Document ID: EPA-R09-OAR-2019-0365-0001
Agency: epa
Document Type: Proposed Rule
Title: Air Quality State Implementation Plans; Approvals and Promulgations: Nevada; Revisions to Clark County Ozone Maintenance Plan
Posted Date: 2019-07-11T04:00Z

[Federal Register Volume 84, Number 133 (Thursday, July 11, 2019)]
[Proposed Rules]
[Pages 33035-33045]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2019-14630]

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ENVIRONMENTAL PROTECTION AGENCY

40 CFR Part 52

[EPA-R09-OAR-2019-0365; FRL-9996-40-Region 9]

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

AGENCY: Environmental Protection Agency (EPA).

ACTION: Proposed rule.

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SUMMARY: The Environmental Protection Agency (EPA) is proposing to 
conditionally approve a revision to the State of Nevada's State 
Implementation Plan (SIP) for Clark County. The revision consists of an 
update to certain elements of the maintenance plan for the Clark County 
air quality planning area for the 1997 8-hour ozone national ambient 
air quality standards (NAAQS or ``standards''), including the emissions 
inventories, maintenance demonstration, and motor vehicle emissions 
budgets. The EPA is proposing to conditionally approve the SIP revision 
because the Clark County ozone SIP, as revised, continues to provide 
for maintenance of the 1997 ozone NAAQS and, upon fulfillment of 
certain commitments, will not interfere with attainment or reasonable 
further progress of the other NAAQS, and the budgets meet the 
applicable transportation conformity requirements. The proposed 
approval is conditional because it is based on commitments to submit a 
SIP revision to reduce the safety margin allocations for the budgets 
within one year of final conditional approval.

DATES: Comments must be received on or before August 12, 2019.

ADDRESSES: Submit your comments, identified by Docket ID No. EPA-R09-
OAR-2019-0365, 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.

FOR FURTHER INFORMATION CONTACT: Karina O'Connor, Air Planning Office 
(AIR-2), EPA Region IX, 75 Hawthorne Street, San Francisco, CA 94105; 
By phone: (775) 434-8176 or by email at oconnor.karina@epa.gov.

SUPPLEMENTARY INFORMATION: Throughout this document, whenever ``we,'' 
``us,'' or ``our'' is used, we mean the EPA. This supplementary 
information section is arranged as follows:

Table of Contents

I. What action is the EPA proposing?
II. Background
    A. NAAQS, SIPs, Designations, and Transportation Conformity
    B. 1997 Ozone NAAQS and Clark County
    C. 2008 Ozone NAAQS and Clark County
    D. 2015 Ozone NAAQS and Clark County
    E. The MOVES Emission Model
III. What did the State submit?
IV. Procedural Requirements for Adoption and Submittal of SIP 
Revisions
V. The EPA's Evaluation of the 2018 Ozone Maintenance Plan Revision

[[Page 33036]]

    A. Revised Attainment Inventory
    B. Revised Maintenance Demonstration
    C. Revised Motor Vehicle Emissions Budgets
    D. CAA Section 110(l) Evaluation
VI. Proposed Action and Request for Public Comment
VII. Statutory and Executive Order Reviews

I. What action is the EPA proposing?

    Under section 110(k) of the Clean Air Act (``Act'' or CAA), the EPA 
is required to take action by approving, disapproving, or conditionally 
approving, in whole or in part, SIPs and SIP revisions submitted by the 
states. In today's action, the EPA is proposing to conditionally 
approve a SIP revision titled ``Revision to Motor Vehicle Emissions 
Budgets in Ozone Redesignation Request and Maintenance Plan: Clark 
County, Nevada'' (October 2018) (herein, referred to as the ``2018 
Ozone Maintenance Plan Revision''), submitted by the Nevada Division of 
Environmental Protection (NDEP) on October 31, 2018. The 2018 Ozone 
Maintenance Plan Revision updates certain elements of the maintenance 
plan for Clark County for the 1997 ozone NAAQS, including the 
attainment inventory, the maintenance plan, and the motor vehicle 
emissions budgets (``budgets'' or MVEBs). The budgets were updated 
using the EPA's MOtor Vehicle Emission Simulator emission model 
released in 2014 (MOVES2014a). If the EPA takes final action to 
conditionally approve the SIP revision, the updated budgets will 
replace Clark County's existing budgets for the 1997 ozone NAAQS. At 
that time, the previously-approved budgets would no longer be 
applicable for transportation conformity purposes, and the revised 
budgets would need to be used beginning on the publication date of the 
EPA's final conditional approval in the Federal Register.\1\ The 
proposed conditional approval is based on commitments from NDEP and the 
Clark County Department of Air Quality (DAQ) to submit a SIP revision 
within one year of final conditional approval.\2\ The purpose of the 
future SIP revision is to reduce the safety margin allocations to the 
budgets to ensure that the 2018 Ozone Maintenance Plan Revision, as 
revised to reduce the safety margin allocations, will not interfere 
with reasonable further progress or attainment of the 2008 and 2015 
ozone NAAQS.
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    \1\ 40 CFR 93.118(f)(2)(v).
    \2\ Letter from Jodi Bechtel, Assistant Director, Clark County 
DAQ, to Greg Lovato, Administrator, NDEP, dated June 14, 2019; and 
letter from Greg Lovato, Administrator, NDEP, to Elizabeth Adams, 
Director, Air Division, EPA Region IX, dated June 21, 2019.
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II. Background

A. NAAQS, SIPs, Designations, and Transportation Conformity

    Under section 109 of the CAA, the EPA promulgates NAAQS for 
pervasive air pollutants, such as ozone. The NAAQS are concentration 
levels that, the attainment and maintenance of which, the EPA has 
determined to be requisite to protect public health and welfare. Once 
the EPA has established a NAAQS or revised a NAAQS, section 110 of the 
CAA requires states to adopt and submit to the EPA a plan, referred to 
as the SIP, that provides for the implementation, maintenance, and 
enforcement of such NAAQS. As noted previously, the EPA is required to 
take action to approve, disapprove, or conditionally approve SIPs and 
SIP revisions under CAA section 110(k).
    Under CAA section 107(d), the EPA must designate all areas of the 
country as attainment, nonattainment or unclassifiable for new or 
revised NAAQS. States with areas designated as nonattainment must 
develop, adopt and submit SIP revisions to provide for, among other 
things, attainment as expeditiously as practicable but no later than 
certain dates and for reasonable further progress (RFP) towards 
attainment.\3\ Once a nonattainment area has attained the NAAQS, the 
state may request redesignation of the area from nonattainment to 
attainment, and the EPA grants such requests if the criteria in CAA 
section 107(d)(3)(E) are met, including the approval of a maintenance 
plan (under CAA section 175A) that demonstrates how the area will 
maintain the NAAQS for at least 10 years after the redesignation. Such 
former nonattainment areas that have been redesignated to attainment 
are referred to as ``maintenance areas.''
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    \3\ See, generally, part D (``Plan Requirements for 
Nonattainment Areas'') of Title I of the CAA.
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    In the State of Nevada, NDEP is the Governor's designee for 
adoption and submittal of SIPs and SIP revisions to the EPA. NDEP is 
also responsible for regulation of stationary sources and development 
of local air quality plans throughout much of the State of Nevada. In 
Clark County, the Clark County DAQ is responsible under state law for 
regulation of most types of stationary sources within the county and 
for development of local air quality plans. Once adopted by the Clark 
County Board of County Commissioners, such county plans are forwarded 
to NDEP for adoption and submittal to the EPA as revisions to the 
Nevada SIP.
    The emission control strategy SIP revisions (e.g., RFP and 
attainment demonstration SIP revisions) and maintenance plans include 
budgets of on-road mobile source emissions for criteria pollutants and/
or their precursors to address pollution from cars and trucks. The 
budgets are the portions of the total allowable emissions that are 
allocated to on-road vehicle use that, together with emissions from 
other sources in the area, will provide for RFP, attainment or 
maintenance. The budgets serve as a ceiling on emissions from an area's 
planned transportation system.\4\
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    \4\ For more information about budgets, see the preamble to the 
November 24, 1993, transportation conformity rule (58 FR 62188).
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    The CAA recognizes the connection between air quality planning and 
transportation planning in nonattainment and maintenance areas and 
includes specific provisions related to adoption and approval of 
transportation programs, plans, and projects by Metropolitan Planning 
Organizations (MPOs) and the U.S Department of Transportation's (DOT's) 
Federal Highway Administration (FHWA) or Federal Transit Administration 
(FTA). More specifically, under section 176(c) of the CAA, 
transportation plans, Transportation Improvement Programs (TIPs), and 
transportation projects must ``conform'' to (i.e., be consistent with) 
the SIP before they can be adopted or approved. Conformity to the SIP 
means that transportation activities will not cause new air quality 
violations, worsen existing air quality violations, or delay timely 
attainment of the NAAQS or delay an interim milestone. The EPA's 
transportation conformity rule at 40 CFR part 93, subpart A establishes 
the criteria and procedures that MPOs and DOT must use to determine 
whether transportation activities conform to the SIP. Transportation 
conformity applies to areas that are designated nonattainment and those 
former nonattainment areas that have been redesignated to attainment 
and have a CAA section 175A maintenance plan (``maintenance areas''), 
but does not apply to areas designated as attainment or 
unclassifiable.\5\
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    \5\ CAA section 176(c)(5).
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    Under certain circumstances, MPOs and DOT must determine conformity 
based, in part, on a ``budget test'' that involves a comparison between 
estimates of regional on-road mobile source emissions under a given 
transportation plan or program with the budgets.\6\ Before budgets can 
be used in

