“Hillside area,” as referred to in this title, means one with an average slope exceeding five percent. The standards under Section 16.08.135 apply to hillside areas with the added provision that areas with a cross-slope of forty percent are considered to be extremely marginal for development and the development of this terrain is limited to special approval and conditions set forth by the city based upon reasonable engineering standards. (Ord. 90-14 (part), 1990; Ord. 90-1 (part), 1990)