Approval of Implementation Plans for Air Quality Planning Purposes; State of Nevada; Clark County Second 10-Year Maintenance Plan for the 1997 8-Hour Ozone Standard, 88300-88308 [2023-27874]
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[FR Doc. 2023–28100 Filed 12–20–23; 8:45 am]
BILLING CODE 8320–01–P
ENVIRONMENTAL PROTECTION
AGENCY
40 CFR Part 52
[EPA–R09–OAR–2022–0955; FRL–10549–
01–R9]
Approval of Implementation Plans for
Air Quality Planning Purposes; State of
Nevada; Clark County Second 10-Year
Maintenance Plan for the 1997 8-Hour
Ozone Standard
Environmental Protection
Agency (EPA).
ACTION: Proposed rule.
AGENCY:
The Environmental Protection
Agency (EPA) is proposing to approve,
as a revision of the Nevada state
implementation plan (SIP), the State’s
second 10-year plan for maintaining the
1997 8-hour ozone standard in Clark
County (‘‘Clark County Second
Maintenance Plan’’ or ‘‘Plan’’). The
Clark County Second Maintenance Plan
includes, among other elements, a base
year emissions inventory, a
maintenance demonstration,
contingency provisions, and motor
vehicle emissions budgets for use in
transportation conformity
determinations to ensure the continued
maintenance of the 1997 National
Ambient Air Quality Standards for
ozone (‘‘1997 ozone NAAQS’’ or ‘‘1997
8-hour ozone standard’’). With this
proposed rulemaking, the EPA is
initiating the adequacy process for the
2017, 2023, and 2033 motor vehicle
emissions budgets. The EPA is
proposing these actions because the SIP
revision meets the applicable statutory
and regulatory requirements for such
plans and motor vehicle emissions
budgets.
SUMMARY:
Comments must be received on
or before January 22, 2024.
ADDRESSES: Submit your comments,
identified by Docket ID No. EPA–R09–
OAR–2022–0955, 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
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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 a
disability 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:
Andrew Ledezma, EPA Region IX, 75
Hawthorne St., San Francisco, CA
94105. By phone: (415) 972–3985 or by
email at Ledezma.Andrew@epa.gov.
SUPPLEMENTARY INFORMATION:
Throughout this document, ‘‘we,’’ ‘‘us,’’
and ‘‘our’’ refer to the EPA.
Table of Contents
I. Summary of Proposed Action
II. Background
III. Second 10-Year Maintenance Plan
Submittal and Procedural Requirements
IV. Requirements for Second 10-Year
Maintenance Plans
V. Evaluation of the Clark County Second
Maintenance Plan
A. Monitoring Network Requirements
B. Attainment Inventory
C. Maintenance Demonstration
D. Verification of Continued Attainment
E. Contingency Provisions
F. Motor Vehicle Emissions Budgets for
Transportation Conformity
VI. Environmental Justice Considerations
VII. Proposed Action and Request for Public
Comment
VIII. Statutory and Executive Order Reviews
I. Summary of Proposed Action
Under Clean Air Act (CAA or ‘‘the
Act’’) section 110(k)(3), the EPA is
proposing to approve two submittals
from the Nevada Division of
Environmental Protection (NDEP) as a
revision to the Nevada SIP: the Clark
County Second Maintenance Plan dated
December 21, 2021, and a supplement to
the Clark County Second Maintenance
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Plan (‘‘Contingency Measure Revision’’)
dated August 16, 2023. In this action,
we refer to the Clark County Second
Maintenance Plan and the Contingency
Measure Revision collectively as the
‘‘Clark County Second Maintenance
Plan submittal.’’
The EPA is proposing to find that the
maintenance demonstration, showing
how the area will continue to attain the
1997 8-hour ozone NAAQS for 10
additional years beyond the approval
the State’s first 10-year plan for
maintaining the 1997 8-hour ozone
standard in Clark County (‘‘Clark
County First Maintenance Plan’’ or
‘‘first maintenance plan’’) (i.e., through
2033), and the contingency provisions,
describing the actions that Clark County
will take in the event of a future
monitored violation, meet all applicable
requirements for maintenance plans and
related contingency provisions in CAA
section 175A. The EPA is also proposing
to approve the motor vehicle emissions
budgets (MVEBs or ‘‘budgets’’) in the
Clark County Second Maintenance Plan
because we find they meet the
applicable transportation conformity
requirements under 40 CFR 93.118(e).
II. Background
Sections 108 and 109 of the CAA
govern the establishment, review, and
revision, as appropriate, of the NAAQS
to protect public health and welfare.
The CAA requires the EPA to
periodically review the air quality
criteria, the science upon which the
standards are based, and the standards
themselves. Ground-level ozone is one
of the criteria pollutants regulated under
the NAAQS.
Ground-level ozone is generally not
emitted directly by sources. Rather,
directly emitted oxides of nitrogen
(NOX) and volatile organic compounds
(VOC) react in the presence of sunlight
to form ground-level ozone, as a
secondary pollutant, along with other
secondary compounds. NOX and VOC
are ‘‘ozone precursors.’’ Reduction of
peak ground-level ozone concentrations
is typically achieved through
controlling VOC and NOX emissions.
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.1
1 ‘‘Fact Sheet—2008 Final Revisions to the
National Ambient Air Quality Standards for
Ozone,’’ dated March 2008.
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In 1997, the EPA revised the NAAQS
for ozone, setting it at 0.08 parts per
million (ppm) averaged over an 8-hour
time frame.2 The EPA set the 1997 8hour ozone standard based on scientific
evidence demonstrating that ozone
causes adverse health effects at lower
ozone concentrations and over longer
periods of time, than was understood
when the pre-existing 1-hour ozone
standard was set. The EPA determined
that the 1997 8-hour ozone NAAQS
would be more protective of human
health, especially for children and
adults who are active outdoors, and
individuals with a pre-existing
respiratory disease, such as asthma.3
In 2004, the EPA designated areas of
the country with respect to the 1997 8hour ozone NAAQS.4 Under the EPA’s
‘‘Phase 1’’ implementation rule for the
1997 8-hour ozone standard 5 an area
was classified under subpart 2 based on
its 8-hour ozone design value (i.e., the
3-year average annual fourth-highest
daily maximum 8-hour average ozone
concentration at the worst-case
monitoring site in the area or in its
immediate downwind environs), if it
had a 1-hour ozone design value 6 at the
time of designation at or above 0.121
ppm. All other areas were covered
under subpart 1 based on their 8-hour
ozone design values.7 Clark County was
designated as a subpart 1 ozone
nonattainment area by the EPA on April
30, 2004, based on air quality
monitoring data from 2001–2003. The
designation became effective on June 15,
2004. On September 17, 2004, the EPA
reduced the geographic extent of the
ozone nonattainment area to encompass
a portion, but not all, of Clark County.8
2 62
FR 38856 (July 18, 1997).
March 27, 2008 (73 FR 16436), the EPA
promulgated a revised 8-hour ozone standard of
0.075 ppm (the 2008 8-hour ozone standard), and
on May 21, 2012, the EPA designated the entire
state of Nevada unclassifiable/attainment for the
2008 8-hour ozone standard (77 FR 30088). This
rulemaking relates only to the 1997 8-hour ozone
standard and does not relate to the 2008 8-hour
ozone standard.
4 69 FR 23858 (April 30, 2004).
5 69 FR 23951, (April 30, 2004).
6 The design value for the 1-hour ozone standard
is the fourth-highest daily maximum 1-hour ozone
concentration over a three-year period at the worstcase monitoring site in the area.
7 69 FR 23951. The design value for the 8-hour
standard is the three-year average of the annual
fourth-highest daily maximum 8-hour ozone
concentration at the worst-case monitoring site in
the area.
8 69 FR 55956 (September 17, 2004), 70 FR 71612
(November 29, 2005), and 40 CFR 81.329. The
boundaries of the Clark County ozone
nonattainment area are defined in 40 CFR 81.329.
Specifically, the area is defined as: ‘‘That portion
of Clark County that lies in hydrographic areas
164A, 164B, 165, 166, 167, 212, 213, 214, 216, 217,
and 218 but excluding the Moapa River Indian
Reservation and the Fort Mojave Indian
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In South Coast Air Quality
Management Dist. v. EPA 9 the U.S.
Court of Appeals for the District of
Columbia Circuit (D.C. Circuit, or
‘‘Court’’) vacated the EPA’s Phase 1
implementation rule for the 1997 8-hour
ozone standard.10 In response to several
petitions for rehearing, the D.C. Circuit
clarified that the Phase 1 rule was
vacated only for those parts of the rule
that had been successfully challenged.11
The decision left intact the Court’s
rejection of the EPA’s reasons for
implementing the 8-hour ozone
standard in certain nonattainment areas
under subpart 1 in lieu of subpart 2 of
the CAA.
On May 14, 2012, in response to the
Court’s vacatur of the provision of the
Phase 1 rule for the 1997 8-hour ozone
standard that placed certain
nonattainment areas, including Clark
County solely under subpart 1, the EPA
classified Clark County as a marginal
ozone nonattainment area under subpart
2 of the CAA.12
On March 29, 2011, the EPA
determined that the Clark County 8hour 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 8-hour ozone
NAAQS for the 2007–2009 monitoring
period.13
On April 11, 2011, NDEP submitted
the Clark County First Maintenance
Plan and requested that the EPA
redesignate the Clark County 8-hour
ozone nonattainment area to attainment
for the 1997 8-hour ozone standard. On
January 8, 2013, the EPA approved the
Clark County First Maintenance Plan,
and redesignated the area from
nonattainment to attainment of the 1997
8-hour ozone NAAQS.14
On October 31, 2018, NDEP submitted
a Revision to Motor Vehicle Emissions
Budgets in Ozone Redesignation
Request and Maintenance Plan (‘‘2018
Ozone Maintenance Plan Revision’’).
The 2018 Ozone Maintenance Plan
Revision updated elements of the Clark
County First Maintenance Plan,
including the attainment inventory, the
maintenance demonstration, and the
budgets. The 2018 Ozone Maintenance
Reservation.’’ The area 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.
9 472 F.3d 882 (D.C. Cir. 2007).
10 69 FR 23951.
11 472 F.3d 882 (D.C. Cir. 2007).
12 77 FR 28424.
13 76 FR 17343.
14 78 FR 1149.
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Plan Revision established ozone season
budgets of 52.96 and 86.74 tons per day
(tpd) for VOC and NOX, respectively, for
2022 so that the area would have
updated budgets available to use for
transportation conformity
determinations with respect to the 2015
National Ambient Air Quality Standards
for ozone (‘‘2015 ozone NAAQS’’).15 On
August 27, 2019, the EPA conditionally
approved the 2018 Ozone Maintenance
Plan revisions, based on commitments
to submit an additional SIP revision to
reduce the safety margin allocations for
the budgets within one year of the final
conditional approval.16
On September 30, 2020, NDEP
submitted an additional Revision to
Motor Vehicle Emissions Budgets for the
1997 ozone NAAQS, Clark County,
Nevada (‘‘2020 Ozone Maintenance Plan
Revision’’). The 2020 Ozone
Maintenance Plan Revision was
prepared in response to the EPA’s
conditional approval of the 2018 Ozone
Maintenance Plan Revision. The 2020
Ozone Maintenance Plan Revision
revised certain budgets from the 2018
Ozone Maintenance Plan Revision to
prevent interference with Reasonable
Further Progress (RFP) or attainment of
the 2008 and 2015 ozone NAAQS. The
2020 Ozone Maintenance Plan Revision
established budgets of 23.92 and 32.16
tons per average summer day 17 for VOC
and NOX, respectively, for 2022. On
October 28, 2021, with the submittal of
the 2020 Ozone Maintenance Plan
Revision, the EPA approved the updates
to the attainment inventory, the
maintenance demonstration, and the
budgets to the Clark County First
Maintenance Plan.18
On January 24, 2022, NDEP submitted
the Clark County Second Maintenance
Plan showing how the area will
continue to attain the 1997 8-hour ozone
national ambient air quality standard
(NAAQS) for 10 additional years beyond
the approval the State’s first 10-year
plan.
Lastly, on August 16, 2023, NDEP
submitted the Contingency Measure
Revision, which revised the contingency
measure section of the Clark County
Second Maintenance Plan. In this
action, we are proposing action on the
15 84
FR 33038 (July 11, 2019).
FR 44699.
17 According to ‘‘Emissions Inventory Guidance
for Implementation of Ozone and Particulate Matter
National Ambient Air Quality Standards (NAAQS)
and Regional Haze Regulations,’’ dated May 2017,
terminology used has changed from ‘‘summer day’’
emissions to ‘‘ozone season’’ emissions. However,
‘‘average summer day’’ emissions are used in this
instance to stay consistent between motor vehicle
emissions budgets of different ozone standards.