[[Page 33037]]

conformity determinations, however, the EPA must affirmatively find the 
budgets adequate.\7\ However, adequate budgets do not supersede 
approved budgets for the same CAA purpose. If the submitted SIP budgets 
are meant to replace budgets for the same purpose, the EPA must approve 
the budgets, and can affirm that they are adequate at the same time. 
Once the EPA approves the submitted budgets, they must be used by state 
and federal agencies in determining whether transportation activities 
conform to the SIP as required by section 176(c) of the CAA. The EPA's 
substantive criteria for determining the adequacy of budgets are set 
out in 40 CFR 93.118(e)(4).
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    \6\ CAA section 176(c)(1) and 40 CFR 93.109 and 93.118.
    \7\ The ``adequacy'' process is established in the EPA's 
transportation conformity rule to provide a mechanism whereby 
budgets in a submitted SIP revision that has undergone preliminary 
review by the EPA can be used for transportation planning purposes 
prior to final approval of the SIP revision.
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    In Clark County, the area's MPO, the Regional Transportation 
Commission of Southern Nevada (RTC) and DOT are the relevant 
transportation agencies that must use approved or adequate budgets in 
determining the conformity of transportation plans and TIPs within 
Clark County.

B. 1997 Ozone NAAQS and Clark County

    Ground-level ozone pollution is formed from the reaction of 
volatile organic compounds (VOC) and oxides of nitrogen 
(NOX) in the presence of sunlight. These two pollutants, 
referred to as ozone precursors, are emitted by many types of sources, 
including on-and off-road motor vehicles and engines, power plants and 
industrial facilities, and smaller area sources such as lawn and garden 
equipment and paints. 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.\8\
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    \8\ ``Fact Sheet--2008 Final Revisions to the National Ambient 
Air Quality Standards for Ozone'' dated March 2008.
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    As noted previously, the EPA promulgates NAAQS for pervasive air 
pollutants, such as ozone, under CAA section 109. In 1997, the EPA 
revised the ozone NAAQS to set the acceptable level of ozone in the 
ambient air at 0.08 parts per million (ppm), averaged over an 8-hour 
period (herein referred to as the ``1997 ozone NAAQS'').\9\ In 2004, 
the EPA designated and classified all areas with respect to the 1997 
ozone NAAQS, and designated Clark County as a ``Subpart 1'' 
nonattainment area for the 1997 ozone NAAQS.\10\ Later that year, the 
EPA reduced the geographic extent of the ozone nonattainment area to a 
portion of Clark County.\11\ In 2005, we published a final rule that we 
would treat the effective date of the partial-county nonattainment area 
designation the same as the designations for the rest of the country, 
i.e., June 15, 2004.\12\
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    \9\ 62 FR 38856 (July 18, 1997) and 40 CFR 50.10. Due to the 
number of significant figures in the level of the standard, a 
computed 3-year average ozone concentration of 0.085 ppm is the 
smallest value that is greater than 0.08 ppm. 40 CFR part 51, 
appendix I.
    \10\ 69 FR 23858 (April 30, 2004). The ``Subpart 1'' 
classification meant that the area was subject solely to the general 
nonattainment area requirements under subpart 1 of part D (of title 
I) of the CAA rather than to the requirements under both subparts 1 
and the ozone-specific requirements under subpart 2. Several years 
later, in response to litigation over the designations for the 1997 
ozone NAAQS, the EPA revised the classification of the Clark County 
ozone nonattainment area from ``Subpart 1'' to ``Subpart 2/
Marginal.'' 77 FR 28424 (May 14, 2012).
    \11\ 69 FR 55956 (September 17, 2004). The boundaries of the 
Clark County ozone nonattainment (now maintenance) area for the 1997 
ozone NAAQS 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. The hydrographic areas are illustrated in Figure 1-1 
of the Clark County Ozone Maintenance Plan (March 2011).
    \12\ 70 FR 71612 (November 29, 2005).
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    As a ``Subpart 1'' area, the Clark County ozone nonattainment area 
was subject to a number of requirements including the requirement to 
demonstrate attainment of the 1997 ozone NAAQS as expeditiously as 
practicable, but no later than five years from the date that the area 
was designated nonattainment.\13\ In 2011, the EPA determined that the 
Clark County 8-hour ozone nonattainment area had attained the 1997 8-
hour ozone NAAQS, based on complete, quality-assured, and certified 
ambient air monitoring data that showed the area monitored attainment 
of the 1997 ozone NAAQS for the 2007-2009 monitoring period.\14\
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    \13\ CAA section 172(a)(2).
    \14\ 76 FR 17343 (March 29, 2011).
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    In 2011, in light of ambient monitoring data showing that the Clark 
County ozone nonattainment had attained the 1997 ozone NAAQS, NDEP 
submitted the ``Ozone Redesignation Request and Maintenance Plan, Clark 
County, Nevada (March 2011)'' (herein, the ``2011 Ozone Maintenance 
Plan'') to the EPA for approval as a revision to the Clark County 
portion of the Nevada SIP. Prepared by the Clark County DAQ, the 2011 
Ozone Maintenance Plan includes the various elements found in most 
maintenance plans, including an attainment inventory, maintenance 
demonstration, monitoring network, verification of continued 
attainment, contingency plan, and motor vehicle emissions budgets.
    For the 2011 Ozone Maintenance Plan, Clark County DAQ selected 2008 
as the year for the attainment inventory of ozone precursors (i.e., VOC 
and NOX), and demonstrated maintenance of the 1997 ozone 
NAAQS through year 2022 by reference to emissions inventories developed 
for future years 2015 and 2022 that showed that future emissions of VOC 
and NOX would not exceed the level of the corresponding 
emissions of the attainment inventory. The 2011 Ozone Maintenance Plan 
established budgets for NOX and VOC for years 2008, 2015 and 
2022. The budgets were derived from the on-road motor vehicle emissions 
estimates prepared using the EPA's then-current on-road vehicle 
emissions model, MOBILE6.2, and the most recent vehicle mix and 
activity data then available from the RTC. In 2013, the EPA approved 
the 2011 Ozone Maintenance Plan and redesignated the Clark County ozone 
nonattainment area to attainment for the 1997 ozone NAAQS.\15\ The 
subject of today's proposed action is a revision to the attainment 
inventory, the maintenance demonstration and budgets of the 2011 Ozone 
Maintenance Plan to reflect updated emissions models, vehicle mix and 
speed data, and transportation activity projections. The other elements 
of the 2011 Ozone Maintenance Plan (monitoring network, verification of 
continued attainment, contingency plan) are not affected by this 
action.
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    \15\ 78 FR 1149 (January 8, 2013).
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    Through adoption of the 2011 Ozone Maintenance Plan, Clark County 
DAQ committed to maintaining an ambient air quality monitoring network 
to verify the continued attainment of the 1997 ozone NAAQS in the Clark 
County ozone maintenance area.\16\ At the present time, monitors 
operating at 10 monitoring sites continuously monitor ambient 
concentrations of ozone within the maintenance area. Since 2008, i.e., 
the year used for the attainment inventory in the 2011 Ozone 
Maintenance Plan, Clark County has experienced a decrease in ambient 
ozone concentrations. As shown in Table 1, 8-hour ozone design values 
have decreased from 0.082 ppm in 2008

