The parties to a proceeding under this chapter unless otherwise provided include:
(1) The commission staff;
(2) The applicant;
(3) Each municipality, county and governmental agency in the area where the facility is proposed to be sited, if timely application therefore is made as determined by the commission pursuant to rule; and
(4) Any person residing in the area where the facility is proposed to be sited, or any directly interested person, if timely application therefore is made as determined by the commission pursuant to rule. An application for party status in a proceeding under this chapter must contain a detailed statement of the interests and reasons prompting the application.