When an order of the highway district board has become final and conclusive, the board shall levy upon all the land within the special tax district created by the order a special tax equal in amount to the amount so charged in the order against the special tax district, specifying the amount per acre. The secretary of the district shall transmit to the assessor and tax collector of the county a certified copy of the levy and of the order creating the special tax district. On receiving the certified copy, the county assessor shall assess, against the land in the special tax district, the amount levied, but it shall not be collected except as installments as shall be called for by the annual levies made by the highway district board of the taxes necessary to meet the requirements of the bonds. The existence of an assessment against land in the special tax district shall not be held to constitute a cloud upon the title of that land, nor as a breach of a convenant of warranty, title, nor against encumbrances in a deed or contract for the land, nor as rendering the title to the land unmarketable. The special tax authorized within special tax districts is a tax for the purpose of securing for the special tax districts the benefit of local highways within the limits of the special tax district, as distinguished from the general purpose of the bond issue as a whole of securing the benefit of a system of highways for the highway district at large.