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Federal Register / Vol. 86, No. 122 / Tuesday, June 29, 2021 / Proposed Rules provided in a Technical Support Document TSD included in the docket to this proposed rulemaking.9
IV. What are the criteria for redesignation?
The CAA provides the requirements for redesignating a nonattainment area to attainment. Specifically, section 107d3E of the CAA allows for redesignation of a nonattainment area provided that: 1 The Administrator determines that the area has attained the applicable NAAQS; 2 the Administrator has fully approved the applicable implementation plan for the area under section 110k; 3 the Administrator determines that the improvement in air quality is due to permanent and enforceable reductions in emissions resulting from implementation of the applicable SIP
and applicable federal air pollutant control regulations and other permanent and enforceable reductions; 4 the Administrator has fully approved a maintenance plan for the area as meeting the requirements of section 175A; and 5 the State containing such area has met all requirements applicable to the area under section 110 and part D of the CAA.
V. What is the EPAs analysis of the request?
The EPAs evaluation of Missouris redesignation request and maintenance
plan is based on consideration of the five redesignation criteria provided under CAA section 107d3E and relevant guidance. On April 16, 1992, the EPA provided guidance on redesignation in the General Preamble for the Implementation of title I of the CAA Amendments of 1990 and supplemented this guidance on April 28, 1992.10 11 The EPA has provided further guidance on processing redesignation requests in several guidance documents. For the purposes of this action, the EPA will be referencing two of these documents: 1
The September 4, 1992 memo Procedures for Processing Requests to Redesignate Areas to Attainment Calcagni Memo; and 2 the EPAs April 23, 2014 memorandum Guidance for 1-Hour SO2 Nonattainment Area SIP
Submissions 2014 SO2 Guidance.12
Criterion 1The Jefferson County SO2
Nonattainment Area Has Attained the 2010 1-Hour SO2 NAAQS
For redesignating a nonattainment area to attainment, the CAA requires the EPA to determine that the area has attained the applicable NAAQS CAA
section 107d3Ei. The EPA
determined that the area attained the 2010 1-hour SO2 NAAQS in its September 2017 NFRM approving the States request for a clean data determination meeting the requirements of CAA section 107d3Ei. That
determination was primarily based on a modeling analysis of recent actual emissions for sources in and around the nonattainment area. As described further in the TSD for this action, the Supplemental modeling submitted by Missouri in February 2019 to support the redesignation request and maintenance plan is based on a modeling demonstration of permanent and enforceable emissions at sources in the nonattainment area that similarly demonstrates the area is attaining the standard. Therefore, the EPAs determination that the area had achieved clean data is consistent with the proposed action to redesignate the area.
Following the EPAs determination that the area had achieved clean data, the EPA reviewed quality assured monitoring data recorded in the EPAs Air Quality System AQS from the Mott Street monitoring station. The 3-year, 20182020 design value for the Mott Street monitor is 14 ppb and continues to meet the 2010 1-hour SO2 NAAQS, as shown in Table 1. If the 3-year design value violates the NAAQS prior to the EPA acting in response to the States request, the EPA will not take final action to approve the redesignation request.13 As discussed in more detail later in this section, Missouri has committed to continue monitoring in this area in accordance with 40 CFR part 58.

TABLE 120152020 MOTT STREET MONITOR DATA PARTS PER BILLION ppb; 99TH PERCENTILE 99% AND 3-YEAR
DESIGN VALUE dv Site
2015
99th %

2016
99th %

2017
99th %

2018
99th %

2019
99th %

2020
99th %

20152017
dv
20162018
dv
20172019
dv
20182020
dv
Mott Street

38

13

18

12

12

17

23

14

14

14

For redesignating a nonattainment area to attainment under a NAAQS, the CAA requires the EPA to determine that the State has met all applicable requirements for that NAAQS under section 110 and part D of title I of the CAA CAA section 107d3Ev and that the State has a fully approved SIP
under section 110k for that NAAQS for
the area CAA section 107d3Eii.
The EPA proposes to find that Missouri has met all applicable SIP requirements for purposes of redesignation for the Jefferson County SO2 nonattainment area under section 110 of the CAA
general SIP requirements.
Additionally, the EPA proposes to find that the Missouri SIP satisfies the criterion that it meets applicable SIP
requirements for purposes of redesignation under part D of title I of the CAA in accordance with section 107d3Ev. Further, the EPA

9 The TSD discusses the EPAs review of the CAA
section 107d3E redesignation criteria: i A
determination of attainment; iii a determination that the improvement in air quality is due to permanent and enforceable reductions in emissions;
and iv a fully approved maintenance plan as well
CAA section 175A maintenance plan criteria: 1
Attainment inventory; 2 maintenance demonstration; and 3 continued monitoring. The EPAs review of the remaining redesignation and maintenance plan criteria are sufficiently addressed in the preamble language to the NPRM.

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Criterion 2Missouri Has a Fully Approved SIP Under Section 110k;
and Criterion 5Missouri Has Met All Applicable Requirements Under Section 110 and Part D of Title I of the CAA

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proposes to determine that the SIP is fully approved with respect to all requirements applicable for the 2010 1hour SO2 NAAQS for purposes of redesignation in accordance with section 107d3Eii. In proposing to make these determinations, the EPA
ascertained which requirements are applicable to the Jefferson County SO2
nonattainment area and, if applicable, that they are fully approved under section 110k.

10 See
57 FR 13498.
57 FR 18070.
12 https www.epa.gov/sites/production/files/
2016-06/documents/20140423guidance_
nonattainment_sip.pdf.
13 See 2014 SO Guidance, at 56.
2 11 See
E:FRFM29JNP1.SGM

29JNP1