Document ID: EPA-R09-OAR-2021-0368-0001
Agency: epa
Document Type: Proposed Rule
Title: Air Quality State Implementation Plans; Approvals and Promulgations: Nevada; Revisions to Clark County Ozone Maintenance Plan
Posted Date: 2021-08-09T04:00Z

[Federal Register Volume 86, Number 150 (Monday, August 9, 2021)]
[Proposed Rules]
[Pages 43461-43469]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2021-16644]

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ENVIRONMENTAL PROTECTION AGENCY

40 CFR Part 52

[EPA-R09-OAR-2021-0368; FRL-8716-01-R9 ]

Air Plan Approval; Nevada; Revisions to Clark County Ozone 
Maintenance Plan

AGENCY: Environmental Protection Agency (EPA).

ACTION: Proposed rule.

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SUMMARY: The Environmental Protection Agency (EPA) is proposing to 
approve a revision to the State of Nevada's state implementation plan 
(SIP) for Clark County. The revision consists of an update to certain 
elements of the maintenance plan for the Clark County air quality 
planning area for the 1997 8-hour ozone national ambient air quality 
standards (NAAQS or ``standards''), including certain emissions 
inventories and motor vehicle emissions budgets. The EPA is proposing 
to approve the SIP revision because the Clark County ozone maintenance 
plan, as revised, continues to provide for maintenance of the 1997 
ozone NAAQS and will not interfere with attainment or reasonable 
further progress of the other NAAQS, and the motor vehicle emissions 
budgets meet the applicable transportation conformity requirements.

DATES: Comments must be received on or before September 8, 2021.

ADDRESSES: Submit your comments, identified by Docket ID No. EPA-R09-
OAR-2021-0368, 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: Karina O'Connor, Air Planning Office 
(AIR-2), EPA Region IX, 75 Hawthorne Street, San Francisco, CA 94105; 
By phone: (775) 434-8176 or by email at oconnor.karina@epa.gov.

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

Table of Contents

I. What action is the EPA proposing?
II. Background
    A. NAAQS, SIPs, Designations, and Clark County
    B. 2008 and 2015 Ozone NAAQS
    C. Transportation Conformity and the 2018 Ozone Maintenance Plan 
Revision
III. What did the State submit?
IV. Procedural Requirements for Adoption and Submittal of SIP 
Revisions
V. The EPA's Evaluation of the 2020 Ozone Maintenance Plan Revision
    A. Emission Inventories
    B. Revised Motor Vehicle Emissions Budgets
    C. CAA Section 110(l) Evaluation
VI. Proposed Action and Request for Public Comment
VII. Statutory and Executive Order Reviews

I. What action is the EPA proposing?

    Under section 110(k) of the Clean Air Act (``Act'' or CAA), the EPA 
is required to take action by approving, disapproving, or conditionally 
approving, in whole or in part, SIPs and SIP revisions submitted by the 
states. In today's action, the EPA is proposing to approve a SIP 
revision titled ``Revision to Motor Vehicle Emissions Budgets for the 
1997 Ozone NAAQS, Clark County, Nevada'' (August 2020) (herein, 
referred to as the ``2020 Ozone Maintenance Plan Revision''), submitted 
by the Nevada Division of Environmental Protection (NDEP) on September 
30, 2020.\1\ The 2020 Ozone Maintenance Plan Revision updates certain 
elements of the maintenance plan for Clark County for the 1997 ozone 
NAAQS, including certain emissions inventories and the motor vehicle 
emissions budgets (``budgets'' or MVEBs). The 2020 Ozone Maintenance 
Plan Revision was prepared in response to the EPA's conditional 
approval of the ``Revision to Motor Vehicle Emissions Budgets in Ozone 
Redesignation Request and Maintenance Plan: Clark County,

[[Page 43462]]

Nevada'' (October 2018) (herein, referred to as the ``2018 Ozone 
Maintenance Plan Revision'').\2\ The 2020 Ozone Maintenance Plan 
Revision revises certain budgets from the 2018 Ozone Maintenance Plan 
Revision to prevent interference with reasonable further progress or 
attainment of the 2008 and 2015 ozone NAAQS. If the EPA takes final 
action to approve the 2020 Ozone Maintenance Plan Revision, the revised 
budgets will replace Clark County's existing budgets for the plan 
horizon year (2022) for the 1997 ozone NAAQS. At that time, the 
previously-approved budgets would no longer be applicable for 
transportation conformity purposes, and the revised budgets would need 
to be used beginning on the publication date of the EPA's final 
approval in the Federal Register.\3\
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    \1\ NDEP submitted the 2020 Ozone Maintenance Plan Revision 
electronically on September 30, 2020, as an attachment to a 
transmittal letter dated September 25, 2020.
    \2\ 84 FR 44699 (August 27, 2019).
    \3\ 40 CFR 93.118(f)(2)(v).
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II. Background

