It is hereby made the duty of the City Manager or his authorized representative to view sidewalks contiguous to any lot within the City to ascertain if any snow, sleet, mud, ice or other substance remains on such sidewalks. In the event that any of such substances is found on such sidewalks, the City Manager shall notify in writing the owner or occupant of the premises contiguous to such sidewalk to remove such substance forthwith. If the person owning or occupying the premises contiguous to such sidewalk is unknown or cannot be found or if any reasonable notice cannot be given to him within the City, or if the owner or occupant fails to remove such substance forthwith, then it shall be the duty of the City Manager or other agent of the City to remove such substance and the expense thereof shall be charged against the property and the owner thereof and may be recovered by proper civil action in the name of the City or may be assessed against the property as a special assessment for improvements and collected as other taxes of the City.