[[Page 33038]]

to 0.074 ppm in 2017.\17\ In more recent years, the design value has 
remained relatively steady, varying little from year to year. Table 1 
shows that Clark County has maintained the 1997 ozone NAAQS through the 
first 5 years (2013 through 2017) of the first maintenance period.
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    \16\ 2011 Ozone Maintenance Plan, page 6-11.
    \17\ Under EPA regulations at 40 CFR 50.10 and appendix I, the 
1997 ozone NAAQS is attained at a site when the 3-year average of 
the annual fourth-highest daily maximum 8-hour average ozone 
concentration is less than or equal to 0.08 ppm. This 3-year average 
is referred to as the design value. When the design value is less 
than or equal to 0.084 ppm (based on the rounding convention in 40 
CFR part 50, appendix I) at each monitoring site within the area, 
then the area is meeting the 1997 ozone NAAQS. The highest design 
value among the various ozone monitoring sites represents the design 
value for the area.

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

C. 2008 Ozone NAAQS and Clark County

    Meanwhile, in 2008, the EPA lowered the ozone NAAQS to a level of 
0.075 ppm, 8-hour average (herein, the ``2008 ozone NAAQS''),\18\ and 
in 2012, the EPA designated all of the hydrographic areas within the 
State of Nevada as ``Unclassifiable/Attainment'' for the 2008 ozone 
NAAQS.\19\ Because all the hydrographic areas located entirely, or 
partially, within Clark County were designated as Unclassifiable/
Attainment for the 2008 ozone NAAQS, no RFP or attainment SIP revision 
was required for any portion of the county, and the transportation 
conformity requirements did not apply for that ozone NAAQS.
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    \18\ 73 FR 16436 (March 27, 2008) and 40 CFR 50.15.
    \19\ 77 FR 30088 (May 21, 2012). Hydrographic areas are those 
that are shown on the State of Nevada Division of Water Resources' 
map titled ``Water Resources and Inter-basin Flows'' (September 
1971).
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    In 2015, the EPA issued a SIP Requirements Rule (SRR) for the 2008 
ozone NAAQS (``2008 Ozone SRR'') that addressed implementation of the 
2008 standards, including attainment dates, requirements for emissions 
inventories, attainment and reasonable further progress (RFP) 
demonstrations, among other SIP elements, as well as the transition 
from the 1997 ozone NAAQS to the 2008 ozone NAAQS and associated anti-
backsliding requirements.\20\ The 2008 Ozone SRR revoked the 1997 ozone 
NAAQS effective April 6, 2015.
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    \20\ 80 FR 12264 (March 6, 2015) and 40 CFR part 51, subpart AA.
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    The EPA's 2008 Ozone SRR was challenged, and on February 16, 2018, 
the U.S. Court of Appeals for the D.C. Circuit (``D.C. Circuit'') 
published its decision in South Coast Air Quality Management District 
v. EPA (``South Coast II'') vacating certain portions of the 2008 Ozone 
SRR, but upholding the EPA's revocation of the 1997 ozone NAAQS.\21\ 
The only aspect of the South Coast II decision that affects this 
proposed action is the vacatur of the elimination of transportation 
conformity in areas that were maintenance areas for the 1997 ozone 
NAAQS at the time of revocation of the 1997 ozone NAAQS and were 
designated as attainment for the 2008 ozone NAAQS, which the court 
referred to as ``orphan maintenance areas.'' The Clark County 1997 
ozone maintenance area is an orphan maintenance area. The 2008 ozone 
SRR had provided that such areas are no longer required to determine 
transportation conformity for the 1997 ozone NAAQS after the 1997 ozone 
NAAQS is revoked.\22\ The court, however, held that transportation 
conformity continues to apply for the 1997 ozone NAAQS in orphan 
maintenance areas notwithstanding revocation of the 1997 ozone NAAQS.
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    \21\ South Coast Air Quality Management District v. EPA, 882 
F.3d 1138 (D.C. Cir. 2018) (``South Coast II''). The term ``South 
Coast II'' is used in reference to the 2018 court decision to 
distinguish it from a decision published in 2006 also referred to as 
``South Coast.'' The earlier decision involved a challenge to the 
EPA's Phase 1 implementation rule for the 1997 ozone NAAQS. South 
Coast Air Quality Management District v. EPA, 472 F.3d 882 (D.C. 
Cir. 2006).
    \22\ 80 FR 12264, 12284 (March 6, 2015).
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    Following the South Coast II decision, the EPA issued guidance that 
addresses how transportation conformity determinations can be made for 
the 1997 ozone NAAQS in orphan maintenance areas, such as the Clark 
County ozone maintenance area.\23\ In the guidance document, the EPA 
explains that transportation conformity for transportation plans and 
TIPs for the 1997 ozone NAAQS can be demonstrated without a regional 
emissions analysis pursuant to 40 CFR 93.109(c).\24\ In the case of the 
Clark County ozone maintenance area, while the transportation 
conformity requirement continues to apply for the revoked 1997 ozone 
NAAQS, RTC and DOT do not need to use the approved MOBILE6.2-based 
budgets from the 2011 Ozone Maintenance Plan in a conformity 
determination for the revoked 1997 ozone NAAQS because a regional 
emissions analysis is not required for that determination.
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    \23\ EPA, Office of Transportation and Air Quality, 
``Transportation Conformity Guidance for the South Coast II Court 
Decision,'' November 2018, EPA-420-B-18-050.
    \24\ Id., section 2.4.
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D. 2015 Ozone NAAQS and Clark County

    In 2015, the EPA further lowered the ozone NAAQS to 0.070 ppm, 
eight-hour average (herein the ``2015 ozone NAAQS'').\25\ In 2018, the 
EPA designated the Las Vegas Valley portion of Clark County as a 
``Marginal'' nonattainment area for the 2015 ozone NAAQS, effective 
August 3, 2018.\26\ The Clark County nonattainment area for the 2015 
ozone NAAQS is about half the size of the Clark County maintenance area 
for the 1997 ozone NAAQS and includes only hydrographic area 212 (``Las 
Vegas Valley'').
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    \25\ 80 FR 65292 (October 26, 2015) and 40 CFR 50.19.
    \26\ 83 FR 25776 (June 4, 2018).
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    The nonattainment area designation for Las Vegas Valley for the 
2015 ozone NAAQS triggers the requirement for certain SIP revisions, 
but, under CAA section 176(c)(6) and 40 CFR 93.102(d), transportation 
conformity does not apply for the 2015 ozone NAAQS for one year 
following the effective date of the nonattainment area designation 
(referred to as the ``grace period''), or, in this case, does not apply 
until August 3, 2019. However, to avoid a conformity ``lapse,'' a MPO 
and DOT must make a conformity determination for the 2015 ozone NAAQS 
for the applicable transportation plan and program before the end of 
the 1-year grace period.\27\
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    \27\ EPA, Office of Air Quality Planning and Standards, 
``Transportation Conformity Guidance for 2015 Ozone NAAQS 
Nonattainment Areas,'' June 2018, EPA-420-B-18-023. During a 
conformity lapse, only certain projects can receive additional 
federal funding or approvals to proceed (i.e., exempt projects, 
project phases that were approved before the lapse, and 
transportation control measures (TCMs) in approved SIPs) until the 
area has both a conforming transportation plan and TIP.
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    Under our Transportation Conformity Rule, the latest approved or 
adequate emission budgets for a previous ozone

[[Page 33039]]

