(a)   Where the owner or the lessee of the owner or the agent in charge of any premises within this City contracts for the improvement in any way of the same, or of the sidewalk, pavement, curbs, gutters or streets abutting thereon or adjacent thereto, such owner, lessee or agent shall observe all safety precautions which were designed to prevent nuisances dangerous to persons or property from being caused, permitted or continued.  Any owner, lessee or agent who permits the contractor or any subcontractor for the improvements, or any agent or employee of such contractor or subcontractor to cause or continue any such nuisance by noncompliance with safety precautions shall be deemed guilty of a violation thereof.
   (b)   In every case where the subcontractor, his agent or employee causes or continues any of the nuisances specified herein, the principal contractor shall be equally liable to punishment for such offense with the subcontractor, agent or employee directly causing or continuing such nuisance.
(1969 Code Sec. 903.21)