Iowa Code § 357.14: Bids for construction.

1. If the majority of votes cast at the election are in favor of the improvement, the board of supervisors shall instruct the engineer to complete the plans and specifications, ready for receiving bids for construction of the project. The engineer shall complete the plans and specifications within thirty days of receiving notice to do so, unless for adequate reason the board extends the time.

2. When the completed plans and specifications are on file with the county auditor, and the estimated total cost of the project exceeds the competitive bid threshold in section 26.3, or as established in section 314.1B, the board of supervisors shall comply with the competitive bid procedures in chapter 26 for the construction of the project.