(a) Upon receipt of a petition for modification, the Mine Safety and Health Administration shall cause an investigation to be made as to the merits of the petition. Any party may request that the investigation of the petition for modification be expedited, or that the time period for investigating the petition be extended. Such requests shall be granted in the discretion of the Administrator upon good cause shown.

(b) As soon as is practicable after the investigation is completed, the appropriate Administrator shall make a proposed decision and order, which shall be served upon all parties to the proceeding. The proposed decision shall become final upon the 30th day after service thereof, unless a request for hearing has been filed with the appropriate Administrator, as provided in § 44.14 of this part.

(c) Service of the proposed decision is complete upon mailing.