California Code, Public Utilities Code - PUC § 120051.6

(a) The County of San Diego Board of Supervisors shall appoint a county supervisor, not already appointed under Section 120051, who represents one of the two supervisorial districts with the greatest percentage of its area within the incorporated area of the County of San Diego within the area under the jurisdiction of the transit development board as defined in Section 120054, to serve as an alternate member of the transit development board.

(b) The city councils of the cities specified in subdivision (b) or(c) of Section 120050.2 shall each individually appoint a member of their respective city councils not already appointed pursuant to subdivision (b) or (c) of Section 120050.2 to serve as an alternate member of the transit development board for each member of the city on the board.

(c) At its discretion, a city council or the county board of supervisors may appoint a second alternate member, in the same manner as first alternates are appointed, to serve on the board in the event that neither a member nor the alternate member is able to attend a meeting of the board.

(d) An alternate member and second alternate member shall be subject to the same restrictions and shall have the same powers, when serving on the board, as a member.