Iowa Code § 313A.4
The department is hereby authorized to enter into agreements with any federal bridge commission or any county or city of this state, and with an adjoining state or county, city, or town thereof, for the purpose of implementing an investigation of the feasibility of any toll bridge project for the bridging of a navigable river forming a portion of the boundary of this state and such adjoining state. The department may use any funds available for the purposes of this section. Such agreements may provide that in the event any such project is determined to be feasible and adopted, any advancement of funds by any state, county or city may be reimbursed out of any proceeds derived from the sale of bonds or out of tolls and revenues to be derived from such project.
Iowa Code § 313A.4