18 86 FR 59643.
16 84
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NDEP’s Clark County Second
Maintenance Plan submittal.
III. Second 10-Year Maintenance Plan
Submittal and Procedural
Requirements
CAA section 110(a)(1) and (2) and
section 110(1) require states to provide
reasonable notice and public hearing
prior to adoption of SIP revisions. In
this action, we are proposing action on
NDEP’s January 24, 2022, submittal of
the Clark County Ozone Second
Maintenance Plan, and NDEP’s August
16, 2023, submittal of the Contingency
Measure Revision as a revision to the
Nevada SIP, collectively referred to as
the Clark County Second Maintenance
Plan submittal.
Following a 30-day public comment
period, the Clark County Second
Maintenance Plan was adopted by the
Clark County Board of Commissioners,
submitted to NDEP, and submitted to
the EPA. Appendix B of the Clark
County Second Maintenance Plan
documents the public review process
followed by Clark County in adopting
the plan prior to transmittal to NDEP for
subsequent submittal to the EPA as a
revision to the Nevada SIP. The
documentation in 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 Clark County
Second Maintenance Plan was
published on October 14, 2021, on the
Clark County Department of
Environment and Sustainability (DES)
website, the DES official Facebook page,
and the DES official Twitter. No
comments were submitted.
On December 7, 2021, the Clark
County Board of Commissioners set a
public hearing for December 21, 2021, to
consider and approve the Clark County
Second Maintenance Plan. The
announcement of the public hearing
was subsequently published on the
County’s web page. On December 21,
2021, the Clark County Board of
Commissioners adopted the Clark
County Second Maintenance Plan at the
close of the public hearing. Following
adoption, Clark County DES forwarded
the plan to NDEP, the Governor of
Nevada’s designee for SIP matters, and
NDEP then submitted the plan as a
revision to the Nevada SIP to the EPA
for approval on January 24, 2022.
Appendix A of the Contingency
Measure Revision documents the board
approval process followed by Clark
County in adopting the plan prior to
transmittal to NDEP for subsequent
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submittal to the EPA as a revision to the
Nevada SIP. On July 18, 2023, the Clark
County Board of Commissioners put the
Contingency Measure Revision up for
public notice and adopted the
Contingency Measure Revision at the
close of the public hearing. Following
adoption, Clark County DES forwarded
the plan to NDEP and NDEP then
submitted the plan, as a revision to the
Nevada SIP, to the EPA for approval on
August 16, 2023.
Based on the documentation
contained in appendix B of the Plan and
appendix A of the Contingency Measure
Revision, we find that the Clark County
Second Maintenance Plan submittal
satisfies the procedural requirements of
section 110(l) of the Act.
IV. Requirements for Second 10-Year
Maintenance Plans
Section 175A of the CAA provides the
general framework for a maintenance
plan. The initial 10-year maintenance
plan must provide for maintenance of
the NAAQS for at least 10 years after
redesignation, including any additional
control measures necessary to ensure
such maintenance. In addition,
maintenance plans are to contain
contingency provisions necessary to
ensure the prompt correction of a
violation of the NAAQS that occurs after
redesignation. The contingency
measures must include, at a minimum,
a requirement that the state will
implement all control measures
contained in the nonattainment SIP
prior to redesignation. Beyond these
provisions, section 175A of the CAA
does not define the content of a second
10-year maintenance plan.
The primary guidance on
maintenance plans and redesignation
requests is a September 4, 1992,
memorandum from John Calcagni, titled
‘‘Procedures for Processing Requests to
Redesignate Areas to Attainment’’
(Calcagni Memo).19 The Calcagni Memo
outlines the key elements of a
maintenance plan, which include
verification of continued attainment,
monitoring network requirements,
attainment emissions inventory,
maintenance demonstration, and a
contingency plan. We evaluate the
Second 10-Year Maintenance Plan based
on the satisfactory fulfillment of these
and all relevant procedural
requirements of the CAA.
CAA section 175A(b) requires states
to submit an additional SIP revision
19 Memorandum dated September 4, 1992, from
John Calcagni, Director, EPA Air Quality
Management Division, to Regional Office Air
Division Directors, Subject: Procedures for
Processing Requests to Redesignate Areas to
Attainment.
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(Second 10-Year Maintenance Plan) to
maintain the NAAQS for an additional
10 years after the expiration of the 10year period covered by the initial
maintenance plan approved in
connection with the redesignation of the
area from nonattainment to attainment.
The revision is submitted eight years
after the original redesignation request
and maintenance plan have been
approved. The deadline to submit Clark
County’s Second Maintenance Plan was
January 8, 2021. On January 24, 2022,
NDEP submitted the Clark County
Second Maintenance Plan, to meet the
requirement for the subsequent
maintenance plan under CAA section
175A(b). The Clark County Second
Maintenance Plan is intended to
provide for continued maintenance of
the 1997 ozone NAAQS for the 10-year
period following the end of the first 10year period, i.e., from 2024 through
2033.
V. Evaluation of the Clark County
Second Maintenance Plan
Section 175A of the CAA sets forth
the elements of a maintenance plan. We
interpret this section of the Act to
require, in general, the following core
elements: attainment inventory,
maintenance demonstration, monitoring
network, verification of continued
attainment, and contingency plan.20
Under CAA section 175A, a
maintenance plan must demonstrate
continued attainment of the applicable
NAAQS for at least ten years after the
EPA approves a redesignation to
attainment. Eight years after
redesignation, the State must submit a
revised maintenance plan that
demonstrates continued attainment for
the subsequent ten-year period
following the initial ten-year
maintenance period. To address the
possibility of future NAAQS violations,
the maintenance plan must contain such
contingency provisions that the EPA
deems necessary to promptly correct
any violation of the NAAQS that occurs
after redesignation of the area. Based on
our review and evaluation of the plan,
as detailed below, we are proposing to
approve the Clark County Second
Maintenance Plan submittal because we
believe that it meets the requirements of
CAA section 175A.
A. Monitoring Network Requirements
Continued ambient monitoring of an
area is generally required over the
maintenance period. Clark County DES
currently operates ozone monitors at
thirteen sites within the Clark County 8hour ozone maintenance area.
20 Calcagni
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In the Clark County Second
Maintenance Plan,21 Clark County DES
indicates its intention to continue
operation of an air quality monitoring
network to verify continued attainment
of the 1997 8-hour ozone NAAQS.22 The
Clark County Second Maintenance Plan
also notes that Clark County DES’s State
and Local Air Monitoring Stations
(SLAMS) air quality monitoring network
(which includes ambient ozone
monitoring) will be reviewed annually
pursuant to 40 CFR 58.20(d) to
determine whether the system continues
to meet the applicable monitoring
objectives.23 We approved Clark
County’s SLAMS air quality network in
their Annual Monitoring Network Plan
for year 2020 on October 28, 2020, prior
to Clark County’s submittal of the Clark
County Second Maintenance Plan. We
find the County’s commitment for
continued ambient ozone monitoring as
set forth in the Clark County Second
Maintenance Plan to be acceptable.
B. Attainment Inventory
For maintenance plans, a state should
develop a comprehensive and accurate
inventory of actual emissions for an
attainment year which identifies the
level of emissions in the area which is
sufficient to maintain the NAAQS. The
inventory should be developed
consistent with the EPA’s most recent
guidance. For ozone, the inventory
should be based on typical ozone season
day emissions of NOX and VOC.
In the Clark County First Maintenance
Plan, Clark County DES used 2008 for
the attainment year inventory, because
2008 was one of the years in the 2007–
2009 three-year period when the area
first attained the 1997 ozone NAAQS.24
Clark County DES continued to monitor
attainment of the 1997 ozone NAAQS in
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2017. Therefore, the emissions
inventory from 2017 represents
emissions levels consistent with
continued attainment (i.e., maintenance)
of the NAAQS. Thus, Clark County DES
selected 2017 as the year for the
attainment inventory in the Clark
County Second Maintenance Plan. We
consider the selection of the 2017 base
year inventory to be appropriate given
that it was the most recent emissions
inventory associated with the reporting
schedule required under the Air
Emissions Reporting Requirements rule
at the time of Plan drafting.
Table 1 presents the VOC and NOX
emissions estimates contained in the
Clark County Second Maintenance Plan
for 2017 and presents the Plan’s
projected emissions inventories of
ozone precursors in an interim year
(2023) and the maintenance plan’s
horizon year (2033).25
TABLE 1—CLARK COUNTY 2017 AND PROJECTED 2023 AND 2033 VOC AND NOX EMISSIONS TOTAL DAILY EMISSIONS
[Tpd, average summer ozone season weekday]
2017
2023
2033
Emissions source
VOC
NOX
VOC
NOX
VOC
NOX
Point Source ............................................
Nonpoint Source ......................................
Mobile—On-road ......................................
Mobile—Nonroad .....................................
Airports .....................................................
Locomotives .............................................
Emission Reduction Bank ........................
Biogenic ...................................................
2.95
64.69
26.27
28.86
1.96
0.07
0.00
362.61
12.34
4.69
42.20
37.45
11.90
1.42
0.00
2.43
2.62
67.83
17.85
27.24
2.64
0.05
0.43
362.61
11.41
5.03
22.22
23.27
15.53
1.21
22.23
2.43
2.63
71.31
11.50
27.82
3.05
0.04
0.43
362.61
11.33
4.78
11.13
15.37
19.77
0.96
22.23
2.43
Total ..................................................
487.41
112.43
481.27
103.33
479.39
88.00
Source: Clark County Second Maintenance Plan, 17, Tables 2–4 and 2–5.
a Emissions associated with the proposed Department of Air Force (DAF) Training Project is included in Airport emissions projections for the
2023 and 2033 emissions projections for general conformity purposes. Emissions associated with the proposed Southern Nevada Supplemental
Airport and proposed Sloan Regional Heliport are included for the 2033 emissions projection for general conformity purposes.
The data shown in Table 1 in this
document is based on the 2017 National
Emissions Inventory (NEI).26 The
inventory addresses point sources,27
nonpoint sources,28 on-road mobile,
non-road mobile, airports, locomotives,
Emission Reduction Credits (ERCs),29
and biogenic 30 sources. Appendix A to
21 Clark
County Second Maintenance Plan, 20–23.
the Clark County Second
Maintenance Plan is not explicit in this regard, we
presume that Clark County DES’s intention to
continue operation of a monitoring network means
that the agency intends to do so consistent with the
EPA’s monitoring requirements in 40 CFR part 58
(‘‘Ambient Air Quality Surveillance’’).
23 The EPA’s requirements for annual review of
monitoring networks are no longer codified at 40
CFR 58.20(d) but are now found at 40 CFR 58.10.
24 76 FR 17343 (Apr. 29, 2011).
25 The emissions inventories reflect county-wide
emissions which include both the nonattainment
area portion of the county and the portion of the
county designated as ‘‘unclassifiable/attainment’’
for the 1997 8-hour ozone NAAQS. County-wide
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the Clark County Second Maintenance
Plan contains source-specific
descriptions of emissions calculation
procedures and sources of input data.
Point sources are stationary sources
that have a potential to emit (PTE)
greater than 100 tons per year of NOX
or VOC. Clark County DES adopted a
lower threshold by including all title V
stationary sources and minor sources
with a PTE greater than 10 tons of VOC
or 25 tons of NOX per year. Clark
County DES based the inventory
estimates on source reported actual
2017 emissions data but adjusted the
reported values to reflect a typical ozone
emissions are acceptable to characterize emissions
within the Clark County ozone nonattainment area
because over 95% of the population of the county
resides in the nonattainment area.
26 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.
27 The Clark County Second Maintenance Plan
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.
28 The Clark County Second Maintenance Plan
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.
29 The Clark County Second Maintenance Plan
uses the term, ‘‘ERCs’’ to refer to allowances earned
through voluntary pollutant emission reductions
such as equipment shutdowns or voluntarily
installed controls.
30 For the Clark County Second Maintenance
Plan, ‘‘biogenic sources’’ include agricultural crops;
lawn grass; forests that produce isoprene,
monoterpene, and other VOC emissions; and soils
that generate trace amounts of NOX.
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season day at each emissions unit
within the source facilities based on
information provided by the facilities.
Nonpoint sources include emissions
from equipment, operations and
activities that are numerous and in total
have significant emissions. Clark
County DES included emissions from
minor sources, residential combustion,
agricultural burning, industrial solvents
and graphic arts, and degreasing
operations. Clark County DES used
several methods to estimate area source
activity levels and emissions, including
applying local activity levels,
apportioning national or statewide
activity levels to the local level,
applying per capita emission factors
considering county-specific populations
and using specific method abstracts
detailed within the submittal.
