Upon an employee's separation from a full-time position to become pensioned under one of the City's pension plans, the City shall continue contributions for health and welfare benefits, at the same level to which the employee was entitled at the time of separation, for a period of five years following retirement for city employees who have ten years of credited service. The ten years of service need not be continuous; provided, however that no employee may be entitled to more than one five year period of paid health and welfare benefits.