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Federal Register / Vol. 86, No. 150 / Monday, August 9, 2021 / Proposed Rules C. Transportation Conformity and the TABLE 1EIGHT-HOUR OZONE DESIGN VALUES FOR THE CLARK 2018 Ozone Maintenance Plan Revision COUNTY
OZONE
MAINTENANCE
The EPAs transportation conformity rule at 40 CFR part 93, subpart A
AREA, 20082020
establishes the criteria and procedures that metropolitan planning Year organizations MPOs and the U.S.
Department of Transportation DOT
2008
0.082 must use to determine whether 2009
0.078 transportation activities conform to the 2010
0.076 SIP. Transportation conformity applies 2011
0.075 to areas that are designated 2012
0.076 nonattainment and those former 2013
0.077 nonattainment areas that have been 2014
0.078 redesignated to attainment and have a 2015
0.075 CAA section 175A maintenance plan 2016
0.075 maintenance areas, but does not 2017
0.074
apply to areas designated as attainment 2018
0.076
17
2019
0.073 or unclassifiable. In Clark County, the areas MPO, the Regional Transportation 2020
0.074
Commission of Southern Nevada RTC, Source: The EPAs 2017 and 2020 Ozone and DOT are the relevant transportation Design Values Reports at https
agencies that must determine the www.epa.gov/air-trends/air-quality-design-valuesreport. Note that design values reported conformity of transportation plans and for a given year reflect data from that year and transportation improvement plans the two previous years, e.g., the design value TIPs within Clark County.
for 2008 reflects data from 20062008.
Under our transportation conformity rule, the latest approved or adequate B. 2008 and 2015 Ozone NAAQS
emissions budgets for a previous ozone In 2008, the EPA lowered the ozone NAAQS i.e., the 2008 or the 1997 ozone NAAQS to a level of 0.075 ppm, 8-hour NAAQS must be used in conformity average herein, the 2008 ozone determinations for the 2015 ozone NAAQS,13 and in 2012, the EPA
NAAQS until emission budgets are designated all of the hydrographic areas established and found adequate or are within the State of Nevada as approved for the 2015 ozone NAAQS.
Unclassifiable/Attainment for the Because the latest approved or adequate 2008 ozone NAAQS.14 Because all the emissions budgets for a previous ozone hydrographic areas located entirely, or NAAQS for Clark County are the partially, within Clark County were approved budgets for the 1997 8-hour designated as unclassifiable/attainment ozone NAAQS, the RTC and DOT must for the 2008 ozone NAAQS, no use these budgets for conformity reasonable further progress RFP or determinations for the 2015 ozone attainment SIP revision was required for NAAQS 18 until they are replaced by any portion of the county.
updated budgets for the 2015 ozone In 2015, the EPA further lowered the NAAQS.
ozone NAAQS to 0.070 ppm, 8-hour In 2018, NDEP submitted the 2018
average herein the 2015 ozone Ozone Maintenance Plan Revision as a NAAQS.15 In 2018, the EPA
revision to the Clark County portion of designated the Las Vegas Valley portion the Nevada SIP. The 2018 Ozone of Clark County as a Marginal Maintenance Plan Revision includes nonattainment area for the 2015 ozone revisions to the attainment inventory, NAAQS, effective August 3, 2018.16 The the maintenance demonstration, and nonattainment area designation for Las budgets in the 2011 Ozone Maintenance Vegas Valley for the 2015 ozone NAAQS Plan to reflect updated emissions triggered the requirement for certain SIP models, vehicle mix and speed data, revisions under CAA section 182a and and transportation activity projections.
the EPAs related SIP Requirements The 2018 Ozone Maintenance Plan Rule promulgated at 40 CFR part 51, Revision revised the budgets for NOX
subpart CC.
and VOC for years 2008, 2015, and 2022. The revised budgets were derived lotter on DSK11XQN23PROD with PROPOSALS1

Design value ppm
13 73 FR 16436 March 27, 2008 and 40 CFR
50.15.
14 77 FR 30088 May 21, 2012. Hydrographic areas are those that are shown on the State of Nevada Division of Water Resources map titled Water Resources and Inter-basin Flows September 1971.
15 80 FR 65292 October 26, 2015 and 40 CFR
50.19.
16 83 FR 25776 June 4, 2018.

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17 CAA

section 176c5.
18 The EPAs guidance Transportation Conformity Guidance for the South Coast II Court Decision November 2018, EPA20B18050, explains that while conformity requirements continue to apply for the revoked 1997 ozone NAAQS, conformity can be demonstrated without a regional emissions analysis for the 1997 ozone standard.

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from the on-road motor vehicle emissions estimates prepared using the most recent version of the EPAs onroad vehicle emissions model available at the time MOVES2014a and updated planning variables e.g., vehicle miles traveled projections and population forecasts from the RTC. The 2018
Ozone Maintenance Plan Revision was developed so that the RTC and DOT
would have updated budgets available to use for transportation conformity determinations with respect to the 2015
ozone NAAQS until budgets developed specifically for the 2015 ozone NAAQS
are adopted and found to be adequate or approved. In 2019, the EPA
conditionally approved the 2018 Ozone Maintenance Plan Revision as a revision of the Clark County portion of the Nevada SIP.19
In so doing, we found that the 2011
Ozone Maintenance Plan, as revised by the updated attainment inventory and maintenance demonstration in the 2018
Ozone Maintenance Plan Revision, continues to provide for maintenance of the 1997 ozone NAAQS, and upon fulfillment of the commitments made by NDEP and Clark County DES to reduce the safety margin allocations for the budgets, will not interfere with RFP or attainment of the other NAAQS in Clark County. In conditionally approving the 2018 Ozone Maintenance Plan Revision, the EPA also found adequate and conditionally approved the updated NOX and VOC budgets for 2008, 2015, and 2022 for the 1997 ozone NAAQS
based on our conclusion that the updated budgets meet the applicable transportation conformity requirements.
The approval was conditional because it is based on commitments by Clark County DES and NDEP to submit an additional SIP revision to reduce the safety margin allocations for the budgets in the 2018 Ozone Maintenance Plan Revision within one year of this final conditional approval.
In September 2020, NDEP submitted the 2020 Ozone Maintenance Plan Revision to the EPA in fulfillment of the commitments made by Clark County DES and NDEP in connection with the EPAs conditional approval of the 2018
Ozone Maintenance Plan Revision. The 2020 Ozone Maintenance Plan Revision is the subject to todays proposed action.
III. What did the State submit?
On August 18, 2020, the Clark County Board of County Commissioners adopted the 2020 Ozone Maintenance Plan Revision and forwarded the plan to NDEP for adoption and submittal to the 19 84

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FR 44699 August 27, 2019.

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