100.1.1. The arbitrator shall proceed with the arbitration with assessors if, within fifteen days of his appointment, there is agreement to that effect between the parties.
Where there is agreement, each party shall designate, within the time prescribed in the first paragraph, an assessor to assist the arbitrator and represent it during the hearing of the grievance and the deliberation. If a party refuses to give effect to the agreement within the prescribed time, the arbitrator may proceed in the absence of that party’s assessor.
He may proceed in the absence of an assessor who does not attend, after having been duly convened.