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.
(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:
(8)
Transportation Control Measures (TCMs) during heavy traffic hours as provided under section 182(e)(4) of the CAA.
(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.
(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).
(u)
Attainment Area means, unless otherwise indicated, an area designated as either attainment, unclassifiable, or attainment/unclassifiable.