Under the direction of the mayor, the director of public safety shall be the executive head of the police and fire departments and the chief administrative authority of the charity, correction, and building departments. He shall have all powers and duties connected with and incident to the appointment, regulation, and government of such departments except as otherwise provided by law. He shall keep a record of his proceedings, a copy of which, certified by him, shall be competent evidence in all courts.
Such director shall make all contracts in the name of the city with reference to the management of such departments, for the erection or repair of all buildings or improvements in connection therewith, and for the purchase of all supplies necessary for such departments.