La. Stat. tit. 33 § 3971
The governing authority of the municipality in which said sewerage district or sub-districts are located shall have authority and are hereby authorized to issue, execute, negotiate, sell and deliver negotiable interest-bearing coupon certificates of the municipality in an amount not exceeding the total amount of the funds necessary for the purchase, construction or maintenance of the sewers in said sewerage district or sub-districts; said certificates to bear interest not to exceed six per cent per annum, said interest to be paid annually in installments and to mature serially over a period not exceeding ten years and in no event shall said certificates extend more than ninety days longer than the period of time provided for by the ordinance levying the local or special assessments hereinabove provided. Said certificates shall be payable in annual installments and payable solely from the funds derived from the pledged sewerage charges and/or square-foot assessments, and shall be in such form, date, denomination, and payable in principal and interest at such time and places as the governing authority of the municipality may provide. Such certificates are to be secured in principal and interest by the irrevocable pledge and dedication of the funds derived from the levying and collecting of the local and special assessments on the real property within said sewerage district or sub-districts as provided for by this Sub-part, and, if the governing authorities so desire, the irrevocable pledge and dedication of the funds derived from the sewerage charges provided for in this Sub-part and either or both of said funds if pledged to secure said certificates shall be set aside in a separate fund and shall not be drawn upon for any other purpose than to pay the interest and principal of said certificates.
La. R.S. § 33:3971