ORS 36.635: Initiation of arbitration.

(1) A person initiates an arbitration proceeding by giving notice in a record to the other parties to the agreement to arbitrate in the agreed manner between the parties or, in the absence of agreement, by certified mail, return receipt requested and obtained, or by service as authorized for summons under ORCP 7 D. The notice must describe the nature of the controversy and the remedy sought.

      (2) Unless a person objects for lack or insufficiency of notice under ORS 36.665 (3) not later than the beginning of the arbitration hearing, the person by appearing at the hearing waives any objection to lack or insufficiency of notice.