Cal. Gov. Code § 3599.67

If, after a reasonable period of time, the employer and the recognized employee organization fail to reach an agreement, the employer and the recognized employee organization may agree upon the appointment of a mediator mutually agreeable to the parties, or either party may request the board to appoint a mediator. When both parties mutually agree upon a mediator, the costs of mediation shall be divided one-half to the employer and one-half to the recognized employee organization. If the board appoints the mediator, the costs of mediation shall be paid by the board.