A. NAAQS, SIPs, Designations, and Clark County

    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. Under 
CAA section 107(d), the EPA must designate all areas of the country as 
attainment, nonattainment or unclassifiable for new or revised NAAQS. 
Section 110 of the CAA requires states to develop and submit SIPs to 
implement, maintain, and enforce the NAAQS. Once a nonattainment area 
has attained the NAAQS, the state may request redesignation of the area 
from nonattainment to attainment, and the EPA grants such requests if 
the criteria in CAA section 107(d)(3)(E) are met, including the 
approval of a maintenance plan (under CAA section 175A) that 
demonstrates how the area will maintain the NAAQS for at least 10 years 
after the redesignation. Such former nonattainment areas that have been 
redesignated to attainment are referred to as ``maintenance areas.''
    In 1997, the EPA replaced the 1-hour ozone \4\ NAAQS at a level of 
0.12 parts per million (ppm) with an 8-hour ozone NAAQS at a level of 
0.08 ppm (herein, the ``1997 ozone NAAQS'').\5\ In 2004, the EPA 
designated a portion of Clark County as a ``Subpart 1'' nonattainment 
area for the 1997 ozone NAAQS.\6\ In 2011, the EPA determined that the 
Clark County 8-hour ozone nonattainment area had attained the 1997 8-
hour ozone NAAQS, based on complete, quality-assured, and certified 
ambient air monitoring data that showed the area monitored attainment 
of the 1997 ozone NAAQS for the 2007-2009 monitoring period.\7\
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    \4\ Ground-level ozone pollution is formed from the reaction of 
volatile organic compounds (VOC) and oxides of nitrogen 
(NOX) in the presence of sunlight. 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.
    \5\ 62 FR 38856 (July 18, 1997) and 40 CFR 50.10.
    \6\ 69 FR 23858 (April 30, 2004) and 69 FR 55956 (September 17, 
2004). The Clark County ozone nonattainment area for the 1997 ozone 
NAAQS includes a significant portion of the unincorporated portions 
of central and southern Clark County, as well as the cities of Las 
Vegas, Henderson, North Las Vegas, and Boulder City. The ``Subpart 
1'' classification meant that the area was subject solely to the 
general nonattainment area requirements under subpart 1 of part D 
(of title I) of the CAA rather than to the requirements under both 
subparts 1 and the ozone-specific requirements under subpart 2. 
Several years later, in response to litigation over the designations 
for the 1997 ozone NAAQS, the EPA revised the classification of the 
Clark County ozone nonattainment area from ``Subpart 1'' to 
``Subpart 2/Marginal.'' 77 FR 28424 (May 14, 2012).
    \7\ 76 FR 17343 (March 29, 2011).
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    In light of ambient monitoring data showing that the Clark County 
ozone nonattainment area had attained the 1997 ozone NAAQS, NDEP 
submitted a request to redesignate the Clark County ozone area from 
nonattainment to attainment and submitted the ``Ozone Redesignation 
Request and Maintenance Plan, Clark County, Nevada (March 2011)'' 
(herein, the ``2011 Ozone Maintenance Plan'') to the EPA for approval 
as a revision to the Clark County portion of the Nevada SIP. Prepared 
by the Clark County Department of Air Quality and Environmental 
Management (currently named ``Department of Environment and 
Sustainability'' (DES)),\8\ the 2011 Ozone Maintenance Plan includes 
the required elements for maintenance plans, including an attainment 
inventory, maintenance demonstration, monitoring network, verification 
of continued attainment, contingency plan, and budgets.\9\ The 2011 
Ozone Maintenance Plan demonstrates maintenance of the 1997 ozone NAAQS 
through year 2022 by reference to emissions inventories developed for 
years 2015 and 2022 that show emissions of volatile organic compounds 
(VOC) and oxides of nitrogen (NOX) in those years would not 
exceed the level of the corresponding emissions of the 2008 attainment 
inventory. The 2011 Ozone Maintenance Plan established budgets for 
NOX and VOC for years 2008, 2015, and 2022. The budgets were 
derived from the on-road motor vehicle emissions estimates prepared 
using the EPA's then-current on-road vehicle emissions model, 
MOBILE6.2, and the most recent vehicle mix and activity data available 
from the Regional Transportation Commission of Southern Nevada. In 
2013, the EPA approved the 2011 Ozone Maintenance Plan and redesignated 
the Clark County ozone nonattainment area to attainment for the 1997 
ozone NAAQS.\10\
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    \8\ In the State of Nevada, NDEP is the Governor's designee for 
adoption and submittal of SIPs and SIP revisions to the EPA. In 
Clark County, the Clark County DES is responsible under state law 
for regulation of most types of stationary sources within the county 
and for development of local air quality plans. Once adopted by the 
Clark County Board of County Commissioners, such county plans are 
forwarded to NDEP for adoption and submittal to the EPA as revisions 
to the Nevada SIP.
    \9\ Under the EPA's transportation conformity rule, at 40 CFR 
93.101, budgets are defined as the portions of the total allowable 
emissions that are allocated to on-road vehicle use that, together 
with emissions from other sources in the area, will provide for RFP, 
attainment or maintenance. The budgets serve as a ceiling on 
emissions from an area's planned transportation system.
    \10\ 78 FR 1149 (January 8, 2013).
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    Through adoption of the 2011 Ozone Maintenance Plan, Clark County 
DES committed to maintaining an ambient air quality monitoring network 
to verify the continued attainment of the 1997 ozone NAAQS in the Clark 
County ozone maintenance area.\11\ At the present time, 10 monitoring 
sites continuously monitor ambient concentrations of ozone within the 
maintenance area. Since 2008, i.e., the year used for the attainment 
inventory in the 2011 Ozone Maintenance Plan, ambient ozone 
concentrations in Clark County have decreased. As shown in Table 1, 8-
hour ozone design values have decreased from 0.082 ppm in 2008 to 0.073 
ppm in 2019.\12\ In more recent years, the design value has remained 
relatively steady, varying little from year to year. Table 1 shows that 
Clark County has maintained the 1997 ozone NAAQS through the first 
seven years (2013 through 2019) of the first maintenance period.
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    \11\ 2011 Ozone Maintenance Plan, 6-11.
    \12\ Under EPA regulations at 40 CFR 50.10 and appendix I, the 
1997 ozone NAAQS is attained at a site when the 3-year average of 
the annual fourth-highest daily maximum 8-hour average ozone 
concentration is less than or equal to 0.08 ppm. This 3-year average 
is referred to as the design value. When the design value is less 
than or equal to 0.084 ppm (based on the rounding convention in 40 
CFR part 50, appendix I) at each monitoring site within the area, 
then the area is meeting the 1997 ozone NAAQS. The highest design 
value among the various ozone monitoring sites represents the design 
value for the area.

[[Page 43463]]

   Table 1--Eight-Hour Ozone Design Values for the Clark County Ozone
                       Maintenance Area, 2008-2020
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                                                           Design  value
                          Year                                 (ppm)
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2008....................................................           0.082
2009....................................................           0.078
2010....................................................           0.076
2011....................................................           0.075
2012....................................................           0.076
2013....................................................           0.077
2014....................................................           0.078
2015....................................................           0.075
2016....................................................           0.075
2017....................................................           0.074
2018....................................................           0.076
2019....................................................           0.073
2020....................................................           0.074
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Source: The EPA's 2017 and 2020 Ozone Design Values Reports at https://www.epa.gov/air-trends/air-quality-design-values#report. Note that
  design values reported for a given year reflect data from that year
  and the two previous years, e.g., the design value for 2008 reflects
  data from 2006-2008.

