All new streets on any plat shall be graded to their full width. All new streets on any plat shall have curbs and gutters of portland cement concrete, with a minimum distance of 30 feet between curbs; together with an adequate storm sewer system consisting of catch basins and underground drainage structures of sufficient capacity and design with proper outlets wherever necessary satisfactory to accomplish the runoff of storm water; provided, however, that in subdivisions where at least 80% of the lots have a frontage of 120 feet or more, the planning commission may waive the requirement for curbs and establish a narrower width for the traveled portion of the streets, if valley-type gutters of portland cement concrete are provided.
('59 Code, § 1113.02) Penalty, see § 151.99