249.807.  Extension of boundaries of district, procedure. — 1.  The boundaries of any sewer district formed under the provisions of sections 249.760 to 249.810 may be extended from time to time by filing a petition with the clerk of the circuit court having jurisdiction, signed by the board of supervisors and five or more owners of real estate situated within the territory to be annexed.  The same proceeding shall then be followed as provided in sections 249.760 to 249.810 for the original organization of the district except that the proposition must be voted on affirmatively by a majority of the qualified voters voting on the proposition in the original district and the area to be annexed combined.

  2.  The costs incurred in the extension of the boundaries of the district shall be taxed to the district if the annexation is completed and otherwise against the petitioners, except that no costs shall be taxed to the board of supervisors.

  3.  Any owner of real estate that abuts upon a district once formed may petition the board of supervisors for the incorporation of the real estate in the district.  If approval is granted by the board, the clerk of the board shall endorse his certificate of the fact of approval by the board upon the petition.  The petition shall then be filed with the clerk of the circuit court of the county in which the district is incorporated.  It is then the duty of the court to amend the boundaries of the district by a decree incorporating the real estate in it.  A certified copy of the decree shall then be filed in the office of the recorder and in the office of the county clerk of the county in which the real estate is located, and in the office of the secretary of state.  The costs of the proceedings shall be borne by the petitioning property owners.

  4.  Any owner of land that has not been platted and such plat finally approved by the county planning commission, county zoning commission, county planning and zoning commission, or county governing body, that abuts upon a district previously formed or currently being formed, for which a trunk sewer has been condemned under chapter 523, shall not be compelled to join such district but may petition the board of supervisors of such district for incorporation of his land into such district under this section.  All costs of proceedings conducted under this subsection shall be paid by the petitioning landowner.