NAAQS (i.e., the 2008 or the 1997 ozone NAAQS) must be used in 
conformity determinations for the 2015 ozone NAAQS until emission 
budgets are established and found adequate or are approved for the 2015 
ozone NAAQS.\28\ Since the latest approved or adequate emission budgets 
for a previous ozone NAAQS for Clark County are the approved MOBILE6.2-
based budgets for the 1997 8-hour ozone NAAQS, the RTC and DOT must use 
these budgets for conformity determinations for the 2015 ozone NAAQS 
until they are replaced by updated budgets.
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    \28\ 40 CFR 93.109(c)(2).
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E. The MOVES Emission Model

    The MOVES model is the EPA's tool for estimating highway emissions. 
The model is based on analyses of millions of emission test results and 
considerable advances in the agency's understanding of vehicle 
emissions. MOVES incorporates the latest emissions data, more 
sophisticated calculation algorithms, increased user flexibility, new 
software design, and significant new capabilities relative to those 
reflected in the EPA's previous motor vehicle emission factor model, 
MOBILE6.2.
    The EPA announced the release of MOVES2010 on March 2, 2010 (75 FR 
9411) and approved the use of MOVES2010 in states other than California 
for official SIP submissions to the EPA and for regional emissions 
analyses for transportation conformity purposes. The EPA released 
MOVES2014 on October 7, 2014 (79 FR 60343). MOVES2014 was a major 
revision to MOVES2010 and incorporated new emissions and fleet data, 
emission standards and functional improvements and features to the 
model. The October 7, 2014 notice approved the use of MOVES2014 in 
states outside of California for official SIP submissions to the EPA 
and for regional emissions analyses for transportation conformity 
purposes. In addition, the notice started a two-year grace period 
before MOVES2014 was required to be used in new regional emissions 
analyses for transportation conformity determinations outside of 
California. Since October 7, 2016, MOVES2014 was required to be used 
for new transportation conformity analyses outside California. In 
November 2015, the EPA released MOVES2014a, a minor update to 
MOVES2014.\29\
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    \29\ In August 2018, the EPA released MOVES2014b to improve 
estimates of emissions from nonroad mobile sources. MOBILE2014b does 
not significantly change the on-road criteria pollutant emissions 
results of MOVES2014 and is not considered a new model for SIP and 
transportation conformity purposes.
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III. What did the State submit?

    On October 31, 2018, NDEP submitted the 2018 Ozone Maintenance Plan 
Revision (for the 1997 ozone NAAQS) to the EPA as a revision to the 
Clark County portion of the Nevada SIP.\30\ Earlier that month, on 
October 16, 2018, the Clark County Board of County Commissioners 
adopted the 2018 Ozone Maintenance Plan Revision and forwarded the plan 
to NDEP for adoption and submittal to the EPA.\31\ The 2018 Ozone 
Maintenance Plan Revision updates certain elements of the 2011 Ozone 
Maintenance Plan for the 1997 ozone NAAQS, including the emissions 
inventories, the maintenance demonstration, and the MOBILE6.2-derived 
budgets. The 2018 Ozone Maintenance Plan Revision also includes a 
technical support document (appendix A of the plan revision) and 
documentation of the public review process (appendix B of the plan 
revision). These updated inventories and budgets in the 2018 Ozone 
Maintenance Plan Revision are based on MOVES2014a. The budgets for the 
1997 ozone NAAQS were developed so that the RTC would have updated 
budgets available to use for transportation conformity determinations 
with respect to the 2015 ozone NAAQS until budgets developed 
specifically for the 2015 ozone NAAQS are adopted and found to be 
adequate or approved.
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    \30\ Letter, Greg Lovato, Administrator, NDEP to Mike Stoker, 
Regional Administrator, EPA Region IX, October 31, 2018 with 
enclosures.
    \31\ Clark County Board of County Commissioners Meeting, Meeting 
Summary, pages 14 and 15 (of 19), October 16, 2018.
---------------------------------------------------------------------------

IV. Procedural Requirements for Adoption and Submittal of SIP Revisions

    CAA sections 110(a)(1) and (2) and 110(l) require a state to 
provide reasonable public notice and opportunity for public hearing 
prior to the adoption and submittal of a SIP or SIP revision. To meet 
this requirement, every SIP submittal should include evidence that 
adequate public notice was given and an opportunity for a public 
hearing was provided consistent with the EPA's implementing regulations 
in 40 CFR 51.102.
    The Clark County Board of County Commissioners and NDEP have 
satisfied applicable statutory and regulatory requirements for 
reasonable public notice and hearing prior to adoption and submittal of 
the 2018 Ozone Maintenance Plan Revision. In the documentation included 
as part of the October 31, 2018 SIP revision submittal,\32\ Clark 
County DAQ provided evidence of the required public notice and 
opportunity for public comment prior to the October 16, 2018 public 
hearing and adoption of the 2018 Ozone Maintenance Plan Revision. We 
find, therefore, that the submittal of the 2018 Ozone Maintenance Plan 
Revision meets the procedural requirements for public notice and 
hearing in CAA sections 110(a) and 110(l).
---------------------------------------------------------------------------

    \32\ Appendix B provides evidence that reasonable notice of a 
public hearing was provided to the public and that a public hearing 
was conducted prior to adoption. Specifically, notice of the 
availability of, and opening of a 30-day comment period on, the 
draft ozone maintenance plan revision was published on August 17, 
2018 on the County's web page. No comments were submitted.
---------------------------------------------------------------------------

    CAA section 110(k)(1)(B) requires the EPA to determine whether a 
SIP submittal is complete within 60 days of receipt. This section also 
provides that any plan submittal that the EPA has not affirmatively 
determined to be complete or incomplete will be deemed complete by 
operation of law six months after the date of submittal. The EPA's SIP 
completeness criteria are found in 40 CFR part 51, Appendix V. The 2018 
Ozone Maintenance Plan Revision submission, dated October 31, 2018, 
became complete by operation of law on April 30, 2019.

V. The EPA's Evaluation of the 2018 Ozone Maintenance Plan Revision

    The 2018 Ozone Maintenance Plan Revision is not a required 
submittal but has been submitted to establish revised budgets 
reflecting the most recent emissions models and planning estimates and 
to thereby provide the basis for RTC and DOT to make future 
transportation conformity determinations for transportation plans, TIPs 
and projects with respect to the 2015 ozone NAAQS. We have reviewed the 
2018 Ozone Maintenance Plan Revision for compliance with the relevant 
requirements for maintenance plans under CAA section 175A and for 
noninterference under CAA section 110(l), and we have evaluated the 
budgets in the 2018 Ozone Maintenance Plan Revision for compliance with 
the budget adequacy criteria in 40 CFR 93.118(e).
    CAA section 175A sets forth the elements of a maintenance plan for 
areas seeking redesignation from nonattainment to attainment. We 
interpret this section of the Act to require, in general, the following 
core elements: Attainment inventory, maintenance demonstration, 
monitoring network, verification of continued

[[Page 33040]]

attainment, and contingency plan.\33\ The 2018 Ozone Maintenance Plan 
Revision updates two of the core elements of the approved 2011 Ozone 
Maintenance Plan for the 1997 ozone NAAQS, the attainment inventory and 
maintenance demonstration, and it also updates the budgets.
---------------------------------------------------------------------------

    \33\ John Calcagni, Director, Air Quality Management Division, 
EPA Office of Air Quality Planning and Standards, memo titled 
``Procedures for Processing Requests to Redesignate Areas to 
Attainment,'' September 4, 1992.
---------------------------------------------------------------------------

    CAA section 110(l) applies to all SIP revisions, and under that 
section, the EPA shall not approve any SIP revision if the revision 
would interfere with any applicable requirement concerning attainment 
and reasonable further progress or any other applicable requirement of 
the CAA.

