605 ILCS 5/5-205.1

Prepare or cause to be prepared, plans, specifications and estimates for all bridges and culverts to be built by the county, or by one or more road districts, and supervise the construction of all such bridges and culverts. When the clear span length of the bridge or culvert is more than 30 feet, the plans and specifications, before being finally adopted, shall be submitted to the Department for approval.