(2) The district may issue refunding bonds to redeem or replace any of its outstanding bonds. The bonds may bear interest at a rate not exceeding six percent each year. The district shall sell the refunding bonds for not less than par value, after notice published for at least two weeks in a newspaper printed and published within the county in which the district is located. The proceeds of the sale shall be applied in payment of matured or maturing bonds. If the district receives no qualifying bids for the refunding bonds they may be exchanged on a par-for-par basis for the matured or maturing bonds. The refunding bonds shall have serial maturity dates, not exceeding 20 years from issue date, as the board of directors shall specify. However, the board may issue the bonds with optional dates of redemption, and may provide for their calling and retirement upon such interest payment dates as are indicated on the bonds. Notice of intention to redeem the bonds shall consist of a notice from the secretary of the district published within the county in which the district is located, or a direct notice from the secretary to the owner of the bonds, if known. The issuance of the refunding bonds shall not require an election of the voters of the district but shall be done by resolution of the board of directors. [Formerly 545.218]