The board of township trustees of a township to which is apportioned by the board of county commissioners a portion of the expenses of the construction of an improvement shall levy annually upon the grand duplicate of the township a tax sufficient to pay said apportionment, but not to exceed five tenths of one mill on a dollar, and shall certify this to the county auditor on or before the fifteenth day of May in each year until all installments are provided for.
R.C. § 6131.53