plans.\66\ The Modeling Guidance states 
that the most recent year of the National Emissions Inventory may be 
appropriate for use as the base year for modeling, but that other years 
may be more appropriate when considering meteorology, transport 
patterns, exceptional events, or other factors that may vary from year 
to year.\67\ Therefore, the base year used for the attainment 
demonstration need not be the same year used to meet the requirements 
for emissions inventories and RFP.
---------------------------------------------------------------------------

    \66\ Modeling Guidance section 2.7.1, 35.
    \67\ Id.
---------------------------------------------------------------------------

    With respect to the list of adopted measures, CAA section 172(c)(6) 
requires that nonattainment area plans include enforceable emissions 
limitations, and such other control measures, means or techniques 
(including economic incentives such as fees, marketable permits, and 
auctions of emission rights), as well as schedules and timetables for 
compliance, as may be necessary or appropriate to provide for timely 
attainment of the NAAQS.\68\ Under the 2008 Ozone SRR, all control 
measures needed for attainment must be implemented no later than the 
beginning of the attainment year ozone season.\69\ The attainment year 
ozone season is defined as the ozone season immediately preceding a 
nonattainment area's maximum attainment date; \70\ in the case of the 
Western Nevada County area, the attainment year is 2020.
---------------------------------------------------------------------------

    \68\ See also CAA section 110(a)(2)(A).
    \69\ 40 CFR 51.1108(d).
    \70\ 40 CFR 51.1100(h).
---------------------------------------------------------------------------

2. Summary of the State's Submission
a. Photochemical Modeling
    CARB performed the air quality modeling for the Western Nevada 
Ozone Plan, and has included documentation of this modeling within the 
Plan and the Staff Report that accompanied CARB's submittal of the 2018 
Ozone Plan (``CARB Staff Report'').\71\ The modeling relies on a 2012 
base year and projects design values for 2020. The Plan's modeling 
protocol is in Appendix H of the 2018 Western Nevada County Ozone Plan 
and contains all the elements recommended in the Modeling Guidance, 
with the exception of a conceptual description and a WOE analysis, 
which appear in the CARB Staff Report.\72\ The area is dominated by 
transport of ozone and precursors from the Sacramento Metro 
nonattainment area, which has a much higher population and emissions 
about twenty times larger.\73\ Concentrations at Western Nevada 
County's single monitor, Grass Valley, have paralleled those in the 
eastern portions of the Sacramento area for the past two decades. The 
Western Nevada County area has multiple valleys extending from 
southwest to northeast into the higher elevations of the Sierra Nevada 
mountain range. Upslope-downslope

[[Page 2327]]

flows in those valleys lead to recirculation of pollutants, and the 
Sierra crest tends to block flow further east; both of these enhance 
ozone concentrations. The area is mainly rural, with generally low 
NOX emissions and relatively high VOC emissions, so that 
ozone formation there is expected to be NOX-limited.\74\ The 
recirculation and the lack of NOX emissions prevents the 
removal of ozone through the NOX titration process. This 
allows carryover of pollution from the previous day, leading to high 
ozone values that persist through the night at the start of the 
following morning, unlike the typical pattern for areas with ozone 
caused by locally generated emissions.\75\
---------------------------------------------------------------------------

    \71\ ``Staff Report: CARB Review of the Ozone Attainment Plan 
for Western Nevada County,'' CARB, October 12, 2018.
    \72\ CARB Staff Report, 2 and 20.
    \73\ The summer 2020 emissions inventories for the Sacramento 
nonattainment area and Western Nevada Nonattainment NOX 
are 63.2 and 3.1 tpd, respectively; VOC emissions are 86.8 and 4.3 
tpd, respectively, 2018 Western Nevada County Ozone Plan, E-27. The 
2020 Sacramento County population is 1,543,522, about 14 times the 
size of the Nevada County population of 104,343, Almanac of 
Emissions & Air Quality, California Air Resources Board, 2013, 
Appendix C, available at https://ww2.arb.ca.gov/our-work/programs/resource-center/technical-assistance/air-quality-and-emissions-data/almanac.
    \74\ Ozone is generally NOX-limited in rural areas 
and downwind suburban areas. See pages 24 and 38 of CARB Staff 
Report and also Chapter 2.1 Ozone Chemistry, ``Final Ozone NAAQS 
Regulatory Impact Analysis,'' March 2008, EPA Office of Air Quality 
Planning and Standards, available at https://www3.epa.gov/ttnecas1/regdata/RIAs/452_R_08_003.pdf. The term ``NOX-limited'' 
can mean either that reducing NOX emissions decrease 
ozone (as opposed to increasing it); or that reducing NOX 
is much more effective at decreasing ozone than is reducing VOC. As 
discussed below and on page 42 of CARB Staff Report, ozone in 
Western Nevada County are decreased by reducing NOX 
emissions.
    \75\ 2018 Western Nevada Ozone Plan, page H-16.
---------------------------------------------------------------------------

    The modeling and the modeled attainment demonstration are described 
in Chapter XII of the 2018 Western Nevada County Ozone Plan and in more 
detail in Appendix E, which provides a description of model input 
preparation procedures and various model configuration options. 
Appendix F of the 2018 Western Nevada County Ozone Plan provides the 
coordinates of the modeling domain and thoroughly describes the 
development of the modeling emissions inventory, including its chemical 
speciation, its spatial and temporal allocation, its temperature 
dependence, and quality assurance procedures. The modeling analysis 
uses version 5 of the Community Multiscale Air Quality (CMAQ) 
photochemical model developed by the EPA, using the 2007 version of the 
Statewide Air Pollution Research Center (SAPRC07) chemical mechanism. 
The CMAQ modeling domain covers most of California, nested within a 
domain covering the entire state. To prepare meteorological inputs for 
CMAQ, CARB used the Weather and Research Forecasting model version 3.6 
(WRF) from the National Center for Atmospheric Research. The WRF domain 
covers the entire state of California, nested within a domain covering 
most of the western United States. The modeling used inputs prepared 
from routinely available meteorological and air quality data collected 
during 2012. Those data cover May through September, a period that 
spans the period of highest ozone concentrations in Western Nevada 
County. The Modeling Guidance recognizes both CMAQ and WRF as 
technically sound, state-of-the-art models. The areal extent and the 
horizontal and vertical resolution used in these models is adequate for 
modeling Western Nevada County ozone.
    The WRF meteorological model results and performance statistics are 
described in Appendix E.\76\ The performance evaluation focuses on a 
smaller area than the full domain but encompassing the Western Nevada 
County nonattainment area and the greater Sacramento area, with special 
attention on the winds for high ozone days. There is a slight 
overprediction of wind speeds and underprediction of temperatures in 
the eastern portion of the nonattainment area, but overall, modeled 
wind speed, wind direction, and temperature all track observations very 
well, as shown in scatter and time series plots. The modeling 
replicates some important meteorological features such as the upslope-
downslope flows in the Sierra Nevada foothills, and the ``Schulz eddy'' 
known to occur in the greater Sacramento area. The 2018 Western Nevada 
County Ozone Plan states that the bias and error are relatively small 
and are comparable to those seen in previous meteorological modeling of 
central California and cited in the Plan. In summary, the 2018 Western 
Nevada County Ozone Plan's meteorological modeling performance 
statistics appear satisfactory.
---------------------------------------------------------------------------

    \76\ Appendix E, section 3.2, E-17; also, refer to supplemental 
figures S.1-S.11, E-48.
---------------------------------------------------------------------------

    Ozone model performance statistics are described in the 2018 
Western Nevada County Ozone Plan at Appendix E.\77\ Appendix E includes 
tables of statistics recommended in the Modeling Guidance for 8-hour 
and 1-hour daily maximum ozone concentrations. Predicted concentrations 
have a small negative bias (underprediction) of 4.1 ppb.\78\ This 
compares well to the range of 2.7 to 10.8 ppb seen in a previous 
modeling exercise for central California that is cited in the Plan; 
bias and error are both at the low end of those seen in a comparative 
study of 69 modeling exercises.\79\ The Plan's supplemental figures 
with hourly time series show good performance; although some individual 
daily ozone peaks are missed in May and September, there are days for 
which the modeled highest concentration is close to the value of the 
highest observed concentration. This supports the adequacy of the model 
for use in the attainment demonstration.
---------------------------------------------------------------------------

    \77\ Appendix E, section 5.2, E-32; also, refer to supplemental 
figures S.12-S.16, E-55.
    \78\ Because only the relative response to emissions changes 
(RRF) from the modeling is used, the underprediction of absolute 
ozone concentrations does not mean that future concentrations will 
be underestimated.
    \79\ Simon, H., Baker, K.R., Phillips, S, 2012, Compilation and 
Interpretation of Photochemical Model Performance Statistics 
Published Between 2006 and 2012, Atmos. Environ., 61, 124-139. 
doi:10.1016/j.atmosenv.2012.07.012.
---------------------------------------------------------------------------

