La. Stat. tit. 33 § 3973
The governing authority of the municipality may by resolution empower and authorize the mayor to negotiate and deliver such sewer certificates and collect the purchase price thereof and do any and all things necessary and incidental thereto, or authorize delivery to the contractor of all or any part hereof of the said sewer certificates in payment of the contractual obligation covering such improvements. The funds derived from the sale of said sewer certificates shall be expended solely in payment of the cost of the improvement herein authorized and shall not be drawn upon for any other purpose whatsoever, provided that any surplus funds remaining after the cost of such improvement and incidental expenses expended therewith shall be expended for any purpose whatsoever for the improvement or maintenance of the sewer system of the district or sub-districts involved.
La. R.S. § 33:3973