A. Revised Attainment Inventory

    A maintenance plan for the 1997 ozone NAAQS must include an 
inventory of emissions of ozone precursors (VOC and NOX) in 
the area to identify a level of emissions that are sufficient to attain 
the 1997 ozone NAAQS. This inventory must be consistent with the EPA's 
most recent guidance on emissions inventories for nonattainment areas 
available at the time and should represent emissions during the time 
period associated with the monitoring data showing attainment. The 
inventory must also be comprehensive, including emissions from 
stationary point sources, area sources, nonroad mobile sources, and on-
road mobile sources, and must be based on actual ``ozone season data'' 
(i.e., summertime) emissions.
    Clark County DAQ selected 2008 as the year for the attainment 
inventory in the 2011 Ozone Maintenance Plan. The attainment year 
inventory in the 2011 Ozone Maintenance Plan is comprehensive in that 
it includes estimates of summertime average weekday VOC and 
NOX emissions from all of the relevant source categories, 
which the plan divides among point sources,\34\ nonpoint sources,\35\ 
commercial aviation, federal aviation (i.e., Nellis Air Force Base), 
on-road mobile, nonroad mobile, and biogenic \36\ sources.\37\ The 2018 
Ozone Maintenance Plan Revision includes a comprehensive update to the 
2008 attainment inventory but, to the extent that the original 
estimates (i.e., from 2011 Ozone Maintenance Plan) are based on actual 
reported emissions or activity levels for year 2008, there is little 
change in the related emissions estimate. Appendix A to the 2018 Ozone 
Maintenance Plan Revision contains source-specific descriptions of 
emission calculation procedures and sources of input data used for the 
update.
---------------------------------------------------------------------------

    \34\ The 2018 Ozone Maintenance Plan Revision uses the term, 
``point sources,'' to refer to those stationary source facilities 
that are required to report their emissions to Clark County DAQ or 
NDEP.
    \35\ The 2018 Ozone Maintenance Plan Revision uses the term, 
``nonpoint sources,'' to refer to those stationary and area sources 
that fall below point source reporting levels and that are too 
numerous or small to identify individually.
    \36\ For the 2018 Ozone Maintenance Plan Revision, ``biogenic 
sources'' include agricultural crops; lawn grass; forests that 
produce isoprene, monoterpene, alpha-pinene, and other VOC 
emissions; and soils that generate trace amounts of NOX.
    \37\ See Table 2-1 in the 2018 Ozone Maintenance Plan Revision.
---------------------------------------------------------------------------

    Table 2 below compares the attainment inventory from the 2011 Ozone 
Maintenance Plan with the corresponding inventory from the 2018 Ozone 
Maintenance Plan Revision. As shown in Table 2, the change in the 
attainment inventory in the 2018 Ozone Maintenance Revision is 
primarily due to the update to the on-road mobile source category and 
the nonpoint source category.

                                       Table 2--2008 Attainment Inventory
                                       [Average summer weekday, tons/day]
----------------------------------------------------------------------------------------------------------------
                                                           NOX emissions                   VOC emissions
                                                 ---------------------------------------------------------------
                 Source category                    2011 Ozone      2018 Ozone      2011 Ozone      2018 Ozone
                                                    Maintenance     Maintenance     Maintenance     Maintenance
                                                       Plan        Plan Revision       Plan        Plan Revision
----------------------------------------------------------------------------------------------------------------
Point source....................................           28.73           28.97            1.32            1.50
Nonpoint source.................................            5.41             6.6           57.07           67.56
Commercial aviation.............................           11.41           11.41            2.60            2.60
Federal aviation................................            1.27            1.27            0.79            0.79
On-road mobile..................................           68.46           89.50           65.08           42.46
Nonroad mobile..................................           43.28           40.63           42.91           42.07
Biogenic........................................            5.00            5.00          132.00          132.00
                                                 ---------------------------------------------------------------
    Total.......................................          163.56          183.38          301.77          288.98
----------------------------------------------------------------------------------------------------------------
Sources: 2011 Ozone Maintenance Plan, tables 6-2 and 6-3; 2018 Ozone Maintenance Plan Revision, table 2-1.

    With respect to on-road mobile source emissions, Clark County DAQ 
updated the emissions estimates using the SMOKE-MOVES approach, which 
incorporates MOVES2014a model emission rates, Sparse Matrix Operator 
Kernel Emissions (SMOKE) modeling,\38\ RTC travel demand modeling, and 
Highway Performance Monitoring System (HPMS) data from the Nevada 
Department of Transportation.\39\ Clark County DAQ selected the SMOKE-
MOVES approach to be consistent with the EPA's approach in developing 
the National Emissions Inventory (NEI), as well as with the EPA's 
modeling platform. This approach is also consistent with the one used 
in Clark County's photochemical modeling applications. In contrast, the 
2011 Ozone Maintenance Plan's on-road mobile source emissions were 
estimated using the CONCEPT MV emissions model \40\ and EPA's MOBILE6.2 
emissions factors. Generally, on-road mobile source emissions estimates 
made using MOVES2014a are higher for NOX

[[Page 33041]]

and lower for VOC relative to those made using MOBILE6.2. With respect 
to nonpoint emissions sources, the change in the 2008 emissions 
inventory is largely due to the use of the SMOKE model.
---------------------------------------------------------------------------

    \38\ SMOKE is an emission-generating and processing model used 
in developing hourly gridded emissions for photochemical modeling. 
The EPA has integrated the MOVES model with the SMOKE model with a 
set of integration software tools that allows the MOVES emission 
rate model to automatically run numerous iterations to generate the 
most accurate modeling results. The SMOKE-MOVES integrated approach 
takes advantage of gridded hourly temperature and humidity 
information from the Weather Research and Forecasting (WRF) 
meteorology model used for air quality modeling.
    \39\ 2018 Ozone Maintenance Plan Revision, Appendix A, page A-2.
    \40\ ``CONCEPT'' refers to the CONsolidated Community Emissions 
Processor Tool (CONCEPT) and ``MV'' refers to the motor vehicle 
module of the CONCEPT model.
---------------------------------------------------------------------------

    Based on our review of the emissions inventories (and related 
documentation) from the 2018 Ozone Maintenance Plan Revision, we find 
that the inventories for 2008 are comprehensive, that the methods and 
assumptions used by Clark County DAQ to update the 2008 emission 
inventory are reasonable, and that the inventories reasonably estimate 
actual ozone season emissions in the 2008 attainment year. Moreover, we 
find that the 2008 emissions inventories in the Ozone Maintenance Plan 
reflect the latest planning assumptions and emissions models available 
at the time the 2018 Ozone Maintenance Plan Revision was developed.

B. Revised 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 
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.
    The 2018 Ozone Maintenance Plan Revision uses the same method as 
the 2011 Ozone Maintenance Plan to demonstrate continued maintenance of 
the 1997 ozone NAAQS. The 2018 Ozone Maintenance Plan Revision 
demonstrates maintenance through the initial 10-year period after 
redesignation by showing that emissions in 2015 and 2022 would be less 
than those in the 2008 attainment year.
    To provide the basis for the comparison of future emissions with 
the updated attainment year (2008) emissions, Clark County DAQ updated 
the 2015 and 2022 emissions inventories using the SMOKE-MOVES approach 
for the on-road mobile sources as described above for the update to the 
2008 attainment year emissions inventory and by incorporating more 
recent emissions and travel demand data. Tables 3 and 4 below compare 
the NOX and VOC emissions inventories, respectively, for 
2015 and 2022 from the 2018 Ozone Maintenance Plan Revision with the 
corresponding values from the 2011 Ozone Maintenance Plan.

                  Table 3--Comparison of NOX Inventories Associated With Approved and Revised Maintenance Plan for the 1997 Ozone NAAQS
                                                            [Tons per average summer weekday]
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                           2011 Ozone  Maintenance Plan    2018 Ozone  Maintenance Plan           Net  change \b\
                                                                        \a\                          Revision            -------------------------------
                     Source category                     ----------------------------------------------------------------
                                                               2015            2022            2015            2022            2015            2022
--------------------------------------------------------------------------------------------------------------------------------------------------------
Stationary and Area (point and nonpoint)................              37              38              18              17             -19             -21
On-road.................................................              35              23              64              27             +29              +4
Nonroad (including aviation)............................              47              51              41              37              -6             -14
Biogenic................................................               5               5               5               5               0               0
Emission Reduction Credits..............................              22              22              22              22               0               0
                                                         -----------------------------------------------------------------------------------------------
    Totals \c\..........................................             146             139             150             109              +4             -30
--------------------------------------------------------------------------------------------------------------------------------------------------------
\a\ The emissions shown for the approved ozone plan are from Table 6-3 of Clark County's 2011 Ozone Maintenance Plan.
\b\ For the net change, a negative number indicates a reduction in emissions, and a positive number indicates an increase in emissions relative to the
  corresponding figure in the 2011 Ozone Maintenance Plan.
\c\ Because of rounding conventions, totals may not reflect individual subcategories.

