Petitioners, various environmental groups,1 attack regulations, promulgated by the Environmental Protection Agency (EPA) under the Clean Air Amendments of 1970,2 setting air pollution control standards for basic oxygen process furnaces (BOPFs) used in the production of steel.3 Petitioners accuse EPA of arbitrariness in confining the scope of those rules to BOPF emissions which are captured and vented through a plant's smokestacks, thus permitting other-"fugitive"-BOPF emissions to enter the atmosphere without treatment. EPA contends that petitioners' bid for judicial review, implicating as it does a regulatory step four years old, is jurisdictionally out of time, and that in any event the agency action must be sustained on the merits.

We find that the instant challenge is in effect a petition to revise and broaden a preexisting BOPF standard on the basis of new information, and as such is not untimely.4 We then conclude that EPA acted reasonably in responding to that application by resolving to conduct a separate rulemaking proceeding with a view to possible amendment of the regulations, instead of giving them that sort of consideration during the course of a proceeding earlier initiated for a much more limited purpose.5 Accordingly, we affirm.

Basic oxygen process furnaces have become the principal means of raw steel production in the United States. Employing high-pressure oxygen during fabrication, they turn out steel more quickly and in greater quantities than was ever possible by the use of traditional furnaces.6 These gains in higher yield, however, have not been achieved without some environmental losses. Enormous amounts of particulate matter and toxic gas are released as oxygen is forced into the furnace at sonic speeds.7 Most are collected by a giant stationary control hood mounted above the furnace.8 These so-called stack, or primary, emissions are then ducted away to the plant's pollution control equipment,9 where substantially all particulate matter is removed before the air thus cleaned is vented into the atmosphere through a smokestack. Other emissions, however-notably those which escape the furnace when it is tipped away from the hood during loading or pouring operations-never enter the pollution control system. Instead, these secondary, or "fugitive," emissions enter the atmosphere untreated, either through ventilation holes in the roof or other openings in the building housing the furnace.10 Current nonregulation of these latter emissions is the matter lying at the heart of the controversy before us.

By Section 111 of the Clean Air Amendments of 1970, Congress instructed EPA to identify categories of stationary sources of air pollution that endanger the public health or welfare,11 and to promulgate regulations establishing standards of performance for new facilities within each category.12 These standards, that section commands, must reflect what in EPA's judgment is the best emission reduction technology available, taking cost and other factors into consideration.13 Pursuant to these directives, EPA issued a notice on June 11, 1973, adding iron and steel plants14 to the list of stationary pollution sources already found in need of regulation,15 and simultaneously issued proposed performance standards for new steel mills employing basic oxygen process furnaces.16

As proposed, the regulations were directed only to BOPF stack emissions; there was no provision curbing fugitive emissions.17 EPA justified this difference on the ground that the best available technology for BOPF emission reduction dealt only with primary, not secondary, emissions, and consequently that development of a fugitive emission standard was unfeasible.18 Additionally, the proposed rules contained two BOPF performance standards-one limiting the concentration of particulate matter released from the stack,19 and the other measuring the opacity of stack emissions20-which were designed to supplement each other as enforcement tools.21 Although the concentration, or mass, standard is the more precise of the two measurements, it also is considerably more expensive and time-consuming to utilize,22 and thus is impracticable to implement on a permanent or even on a frequent basis. The opacity standard, on the other hand, although less accurate requires no more than mere on-site observation of a plant's stack emissions by relatively untrained inspectors who can, periodically and without advance warning, visit a facility and quickly conduct compliance reviews.23

EPA invited comments on the proposed rules, and on March 8, 1974, promulgated final performance standards for basic oxygen process furnaces.24 The final mass standard was virtually identical to the one that had been proposed,25 but the opacity standard was withdrawn pending additional study of various technical problems.26 EPA made known its intention, however, to devise another BOPF opacity standard as soon as practicable.27 Petitioners did not then challenge either the exclusion of fugitive emissions or the absences of an opacity standard from the final regulations.

