Cal. Public Resources Code § 3324

At hearings all persons interested are entitled to be heard and present evidence, both oral and written. All such persons shall be sworn, and a transcript of the proceedings shall be kept. The procedure to be followed by the supervisor with respect to the administering of oaths, applying for subpoenas for witnesses and for the production of books, records, well logs, production records, and other documents, the taking of depositions, and the penalties attaching for failure to comply with any order of the supervisor or subpoena issued, shall be in the manner as in this division provided. On the request of the supervisor, a hearing officer in the Office of Administrative Hearings may be assigned to assist in conducting the proceedings as provided in Section 11370.3 of the Government Code. The officer, however, shall not make the determination specified in Section 3321. The provisions of Section 3234 prohibiting the giving of testimony as to the contents of records on file shall not apply to this article. All of these records shall be available and may be received in evidence in any public hearing or in any judicial proceeding herein provided for.