The director of public works may appoint a principal assistant or assistants and field supervisor or supervisors to supervise the operations of any functional subdivision of the department including but not limited to streets, water, sewer, manpower, solid waste, and public works inspection. Such principal assistants and field supervisors shall be exempt from civil service. [Ord. 8485 § 1(C), 1976; Code 1980 at § 1.70.040].