The total cost of a sewage or garbage disposal system, or any portion thereof, may be defrayed by the following alternative methods:
5. From moneys secured by the issuance and sale of first mortgage bonds secured by the assets and property of the improvement or system in like manner as provided in subsection 4, except that such bonds may be issued for the total cost of the improvement upon compliance with this subsection. Bonds issued under this subsection shall be secured by a pledge of the net revenues of the improvement or system to be set apart as an interest and sinking fund to pay the principal and interest of such first mortgage bonds as they mature. If the method provided in this subsection is utilized by any municipality to defray the cost of a sewage disposal system, it, by a resolution of its governing body, shall create the district, provide for and approve the plans and specifications and estimates of the cost, and adopt and publish the resolution declaring the work necessary to be done in accordance with the requirements of chapter 40-22 as far as the same may be applicable. If the owners of property liable to be imposed with the sewage disposal service charges as provided in this subsection shall file with the city auditor, within thirty days after the first publication of the resolution, a written protest against the improvement, the governing body at its next meeting after the expiration of the time for filing protests against the improvement shall hear and determine the sufficiency of the protests. After the hearing has been had, the governing body, if it finds the protests to contain the signatures of the owners of a majority of the property liable to be charged, shall not proceed further with the improvement. If the protests are found insufficient or invalid, the governing body of the municipality may cause the improvement to be made, contract therefor, and defray the cost thereof in the manner provided in this subsection. A municipality may pay the cost of leasing any sewage systems and all related real and personal property for the collection, treatment, purification, and disposal in a sanitary manner of sewage from the state, or any agency or institution of the state under section 40-34-19, solely from revenues to be derived by the municipality from the ownership, sale, lease, disposition, and operation of the sewage systems; the funds or any other amounts invested by the municipality pursuant to section 21-06-07, or invested on the municipality's behalf by the state, or any agency of the state, in conformity with policies of the industrial commission, including investment in a guaranteed investment contract and any earnings thereon, to the extent pledged therefor; and funds, if any, appropriated annually by the governing body of the municipality or received from federal or state sources.