Non-road emissions sources include
equipment that either move under their
own power or can be moved from site
to site.
The on-road emissions sector includes
emissions from engines used primarily
to propel equipment on highways and
other roads, including passenger
vehicles, motorcycles, and heavy-duty
diesel trucks. Clark County DES used
MOVES3, EPA’s MOVES3 emissions
factors, fleet data from Department of
Motor Vehicles (DMV) registration data,
Coordinated Research council (CRC)
vehicle speed data, the Regional
Transportation Commission (RTC) of
Southern Nevada’s transportation
demand modeling results, vehicle
classification data from the June 2018
Clark County Vehicle Classification
Study,31 and 2017 Highway
Performance Monitoring System
(HPMS) data from the Nevada
Department of Transportation (NDOT).
Biogenic emissions are from
vegetation and soil, and include crops,
lawn grass, and forests. Clark County
DES used the Biogenic Emissions
Inventory System version 3.61
(BEIS3.61) embedded in the SMOKE 4.7
model for the month of July to generate
average ozone season day emissions for
Clark County.
The airport sector includes emissions
from aircraft from commercial and
federal aviation sources. Clark County
DES relied on airport-specific emissions
inventory information provided by the
Clark County Department of Aviation
(CCDOA) for the five commercial
31 Clark County DES completed a vehicle
classification study in June 2018. The study used
2014–2016 traffic count data collected by the
Nevada Department of Transportation (NDOT).
Clark County DES incorporated VMT mix profiles
and temporal profiles, which DES incorporated into
the 2017 MOVES3 input database.
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airports located within the
nonattainment area.
Locomotives include emissions from
railroad and high-speed passenger train
emissions. Locomotive emissions were
estimated by Clark County DES based
on local activity data collected for the
Clark County First Maintenance Plan
and predicted emissions from highspeed passenger train service.
ERCs refer to allowances earned
through voluntary pollutant emissions
reductions such as equipment
shutdowns or voluntarily installed
controls. Clark County adopted New
Source Review (NSR) rule, Section
12.7.5—Emission Reduction credits into
the SIP,32 allowing Clark County to
adopt ERCs. In the Clark County First
Maintenance Plan, Clark County banked
NOX and VOC credits from the Clark
County Department of Air Quality and
Environmental Management (DAQEM)
ERC Bank,33 Reid Gardner ERCs,34 and
Mohave ERCs.35 In the Clark County
Second Maintenance Plan, Clark County
noted that ERCs have not changed from
the Clark County First Maintenance
Plan.
The EPA has reviewed the emissions
inventory submitted by Clark County
and proposes to conclude that the plan’s
inventory is based on reasonable
assumptions and methodologies, and
that the inventory is comprehensive,
current, accurate, and consistent with
applicable CAA provisions and the
Calcagni Memo. Therefore, we are
proposing that the inventory is
acceptable for use in demonstrating
maintenance of the 1997 ozone NAAQS.
C. Maintenance Demonstration
CAA section 175A(a) requires that the
maintenance plan ‘‘provide for the
maintenance of the national primary
ambient air quality standard for such air
pollutant in the area concerned for at
least 10 years after the redesignation.’’
Generally, a state may demonstrate
maintenance of the ozone NAAQS by
either showing that future emissions of
a pollutant or its precursors will not
exceed the level of the attainment
inventory or by modeling to show that
the future mix of sources and emissions
rates will not cause a violation of the
32 79
FR 62350 (October 17, 2014).
‘‘DAQEM ERC Bank’’ for a list of sources
contributing to the DAQEM ERC Bank in Clark
County.
34 NDEP banked Reid Gardner ERCs after the NV
Energy—Reid Gardner Station Power Plant, Unit #4
Steam Boiler was controlled with a low-NOX burner
in January 2010.
35 NDEP banked Mohave ERCs after the
permanent shut down and dismantling of the
Southern California Edison Mohave Generating
Station in November 2009.
33 See
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NAAQS.36 For areas that are required
under the Act to submit modeled
attainment demonstrations, the
maintenance demonstration should use
the same level of modeling.37 The Clark
County 8-hour ozone nonattainment
area was not required to submit a
modeled attainment demonstration, and
thus, the Clark County Second
Maintenance Plan may demonstrate
maintenance based on a comparison of
existing and future emissions of ozone
precursors.38
Clark County used the 2017 national
emissions inventory (NEI) data as the
baseline to develop growth factors for
point, nonpoint, and locomotive
sources. Clark County DES used the
EPA 2016 v.1 modeling platform
emissions data to develop per-year
growth adjustment factors for point,
nonpoint, federal aviation, and
locomotives. Clark County DES used
local activity data to develop
commercial airport growth factors and
conducted MOVES3 modeling to project
on-road and non-road emissions. The
derived growth adjustment factors were
used to extrapolate emissions to account
for a 16-year (2017 through 2033)
spread. The 2033 growth factors were
multiplied by the 2017 actual emissions
to produce the 2033 projected point
source and various other stationary
source emissions; including Residential
Wood Combustion,39 non-point VOC,40
airport,41 and locomotive emissions.42
An interim year (2023) projected
emissions inventory is also included.
On-road emissions were estimated for
the 2017 base year and for projection
years 2023 and 2033 and reflect a 32
percent decrease in VMT from 2017 to
2023 and a 56 percent decrease in VMT
from 2017 to 2033 based on Regional
Transit Commission (RTC)
projections.43
In addition to accounting for areawide
growth trends, Clark County DES added
emissions from specific projects that are
expected to become operational during
the second maintenance period,
36 Calcagni
Memo, 9–11.
37 Id.
38 A maintenance demonstration need not be
based on ozone modeling. See Wall v. EPA, 265
F.3d. 426 (6th Cir. 2001); Sierra Club v. EPA, 375
F.3d 537 (7th Cir. 2004). See also 66 FR 53094
(October 19, 2001), and 68 FR 25418 (May 12,
2003).
39 Clark County Second Maintenance Plan,
Appendix A, 23.
40 Clark County Second Maintenance Plan,
Appendix A, 24.
41 Clark County Second Maintenance Plan,
Appendix A, 29.
42 Clark County Second Maintenance Plan,
Appendix A, 31.
43 Clark County Second Maintenance Plan, 27,
Table 6–1.
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including the proposed Southern
Nevada Supplemental Airport, the
proposed Sloan Regional Heliport, and
DAF training program in the future-year
emissions inventories, and also added
in ERCs from certain stationary sources
in the event that the ERCs are used for
the purposes of issuing permits for new
or modified stationary sources in the air
quality planning area. We have
reviewed the methods and assumptions,
as described in connection with the
attainment inventory, that Clark County
DES used to project emissions to 2023
and 2033 for the various source
categories and find them to be
reasonable.
Table 1 compares the VOC and NOX
emissions estimated for the Clark
County 8-hour ozone maintenance area
for 2017 with those for 2023 and 2033
by source category. The projected VOC
and NOX emissions show that VOC and
NOX emissions would remain well
below the attainment levels throughout
the second 10-year maintenance period
and thereby adequately demonstrate
maintenance through that period.
In addition, historical monitoring data
presented in the plan shows a gradual
downward trend in ozone design values
during 2008–2020. The 1997 NAAQS
level of 80 ppb was achieved in 2009,
and the 2020 value of 74 ppb is well
below the NAAQS.44 This supports the
maintenance demonstration, and the
EPA expects this downward trend will
continue given the projected emissions
decreases.
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D. Verification of Continued Attainment
NDEP and the Clark County Board of
County Commissioners have the legal
authority to implement and enforce the
requirements of the Clark County
Second Maintenance Plan. This
includes the authority to adopt,
implement and enforce any emissions
control contingency measures
determined to be necessary to correct
ozone NAAQS violations. To verify
continued attainment, Clark County
DES commits in the Clark County
Second Maintenance Plan to the
continued operation of an ozone
monitoring network that meets the EPA
ambient air quality surveillance
requirements.
Secondly, the transportation
conformity process represents another
means by which to verify continued
attainment of the 1997 8-hour ozone
NAAQS in the Clark County 8-hour
ozone area given the relative importance
of motor vehicle emissions to the overall
emissions inventories of ozone
precursors.45
Lastly, while not cited in the plan,
NDEP and Clark County DES must
inventory emissions sources and report
to the EPA on a periodic basis under 40
CFR part 51, subpart A (‘‘Air Emissions
Reporting Requirements’’). These
emissions inventory updates will
provide a third means with which to
track emissions in the area relative to
those projected in the maintenance plan
and thereby verify continued attainment
of the NAAQS. These methods are
sufficient for the purpose of verifying
continued attainment.
E. Contingency Provisions
Section 175A(d) of the Act requires
that maintenance plans include
contingency provisions, as the EPA
deems necessary, to promptly correct
any violations of the NAAQS that occur
after redesignation of the area. Such
provisions must include a requirement
that the State will implement all
measures with respect to the control of
the air pollutant concerned which were
contained in the SIP for the area before
redesignation of the area as an
attainment area.
Under section 175A(d), contingency
measures identified in the contingency
plan do not have to be fully adopted at
the time of redesignation. However, the
contingency plan is an enforceable part
of the SIP and should ensure that the
contingency measures are adopted
expeditiously once they are triggered by
a specified event. The maintenance plan
should clearly identify the measures to
be adopted, a schedule and procedure
for adoption and implementation, and a
specific timeline for action by the State.
As a necessary part of the plan, the State
should also identify specific indicators
or triggers, which will be used to
determine when the contingency
measures need to be implemented.
As required by section 175A of the
CAA, Clark County DES has adopted a
contingency plan to address possible
future ozone air quality problems.46
Clark County DES identifies the trigger
date as 60 days after a determination of
a confirmed violation of the 1997 8-hour
ozone NAAQS. Within 45 days of the
trigger date, Clark County will notify the
EPA that it is evaluating potential
contingency measures. Within 90 days
of the trigger date, Clark County will
send a report to the EPA and then will
initiate a public process to consider the
recommended contingency measures,
45 Clark
County Second Maintenance Plan, Page
15.
44 Clark
County Second Maintenance Plan, 12,
Figure 2–1.
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46 Contingency Measure Revision, Section 2,
‘‘Contingency Measures Plan.’’
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including soliciting stakeholder
involvement and holding public
hearings. The necessary emissions
control measures will be adopted and
implemented no later than 18 months
after the trigger date.
Potential contingency measures listed
in the maintenance plan are those
emissions controls or other measures
that Clark County, the Nevada State
Board of Agriculture, and/or the Nevada
State Environmental Commission may
choose to adopt and implement in
response to the contingency trigger. The
contingency measures plan in the
Contingency Measure Revision lists the
following potential contingency
measures that will be considered for
adoption and implementation by the
applicable State or County agency, but
the Plan indicates that the list is not to
be considered exclusive:
• Reid vapor pressure reduction (i.e.,
in gasoline sold during the summer
ozone season; would need to be adopted
and implemented by the Nevada State
Board of Agriculture);
• Inspection/maintenance program
changes and additions (e.g., lowering
the cut points for VOCs and NOX
applicable to pre-1996 vehicles; would
need to be adopted and implemented by
the State Environmental Commission
and/or the State Department of Motor
Vehicles);
• Consumer and commercial products
(Clark County would be responsible for
adoption and implementation);
• Architectural surface coatings
(Clark County would be responsible for
adoption and implementation);
• Lawn and garden equipment use
(Clark County would be responsible for
adoption and implementation); and
• Establish/enhance trip reduction
programs (Clark County and the RTC
would be responsible for adoption and
implementation).
Upon our review of the plan, we find
that the contingency provisions of the
Contingency Measure Revision clearly
identify specific contingency measures,
contain tracking and triggering
mechanisms to determine when
contingency measures are needed,
contain a description of the process of
recommending and implementing
contingency measures, and contain
specific timelines for action. Thus, we
conclude that the contingency
provisions of the Contingency Measure
Revision are adequate to ensure prompt
correction of a violation and therefore
comply with section 175A(d) of the Act.
F. Motor Vehicle Emissions Budgets for
Transportation Conformity
Section 176(c) of the CAA requires
federal actions in nonattainment and
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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, RTCs in nonattainment and
maintenance areas coordinate with state
and local air quality and transportation
agencies, the EPA, FHWA, and FTA to
demonstrate that an area’s regional
transportation plans and transportation
improvement programs conform to the
applicable SIP. This demonstration is
typically done by showing that
estimated emissions from existing and
planned highway and transit systems
are less than or equal to the motor
vehicle emissions budgets (‘‘budgets’’)
contained in submitted or approved
control strategy SIPs and maintenance
plans.47
These control strategy SIPs and
maintenance plans typically set budgets
for criteria pollutants and/or their
precursors to address pollution from
cars and trucks. Budgets are generally
established for specific years and
specific pollutants or precursors.
