Cal. Pub. Util. Code § 13104
Upon any such resolution taking effect subject to the right of referendum, pursuant to this article, the board shall cause the same to be published in the manner provided for the publication of notices. At any time within 60 days after the date of the second such publication a referendary petition, signed by voters in number equal to at least 3 percent of the total vote cast, as defined in Section 11507, demanding the submission of such resolution to a vote of the voters of the district for their assent to the issuance of the proposed bonds, may be filed with the secretary. Upon presentation to the secretary of a referendary petition, the resolution which is the subject thereof shall be of no effect unless and until it has been assented to by the voters.
Ca. Pub. