1. A sewer district organized under the provisions of sections 249.760 to 249.810 may in the manner hereinafter provided authorize and issue sewerage system revenue bonds of the district. The bonds shall be payable solely from the revenues derived and to be derived from the operation of the district’s sanitary sewerage system or any part thereof including income from extensions and improvements to the system thereafter made or acquired. The bonds shall not constitute an indebtedness of the district and no taxes shall be levied to pay the bonds or the interest thereon.

2. Revenue bonds issued under the provisions of sections 249.760 to 249.810 shall be signed by the chairman of the board of supervisors of the district, and the seal of the district shall be affixed, attested by the secretary of the board. The bonds shall be payable at such bank or trust company as the board may select. The bonds shall be registered in the office of the secretary of the sewer district and when so registered and issued shall import absolute verity and shall be conclusive in favor of all persons purchasing the bonds that all proceedings and conditions precedent have been had and performed to authorize the issuance thereof, and the bonds shall be negotiable.

3. It is the mandatory duty of any sewer district issuing revenue bonds under sections 249.760 to 249.810 to fix and maintain rates and make and collect charges for the use and services of the district’s sewerage system for the benefit of which the revenue bonds were issued, sufficient to pay the cost of maintenance and operation thereof, to pay the principal of and the interest on all revenue bonds or any other obligations issued by the district and chargeable to the revenues of the system as and when the same become due, provide an adequate depreciation and replacement fund, and to create reasonable reserves therefor, and to provide funds ample to meet all valid and reasonable requirements of the resolution authorizing the revenue bonds. The fees, rates or charges shall be sufficient to allow for miscellaneous and emergency or unforeseen expenses and the rates shall from time to time be revised so as fully to meet the requirements of sections 249.760 to 249.810.

4. The resolution authorizing the issuance of revenue bonds hereunder may establish limitations upon the issuance of additional revenue bonds payable from the revenues of the district’s sewerage system and may provide that additional revenue bonds shall stand on a parity as to the revenues of the sewer district and in all other respects with revenue bonds previously issued on such conditions as may be specified in the resolution. The resolution may include other agreements, covenants or restrictions deemed advisable by the board to effect the efficient operation of the system and to safeguard the interest of the holders of the revenue bonds and to secure the payment of the bonds and the interest thereon promptly when due.

5. Whenever a district authorizes and issues revenue bonds under sections 249.760 to 249.810, an amount of the net revenues of the sewerage system of the district sufficient for the purpose shall, by operation of sections 249.760 to 249.810, be pledged to the payment of the principal of and the interest on the bonds as the same shall become due.