By letter filed with the clerk, the head of a department may designate, subject to the approval of the board of commissioners, a qualified person to exercise the powers and perform the duties of head of that department during the department head’s temporary absence or disability. During an absence or disability, the board may revoke the designation at any time and appoint another person to serve until the department head returns or his disability ceases. (1973, c. 822, s. 1.)