Federal Register - August 9, 2021
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Federal Register / Vol. 86, No. 150 / Monday, August 9, 2021 / Proposed Rules TABLE 22017 CLARK COUNTY OZONE PRECURSOR EMISSION INVENTORY
County-wide, average summer weekday, tons per day NOX emissions 2020 Ozone maintenance plan revision
Source category
VOC emissions
2018 Ozone maintenance plan revision
2020 Ozone maintenance plan revision
2018 Ozone maintenance plan revision
Point source
Nonpoint source
Commercial aviation
Federal aviation
On-road mobile
Nonroad mobile
Biogenic
12.40
7.651
11.47
0.50
46.96
37.45
2.43
11.79
5.68
13.38
1.77
53.65
24.78
5.00
2.95
62.56
1.73
0.24
29.47
28.25
362.61
2.51
59.94
2.75
1.04
28.49
30.36
132.00
Total
118.86
116.06
487.81
257.09
Sources: 2018 Ozone Maintenance Plan Revision, interpolated values from Tables 21 and 22; 2020 Ozone Maintenance Plan Revision, Tables 21 and 22.
With respect to on-road mobile source emissions, Clark County DES updated the emissions estimates using MOVES2014b, RTC travel demand modeling, and highway performance monitoring system data from the Nevada Department of Transportation.29 Clark County DES also selected the inventory mode, rather than the emission rate mode used in the 2018 Ozone Maintenance Plan Revision, with MOVES2014b emissions factors and projected emissions for 2022 from 2017
rather than 2015. Generally, on-road mobile source emissions estimates made using MOVES2014b are similar to MOVES2014a. With respect to nonroad emissions sources, the change in the 2017 emissions inventory is largely due to the use of the nonroad module of MOVES2014b that was released in August 2018. Clark County DES used default estimates from MOVES2014b for Clark County and the most significant changes were in the two largest sectors:
construction and lawn/garden, which increased and decreased, respectively.
Overall, nonroad emissions are higher for NOX but lower for VOC using MOVES2014b compared to using the nonroad module of MOVES2014a.
Biogenic emissions for Clark County were developed using the EPAs Biogenic Emission Inventory System 30
BEIS version 3.61, which replaced the
Emissions of Gasses and Aerosols from Nature MEGAN model used by Clark County DES for the 2011 Ozone Maintenance Plan 31 and the 2018
Ozone Maintenance Plan Revision. The BEIS model allows for interactions between air quality and meteorology. In 2017, the EPA updated the BEIS v3.61
to include the biogenic emissions landcover database version 5 BELD5
and the newer version of the forest inventory and analysis version 8.0. This updated model improved the biogenic VOC emissions estimates. Clark County DES used the updated BEIS model, which is part of SMOKE 4.7 Sparse Matrix Operator Kerner Emissions model, to generate the biogenic emissions for Clark County.32 The results show a slight decrease in NOX
and large increase in VOC biogenic emissions relative to the corresponding emissions estimates from the 2011
Ozone Maintenance Plan and 2018
Ozone Maintenance Plan Revision.
Based on our review of the emissions inventories and related documentation from the 2020 Ozone Maintenance Plan Revision, we find that the inventories for 2017 are comprehensive, that the methods and assumptions used by Clark County DES to develop the 2017
emission inventory are reasonable, and that the inventories reasonably estimate actual ozone season emissions in 2017.
Moreover, we find that the 2017
emissions inventories in the plan reflect the latest planning assumptions and emissions models available at the time the 2020 Ozone Maintenance Plan Revision was developed.
To provide the basis for the comparison of future emissions with the updated 2017 emissions, Clark County DES updated the 2022 emissions inventories using the same approaches as described above for the 2017
emissions inventory. Clark County DES
allocated the same amount of emissions reductions credits ERCs, for use in connection with the new major stationary source permitting program, for 2022 as had been allocated for that year in the 2018 Ozone Maintenance Plan Revision. With respect to transportation conformity safety margins, as described further in section V.B of this document, the Clark County DES significantly reduced the safety margins that had been included in budgets for the 2018 Ozone Maintenance Plan Revision. Table 3
below compares the NOX and VOC
emissions inventories, respectively, for 2022 from the 2020 Ozone Maintenance Plan Revision with the corresponding values from the 2018 Ozone Maintenance Plan Revision.
TABLE 32022 CLARK COUNTY OZONE PRECURSOR EMISSION INVENTORY
County-wide, average summer weekday, tons per day
lotter on DSK11XQN23PROD with PROPOSALS1
NOX emissions Source category
2020 Ozone maintenance plan revision
Point source
29 2020 Ozone Maintenance Plan Revision, Appendix A, 412.
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2018 Ozone maintenance plan revision
12.09
30 https www.epa.gov/air-emissions-modeling/
biogenic-emission-inventory-system-beis.
VOC emissions
12.26
31 2011
32 2020
E:FRFM09AUP1.SGM
2020 Ozone maintenance plan revision 3.12
2018 Ozone maintenance plan revision 2.72
Ozone Maintenance Plan, 64.
Ozone Maintenance Plan Revision, 14.
09AUP1