    As noted in the 2018 Western Nevada County Ozone Plan's modeling 
protocol, the Modeling Guidance recognizes that limited time and 
resources can constrain the extent of the diagnostic and dynamic 
evaluation of model performance undertaken.\80\ The Plan describes a 
dynamic evaluation \81\ in which model predictions of ozone 
concentrations for weekdays and weekends were compared to each other 
and to observed concentrations. This evaluation provides useful 
information on how well the model simulates the effect of emissions 
changes, since NOX emissions are lower on weekends than on 
weekdays, but the days are otherwise similar. The modeled ozone 
decreased in response to the weekend NOX reductions, which 
matches the observed decrease, and indicates that the model is 
simulating the chemistry correctly. The Plan also contains results of 
an analysis of weekday and weekend ozone concentrations during the 
2000-2015 period. It notes a shift over the years toward lower ozone on 
weekends, especially after 2010, showing that lower NOX 
emissions lead to lower ozone concentrations.\82\ Both the modeling and 
the observed weekday-weekend trends show that ozone responds to 
NOX emissions reductions, i.e., that ozone formation is 
NOX-limited. The modeled 2012 base year is also 
NOX-limited, with the weekday-weekend difference comparable 
to those seen historically. This match lends confidence to the 
modeling.
---------------------------------------------------------------------------

    \80\ 2018 Western Nevada County Ozone Plan, Appendix H, 
``Modeling Protocol,'' H-31; Modeling Guidance, 63.
    \81\ See ``Diagnostic Evaluation'' in Appendix E section 5.2.1, 
E-36.
    \82\ 2018 Western Nevada County Ozone Plan, Appendix E, E-40.
---------------------------------------------------------------------------

    After accepting the model performance for the 2012 base case, CARB 
used the model to develop RRFs for the attainment demonstration.\83\ 
This entailed running the model with the same meteorological inputs as 
before, but with emissions inventories to reflect

[[Page 2328]]

the expected changes between the 2012 base year and the 2020 future 
year. These modeling inventories exclude ``emissions events which are 
either random and/or cannot be projected to the future . . . wildfires, 
and events such as the [San Francisco Bay Area] Chevron refinery 
fire.'' \84\ The future inventories project the base year with these 
exclusions into the future by including the effect of economic growth 
and emissions control measures.
---------------------------------------------------------------------------

    \83\ Id. at 57, and Appendix H, ``Modeling Protocol,'' section 
10.3, H-34.
    \84\ Id. at Appendix H, H-33; and, Appendix F, ``Modeling 
Emissions Inventory,'' F-35. To include the fires in the base year 
but not the future year would effectively credit the Plan's control 
measures with eliminating emissions from the fire.
---------------------------------------------------------------------------

    The 2018 Western Nevada County Ozone Plan carries out the 
attainment test procedure consistent with the Modeling Guidance. The 
RRF is calculated as the ratio of future to base year concentrations; 
these are then applied to the 2013 weighted design values for the Grass 
Valley monitor to arrive at a future year design value.\85\ Typically 
the RRFs would be applied to a weighted design value for 2012, the 
model base year,\86\ but in this case CARB used the somewhat higher 
value for 2013, considering the upward trend design values starting in 
2013.\87\ The predicted 2020 ozone design value is 67 ppb or 0.067 ppm, 
well below the level of the 2008 8-hour ozone NAAQS of 0.075 ppm.
---------------------------------------------------------------------------

    \85\ Id. at 57, and Appendix H, ``Modeling Protocol,'' section 
10.3, H-34. The combination of years used is illustrated in Appendix 
E, Table 1, E-11.
    \86\ The Modeling Guidance recommends that RRFs be applied to 
the average of three three-year design values, for the base year and 
the two subsequent years. This amounts to a 5-year weighted average 
of individual year 4th high concentrations, centered on the base 
year, and so is referred to as a weighted design value.
    \87\ 2018 Western Nevada County Ozone Plan, Appendix E, E-10; 
also Plan, 58.
---------------------------------------------------------------------------

    Finally, the 2018 Western Nevada County Ozone Plan modeling 
includes an ``Unmonitored Area Analysis'' (UAA) to assess whether 
locations without a monitor are able to reach attainment; the standard 
attainment test procedure covers only locations with a monitor.\88\ The 
Modeling Guidance describes a procedure utilizing ``gradient adjusted 
spatial fields,'' as well as the EPA software used to carry it out.\89\ 
This procedure uses a form of interpolation, combining monitored 
concentrations and modeled gradients (modeled changes in concentration 
with distance from a monitor) to estimate future concentrations at 
locations without a monitor. The 2018 Western Nevada County Ozone Plan 
describes a UAA carried out using software developed by CARB and 
implemented in ``R,'' \90\ using a procedure virtually the same as that 
outlined in the Modeling Guidance. The Plan states that the 2020 
results show concentrations below 75 ppb at all locations in the 
nonattainment area; it did not examine the surrounding area. Because 
the results are well below the 2008 ozone NAAQS level of 75 ppb, the 
UAA supports the demonstration that all locations in Western Nevada 
County will attain the NAAQS in 2020.
---------------------------------------------------------------------------

    \88\ 2018 Western Nevada County Ozone Plan, Appendix E, section 
5.4, E-41.
    \89\ Modeling Guidance section 4.7, 138.
    \90\ The R Project for Statistical Computing, https://www.r-project.org.
---------------------------------------------------------------------------

    In addition to the formal attainment demonstration, the Plan also 
contains a WOE analysis within Appendix A to the CARB Staff Report. It 
mainly shows the long-term downward trends that continue through 2017, 
the latest year available prior to development of the 2018 Western 
Nevada County Ozone Plan. As described in the WOE, Western Nevada 
County has shown a general downward trend in measured ozone 
concentrations and number of days above the ozone NAAQS but has 
recently seen increases in 2017 and 2018. Atypical high ozone 
concentrations were observed in 2017, though CARB's staff analysis does 
not point to specific anthropogenic or biogenic emission increases or 
meteorology as likely causes for the unusual number of exceedances. 
Additionally, the area may have experienced higher than normal ozone 
concentrations in 2018 due to wildfire impacts in the surrounding areas 
during the summer and fall months. Despite the recent exceptions, there 
are strong downward trends in emissions of ozone and of the ozone 
precursors NOX and VOC, both within the Western Nevada 
County area and in the upwind Sacramento and San Francisco Bay 
areas.\91\ These all show the substantial air quality progress made in 
the Western Nevada County Area and add support to the attainment 
demonstration for 2020.
---------------------------------------------------------------------------

    \91\ 2018 Western Nevada County Ozone Plan, page 41.
---------------------------------------------------------------------------

b. Control Strategy
    The control strategy for attainment of the 2008 ozone NAAQS is 
detailed in Chapter IV of the 2018 Western Nevada County Ozone Plan. 
The Plan's strategy relies primarily on emissions reductions from 
control measures that have been adopted by the Districts and CARB prior 
to the submittal of the Plan. The District has adopted rules for 
reducing emissions from a broad scope of stationary and area sources 
into its RACT SIP. Additionally, a detailed description of the mobile 
source control programs and a comprehensive list of CARB regulations 
are included in Appendices B and C of the Plan. CARB's comprehensive 
strategy to reduce emissions from mobile sources consists of emissions 
standards for new vehicles, in-use programs to reduce emissions from 
existing vehicle and equipment fleets, cleaner fuels, and incentive 
programs to accelerate the penetration of the cleanest vehicles beyond 
that achieved by regulations alone.
    As Table 2 and Table 3 show, the vast majority of emissions 
reductions relied upon by the Plan's control strategy are from the on- 
and off-road mobile source inventory and can be largely attributed to 
control measures adopted by CARB, subsequently approved by the EPA, and 
cited in detail in Section III.C. Generally, the bulk of the emissions 
reductions on which the control strategies rely is expected to come 
from already-adopted measures, which are discussed in Section III.C of 
this document. For the 2008 ozone NAAQS, already-adopted measures are 
expected to achieve all of the reductions needed from the 2012 base 
year to attain the NAAQS in 2020.

                         Table 2--2012 and 2020 NOX Emissions for Western Nevada County
                                        [Summer planning inventory, tpd]
----------------------------------------------------------------------------------------------------------------
                                                                             Emissions
            Source category                   2012            2020        difference from    Percentage of total
                                                                            2012 to 2020    emissions change (%)
----------------------------------------------------------------------------------------------------------------
Stationary Sources.....................           0.106           0.096             -0.010                  -9.4
Area Sources...........................           0.135           0.138             +0.003                   2.2
On-Road Mobile Sources.................           3.976           2.160             -1.816                 -45.7
Other Mobile Sources...................           0.944           0.738             -0.206                 -21.8
                                        ------------------------------------------------------------------------

[[Page 2329]]

 
    Total..............................           5.160           3.131             -2.029                 -39.3
----------------------------------------------------------------------------------------------------------------
Source: 2018 Western Nevada County Ozone Plan, Chapter XII, Table 11, 57. The sum of the emissions values may
  not equal the total shown due to rounding.

