The petition for certification, decertification or amendment of certification of the representative of a bargaining unit must be filed either:

(1) With the Supervisor, Division of Industrial Relations, Department of Labor and Industries, General Administration Building, Olympia, Washington 98504; or

(2) If the health care activity is situated in western Washington with the Labor Mediator, Division of Industrial Relations, Department of Labor and Industries, 300 West Harrison Street, Seattle, Washington 98119; or

(3) If the health care activity is situated in eastern Washington with the Labor Mediator, Division of Industrial Relations, Department of Labor and Industries, North 1322 Post Street, Spokane, Washington 99207.