B. 2008 and 2015 Ozone NAAQS

    In 2008, the EPA lowered the ozone NAAQS to a level of 0.075 ppm, 
8-hour average (herein, the ``2008 ozone NAAQS''),\13\ and in 2012, the 
EPA designated all of the hydrographic areas within the State of Nevada 
as ``Unclassifiable/Attainment'' for the 2008 ozone NAAQS.\14\ Because 
all the hydrographic areas located entirely, or partially, within Clark 
County were designated as unclassifiable/attainment for the 2008 ozone 
NAAQS, no reasonable further progress (RFP) or attainment SIP revision 
was required for any portion of the county.
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    \13\ 73 FR 16436 (March 27, 2008) and 40 CFR 50.15.
    \14\ 77 FR 30088 (May 21, 2012). Hydrographic areas are those 
that are shown on the State of Nevada Division of Water Resources' 
map titled ``Water Resources and Inter-basin Flows'' (September 
1971).
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    In 2015, the EPA further lowered the ozone NAAQS to 0.070 ppm, 8-
hour average (herein the ``2015 ozone NAAQS'').\15\ In 2018, the EPA 
designated the Las Vegas Valley portion of Clark County as a 
``Marginal'' nonattainment area for the 2015 ozone NAAQS, effective 
August 3, 2018.\16\ The nonattainment area designation for Las Vegas 
Valley for the 2015 ozone NAAQS triggered the requirement for certain 
SIP revisions under CAA section 182(a) and the EPA's related SIP 
Requirements Rule promulgated at 40 CFR part 51, subpart CC.
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    \15\ 80 FR 65292 (October 26, 2015) and 40 CFR 50.19.
    \16\ 83 FR 25776 (June 4, 2018).
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C. Transportation Conformity and the 2018 Ozone Maintenance Plan 
Revision

    The EPA's transportation conformity rule at 40 CFR part 93, subpart 
A establishes the criteria and procedures that metropolitan planning 
organizations (MPOs) and the U.S. Department of Transportation (DOT) 
must use to determine whether transportation activities conform to the 
SIP. Transportation conformity applies to areas that are designated 
nonattainment and those former nonattainment areas that have been 
redesignated to attainment and have a CAA section 175A maintenance plan 
(``maintenance areas''), but does not apply to areas designated as 
attainment or unclassifiable.\17\ In Clark County, the area's MPO, the 
Regional Transportation Commission of Southern Nevada (RTC), and DOT 
are the relevant transportation agencies that must determine the 
conformity of transportation plans and transportation improvement plans 
(TIPs) within Clark County.
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    \17\ CAA section 176(c)(5).
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    Under our transportation conformity rule, the latest approved or 
adequate emissions budgets for a previous ozone NAAQS (i.e., the 2008 
or the 1997 ozone NAAQS) must be used in conformity determinations for 
the 2015 ozone NAAQS until emission budgets are established and found 
adequate or are approved for the 2015 ozone NAAQS. Because the latest 
approved or adequate emissions budgets for a previous ozone NAAQS for 
Clark County are the approved budgets for the 1997 8-hour ozone NAAQS, 
the RTC and DOT must use these budgets for conformity determinations 
for the 2015 ozone NAAQS \18\ until they are replaced by updated 
budgets for the 2015 ozone NAAQS.
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    \18\ The EPA's guidance ``Transportation Conformity Guidance for 
the South Coast II Court Decision'' (November 2018, EPA-20-B-18-
050), explains that while conformity requirements continue to apply 
for the revoked 1997 ozone NAAQS, conformity can be demonstrated 
without a regional emissions analysis for the 1997 ozone standard.
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    In 2018, NDEP submitted the 2018 Ozone Maintenance Plan Revision as 
a revision to the Clark County portion of the Nevada SIP. The 2018 
Ozone Maintenance Plan Revision includes revisions to the attainment 
inventory, the maintenance demonstration, and budgets in the 2011 Ozone 
Maintenance Plan to reflect updated emissions models, vehicle mix and 
speed data, and transportation activity projections. The 2018 Ozone 
Maintenance Plan Revision revised the budgets for NOX and 
VOC for years 2008, 2015, and 2022. The revised budgets were derived 
from the on-road motor vehicle emissions estimates prepared using the 
most recent version of the EPA's on-road vehicle emissions model 
available at the time (MOVES2014a) and updated planning variables 
(e.g., vehicle miles traveled projections and population forecasts) 
from the RTC. The 2018 Ozone Maintenance Plan Revision was developed so 
that the RTC and DOT would have updated budgets available to use for 
transportation conformity determinations with respect to the 2015 ozone 
NAAQS until budgets developed specifically for the 2015 ozone NAAQS are 
adopted and found to be adequate or approved. In 2019, the EPA 
conditionally approved the 2018 Ozone Maintenance Plan Revision as a 
revision of the Clark County portion of the Nevada SIP.\19\
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    \19\ 84 FR 44699 (August 27, 2019).
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    In so doing, we found that the 2011 Ozone Maintenance Plan, as 
revised by the updated attainment inventory and maintenance 
demonstration in the 2018 Ozone Maintenance Plan Revision, continues to 
provide for maintenance of the 1997 ozone NAAQS, and upon fulfillment 
of the commitments made by NDEP and Clark County DES to reduce the 
safety margin allocations for the budgets, will not interfere with RFP 
or attainment of the other NAAQS in Clark County. In conditionally 
approving the 2018 Ozone Maintenance Plan Revision, the EPA also found 
adequate and conditionally approved the updated NOX and VOC 
budgets for 2008, 2015, and 2022 for the 1997 ozone NAAQS based on our 
conclusion that the updated budgets meet the applicable transportation 
conformity requirements. The approval was conditional because it is 
based on commitments by Clark County DES and NDEP to submit an 
additional SIP revision to reduce the safety margin allocations for the 
budgets in the 2018 Ozone Maintenance Plan Revision within one year of 
this final conditional approval.
    In September 2020, NDEP submitted the 2020 Ozone Maintenance Plan 
Revision to the EPA in fulfillment of the commitments made by Clark 
County DES and NDEP in connection with the EPA's conditional approval 
of the 2018 Ozone Maintenance Plan Revision. The 2020 Ozone Maintenance 
Plan Revision is the subject to today's proposed action.