Maintenance plan submittals should
identify budgets for transportationrelated VOC and NOX emissions in the
last year of the maintenance period.
For budgets in a maintenance plan to
be approvable, they must meet, at a
minimum, the EPA’s adequacy
criteria.48 To meet these requirements,
the budgets must be consistent, when
considered with emissions from all
other sources, with maintenance of the
NAAQS and reflect all the motor vehicle
control measures relied upon for the
maintenance demonstration. 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 MVEB
during a public comment period; and (3)
making a finding of adequacy. The
process for determining the adequacy of
a submitted budget is codified at 40 CFR
93.118(f). The EPA can notify the public
by either posting an announcement that
the EPA has received SIP budgets on the
EPA’s adequacy website, or via a
Federal Register notice of proposed
rulemaking when the EPA reviews the
adequacy of a maintenance plan budget
simultaneously with its review and
action on the SIP submittal itself.49
Clark County’s Second Maintenance
Plan contains VOC and NOX budgets for
2017, 2023 and 2033. Any and all
comments on the approvability of the
budgets should be submitted during the
comment period stated in the DATES
section of this document.
The EPA proposes to approve 2017,
2023, and 2033 budgets in the Clark
County Second Maintenance Plan for
transportation conformity purposes in
the final rulemaking on Clark County’s
ozone redesignation request. If the EPA
approves the budgets in the final
rulemaking action, the new budgets
must be used in future transportation
conformity determinations for Clark
County for the 2015 ozone standard.
The new budgets, if approved in the
final rulemaking, will be effective on the
date of the EPA’s final rulemaking in the
Federal Register. The applicable VOC
and NOX MVEBs for the Clark County
ozone nonattainment area are defined in
table 2.
TABLE 2—PROPOSED MOTOR VEHICLE EMISSIONS BUDGETS (MVEBS) FOR CLARK COUNTY
VOC
(tpd, average summer weekday)
Budget year
2017 .........................................................................................................
2023 .........................................................................................................
2033 .........................................................................................................
NOX
(tpd, average summer weekday)
26.27
20.92
15.51
42.2
26.77
23.35
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From Table 6–3 and 6–4 of the Clark County Second Maintenance Plan.
The MVEBs are the on-road mobile
source VOC and NOX emissions for
Clark County for 2017, 2023 and 2033.
The budgets are compatible with the
2017, 2023, and 2033 on-road mobile
source VOC and NOX emissions
included in Clark County’s 2017, 2023,
and 2033 VOC and NOX emission
inventories, as summarized in Table 2.
The derivation of the budgets is
thoroughly discussed in Appendix A,
Chapter 2 of Clark County’s Second
Maintenance Plan. While the Plan
includes budgets for 2017, we are not
evaluating the 2017 budgets because
that year would not be used in any
future conformity determination
because the plan contains budgets for
2023 and because 2017 budgets are not
required for the submitted second
maintenance plan.
We evaluated the budgets against our
adequacy criteria in 40 CFR 93.118(e)(4)
and (5) as part of our review of the
budget’s approvability and expect to
complete the adequacy review of the
budgets concurrent with our final action
on the Clark County’s Second
Maintenance Plan. The EPA is not
required under its transportation
conformity rule to find budgets
adequate prior to proposing approval of
them. In this notice, the EPA is
announcing that the adequacy process
for these budgets begins, and the public
has 30 days to comment on their
adequacy, per the transportation
conformity rule at 40 CFR 93.118(f)(2)(i)
and (ii).
Clark County DES developed the
budgets for 2023 and 2033 using onroad motor vehicle emission estimates
made using the EPA’s MOVES3 model,
fleet data from DMV registration data,
CRC vehicle speed data, NDOT HPMS
data, travel demand modeling from the
Regional Transportation Commission
and vehicle classification data from the
June 2018 Clark County On-road
Vehicle Classification Study.
As documented in the separate
memorandum 50 included in the docket
for this rulemaking, we preliminarily
conclude that the budgets in the Second
Maintenance Plan meet each adequacy
criterion. While adequacy and approval
47 Control strategy SIPs refer to RFP and
attainment demonstration SIPs. 40 CFR 93.101.
48 40 CFR 93.118(e)(4) and (5). For more
information on the transportation conformity
requirement and applicable policies on MVEBs,
please visit our transportation conformity website
at: https://www.epa.gov/otaq/stateresources/
transconf/index.htm.
49 40 CFR 93.118(f)(2).
50 See the EPA Memorandum dated August 22,
2023 titled: Adequacy Documentation for Motor
Vehicle Emissions Budgets in Clark County Second
Maintenance Plan.’’
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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 and are
proposing to approve the demonstration
of maintenance for the 1997 ozone
maintenance area through the year 2033.
We have also reviewed the budgets in
Clark County’s Second Maintenance
Plan and found that they are consistent
with the maintenance demonstration for
which we are proposing approval, are
clearly identified and precisely
quantified, 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 93.118(e)(4)
and (5). The EPA is proposing to
approve the budgets for 2023 and 2033
as part of our approval of Clark County’s
Second Maintenance Plan. At the point
when we either finalize the adequacy
process or approve the budgets as
proposed (whichever occurs first; note
that they could also occur concurrently
per 40 CFR 93.118(f)(2)(iii)), the budgets
must be used by the Regional
Transportation Commission (i.e., the
Metropolitan Planning Organization
(MPO) for this area) for transportation
conformity determinations for the Clark
County 2015 ozone nonattainment area.
VI. Environmental Justice
Considerations
The EPA performed a screening-level
analysis using the EPA’s environmental
justice (EJ) screening and mapping tool
(‘‘EJSCREEN’’). Our screening-level
analysis included multiple
environmental and demographic
indicators, including the EJSCREEN
‘‘Demographic Index,’’ which is the
average of an area’s percentage of
minority and low-income populations.
The Demographic Index of Clark County
is at the 68th percentile, compared to
the United States as a whole.51 The
results of this analysis are being
provided for informational and
transparency purposes.
This action addresses a plan for
continued maintenance of the 1997
ozone NAAQS for Clark County.
Approval of this plan does not impose
any additional regulatory requirements
on sources beyond those imposed by
state law. As discussed in this
document, Nevada has demonstrated
that the Clark County is attaining the
1997 ozone NAAQS and the Clark
County Second Maintenance Plan
provides for the maintenance of the
51 Clark County Ozone NAA EJSCREEN Report
dated February 10, 2023.
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NAAQS for the reminder of the
maintenance period. We expect that this
action will generally be neutral or
contribute to reduced environmental
and health impacts on all populations in
Clark County, including people of color
and low-income populations. At a
minimum, this action would not worsen
any existing air quality and is expected
to ensure the area is meeting
requirements to maintain air quality
standards. Further, there is no
information in the record indicating that
this action is expected to have
disproportionately high or adverse
human health or environmental effects
on a particular group of people.
VII. Proposed Action and Request for
Public Comment
Under CAA section 110(k)(3), and for
the reasons set forth in this document,
the EPA is proposing to approve the
Clark County Second Maintenance Plan
submitted by NDEP on January 24, 2022,
as a revision to the Nevada SIP.52 We
are proposing to approve the
maintenance demonstration and
contingency provisions as meeting all
applicable requirements for
maintenance plans and related
contingency provisions in CAA section
175A, and the budgets for 2023 and
2033 (shown in Table 2) for
transportation conformity purposes as
we find they meet all applicable criteria
for such budgets including the adequacy
criteria under 40 CFR 93.118(e).
We are soliciting comments on these
proposed actions. We will accept
comments from the public for 30 days
following publication of this proposal in
the Federal Register and will consider
any relevant comments before taking
final action.
VIII. Statutory and Executive Order
Reviews
Under the Clean Air Act, the
Administrator is required to approve a
SIP submission that complies with the
provisions of the Act and applicable
federal regulations. 42 U.S.C. 7410(k);
40 CFR 52.02(a). Thus, in reviewing SIP
submissions, the EPA’s role is to
approve state choices, provided that
they meet the criteria of the Clean Air
Act. Accordingly, this proposed action
merely proposes to approve state law as
meeting federal requirements and does
not impose additional requirements
beyond those imposed by state law. For
that reason, this proposed action:
• Is not a ‘‘significant regulatory
action’’ subject to review by the Office
of Management and Budget under
52 Clark County Second Maintenance Plan
(submitted electronically January 24, 2022).
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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 (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
• Will not have disproportionately
high and adverse human health or
environmental effects on minority
populations, low-income populations
and/or indigenous peoples, as specified
in Executive Order 12898 (59 FR 7629,
February 16, 1994), as discussed in
section VI of this proposal.
In addition, there are no areas of
Indian country within the planning
area, and the state plan for which the
EPA is proposing approval does not
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 Clark County
Second Maintenance Plan does not
apply, and therefore, this proposed
action does not have tribal implications
and would not, if approved, 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, Nitrogen dioxide, Particulate
matter, Sulfur dioxide, Reporting and
recordkeeping requirements, Volatile
organic compounds.
Authority: 42 U.S.C. 7401 et seq.
E:\FR\FM\21DEP1.SGM
21DEP1
88308
Federal Register / Vol. 88, No. 244 / Thursday, December 21, 2023 / Proposed Rules
Dated: December 14, 2023.
Martha Guzman Aceves,
Regional Administrator, Region IX.
https://www.epa.gov/dockets/
commenting-epa-dockets.
FOR FURTHER INFORMATION CONTACT:
[FR Doc. 2023–27874 Filed 12–20–23; 8:45 am]
BILLING CODE 6560–50–P
ENVIRONMENTAL PROTECTION
AGENCY
40 CFR Part 52
[EPA–R04–OAR–2023–0232; FRL–11600–
01–R4]
Air Plan Approval; GA; Miscellaneous
Rule Revision
Environmental Protection
Agency (EPA).
ACTION: Proposed rule.
AGENCY:
The Environmental Protection
Agency (EPA) is proposing to approve a
State Implementation Plan (SIP)
revision submitted by the State of
Georgia, through the Georgia
Environmental Protection Division
(EPD) via a letter dated October 20,
2022. The revision seeks to change
Georgia’s Rules for Air Quality Control
in the SIP by removing the 1971 annual
and 24-hour ambient air quality primary
standard for sulfur dioxide (SO2), which
no longer applied in Georgia as of April
30, 2022. EPA is proposing to approve
this SIP revision because the State has
demonstrated that this change is
consistent with the Clean Air Act (CAA
or Act).
DATES: Comments must be received on
or before January 22, 2024.
ADDRESSES: Submit your comments,
identified by Docket ID No. at EPA–
R04–OAR–2023–0232 at https://
www.regulations.gov. Follow the online
instructions for submitting comments.
Once submitted, comments cannot be
edited or removed from Regulations.gov.
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. 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, the full
EPA public comment policy,
information about CBI or multimedia
submissions, and general guidance on
making effective comments, please visit
khammond on DSKJM1Z7X2PROD with PROPOSALS
SUMMARY:
VerDate Sep<11>2014
16:23 Dec 20, 2023
Jkt 262001
Josue Ortiz Borrero, Air Regulatory
Management Section, Air Planning and
Implementation Branch, Air and
Radiation Division, U.S. Environmental
Protection Agency, Region 4, 61 Forsyth
Street SW, Atlanta, Georgia 30303–8960.
The telephone number is (404) 562–
8085. Mr. Ortiz Borrero can also be
reached via electronic mail at
ortizborrero.josue@epa.gov.
SUPPLEMENTARY INFORMATION:
I. Background
On June 2, 2010, EPA revised the
primary SO2 national ambient air
quality standards (NAAQS or standards)
to provide requisite protection of public
health with an adequate margin of
safety. See 75 FR 35520 (June 22, 2010).
Specifically, EPA established a new 1hour SO2 standard at a level of 75 parts
per billion (ppb), codified at 40 CFR
50.17.1 2 The 1-hour standard is met at
an ambient air quality monitoring site
when the 3-year average of the annual
99th percentile of daily maximum 1hour average concentrations is less than
or equal to 75 ppb, as determined in
accordance with Appendix T of 40 CFR
part 50 and 40 CFR 50.17(a) and (b).3
EPA set this new 1-hour short-term
standard to replace the 1971 primary 24hour standard of 0.14 parts per million
(ppm) and the annual SO2 standard set
of 0.03 ppm.4 5 In the 2010 SO2 NAAQS
final rulemaking, the Administrator
concluded it was appropriate to revoke
the 24-hour and annual primary
standards,6 stating ‘‘a 1-hour standard at
[a] level of 75 ppb would have the effect
of maintaining 24-hour and annual SO2
1 See 75 FR 35520 and https://www.gpo.gov/
fdsys/pkg/FR-2010-06-22/pdf/2010-13947.pdf.
