(3)No restriction 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 works 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 restriction came into force or with the consent of the Highway Authority on or after that date.
