(3)No restrictions in force under section 9 shall apply to any excavation or works necessary in connection with any drains, ditches or other drainage works for agricultural purposes or to any work necessary for the repair, renewal enlargement or maintenance of any sewer, drain, electric line, pipe, duct, or other apparatus, constructed in or upon the land before the date on which the restrictions came into force or with the consent of the Highway Authority on or after that date.
