California Code, Elections Code - ELEC § 10409

When the boundaries of the territory within which an election is to be held, or the boundaries of the precincts established therefor, do not fully coincide with the boundaries of the territory within which some other election is to be held, or the boundaries of the precincts established for the other election, the elections may be consolidated as to all precincts which are the same for both elections. The elections may also be consolidated as to those precincts where a single precinct established for one election lies entirely within a single precinct established for the other election. Separate ballots shall be provided for those voters who reside outside the territory within which one of the elections is called.