Time Limitation and Waiver Grievances shall not be valid for consideration unless the grievance is submitted in writing to the School District’s designee, setting forth the facts and specific provision(s) of the Agreement allegedly violated and the particular relief sought, within twenty (20) days after the event giving rise to the grievance occurred. Failure to file any grievance within such period shall be deemed a waiver thereof. Failure to appeal a grievance from one level to another within the time periods hereafter provided shall constitute a waiver of the grievance. An effort shall first be made to adjust an alleged grievance informally between the employee and the School District’s designee. By written mutual agreement, the parties may waive any step and/or extend any time limits of the grievance procedure.