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Federal Register / Vol. 86, No. 7 / Tuesday, January 12, 2021 / Proposed Rules
for estimating on-road motor vehicle emissions.36
Emissions estimates of VOC and NOX
in the 2018 Western Nevada County Ozone Plan are grouped into three categories: 1 Stationary point sources, 2 areawide sources, 3 on-road and other mobile sources. Stationary point sources refer to larger sources that have a fixed geographic location, such as power plants, industrial engines, and oil storage tanks. This inventory includes emissions from stationary internal combustion engines and gasoline dispensing facilities; these are not inventoried individually but estimated as a group and reported as an aggregated total. Areawide sources are emissions sources occurring over a wide geographic area, such as consumer products and architectural coatings. The on-road sources include light-duty automobiles, light-, medium-, and heavy-duty trucks, and motorcycles.
Other mobile off-road sources include aircraft, recreational boats, and off-road equipment.
For the 2018 Western Nevada County Ozone Plan, stationary point source emissions for the 2011 base year emissions inventory are based on reported data from all stationary point sources in Western Nevada County using the Districts annual emissions reporting program, which applies under District Rule 513, Emissions Statements and Recordkeeping, to stationary sources that emit VOC or
NOX.37 Areawide sources include smaller emissions sources distributed across the nonattainment area. CARB
and the District estimate emissions for areawide sources using the most recent models and methodologies, including publicly available emission factors and activity information. CARB also reviewed the growth profiles for point and areawide source categories and updated them as necessary to ensure that the emission projections are based on data that reflect historical trends, current conditions, and recent economic and demographic forecasts. Growth forecasts for most point and areawide sources were developed by CARB.
On-road emissions inventories in the 2018 Western Nevada County Ozone Plan are based on 2012 travel activity data provided by the California Department of Motor Vehicles. CARB
provided emissions inventories for offroad equipment, including locomotives, pleasure craft and recreational vehicles, in-use off-road equipment, transport refrigeration units, cargo handling equipment, diesel agricultural equipment, and fuel storage and handling. Emissions from off-road sources were estimated using a suite of category-specific models or, where a new model was not available, the OFFROAD2007 model. A detailed list of the updates made to specific emissions inventory categories can be found in Chapter V.

CARB developed the emission forecasts in the 2018 Western Nevada County Ozone Plan by applying growth and control profiles to the base year inventory. Growth profiles for stationary point and areawide sources are derived from surrogates such as economic activity, fuel usage, population, housing units, etc. Growth projections were obtained from government entities with expertise in developing forecasts for specific sectors, and from econometric models. Control profiles, which account for emissions reductions resulting from adopted rules and regulations, are derived from data provided by the regulatory agencies responsible for the affected emission categories.38
Table 1 provides a summary of the Districts 2011 base year, 2012 baseline year for modeling, and 2020 attainment year baseline VOC and NOX emissions estimates in tons per day tpd for an average summer day. All inventory years in the 2018 Western Nevada County Ozone Plan are derived from the 2011 base year inventory, except that 2012 is used as the baseline year for attainment modeling. These inventories provide the basis for the control measure analysis and the attainment demonstration in the Plan. Based on the inventory for 2011, mobile sources are the predominant sources for both VOC
and NOX emissions. For a more detailed discussion of the inventories, see Appendix A of the Plan.

TABLE 1WESTERN NEVADA 2011 BASE YEAR, 2012 BASELINE YEAR FOR MODELING, AND 2020 ATTAINMENT YEAR
EMISSIONS INVENTORIES
Summer planning inventory, tpd 2011

2012

2020

Category VOC

VOC

NOX

NOX

VOC

NOX

Stationary
Area Sources
On-Road and Other Mobile Sources

0.7620
1.4109
3.3227

0.0999
0.1452
5.4415

0.7006
1.3946
3.1131

0.0997
0.1349
4.9124

0.7843
1.5150
1.9559

0.0918
0.1377
2.8886

Total for Western Nevada County Nonattainment Area

5.4956

5.6866

5.2083

5.1470

4.2552

3.1181

Source: 2018 Western Nevada County Ozone Plan, Appendix A. The sum of the emissions values may not equal the total shown due to rounding of the numbers.

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3. The EPAs Review of the States Submission We have reviewed the 2011 base year emissions inventory in the 2018
36 EMFAC is short for EMission FACtor. In December 2015, the EPA approved EMFAC2014 for SIP development and transportation conformity purposes in California. 80 FR 77337 December 14, 2015. EMFAC2014 was the most recently approved version of the EMFAC model that was available at the time of preparation of the Western Nevada County Ozone Attainment Plan. The EPA recently approved an updated version of the EMFAC model,
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Western Nevada County Ozone Plan and the inventory methodologies used by the District and CARB for consistency with CAA requirements and EPA

guidance. First, as required by EPA
regulation, we find that the 2011
inventory includes estimates for VOC
and NOX for a typical ozone season
EMFAC2017, for future SIP development and transportation purposes in California. 84 FR 41717
August 15, 2019.
37 The Air Pollution Control Officer of the NSAQMD may waive the applicability of the reporting required by District Rule 513 for certain classes or categories of sources with actual emissions or potential to emit less than 10 tons per year of actual facility-wide VOC or NOX emissions
if the emissions for the class or category of source are included in the base year and periodic emission inventories and the emissions are calculated using emission factors established by the EPA or other methods acceptable to the EPA. As described in Section B of this document, this approach is consistent with CAA section 182a3Bii.
38 2018 Western Nevada County Ozone Plan, page 23.

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