Three years later, EPA proposed a new opacity standard for BOPF stack emissions.28 Petitioners and others submitted comments thereon, arguing among other things that because of improved technology in the capture and treatment fugitive emissions, any BOPF performance standard that failed to address pollution resulting therefrom was violative of the Act.29 Without disputing petitioners' technological claim, EPA concluded that fugitive emission control was beyond the scope of a rulemaking proceeding instigated to fashion only a primary emission opacity standard.30 Accordingly, on April 13, 1978, EPA issued a final opacity regulation,31 and also announced that it would review the regulations to determine whether BOPF performance standards ultimately should extend to both primary and secondary emissions.32 Indeed, eleven months later the agency gave notice of its intention to propose revised BOPF performance standards that would govern emissions of both types.33

Meanwhile, on June 12, 1978, petitioners, dissatisfied with the agency's response, sought review in this court of the final opacity standard. Petitioners assail the opacity standard principally on the ground that the record assertedly does not support EPA's exemption of fugitive emissions from the regulations into which that standard was incorporated.34 In a parallel assault, petitioners contend that the agency acted arbitrarily in not adequately explaining its decision to deal only with primary emissions.35 EPA not only resists these claims, but argues in turn that petitioners' presentation of these objections in an allegedly untimely fashion deprives this court of jurisdiction to entertain them.36 Alternatively, the agency asserts that in any event its later decision37 to revise its performance standards to include BOPF fugitive emissions by early 1982 moots the entire controversy.38

We first consider EPA's contention that petitioners' challenge to the exclusion of fugitive emissions from the ambit of the final BOPF opacity standard and the regulations of which it became a part is out of time jurisdictionally. In support of this position, EPA relies upon former Section 307(b)(1) of the Act, which provided that petitions for review of performance standards formulated under Section 111 must be filed "within 30 days from the date of such promulgation."39 EPA asserts that the decision not to regulate fugitive emissions was made on March 8, 1974, when the final mass standard for BOPF primary emissions was promulgated, and urges that the time for judicial attacks on that decision has long since expired. EPA does not dispute that the petition for review was filed within the statutorily-prescribed period following promulgation of the final opacity standard; instead, the agency argues that because the opacity standard is merely an additional tool for monitoring compliance with the previously-established particulate standard for stack emissions,40 petitioners were on notice as early as 1974 that the opacity standard, whenever issued in final form, would not encompass fugitive emissions. Thus, EPA says, having failed to litigate the proper scope of the final mass standard, petitioners are foreclosed from now doing so in the guise of a challenge to the final opacity standard.

While EPA's theory has a modicum of surface appeal, it does not withstand scrutiny. Were petitioners merely attempting, as EPA insists, to attack collaterally a decision they could and should have resisted years earlier, we would not hesitate to dismiss the petition for review as untimely.41 The agency ignores, however, the final words of Section 307(b)(1), which unambiguously proclaim that petitions may be filed after the 30-day limit if based "solely on grounds arising after such 30th day."42 We have had occasion in the past to consider this proviso, as well as the legislative history that gave it birth,43 and have noted the congressional purpose in allowing later review based upon new information:

(I)t would not be in the public interest to measure for all time the adequacy of a promulgation of any standard or regulation by the information available at the time of such promulgation. In the area of protection of public health and environmental quality, it is clear that new information will be developed and that such information may dictate a revision or modification of any promulgated standard or regulation established under the act. The judicial review section, therefore, provides that any person may challenge any promulgation whenever it is alleged that significant new information has become available.44

Moreover, EPA itself has set forth in laudable detail procedures, which this court has explicitly endorsed,45 for seeking revision of a preexisting performance standard:

(1) The person seeking revision of a standard of performance, or any other standard reviewable under § 307, should petition EPA to revise the standard in question. The petition should be submitted together with supporting materials, or references to supporting materials.

(2) EPA should respond to the petition and if it denies the petition, set forth its reasons.

