The property owner(s) of a lot or parcel from which an illegal discharge originates shall be ultimately responsible for all abatement and cleanup costs associated with the discharge, at his own expense, if the responsible party cannot be located. Likewise, if the tenant of a multi-family residential unit has discharged a prohibited material or waste into the City's storm drainage system or has caused the contamination of storm water runoff from the property by his activities and the City Engineer cannot determine the responsible party or residential unit responsible, the owner of the property from which the discharge originated, shall be responsible for the cleanup and abatement costs to mitigate the condition. Additionally, a property owner shall be responsible for all cleanup costs and damages to the City's storm drainage system from a contractor's activities, if the contractor was hired by the owner and cannot be located.