Should any bond issue where the indebtedness has been charged in part against adjoining property be funded or refunded so that a sinking fund for the original issue is not required to be established, then the annual levy for sinking fund requirements need not be made upon the land in the special tax districts created in respect to the bond issue; or, at the option of the highway district commissioners, a portion of the bond issue, to meet a sufficient amount which has been charged against the special tax districts, may remain without refunding, and shall subsequently be paid and retired with the proceeds of the special taxes on the land within the special tax districts. If the proceeds prove temporarily insufficient, then they shall be paid from the other revenues of the district. If the whole of an issue is refunded and new bonds issued, then the land within the special tax districts shall continue to be specially taxed for the new bonds, equal in amount to the refunding issue equably, both as to principal and interest, with the taxation of the district at large for the bond purposes. On the funding of any issue of bonds, on receiving from the treasurer of the district a certificate, under the seal of the district, signed by the secretary and treasurer of the district and either by the chairman or by the other highway district commissioners that the bonds have been actually funded and retired, the special assessment made against the land within the special tax districts created for the bond issue as provided in section 40-810, Idaho Code, shall be canceled, vacated and annulled, and a new special levy of the same amount shall be assessed against the land in the special tax districts in respect to the new or refunding bonds.