III. What did the State submit?

    On August 18, 2020, the Clark County Board of County Commissioners 
adopted the 2020 Ozone Maintenance Plan Revision and forwarded the plan 
to NDEP for adoption and submittal to the

[[Page 43464]]

EPA.\20\ On September 30, 2020, NDEP submitted the 2020 Ozone 
Maintenance Plan Revision to the EPA as a revision to the Clark County 
portion of the Nevada SIP.\21\ The 2020 Ozone Maintenance Plan Revision 
also includes a technical support document (appendix A of the plan 
revision) and documentation of the public review process (appendix B of 
the plan revision).
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    \20\ Clark County Board of County Commissioners Meeting, Meeting 
Summary, October 16, 2018, 14 and 15.
    \21\ Letter dated September 25, 2020, from Greg Lovato, 
Administrator, NDEP to Elizabeth Adams, Director, Air Division, EPA 
Region IX, (submitted electronically on September 30, 2020 with 
enclosures).
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    Through the 2020 Ozone Maintenance Plan Revision, Clark County DES 
is updating the emissions projections for the ozone maintenance plan 
horizon year of 2022 based on the latest available emissions models, 
vehicle mix and speed data, and transportation activity projections and 
is revising the budgets for 2022 to reflect the updated projections for 
that year and to include a reduced safety margin compared to the 
corresponding budgets from the 2018 Ozone Maintenance Plan Revision. 
The 2020 Ozone Maintenance Plan Revision also presents a new emissions 
inventory for year 2017 that provides the basis to evaluate the new 
budgets with respect to continued attainment of the 2008 ozone NAAQS 
and progress towards attainment of the 2015 ozone NAAQS in Las Vegas 
Valley.

IV. Procedural Requirements for Adoption and Submittal of SIP Revisions

    Sections 110(a)(1) and (2) and 110(l) of the CAA require a state to 
provide reasonable public notice and opportunity for public hearing 
prior to the adoption and submittal 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.
    The Clark County Board of County Commissioners and NDEP have 
satisfied applicable statutory and regulatory requirements for 
reasonable public notice and public hearing prior to adoption and 
submittal of the 2020 Ozone Maintenance Plan Revision. In the September 
30, 2020 SIP submittal,\22\ Clark County DES provided evidence of the 
required public notice and opportunity for public comment prior to the 
August 18, 2020 public hearing and adoption of the 2020 Ozone 
Maintenance Plan Revision. Therefore, we find that the submittal of the 
2020 Ozone Maintenance Plan Revision meets the procedural requirements 
for public notice and hearing in CAA sections 110(a) and 110(l) and 40 
CFR 51.102.
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    \22\ Appendix B provides evidence that reasonable notice of a 
public hearing was provided to the public and that a public hearing 
was conducted prior to adoption. Specifically, notice of the 
availability of, and opening of a 30-day comment period on the draft 
ozone maintenance plan revision was published on June 25, 2020, on 
the County's webpage. No comments were submitted.
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V. The EPA's Evaluation of the 2020 Ozone Maintenance Plan Revision

    Clark County DES and NDEP submitted the 2020 Ozone Maintenance Plan 
Revision to fulfill commitments made in connection with the EPA's 
conditional approval of the 2018 Ozone Maintenance Plan Revision to 
reduce the safety margin allocations in the budgets to ensure that the 
Clark County ozone SIP will not interfere with RFP or attainment of the 
2008 and 2015 ozone NAAQS consistent with CAA section 110(l). As 
described further below, we have reviewed the 2020 Ozone Maintenance 
Plan Revision for compliance with the relevant requirements for 
maintenance plans under CAA section 175A and for noninterference under 
CAA section 110(l), and we have evaluated the budgets in the 2020 Ozone 
Maintenance Plan Revision for compliance with the budget adequacy 
criteria in 40 CFR 93.118(e).

A. Emissions Inventories

    The 2020 Ozone Maintenance Plan Revision includes inventories of 
emissions of ozone precursors (VOC and NOX) for years 2017 
and 2022. The 2017 inventory provides estimates of actual emissions 
that occurred in that year. Clark County DES selected 2017 as the base 
year for the 2020 Ozone Maintenance Plan Revision for the following 
reasons: It is the most recent year for which National Emissions 
Inventory \23\ (NEI) emissions estimates were available at the time the 
plan was being developed; it is an attainment year for the 2008 ozone 
NAAQS; and it is the base year for SIP planning purposes for the 2015 
ozone NAAQS. Clark County DES used the 2017 inventory to revise the 
2022 emissions inventory from the 2018 Ozone Maintenance Plan Revision 
based on the latest methods and planning assumptions.
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    \23\ The NEI is a comprehensive and detailed estimate of air 
emissions of criteria pollutants, criteria precursors, and hazardous 
air pollutants from air emissions sources. The NEI is released every 
three years based primarily upon data provided by State, Local, and 
Tribal air agencies for sources in their jurisdictions and 
supplemented by data developed by the EPA.
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    As a general matter, base year emissions inventories must be (1) 
consistent with the EPA's most recent guidance on emissions inventories 
available at the time, (2) comprehensive, including emissions from 
stationary point sources, area sources, nonroad mobile sources, and on-
road mobile sources, and (3) based on actual ``ozone season data'' 
(i.e., summertime) emissions.\24\
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    \24\ In Clark County, Nevada, the highest ambient ozone 
concentrations generally occur during the months of the year when 
the highest temperatures occur--typically from May through 
September. For SIP planning purposes, Clark County has selected 
weekdays in the month of July as the basis to estimate typical 
summertime weekday emissions.
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    The 2017 year inventory in the 2020 Ozone Maintenance Plan Revision 
is comprehensive in that it includes estimates of summertime average 
weekday VOC and NOX emissions from all of the relevant 
source categories, which the plan divides among point sources,\25\ 
nonpoint sources,\26\ commercial aviation, federal aviation (i.e., 
Nellis Air Force Base), on-road mobile, nonroad mobile, and biogenic 
\27\ sources.\28\ For comparison, the 2018 Ozone Maintenance Plan 
Revision did not include a 2017 inventory, but emissions for 2017 can 
be interpolated from 2015 and 2022 emissions. Appendix A to the 2020 
Ozone Maintenance Plan Revision contains source-specific descriptions 
of emission calculation procedures and sources of input data used for 
the update.
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    \25\ The 2020 Ozone Maintenance Plan Revision uses the term, 
``point sources,'' to refer to those stationary source facilities 
that are required to report their emissions to Clark County DES or 
NDEP.
    \26\ The 2020 Ozone Maintenance Plan Revision uses the term, 
``nonpoint sources,'' to refer to those stationary and area sources 
that fall below point source reporting levels and that are too 
numerous or small to identify individually.
    \27\ For the 2020 Ozone Maintenance Plan Revision, ``biogenic 
sources'' include the following: Agricultural crops; lawn grass; 
forests that produce isoprene, monoterpene, alpha-pinene, and other 
VOC emissions; and soils that generate trace amounts of 
NOX.
    \28\ See Table 2-1 in the 2020 Ozone Maintenance Plan Revision.
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    Table 2 below compares the 2017 inventory from the 2020 Ozone 
Maintenance Plan Revision with the corresponding interpolated inventory 
from the 2018 Ozone Maintenance Plan Revision. As shown in Table 2, the 
change in the 2017 inventory in the 2020 Ozone Maintenance Plan 
Revision is primarily due to the update to the on-road mobile source 
category and the nonroad source category as well as a change in the 
methodology for biogenic emissions.

