(d) Objections to the petition may be filed by a party within fifteen (15) days of the filing of the petition. If objections to the petition are filed, the administrative law judge shall then determine whether petitioners have the requisite interest to be a party in the proceedings, as defined in
paragraph (b) of this section, and shall permit or deny participation accordingly. Where petitions to participate as parties are made by individuals or groups with common interests, the administrative law judge may request all such petititioners to designate a single representative, or he or she may recognize one or more of such petitioners. The administrative law judge shall give each such petitioner as well as the parties, written notice of the decision on his or her petition. For each petition granted, the administrative law judge shall provide a brief statement of the basis of the decision. If the petition is denied, he or she shall briefly state the grounds for denial and shall then treat the petition as a request for participation as amicus curiae.