No lime, cement, mortar or concrete shall be mixed upon any street or sidewalk in the City except in boxes, the bottoms of which boxes shall be tight-tongued with grooved boards. Such boxes shall be placed upon four-inch bearers or sleepers, thereby leaving an air space, shall be protected on all sides by a margin of two-inch boards and shall be not less than six inches above the floor space.
Upon completion of the work in which such mortar boxes are used, the streets or sidewalks shall be thoroughly cleaned, and all mortar, sand, gravel, refuse matter and building materials of any kind shall be completely removed.
(1956 Code Sec. 16.2)