                  Table 4--Comparison of VOC Inventories Associated With Approved and Revised Maintenance Plan for the 1997 Ozone NAAQS
                                                            [Tons per average summer weekday]
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                           2011 Ozone  Maintenance Plan    2018 Ozone  Maintenance Plan           Net  change \b\
                                                                        \a\                          Revision            -------------------------------
                     Source category                     ----------------------------------------------------------------
                                                               2015            2022            2015            2022            2015            2022
--------------------------------------------------------------------------------------------------------------------------------------------------------
Stationary and Area (point and nonpoint)................              68              78              63              62              -5             -16
On-road.................................................              45              37              33              17             -12             -20
Nonroad (including aviation)............................              36              35              35              32              -1              -3
Biogenic................................................             132             132             132             132               0               0
Emission Reduction Credits..............................              <1              <1              <1              <1               0               0
                                                         -----------------------------------------------------------------------------------------------
    Totals \c\..........................................             282             282             263             244             -19             -38
--------------------------------------------------------------------------------------------------------------------------------------------------------
\a\ The emissions shown for the approved ozone plan are from Table 6-3 of Clark County's 2011 Ozone Maintenance Plan.
\b\ For the net change, a negative number indicates a reduction in emissions, and a positive number indicates an increase in emissions relative to the
  corresponding figure in the 2011 Ozone Maintenance Plan.
\c\ Because of rounding conventions, totals may not reflect individual subcategories.

[[Page 33042]]

    As shown in tables 3 and 4, total emissions for 2015 and 2022 in 
the 2018 Ozone Maintenance Plan Revision are lower than the 
corresponding emissions in the 2011 Ozone Maintenance Plan with the 
exception of a 4 tpd higher estimate in 2015 for NOX. With 
respect to the on-road mobile sources, the update results in higher 
NOX emissions but lower VOC emissions and reflects primarily 
the differences in the emissions rates calculated using MOVES2014a 
relative to those calculated using MOBILE6.2. The on-road mobile source 
emission estimates in the 2018 Ozone Maintenance Plan Revision reflect 
the most recent published data concerning vehicle registration data, 
vehicle miles traveled (VMT) temporal distribution, VMT mix profiles, 
vehicle speeds and travel demand forecasts from RTC.\41\ The higher 
estimates for NOX from on-road mobile sources are offset by 
decreases in the actual reported emissions for point source emissions 
compared to their projected emissions in the 2011 Ozone Maintenance 
Plan (which includes the shutdown of the Reid Gardner coal-fired power 
plant). Other significant differences include: (1) A reduction in 
commercial aviation emissions because the Sloan Regional Heliport and 
South County Ivanpah Airport projects, which had been assumed for the 
2011 Ozone Maintenance Plan, have not been constructed and (2) 
reductions in nonpoint source emission projection factors.\42\
---------------------------------------------------------------------------

    \41\ Key references used by Clark County DAQ include Eastern 
Research Group, Inc.'s ``Clark County On-Road Vehicle Classification 
Study,'' final report, June 29, 2018 and the Coordinating Research 
Council, Inc.'s ``Improvement of Default Inputs for MOVES and SMOKE-
MOVES,'' final report, February 2017.
    \42\ Clark County projected emissions from 2014 NEI data with 
factors derived from the 2011-2023 annual rate of change for all 
nonpoint sectors from EPA's 2011 Version 6 Air Emissions Modeling 
Platform. Nonpoint source emissions in the 2011 Ozone Maintenance 
Plan were based on the 2008 NEI and higher growth correlated to 
population and economic growth factors.
---------------------------------------------------------------------------

    Based on our review of the methods, assumptions, and data sources, 
as described in Appendix A to the 2018 Ozone Maintenance Plan Revision, 
and briefly summarized above, we find that Clark County DAQ's estimates 
for 2015 and 2022 for the various source categories to be based on the 
best available emissions models and data sources, and thus to provide a 
reasonable basis upon which to evaluate whether the area will maintain 
the 1997 ozone NAAQS through 2022.
    A state may choose to allocate all or a portion of the safety 
margin \43\ under our transportation conformity rule so long as such 
margins are explicitly quantified in the applicable plan and are shown 
to be consistent with attainment or maintenance of the NAAQS (whichever 
is relevant to the particular plan).\44\ For the 2018 Ozone Maintenance 
Plan Revision, Clark County DAQ allocated 80 percent of the safety 
margin for NOX and VOC in 2015 and 2022 to the projected on-
road emissions estimates for NOX and VOC.
---------------------------------------------------------------------------

    \43\ In this context, ``safety margin'' means the amount by 
which the total projected emissions from all sources of a given 
pollutant are less than the total emissions that would satisfy the 
applicable requirements for reasonable further progress, attainment 
or maintenance. With respect to the 2018 Ozone Maintenance Plan 
Revision, the safety margin is the difference between the projected 
emissions in 2015 and 2022 of NOX and VOC and the actual 
emissions of NOX and VOC in the 2008 attainment year.
    \44\ See 40 CFR 93.124(a).
---------------------------------------------------------------------------

    Table 5 below summarizes the revised maintenance demonstration 
(including the safety margins) for the 1997 ozone NAAQS. As shown in 
Table 5, the revised emission estimates for NOX and VOC in 
2015 and 2022 (including the safety margins) would remain below the 
corresponding 2008 attainment levels throughout the 10-year maintenance 
period and thereby adequately demonstrate maintenance through that 
period.

                         Table 5--Revised Maintenance Demonstration for 1997 Ozone NAAQS
----------------------------------------------------------------------------------------------------------------
                                                            Emissions  (average summer weekday, tpd)
                                               -----------------------------------------------------------------
              Source description                 Attainment  (2008)           2015                  2022
                                               -----------------------------------------------------------------
                                                   NOX        VOC        NOX        VOC        NOX        VOC
----------------------------------------------------------------------------------------------------------------
Projected Emissions--Excluding On-Road Mobile       93.88     246.52      85.81     229.82      81.71     227.06
 Sources......................................
Projected On-Road Mobile Source Emissions.....      89.50      42.46      64.30      33.04      27.02      17.12
Allocation of Portion of Safety Margin to On-           0          0      26.62      20.90      59.72      35.84
 Road.........................................
Total Emissions (with Safety Margins).........     183.38     288.98     176.73     283.76     168.45     280.02
Maintenance Demonstrated?.....................  .........  .........        Yes        Yes        Yes        Yes
Motor Vehicle Emissions Budget (Projected On-       89.50      42.46      90.92      53.94      86.74      52.96
 Road Plus Safety Margin).....................
----------------------------------------------------------------------------------------------------------------
Source: 2018 Ozone Maintenance Plan Revision, Tables 2-1, 2-2 and 3-1. Note: Maintenance is demonstrated where
  future emissions (with the safety margins) are less than the corresponding attainment inventory emissions.