                  Table 3--2012 and 2020 Anthropogenic VOC Emissions for Western Nevada County
                                        [Summer planning inventory, tpd]
----------------------------------------------------------------------------------------------------------------
                                                                             Emissions
            Source category                   2012            2020        difference from    Percentage of total
                                                                            2012 to 2020    emissions change (%)
----------------------------------------------------------------------------------------------------------------
Stationary Sources.....................           0.702           0.785             +0.083                  11.8
Area Sources...........................           1.394           1.515             +0.121                   8.7
On-Road Mobile Sources.................           1.793           1.007             -0.786                 -43.8
Other Mobile Sources...................           1.327           0.958             -0.369                 -27.8
                                        ------------------------------------------------------------------------
    Total..............................           5.215           4.265             -0.950                 -18.2
----------------------------------------------------------------------------------------------------------------
Source: 2018 Western Nevada County Ozone Plan, Chapter XII, Table 11, 57. The sum of the emissions values may
  not equal the total shown due to rounding.

c. Attainment Demonstration
    Chapter XII of the Plan describes the attainment demonstration in 
general terms, including photochemical modeling results, while Appendix 
E to the Plan provides more detail concerning photochemical modeling. 
Other aspects of this demonstration are included throughout the Plan, 
including emissions inventory forecasts included in Appendix A and the 
control strategy described in Chapter IV. The WOE analysis in Appendix 
A to the CARB Staff Report includes additional supporting information 
to complement the photochemical modeling and to provide context for 
this attainment demonstration, such as analyses of anthropogenic 
emissions, ambient ozone data, and meteorological analyses.
3. The EPA's Review of the State's Submission
a. Photochemical Modeling
    To approve a SIP's attainment demonstration, the EPA must make 
several findings. First, we must find that the demonstration's 
technical bases, including the emissions inventories and air quality 
modeling, are adequate. As discussed above in Section III.A of this 
document, we are proposing to approve the base year emissions inventory 
and to find that the future year emissions projections in the 2018 
Western Nevada County Ozone Plan reflect appropriate calculation 
methods and that the latest planning assumptions are properly supported 
by SIP-approved stationary and mobile source measures.
    The modeling followed the Modeling Guidance in essentially all 
respects, and both the meteorological and the photochemical models 
showed good performance. One difference between CARB's modeling and the 
Modeling Guidance was that the state applied RRFs to a weighted design 
value based on the year 2013, instead of 2012, as would be typical for 
modeling of a 2012 base year. The Modeling Guidance recognizes that 
there is no one correct method for choosing base design values,\92\ and 
provides for other calculations with appropriate justification, such as 
consideration of unusual meteorological conditions. As noted above, the 
state's choice of 2013 was based on design values increasing relative 
to 2012. Since a higher starting point base design value will yield a 
higher 2020 attainment year design value, the state's use of 2013 adds 
conservatism to the attainment demonstration.
---------------------------------------------------------------------------

    \92\ Modeling Guidance, section 4.1.1, ``Establishing the Base 
Design Value,'' 103.
---------------------------------------------------------------------------

    An important difference from the Modeling Guidance is that the 
state presented a model performance evaluation only for the single 
monitoring site in the nonattainment area, in Grass Valley. The 
Modeling Guidance recommends a performance evaluation using all 
available ambient monitoring data.\93\ This is of particular importance 
for the Western Nevada County area. As described in the conceptual 
description in the Plan discussed above, ozone in the area is largely 
due to emissions in and transport from the upwind Sacramento area. The 
chemical evolution of the pollutant plume as it travels from Sacramento 
to Nevada County necessitates evaluation at more than a single downwind 
location. This means that the submitted modeling performance evaluation 
alone may not be adequate for assessing the performance model, which is 
influenced by emissions from a much larger area, with various 
meteorological and terrain impacts. However, because the 2012 modeling 
exercise in the Plan was essentially the same as that undertaken for 
the 2017 Sacramento Regional Ozone Plan, the EPA is relying on the 
latter plan's more complete model performance evaluation. As discussed 
in the technical support document \94\ accompanying the EPA's proposed 
action on the Sacramento plan, the state followed EPA recommended 
modeling procedures and the modeling had good performance. That was 
shown in statistical and dynamic performance analyses that covered a 
larger portion of the modeling domain than the analyses in the 
submittal for the 2018 Western Nevada County Ozone Plan, encompassing 
the Western Nevada County as well as the Sacramento area. Overall, the 
EPA therefore considers the modeling in the 2018 Western Nevada

[[Page 2330]]

County Ozone Plan to be adequate for establishing modeling performance.
---------------------------------------------------------------------------

    \93\ Modeling Guidance, section 3.1, ``Overview of Model 
Performance Evaluation,'' 68.
    \94\ Docket EPA-R09-OAR-2020-0425, item A-85, ``Modeling 
Technical Support Document (TSD) for the `2017 Sacramento Regional 
Ozone Plan', 2008 8-hour ozone National Ambient Air Quality 
Standard,'' September 14, 2020, Air and Radiation Division, EPA 
Region IX.
---------------------------------------------------------------------------

    The modeling shows that existing control measures from CARB and the 
Districts are sufficient to attain the 2008 8-hour ozone NAAQS by 2020 
at all monitoring sites in the Western Nevada County area. The Plan 
follows the procedures recommended in the EPA Modeling Guidance, 
properly incorporates all modeling and input preparation procedures, 
tests, and performance analyses called for in the modeling protocol, 
demonstrates good model performance, and responds to emission changes 
consistent with observations. Therefore, based on the documentation 
included in the modeling performance analysis, UAA, and WOE analysis, 
the EPA finds that the photochemical modeling is adequate for purposes 
of supporting the attainment demonstration.
b. Control Strategy
    As discussed above, the 2018 Western Nevada County Ozone Plan 
relies on previously adopted measures to achieve all of the emissions 
reductions needed to attain the 2008 ozone NAAQS in 2020. For the 
reasons described above, we find that the emissions reductions that are 
relied on for attainment are creditable and are sufficient to provide 
for attainment.
c. Attainment Demonstration
    The 2018 Western Nevada County Ozone Plan follows the modeling 
procedures recommended in the EPA's Modeling Guidance and shows 
excellent performance in simulating observed ozone concentrations in 
the 2012 base year. Given the extensive discussion of modeling 
procedures, tests, and performance analyses called for in the modeling 
protocol, the good model performance, and the model response to 
emissions changes consistent with observations, the EPA finds that the 
modeling is adequate for purposes of supporting the attainment 
demonstration. Based on our review of the 2018 Western Nevada County 
Ozone Plan and our proposed findings that the photochemical modeling 
and control strategy are acceptable and demonstrate attainment by the 
applicable attainment date, we propose to approve the attainment 
demonstration for the 2008 ozone NAAQS in the Western Nevada County 
Ozone Plan as meeting the requirements of CAA section 182(c)(2)(A) and 
40 CFR 51.1108.

E. Rate of Progress Plan and Reasonable Further Progress Demonstration

1. Statutory and Regulatory Requirements
    Requirements for RFP for ozone nonattainment areas are specified in 
CAA sections 172(c)(2), 182(b)(1), and 182(c)(2)(B). CAA section 
172(c)(2) requires that plans for nonattainment areas provide for RFP, 
which is defined at CAA section 171(1) as such annual incremental 
reductions in emissions of the relevant air pollutant as are required 
under part D, ``Plan Requirements for Nonattainment Areas,'' or may 
reasonably be required by the EPA for the purpose of ensuring 
attainment of the applicable NAAQS by the applicable date. CAA section 
182(b)(1) specifically requires that ozone nonattainment areas that are 
classified as Moderate or above demonstrate a 15 percent reduction in 
VOC within the first six years of the planning period. The EPA has 
typically referred to section 182(b)(1) as the Rate of Progress (ROP) 
requirement. For ozone nonattainment areas classified as Serious or 
higher, section 182(c)(2)(B) requires reductions averaged over each 
consecutive 3-year period, beginning 6 years after the baseline year 
until the attainment date, of at least 3 percent of baseline emissions 
per year. CAA section 182(c)(2)(B)(ii) allows an amount less than 3 
percent of such baseline emissions each year if the state demonstrates 
to the EPA that a plan includes all measures that can feasibly be 
implemented in the area in light of technological achievability. To 
meet CAA sections 172(c)(2) and 182(c)(2)(B) RFP requirements, the 
state may substitute NOX emissions reductions for VOC 
reductions.\95\
---------------------------------------------------------------------------

    \95\ 40 CFR 51.1110(a)(2)(i)(C) and 40 CFR 51.1110(a)(2)(ii)(B); 
and 70 FR 12264, at 12271 (March 6, 2015).
---------------------------------------------------------------------------

    The 2008 Ozone SRR provides that areas classified Moderate or 
higher for the 2008 8-hour ozone standard will have met the ROP 
requirements of CAA section 182(b)(1) if the area has a fully approved 
15 percent ROP plan for the 1979 1-hour or 1997 8-hour ozone standards, 
provided the boundaries of the ozone nonattainment areas are the 
same.\96\ Western Nevada County does not have a fully approved 15 
percent ROP plan for either the 1979 1-hour or the 1997 8-hour ozone 
standards.\97\ Therefore, the 15 percent ROP requirement of section 
182(b)(1) remains applicable to Western Nevada County, and the area 
must show a 15 percent reduction in VOC within the first six years of 
the planning period.
---------------------------------------------------------------------------

