Whenever the board of commissioners of any county is authorized to let contracts for the construction or repair of two or more bridges, the board of commissioners may consolidate any of such bridge construction or repair projects and may let a single contract therefor in the manner prescribed by law. All bidders for a contract for the construction or repair of two or more bridges shall submit a separate proposal on each such bridge construction or repair project included under such contract as required by Kan. Stat. Ann. § 68-1113, and any amendments thereto. When bids are let for such a consolidated project, the board shall accept the lowest lump sum bid for such consolidated project if such lump sum bid is less than the sum of the lowest bid for each separate bridge or culvert included in such consolidated project and may accept the lowest lump sum bid in any other case.