The contours at one foot intervals for predominant ground slopes within the tract between level and five percent; and five foot contours for predominant ground slopes within the tract over five percent shall be shown on the tentative map. Such contours shall be based on the city datum. The closest city benchmark shall be used and its elevation called out on the map. Benchmark information shall be obtained from the city engineer. (Ord. 1785 NCS §4, 1990; Ord. 1046 NCS §1 (part), 1972; prior code §22.4.609.)