All machinery, equipment and materials must gain access to or be delivered through means of or via the completed culvert and approach, and in no instance shall machinery, trucks or other equipment be moved through unprotected ditches to gain access to any construction site. Exception to the above rules and regulations will be made during periods when ground frost makes it impractical or impossible to install permanent culverts properly. Under such conditions, timber bridges may be installed but only in such manner as not to impair or interfere with the proper drainage or run-off of water in such ditches.
(O.C. § 4.5)