40 CFR §22.12

1. (a)Consolidation. The Presiding Officer or the Environmental Appeals Board may consolidate any or all matters at issue in two or more proceedings subject to these Consolidated Rules of Practice where: there exist common parties or common questions of fact or law; consolidation would expedite and simplify consideration of the issues; and consolidation would not adversely affect the rights of parties engaged in otherwise separate proceedings. Proceedings subject to subpart I of this part may be consolidated only upon the approval of all parties. Where a proceeding subject to the provisions of subpart I of this part is consolidated with a proceeding to which subpart I of this part does not apply, the procedures of subpart I of this part shall not apply to the consolidated proceeding.
2. (b)Severance. The Presiding Officer or the Environmental Appeals Board may, for good cause, order any proceedings severed with respect to any or all parties or issues.