Appeal.

(a) Any party aggrieved by a presiding officer's decision may file an appeal with the Administrator. The appeal must be filed within twenty (20) days after service of the presiding officer's decision. (b) Prior to rendering a final determination on an appeal, the Administrator may remand the case for further proceedings before the hearing officer. (c) The filing of an appeal does not stay the effectiveness of a compliance order unless the Administrator expressly so provides.