Easements for drainage or sewer purposes shall be provided as necessary, in order to ensure a clear air space of a minimum width of 10 feet. Easements for large structures or unusually deep structures shall be of such greater width as may be specified by the City Engineer. (Ord. 3153 § 2 (Exh. C), 2010; Ord. 2100 § 1, 1985; Ord. 1369, 1971; prior code § 28.906).