La. Stat. tit. 33 § 4256
When any municipality has issued bonds and has pledged the revenues of any utility for the payment thereof as herein provided, the municipality shall impose and collect fees and charges for the products, commodities and services furnished by the utility, including those furnished to the municipality itself and its various agencies and departments, in such amounts and at such rates as shall be fully sufficient at all times to (1) pay the expenses of operating and maintaining the utility, (2) provide a sinking fund sufficient to assure the prompt payment of principal of and interest on the bonds as each falls due, (3) provide such reasonable fund for contingencies as may be required by the resolution authorizing the bonds, and (4) provide an adequate depreciation fund for repairs, extensions and improvements to the utility necessary to assure adequate and efficient service to the public. No board or commission other than the governing body of the municipality shall have authority to fix or supervise the making of these fees and charges.
La. R.S. § 33:4256