California Code, Public Resources Code - PRC § 45032

(a) In the board's hearing on the appeal, the evidence before the board shall consist of the record before the hearing panel or hearing officer, relevant facts as to any actions or inactions not subject to review by a hearing panel or hearing officer, the record before the local enforcement agency, written and oral arguments submitted by the parties, and any other relevant evidence that, in the judgment of the board, should be considered to effectuate and implement the policies of this division.

(b) The board may only overturn an enforcement action, and any administrative civil penalty, by a local enforcement agency if it finds, based on substantial evidence, that the action was inconsistent with this division.  If the board overturns the decision of the local enforcement agency, the hearing panel, or the hearing officer, or finds that the enforcement agency has failed to act as required, the board may do both of the following: