Iowa Code § 309.41: Optional advertisement and letting.

1. Contracts not embraced within the provisions of section 309.40 or 309.40A shall be either advertised and let at a public letting or, where the cost does not exceed the county engineer’s estimate, let through informal bid procedure by contacting at least three qualified bidders prior to letting the contract. The informal bids received together with a statement setting forth the reasons for use of the informal procedure and bid acceptance shall be entered in the minutes of the board of supervisors meeting at which such action was taken.

2. Nothing contained in this section shall be deemed to prohibit the board of supervisors from purchasing material and using county equipment and regularly employed county road personnel on a project within their capability as determined by the county engineer.