It is hereby declared unlawful for any mover or owner of houses and buildings to move any building or structure in such a manner that there shall remain holes or depressions dangerous to life or limb; there shall not remain debris or rubbish from which dust or offensive odors shall emanate detrimental to public health. Such premises shall be left in a safe, clean, and sanitary condition. When a building has been moved for the purpose of erecting thereon another building or structure, the chief building official at his discretion may permit the owner of such property to maintain for a period not to exceed six months any remaining hole or depression if the following conditions are met: Such hole or depression is maintained in a sanitary condition and kept clean of all rubbish or debris of any nature; that such hole or depression is surrounded and protected by a strong and suitable barricade not less than five feet high; that such barricade is maintained in a sound and proper condition; and that said owner shall covenant for himself, his heirs and assigns, to properly fill such remaining hole or depression at the conclusion of the said six month period unless building operations thereat have then been begun; provided, that the city council may, upon good cause shown, extend the period of time during which the hole or depression may be maintained, subject to any conditions that the city council may prescribe.