[[Page 43465]]

                          Table 2--2017 Clark County Ozone Precursor Emission Inventory
                               [County-wide, average summer weekday, tons per day]
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                                                           NOX emissions                   VOC emissions
                                                 ---------------------------------------------------------------
                 Source category                    2020 Ozone      2018 Ozone      2020 Ozone      2018 Ozone
                                                    maintenance     maintenance     maintenance     maintenance
                                                   plan revision   plan revision   plan revision   plan revision
----------------------------------------------------------------------------------------------------------------
Point source....................................           12.40           11.79            2.95            2.51
Nonpoint source.................................           7.651            5.68           62.56           59.94
Commercial aviation.............................           11.47           13.38            1.73            2.75
Federal aviation................................            0.50            1.77            0.24            1.04
On-road mobile..................................           46.96           53.65           29.47           28.49
Nonroad mobile..................................           37.45           24.78           28.25           30.36
Biogenic........................................            2.43            5.00          362.61          132.00
                                                 ---------------------------------------------------------------
    Total.......................................          118.86          116.06          487.81          257.09
----------------------------------------------------------------------------------------------------------------
Sources: 2018 Ozone Maintenance Plan Revision, interpolated values from Tables 2-1 and 2-2; 2020 Ozone
  Maintenance Plan Revision, Tables 2-1 and 2-2.

    With respect to on-road mobile source emissions, Clark County DES 
updated the emissions estimates using MOVES2014b, RTC travel demand 
modeling, and highway performance monitoring system data from the 
Nevada Department of Transportation.\29\ Clark County DES also selected 
the inventory mode, rather than the emission rate mode used in the 2018 
Ozone Maintenance Plan Revision, with MOVES2014b emissions factors and 
projected emissions for 2022 from 2017 rather than 2015. Generally, on-
road mobile source emissions estimates made using MOVES2014b are 
similar to MOVES2014a. With respect to nonroad emissions sources, the 
change in the 2017 emissions inventory is largely due to the use of the 
nonroad module of MOVES2014b that was released in August 2018. Clark 
County DES used default estimates from MOVES2014b for Clark County and 
the most significant changes were in the two largest sectors: 
construction and lawn/garden, which increased and decreased, 
respectively. Overall, nonroad emissions are higher for NOX 
but lower for VOC using MOVES2014b compared to using the nonroad module 
of MOVES2014a.
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    \29\ 2020 Ozone Maintenance Plan Revision, Appendix A, 4-12.
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    Biogenic emissions for Clark County were developed using the EPA's 
Biogenic Emission Inventory System \30\ (BEIS) version 3.61, which 
replaced the Emissions of Gasses and Aerosols from Nature (MEGAN) model 
used by Clark County DES for the 2011 Ozone Maintenance Plan \31\ and 
the 2018 Ozone Maintenance Plan Revision. The BEIS model allows for 
interactions between air quality and meteorology. In 2017, the EPA 
updated the BEIS v3.61 to include the biogenic emissions landcover 
database version 5 (BELD5) and the newer version of the forest 
inventory and analysis version 8.0. This updated model improved the 
biogenic VOC emissions estimates. Clark County DES used the updated 
BEIS model, which is part of SMOKE 4.7 (Sparse Matrix Operator Kerner 
Emissions) model, to generate the biogenic emissions for Clark 
County.\32\ The results show a slight decrease in NOX and 
large increase in VOC biogenic emissions relative to the corresponding 
emissions estimates from the 2011 Ozone Maintenance Plan and 2018 Ozone 
Maintenance Plan Revision.
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    \30\ https://www.epa.gov/air-emissions-modeling/biogenic-emission-inventory-system-beis.
    \31\ 2011 Ozone Maintenance Plan, 6-4.
    \32\ 2020 Ozone Maintenance Plan Revision, 14.
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    Based on our review of the emissions inventories (and related 
documentation) from the 2020 Ozone Maintenance Plan Revision, we find 
that the inventories for 2017 are comprehensive, that the methods and 
assumptions used by Clark County DES to develop the 2017 emission 
inventory are reasonable, and that the inventories reasonably estimate 
actual ozone season emissions in 2017. Moreover, we find that the 2017 
emissions inventories in the plan reflect the latest planning 
assumptions and emissions models available at the time the 2020 Ozone 
Maintenance Plan Revision was developed.
    To provide the basis for the comparison of future emissions with 
the updated 2017 emissions, Clark County DES updated the 2022 emissions 
inventories using the same approaches as described above for the 2017 
emissions inventory. Clark County DES allocated the same amount of 
emissions reductions credits (ERCs), for use in connection with the new 
major stationary source permitting program, for 2022 as had been 
allocated for that year in the 2018 Ozone Maintenance Plan Revision. 
With respect to transportation conformity safety margins, as described 
further in section V.B of this document, the Clark County DES 
significantly reduced the safety margins that had been included in 
budgets for the 2018 Ozone Maintenance Plan Revision. Table 3 below 
compares the NOX and VOC emissions inventories, 
respectively, for 2022 from the 2020 Ozone Maintenance Plan Revision 
with the corresponding values from the 2018 Ozone Maintenance Plan 
Revision.

