La. Stat. tit. 33 § 3987
The governing authority of any such sewerage district complying with the provisions of this Sub-part, shall have the power and is hereby authorized to issue, execute, negotiate, sell and deliver negotiable interest-bearing coupon certificates of the district in an amount not exceeding the total amount of the installments or deferred payments as provided for in R.S. 33:3986, said certificates to bear interest not exceeding six per centum per annum, payable annually, and to mature serially over a period not exceeding twenty years, but in no event shall said certificates extend over a longer period of time than that provided for by the ordinance levying the local or special assessments which may be payable in annual installments. Said certificates shall be of such form, date, denomination and payable in principal and interest at such time and place as the governing authority may determine, and such certificates shall be secured by and payable in principal and interest from the irrevocable pledge and dedication of the funds to be derived from the special assessments hereinabove provided, which are payable in annual installments or deferred payments as provided for by this Sub-Part, which funds shall be set aside in a separate trust fund and shall not be drawn upon for any purpose other than to pay the principal and interest of said certificates.
La. R.S. § 33:3987