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Federal Register / Vol. 86, No. 5 / Friday, January 8, 2021 / Proposed Rules
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G. Motor Vehicle Emissions Budgets for Transportation Conformity 1. Statutory and Regulatory Requirements Section 176c of the CAA requires Federal actions in nonattainment and maintenance areas to conform to the goals of the states SIP to eliminate or reduce the severity and number of violations of the NAAQS and achieve timely attainment of the standards.
Conformity to the goals of the SIP 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.
Actions involving Federal Highway Administration FHWA or Federal Transit Administration FTA funding or approval are subject to the EPAs transportation conformity rule, codified at 40 CFR part 93, subpart A. Under this rule, metropolitan planning organizations 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 areas regional transportation plans and transportation improvement programs 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 motor vehicle emissions budgets MVEBs or budgets contained in all control strategy attainment plans designed to attain the NAAQSs. Budgets are generally established for specific years and specific pollutants or precursors. Attainment plans for PM10
nonattainment areas should identify budgets for mobile source emissions of PM10, i.e., vehicle and fugitive dust emissions, in the area for each RFP
milestone year, as appropriate, and the attainment year, if the plan demonstrates attainment.76
For budgets to be approvable, they must meet, at a minimum, the EPAs adequacy criteria at 40 CFR 93.118e4.
To meet these requirements, the budgets must be consistent with the attainment and RFP requirements and reflect all the motor vehicle control measures contained in the attainment and RFP
demonstrations.77 Budgets may include a safety margin representing the 76 40

CFR 93.102b1.
CFR 93.118e4iii, iv and v. For more information on the transportation conformity requirements and applicable policies on MVEBs, please visit our transportation conformity website at: http www.epa.gov/otaq/stateresources/
transconf/index.htm.
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difference between projected emissions and the total amount of emissions estimated to satisfy any requirements for attainment or RFP.
The EPAs 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.78
2. Summary of the States Submission The West Pinal County PM10 Plan includes a budget for the 2018
attainment year. As discussed in Section III.E, we are proposing to disapprove the RFP and quantitative milestones elements of the Plan. No interim RFP
budget was submitted for 2016. The States submitted 2018 conformity budget for PM10 for the West Pinal County Area is provided in Table 6.

TABLE 62018 MOTOR VEHICLE
EMISSIONS BUDGET FOR THE WEST
PINAL COUNTY PM10 NONATTAINMENT AREA
Tons per year Source
Emissions
Direct On-Road Mobile Sources exhaust, tire and brake wear Unpaved Road Fugitive Dust
Paved Road Fugitive Dust
Road Construction/Maintenance
173.7
26,433.5
1,211.1
168.8

Total

27,987.1

Source: West Pinal County PM10 Plan, Table 54.

The methodologies ADEQ used to develop the motor vehicle emissions budget are provided in Appendix B of the West Pinal County PM10 Plan.79 As discussed in section III.A. of this proposal, ADEQ used MOVES2014 in the development of this budget; this emissions factor model was the latest EPA approved version at the time the West Pinal County PM10 Plan was developed. Paved road vehicle miles traveled VMT estimates for estimating direct and fugitive PM10 emissions were provided by MAG using an interpolation methodology where 2018
VMT was estimated from 2015 and 2025
regional transportation modeling runs.80
ADEQ used the most recently approved EPA provided AP42 emissions factor equations to develop paved and unpaved road fugitive dust emissions 78 40

CFR 93.118f2.
B, 120137, and 166180.
80 Appendix B, 120.
79 Appendix
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estimates.81 In addition to the line item source categories in the 2018 budget presented in Table 6, ADEQ specified that the budget includes an 81 ton per year safety margin.82
The EPA has neither found this 2018
budget to be adequate, nor have we acted on it in the past.
3. The EPAs Review of the States Submission As part of our review of the approvability of the motor vehicle emissions budget in the West Pinal County PM10 Plan, we have evaluated the budget using the adequacy criteria specified in the transportation conformity rule.83 Reviewing the budget against the criteria in the transportation conformity rule informs the EPAs decision to propose our action on the budget. We have determined that the 2018 budget submitted by Arizona for the West Pinal County area has not met several of these criteria.
First and foremost, 93.118e4iv requires that a budget, when considered together with all other emissions sources, be consistent with applicable requirements for RFP, attainment, or maintenance whichever is relevant to a given implementation plan submission.
In this case, the West Pinal County area budget is not consistent with the requirements for attainment and RFP, as discussed in Sections III.D and E of this proposal and our proposed disapproval of these two Plan elements. Secondly, the West Pinal County budget is presented in a tons per year format for an attainment plan intended to meet the 24-hour PM10 NAAQS. The budget must be consistent with the 24-hour timeframe of the attainment demonstration and PM10 standard, and therefore should be presented in a tons per day format. Finally, 93.118e4iii requires that the budget be clearly identified and precisely quantified. Although ADEQ
describes an allowance or safety margin in the West Pinal County PM10
Plan, the submitted budget does not clearly and explicitly identify this safety margin in its presentations of the budget.84 Also, a safety margin, as 81 ADEQ used the appropriate AP42 guidance in sections 13.2.1 and 13.2.2 to calculate fugitive dust from paved and unpaved roads. The AP42
emission factor equation inputs for estimating unpaved road fugitive dust emissions can be found in Appendix B, Table 511. The most recent EPA
revision and approval of these AP42 emission factor equations occurred in 2011 and are reflected in the Plans estimates; 76 FR 6328 February 4, 2011.
82 West Pinal County PM
10 Plan, 62.
83 40 CFR 93.118e4 and 5.
84 West Pinal County PM
10 Plan, Table 54;
Appendix D, Table D44.

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