(1) Any person, other than the original parties to the proceeding, who shall desire to appear and participate in any proceeding before the commission, and who does not desire to broaden the issues of the original proceeding, may petition in writing for leave to intervene in the proceeding. Such a petition shall be filed no later than the intervention deadline established in a procedural order, if one is entered. If no procedural order is entered, the petition shall be filed no later than one week prior to the commencement of hearing. No such petition or motion shall be filed after these times, except for good cause shown. The petition or motion to intervene must disclose the name and address of the party intervening; the name and address of his attorney, if any; a clear and concise statement of the direct and substantial interest of the petitioner in the proceeding; his position in regard to the matter in controversy; and a statement of the relief desired.