The heads of the administrative departments under the City Manager shall be directly responsible to the City Manager for the efficient administration of their respective departments. The City Manager may designate acting department heads, subject to the approval of the Council, when necessary to assure the continuity of the City's business. The City Manager shall have the power, with the approval of the Council, to employ expert consultants to perform work or give advice connected with the departments of the city when the City Manager finds such work or advice necessary.