Section 153.64 - Schedule of rates and fees(1) The district board shall fix the initial schedule of rates, fees or other charges for the use of and the services and facilities to be furnished by any such water system or sewer system to be paid by the owner, tenant or occupant of each lot or parcel of land which may be connected with or used by any such system or systems of the district. After the system or systems shall have been in operation the district board may revise the schedule of rates, fees and charges from time to time; provided, however, that such rates, fees and charges shall be so fixed and revised so as to provide some, which, with other funds available for such purposes, shall be sufficient at all times to pay the expenses of operating and maintaining such water system or sewer system or both, including reserves for such purposes, the principal of and interest on revenue bonds as the same shall become due and reserves therefor, and to provide a margin of safety over and above the total amount of any such payments, and to comply fully with any covenants contained in the proceedings authorizing the issuance of any bonds or other obligations of the district. The district shall charge and collect such rates, fees and charges so fixed or revised, and such rates, fees and charges shall not be subject to the supervision or regulation by any other commission, board, bureau, agency or other political subdivision or agency of the county or state.(2) Such rates, fees and charges shall be just and equitable and uniform for users of the same class and where appropriate may be based or computed either upon the quantity of water consumed or upon the number and size of sewer connections or upon the number and kind of plumbing fixtures in use in the premises or upon the number or average number of persons residing or working in or otherwise using or occupying such premises or upon any other factor affecting the use of the facilities furnished or upon any combination of the foregoing factors as may be determined by the district board on any other equitable basis.(3) No rates, fees or charges shall be fixed under the foregoing provisions of this section until after a public hearing at which all the users of the proposed sewer system or water system, or both, or owners, tenants or occupants served or to be served thereby and all others interested shall have an opportunity to be heard concerning the proposed rates, fees and charges. Notice of such public hearing setting forth the proposed schedule or schedules of rates, fees and charges shall be given by one publication in a newspaper published in the county and circulating in the district at least 10 days before the date fixed in such notice for the hearing, which may be adjourned from time to time. If there be no such newspaper published in the county and circulating in the district the notice of such rate hearing shall be posted as provided for in s. 153.56 regarding the posting of the notice calling the election creating the district. After such hearing such schedule or schedules, either as initially adopted, or as modified or amended, may be finally adopted.(4) A copy of the schedule or schedules of such rates, fees or charges finally adopted shall be kept on file in the office of the district clerk and shall be open at all times to public inspection. The rates, fees or charges so fixed for any class of users or property served shall be extended to cover any additional users or properties thereafter served which shall fall in the same class, without the necessity of any hearing or notice. Any change or revision of such rates, fees or charges may be made in the same manner as such rates, fees or charges were originally established as hereinabove provided; provided however, that if such changes or revisions be made substantially pro rata as to all classes of service no hearing or notice shall be required.