Single-story structures attached to the main building may be located within 10 feet of the rear property line, but shall not be closer than five feet from any retaining wall or toe of slope and said structure shall not occupy more than 30 percent of the rear yard area. Rear yards that have an elevation difference of six feet or more from the adjoining lot or parcel may reduce said 10 feet one foot for every foot over six feet, but not more than five feet. Two-story structures shall not be closer than the required rear yard setback. (Ord. 3153 § 2 (Exh. A), 2010; Ord. 1356 § 1, 1971; Ord. 1212 § 1, 1969; prior code § 33.504(K)).