The Director of City Services shall have charge of all public improvements and public grounds in the city, and shall supervise the construction and repair of all such public improvements therein, but no improve-ments shall be made by him, without the previous order of the City Council, except in cases of emergency and immediate necessity to protect the city's interests. He shall without delay, cause all breaks in any street, alley, catch basins, street drains, sidewalk crossing, bridge, culvert, apron or other unsafe place, to be properly repaired and report the cost thereof to the City Council for allowance; but when the probable cost of any such repairs shall exceed $500, the same shall be made only with the concurrence of the Mayor and the City Council.
(`79 Code, § 31.315)