Idaho Code § 40-1202

When the construction of a new bridge, for which the expenditure contemplated will exceed twenty-five thousand dollars ($25,000), five percent (5%) or twenty-five (25) qualified voters, whichever is greater, of a county highway system or highway district system interested in it may petition the respective commissioners for the erection of the needed bridge. The commissioners shall then advertise the petition, in accordance with the provisions of section 40-206, Idaho Code, giving the location and notify the director of highways to attend at a certain time and place to hear the petition.