Ohio Rev. Code § 5559.12
After the board of county commissioners has decided to proceed with an improvement as provided by section 5559.02 of the Revised Code, it shall advertise for bids once, not later than two weeks prior to the date fixed for the letting of the contract, in a newspaper of general circulation in the county. Such notice shall state that copies of the surveys, plans, profiles, cross sections, estimates, and specifications for such improvement are on file in the office of the board, and the time within which bids will be received. The board shall award the contract to the lowest responsible bidder.
The contract shall be let upon the basis of lump sum bids, unless the board orders that it be let upon the basis of unit price bids, in which event it shall be let upon such basis. The bids received shall be opened at the time stated in the notice. The board may reject all bids.
R.C. § 5559.12