California Code, Public Resources Code - PRC § 30304

(a) Any member of the commission may, subject to the confirmation of the member's appointing power, appoint an alternate member to represent the member at any commission meeting.  An alternate for a locally elected official need not also be a locally elected official.  An alternate may serve before confirmation for a period not to exceed 90 days from the date of appointment unless and until confirmation is specifically refused.  The alternate shall serve at the pleasure of the member who appointed them and shall have all the powers and duties as a member of the commission, except that the alternate shall only participate and vote in meetings in the absence of the member who appointed them.

(b) All provisions of law relating to conflicts of interest that are applicable to a member shall apply to an alternate member.  Whenever a member has, or is known to have, a conflict of interest on any matter, the member's alternate is not eligible to vote on that matter.