(13) "Party" means:
(a) Specifically named persons whose substantial interests are being determined in the proceeding.
(b) Any other person who, as a matter of constitutional right, provision of statute, or provision of agency regulation, is entitled to participate in whole or in part in the proceeding, or whose substantial interests will be affected by proposed agency action, and who makes an appearance as a party.
(c) Any other person, including an agency staff member, allowed by the agency to intervene or participate in the proceeding as a party. An agency may by rule authorize limited forms of participation in agency proceedings for persons who are not eligible to become parties.
(d) Any county representative, agency, department, or unit funded and authorized by state statute or county ordinance to represent the interests of the consumers of a county, when the proceeding involves the substantial interests of a significant number of residents of the county and the board of county commissioners has, by resolution, authorized the representative, agency, department, or unit to represent the class of interested persons. The authorizing resolution shall apply to a specific proceeding and to appeals and ancillary proceedings thereto, and it shall not be required to state the names of the persons whose interests are to be represented.
The term "party" does not include a member government of a regional water supply authority or a governmental or quasi-judicial board or commission established by local ordinance or special or general law where the governing membership of such board or commission is shared with, in whole or in part, or appointed by a member government of a regional water supply authority in proceedings under s. 120.569, s. 120.57, or s. 120.68, to the extent that an interlocal agreement under ss. 163.01 and 373.713 exists in which the member government has agreed that its substantial interests are not affected by the proceedings or that it is to be bound by alternative dispute resolution in lieu of participating in the proceedings. This exclusion applies only to those particular types of disputes or controversies, if any, identified in an interlocal agreement.