    \96\ 70 FR 12264, 12271 (March 6, 2015). For more information 
about how the RFP requirement of section 172(c)(2) applies in such 
areas, see 84 FR 28132, 28157 (June 17, 2019).
    \97\ As explained above in Section I, for the 1979 1-hour ozone 
NAAQS, the EPA classified Western Nevada County as Unclassifiable/
Attainment and, thus, it was not subject to the ROP requirement. 62 
FR 38856 (July 18, 1997). For the 1997 8-hour ozone NAAQS, the EPA 
initially designated Western Nevada County as a ``Subpart 1'' 
nonattainment area and later reclassified the area to Moderate, 
triggering the ROP requirement, but subsequently issued a clean data 
determination, which suspended attainment-related planning 
requirements, including the ROP requirement. 69 FR 23857 (April 30, 
2004); 77 FR 28423 (May 14, 2012); 77 FR 71551 (December 3, 2012).
---------------------------------------------------------------------------

    Except as specifically provided in CAA section 182(b)(1)(C), 
emissions reductions from all SIP-approved, federally promulgated, or 
otherwise SIP-creditable measures that occur after the baseline year 
are creditable for purposes of demonstrating that the RFP targets are 
met. Because the EPA has determined that the passage of time has caused 
the effect of certain exclusions to be de minimis, the RFP 
demonstration is no longer required to calculate and specifically 
exclude reductions from measures related to motor vehicle exhaust or 
evaporative emissions promulgated by January 1, 1990; regulations 
concerning Reid vapor pressure promulgated by November 15, 1990; 
measures to correct previous RACT requirements; and, measures required 
to correct previous inspection and maintenance (I/M) programs.\98\
---------------------------------------------------------------------------

    \98\ 40 CFR 51.1110(a)(7).
---------------------------------------------------------------------------

    The 2008 Ozone SRR requires the RFP baseline year to be the most 
recent calendar year for which a complete triennial inventory was 
required to be submitted to the EPA. For the purposes of developing RFP 
demonstrations for the 2008 ozone NAAQS, the applicable triennial 
inventory year is 2011. As discussed previously, the 2008 Ozone SRR 
provided states with the opportunity to use an alternative baseline 
year for RFP,\99\ but this provision was vacated by the D.C. Circuit in 
the South Coast II decision.
---------------------------------------------------------------------------

    \99\ See 40 CFR 51.1110(b).
---------------------------------------------------------------------------

2. Summary of the State's Submission
    Documentation for the Western Nevada County RFP baseline and 
milestone emissions inventories is found in the 2018 Western Nevada 
County Ozone Plan on pages 21-34, 54-56, and in Appendix A. Consistent 
with the South Coast II decision, CARB's RFP demonstration for Western 
Nevada County uses a 2011 RFP baseline emissions inventory.\100\ To 
develop the 2011 RFP baseline inventory, CARB relied on actual 
emissions reported from industrial point sources for year 2011 and 
backcasted emissions from smaller stationary sources and area sources 
from

[[Page 2331]]

2012 to 2011 using the same growth and control factors used for future 
years.\101\ The Plan indicates that the 2012 inventory base year for 
modeling and the 2011 baseline year inventory for RFP are consistent 
with each other since they both use actual emissions for stationary 
sources and the same growth profiles. Emissions estimates in the 
baseline emissions inventory reflect District and CARB rules submitted 
to the EPA through November 2016.
---------------------------------------------------------------------------

    \101\ 2018 Western Nevada County Ozone Plan, page 23.
---------------------------------------------------------------------------

    The RFP demonstration for Western Nevada County for the 2008 ozone 
NAAQS is shown in Table 10 of the 2018 Western Nevada County Ozone 
Plan, which is reproduced as Table 4 below. As Western Nevada County is 
a Serious nonattainment area without a previously approved ROP plan, 
the Plan demonstrates a reduction in VOC of 15 percent from baseline 
emissions within six years of the RFP baseline year period, consistent 
with CAA 182(b)(1). The Plan shows an additional 3 percent reduction of 
VOC or NOX emissions, averaged over each consecutive 3-year 
period until the attainment year. The RFP demonstration calculates 
future year VOC targets from the 2011 baseline, consistent with CAA 
182(c)(2)(B)(i), and it substitutes NOX reductions for VOC 
reductions beginning in milestone year 2020 to meet VOC emission 
targets as allowed under CAA section 182(c)(2)(C).\102\ CARB concludes 
that the RFP demonstration meets the applicable requirements for each 
milestone year as well as the attainment year.
---------------------------------------------------------------------------

    \102\ See also 40 CFR 51.1110(a)(2)(i)(C) and 40 CFR 
51.1110(a)(2)(ii)(B); and 70 FR 12264, at 12271 (March 6, 2015). The 
District's RFP demonstration substitutes NOX reductions 
for VOC reductions on a percentage basis. See EPA, NOX 
Substitution Guidance (December 1993).

       Table 4--2008 Ozone RFP Demonstration Western Nevada County
               [Summer planning inventory, tpd or percent]
------------------------------------------------------------------------
                                                    VOC
                                  --------------------------------------
                                       2011         2017         2020
------------------------------------------------------------------------
Baseline VOC.....................         5.50         4.50         4.20
Required change since 2011 (VOC    ...........           15           24
 or NOX), %......................
Target VOC level.................  ...........          4.7          4.2
Apparent shortfall (-)/surplus     ...........         +0.2         -0.1
 (+) in VOC......................
Apparent shortfall (-)/surplus     ...........         +3.2         -1.4
 (+) in VOC, %...................
Actual VOC shortfall (-)/surplus   ...........         +3.2         -1.4
 (+), %..........................
------------------------------------------------------------------------

 
                                                    NOX
                                  --------------------------------------
                                       2011         2017         2020
------------------------------------------------------------------------
Baseline NOX.....................         5.69         3.74         2.89
Change in NOX since 2011.........  ...........         1.95          2.8
Change in NOX since 2011, %......  ...........           34           49
NOX reductions used for VOC        ...........  ...........          3.1
 substitution through last
 milestone year, %...............
NOX reductions since 2011          ...........           34           49
 available for VOC substitution
 in this milestone year, %.......
NOX reductions since 2011 used     ...........            0          3.1
 for VOC substitution in this
 milestone year, %...............
NOX reductions since 2011 surplus  ...........           34         45.9
 after meeting VOC substitution
 needs in this milestone year, %.
Total shortfall for RFP..........  ...........            0            0
RFP met?.........................  ...........          Yes          Yes
------------------------------------------------------------------------
Source: 2018 Western Nevada County Ozone Plan, Table 10, p. 55.

3. The EPA's Review of the State's Submission
    Based on our review of the emissions inventory documentation in the 
2018 Western Nevada County Ozone Plan, we find that CARB and the 
District have used the most recent planning and activity assumptions, 
emissions models, and methodologies in developing the RFP baseline and 
milestone year emissions inventories. We have also reviewed the 
calculations in Table 10 of the Plan and presented in Table 4 above and 
find that the District and CARB have used an appropriate calculation 
method to demonstrate RFP.
    We have also reviewed the comparison of the VOC emission reductions 
against the 15 percent ROP requirement. As shown in Table 4, the RFP 
demonstration shows that Western Nevada County meets the 15 percent 
reduction in VOC emissions with an additional 3.2 percent surplus in 
VOC emissions reductions from 2011 to 2017. Such reductions satisfy the 
ROP requirement for Western Nevada County for the 2008 ozone NAAQS. As 
a result, we find that the District and CARB have met the ROP 
requirements of CAA section 182(b)(1) for Western Nevada County with 
respect to the 2008 ozone NAAQS.
    We find that the District's use of substitution of NOX 
reductions for VOC reductions in this demonstration is appropriate 
under CAA section 182(c)(2)(C). As described in Section III.D.2.a of 
this document, ozone formation in Western Nevada County is 
NOX-limited, and the substituted NOX reductions 
are expected to achieve an equal or greater reduction in ozone 
concentrations as would result from the VOC emissions reductions 
described in CAA section 182(c)(2)(B).\103\
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    \103\ As discussed above, modeling for the Sacramento 
nonattainment area used a modeling domain that encompassed the 
Western Nevada nonattainment area, and was used to create an 
isopleth diagram showing ozone for various levels of NOX 
and VOC emissions. Sacramento Regional 2008 NAAQS 8-hour Attainment 
and Reasonable Further Progress Plan (``2017 Sacramento Regional 
Ozone Plan''), July 24, 2017, Appendix B-4, p.B-158, Figure 16, 
available at https://ww2.arb.ca.gov/resources/documents/2017-sacramento-regional-2008-8-hour-ozone-attainment-and-further-reasonable. The EPA used this information to estimate the 
sensitivity of ozone to NOX reductions and to VOC 
reductions, and found NOX reductions to be 23 times as 
effective at reducing ozone as VOC reductions, on a tonnage basis, 
and 13 times as effective on a percentage basis. Docket EPA-R09-OAR-
2020-0425, item A-86, ``Assessment of Sacramento Metro NAA 
Conformity Motor Vehicle Emissions Budget Consistency with O3 NAAQS 
Attainment,'' September 14, 2020, Air and Radiation Division, EPA 
Region IX.

