[p778] McGOWAN, Circuit Judge:
Section 111 of the Clean Air Act, 42 U.S.C. § 1857c-6 (1970 and Supp. IV, 1974), directs the Administrator of the Environmental Protection Agency (EPA) to maintain a list of stationary sources which "may contribute significantly to air pollution which causes or contributes to the endangerment of public health or welfare." Id. § 1857c-6(b) (1) (A) (1970). Within 120 days after the Administrator designates a particular source category as a "significant contributor," he must publish proposed standards of performance for sources within that category. The statute defines a standard of performance as:
A standard for emissions of air pollutants which reflects the degree of emission limitation achievable through the application of the best system of emission reduction which (taking into account the cost of achieving such reduction) the Administrator determines has been adequately demonstrated.
Id. § 1857c-6(a) (1). The Administrator must afford interested parties an opportunity to comment on the proposed standards, and, after considering such comments and making appropriate modifications, he must promulgate final standards within 90 days after publication of the proposed standards. Id. § 1857c-6(b) (1) (B) (Supp. IV, 1974).
On June 11, 1973 the Administrator published a notice in the Federal Register indicating that he had amended his list of "significant contributors" to include asphalt concrete plants. 38 Fed. Reg. 15380. On that same day he also published proposed standards of performance for new or modified asphalt concrete plants. Id. at 15406. After considering written comments on the proposed standards, the Administrator published final standards of performance on March 8, 1974. 39 Fed. Reg. 9307.
The National Asphalt Pavement Association (NAPA) and various asphalt concrete plants then invoked our exclusive review jurisdiction, [p779] 42 U.S.C. § 1857h-5(b) (1) (Supp. IV, 1974), filing a petition in this court challenging the action of the Administrator on the following grounds: (1) the Administrator failed to provide interested parties with a meaningful opportunity to comment on the designation of the asphalt concrete industry as a "significant contributor"; (2) the Administrator erred in determining that asphalt concrete plants are "significant contributors" within the meaning of the Act; and (3) there is insufficient evidence in the record (a) to support the Administrator's conclusion that the standards of performance are achievable through the best systems of emission reduction and (b) to show that the Administrator took attendant costs into account. For the reasons set forth below, we affirm the action of the Administrator.
I
Petitioners first argue that they were never given a meaningful opportunity to comment on the Administrator's designation of the asphalt concrete industry as a "significant contributor" within the meaning of the Clean Air Act. The thrust of petitioners' complaint appears to be that in simultaneously publishing the "significant contributor" designation and proposed standards of performance, the Administrator indicated that he had already reached a final determination on the "significant contributor" [p780] designation and did not consider it open for discussion during the informal rulemaking procedure. See Brief for Warren Brothers at 21 (Simultaneous publication of the designation and the proposed standards "virtually ensured that that determination would be immune from meaningful public comment."). We think an examination of the published notices, the agency's response to written comments, and record correspondence between petitioners and the EPA indicates that the "significant contributor" designation was subject to comment as a threshold question in the rulemaking process, and that petitioners were specifically informed of that fact.
We begin with the notices published in the Federal Register on June 11, 1973. The first notice, published in the "Notices" section of the Federal Register, announced that the Administrator, after considering available information, had determined that the asphalt concrete industry was a "significant contributor" pursuant to section 111 of the Act. The notice also announced that proposed standards of performance were being published that same day. 38 Fed. Reg. 15380.