No person, without having authority from the city so to do, shall willfully prevent, delay, hinder, obstruct or otherwise interfere with, directly or indirectly, any contractor, workman or other person who is engaged upon any construction, repair or other project or enterprise for or on behalf of the city or willfully impede the progress of any such project or enterprise in any manner.
(Prior Code, § 529.03) Penalty, see § 134.99