All street work, plans, profiles and cross sections shall be prepared by the City Engineer, approved and adopted by the Council and filed in the office of the City Engineer before the passage of any resolution of intention to improve any street or portion thereof. The height of curbs and the height and curve of the street crown shall be such as shall be shown on the cross section so adopted and filed as specified in this section. At street intersections, curbs shall be carried around the corners on a level until opposite the property line in either direction; provided, that in cases where the natural contour of the land is such as to require, curb corners may be established on such grades as may be necessary, and in such cases the grade of curb corners shall be clearly shown by the plans and profiles for the same adopted and filed as set forth in this section.
(`78 Code, § 12.04.040.)