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[[Page 2332]]

    For these reasons, we have determined that the 2018 Western Nevada 
County Ozone Plan demonstrates RFP in each milestone year and the 
attainment year, consistent with applicable CAA requirements and EPA 
guidance. We therefore propose to approve the RFP demonstrations for 
the Western Nevada County nonattainment area for the 2008 ozone NAAQS 
under sections 172(c)(2), 182(b)(1) and 182(c)(2)(B) of the CAA and 40 
CFR 51.1110(a)(2)(ii).

F. Contingency Measures

1. Statutory and Regulatory Requirements
    Under the CAA, 8-hour ozone nonattainment areas classified under 
subpart 2 as Moderate or above must include in their SIPs contingency 
measures consistent with sections 172(c)(9) and 182(c)(9). Contingency 
measures are additional controls or measures to be implemented in the 
event the area fails to make reasonable further progress or to attain 
the NAAQS by the attainment date. The SIP should contain trigger 
mechanisms for the contingency measures, specify a schedule for 
implementation, and indicate that the measure will be implemented 
without significant further action by the state or the EPA.\104\
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    \104\ 70 FR 71612 (November 29, 2005). See also 2008 Ozone SRR, 
80 FR 12264, at 12285 (March 6, 2015).
---------------------------------------------------------------------------

    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's 2008 Ozone SRR 
reiterates the EPA's policy that contingency measures should generally 
provide for emissions reductions approximately equivalent to one year's 
worth progress, amounting to reductions of 3 percent of the baseline 
emissions inventory for the nonattainment area.\105\
---------------------------------------------------------------------------

    \105\ 80 FR 12264 at 12285 (March 6, 2015).
---------------------------------------------------------------------------

    It has been the EPA's longstanding interpretation of CAA section 
172(c)(9) that states may rely on federal measures (e.g., federal 
mobile source measures based on the incremental turnover of the motor 
vehicle fleet each year) and local measures already scheduled for 
implementation that provide emissions reductions in excess of those 
needed to provide for RFP or expeditious attainment. The key is that 
the Act requires that contingency measures provide for additional 
emissions reductions that are not relied on for RFP or attainment and 
that are not included in the RFP or attainment demonstrations as 
meeting part or all of the contingency measures requirements. The 
purpose of contingency measures is to provide continued emissions 
reductions while the plan is being revised to meet the missed milestone 
or attainment date.
    The EPA has approved numerous SIPs under this interpretation, i.e., 
SIPs that use as contingency measures one or more federal or local 
measures that are in place and provide reductions that are in excess of 
the reductions required by the attainment demonstration or RFP 
plan,\106\ and there is case law supporting the EPA's interpretation in 
this regard.\107\ However, in Bahr v. EPA, the United States Court of 
Appeals for the Ninth Circuit (``Ninth Circuit'') rejected the EPA's 
interpretation of CAA section 172(c)(9) as allowing for early 
implementation of contingency measures.\108\ 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.\109\ Thus, within the geographic jurisdiction of the Ninth 
Circuit, states cannot rely on early-implemented measures to comply 
with the contingency measures requirements under CAA section 172(c)(9) 
and 182(c)(9).\110\
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    \106\ See, e.g., 62 FR 15844 (April 3, 1997) (direct final rule 
approving an Indiana ozone SIP revision); 62 FR 66279 (December 18, 
1997) (final rule approving an Illinois ozone SIP revision); 66 FR 
30811 (June 8, 2001) (direct final rule approving a Rhode Island 
ozone SIP revision); 66 FR 586 (January 3, 2001) (final rule 
approving District of Columbia, Maryland, and Virginia ozone SIP 
revisions); and 66 FR 634 (January 3, 2001) (final rule approving a 
Connecticut ozone SIP revision).
    \107\ See, e.g., LEAN v. EPA, 382 F.3d 575 (5th Cir. 2004) 
(upholding contingency measures that were previously required and 
implemented where they were in excess of the attainment 
demonstration and RFP SIP).
    \108\ Bahr v. EPA, 836 F.3d 1218, at 1235-1237 (9th Cir. 2016).
    \109\ Id. at 1235-1237.
    \110\ The Bahr v. EPA decision involved a challenge to an EPA 
approval of contingency measures under the general nonattainment 
area plan provisions for contingency measures in CAA section 
172(c)(9), but, given the similarity between the statutory language 
in section 172(c)(9) and the ozone-specific contingency measures 
provision in section 182(c)(9), we find that the decision affects 
how both sections of the Act must be interpreted.
---------------------------------------------------------------------------

2. Summary of the State's Submission
    In the 2018 Western Nevada County Ozone Plan, CARB calculates the 
extent of surplus emission reductions (i.e., surplus to meeting the RFP 
milestone requirement for a given milestone year) in the milestone 
years and estimates the incremental emissions reductions in the year 
following the attainment year.\111\ In light of the Bahr v. EPA 
decision, however, the 2018 Western Nevada County Ozone Plan does not 
rely on the surplus or incremental emissions reductions to comply with 
the contingency measures requirements of sections 172(c)(9) and 
182(c)(9) but, rather, to provide context in which to evaluate the 
adequacy of Bahr-compliant (i.e., to take effect if triggered) 
contingency measures for the 2008 ozone NAAQS.
---------------------------------------------------------------------------

    \111\ CARB Staff Report, Section D, 10-11.
---------------------------------------------------------------------------

    To comply with sections 172(c)(9) and 182(c)(9), as interpreted in 
the Bahr v. EPA decision, the state must develop, adopt and submit a 
contingency measure to be triggered upon a failure to meet RFP 
milestones or failure to attain the NAAQS by the applicable attainment 
date regardless of the extent to which already-implemented measures 
would achieve surplus emissions reductions beyond those necessary to 
meet RFP milestones and beyond those predicted to achieve attainment of 
the NAAQS. Therefore, to fully address the contingency measures 
requirement for the 2008 ozone NAAQS in the Western Nevada 
nonattainment area, the District has committed to develop, adopt and 
submit a contingency measure to CARB in sufficient time to allow CARB 
to submit the contingency measure as a SIP revision to the EPA within 
12 months of the EPA's final conditional approval of the contingency 
measures element of the 2018 Western Nevada County Ozone Plan.\112\
---------------------------------------------------------------------------

    \112\ Letter dated October 26, 2020, from Gretchen Bennitt, 
Executive Director, NSAQMD, to Richard Corey, Executive Officer, 
CARB.
---------------------------------------------------------------------------

    The District's commitment is to adopt the 2019 (or most recent) 
Architectural Coatings Suggested Control Measure (SCM), developed and 
approved by CARB, as a rule to take effect upon adoption throughout the 
nonattainment area upon a determination that the Western Nevada County 
nonattainment area failed to meet an RFP milestone or failed to attain 
the 2008 ozone NAAQS by the applicable attainment date. The District 
estimates that adoption of this new measure will yield an estimated 
0.010 tpd in VOC emissions reductions in the nonattainment area. The 
District also evaluated three other additional categories for potential 
contingency measures. The categories are automotive coatings, water 
heaters, boilers, and process heaters rated less than a million BTU per 
hour, and miscellaneous combustion units. However, the District 
determined that these categories did not yield meaningful 
reductions.\113\
---------------------------------------------------------------------------

    \113\ Appendix to Letter dated October 26, 2020, from Gretchen 
Bennitt, Executive Director, NSAQMD, to Richard Corey, Executive 
Officer, CARB.
---------------------------------------------------------------------------

    CARB attached the District's commitment to a letter committing CARB 
to adopt and submit the revised

[[Page 2333]]

NSAQMD rule to the EPA within one year of the EPA's final conditional 
approval of the contingency measures element of the 2018 Western Nevada 
County Ozone Plan.\114\
---------------------------------------------------------------------------

    \114\ Letter dated November 16, 2020, from Richard W. Corey, 
Executive Officer, CARB, to John Busterud, Regional Administrator, 
EPA Region IX.
---------------------------------------------------------------------------

