The excavation for curb shall be made to a depth of six inches below the intended surface and shall be refilled with good material.  After the grading and shaping is done, a foundation of mill-tailings or broken limestone six inches thick shall be placed in the subgrade, which shall be consolidated by ramming, to an even surface, and shall be moistened just before the concrete is placed thereon.  The curb shall be six inches wide at the top and eight inches wide at the bottom, and shall be 18 inches deep.  It shall be composed of a concrete core or backing, faced with one part portland cement and four parts mill-tailings.  The exposed surface of the curb shall be faced with mortar one inch in thickness, composed of one part sand and two parts portland cement.  The face corner of the curb shall be rounded to a radius on two inches.
(`83 Code, § 14-215)  Penalty, see § 101.99