No part of any building or structure of any kind nor any cellar or other excavation shall encroach upon or within any public street, sidewalk, land, easement or right of way except by specific authority of the City Council as contained in a franchise, ordinance or resolution of the City Council duly noted in its journal or minutes; and any building or structure or part thereof and any cellar or other excavation which may exist at any time in violation of this section may be declared by the City Council to constitute a nuisance and subject to abatement as provided in Article 1111 ; provided, that nothing in this section shall apply to any excavation made pursuant to any excavation permit under the provisions of Article 909.