Does the arbitrator have the power to award Section 998 expert witness costs?

Additionally, it makes sense that only the arbitrator decides section 998 costs incurred in arbitration because an award of expert witness costs, and the amount, is discretionary under section 998. "[N]ot only is the determination as to the amount [of attorney fees and costs] properly within the purview of the arbitrator, but we observe it is the arbitrator, not the trial court, which is best situated to determine the amount of reasonable attorney fees and costs to be awarded for the conduct of the arbitration proceeding." (DiMarco v. Chaney (1995) 31 Cal.App.4th 1809, 1816-1817.)