(a) Intervention. Any person desiring to become a party to a proceeding may move for leave to intervene. A motion for leave to intervene that is filed after the exchange of information pursuant to § 22.19(a) shall not be granted unless the movant shows good cause for its failure to file before such exchange of information. All requirements of these Consolidated Rules of Practice shall apply to a motion for leave to intervene as if the movant were a party. The Presiding Officer shall grant leave to intervene in all or part of the proceeding if: the movant claims an interest relating to the cause of action; a final order may as a practical matter impair the movant's ability to protect that interest; and the movant's interest is not adequately represented by existing parties. The intervenor shall be bound by any agreements, arrangements and other matters previously made in the proceeding unless otherwise ordered by the Presiding Officer or the Environmental Appeals Board for good cause.

(b) Non-party briefs. Any person who is not a party to a proceeding may move for leave to file a non-party brief. The motion shall identify the interest of the applicant and shall explain the relevance of the brief to the proceeding. All requirements of these Consolidated Rules of Practice shall apply to the motion as if the movant were a party. If the motion is granted, the Presiding Officer or Environmental Appeals Board shall issue an order setting the time for filing such brief. Any party to the proceeding may file a response to a non-party brief within 15 days after service of the non-party brief.