(A) The Commissioner of the Department of Streets and Public Improvements shall have authority over and charge of:
(1) All public work;
(2) The cleaning, sprinkling and repairing of streets, alleys and bridges, and, except as otherwise provided by law, the erection, making and reconstruction of all street improvements, paving, curbing, sidewalks, sewers, bridges and all public improvements and the repair thereof;
(3) All bridges; and
(4) Enforcing the provisions of this code and any ordinances relating to obstructions, encroachments, billboards, signs, trees and other shrubs upon the streets, alleys, bridges and sidewalks.
(B) In all cases where excavations in or obstructions of streets are provided for by ordinance and a permit is necessary in regard thereto, application for such permits shall be made to and such permits issued by the Commissioner.
(C) The engineer in charge and all persons who may be employed upon the streets, alleys, bridges, sidewalks, and all public works, are apportioned and assigned to the Department and shall be under the direction and supervision of the Commissioner.
('72 Code, § 3.05)