(1) The parties are free to agree on a procedure for challenging an arbitrator, subject to the provisions of subsection (3) of this section.

(2) Failing such agreement, a party who intends to challenge an arbitrator shall, within fifteen days after becoming aware of the constitution of the arbitral tribunal or after becoming aware of any circumstance referred to in RCW 7.05.130(2), send a written statement of the reasons for the challenge to the arbitral tribunal. Unless the challenged arbitrator withdraws from the arbitrator's office or the other party agrees to the challenge, the arbitral tribunal shall decide on the challenge.

(3) If a challenge under any procedure agreed upon by the parties or under the procedure of subsection (2) of this section is not successful, the challenging party may request, within thirty days after having received notice of the decision rejecting the challenge, the court specified in RCW 7.05.070 to decide on the challenge, which decision shall be subject to no appeal. While such a request is pending, the arbitral tribunal, including the challenged arbitrator, may continue the arbitral proceedings and make an award.