C. Revised Motor Vehicle Emissions Budgets

    Section 176(c) of the CAA requires federal actions in nonattainment 
and maintenance areas to conform to the SIP's goals of eliminating or 
reducing the severity and number of violations of the NAAQS and 
achieving timely attainment of the standards. Conformity to the SIP's 
goals means that such actions will not: (1) Cause or contribute to 
violations of a NAAQS, (2) worsen the severity of an existing 
violation, or (3) delay timely attainment of any NAAQS or any interim 
milestone.
    Under the transportation conformity rule, MPOs in nonattainment and 
maintenance areas coordinate with state and local air quality and 
transportation agencies, the EPA, the FHWA, and the FTA to demonstrate 
that an area's regional transportation plans and TIPs conform to the 
applicable SIP. This demonstration is typically done by showing that 
estimated emissions from existing and planned highway and transit 
systems are less than or equal to the budgets contained in all control 
strategy or maintenance SIPs. Budgets are generally established for 
specific years and specific pollutants or precursors. Maintenance ozone 
plans should identify budgets for on-road emissions of ozone precursors 
(NOX and VOC) in the area for the last year of the 
maintenance period. Budgets may also be specified for additional years 
during the maintenance period.
    For budgets to be approvable, they must meet the EPA's adequacy 
criteria (40 CFR 93.118(e)(4) and (5)) and comply with all pertinent 
SIP requirements. With respect to maintenance plans, to meet these 
requirements, the budgets must be consistent with the maintenance plan 
and reflect all the motor vehicle control measures contained in the 
maintenance

[[Page 33043]]

demonstration.\45\ The EPA's process for determining adequacy of a 
budget consists of three basic steps: (1) Providing public notification 
of a SIP submission; (2) providing the public the opportunity to 
comment on the budget during a public comment period; and, (3) making a 
finding of adequacy or inadequacy.\46\ We will complete the adequacy 
review of the budgets in the 2018 Ozone Maintenance Plan Revision 
concurrent with our final action on the 2018 Ozone Maintenance Plan 
Revision. The EPA is not required under its transportation conformity 
rule to find budgets adequate prior to proposing approval of them.\47\
---------------------------------------------------------------------------

    \45\ 40 CFR 93.118(e)(4)(iii), (iv) and (v). For more 
information on the transportation conformity requirements and 
applicable policies on budgets, please visit our transportation 
conformity website at: http://www.epa.gov/otaq/stateresources/transconf/index.htm.
    \46\ 40 CFR 93.118(f)(2).
    \47\ Under the transportation conformity regulations, the EPA 
may review the adequacy of submitted motor vehicle emission budgets 
simultaneously with the EPA's approval or disapproval of the 
submitted implementation plan. 40 CFR 93.118(f)(2).
---------------------------------------------------------------------------

    The 2018 Ozone Maintenance Plan Revision includes revised budgets 
for VOC and NOX for years 2008, 2015 and the last year of 
the initial maintenance period, i.e., 2022. The revised budgets from 
the 2018 Ozone Maintenance Plan Revision are shown in Table 6 below and 
compared with the corresponding budgets from the approved 2011 Ozone 
Maintenance Plan. As noted previously, Clark County DAQ developed the 
revised budgets using the latest emissions model (MOVES2014a) available 
at the time the 2018 Ozone Maintenance Plan Revision was being 
developed, and the most recent travel activity projections provided by 
the NDOT and RTC. As such, we find that the revised budgets reflect the 
most recent planning forecasts and are based on the most recent 
emission factor data and approved calculation methods. Clark County DAQ 
included 80% of the safety margin in the budgets. In this context, the 
term ``safety margin'' refers to the difference between the updated 
emissions inventories in the 2018 Ozone Maintenance Plan Revision for 
years 2015 and 2022 and the updated attainment (2008) emissions 
inventory in the plan revision.

                                  Table 6--Ozone Motor Vehicle Emission Budgets
                                       [Average summer weekday, tons/day]
----------------------------------------------------------------------------------------------------------------
                                                    2011 Ozone Maintenance Plan     2018 Ozone Maintenance Plan
                                                 --------------------------------            Revision
                      Year                                                       -------------------------------
                                                        NOX             VOC             NOX             VOC
----------------------------------------------------------------------------------------------------------------
2008............................................           68.46           65.08           89.50           42.46
2015............................................           34.69           45.32           90.92           53.94
2022............................................           23.15           36.71           86.74           52.96
----------------------------------------------------------------------------------------------------------------
Sources: 2011 Ozone Maintenance Plan, Table 7-1; 2018 Ozone Maintenance Plan Revision, Table 3-1.

    As documented in a May 22, 2019 memorandum to the docket for this 
rulemaking, we find that the budgets in the 2018 Ozone Maintenance Plan 
Revision meet each adequacy criterion.\48\ We have completed our 
detailed review of the 2018 Ozone Maintenance Plan Revision and find 
them acceptable. We have also reviewed the budgets in the 2018 Ozone 
Maintenance Plan Revision and found that they are consistent with the 
revised maintenance demonstration; are based on control measures that 
have already been adopted and implemented; and meet all other 
applicable statutory and regulatory requirements including the adequacy 
criteria in 40 CFR 93.1118(e)(4) and (5). Therefore, we are proposing 
to find adequate and conditionally approve the 2008, 2015 and 2022 
budgets in the 2018 Ozone Maintenance Plan Revision. If we finalize our 
adequacy determination and conditional approval of the revised budgets 
in the 2018 Ozone Maintenance Plan Revision, as proposed, they will 
replace the budgets for the 1997 ozone NAAQS from the 2011 Ozone 
Maintenance Plan that we previously found adequate and approved for use 
in transportation conformity determinations. The proposed approval of 
the budgets is conditional because it is based on commitments by NDEP 
and Clark County DAQ to submit a SIP revision within one year of final 
conditional approval to reduce the safety margin allocations to avoid 
interference with reasonable further progress or attainment of the 2008 
and 2015 ozone NAAQS. For more information on why the reduction of the 
safety margin is needed, see the following section of this notice.
---------------------------------------------------------------------------

    \48\ Memorandum from Karina O'Connor, Air Planning Office, EPA 
Region IX, to Air Plan Approval; Revisions to the Clark County Ozone 
Maintenance Plan, dated May 22, 2019.
---------------------------------------------------------------------------

D. CAA Section 110(l) Evaluation

    In relevant part, CAA section 110(l) provides that the EPA shall 
not approve a SIP revision that would interfere with any applicable 
requirement concerning attainment or RFP of any of the NAAQS or any 
other applicable requirement of the CAA. The 2018 Ozone Maintenance 
Plan Revision would establish budgets that are larger than those that 
are currently approved from the 2011 Ozone Maintenance Plan. Thus, 
approval of the 2018 Ozone Maintenance Plan Revision would accommodate 
a higher level of VOC and NOX emissions from on-road mobile 
source emissions than would otherwise be allowed under the existing 
budgets. In the following paragraphs, we evaluate the higher level of 
VOC and NOX emissions with respect to the potential for 
interference with RFP and attainment of the NAAQS for which VOC and 
NOX are precursors, namely, the 2008 and 2015 ozone NAAQS 
and the 2006 and 2012 PM2.5 NAAQS.\49\
---------------------------------------------------------------------------

    \49\ As a general matter, NOX is also considered a 
precursor for PM10. However, in approving the Las Vegas 
Valley Serious Area PM10 Plan, the EPA determined that 
major stationary sources of PM10 precursors do not 
contribute significantly to elevated ambient PM10 
concentrations in Las Vegas Valley. 69 FR 32273 (June 9, 2004). 
Moreover, the approved Las Vegas Valley PM10 Maintenance 
Plan relies on direct PM10 control measures (rather than 
PM10 precursor controls) to demonstrate maintenance of 
the PM10 NAAQS within Las Vegas Valley. 79 FR 42258 (July 
21, 2014) (proposed PM10 redesignation and approval of 
related maintenance plan) and 79 FR 60078 (October 6, 2014) (final 
PM10 redesignation and approval of related maintenance 
plan).
---------------------------------------------------------------------------

    2008 Ozone NAAQS. In 2012, the EPA designated all the hydrographic 
areas within the State of Nevada as unclassifiable/attainment for the 
0.075 ppm 2008 ozone NAAQS based on ambient ozone concentration data 
for

[[Page 33044]]

years 2009-2011.\50\ After the original designation, the 8-hour ozone 
design values within Clark County exceeded the 2008 ozone NAAQS for a 
few years but, since 2015, the design values have returned to 
attainment levels for the 2008 ozone NAAQS. See Table 1 above. Thus, 
emissions of VOC and NOX in 2015 represent conditions under 
which Clark County meets the 2008 ozone NAAQS. As updated in the 2018 
Ozone Maintenance Plan Revision, summertime weekday average emissions 
in 2015 were approximately 262 tpd of VOC and 128 tpd of 
NOX.\51\ Including the safety margin allocations to the on-
road emissions estimates, the 2018 Ozone Maintenance Plan Revision 
allows for 280 tpd of VOC and 168 tpd of NOX emissions in 
2022, i.e., a higher level of VOC and NOX emissions than is 
consistent with continued attainment of the 2008 ozone NAAQS.
---------------------------------------------------------------------------