                          Table 3--2022 Clark County Ozone Precursor Emission Inventory
                               [County-wide, average summer weekday, tons per day]
----------------------------------------------------------------------------------------------------------------
                                                           NOX emissions                   VOC emissions
                                                 ---------------------------------------------------------------
                 Source category                    2020 Ozone      2018 Ozone      2020 Ozone      2018 Ozone
                                                    maintenance     maintenance     maintenance     maintenance
                                                   plan revision   plan revision   plan revision   plan revision
----------------------------------------------------------------------------------------------------------------
Point source....................................           12.09           12.26            3.12            2.72

[[Page 43466]]

 
Nonpoint source.................................            7.57            5.04           62.58           59.49
Commercial aviation.............................           13.08           17.42            1.73            2.95
Federal aviation................................            1.97            2.26            0.82            0.95
On-road mobile..................................           29.16           27.02           20.92           17.12
Nonroad mobile..................................           24.93           17.50           26.71           28.52
Biogenic........................................            2.43            5.00          362.61          132.00
Emission reduction credits......................           22.23           22.23            0.43            0.43
Transportation conformity safety margins........            3.00           59.72            3.00           35.84
                                                 ---------------------------------------------------------------
    Total.......................................          116.46          168.45          484.92          280.02
----------------------------------------------------------------------------------------------------------------
Sources: 2018 Ozone Maintenance Plan Revision, Tables 2-1, 2-2 and 3-1; 2020 Ozone Maintenance Plan Revision,
  Tables 2-1, 2-2 and 3-1.

    As shown in Table 3, emissions for 2022 in the 2020 Ozone 
Maintenance Plan Revision are similar to the corresponding emissions in 
the 2018 Ozone Maintenance Plan Revision except for biogenic emissions. 
Similar to the comparison of the emission inventories for the year 
2017, differences are again primarily due to the updates to the on-road 
mobile source category, the nonroad source category, and the change in 
the methodology for biogenic emissions. The on-road mobile source 
emission estimates in the 2020 Ozone Maintenance Plan Revision reflect 
the most recent published data concerning vehicle registration data, 
vehicle miles traveled (VMT) temporal distribution, VMT mix profiles, 
vehicle speeds, and travel demand forecasts from RTC.\33\
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    \33\ Key references used by Clark County DES include Eastern 
Research Group's ``Clark County On-Road Vehicle Classification 
Study,'' final report, June 29, 2018, and the Coordinating Research 
Council's ``Improvement of Default Inputs for MOVES and SMOKE-MOVES, 
final report, February 2017.
---------------------------------------------------------------------------

    Based on our review of the methods, assumptions, and data sources, 
as described in Appendix A to the 2020 Ozone Maintenance Plan Revision, 
we find that the Clark County DES estimates for 2017 and 2022 for the 
various source categories to be based on the best available emissions 
models and data sources, and thus to provide a reasonable basis upon 
which to evaluate whether the area will continue to maintain the 1997 
ozone NAAQS through 2022 and whether the revised budgets for 2022 in 
the 2020 Ozone Maintenance Plan Revision would interfere with RFP or 
attainment of the 2008 and 2015 ozone NAAQS.

B. Revised Motor Vehicle Emissions Budgets

    Section 176(c) of the CAA requires federal actions in nonattainment 
and maintenance areas to conform to the SIP's goals of eliminating or 
reducing the severity and number of violations of the NAAQS and 
achieving timely 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.
    Under the transportation conformity rule, MPOs in nonattainment and 
maintenance areas coordinate with state and local air quality and 
transportation agencies, the EPA, the Federal Highway Administration, 
and the Federal Transit Administration to demonstrate that an area's 
regional transportation plans and TIPs conform to the applicable SIP. 
This demonstration is typically done by showing that estimated 
emissions from existing and planned highway and transit systems are 
less than or equal to the budgets contained in all control strategy or 
maintenance SIPs. Budgets are generally established for specific years 
and specific pollutants or precursors. Ozone maintenance plans should 
identify budgets for on-road emissions of ozone precursors 
(NOX and VOC) in the area for the last year of the 
maintenance period. Budgets may also be specified for additional years 
during the maintenance period.
    For budgets to be approvable, they must meet the EPA's adequacy 
criteria (40 CFR 93.118(e)(4) and (5)) and comply with all pertinent 
SIP requirements. With respect to maintenance plans, to meet these 
requirements, the budgets must be consistent with the maintenance plan 
and reflect all the motor vehicle control measures contained in the 
maintenance demonstration.\34\ 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.\35\ We will 
complete the adequacy review of the budgets in the 2020 Ozone 
Maintenance Plan Revision concurrent with our final action on the 2020 
Ozone Maintenance Plan Revision. The EPA is not required under its 
transportation conformity rule to find budgets adequate prior to 
proposing approval of them.\36\
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    \34\ 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.
    \35\ 40 CFR 93.118(f)(2).
    \36\ 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).
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    The 2020 Ozone Maintenance Plan Revision includes revised budgets 
for VOC and NOX for the last year of the initial maintenance 
period, i.e., 2022.\37\ The revised budgets from the 2020 Ozone 
Maintenance Plan Revision are shown in Table 4 below and compared with 
the corresponding budgets from the approved 2018 Ozone Maintenance

[[Page 43467]]

Plan Revision. As noted in section V.A of this document, Clark County 
DES developed the revised budgets using the latest emissions model 
(MOVES2014b) available at the time the 2020 Ozone Maintenance Plan 
Revision was being developed, and the most recent travel activity 
projections provided by the Nevada Department of Transportation and 
RTC. Therefore, we find that the revised budgets reflect the most 
recent planning forecasts and are based on the most recent emission 
factor data and approved calculation methods.
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    \37\ The 2020 Ozone Maintenance Plan Revision does not revise 
the 2015 budgets from the 2018 Ozone Maintenance Plan Revision that 
also included large safety margins; however, we note that, given the 
passage of time, the 2015 budgets from the 2018 Ozone Maintenance 
Plan Revision will no longer be used for conformity determinations 
and thus the failure to reduce the safety margins of the 2015 
budgets in the 2018 Ozone Maintenance Plan Revision is acceptable.
---------------------------------------------------------------------------

    A state may choose to allocate all or a portion of the safety 
margin \38\ under the EPA transportation conformity rule so long as 
such margins are explicitly quantified in the applicable plan and are 
shown to be consistent with attainment or maintenance of the NAAQS 
(whichever is relevant to the particular plan).\39\ For the 2020 Ozone 
Maintenance Plan Revision, Clark County DES allocated a 3 tons per day 
(tpd) safety margin for NOX and VOC in 2022 to the projected 
on-road emissions estimates for NOX and VOC.
---------------------------------------------------------------------------

