California Code, Public Resources Code - PRC § 3765

(a) Within 30 days after the close of a hearing conducted by the director, the director shall issue a written decision affirming, setting aside, or modifying the order from which the appeal was taken. The director's written decision shall be based upon the preponderance of the evidence and shall set forth the director's factual findings, legal conclusions, and rationale for the result. The director may extend the 30-day period for issuing the written decision if the extension is agreed to by the operator.

(b) The director shall file the written decision with the supervisor and serve it on the operator as soon as the decision is complete, at which time the decision shall be deemed final. The director's decision shall supersede the order of the supervisor from which the appeal was made. If the director affirms or modifies the order, the director shall retain jurisdiction until the operator completes the work required to be performed by the order.