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Federal Register / Vol. 86, No. 30 / Wednesday, February 17, 2021 / Proposed Rules
level response be triggered, implementation of necessary control measures will take place as expeditiously as possible, but in no event later than 18 months after IDEQ
determines, based on quality-assured ambient data, that an action level trigger has been exceeded.
Idaho has identified the following potential contingency measures for the maintenance plan:
Measures to address emissions from residential wood combustion, including the potential implementation of a burn ban in the maintenance area at a lower threshold than currently in place in the ordinances for the six cities in the Idaho portion of the Logan UT-ID PM2.5 NAA.
The current ordinances trigger a burn ban when the Air Quality Index AQI
level reaches 75.
Additional measures to address other PM2.5 sources identified in the emissions inventory such as on-road and nonroad vehicles, industrial sources, and dust.
Based on our analysis of Idahos submittal, we propose to find that the contingency measure provisions provided in Idahos Logan, UT-ID PM2.5
maintenance plan are sufficient and meet the requirements of CAA section 175Ad.
E. Requirements for Transportation Conformity and Motor Vehicle Emissions Budgets MVEBs.
Transportation conformity is required by CAA section 176c. EPAs conformity rule at 40 CFR part 93, subpart A requires that transportation plans, programs, and projects conform to SIPs and establishes the criteria and
procedures for determining whether or not they conform. Conformity to a SIP
means that transportation activities will not produce new air quality violations, worsen existing violations, or delay timely attainment of the NAAQS. Thus, EPAs conformity rule requires a demonstration that emissions from a Metropolitan Planning Organizations MPOs Regional Transportation Plan and Transportation Improvement Program, involving Federal Highway Administration FHWA or Federal Transit Administration FTA funding or approval, are consistent with the MVEBs contained in a control strategy SIP revision or maintenance plan 40
CFR 93.101, 93.118, and 93.124. A
MVEB is the level of mobile source emissions of a pollutant relied upon in the attainment or maintenance demonstration to attain or maintain compliance with the NAAQS in the nonattainment or maintenance area.
A PM2.5 maintenance plan should identify MVEBs for direct PM2.5, NOX
and all other PM2.5 precursors from onroad mobile source emissions that are determined to significantly contribute to PM2.5 levels in the area.20 To determine which precursor pollutants are required to have an MVEB, IDEQ reviewed PM2.5
speciation at the Franklin monitor.
Based on PM2.5 speciation data and the local emissions inventory composition for each pollutant, IDEQ determined that in addition to NOX and direct PM2.5, the maintenance plan should also include an MVEB for VOCs because they are important precursors to secondary formation PM2.5. The State excluded direct PM2.5 emissions from paved road dust from the MVEBs in
accordance with 40 CFR 93.102b3, as these emissions made up only 1% of total wintertime contributions at the Franklin monitor. Vehicle emissions of SO2 and NH3 were also found to contribute minimally to PM2.5 in the area and therefore the maintenance plan does not include MVEBs for these precursors in accordance with 40 CFR
93.102b2v. See Section 6 of Idahos maintenance plan, in the docket for this action, for further analysis of the pollutants and precursors and the decisions on whether or not MVEBs were required for the individual pollutants and precursors.
The MVEBs for 2031 are identical to the on-road mobile source emissions inventory provided for direct PM2.5, NOX and VOCs in Table 1 in Section II.D.1 of this document of this proposed action for that year, except that the 2031
direct PM2.5 budget does not include paved road dust. As stated in that section, IDEQ used EPAs MOVES2014b model to develop vehicle emissions estimates for 2031, which were recalculated into tons per day from lbs per day for the 2031 MVEBs.
Based on its analysis, IDEQ set the mobile source emissions budgets for 2031 provided in Table 6 of this proposed action, as part of the September 13, 2019 maintenance plan submission. The previously approved 2017 MVEBs see 85 FR 9664, February 20, 2020, are included in Table 6.
According to EPAs conformity rule, the emissions budget acts as a ceiling on emissions in the year for which it is defined or until a SIP revision modifies the budget.21

TABLE 62017 AND 2031 MVEBS FOR THE IDAHO PORTION OF THE LOGAN UT-ID PM2.5 NAA
Motor vehicle emissions budget tpd
Year
Direct PM2.5

jbell on DSKJLSW7X2PROD with PROPOSALS

2017
2031

We propose to find that Idaho has evaluated the appropriate pollutants and precursors and appropriately established MVEBs for direct PM2.5, NOX and VOCs. Idaho used the most upto-date model MOVES2014b available at the time of submission in order to appropriately calculate these budgets.22
The MVEBs are based on the control measures in the maintenance plan and consistent with maintaining the 2006
20 See 21 See
40 CFR 93.102b2ivv and b3.
40 CFR 93.118.

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24-hour PM2.5 NAAQS. Based on our review of Idahos 2031 MVEBs, we are proposing to approve the budgets.
IV. Proposed Action EPA is proposing to redesignate the Idaho portion of the Logan UT-ID PM2.5
NAA, and proposing to approve the associated maintenance plan for the area. If this proposal is finalized, the designation status of the Idaho portion 22 See document titled EPA R10 MVEB and MOVES TSD in the docket for this proposed action
PO 00000

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NOX

VOC
.544
.149

.467
.198

of the Logan, UT-ID PM2.5 NAA under 40 CFR part 81 will be revised to attainment upon the effective date of that final action.
V. Statutory and Executive Order Reviews Under the CAA, redesignation of an area to attainment and the accompanying approval of a maintenance plan under section EPAR10OAR20200190 on www.regulations.gov.

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