    \38\ In this context, ``safety margin'' means the amount by 
which the total projected emissions from all sources of a given 
pollutant are less than the total emissions that would satisfy the 
applicable requirements for reasonable further progress, attainment 
or maintenance. With respect to the 2020 Ozone Maintenance Plan 
Revision, the safety margin is the difference between the projected 
emissions in 2022 of NOX and VOC and the actual emissions 
of NOX and VOC in the 2008 attainment year as updated in 
the 2018 Ozone Maintenance Plan Revision. The anthropogenic 
emissions (i.e., excluding biogenic emissions) of NOX and 
VOC in 2008 were approximately 178 tons per day (tpd) and 157 tpd, 
respectively. The 2020 Ozone Maintenance Plan Revision continues to 
provide for maintenance of the 1997 ozone NAAQS because the 
anthropogenic emissions of NOX and VOC in 2022 (including 
the ERCs and transportation conformity safety margins) would be 
approximately 114 tpd and 122 tpd, respectively, which is 
substantially less than the emissions in the attainment year (2008) 
for the 1997 ozone NAAQS.
    \39\ See 40 CFR 93.124(a).

                      Table 4--Clark County Year 2022 Ozone Motor Vehicle Emission Budgets
                                   [County-wide, average summer weekday, tpd]
----------------------------------------------------------------------------------------------------------------
                                                   2018 Ozone  maintenance  plan   2020 Ozone  maintenance  plan
                                                             revision                        revision
                 Source category                 ---------------------------------------------------------------
                                                        NOX             VOC             NOX             VOC
----------------------------------------------------------------------------------------------------------------
On-Road Mobile..................................           27.02           17.12           29.16           20.92
Transportation Conformity Safety Margins........           59.72           35.84            3.00            3.00
Budgets.........................................           86.74           52.96           32.16           23.92
----------------------------------------------------------------------------------------------------------------
Sources: 2018 Ozone Maintenance Plan Revision, Table 3-1; 2020 Ozone Maintenance Plan Revision, Table 3-1.

    As documented in a April 20, 2021 memorandum to the docket for this 
rulemaking, we find that the budgets in the 2020 Ozone Maintenance Plan 
Revision meet each adequacy criterion.\40\ In short, we reviewed the 
budgets in the 2020 Ozone Maintenance Plan Revision and found that they 
are consistent with the revised maintenance demonstration from the 2018 
Ozone Maintenance Plan Revision; 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 approve the 2022 budgets in the 2020 Ozone Maintenance Plan 
Revision. If we finalize our approval of the revised budgets in the 
2020 Ozone Maintenance Plan Revision, as proposed, they will replace 
the corresponding budgets for the 1997 ozone NAAQS from the 2018 Ozone 
Maintenance Plan Revision that we previously found adequate and 
conditionally approved for use in transportation conformity 
determinations.
---------------------------------------------------------------------------

    \40\ Memorandum dated April 20, 2021, from Karina O'Connor, Air 
Planning Office, EPA Region IX, ``Adequacy Documentation for Plan 
Motor Vehicle Emission Budgets in August 2020 Clark County Revision 
to Ozone Maintenance Plan.'' This memorandum has been uploaded to 
the docket (EPA-R09-OAR-2021-0368) for this rulemaking.
---------------------------------------------------------------------------

C. CAA Section 110(l) Evaluation

    In relevant part, CAA section 110(l) provides that the EPA shall 
not approve a SIP revision that would interfere with any applicable 
requirement concerning attainment or RFP of any of the NAAQS or any 
other applicable requirement of the CAA. The 2018 Ozone Maintenance 
Plan Revision established budgets that are larger than those that were 
previously approved from the 2011 Ozone Maintenance Plan. Thus, 
approval of the 2018 Ozone Maintenance Plan Revision accommodated a 
higher level of VOC and NOX emissions from on-road mobile 
source emissions than would otherwise be allowed under the previous 
budgets. In our approval of the 2018 Ozone Maintenance Plan Revision, 
we evaluated the higher level of VOC and NOX emissions with 
respect to the potential for interference with RFP and attainment of 
the NAAQS for which VOC and NOX are precursors, namely, the 
2008 and 2015 ozone NAAQS.\41\
---------------------------------------------------------------------------

    \41\ As a general matter, VOC and NOX are also 
considered precursors for course particulate matter 
(PM10) and fine particulate matter (PM2.5). In 
our conditional approval of the 2018 Ozone Maintenance Plan 
Revision, we concluded that the revised budgets, even with the 
substantial safety margins, would not interfere with attainment or 
maintenance of the PM10 or PM2.5 NAAQS. 84 FR 
33035, at 33043-33044 (July 11, 2019) (proposed rule), finalized at 
84 FR 44699 (August 27, 2019). Clark County is designated as 
attainment for the PM10 NAAQS and unclassifiable/
attainment for the PM2.5 NAAQS. 40 CFR 81.329. In this 
document, we are proposing approval of budgets that have been 
revised to substantially reduce the safety margins, and thus, the 
potential for interference with attainment or maintenance of the 
PM10 or PM2.5 NAAQS is even less than it was 
previously. As such, we find that approval of the 2020 Ozone 
Maintenance Plan Revision would not interfere with attainment or 
maintenance of the PM10 or PM2.5 NAAQS in 
Clark County.
---------------------------------------------------------------------------

    In our conditional approval of the 2018 Ozone Maintenance Plan 
Revision, we determined that if the 2018 Ozone Maintenance Plan 
Revision were revised to reduce the safety margin allocations to the 
budgets such that total estimated emissions in 2022 (with the 
allocations) would not exceed actual emissions in year 2017, then the 
updated budgets would not interfere with reasonable further progress or 
attainment of the 2008 and 2015 ozone NAAQS.
1. 2008 Ozone NAAQS
    As noted in Section II.B of this document, in 2012, the EPA 
designated all the hydrographic areas within the State of Nevada as 
unclassifiable/attainment for the 0.075 ppm 2008 ozone NAAQS based on 
ambient ozone concentration data for years 2009-2011.\42\ After the 
original designation, the 8-hour ozone design values within Clark 
County exceeded the 2008 ozone

