All assessments as collected shall be immediately placed in an account to be known as "local improvement assessment account" . Such moneys shall be used only to pay indebtedness incurred for such improvements whether by temporary or permanent certificates, notes or bonds. Whenever a sinking fund is maintained, upon a vote of the governing body such moneys as collected shall be paid into such sinking fund and kept in a similarly designated account and used for the purposes herein described.
N.J.S. § 40:56-36