3. The EPA's Review of the State's Submission
    CAA sections 172(c)(9) and 182(c)(9) require contingency measures 
to address potential failures to achieve RFP milestones or to attain 
the NAAQS by the applicable attainment date through implementation of 
additional emissions controls in the event the area fails to make RFP 
or to attain the NAAQS by the applicable attainment date. Contingency 
measures must provide for the implementation of additional emissions 
controls, if triggered, without significant further action by the state 
or the EPA. For the purposes of evaluating the adequacy of the 
emissions reductions from the contingency measures (once adopted and 
submitted), we find it useful to distinguish between contingency 
measures to address potential failure to achieve RFP milestones (``RFP 
contingency measures'') and contingency measures to address potential 
failure to attain the NAAQS (``attainment contingency measures'').
    With respect to the RFP contingency measures requirement, we have 
reviewed the surplus emissions estimates in each of the RFP milestone 
years, as shown in CARB's Staff Report, and find that the calculations 
are correct. We therefore agree that the 2018 Western Nevada County 
Ozone Plan provides surplus emissions reductions well beyond those 
necessary to demonstrate RFP in all of the RFP milestone years. While 
such surplus emissions reductions in the RFP milestone years do not 
represent contingency measures themselves, we believe they are relevant 
in evaluating the adequacy of RFP contingency measures that are 
submitted (or will be submitted) to meet the requirements of sections 
172(c)(9) and 182(c)(9).
    The attainment year for the 2008 ozone NAAQS in Western Nevada 
County coincides with the 2020 RFP milestone, and thus, we have 
reviewed the emissions reductions estimated by the District for the 
committed contingency measures in light of the facts and circumstances 
in Western Nevada County in the year following the attainment year, to 
determine whether there will be sufficient continued progress in that 
area in the event the area fails to achieve the 2020 RFP milestone or 
fails to attain the 2008 ozone NAAQS by the 2020 attainment year.\115\
---------------------------------------------------------------------------

    \115\ CAA section 182(g)(2) provides that states must submit RFP 
milestone compliance demonstrations within 90 days after the date on 
which an applicable milestone occurs, except where the milestone and 
attainment date are the same and the standard has been attained.
---------------------------------------------------------------------------

    As discussed above, 2018 Western Nevada County Ozone Plan provides 
estimates of emissions reductions that are surplus of the reductions 
necessary for RFP or attainment, but does not include measures that 
would implement additional emissions controls, if triggered, without 
significant further action by the state or the EPA. However, CARB and 
the District have submitted commitments to adopt and submit a revised 
District rule with the necessary provisions as a SIP revision within 
one year of the EPA's final action on the contingency measures element 
of the Plan. The specific revisions the District has committed to make, 
such as tightening control efficiencies or establishing content limits, 
upon a failure to achieve a milestone or a failure to attain, would 
comply with the requirements in CAA sections 172(c)(9) and 182(c)(9) 
because the additional controls would be undertaken if the area fails 
to achieve a milestone or fails to attain, and would take effect 
without significant further action by the State or the EPA.
    We find that the contingency measures described in the District and 
CARB's commitment letters would provide adequate emissions reductions 
when triggered. Neither the CAA nor the EPA's implementing regulations 
for the ozone NAAQS establish a specific amount of emissions reductions 
that implementation of contingency measures must achieve, but we 
generally expect that contingency measures should provide for emissions 
reductions approximately equivalent to one year's worth of RFP, which, 
for ozone, amounts to reductions of 3 percent of the RFP baseline year 
emissions inventory for the nonattainment area. For the 2008 ozone 
NAAQS in Western Nevada County, one year's worth of RFP is 
approximately 0.16 tpd of VOC or 0.17 tpd of NOX 
reductions.\116\ The District's commitment letter estimates the 
potential additional emission reductions from its contingency measure 
commitment at 0.010 tpd VOC. However, emissions in the year following 
the attainment year (2021) in Western Nevada County are expected to be 
approximately 0.048 tpd lower for VOC and 0.23 tpd lower for 
NOX than in the attainment year (2020).\117\ The downward 
trend in emissions reflects the continuing benefits of already-
implemented measures and is primarily the result of vehicle turnover, 
which refers to the ongoing replacement by individuals, companies, and 
government agencies of older, more polluting vehicles and engines with 
newer vehicles and engines. While the continuing reductions from such 
already-implemented measures do not constitute contingency measures 
themselves, they provide context in which we evaluate the adequacy of 
the contingency measures submitted (or, in this case, to be submitted) 
to fulfill the requirements of CAA sections 172(c)(9) and 182(c)(9).
---------------------------------------------------------------------------

    \116\ One year's worth of RFP for Western Nevada County 
corresponds to 3 percent of the 2011 RFP baseline year inventories 
for VOC (5.496 tpd) and NOX (5.687 tpd).
    \117\ Estimates for the emissions reductions in the year 
following the attainment year are based on the emissions inventories 
for Western Nevada County in Appendix A of the Plan. The estimate of 
the reductions in emissions of 0.048 tpd of VOC and 0.23 tpd of 
NOX in 2021 (relative to 2020) amounts to approximately 
29 percent and 132 percent of one year's worth of progress, 
respectively in this area based on the 2011 RFP baseline inventory.
---------------------------------------------------------------------------

    In this instance, we find that the emissions reductions from the 
to-be-adopted contingency measures together with the reductions 
expected to occur due to already-implemented measures are consistent 
with our guidance recommending that contingency measures provide for 
one year's worth of progress in the event of a failure to meet an RFP 
milestone or a failure to attain the NAAQS by the applicable attainment 
date. Therefore, in light of the year-to-year reductions in the VOC and 
NOX inventories, we find that the contingency measures 
described in the District's and CARB's commitment letters would provide 
sufficient emissions reductions even though reductions from the 
measures would be lower than the EPA normally recommends for such 
measures.
    For these reasons, and in light of commitments from the District 
and CARB to adopt and submit a District rule that will apply tighter 
limits or requirements upon a failure to achieve an RFP milestone or 
the 2008 ozone NAAQS by the applicable attainment date, we propose to 
approve conditionally the contingency measures element of the 2018 
Western Nevada County Ozone Plan as meeting the contingency measures 
requirements of CAA sections 172(c)(9) and 182(c)(9). Our proposed 
approval is conditional because it relies upon commitments to adopt and 
submit a specific enforceable

[[Page 2334]]

contingency measure (i.e., a revised District rule or rules with 
contingent provisions). Conditional approvals are authorized under CAA 
section 110(k)(4).

G. Motor Vehicle Emissions Budgets for Transportation Conformity

1. Statutory and Regulatory Requirements
    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 in 
nonattainment and maintenance areas coordinate with state and local air 
quality and transportation agencies, the EPA, the FHWA, and the FTA to 
demonstrate that an area's regional transportation plans and 
transportation improvement programs conform to the applicable SIP.\118\ 
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'') 
contained in all control strategy SIPs. Budgets are generally 
established for specific years and specific pollutants or precursors. 
Ozone plans should identify budgets for on-road emissions of ozone 
precursors (NOX and VOC) in the area for each RFP milestone 
year and, if the plan demonstrates attainment, the attainment 
year.\119\
---------------------------------------------------------------------------

    \118\ As mentioned in Section I.B, Western Nevada County is an 
isolated rural area. Isolated rural areas do not have federally 
required metropolitan transportation plans and transportation 
improvement programs, and they are not subject to the frequency 
requirements for conformity determinations on transportation plans 
and transportation improvement programs (40 CFR 93.104(b), (c), and 
(e)). Instead, in an isolated rural area, a conformity determination 
is required for the 2008 ozone and other applicable NAAQS only when 
a non-exempt FHWA/FTA project(s) needs funding or approval, based on 
the conformity requirements for isolated rural areas at 40 CFR 
93.109(g). See also ``Transportation Conformity Guidance for 2008 
Ozone Nonattainment Areas,'' July 2012, EPA Office of Transportation 
and Air Quality, Transportation and Climate Division, available at 
https://www3.epa.gov/ttn/naaqs/aqmguide/collection/cp2/20120701_otaq_epa-420_b-12-045_guidance_transport_conformity_2008_oxone_naaqs.pdf.
    \119\ 40 CFR 93.102(b)(2)(i).
---------------------------------------------------------------------------

    For budgets to be approvable, they must meet, at a minimum, the 
EPA's adequacy criteria (40 CFR 93.118(e)(4)) and be approvable under 
all pertinent SIP requirements. To meet these requirements, the budgets 
must be consistent with the attainment and RFP requirements and reflect 
all of the motor vehicle control measures contained in the attainment 
and RFP demonstrations.\120\
---------------------------------------------------------------------------

    \120\ 40 CFR 93.118(e)(4)(iii), (iv) and (v). For more 
information on the transportation conformity requirements and 
applicable policies on budgets, please visit our transportation 
conformity website at: http://www.epa.gov/otaq/stateresources/transconf/index.htm.
---------------------------------------------------------------------------

    The EPA's process for determining adequacy of a budget consists of 
three basic steps: (1) Providing public notification of a SIP 
submission; (2) providing the public the opportunity to comment on the 
budget during a public comment period; and (3) making a finding of 
adequacy or inadequacy.\121\
---------------------------------------------------------------------------

    \121\ 40 CFR 93.118(f)(2).
---------------------------------------------------------------------------

2. Summary of the State's Submission
    Chapter VI of the 2018 Western Nevada County Ozone Plan includes 
budgets for the 2020 RFP milestone and attainment year. The budgets 
were derived from the 2011 base year. The budgets were calculated using 
EMFAC2014, CARB's then-current and latest approved version of the EMFAC 
model for estimating emissions from on-road vehicles operating in 
California and are rounded up to the nearest whole number. The budgets 
in the Plan reflect updated VMT estimates from the NCTC 2015-2035 
Regional Transportation Plan, adopted by NCTC in January 2018, which 
are lower than the conservative estimate of on-road emissions in the 
emissions inventory. Given the use of updated travel data and CARB's 
convention of rounding emissions up to the next tenth (0.1), there are 
some differences between the budgets and the emissions inventories in 
the Plan for the RFP and attainment demonstrations. CARB's addendum to 
the technical clarification memorandum dated October 27, 2020 indicates 
that the differences are quite small (VOC: 0.55 tpd; NOX: 
0.26 tpd) and do not impact the RFP or attainment demonstrations.\122\ 
The conformity budgets for NOX and VOC in the Plan for the 
Western Nevada County area are provided in Table 5 below.
---------------------------------------------------------------------------

    \122\ This is addressed in more detail in our memorandum for the 
budgets, as detailed in Section III.G.3.

