No person shall throw, rake, deposit, dump, drop or spill litter, waste material or foreign material upon the streets, sidewalks or other public rights of way within the City. The Mayor may at his discretion proclaim a period when leaves may be placed in the street rights of way for collection. Nothing in this Chapter shall prevent any person under a permit from the City from encumbering the streets or alleys with building materials or earth as may be necessary for the purpose of construction, erection, adding to, remodeling or repairing any building or structure or resulting from demolition operations; provided, however, that in the event of such encumbering of the streets or alleys, the contractor, owner or occupant shall remove any and all materials remaining within ten (10) days of the completion of the work, and shall leave the said streets or alleys in the same condition that they were in prior to such use thereof. (1988 Code § 17-214)