Congress enacted the Resource Conservation and Recovery Act (RCRA) in 1976 to establish a comprehensive program for regulation of hazardous waste management and disposal. Subsection (a) of RCRA § 3008 authorizes D to enter orders assessing civil penalties, including suspension or revocation of permits, for violation of RCRA regulations. Subsection (b) provides that, upon request made within thirty days of the issuance of a subsection (a) order, D 'shall promptly conduct a public hearing.' In 1978, D promulgated procedural regulations to implement the 'public hearing' provision of subsection (a) conforming to the provisions of the Administrative Procedure Act (APA) for formal adjudication. In the Hazardous and Solid Waste Amendments of 1984, Congress added to § 3008 a new subsection (h), authorizing the Administrator of EPA to issue 'an order requiring corrective action' whenever he 'determines that there is or has been a release of hazardous waste into the environment' from an interim facility. The 1984 Amendments also modified subsection (b) to make it clear that those subject to corrective action orders under the new subsection (h) have the right to a 'public hearing.' To govern subsection (h) hearings, D promulgated the procedural regulations here under review, 40 C.F.R. Part 24. Those rules provide that the formal adjudicatory procedures of Part 22 shall be applicable only to challenges to subsection (h) corrective action orders that include a suspension or revocation of interim status or an assessment of civil penalties for noncompliance. 40 C.F.R. § 24.01. If the order calls upon the interim facility operator merely to undertake an investigation or to do so in combination with interim corrective measures, then, depending upon the burden entailed by such measures, the agency will use either the informal adjudicatory procedures provided in Subpart B of Part 24 (for interim corrective measures that are 'neither costly nor technically complex,' 40 C.F.R. § 24.80) or those in Subpart C of Part 24. The procedures in Subparts B and C set forth informal rather than formal adjudicatory procedures. Direct examination and cross-examination of witnesses is not permitted, but the Presiding Officer may direct questions to either party. The Presiding Officer is to review the record and to file a recommended decision with the D Regional Administrator. The Regional Administrator is to receive comments from the parties and to render a final decision from which an aggrieved party may seek judicial review under the APA. Ps appealed the provisions that provided informal hearings for corrective-action orders issued under section 3008(h).