Upon issuance, the proceeds of certificates of indebtedness must be set aside from other county funds and used and applied only for payment of the costs of reconstructing, replacing, repairing, or paying insurable losses as defined in this article and the cost of printing and delivering and other expenses of issuance of the certificates of indebtedness, and any other incidental expenses, and the reimbursement of the general tax receipts of the county or participating agency for any money previously expended therefrom to cover the cost of the insurable losses. Any balance of the proceeds, together with any part of the sum so set aside which is not required for payment of the cost of the insurable losses, must be promptly applied to the payment of the certificates of indebtedness as they become due. (Mont. Co. Code 1965, § 5-6; 1978 L.M.C., ch. 36, § 1; 1986 L.M.C., ch. 44, § 1.)