Ind. Code § 8-17-1-10

Sec. 10. When any highway or part of a highway is constructed, reconstructed, or improved, the county executive shall order the auditor to give notice, in accordance with IC 5-3-1, that, on a day to be named by the executive in an order, sealed proposals will be received by the executive for the improvement in accordance with IC 36-1-12. However, if the proposed improvement includes any bridge having a total span of more than twenty (20) feet, the executive shall receive separate bids for the bridge, and shall enter into a separate contract to build the bridge.