§ 51.900 - Definitions.

§ 51.900 Definitions.

The following definitions apply for purposes of this subpart. Any term not defined herein shall have the meaning as defined in 40 CFR 51.100.

(a) 1-hour NAAQS means the 1-hour ozone national ambient air quality standards codified at 40 CFR 50.9.

(b) 8-hour NAAQS means the 8-hour ozone national ambient air quality standards codified at 40 CFR 50.10.

(c) 1-hour ozone design value is the 1-hour ozone concentration calculated according to 40 CFR part 50, Appendix H and the interpretation methodology issued by the Administrator most recently before the date of the enactment of the CAA Amendments of 1990.

(d) 8-Hour ozone design value is the 8-hour ozone concentration calculated according to 40 CFR part 50, appendix I.

(e) CAA means the Clean Air Act as codified at 42 U.S.C. 7401-7671q (2003).

(f) Applicable requirements means for an area the following requirements to the extent such requirements apply or applied to the area for the area's classification under section 181(a)(1) of the CAA for the 1-hour NAAQS at designation for the 8-hour NAAQS:

(1) Reasonably available control technology (RACT).

(2) Inspection and maintenance programs (I/M).

(3) Major source applicability cut-offs for purposes of RACT.

(4) Rate of Progress (ROP) reductions.

(5) Stage II vapor recovery.

(6) Clean fuels fleet program under section 183(c)(4) of the CAA.

(7) Clean fuels for boilers under section 182(e)(3) of the CAA.

(8) Transportation Control Measures (TCMs) during heavy traffic hours as provided under section 182(e)(4) of the CAA.

(9) Enhanced (ambient) monitoring under section 182(c)(1) of the CAA.

(10) Transportation controls under section 182(c)(5) of the CAA.

(11) Vehicle miles traveled provisions of section 182(d)(1) of the CAA.

(12) NO_X requirements under section 182(f) of the CAA.

(13) Attainment demonstration or an alternative as provided under § 51.905(a)(1)(ii).

(14) Contingency measures required under CAA sections 172(c)(9) and 182(c)(9) that would be triggered based on a failure to attain the 1-hour NAAQS by the applicable attainment date or to make reasonable further progress toward attainment of the 1-hour NAAQS.

(g) Attainment year ozone season shall mean the ozone season immediately preceding a nonattainment area's attainment date.

(h) Designation for the 8-hour NAAQS shall mean the effective date of the 8-hour designation for an area.

(i) Higher classification/lower classification. For purposes of determining whether a classification is higher or lower, classifications are ranked from lowest to highest as follows: classification under subpart 1 of the CAA; marginal; moderate; serious; severe-15; severe-17; and extreme.

(j) Initially designated means the first designation that becomes effective for an area for the 8-hour NAAQS and does not include a redesignation to attainment or nonattainment for that standard.

(k) Maintenance area for the 1-hour NAAQS means an area that was designated nonattainment for the 1-hour NAAQS on or after November 15, 1990 and was redesignated to attainment for the 1-hour NAAQS subject to a maintenance plan as required by section 175A of the CAA.

(l) Nitrogen Oxides (NO_X) means the sum of nitric oxide and nitrogen dioxide in the flue gas or emission point, collectively expressed as nitrogen dioxide.

(m) NO_X SIP Call means the rules codified at 40 CFR 51.121 and 51.122.

(n) Ozone season means for each State, the ozone monitoring season as defined in 40 CFR Part 58, Appendix D, section 2.5 for that State.

(o) Ozone transport region means the area established by section 184(a) of the CAA or any other area established by the Administrator pursuant to section 176A of the CAA for purposes of ozone.

(p) Reasonable further progress (RFP) means for the purposes of the 8-hour NAAQS, the progress reductions required under section 172(c)(2) and section 182(b)(1) and (c)(2)(B) and (c)(2)(C) of the CAA.

(q) Rate of progress (ROP) means for purposes of the 1-hour NAAQS, the progress reductions required under section 172(c)(2) and section 182(b)(1) and (c)(2)(B) and (c)(2)(C) of the CAA.

(r) Revocation of the 1-hour NAAQS means the time at which the 1-hour NAAQS no longer apply to an area pursuant to 40 CFR 50.9(b).

(s) Subpart 1 (CAA) means subpart 1 of part D of title I of the CAA.

(t) Subpart 2 (CAA) means subpart 2 of part D of title I of the CAA.

(u) Attainment Area means, unless otherwise indicated, an area designated as either attainment, unclassifiable, or attainment/unclassifiable.

(v) Summer day emissions means an average day's emissions for a typical summer work weekday. The state will select the particular month(s) in summer and the day(s) in the work week to be represented. The selection of conditions should be coordinated with the conditions assumed in the development of RFP plans, ROP plans and demonstrations, and/or emissions budgets for transportation conformity, to allow comparability of daily emission estimates.

[69 FR 23996, Apr. 30, 2004, as amended at 70 FR 30604, May 26, 2005; 77 FR 28441, May 14, 2012; 80 FR 8799, Feb. 19, 2015]