Upon receipt of any request meeting the requirements of § 108.3, the Regional Administrator shall conduct a full investigation of the matter, in order to determine whether the request may be related to an effluent limitation or order under the Act. Following the investigation, the Regional Administrator shall notify the employee requesting the investigation (or the employee's representative) and the employer of such employee, in writing, of his preliminary findings and conclusions. The employee, the representative of such employee, or the employer may within fifteen days following receipt of the preliminary findings and conclusions of the Regional Administrator request a hearing under this part. Upon receipt of such a request, the Regional Administrator, with the concurrence of the Chief Administrative Law Judge, shall publish notice of a hearing to be held not less than 30 days following the date of such publication where he determines that there are factual issues concerning the existence of the alleged discrimination or its relationship to an effluent limitation or order under the Act. The notice shall specify a date before which any party (or representative of such party) may submit a request to appear.