La. R.S. 33:4286

Whenever any certificates of indebtedness are issued in accordance with this Sub-part, the municipal authority shall provide for the creation of a sinking fund into which shall be paid from the revenues of the utility, subject only to prior payment of reasonable and necessary operation and maintenance expenses, sums fully sufficient to pay the principal and interest on the certificates, and to create reserves for contingencies provided in the resolution and election. The moneys in the sinking fund shall be applied to the payment of the principal and interest of the certificates or to the purchase or retirement of the certificates prior to maturity in the manner provided.