All holes, depressions, excavations or other dangerous places upon private lots, which holes, depressions, excavations or other dangerous places are below the grade of the adjoining street, shall be properly enclosed with a fence or wall or filled up by the owner or occupant of the lot so as to prevent persons or animals from falling therein. It shall be the duty of the City Manager, upon ascertaining that such holes, depressions, excavations or other dangerous places exist, to notify the owner or occupant of the premises thereof and require that fences or walls be built or that they be filled up within such a period as he deems the exigencies of the case may require in order to obviate the danger. In case of failure to comply with such notification, the City Manager shall do what is necessary to obviate the danger at the expense of the City, and the sum so expended, together with such fine that may be imposed, shall be collected of the owner or occupant as other fines are collected.