Building contractors, excavators and other persons who in the course of their respective businesses cause debris or refuse of any kind to accumulate at any place within the City shall remove and dispose of such debris or refuse periodically before it becomes a hazard to the public health, safety or welfare, and at the completion of each project shall remove all such debris and refuse and dispose thereof in a sanitary and lawful manner; provided, that when debris or refuse accumulates on any vacant lot so regarding becomes a nuisance and is not subject to removal by any contractor or other person as above provided, the City may collect and dispose of such debris and refuse and the costs of such collection and disposal shall become a charge against the owner of such vacant lot and a lien thereon and shall be collectable in the same manner as taxes.