(3) If the petition is denied, the petitioner may seek review of the denial in this court pursuant to § 307.46

Here, petitioners presented to EPA considerable evidence that the technology of capturing and controlling secondary emissions had advanced since the agency decided in 1974 to omit fugitive emissions from coverage by the regulations.47 The validity of that decision is now disputed on the ground that it is no longer based on the best emission reduction technology available, as the Act requires.48 We are mindful that this evidence was submitted in the form of comments on the proposed final BOPF opacity standard, rather than in a formal petition to revise the preexisting mass standard, and whether a presentation of that sort always will satisfy the statutory and agency procedures, for revising regulations and standards is a question we need not now decide. Whatever EPA's future response to such submissions might be, it appears here to have taken heed of petitioners' comments on fugitive emissions and to have acted in consonance with them, for in issuing the final opacity standard the agency addressed them as follows:

EPA recognizes that fugitive emissions from BOPF shops are an important problem. However, it was not within the scope of this evaluation to consider an opacity standard for fugitive emissions.... EPA will be reviewing the standards of performance for new BOPF's in accordance with the 1977 amendments to the Clean Air Act.49 This review will address the need for limits on fugitive emissions as well as any revisions of the particulate concentration and opacity standards.50

And, as we noted above,51 EPA subsequently announced its intention to propose amendments to the BOPF standards, including revisions intercepting fugitive emissions.

We conclude, then, that petitioners' failure to mount a judicial challenge to the exclusion of fugitive emissions from coverage by the regulations when originally promulgated did not preclude them from later seeking judicial review of the agency's subsequent refusal to revise the standard on the basis of new information.

EPA also asserts that its decision to promulgate by early 1982 new BOPF performance standards that will extend to fugitive emissions moots the instant controversy.52 In light of the protracted nature of these agency proceedings,53 and continuing uncertainty as to when revised regulations will finally be adopted,54 we believe the case still exhibits the requisite level of liveliness.55 Despite EPA's projected publication of proposed new regulations by April, 1981,56 they have yet to come forth. Indeed, EPA recently notified the court of its estimate that a proposed standard on fugitive emissions will not be available before January, 1982,57 and we have no real assurance that even that will be the case.58 Accordingly, we proceed to consider the merits of petitioners' claims.

Treating petitioners' challenge as a petition to revise, our task is to determine whether EPA has acted arbitrarily in responding to new information that petitioners and others have brought to its attention.59 Petitioners asked EPA to put fugitive emissions within the purview of the final BOPF opacity standard promulgated on April 13, 1978;60 in effect, they sought to have the agency revise the preexisting BOPF performance standard to include secondary emissions. Petitioners did so, however, in the context of rulemaking proceedings designed only to consider and formulate an opacity standard for primary emissions,61 and on that account EPA denied their request.62

Given the history behind bifurcation of the rulemaking proceedings leading to BOPF performance standards,63 as well as the agency's prior explanations of the then unfeasibility of trying to develop a fugitive emission standard64 and the functional relationship between the particulate and opacity standards,65 we find little merit in petitioners' assertions that EPA failed either to support its decision to omit fugitive emissions or to explain adequately its reasons therefor. Moreover, when EPA published the final opacity standard, it simultaneously gave notice of its intention to inaugurate another rulemaking proceeding for the purpose of devising an amended standard that would accomplish precisely what petitioners sought.66 Petitioners have not pointed to anything that would suggest that the agency is not now preparing to do just that.67

Having decided upon an effort to broaden its regulations to control fugitive emissions-the very relief petitioners demanded-EPA cannot soundly be charged with arbitrariness merely because it chose a separate rulemaking proceeding as the process for proposing a revised standard in lieu of an undertaking to do so in the narrower context of the opacity standard proceedings as petitioners requested.68 And in view of the extensive "testing problems" presented and the "complex and evolving" fugitive emission control technology implicated,69 we think it was reasonable for the agency to establish the separate rulemaking agenda it did. The order under review is accordingly

Affirmed.

The majority opinion recognizes that the Environmental Protection Agency has now commenced rulemaking procedures looking to the promulgation of regulations to control fugitive emissions. This is the relief petitioners demand, and their only complaint now is that the agency is not moving fast enough. In these circumstances I think the case should be dismissed as moot.