Cal. Elections Code § 4108

(a) Notwithstanding any other law and regardless of the number of eligible voters within its boundaries a district may, by resolution of its governing board, conduct any election by all-mailed ballots pursuant to Division 4 (commencing with Section 4000). (b) (1) A district conducting an election by all-mailed ballots may consolidate its election with the election of one or more other legislative or congressional districts, public districts, cities, counties, or other political subdivisions if all of the elections to be consolidated will be: (A) Held on the same day. (B) Held in the same territory or in a territory that is in part the same. (C) Conducted wholly by mail. (2) A district consolidating its election pursuant to subdivision (a) shall order the consolidation pursuant to Section 10400. (3) A district election that is consolidated with an all-mailed ballot election for a legislative or congressional district shall also comply with any additional statutory requirements that apply to the all-mailed ballot election for that legislative or congressional district. (c) An election conducted pursuant to this section shall be held on a date prescribed in Section 1500 or on any other date other than an established election date.