Cal. Pub. Util. Code § 12815

The board may call a special election at any time for the purpose of submitting to the voters of the district the proposition as to whether or not the voters approve the addition of fluorine and fluorine compounds to the public water supply of the district. The ordinance calling an election shall fix the date on which the election shall be held, the wording of the proposition and the manner of holding the election and of voting for or against the proposition. The election shall be consolidated, in the manner provided in Section 13209, with a statewide primary or general election. The ordinance shall be published. Another election in the district on the same or substantially the same proposition shall not be called by the board, pursuant to this section or Section 12815.1, within four years after such election.