[[Page 43468]]

NAAQS for a few years but, since 2015, the design values have generally 
returned to attainment levels for the 2008 ozone NAAQS. As shown in 
Table 1, the design value in year 2017 was 0.074 ppm, which is 
consistent with attainment of the 0.075 ppm 2008 ozone NAAQS. Thus, 
emissions of VOC and NOX in 2017 represent conditions under 
which Clark County meets the 2008 ozone NAAQS.
---------------------------------------------------------------------------

    \42\ Letter dated December 9, 2011, from Jared Blumenfeld, 
Regional Administrator, EPA Region IX, to Brian Sandoval, Governor, 
State of Nevada.
---------------------------------------------------------------------------

    In recognition of the need to avoid interference with attainment of 
the 2008 ozone NAAQS and progress toward attainment of the 2015 ozone 
NAAQS, NDEP and Clark County DES committed to submit a SIP revision to 
reduce the safety margin allocations to the 2022 budgets such that 
total estimated emissions in 2022 (with the allocations) would not 
exceed actual emissions in year 2017, a year in which Clark County was 
attaining the 2008 ozone NAAQS.
    As shown in Table 2 of this document, the 2020 Ozone Maintenance 
Plan Revision estimates year 2017 emissions in Clark County to be 
approximately 119 tpd of NOX and 488 tpd of VOC. In 2022, as 
shown in Table 3 of this document, the 2020 Ozone Maintenance Plan 
Revision estimates year 2022 emissions in Clark County to be 
approximately 116 tpd of NOX and 485 tpd of VOC, including 
the allocated ERCs for stationary sources and transportation conformity 
safety margins for on-road mobile sources. As such, ozone precursor 
emissions in year 2022 under the 2020 Ozone Maintenance Plan Revision 
would be less than those in 2017, a year in which Clark County was 
attaining the 2008 ozone NAAQS. As such, we find that the 2020 Ozone 
Maintenance Plan Revision would not interfere with attainment of the 
2008 ozone NAAQS in Clark County.
2. 2015 Ozone NAAQS
    In 2018, the EPA designated the Las Vegas Valley (i.e., 
hydrographic area #212) as a Marginal nonattainment area for the 0.070 
ppm 2015 ozone NAAQS based on ambient ozone concentration data for 
years 2015-2017.\43\ The 2017 ozone design value is 0.074 ppm. To 
attain the 0.070 ppm 2015 ozone NAAQS by the applicable Marginal area 
attainment date, i.e., by August 3, 2021, VOC and NOX 
emissions must decrease relative to those in 2017. NDEP and Clark 
County DES committed to revise the 2018 Ozone Maintenance Plan Revision 
and the associated safety margins for the budgets so that, the total 
projected emissions (with the reduced safety margin allocations) in 
year 2022 would be less than the actual emissions estimated for year 
2017, the base year for implementation of the 2015 ozone NAAQS.
---------------------------------------------------------------------------

    \43\ EPA, ``Nevada, Las Vegas Nonattainment Area, Final Area 
Designations for the 2015 Ozone National Ambient Air Quality 
Standards, Technical Support Document (TSD).''
---------------------------------------------------------------------------

    With respect to the 2015 ozone NAAQS, we are finding that ozone 
precursor emissions in year 2022 under the 2020 Ozone Maintenance Plan 
Revision would be less than those in 2017, the base year for 
implementation of the 2015 ozone NAAQS. As such, we find that the 2020 
Ozone Maintenance Plan Revision would not interfere with RFP towards 
attainment of the 2015 ozone NAAQS.

VI. Proposed Action and Request for Public Comment

    For the reasons discussed herein, under CAA section 110(k)(3), the 
EPA is proposing to approve the 2020 Ozone Maintenance Plan Revision 
submitted by NDEP on September 30, 2020, as a revision for the Clark 
County portion of the Nevada SIP. We are proposing to approve the 2020 
Ozone Maintenance Plan Revision because we find that the 2011 Ozone 
Maintenance Plan, as revised by the 2018 Ozone Maintenance Plan 
Revision, and as further revised by the 2020 Ozone Maintenance Plan 
Revision, continues to provide for maintenance of the 1997 ozone NAAQS 
and will not interfere with RFP or attainment of the other NAAQS in 
Clark County. The EPA is also proposing to approve the updated budgets 
for 2022 for the 1997 ozone NAAQS (shown in Table 4 of this document) 
based on our conclusion that the updated budgets meet the applicable 
transportation conformity and other CAA requirements.
    If the EPA takes final action to approve the 2020 Ozone Maintenance 
Plan Revision as proposed, the revised budgets will replace the 
corresponding approved budgets from the 2018 Ozone Maintenance Plan 
Revision, and RTC and DOT must use the revised budgets for future 
transportation conformity determinations for the 2015 ozone NAAQS until 
motor vehicle emissions budgets for that ozone NAAQS are found adequate 
or are approved.\44\
---------------------------------------------------------------------------

    \44\ In addition, if we finalize this action as proposed, we 
will be removing the conditional approval regulatory text found at 
40 CFR 52.1475(a).
---------------------------------------------------------------------------

    The EPA is soliciting public comments on the issues discussed in 
this document. We will accept comments from the public on this proposal 
for the next 30 days. We will consider these comments before taking 
final action.

VII. Statutory and Executive Order Reviews

    Under the Clean Air Act, the Administrator is required to approve a 
SIP submission that complies with the provisions of the Act and 
applicable federal regulations. 42 U.S.C. 7410(k); 40 CFR 52.02(a). 
Thus, in reviewing SIP submissions, the EPA's role is to approve state 
choices, provided that they meet the criteria of the Clean Air Act. 
Accordingly, this proposed action merely proposes to approve a state 
plan 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);
     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 (Public Law 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. The Las Vegas

[[Page 43469]]

Tribe of Paiute Indians of the Las Vegas Indian Colony has areas of 
Indian country geographically located within the Clark County 1997 
ozone maintenance area. 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 regulations, Nitrogen dioxide, Ozone, 
Reporting and recordkeeping requirements, Volatile organic compounds.

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

    Dated: July 19, 2021.
Deborah Jordan,
Acting Regional Administrator, EPA Region IX.
[FR Doc. 2021-16644 Filed 8-6-21; 8:45 am]
BILLING CODE 6560-50-P