Any road, tile, or culvert construction, repair work, or materials on the county highway system, for which the county highway superintendent's estimated cost exceeds the amount provided in § 5-18A-14, shall be advertised and let at a public letting by the board of county commissioners or may be built by day labor. The board may reject all bids, in which case the board may readvertise and let at a public letting.
SDCL 31-12-13