A salary differential of $42.50 biweekly shall be paid incumbents or positions requiring bilingual proficiency as designated by the appointing authority and HRD Director.  Said differen­tial shall be prorated for employees working less than full‑time or who are in an unpaid leave of absence status for a portion of any given pay period.  Designation of positions for which bilingual profi­ciency is required is the sole prerogative of the County and the decision of the HRD Director is final.  The Union shall be notified when such designations are made.