2 See also NAAQS Table at https://www.epa.gov/
criteria-air-pollutants/naaqs-table.
3 On February 25, 2019, EPA finalized a second
review of the SO2 standard, retaining the existing
primary 1-hour SO2 NAAQS based on a review of
the full body of currently available scientific
evidence and exposure/risk information at the time.
See 84 FR 9866 and https://www.epa.gov/so2pollution/primary-national-ambient-air-qualitystandard-naaqs-sulfur-dioxide.
4 EPA promulgated the 1971 primary and
secondary NAAQS for SO2 on April 30, 1971. See
36 FR 8186. The 1971 primary SO2 standards of 365
mg/m3 (0.14 ppm), averaged over a period of 24
hours and not to be exceeded more than once per
year, and 80 mg/m3 (0.03 ppm), as an annual
arithmetic mean.
5 EPA did not revise the secondary 3-hour SO
2
NAAQS set at 0.5 ppm in the 2010 or 2019 NAAQS
review.
6 EPA arrived at the same conclusion in the 2019
review of the SO2 standard when the agency
retained the 1-hour SO2 standard of 75 ppb stating
(respecting the rationale to revoke the previous SO2
standard) ‘‘the evidence in this review [2019] is not
substantively changed from that in the last review
[2010].’’ See 84 FR 9866 (March 18, 2019).
PO 00000
Frm 00038
Fmt 4702
Sfmt 4702
concentrations generally well below the
levels of the current 24-hour and annual
NAAQS.’’ See 75 FR at 35550. The final
rule also states, based on health
evidence and risk-based information,
that the 1971 SO2 standards ‘‘ ‘are not
adequate to protect public health,
especially in relation to short-term
exposures to SO2 (5–10 minutes) by
exercising asthmatics’ ’’ and that the
new 1-hour standard would provide
requisite protection of public health
with an adequate margin of safety. See
75 FR at 35530, 35550.
Anti-Backsliding
When EPA revised the SO2 NAAQS in
2010, replacing the annual and 24-hour
standards with a short term 1-hour
standard, EPA also addressed the
section 172(e) anti-backsliding
provision of the CAA and determined
what provisions are appropriate to
provide for transition to the new
standard. Section 172(e) of the CAA
specifies that if EPA relaxes a NAAQS,
control obligations no less stringent
than those that apply in nonattainment
area SIPs may not be relaxed, and
adopting those controls that have not
yet been adopted as needed may not be
avoided. Even though the 2010 1-hour
standard is more protective than the
previous SO2 NAAQS, anti-backsliding
provisions were necessary to insure that
the health protection provided by the
prior NAAQS continues to be achieved
as well as maintained as states
transition to the new standard.7
Specifically, EPA established at 40 CFR
50.4(e) when the 1971 SO2 NAAQS
would be revoked in areas, and when it
was necessary to retain the older SO2
standards, setting conditions needed for
the eventual transition to the new 1hour SO2 NAAQS. Specifically, 40 CFR
50.4(e) provides that the 1971 SO2
NAAQS will no longer apply to an area
one year after the effective date of the
designation of that area for the 2010 SO2
NAAQS set forth in § 50.17; except that
the 1971 SO2 NAAQS remains in effect
for areas that are nonattainment for that
NAAQS as of the effective date of the
2010 SO2 NAAQS, and areas not
meeting the requirements of a SIP call
with respect to requirements for the
1971 SO2 NAAQS until that area
submits, and EPA approves, an
7 The owner or operator of a new or modified
source will still be required to demonstrate
compliance with the annual and 24-hour SO2
increments, even when their counterpart NAAQS
are revoked. The annual and 24-hour increments
are established in the CAA and will need to remain
in the prevention of significant deterioration
regulations because EPA does not interpret the CAA
to authorize EPA to remove them. See 75 FR at
35578.
E:\FR\FM\21DEP1.SGM
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]]>Agencies
[Federal Register Volume 88, Number 244 (Thursday, December 21, 2023)]
[Proposed Rules]
[Pages 88300-88308]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2023-27874]
=======================================================================
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ENVIRONMENTAL PROTECTION AGENCY
40 CFR Part 52
[EPA-R09-OAR-2022-0955; FRL-10549-01-R9]
Approval of Implementation Plans for Air Quality Planning
Purposes; State of Nevada; Clark County Second 10-Year Maintenance Plan
for the 1997 8-Hour Ozone Standard
AGENCY: Environmental Protection Agency (EPA).
ACTION: Proposed rule.
-----------------------------------------------------------------------
SUMMARY: The Environmental Protection Agency (EPA) is proposing to
approve, as a revision of the Nevada state implementation plan (SIP),
the State's second 10-year plan for maintaining the 1997 8-hour ozone
standard in Clark County (``Clark County Second Maintenance Plan'' or
``Plan''). The Clark County Second Maintenance Plan includes, among
other elements, a base year emissions inventory, a maintenance
demonstration, contingency provisions, and motor vehicle emissions
budgets for use in transportation conformity determinations to ensure
the continued maintenance of the 1997 National Ambient Air Quality
Standards for ozone (``1997 ozone NAAQS'' or ``1997 8-hour ozone
standard''). With this proposed rulemaking, the EPA is initiating the
adequacy process for the 2017, 2023, and 2033 motor vehicle emissions
budgets. The EPA is proposing these actions because the SIP revision
meets the applicable statutory and regulatory requirements for such
plans and motor vehicle emissions budgets.
DATES: Comments must be received on or before January 22, 2024.
ADDRESSES: Submit your comments, identified by Docket ID No. EPA-R09-
OAR-2022-0955, 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 a disability
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: Andrew Ledezma, EPA Region IX, 75
Hawthorne St., San Francisco, CA 94105. By phone: (415) 972-3985 or by
email at [email protected].
SUPPLEMENTARY INFORMATION: Throughout this document, ``we,'' ``us,''
and ``our'' refer to the EPA.
Table of Contents
I. Summary of Proposed Action
II. Background
III. Second 10-Year Maintenance Plan Submittal and Procedural
Requirements
IV. Requirements for Second 10-Year Maintenance Plans
V. Evaluation of the Clark County Second Maintenance Plan
A. Monitoring Network Requirements
B. Attainment Inventory
C. Maintenance Demonstration
D. Verification of Continued Attainment
E. Contingency Provisions
F. Motor Vehicle Emissions Budgets for Transportation Conformity
VI. Environmental Justice Considerations
VII. Proposed Action and Request for Public Comment
VIII. Statutory and Executive Order Reviews
I. Summary of Proposed Action
Under Clean Air Act (CAA or ``the Act'') section 110(k)(3), the EPA
is proposing to approve two submittals from the Nevada Division of
Environmental Protection (NDEP) as a revision to the Nevada SIP: the
Clark County Second Maintenance Plan dated December 21, 2021, and a
supplement to the Clark County Second Maintenance Plan (``Contingency
Measure Revision'') dated August 16, 2023. In this action, we refer to
the Clark County Second Maintenance Plan and the Contingency Measure
Revision collectively as the ``Clark County Second Maintenance Plan
submittal.''
The EPA is proposing to find that the maintenance demonstration,
showing how the area will continue to attain the 1997 8-hour ozone
NAAQS for 10 additional years beyond the approval the State's first 10-
year plan for maintaining the 1997 8-hour ozone standard in Clark
County (``Clark County First Maintenance Plan'' or ``first maintenance
plan'') (i.e., through 2033), and the contingency provisions,
describing the actions that Clark County will take in the event of a
future monitored violation, meet all applicable requirements for
maintenance plans and related contingency provisions in CAA section
175A. The EPA is also proposing to approve the motor vehicle emissions
budgets (MVEBs or ``budgets'') in the Clark County Second Maintenance
Plan because we find they meet the applicable transportation conformity
requirements under 40 CFR 93.118(e).
II. Background
Sections 108 and 109 of the CAA govern the establishment, review,
and revision, as appropriate, of the NAAQS to protect public health and
welfare. The CAA requires the EPA to periodically review the air
quality criteria, the science upon which the standards are based, and
the standards themselves. Ground-level ozone is one of the criteria
pollutants regulated under the NAAQS.
Ground-level ozone is generally not emitted directly by sources.
Rather, directly emitted oxides of nitrogen (NOX) and
volatile organic compounds (VOC) react in the presence of sunlight to
form ground-level ozone, as a secondary pollutant, along with other
secondary compounds. NOX and VOC are ``ozone precursors.''
Reduction of peak ground-level ozone concentrations is typically
achieved through controlling VOC and NOX emissions.
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.\1\
---------------------------------------------------------------------------
\1\ ``Fact Sheet--2008 Final Revisions to the National Ambient
Air Quality Standards for Ozone,'' dated March 2008.
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[[Page 88301]]
In 1997, the EPA revised the NAAQS for ozone, setting it at 0.08
parts per million (ppm) averaged over an 8-hour time frame.\2\ The EPA
set the 1997 8- hour ozone standard based on scientific evidence
demonstrating that ozone causes adverse health effects at lower ozone
concentrations and over longer periods of time, than was understood
when the pre-existing 1-hour ozone standard was set. The EPA determined
that the 1997 8-hour ozone NAAQS would be more protective of human
health, especially for children and adults who are active outdoors, and
individuals with a pre-existing respiratory disease, such as asthma.\3\
---------------------------------------------------------------------------
\2\ 62 FR 38856 (July 18, 1997).
\3\ On March 27, 2008 (73 FR 16436), the EPA promulgated a
revised 8-hour ozone standard of 0.075 ppm (the 2008 8-hour ozone
standard), and on May 21, 2012, the EPA designated the entire state
of Nevada unclassifiable/attainment for the 2008 8-hour ozone
standard (77 FR 30088). This rulemaking relates only to the 1997 8-
hour ozone standard and does not relate to the 2008 8-hour ozone
standard.
---------------------------------------------------------------------------
In 2004, the EPA designated areas of the country with respect to
the 1997 8-hour ozone NAAQS.\4\ Under the EPA's ``Phase 1''
implementation rule for the 1997 8-hour ozone standard \5\ an area was
classified under subpart 2 based on its 8-hour ozone design value
(i.e., the 3-year average annual fourth-highest daily maximum 8-hour
average ozone concentration at the worst-case monitoring site in the
area or in its immediate downwind environs), if it had a 1-hour ozone
design value \6\ at the time of designation at or above 0.121 ppm. All
other areas were covered under subpart 1 based on their 8-hour ozone
design values.\7\ Clark County was designated as a subpart 1 ozone
nonattainment area by the EPA on April 30, 2004, based on air quality
monitoring data from 2001-2003. The designation became effective on
June 15, 2004. On September 17, 2004, the EPA reduced the geographic
extent of the ozone nonattainment area to encompass a portion, but not
all, of Clark County.\8\
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\4\ 69 FR 23858 (April 30, 2004).
\5\ 69 FR 23951, (April 30, 2004).
\6\ The design value for the 1-hour ozone standard is the
fourth-highest daily maximum 1-hour ozone concentration over a
three-year period at the worst-case monitoring site in the area.
\7\ 69 FR 23951. The design value for the 8-hour standard is the
three-year average of the annual fourth-highest daily maximum 8-hour
ozone concentration at the worst-case monitoring site in the area.
\8\ 69 FR 55956 (September 17, 2004), 70 FR 71612 (November 29,
2005), and 40 CFR 81.329. The boundaries of the Clark County ozone
nonattainment area are defined in 40 CFR 81.329. Specifically, the
area is defined as: ``That portion of Clark County that lies in
hydrographic areas 164A, 164B, 165, 166, 167, 212, 213, 214, 216,
217, and 218 but excluding the Moapa River Indian Reservation and
the Fort Mojave Indian Reservation.'' The area 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.
---------------------------------------------------------------------------
In South Coast Air Quality Management Dist. v. EPA \9\ the U.S.
Court of Appeals for the District of Columbia Circuit (D.C. Circuit, or
``Court'') vacated the EPA's Phase 1 implementation rule for the 1997
8-hour ozone standard.\10\ In response to several petitions for
rehearing, the D.C. Circuit clarified that the Phase 1 rule was vacated
only for those parts of the rule that had been successfully
challenged.\11\ The decision left intact the Court's rejection of the
EPA's reasons for implementing the 8-hour ozone standard in certain
nonattainment areas under subpart 1 in lieu of subpart 2 of the CAA.
---------------------------------------------------------------------------
\9\ 472 F.3d 882 (D.C. Cir. 2007).
\10\ 69 FR 23951.
\11\ 472 F.3d 882 (D.C. Cir. 2007).
---------------------------------------------------------------------------
On May 14, 2012, in response to the Court's vacatur of the
provision of the Phase 1 rule for the 1997 8-hour ozone standard that
placed certain nonattainment areas, including Clark County solely under
subpart 1, the EPA classified Clark County as a marginal ozone
nonattainment area under subpart 2 of the CAA.\12\
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\12\ 77 FR 28424.