 Table 5--Transportation Conformity Budgets for 2020 for the 2008 Ozone
                     NAAQS in Western Nevada County
                    [Summer planning inventory, tpd]
------------------------------------------------------------------------
                                                       2020
                                         -------------------------------
                                                VOC             NOX
------------------------------------------------------------------------
Motor vehicle emissions budget..........             0.8             1.7
------------------------------------------------------------------------
Source: Table 7 of the 2018 Western Nevada County Ozone Plan.

3. The EPA's Review of the State's Submission
    As part of our review of the approvability of the budgets in the 
2018 Western Nevada County Ozone Plan, we have evaluated the budgets 
using our adequacy criteria in 40 CFR 93.118(e)(4) and (5). We will 
complete the adequacy review concurrent with our final action on the 
2018 Western Nevada County Ozone Plan. The transportation conformity 
rule does not require the EPA to find budgets adequate prior to 
proposing approval of them.\123\ Today, the EPA is announcing the 
beginning of the adequacy process for these budgets, and the public has 
30 days to comment on their adequacy, per the transportation conformity 
regulation at 40 CFR 93.118(f)(2)(i) and (ii).
---------------------------------------------------------------------------

    \123\ Under the transportation conformity regulations, the EPA 
may review the adequacy of submitted motor vehicle emission budgets 
simultaneously with the EPA's approval or disapproval of the 
submitted implementation plan. 40 CFR 93.118(f)(2).
---------------------------------------------------------------------------

    As documented in a separate memorandum included in the docket for

[[Page 2335]]

this rulemaking, we preliminarily conclude that the budgets in the 2018 
Western Nevada County Ozone Plan meet each adequacy criterion.\124\ 
While adequacy and approval are two separate actions, reviewing the 
budgets in terms of the adequacy criteria informs the EPA's decision to 
propose to approve the budgets. We have completed our detailed review 
of the 2018 Western Nevada County Ozone Plan and are proposing herein 
to approve the SIP's attainment and RFP demonstrations. We have also 
reviewed the budgets in the 2018 Western Nevada County Ozone Plan and 
found that they are consistent with the attainment and RFP 
demonstrations for which we are proposing approval, are based on 
control measures that have already been adopted and implemented, and 
meet all other applicable statutory and regulatory requirements 
including the adequacy criteria in 40 CFR 93.1118(e)(4) and (5). 
Therefore, we are proposing to find adequate and approve the 2020 
budgets in the 2018 Western Nevada County Ozone Plan (and shown in 
Table 5, above). If we finalize our adequacy determination and approval 
of the budgets for the 2008 ozone NAAQS in the Plan as proposed, then 
they will be approved for use in transportation conformity 
determinations.
---------------------------------------------------------------------------

    \124\ Memorandum dated December 4, 2020, from Khoi Nguyen, Air 
Planning Office, EPA Region 9, to the docket for this proposed 
rulemaking, titled ``Adequacy Documentation for Plan Motor Vehicle 
Emission Budgets in 2018 Western Nevada County Ozone Plan.''
---------------------------------------------------------------------------

    Under our transportation conformity rule, as a general matter, once 
budgets are approved, they cannot be superseded by revised budgets 
submitted for the same CAA purpose and the same period of years 
addressed by the previously approved SIP until the EPA approves the 
revised budgets as a SIP revision. In other words, as a general matter, 
such approved budgets cannot be superseded by revised budgets found 
adequate, but rather only through approval of the revised budgets, 
unless the EPA specifies otherwise in its approval of a SIP by limiting 
the duration of the approval to last only until subsequently submitted 
budgets are found adequate.\125\
---------------------------------------------------------------------------

    \125\ 40 CFR 93.118(e)(1).
---------------------------------------------------------------------------

    In this instance, CARB originally requested that we limit the 
duration of our approval of the budgets in the 2018 Western Nevada 
County Ozone Plan only until the effective date of the EPA's adequacy 
finding for any subsequently submitted budgets.\126\ However, in an 
email dated August 17, 2020, CARB indicated its decision to no longer 
request limited approval of the budgets for Western Nevada.\127\
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    \126\ CARB's request to limit the duration of the approval of 
the Western Nevada County ozone budgets is contained in a letter 
dated December 2, 2018, from Richard Corey, Executive Officer, CARB, 
to Mike Stoker, Regional Administrator, EPA Region IX.
    \127\ See email dated August 17, 2020 from Nesamani Kalandiyur, 
CARB, to EPA Region 9.
---------------------------------------------------------------------------

H. Other Clean Air Act Requirements Applicable to Serious Ozone 
Nonattainment Areas

    In addition to the SIP requirements discussed in the previous 
sections, the CAA includes certain other SIP requirements applicable to 
Serious ozone nonattainment areas, such as Western Nevada County. We 
describe these provisions and their current status below for 
informational purposes only.
1. Enhanced Vehicle Inspection and Maintenance Programs
    Section 182(c)(3) of the CAA requires states with ozone 
nonattainment areas classified under subpart 2 as Serious or above to 
implement an enhanced motor vehicle I/M program in each urbanized area 
within the nonattainment area, as defined by the Bureau of the Census, 
with a 1980 population of 200,000 or more. The requirements for those 
programs are provided in CAA section 182(c)(3) and 40 CFR part 51, 
subpart S.
    Consistent with the 2008 Ozone SRR, no new I/M programs are 
currently required for nonattainment areas for the 2008 ozone 
NAAQS.\128\ Further, because there are no urbanized areas in Nevada 
County, the Western Nevada County nonattainment area is not required to 
implement an enhanced I/M program. Nevada County has had a basic smog 
check program in place since 1998.\129\
---------------------------------------------------------------------------

    \128\ 2008 Ozone SRR, 80 FR 12264, 12283 (March 6, 2015).
    \129\ 2018 Western Nevada County Ozone Plan, page 50.
---------------------------------------------------------------------------

2. New Source Review Rules
    Section 182(a)(2)(C) of the CAA requires states to develop SIP 
revisions containing permit programs for each of its ozone 
nonattainment areas. The SIP revisions are to include requirements for 
permits in accordance with CAA sections 172(c)(5) and 173 for the 
construction and operation of each new or modified major stationary 
source for VOC and NOX anywhere in the nonattainment area. 
The 2008 Ozone SRR includes provisions and guidance for nonattainment 
NSR programs.\130\
---------------------------------------------------------------------------

    \130\ 80 FR 12264 (March 6, 2015).
---------------------------------------------------------------------------

    The 2018 Western Nevada County Ozone Plan cites District Rule 428, 
``New Source Review Requirements for New and Modified Major Sources in 
Federally Designated Non-attainment Areas,'' as amended by the District 
on June 27, 2016, as the rule that meets Serious area requirements for 
nonattainment NSR.\131\ Since the Plan's submittal, the District 
rescinded the previously adopted Rule 428 and concurrently adopted a 
new Rule 428, ``NSR Requirements for New and Modified Major Sources in 
Nonattainment Areas,'' on November 25, 2019. The rule was submitted to 
the EPA on February 19, 2020. We approved this version of Rule 428 into 
the SIP on November 20, 2020.\132\
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    \131\ 2018 Western Nevada County Ozone Plan, 40.
    \132\ 85 FR 74263 (November 20, 2020).
---------------------------------------------------------------------------

3. Clean Fuels Fleet Program
    Sections 182(c)(4)(A) and 246 of the CAA require California to 
submit to the EPA for approval into the SIP measures to implement a 
Clean Fuels Fleet Program. Section 182(c)(4)(B) of the CAA allows 
states to opt out of the federal clean-fuel vehicle fleet program by 
submitting a SIP revision consisting of a program or programs that will 
result in at least equivalent long-term reductions in ozone precursors 
and toxic air emissions.
    In 1994, CARB submitted a SIP revision to the EPA to opt out of the 
federal clean-fuel fleet program. The submittal included a 
demonstration that California's low-emissions vehicle program achieved 
emissions reductions at least as large as would be achieved by the 
federal program. The EPA approved the SIP revision to opt out of the 
federal program on August 27, 1999.\133\ There have been no changes to 
the federal Clean Fuels Fleet program since the EPA approved the 
California SIP revision to opt out of the federal program, and thus, no 
corresponding changes to the SIP are required. Thus, we find that the 
California SIP revision to opt out of the federal program, as approved 
in 1999, meets the requirements of CAA sections 182(c)(4)(A) and 246 
for Western Nevada County for the 2008 ozone NAAQS.
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    \133\ 64 FR 46849 (August 27, 1999).
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4. Gasoline Vapor Recovery
    Section 182(b)(3) of the CAA requires states to submit a SIP 
revision by November 15, 1992, that requires owners or operators of 
gasoline dispensing systems to install and operate gasoline vehicle 
refueling vapor recovery (``Stage II'') systems in ozone nonattainment 
areas classified as Moderate and above. California's ozone 
nonattainment areas implemented Stage

