PETITION FOR REVIEW OF ADMINISTRATIVE ORDER OF THE ENVIRONMENTAL PROTECTION AGENCY
Before Forman, Van Dusen and Gibbons, Circuit Judges
VAN DUSEN, Circuit Judge.
Pursuant to § 307(b)(1) of the Clean Air Act, 42 U.S.C. § 1857h-(b)(1) (1970),*fn1 Delaware Citizens for Clean Air, Inc. (DCCA) here challenges the Environmental Protection Agency's (EPA) approval of portions of Delaware's implementation plan. The challenge is on the merits. We stress this point because all the decided cases we have been able to locate either deal with strictly procedural attacks or dispose of substantive attacks on procedural grounds. See Duquesne Light Co. v. EPA, 481 F.2d 1 (3d Cir. 1973); Utah International, Inc. v. EPA, 478 F.2d 126 (10th Cir. 1973); Appalachian Power Co. v. EPA, 477 F.2d 495 (4th Cir. 1973); Getty Oil Co. v. Ruckelshaus, 467 F.2d 349 (3d Cir. 1972). Because of the unfamiliar and complex technical issues involved, we have approached this case with great "diffidence" and judicial restraint, see International Harvester Co. v. Ruckelshaus, 478 F.2d 615 (D.C. Cir. 1973), slip opinion at 56-57.*fn2
The legislative plan of the Clean Air Act was extensively set out by Judge Adams in Duquesne Light Co. v. EPA, supra, slip opinion at 2-6, and so it is unnecessary to discuss it in detail here.*fn3 Delaware, like all states, was required to submit to the EPA an implementation plan which would meet a variety of federal standards regarding the regulation of air pollution. Delaware held a federally mandated public hearing on November 29, 1971, and submitted its plan on January 28, 1972. On May 31, 1972, the EPA approved some parts of the plan and disapproved others. 37 Fed. Reg. 10842, 10856-57 (1972). DCCA filed its petition for review in June 1972. DCCA challenges EPA's approval of those sections of the Delaware plan dealing with the control of sulfur dioxide and nitrogen dioxide.
The EPA's authority to prescribe regulations for sulfur dioxide and nitrogen dioxide is based on Clean Air Act § 109, 42 U.S.C. § 1857c-4 (1970). The statute orders the EPA to promulgate what it calls national primary and secondary ambient air quality standards for substances which have been determined to be air pollutants. Primary standards are based on the protection of the public health; the secondary standards are based on the protection of the public welfare, which includes factors beyond merely the physical health of the populace. The primary and secondary standards promulgated by the EPA for sulfur dioxide appear, respectively, in 40 C.F.R. § 50.4 and § 50.5 (1972). The standard for nitrogen dioxide, which is both primary and secondary, is in 40 C.F.R. § 50.11 (1972). The EPA has also promulgated guidelines for the control strategies that should appear in state implementation plans where the ambient levels of a pollutant exceed the applicable standard. See 40 C.F.R. § 51.13 (1972) (sulfur dioxide) and § 51.14 (1972) (nitrogen dioxide).
The thrust of DCCA's petition is that the Delaware plan does not (1) meet the statutory deadline for attaining the nitrogen dioxide standard and (2) contain various measures, asserted to be made compulsory by the statute, for attaining the nitrogen dioxide standard and for maintaining it and the primary and secondary sulfur dioxide standards. Before dealing with DCCA's arguments more specifically, however, we will describe certain developments that make much of this case moot.
Delaware's plan itself seems to indicate that it is inadequate to attain the nitrogen dioxide standard.*fn4 Nevertheless, when EPA on May 31, 1972, approved the nitrogen dioxide control strategy it proposed an attainment date of May 31, 1975,*fn5 for the Metropolitan Philadelphia Interstate Air Quality Control Region.*fn6 The EPA also proposed the same date for the attainment of the primary and secondary sulfur dioxide standards.*fn7
Whatever the dates were as of May 31, 1972, they were changed after the filing of the petition in this matter by the publication on July 27, 1972, of new attainment dates.*fn8 This new schedule, whose "dates reflect the information presented in the Delaware Plan,"*fn9 gives January 1972 for the primary sulfur dioxide standard; January 1973 for the secondary sulfur dioxide standard; and January 1974 for the nitrogen dioxide standard. Quite recently, on May 23, 1973, the EPA published approval of a revision to the plan, changing the attainment date for the secondary sulfur dioxide standard from January 1973 to January 1974.*fn10 This revision was based on information submitted by Delaware following notice and a public hearing.
Meanwhile, because of litigation not directly related to the present case,*fn11 the EPA has withdrawn approval from the maintenance provisions of all state implementation plans.*fn12 Also, it has proposed a substantial relaxation of the secondary sulfur dioxide standard.*fn13
The net effect of these developments appears*fn14 to make moot a number of issues in this case. The challenge to the approval of Delaware's control strategy for attaining the primary sulfur dioxide standard is moot because Delaware has evidently already (January 1972) attained this standard. It is not possible to evaluate the correctness of the strategy for attaining the secondary sulfur dioxide standard, for the information upon the basis of which the attainment date was changed to January 1974 is not now before the court.*fn15 The maintenance provisions for both the primary and secondary sulfur dioxide standards and the single nitrogen dioxide standard are no longer approved (see note 12 above). The only remaining question raised by the petition is whether the approval of Delaware's strategy for attaining the nitrogen dioxide standard was proper.*fn16
Clean Air Act § 307(b)(1), 42 U.S.C. § 1857h-5(b)(1) (1970), is silent on the scope or standard of our review of the EPA's action. The Administrative Procedure Act, 5 U.S.C. § 701(a) (1970), dictates that the scope of review set out in 5 U.S.C. § 706 (1970) is applicable. See Citizens To Preserve Overton Park, Inc. v. Volpe, 401 U.S. 402, 410, 28 L. Ed. 2d 136, 91 S. Ct. 814 (1971). Yet the impact of § 706 is not entirely clear.
Section 706(2)(E) mandates that a reviewing court hold unlawful agency action "unsupported by substantial evidence in a case subject to sections 556 and 557 of this title or otherwise reviewed on the record of an agency hearing provided by statute...." This is not a case subject to sections 556 and 557, see Duquesne Light Co. v. EPA, 481 F.2d 1 (3d Cir. 1973); Appalachian Power Co. v. EPA, 477 F.2d 495 (4th Cir. 1973). Nor does the Clean Air Act, as construed in Duquesne Light Co. and Appalachian Power Co., provide for a hearing by the EPA. Rather, the statute affords interested parties a hearing at the state level before the state adopts an implementation plan. Clean Air Act § 110(a)(1), 42 U.S.C. § 1857c-5(a)(1) (1970). While the EPA has a duty to consider the record developed at the state hearing, see Appalachian Power Co. v. EPA, supra, slip opinion at 18-19 & n. 33, it is by no means clear what else the EPA can also consider in evaluating a plan. Given the time lag between the state hearing and the EPA decision, the fast rate of change in the state of the art of pollution measurement and control, and the determination of the EPA to keep current, it appears inevitable that the EPA will go beyond the record of the state hearing.* ...