---------------------------------------------------------------------------
On March 29, 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
8-hour ozone NAAQS for the 2007-2009 monitoring period.\13\
---------------------------------------------------------------------------
\13\ 76 FR 17343.
---------------------------------------------------------------------------
On April 11, 2011, NDEP submitted the Clark County First
Maintenance Plan and requested that the EPA redesignate the Clark
County 8-hour ozone nonattainment area to attainment for the 1997 8-
hour ozone standard. On January 8, 2013, the EPA approved the Clark
County First Maintenance Plan, and redesignated the area from
nonattainment to attainment of the 1997 8-hour ozone NAAQS.\14\
---------------------------------------------------------------------------
\14\ 78 FR 1149.
---------------------------------------------------------------------------
On October 31, 2018, NDEP submitted a Revision to Motor Vehicle
Emissions Budgets in Ozone Redesignation Request and Maintenance Plan
(``2018 Ozone Maintenance Plan Revision''). The 2018 Ozone Maintenance
Plan Revision updated elements of the Clark County First Maintenance
Plan, including the attainment inventory, the maintenance
demonstration, and the budgets. The 2018 Ozone Maintenance Plan
Revision established ozone season budgets of 52.96 and 86.74 tons per
day (tpd) for VOC and NOX, respectively, for 2022 so that
the area would have updated budgets available to use for transportation
conformity determinations with respect to the 2015 National Ambient Air
Quality Standards for ozone (``2015 ozone NAAQS'').\15\ On August 27,
2019, the EPA conditionally approved the 2018 Ozone Maintenance Plan
revisions, based on commitments to submit an additional SIP revision to
reduce the safety margin allocations for the budgets within one year of
the final conditional approval.\16\
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\15\ 84 FR 33038 (July 11, 2019).
\16\ 84 FR 44699.
---------------------------------------------------------------------------
On September 30, 2020, NDEP submitted an additional Revision to
Motor Vehicle Emissions Budgets for the 1997 ozone NAAQS, Clark County,
Nevada (``2020 Ozone Maintenance Plan Revision''). The 2020 Ozone
Maintenance Plan Revision was prepared in response to the EPA's
conditional approval of the 2018 Ozone Maintenance Plan Revision. The
2020 Ozone Maintenance Plan Revision revised certain budgets from the
2018 Ozone Maintenance Plan Revision to prevent interference with
Reasonable Further Progress (RFP) or attainment of the 2008 and 2015
ozone NAAQS. The 2020 Ozone Maintenance Plan Revision established
budgets of 23.92 and 32.16 tons per average summer day \17\ for VOC and
NOX, respectively, for 2022. On October 28, 2021, with the
submittal of the 2020 Ozone Maintenance Plan Revision, the EPA approved
the updates to the attainment inventory, the maintenance demonstration,
and the budgets to the Clark County First Maintenance Plan.\18\
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\17\ According to ``Emissions Inventory Guidance for
Implementation of Ozone and Particulate Matter National Ambient Air
Quality Standards (NAAQS) and Regional Haze Regulations,'' dated May
2017, terminology used has changed from ``summer day'' emissions to
``ozone season'' emissions. However, ``average summer day''
emissions are used in this instance to stay consistent between motor
vehicle emissions budgets of different ozone standards.
\18\ 86 FR 59643.
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On January 24, 2022, NDEP submitted the Clark County Second
Maintenance Plan showing how the area will continue to attain the 1997
8-hour ozone national ambient air quality standard (NAAQS) for 10
additional years beyond the approval the State's first 10-year plan.
Lastly, on August 16, 2023, NDEP submitted the Contingency Measure
Revision, which revised the contingency measure section of the Clark
County Second Maintenance Plan. In this action, we are proposing action
on the
[[Page 88302]]
NDEP's Clark County Second Maintenance Plan submittal.
III. Second 10-Year Maintenance Plan Submittal and Procedural
Requirements
CAA section 110(a)(1) and (2) and section 110(1) require states to
provide reasonable notice and public hearing prior to adoption of SIP
revisions. In this action, we are proposing action on NDEP's January
24, 2022, submittal of the Clark County Ozone Second Maintenance Plan,
and NDEP's August 16, 2023, submittal of the Contingency Measure
Revision as a revision to the Nevada SIP, collectively referred to as
the Clark County Second Maintenance Plan submittal.
Following a 30-day public comment period, the Clark County Second
Maintenance Plan was adopted by the Clark County Board of
Commissioners, submitted to NDEP, and submitted to the EPA. Appendix B
of the Clark County Second Maintenance Plan documents the public review
process followed by Clark County in adopting the plan prior to
transmittal to NDEP for subsequent submittal to the EPA as a revision
to the Nevada SIP. The documentation in 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 Clark County Second Maintenance Plan was
published on October 14, 2021, on the Clark County Department of
Environment and Sustainability (DES) website, the DES official Facebook
page, and the DES official Twitter. No comments were submitted.
On December 7, 2021, the Clark County Board of Commissioners set a
public hearing for December 21, 2021, to consider and approve the Clark
County Second Maintenance Plan. The announcement of the public hearing
was subsequently published on the County's web page. On December 21,
2021, the Clark County Board of Commissioners adopted the Clark County
Second Maintenance Plan at the close of the public hearing. Following
adoption, Clark County DES forwarded the plan to NDEP, the Governor of
Nevada's designee for SIP matters, and NDEP then submitted the plan as
a revision to the Nevada SIP to the EPA for approval on January 24,
2022.
Appendix A of the Contingency Measure Revision documents the board
approval process followed by Clark County in adopting the plan prior to
transmittal to NDEP for subsequent submittal to the EPA as a revision
to the Nevada SIP. On July 18, 2023, the Clark County Board of
Commissioners put the Contingency Measure Revision up for public notice
and adopted the Contingency Measure Revision at the close of the public
hearing. Following adoption, Clark County DES forwarded the plan to
NDEP and NDEP then submitted the plan, as a revision to the Nevada SIP,
to the EPA for approval on August 16, 2023.
Based on the documentation contained in appendix B of the Plan and
appendix A of the Contingency Measure Revision, we find that the Clark
County Second Maintenance Plan submittal satisfies the procedural
requirements of section 110(l) of the Act.
IV. Requirements for Second 10-Year Maintenance Plans
Section 175A of the CAA provides the general framework for a
maintenance plan. The initial 10-year maintenance plan must provide for
maintenance of the NAAQS for at least 10 years after redesignation,
including any additional control measures necessary to ensure such
maintenance. In addition, maintenance plans are to contain contingency
provisions necessary to ensure the prompt correction of a violation of
the NAAQS that occurs after redesignation. The contingency measures
must include, at a minimum, a requirement that the state will implement
all control measures contained in the nonattainment SIP prior to
redesignation. Beyond these provisions, section 175A of the CAA does
not define the content of a second 10-year maintenance plan.
The primary guidance on maintenance plans and redesignation
requests is a September 4, 1992, memorandum from John Calcagni, titled
``Procedures for Processing Requests to Redesignate Areas to
Attainment'' (Calcagni Memo).\19\ The Calcagni Memo outlines the key
elements of a maintenance plan, which include verification of continued
attainment, monitoring network requirements, attainment emissions
inventory, maintenance demonstration, and a contingency plan. We
evaluate the Second 10-Year Maintenance Plan based on the satisfactory
fulfillment of these and all relevant procedural requirements of the
CAA.
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\19\ Memorandum dated September 4, 1992, from John Calcagni,
Director, EPA Air Quality Management Division, to Regional Office
Air Division Directors, Subject: Procedures for Processing Requests
to Redesignate Areas to Attainment.
---------------------------------------------------------------------------
CAA section 175A(b) requires states to submit an additional SIP
revision (Second 10-Year Maintenance Plan) to maintain the NAAQS for an
additional 10 years after the expiration of the 10-year period covered
by the initial maintenance plan approved in connection with the
redesignation of the area from nonattainment to attainment. The
revision is submitted eight years after the original redesignation
request and maintenance plan have been approved. The deadline to submit
Clark County's Second Maintenance Plan was January 8, 2021. On January
24, 2022, NDEP submitted the Clark County Second Maintenance Plan, to
meet the requirement for the subsequent maintenance plan under CAA
section 175A(b). The Clark County Second Maintenance Plan is intended
to provide for continued maintenance of the 1997 ozone NAAQS for the
10-year period following the end of the first 10-year period, i.e.,
from 2024 through 2033.
V. Evaluation of the Clark County Second Maintenance Plan
Section 175A of the CAA sets forth the elements of a maintenance
plan. We interpret this section of the Act to require, in general, the
following core elements: attainment inventory, maintenance
demonstration, monitoring network, verification of continued
attainment, and contingency plan.\20\ Under CAA section 175A, a
maintenance plan must demonstrate continued attainment of the
applicable NAAQS for at least ten years after the EPA approves a
redesignation to attainment. Eight years after redesignation, the State
must submit a revised maintenance plan that demonstrates continued
attainment for the subsequent ten-year period following the initial
ten-year maintenance period. To address the possibility of future NAAQS
violations, the maintenance plan must contain such contingency
provisions that the EPA deems necessary to promptly correct any
violation of the NAAQS that occurs after redesignation of the area.
Based on our review and evaluation of the plan, as detailed below, we
are proposing to approve the Clark County Second Maintenance Plan
submittal because we believe that it meets the requirements of CAA
section 175A.
---------------------------------------------------------------------------
\20\ Calcagni Memo, 8-13.
---------------------------------------------------------------------------
A. Monitoring Network Requirements
Continued ambient monitoring of an area is generally required over
the maintenance period. Clark County DES currently operates ozone
monitors at thirteen sites within the Clark County 8-hour ozone
maintenance area.
[[Page 88303]]
In the Clark County Second Maintenance Plan,\21\ Clark County DES
indicates its intention to continue operation of an air quality
monitoring network to verify continued attainment of the 1997 8-hour
ozone NAAQS.\22\ The Clark County Second Maintenance Plan also notes
that Clark County DES's State and Local Air Monitoring Stations (SLAMS)
air quality monitoring network (which includes ambient ozone
monitoring) will be reviewed annually pursuant to 40 CFR 58.20(d) to
determine whether the system continues to meet the applicable
monitoring objectives.\23\ We approved Clark County's SLAMS air quality
network in their Annual Monitoring Network Plan for year 2020 on
October 28, 2020, prior to Clark County's submittal of the Clark County
Second Maintenance Plan. We find the County's commitment for continued
ambient ozone monitoring as set forth in the Clark County Second
Maintenance Plan to be acceptable.
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\21\ Clark County Second Maintenance Plan, 20-23.
\22\ Although the Clark County Second Maintenance Plan is not
explicit in this regard, we presume that Clark County DES's
intention to continue operation of a monitoring network means that
the agency intends to do so consistent with the EPA's monitoring
requirements in 40 CFR part 58 (``Ambient Air Quality
Surveillance'').
\23\ The EPA's requirements for annual review of monitoring
networks are no longer codified at 40 CFR 58.20(d) but are now found
at 40 CFR 58.10.
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B. Attainment Inventory
For maintenance plans, a state should develop a comprehensive and
accurate inventory of actual emissions for an attainment year which
identifies the level of emissions in the area which is sufficient to
maintain the NAAQS. The inventory should be developed consistent with
the EPA's most recent guidance. For ozone, the inventory should be
based on typical ozone season day emissions of NOX and VOC.
In the Clark County First Maintenance Plan, Clark County DES used
2008 for the attainment year inventory, because 2008 was one of the
years in the 2007-2009 three-year period when the area first attained
the 1997 ozone NAAQS.\24\ Clark County DES continued to monitor
attainment of the 1997 ozone NAAQS in 2017. Therefore, the emissions
inventory from 2017 represents emissions levels consistent with
continued attainment (i.e., maintenance) of the NAAQS. Thus, Clark
County DES selected 2017 as the year for the attainment inventory in
the Clark County Second Maintenance Plan. We consider the selection of
the 2017 base year inventory to be appropriate given that it was the
most recent emissions inventory associated with the reporting schedule
required under the Air Emissions Reporting Requirements rule at the
time of Plan drafting.
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\24\ 76 FR 17343 (Apr. 29, 2011).
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Table 1 presents the VOC and NOX emissions estimates
contained in the Clark County Second Maintenance Plan for 2017 and
presents the Plan's projected emissions inventories of ozone precursors
in an interim year (2023) and the maintenance plan's horizon year
(2033).\25\
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\25\ The emissions inventories reflect county-wide emissions
which include both the nonattainment area portion of the county and
the portion of the county designated as ``unclassifiable/
attainment'' for the 1997 8-hour ozone NAAQS. County-wide emissions
are acceptable to characterize emissions within the Clark County
ozone nonattainment area because over 95% of the population of the
county resides in the nonattainment area.