[[Page 2336]]

II vapor recovery well before the passage of the CAA Amendments of 
1990.\134\
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    \134\ General Preamble, 57 FR 13498 at 13514 (April 16, 1992).
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    Section 202(a)(6) of the CAA requires the EPA to promulgate 
standards requiring motor vehicles to be equipped with onboard 
refueling vapor recovery (ORVR) systems. The EPA promulgated the first 
set of ORVR system regulations in 1994 for phased implementation on 
vehicle manufacturers, and since the end of 2006, essentially all new 
gasoline-powered light and medium-duty vehicles are ORVR-equipped.\135\ 
Section 202(a)(6) also authorizes the EPA to waive the SIP requirement 
under CAA section 182(b)(3) for installation of Stage II vapor recovery 
systems after such time as the EPA determines that ORVR systems are in 
widespread use throughout the motor vehicle fleet. Effective May 16, 
2012, the EPA waived the requirement of CAA section 182(b)(3) for Stage 
II vapor recovery systems in ozone nonattainment areas regardless of 
classification.\136\ Thus, a SIP submittal meeting CAA section 
182(b)(3) is not required for the 2008 ozone NAAQS.
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    \135\ 77 FR 28772, at 28774 (May 16, 2012).
    \136\ See 40 CFR 51.126(b).
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    While a SIP submittal meeting CAA section 182(b)(3) is not required 
for the 2008 ozone NAAQS, under California State law (i.e., Health and 
Safety Code section 41954), CARB is required to adopt procedures and 
performance standards for controlling gasoline emissions from gasoline 
marketing operations, including transfer and storage operations. State 
law also authorizes CARB, in cooperation with local air districts, to 
certify vapor recovery systems, to identify defective equipment and to 
develop test methods. CARB has adopted numerous revisions to its vapor 
recovery program regulations and continues to rely on its vapor 
recovery program to achieve emissions reductions in ozone nonattainment 
areas in California.
    In Western Nevada County, the installation and operation of CARB-
certified vapor recovery equipment is required and enforced through 
NSAQMD Rule 215, ``Phase II Vapor Recovery System Requirements,'' which 
was most recently approved into the SIP on July 26, 2011.\137\
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    \137\ 76 FR 44493 (July 26, 2011).
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5. Enhanced Ambient Air Monitoring
    Section 182(c)(1) of the CAA requires that all ozone nonattainment 
areas classified as Serious or above implement measures to enhance and 
improve monitoring for ambient concentrations of ozone, NOX, 
and VOC, and to improve monitoring of emissions of NOX and 
VOC. The enhanced monitoring network for ozone is referred to as the 
Photochemical Assessment Monitoring Station (PAMS) network. The EPA 
promulgated final PAMS regulations on February 12, 1993.\138\
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    \138\ 58 FR 8452 (February 12, 1993).
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    Prior to 2006, the EPA's ambient air monitoring regulations in 40 
CFR part 58, ``Ambient Air Quality Surveillance,'' set forth specific 
SIP requirements (see former 40 CFR 52.20). In 2006, the EPA 
significantly revised and reorganized 40 CFR part 58.\139\ Under 
revised 40 CFR part 58, SIP revisions are no longer required; rather, 
compliance with EPA monitoring regulations is established through 
review of required annual monitoring network plans.\140\ The 2008 Ozone 
SRR made no changes to these requirements.\141\
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    \139\ 71 FR 61236 (October 17, 2006).
    \140\ 40 CFR 58.2(b) now provides ``The requirements pertaining 
to provisions for an air quality surveillance system in the SIP are 
contained in this part.''
    \141\ The 2008 ozone SRR addresses PAMS-related requirements at 
80 FR 12264, at 12291 (March 6, 2015).
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    The 2018 Western Nevada County Ozone Plan does not specifically 
address the enhanced ambient air monitoring requirement in CAA section 
182(c)(1). However, we note that CARB includes the ambient monitoring 
network within Western Nevada County, in its annual monitoring network 
plan that is submitted to the EPA, and that we have approved the most 
recent annual monitoring network plan (``Annual Network Plan Covering 
Monitoring Operations in 25 California Air Districts, July 2020'' or 
``2020 ANP'') with respect to Western Nevada County.\142\ In addition, 
CARB has fulfilled the requirement under 40 CFR part 58, Appendix D, 
section 5(h), to submit an enhanced monitoring plan for Western Nevada 
County.\143\ Based on our review and approval of the 2020 ANP with 
respect to Western Nevada County and CARB's submittal of an enhanced 
monitoring plan for Western Nevada County, we propose to find that CARB 
and the NSAQMD meet the enhanced monitoring requirements under CAA 
section 182(c)(1) for Western Nevada County with respect to the 2008 
ozone NAAQS.
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    \142\ Letter dated November 5, 2020, from Gwen Yoshimura, 
Manager, Air Quality Analysis Office, EPA Region IX, to Ravi 
Ramalingam, Chief, Consumer Products and Air Quality Assessment 
Branch, Air Quality Planning and Science Division, CARB.
    \143\ Letter dated November 9, 2020, from Dr. Michael T. 
Benjamin, Chief, Air Quality Planning and Science Division, CARB, to 
Meredith Kurpius, Assistant Director, EPA Region 9, enclosing the 
``2020 Monitoring Network Assessment (October 2020).'' The 
assessment includes a five-year network assessment and an updated 
enhanced monitoring plan, as required by 40 CFR 58, Appendix D, 
Section 5(a).
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IV. Proposed Action

    For the reasons discussed in this notice, under CAA section 
110(k)(3), the EPA is proposing to approve as a revision to the 
California SIP the following portions of the 2018 Western Nevada County 
Ozone Plan submitted by CARB on December 2, 2018:
     Base year emissions inventory element as meeting the 
requirements of CAA sections 172(c)(3) and 182(a)(1) and 40 CFR 51.1115 
for the 2008 ozone NAAQS;
     RACM demonstration element as meeting the requirements of 
CAA section 172(c)(1) and 40 CFR 51.1112(c) for the 2008 ozone NAAQS;
     Attainment demonstration element for the 2008 ozone NAAQS 
as meeting the requirements of CAA section 182(c)(2)(A) and 40 CFR 
51.1108;
     ROP demonstration element as meeting the requirements of 
CAA 182(b)(1) and 40 CFR 51.1110(a)(4)(i) for the 2008 ozone NAAQS;
     RFP demonstration element as meeting the requirements of 
CAA sections 172(c)(2), 182(b)(1), and 182(c)(2)(B), and 40 CFR 
51.1110(a)(4)(iii) for the 2008 ozone NAAQS;
     Motor vehicle emissions budgets for the RFP milestone and 
attainment year of 2020 (see Table 5) because they are consistent with 
the RFP and attainment demonstrations for the 2008 ozone NAAQS proposed 
for approval herein and meet the other criteria in 40 CFR 93.118(e);
    We are also proposing to find that the:
     California SIP revision to opt-out of the federal Clean 
Fuels Fleet Program meets the requirements of CAA sections 182(c)(4)(A) 
and 246 and 40 CFR 51.1102 for the 2008 ozone NAAQS with respect to 
Western Nevada County; and
     Requirements for enhanced monitoring under CAA section 
182(c)(1) and 40 CFR 51.1102 for Western Nevada County for the 2008 
ozone NAAQS have been met.
    In addition, we are proposing, under CAA section 110(k)(4), to 
approve conditionally the contingency measures element of the 2018 
Western Nevada County Ozone Plan as meeting the requirements of CAA 
sections 172(c)(9) and 182(c)(9) for RFP and attainment contingency 
measures. Our proposed approval is based on commitments by the District 
and CARB to supplement the element through submission, as a SIP 
revision (within one year of our

[[Page 2337]]

final conditional approval action), of a new District rule that would 
add new limits or other requirements if an RFP milestone is not met or 
if Western Nevada County fails to attain the 2008 ozone NAAQS by the 
applicable attainment date.

V. 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, or 
conditionally approve, state plans 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 proposed 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, Incorporation by 
reference, Intergovernmental relations, Nitrogen dioxide, Ozone, 
Reporting and recordkeeping requirements, Volatile organic compounds.

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

    Dated: December 21, 2020.
John Busterud,
Regional Administrator, Region IX.
[FR Doc. 2020-28885 Filed 1-11-21; 8:45 am]
BILLING CODE 6560-50-P