The board of directors of any irrigation district may by resolution convert any then existing local improvement district into a utility local improvement district at any time prior to the adoption of a resolution approving and confirming the initial assessment roll of such local improvement district. The resolution so converting the local improvement district shall provide for the payment of the special assessments levied in that district into the special fund established or to be established for the payment of revenue bonds issued to defray the cost of the local improvement district.