Table 1--Clark County 2017 and Projected 2023 and 2033 VOC and NOX Emissions Total Daily Emissions
[Tpd, average summer ozone season weekday]
--------------------------------------------------------------------------------------------------------------------------------------------------------
2017 2023 2033
Emissions source -----------------------------------------------------------------------------------------------
VOC NOX VOC NOX VOC NOX
--------------------------------------------------------------------------------------------------------------------------------------------------------
Point Source............................................ 2.95 12.34 2.62 11.41 2.63 11.33
Nonpoint Source......................................... 64.69 4.69 67.83 5.03 71.31 4.78
Mobile--On-road......................................... 26.27 42.20 17.85 22.22 11.50 11.13
Mobile--Nonroad......................................... 28.86 37.45 27.24 23.27 27.82 15.37
Airports................................................ 1.96 11.90 2.64 15.53 3.05 19.77
Locomotives............................................. 0.07 1.42 0.05 1.21 0.04 0.96
Emission Reduction Bank................................. 0.00 0.00 0.43 22.23 0.43 22.23
Biogenic................................................ 362.61 2.43 362.61 2.43 362.61 2.43
-----------------------------------------------------------------------------------------------
Total............................................... 487.41 112.43 481.27 103.33 479.39 88.00
--------------------------------------------------------------------------------------------------------------------------------------------------------
Source: Clark County Second Maintenance Plan, 17, Tables 2-4 and 2-5.
\a\ Emissions associated with the proposed Department of Air Force (DAF) Training Project is included in Airport emissions projections for the 2023 and
2033 emissions projections for general conformity purposes. Emissions associated with the proposed Southern Nevada Supplemental Airport and proposed
Sloan Regional Heliport are included for the 2033 emissions projection for general conformity purposes.
The data shown in Table 1 in this document is based on the 2017
National Emissions Inventory (NEI).\26\ The inventory addresses point
sources,\27\ nonpoint sources,\28\ on-road mobile, non-road mobile,
airports, locomotives, Emission Reduction Credits (ERCs),\29\ and
biogenic \30\ sources. Appendix A to the Clark County Second
Maintenance Plan contains source-specific descriptions of emissions
calculation procedures and sources of input data.
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\26\ 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.
\27\ The Clark County Second Maintenance Plan 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.
\28\ The Clark County Second Maintenance Plan 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.
\29\ The Clark County Second Maintenance Plan uses the term,
``ERCs'' to refer to allowances earned through voluntary pollutant
emission reductions such as equipment shutdowns or voluntarily
installed controls.
\30\ For the Clark County Second Maintenance Plan, ``biogenic
sources'' include agricultural crops; lawn grass; forests that
produce isoprene, monoterpene, and other VOC emissions; and soils
that generate trace amounts of NOX.
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Point sources are stationary sources that have a potential to emit
(PTE) greater than 100 tons per year of NOX or VOC. Clark
County DES adopted a lower threshold by including all title V
stationary sources and minor sources with a PTE greater than 10 tons of
VOC or 25 tons of NOX per year. Clark County DES based the
inventory estimates on source reported actual 2017 emissions data but
adjusted the reported values to reflect a typical ozone
[[Page 88304]]
season day at each emissions unit within the source facilities based on
information provided by the facilities.
Nonpoint sources include emissions from equipment, operations and
activities that are numerous and in total have significant emissions.
Clark County DES included emissions from minor sources, residential
combustion, agricultural burning, industrial solvents and graphic arts,
and degreasing operations. Clark County DES used several methods to
estimate area source activity levels and emissions, including applying
local activity levels, apportioning national or statewide activity
levels to the local level, applying per capita emission factors
considering county-specific populations and using specific method
abstracts detailed within the submittal.
Non-road emissions sources include equipment that either move under
their own power or can be moved from site to site.
The on-road emissions sector includes emissions from engines used
primarily to propel equipment on highways and other roads, including
passenger vehicles, motorcycles, and heavy-duty diesel trucks. Clark
County DES used MOVES3, EPA's MOVES3 emissions factors, fleet data from
Department of Motor Vehicles (DMV) registration data, Coordinated
Research council (CRC) vehicle speed data, the Regional Transportation
Commission (RTC) of Southern Nevada's transportation demand modeling
results, vehicle classification data from the June 2018 Clark County
Vehicle Classification Study,\31\ and 2017 Highway Performance
Monitoring System (HPMS) data from the Nevada Department of
Transportation (NDOT).
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\31\ Clark County DES completed a vehicle classification study
in June 2018. The study used 2014-2016 traffic count data collected
by the Nevada Department of Transportation (NDOT). Clark County DES
incorporated VMT mix profiles and temporal profiles, which DES
incorporated into the 2017 MOVES3 input database.
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Biogenic emissions are from vegetation and soil, and include crops,
lawn grass, and forests. Clark County DES used the Biogenic Emissions
Inventory System version 3.61 (BEIS3.61) embedded in the SMOKE 4.7
model for the month of July to generate average ozone season day
emissions for Clark County.
The airport sector includes emissions from aircraft from commercial
and federal aviation sources. Clark County DES relied on airport-
specific emissions inventory information provided by the Clark County
Department of Aviation (CCDOA) for the five commercial airports located
within the nonattainment area.
Locomotives include emissions from railroad and high-speed
passenger train emissions. Locomotive emissions were estimated by Clark
County DES based on local activity data collected for the Clark County
First Maintenance Plan and predicted emissions from high-speed
passenger train service.
ERCs refer to allowances earned through voluntary pollutant
emissions reductions such as equipment shutdowns or voluntarily
installed controls. Clark County adopted New Source Review (NSR) rule,
Section 12.7.5--Emission Reduction credits into the SIP,\32\ allowing
Clark County to adopt ERCs. In the Clark County First Maintenance Plan,
Clark County banked NOX and VOC credits from the Clark
County Department of Air Quality and Environmental Management (DAQEM)
ERC Bank,\33\ Reid Gardner ERCs,\34\ and Mohave ERCs.\35\ In the Clark
County Second Maintenance Plan, Clark County noted that ERCs have not
changed from the Clark County First Maintenance Plan.
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\32\ 79 FR 62350 (October 17, 2014).
\33\ See ``DAQEM ERC Bank'' for a list of sources contributing
to the DAQEM ERC Bank in Clark County.
\34\ NDEP banked Reid Gardner ERCs after the NV Energy--Reid
Gardner Station Power Plant, Unit #4 Steam Boiler was controlled
with a low-NOX burner in January 2010.
\35\ NDEP banked Mohave ERCs after the permanent shut down and
dismantling of the Southern California Edison Mohave Generating
Station in November 2009.
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The EPA has reviewed the emissions inventory submitted by Clark
County and proposes to conclude that the plan's inventory is based on
reasonable assumptions and methodologies, and that the inventory is
comprehensive, current, accurate, and consistent with applicable CAA
provisions and the Calcagni Memo. Therefore, we are proposing that the
inventory is acceptable for use in demonstrating maintenance of the
1997 ozone NAAQS.
C. Maintenance Demonstration
CAA section 175A(a) requires that the maintenance plan ``provide
for the maintenance of the national primary ambient air quality
standard for such air pollutant in the area concerned for at least 10
years after the redesignation.'' Generally, a state may demonstrate
maintenance of the ozone NAAQS by either showing that future emissions
of a pollutant or its precursors will not exceed the level of the
attainment inventory or by modeling to show that the future mix of
sources and emissions rates will not cause a violation of the
NAAQS.\36\ For areas that are required under the Act to submit modeled
attainment demonstrations, the maintenance demonstration should use the
same level of modeling.\37\ The Clark County 8-hour ozone nonattainment
area was not required to submit a modeled attainment demonstration, and
thus, the Clark County Second Maintenance Plan may demonstrate
maintenance based on a comparison of existing and future emissions of
ozone precursors.\38\
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\36\ Calcagni Memo, 9-11.
\37\ Id.
\38\ A maintenance demonstration need not be based on ozone
modeling. See Wall v. EPA, 265 F.3d. 426 (6th Cir. 2001); Sierra
Club v. EPA, 375 F.3d 537 (7th Cir. 2004). See also 66 FR 53094
(October 19, 2001), and 68 FR 25418 (May 12, 2003).
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Clark County used the 2017 national emissions inventory (NEI) data
as the baseline to develop growth factors for point, nonpoint, and
locomotive sources. Clark County DES used the EPA 2016 v.1 modeling
platform emissions data to develop per-year growth adjustment factors
for point, nonpoint, federal aviation, and locomotives. Clark County
DES used local activity data to develop commercial airport growth
factors and conducted MOVES3 modeling to project on-road and non-road
emissions. The derived growth adjustment factors were used to
extrapolate emissions to account for a 16-year (2017 through 2033)
spread. The 2033 growth factors were multiplied by the 2017 actual
emissions to produce the 2033 projected point source and various other
stationary source emissions; including Residential Wood Combustion,\39\
non-point VOC,\40\ airport,\41\ and locomotive emissions.\42\ An
interim year (2023) projected emissions inventory is also included. On-
road emissions were estimated for the 2017 base year and for projection
years 2023 and 2033 and reflect a 32 percent decrease in VMT from 2017
to 2023 and a 56 percent decrease in VMT from 2017 to 2033 based on
Regional Transit Commission (RTC) projections.\43\
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\39\ Clark County Second Maintenance Plan, Appendix A, 23.
\40\ Clark County Second Maintenance Plan, Appendix A, 24.
\41\ Clark County Second Maintenance Plan, Appendix A, 29.
\42\ Clark County Second Maintenance Plan, Appendix A, 31.
\43\ Clark County Second Maintenance Plan, 27, Table 6-1.
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In addition to accounting for areawide growth trends, Clark County
DES added emissions from specific projects that are expected to become
operational during the second maintenance period,
[[Page 88305]]
including the proposed Southern Nevada Supplemental Airport, the
proposed Sloan Regional Heliport, and DAF training program in the
future-year emissions inventories, and also added in ERCs from certain
stationary sources in the event that the ERCs are used for the purposes
of issuing permits for new or modified stationary sources in the air
quality planning area. We have reviewed the methods and assumptions, as
described in connection with the attainment inventory, that Clark
County DES used to project emissions to 2023 and 2033 for the various
source categories and find them to be reasonable.
Table 1 compares the VOC and NOX emissions estimated for
the Clark County 8-hour ozone maintenance area for 2017 with those for
2023 and 2033 by source category. The projected VOC and NOX
emissions show that VOC and NOX emissions would remain well
below the attainment levels throughout the second 10-year maintenance
period and thereby adequately demonstrate maintenance through that
period.
In addition, historical monitoring data presented in the plan shows
a gradual downward trend in ozone design values during 2008-2020. The
1997 NAAQS level of 80 ppb was achieved in 2009, and the 2020 value of
74 ppb is well below the NAAQS.\44\ This supports the maintenance
demonstration, and the EPA expects this downward trend will continue
given the projected emissions decreases.
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\44\ Clark County Second Maintenance Plan, 12, Figure 2-1.
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D. Verification of Continued Attainment
NDEP and the Clark County Board of County Commissioners have the
legal authority to implement and enforce the requirements of the Clark
County Second Maintenance Plan. This includes the authority to adopt,
implement and enforce any emissions control contingency measures
determined to be necessary to correct ozone NAAQS violations. To verify
continued attainment, Clark County DES commits in the Clark County
Second Maintenance Plan to the continued operation of an ozone
monitoring network that meets the EPA ambient air quality surveillance
requirements.
Secondly, the transportation conformity process represents another
means by which to verify continued attainment of the 1997 8-hour ozone
NAAQS in the Clark County 8-hour ozone area given the relative
importance of motor vehicle emissions to the overall emissions
inventories of ozone precursors.\45\
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\45\ Clark County Second Maintenance Plan, Page 15.
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Lastly, while not cited in the plan, NDEP and Clark County DES must
inventory emissions sources and report to the EPA on a periodic basis
under 40 CFR part 51, subpart A (``Air Emissions Reporting
Requirements''). These emissions inventory updates will provide a third
means with which to track emissions in the area relative to those
projected in the maintenance plan and thereby verify continued
attainment of the NAAQS. These methods are sufficient for the purpose
of verifying continued attainment.
E. Contingency Provisions
Section 175A(d) of the Act requires that maintenance plans include
contingency provisions, as the EPA deems necessary, to promptly correct
any violations of the NAAQS that occur after redesignation of the area.
Such provisions must include a requirement that the State will
implement all measures with respect to the control of the air pollutant
concerned which were contained in the SIP for the area before
redesignation of the area as an attainment area.
