All money received from any special assessments in a city of the primary class shall be held by the city treasurer as a special fund to be applied to the payment of the improvement for which the assessment was made, and such money shall be used for no other purpose. Any surplus remaining in any such fund after all obligations against the same shall have been satisfied, may be transferred to any other fund by order of the city council.
Neb. Rev. Stat. §§ 15-835