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Federal Register / Vol. 86, No. 183 / Friday, September 24, 2021 / Proposed Rules
inventories for PM2.5 nonattainment areas.63
The base year emissions inventory for a Serious area attainment plan or a CAA
section 189d plan must provide a states best estimate of actual emissions from all sources of the relevant pollutants in the area, i.e., all emissions that contribute to the formation of a particular NAAQS pollutant. For the PM2.5 NAAQS, the base year inventory must include direct PM2.5 emissions, separately reported filterable and condensable PM2.5 emissions,64 and emissions of all chemical precursors to the formation of secondary PM2.5, i.e., nitrogen oxides NOX, sulfur dioxide SO2, volatile organic compounds VOC, and ammonia.65
The emissions inventory base year for a Serious area attainment plan must be one of the three years for which monitoring data were used to reclassify the area to Serious, or another technically appropriate year justified by the state in its Serious area SIP
submission.66 The emissions inventory base year for a Serious PM2.5
nonattainment area subject to CAA
section 189d must be one of the three years for which the EPA used monitored data to determine that the area failed to attain the PM2.5 NAAQS by the applicable Serious area attainment date, or another technically appropriate year justified by the state in its Serious area SIP submission.67
A states SIP submission must include documentation explaining how it calculated emissions data for the inventory. In estimating mobile source emissions, a state should use the latest emissions models and planning assumptions available at the time the SIP is developed. The latest EPAapproved version of Californias mobile source emission factor model for estimating tailpipe, brake, and tire wear emissions from on-road mobile sources that was available during the States and Districts development of the SJV PM2.5
Plan was EMFAC2014.68 Following 63 Emissions Inventory Guidance for Implementation of Ozone and Particulate Matter National Ambient Air Quality Standards NAAQS
and Regional Haze Regulations, U.S. EPA, May 2017 Emissions Inventory Guidance, available at https www.epa.gov/air-emissions-inventories/
air-emissions-inventory-guidance-implementationozone-and-particulate.
64 The Emissions Inventory Guidance identifies the types of sources for which the EPA expects states to provide condensable PM emissions inventories. Emissions Inventory Guidance, section 4.2.1 Condensable PM Emissions, 6365.
65 40 CFR 51.1008b1 and c1.
66 40 CFR 51.1008b1.
67 40 CFR 51.1008c1.
68 80 FR 77337 December 14, 2015. EMFAC is short for EMission FACtor. The EPA announced the availability of the EMFAC2014 model, effective on
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CARBs submission of the Plan, the EPA
approved EMFAC2017, the latest revision to this mobile source emissions model. States are also required to use the EPAs Compilation of Air Pollutant Emission Factors AP42 road dust method for calculating re-entrained road dust emissions from paved roads.69 70
In addition to the base year inventory submitted to meet the requirements of CAA section 172c3, the state must also submit a projected attainment year inventory and emissions projections for each RFP milestone year.71 These future emissions projections are necessary components of the attainment demonstrations required under CAA
sections 189b1 and 189d and the demonstration of RFP required under section 172c2.72 Emissions projections for future years referred to in the Plan as forecasted inventories should account for, among other things, the ongoing effects of economic growth and adopted emissions control requirements. The states SIP
submission should include documentation to explain how the state calculated the emissions projections.
Where a state chooses to allow new major stationary sources or major modifications to use emissions reduction credits ERCs that were generated through shutdown or curtailed emissions units occuring before the base year of an attainment plan, the projected emissions inventory used to develop the attainment demonstration must explicitly include the date of publication in the Federal Register, for use in state implementation plan development and transportation conformity in California. Upon that action, EMFAC2014 was required to be used for all new regional emissions analyses and CO, PM10, and PM2.5 hot-spot analyses that were started on or after December 14, 2017, which was the end of the grace period for using the prior mobile source emissions model, EMFAC2011.
69 The EPA released an update to AP42 in January 2011 that revised the equation for estimating paved road dust emissions based on an updated data regression that included new emissions tests results. 76 FR 6328 February 4, 2011. CARB used the revised 2011 AP42
methodology in developing on-road mobile source emissions; see https www.arb.ca.gov/ei/areasrc/
fullpdf/full7-9_2016.pdf.
70 AP42 has been published since 1972 as the primary source of the EPAs emission factor information and is available at https
www.epa.gov/air-emissions-factors-andquantification/ap-42-compilation-air-emissionsfactors. It contains emission factors and process information for more than 200 air pollution source categories. A source category is a specific industry sector or group of similar emitting sources. The emission factors have been developed and compiled from source test data, material balance studies, and engineering estimates.
71 40 CFR 51.1008 and 51.1012. See also Emissions Inventory Guidance, section 3 SIP
Inventory Requirements and Recommendations.
72 40 CFR 51.1004, 51.1008, 51.1011, and 51.1012.

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the emissions from such previously shutdown or curtailed emissions units.73
2. Summary of the States Submission The State included summaries of the planning emissions inventories for direct PM2.5 and PM2.5 precursors NOX, SOX,74 VOC,75 and ammonia and the documentation for the inventories for the San Joaquin Valley PM2.5
nonattainment area in Appendix B
Emissions Inventory and Appendix I New Source Review and Emission Reduction Credits of the 2018 PM2.5
Plan.
CARB and District staff worked together to develop the emissions inventories for the San Joaquin Valley PM2.5 nonattainment area. The District worked with operators of the stationary facilities in the nonattainment area to develop the stationary source emissions estimates. The responsibility for developing emissions estimates for area sources such as agricultural burning and paved road dust was shared by the District and CARB. CARB staff developed the emissions inventories for both on-road and non-road mobile sources.76
The Plan includes winter 24-hour average and annual average daily emissions inventories for the 2013 base year, which CARB derived from the 2012 emissions inventory, and estimated emissions for forecasted years from 2017 through 2028 for the attainment and RFP demonstrations for the 1997, 2006, and 2012 PM2.5
NAAQS.77 In this proposal, we are proposing action on those winter average and annual average emissions inventories necessary to support the Serious area and CAA section 189d nonattainment plans for the 1997 2473 40

CFR 51.165a3iiC1.
SJV PM2.5 Plan generally uses sulfur oxides or SOX in reference to SO2 as a precursor to the formation of PM2.5. We use SOX and SO2
interchangeably throughout this document.
75 The SJV PM
2.5 Plan generally uses reactive organic gasses or ROG in reference to VOC as a precursor to the formation of PM2.5. We use ROG
and VOC interchangeably throughout this document.
76 The EPA regulations refer to non-road vehicles and engines whereas CARB regulations refer to Other Mobile Sources or off-road vehicles and engines. These terms refer to the same types of vehicles and engines. We refer herein to such vehicles and engines as non-road sources.
77 2018 PM
2.5 Plan, Appendix B, B18 to B19.
The winter average daily planning inventory corresponds to the months of November through April, when daily, ambient PM2.5 concentrations are typically highest. The base year inventory is from the California Emissions Inventory Development and Reporting System and future year inventories were estimated using the California Emission Projection Analysis Model CEPAM, 2016 SIP
Baseline Emission Projections, version 1.05.
74 The
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