Under section 175A(d), contingency measures identified in the
contingency plan do not have to be fully adopted at the time of
redesignation. However, the contingency plan is an enforceable part of
the SIP and should ensure that the contingency measures are adopted
expeditiously once they are triggered by a specified event. The
maintenance plan should clearly identify the measures to be adopted, a
schedule and procedure for adoption and implementation, and a specific
timeline for action by the State. As a necessary part of the plan, the
State should also identify specific indicators or triggers, which will
be used to determine when the contingency measures need to be
implemented.
As required by section 175A of the CAA, Clark County DES has
adopted a contingency plan to address possible future ozone air quality
problems.\46\ Clark County DES identifies the trigger date as 60 days
after a determination of a confirmed violation of the 1997 8-hour ozone
NAAQS. Within 45 days of the trigger date, Clark County will notify the
EPA that it is evaluating potential contingency measures. Within 90
days of the trigger date, Clark County will send a report to the EPA
and then will initiate a public process to consider the recommended
contingency measures, including soliciting stakeholder involvement and
holding public hearings. The necessary emissions control measures will
be adopted and implemented no later than 18 months after the trigger
date.
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\46\ Contingency Measure Revision, Section 2, ``Contingency
Measures Plan.''
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Potential contingency measures listed in the maintenance plan are
those emissions controls or other measures that Clark County, the
Nevada State Board of Agriculture, and/or the Nevada State
Environmental Commission may choose to adopt and implement in response
to the contingency trigger. The contingency measures plan in the
Contingency Measure Revision lists the following potential contingency
measures that will be considered for adoption and implementation by the
applicable State or County agency, but the Plan indicates that the list
is not to be considered exclusive:
Reid vapor pressure reduction (i.e., in gasoline sold
during the summer ozone season; would need to be adopted and
implemented by the Nevada State Board of Agriculture);
Inspection/maintenance program changes and additions
(e.g., lowering the cut points for VOCs and NOX applicable
to pre-1996 vehicles; would need to be adopted and implemented by the
State Environmental Commission and/or the State Department of Motor
Vehicles);
Consumer and commercial products (Clark County would be
responsible for adoption and implementation);
Architectural surface coatings (Clark County would be
responsible for adoption and implementation);
Lawn and garden equipment use (Clark County would be
responsible for adoption and implementation); and
Establish/enhance trip reduction programs (Clark County
and the RTC would be responsible for adoption and implementation).
Upon our review of the plan, we find that the contingency
provisions of the Contingency Measure Revision clearly identify
specific contingency measures, contain tracking and triggering
mechanisms to determine when contingency measures are needed, contain a
description of the process of recommending and implementing contingency
measures, and contain specific timelines for action. Thus, we conclude
that the contingency provisions of the Contingency Measure Revision are
adequate to ensure prompt correction of a violation and therefore
comply with section 175A(d) of the Act.
F. Motor Vehicle Emissions Budgets for Transportation Conformity
Section 176(c) of the CAA requires federal actions in nonattainment
and
[[Page 88306]]
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, RTCs in nonattainment and maintenance areas
coordinate with state and local air quality and transportation
agencies, the EPA, FHWA, and FTA to demonstrate that an area's regional
transportation plans and transportation improvement programs conform to
the applicable SIP. This demonstration is typically done by showing
that estimated emissions from existing and planned highway and transit
systems are less than or equal to the motor vehicle emissions budgets
(``budgets'') contained in submitted or approved control strategy SIPs
and maintenance plans.\47\
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\47\ Control strategy SIPs refer to RFP and attainment
demonstration SIPs. 40 CFR 93.101.
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These control strategy SIPs and maintenance plans typically set
budgets for criteria pollutants and/or their precursors to address
pollution from cars and trucks. Budgets are generally established for
specific years and specific pollutants or precursors. Maintenance plan
submittals should identify budgets for transportation-related VOC and
NOX emissions in the last year of the maintenance period.
For budgets in a maintenance plan to be approvable, they must meet,
at a minimum, the EPA's adequacy criteria.\48\ To meet these
requirements, the budgets must be consistent, when considered with
emissions from all other sources, with maintenance of the NAAQS and
reflect all the motor vehicle control measures relied upon for the
maintenance demonstration. 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 MVEB during a public comment period; and
(3) making a finding of adequacy. The process for determining the
adequacy of a submitted budget is codified at 40 CFR 93.118(f). The EPA
can notify the public by either posting an announcement that the EPA
has received SIP budgets on the EPA's adequacy website, or via a
Federal Register notice of proposed rulemaking when the EPA reviews the
adequacy of a maintenance plan budget simultaneously with its review
and action on the SIP submittal itself.\49\
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\48\ 40 CFR 93.118(e)(4) and (5). For more information on the
transportation conformity requirement and applicable policies on
MVEBs, please visit our transportation conformity website at: https://www.epa.gov/otaq/stateresources/transconf/index.htm.
\49\ 40 CFR 93.118(f)(2).
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Clark County's Second Maintenance Plan contains VOC and
NOX budgets for 2017, 2023 and 2033. Any and all comments on
the approvability of the budgets should be submitted during the comment
period stated in the DATES section of this document.
The EPA proposes to approve 2017, 2023, and 2033 budgets in the
Clark County Second Maintenance Plan for transportation conformity
purposes in the final rulemaking on Clark County's ozone redesignation
request. If the EPA approves the budgets in the final rulemaking
action, the new budgets must be used in future transportation
conformity determinations for Clark County for the 2015 ozone standard.
The new budgets, if approved in the final rulemaking, will be effective
on the date of the EPA's final rulemaking in the Federal Register. The
applicable VOC and NOX MVEBs for the Clark County ozone
nonattainment area are defined in table 2.
Table 2--Proposed Motor Vehicle Emissions Budgets (MVEBs) for Clark County
----------------------------------------------------------------------------------------------------------------
VOC (tpd, average summer NOX (tpd, average summer
Budget year weekday) weekday)
----------------------------------------------------------------------------------------------------------------
2017........................................ 26.27 42.2
2023........................................ 20.92 26.77
2033........................................ 15.51 23.35
----------------------------------------------------------------------------------------------------------------
From Table 6-3 and 6-4 of the Clark County Second Maintenance Plan.
The MVEBs are the on-road mobile source VOC and NOX
emissions for Clark County for 2017, 2023 and 2033. The budgets are
compatible with the 2017, 2023, and 2033 on-road mobile source VOC and
NOX emissions included in Clark County's 2017, 2023, and
2033 VOC and NOX emission inventories, as summarized in
Table 2. The derivation of the budgets is thoroughly discussed in
Appendix A, Chapter 2 of Clark County's Second Maintenance Plan. While
the Plan includes budgets for 2017, we are not evaluating the 2017
budgets because that year would not be used in any future conformity
determination because the plan contains budgets for 2023 and because
2017 budgets are not required for the submitted second maintenance
plan.
We evaluated the budgets against our adequacy criteria in 40 CFR
93.118(e)(4) and (5) as part of our review of the budget's
approvability and expect to complete the adequacy review of the budgets
concurrent with our final action on the Clark County's Second
Maintenance Plan. The EPA is not required under its transportation
conformity rule to find budgets adequate prior to proposing approval of
them. In this notice, the EPA is announcing that the adequacy process
for these budgets begins, and the public has 30 days to comment on
their adequacy, per the transportation conformity rule at 40 CFR
93.118(f)(2)(i) and (ii).
Clark County DES developed the budgets for 2023 and 2033 using on-
road motor vehicle emission estimates made using the EPA's MOVES3
model, fleet data from DMV registration data, CRC vehicle speed data,
NDOT HPMS data, travel demand modeling from the Regional Transportation
Commission and vehicle classification data from the June 2018 Clark
County On-road Vehicle Classification Study.
As documented in the separate memorandum \50\ included in the
docket for this rulemaking, we preliminarily conclude that the budgets
in the Second Maintenance Plan meet each adequacy criterion. While
adequacy and approval
[[Page 88307]]
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 and are proposing to
approve the demonstration of maintenance for the 1997 ozone maintenance
area through the year 2033. We have also reviewed the budgets in Clark
County's Second Maintenance Plan and found that they are consistent
with the maintenance demonstration for which we are proposing approval,
are clearly identified and precisely quantified, 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 93.118(e)(4) and (5). The EPA is proposing
to approve the budgets for 2023 and 2033 as part of our approval of
Clark County's Second Maintenance Plan. At the point when we either
finalize the adequacy process or approve the budgets as proposed
(whichever occurs first; note that they could also occur concurrently
per 40 CFR 93.118(f)(2)(iii)), the budgets must be used by the Regional
Transportation Commission (i.e., the Metropolitan Planning Organization
(MPO) for this area) for transportation conformity determinations for
the Clark County 2015 ozone nonattainment area.
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\50\ See the EPA Memorandum dated August 22, 2023 titled:
Adequacy Documentation for Motor Vehicle Emissions Budgets in Clark
County Second Maintenance Plan.''
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VI. Environmental Justice Considerations
The EPA performed a screening-level analysis using the EPA's
environmental justice (EJ) screening and mapping tool (``EJSCREEN'').
Our screening-level analysis included multiple environmental and
demographic indicators, including the EJSCREEN ``Demographic Index,''
which is the average of an area's percentage of minority and low-income
populations. The Demographic Index of Clark County is at the 68th
percentile, compared to the United States as a whole.\51\ The results
of this analysis are being provided for informational and transparency
purposes.
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\51\ Clark County Ozone NAA EJSCREEN Report dated February 10,
2023.
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This action addresses a plan for continued maintenance of the 1997
ozone NAAQS for Clark County. Approval of this plan does not impose any
additional regulatory requirements on sources beyond those imposed by
state law. As discussed in this document, Nevada has demonstrated that
the Clark County is attaining the 1997 ozone NAAQS and the Clark County
Second Maintenance Plan provides for the maintenance of the NAAQS for
the reminder of the maintenance period. We expect that this action will
generally be neutral or contribute to reduced environmental and health
impacts on all populations in Clark County, including people of color
and low-income populations. At a minimum, this action would not worsen
any existing air quality and is expected to ensure the area is meeting
requirements to maintain air quality standards. Further, there is no
information in the record indicating that this action is expected to
have disproportionately high or adverse human health or environmental
effects on a particular group of people.
VII. Proposed Action and Request for Public Comment
Under CAA section 110(k)(3), and for the reasons set forth in this
document, the EPA is proposing to approve the Clark County Second
Maintenance Plan submitted by NDEP on January 24, 2022, as a revision
to the Nevada SIP.\52\ We are proposing to approve the maintenance
demonstration and contingency provisions as meeting all applicable
requirements for maintenance plans and related contingency provisions
in CAA section 175A, and the budgets for 2023 and 2033 (shown in Table
2) for transportation conformity purposes as we find they meet all
applicable criteria for such budgets including the adequacy criteria
under 40 CFR 93.118(e).
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\52\ Clark County Second Maintenance Plan (submitted
electronically January 24, 2022).
---------------------------------------------------------------------------
We are soliciting comments on these proposed actions. We will
accept comments from the public for 30 days following publication of
this proposal in the Federal Register and will consider any relevant
comments before taking final action.
VIII. Statutory and Executive Order Reviews
Under the Clean Air Act, the Administrator is required to approve a
SIP submission that complies with the provisions of the Act and
applicable federal regulations. 42 U.S.C. 7410(k); 40 CFR 52.02(a).
Thus, in reviewing SIP submissions, the EPA's role is to approve state
choices, provided that they meet the criteria of the Clean Air Act.
Accordingly, this proposed action merely proposes to approve state law
as meeting federal requirements and does not impose additional
requirements beyond those imposed by state law. For that reason, this
proposed action:
Is not a ``significant regulatory action'' subject to
review by the Office of Management and Budget under Executive Orders
12866 (58 FR 51735, October 4, 1993) and 13563 (76 FR 3821, January 21,
2011);
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
Will not have disproportionately high and adverse human
health or environmental effects on minority populations, low-income
populations and/or indigenous peoples, as specified in Executive Order
12898 (59 FR 7629, February 16, 1994), as discussed in section VI of
this proposal.
In addition, there are no areas of Indian country within the
planning area, and the state plan for which the EPA is proposing
approval does not 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 Clark County Second
Maintenance Plan does not apply, and therefore, this proposed action
does not have tribal implications and would not, if approved, 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, Nitrogen dioxide, Particulate matter, Sulfur dioxide,
Reporting and recordkeeping requirements, Volatile organic compounds.
Authority: 42 U.S.C. 7401 et seq.
[[Page 88308]]
Dated: December 14, 2023.
Martha Guzman Aceves,
Regional Administrator, Region IX.
[FR Doc. 2023-27874 Filed 12-20-23; 8:45 am]
BILLING CODE 6560-50-P