    \50\ Letter from Jared Blumenfeld, Regional Administrator, EPA 
Region IX, to Brian Sandoval, Governor, State of Nevada, dated 
December 9, 2011.
    \51\ Assumes that no emission reduction credits (ERCs) were used 
in 2015.
---------------------------------------------------------------------------

    However, in recognition of the need to avoid interference with 
attainment of the 2008 ozone NAAQS and progress toward attainment of 
the 2015 ozone NAAQS, NDEP and Clark County DAQ have committed to 
submit a SIP revision to remove the safety margin allocations to the 
2015 budgets and to reduce the safety margin allocations to the 2022 
budgets such that total estimated emission in 2022 (with the 
allocations) would not exceed actual emissions in year 2017. As shown 
in Table 1 above, the design value in year 2017 was 0.074 ppm, which is 
consistent with attainment of the 0.075 ppm 2008 ozone NAAQS.
    Based on the commitments by NDEP and Clark County DAQ, the total 
projected emissions (with the reduced safety margin allocations) in 
year 2022 would be less than the actual emissions estimated for year 
2017, a year in which the 2008 ozone NAAQS was attained in Clark 
County. Therefore, the 2018 Ozone Maintenance Plan, as revised 
consistent with NDEP's and Clark County DAQ's commitments, would not 
interfere with attainment of the 2008 ozone NAAQS in Clark County.
    2015 Ozone NAAQS. In 2018, the EPA designated the Las Vegas Valley 
(i.e., hydrographic area #212) as a Marginal nonattainment area for the 
0.070 ppm 2015 ozone NAAQS based on ambient ozone concentration data 
for years 2015-2017.\52\ The 2017 ozone design value is 0.074 ppm, and 
VOC and NOX emissions in 2017 are estimated (based on 
interpolating the 2015 and 2022 updated inventories in the 2018 Ozone 
Maintenance Plan Revision) to be approximately 257 tpd and 116 tpd, 
respectively.\53\ To attain the 0.070 ppm 2015 ozone NAAQS by the 
applicable Marginal area attainment date, i.e., by August 3, 2021, VOC 
and NOX emissions must decrease relative to those in 2017. 
With the allocation of the safety margin to the on-road emissions 
estimates, the 2018 Ozone Maintenance Plan Revision would allow for VOC 
and NOX emissions that are greater than those in 2017.
---------------------------------------------------------------------------

    \52\ EPA, ``Nevada, Las Vegas Nonattainment Area, Final Area 
Designations for the 2015 Ozone National Ambient Air Quality 
Standards, Technical Support Document (TSD).''
    \53\ Assumes that no ERCs were used in 2017.
---------------------------------------------------------------------------

    However, based on the commitments by NDEP and Clark County DAQ 
described above for the 2008 ozone NAAQS, the total projected emissions 
(with the reduced safety margin allocations) in year 2022 would be less 
than the actual emissions estimated for year 2017, the base year for 
implementation of the 2015 ozone NAAQS. Therefore, the 2018 Ozone 
Maintenance Plan, as revised consistent with NDEP's and Clark County 
DAQ's commitments, would not interfere with RFP towards attainment of 
the 2015 ozone NAAQS.
    2006 and 2012 PM2.5 NAAQS. The EPA has designated the State of 
Nevada, on a hydrographic area basis, as unclassifiable/attainment for 
both the 35 [micro]g/m\3\, 24-hour average, 2006 PM2.5 NAAQS 
and the 12.0 [micro]g/m\3\, annual average, 2012 PM2.5 
NAAQS.\54\ The design values for 24-hour average PM2.5 
concentrations have ranged from 19 to 26 [micro]g/m\3\ over the 2008-
2017 period, well below the corresponding NAAQS of 35 [micro]g/
m\3\.\55\ With respect to annual average PM2.5 
concentrations, the design values have ranged from 7.7 to 10.3 
[micro]g/m\3\ over that same period, i.e., well below the corresponding 
NAAQS of 12.0 [micro]g/m\3\.\56\ Thus, since at least 2008, ambient 
PM2.5 concentrations have been well within the applicable 
NAAQS, and given that the VOC and NOX emissions that would 
be allowed under the 2018 Ozone Maintenance Plan Revision (including 
the safety margin allocations to on-road emissions) would be less than 
those that occurred in 2008, approval of the 2018 Ozone Maintenance 
Plan Revision would not interfere with attainment of the 2006 or 2012 
PM2.5 NAAQS in Clark County.
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    \54\ 40 CFR 81.329.
    \55\ 2017 PM2.5 Design Values Report at https://www.epa.gov/air-trends/air-quality-design-values#report. The 24-hour 
PM2.5 NAAQS design value is the 3-year average of annual 
98th percentile 24-hour average values recorded at each monitoring 
site, and the 24-hour PM2.5 design value for the area is 
the highest design value among the monitoring sites.
    \56\ Id. The annual PM2.5 NAAQS design value is the 
3-year average of annual mean concentrations recorded at each 
monitoring site, and the annual PM2.5 design value for 
the area is the highest design value among the monitoring sites.
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VI. Proposed Action and Request for Public Comment

    For the reasons discussed above, under CAA section 110(k)(4), the 
EPA is proposing to conditionally approve the 2018 Ozone Maintenance 
Plan Revision submitted by NDEP on October 31, 2018 as a revision for 
the Clark County portion of the Nevada SIP. In so proposing, we find 
that the 2011 Ozone Maintenance Plan, as revised by the updated 
attainment inventory and maintenance demonstration in the 2018 Ozone 
Maintenance Plan Revision, continues to provide for maintenance of the 
1997 ozone NAAQS and, upon fulfillment of the commitments made by NDEP 
and Clark County DAQ to reduce the safety margin allocations to the 
budgets, will not interfere with RFP or attainment of the other NAAQS 
in Clark County. In proposing conditional approval of the 2018 Ozone 
Maintenance Plan Revision, the EPA is also proposing to find adequate 
and conditionally approve the updated budgets for 2008, 2015 and 2022 
for the 1997 ozone NAAQS (shown in Table 6 of this document) based on 
our conclusion that the updated budgets meet the applicable 
transportation conformity requirements.
    The proposed approval of the 2018 Ozone Maintenance Plan Revision 
is conditional because it is based on commitments from NDEP and the 
Clark County DAQ to submit a SIP revision within one year of final 
conditional approval.\57\ The purpose of the future SIP revision is to 
reduce the safety margin allocations to the budgets to ensure that the 
2018 Ozone Maintenance Plan Revision, as revised to reduce the safety 
margin allocations, will not interfere with reasonable further progress 
or attainment of the 2008 and 2015 ozone NAAQS.
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    \57\ Letter from Jodi Bechtel, Assistant Director, Clark County 
DAQ, to Greg Lovato, Administrator, NDEP, dated June 14, 2019; and 
letter from Greg Lovato, Administrator, NDEP, to Elizabeth Adams, 
Director, Air Division, EPA Region IX, dated June 21, 2019.
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    Lastly, if the EPA takes final action to approve conditionally the 
2018 Ozone Maintenance Plan Revision as proposed, the revised budgets 
will replace the existing approved budgets from the 2011 Ozone 
Maintenance Plan, and RTC and DOT must use the revised budgets for 
future transportation conformity determinations.

[[Page 33045]]

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

VII. Statutory and Executive Order Reviews

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

List of Subjects in 40 CFR Part 52

    Environmental protection, Air pollution control, Incorporation by 
reference, Intergovernmental regulations, Nitrogen dioxide, Ozone, 
Reporting and recordkeeping requirements, Volatile organic compounds.

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

    Dated: June 27, 2019.
Deborah Jordan,
Acting Regional Administrator, EPA Region IX.
[FR Doc. 2019-14630 Filed 7-10-19; 8:45 am]
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