Before the court are five petitions for rehearing
1
with regard to the vacatur and remand of a final rule implementing the eight-hour national ambient air quality standard (“NAAQS”) for ozone under the Clean Air Act (“the CAA”), 42. U.S.C. § 7401 et
seq. See
Final Phase 1 Rule To Implement the 8-Hour Ozone NAAQS, 69 Fed.Reg. 23,951 (Apr. 30, 2004) (codified at 40 C.F.R. parts 40, 51, 81) (“2004 Rule”). The petitions overlap in part, challenging principally the court’s interpretation of the statutory gap, described in
Whitman v. American Trucking Ass’ns,
I.
In
Whitman,
the Supreme Court acknowledged that Subpart 2 of the CAA “unquestionably” provides for classifying nonattainment ozone areas even after EPA changed the system for measuring ozone levels from the highest annual one-hour average concentration to the fourth-highest annual eight-hour average concentration.
[T]o the extent that the new ozone standard is stricter than the old one, see 62 Fed.Reg. 38856, 38858 (1997) (8-hour standard of 0.09 ppm rather than 0.08 ppm would have “generally represented] the continuation of the [old] level of protection”), the classification system of Subpart 2 contains a gap, because it fails to classify areas whose ozone levels are greater than the new standard (and thus nonattaining) but less than the approximation of the old standard codified by Table 1.
EPA’s interpretation is irreconcilable with the CAA and Whitman. First, every other ozone level referenced in the sentence is in eight-hour terms and there is no signal that the final ozone level (the “approximation”) used a different metric. Second, 0.121 is not an “approximation” of 0.12, because an approximation is typically less precise than the true value. Here, Congress started the statutory Table 1 with the value 0.121 because it is the smallest design value that qualifies as no-nattaining. An area with a design value of precisely 0.12 would “meet[ ]” the NAAQS under section 107 of the CAA, 42 U.S.C. § 7407. Third, nowhere in Whitman does the Supreme Court signal that “the approximation of the old standard” is shorthand for 0.121 ppm of one-hour ozone.
EPA also maintains that there can be no eight-hour approximation of the one-hour ozone level because there is no one-to-one correspondence between the two metrics. EPA Pet’n at 5-6. But the lack of a precise equivalence is precisely why an approximation is necessary. The approximation referenced by the court, 0.09 ppm, is not, as EPA suggests, an arbitrary expression of the court’s scientific prowess; as acknowledged by the Supreme Court, the approximation comes directly from the rulemaking record, which stated that 0.09 ppm of eight-hour ozone “generally represented] the continuation of the [old] level of protection.”
See
1997 Rule,
EPA next objects to the court’s failure to defer, under
Chevron
Step 2, to EPA’s application óf Subpart 1 to gap areas. The court merely recognized that under
Chevron
agency action that does not constitute a reasonable interpretation of the statute must be vacated.
See id.
at 894. Because Congress sought to reduce EPA discretion by enacting Subpart 2 as part of the 1990 amendments to the CAA, EPA could not reasonably rely upon its preference for regulatory flexibility in setting the boundary between Subpart 1 and Subpart 2. EPA’s claim that the court nullified the discretion recognized by the Supreme Court in
Whitman
is meritless.
See Whitman,
II.
Four petitioners seek rehearing on which aspects of EPA’s regulation of one-
EPA and the Industry Petitioners claim, however, that in applying EPA’s interpretation of section 172(e), the court treated the provision as legally binding and usurped EPA’s discretion. Not so. In the rulemaking, EPA concluded that “Congress would have intended that control obligations that applied for purposes of the 1-hour NAAQS should remain in place.” Phase 1 Implementation of the 8-Hour Ozone NAAQS: Reconsideration, 70 Fed. Reg. 30,592, 30,593 (May 26, 2005). While the Industry Petitioners renew their arguments that the term “controls” in section 172(e) is ambiguous and that EPA’s interpretation eliminating certain controls is entitled to
Chevron
deference, they provide no basis to doubt the court’s conclusion that the “controls” at issue had a settled meaning.
See S. Coast Air Quality Mgmt. Dist.,
III.
We grant the joint request by EPA and the Environmental Petitioners to make explicit that the court’s reference to conformity determinations speaks only to the use of one-hour motor vehicle emissions budgets as part of eight-hour conformity determinations until eight-hour motor vehicle emissions budgets are available. See id. at 904-05.
We also grant their request that the 2004 Rule be vacated only to the extent that the court has sustained challenges to it. Although certain states and the District of Columbia object to partial vacatur on the ground that this will inequitably exempt Subpart 1 areas from regulation while the remand is pending, complete va-catur of a partially valid rule would only serve to stall progress where it is most needed. EPA is urged to act promptly in promulgating a revised rule that effectuates the statutory mandate by implement
Notes
. Separate petitions for rehearing were filed by a group of Environmental Petitioners, the Chamber of Greater Baton Rouge et al. ("Baton Rouge”), National Petrochemical & Refiners Association ("NPRA”), American Chemistry Council et al. ("ACC”), and EPA.
. Section 172(e) of the CAA provides that
[i]f the Administrator relaxes a national primary ambient air quality standard ... the Administrator shall ... promulgate requirements applicable to all areas which have not attained that standard as of the date of such relaxation. Such requirements shall provide for controls which are not less stringent than the controls applicable to areas designated nonattainment before such relaxation.
42 U.S.C. § 7502(e).
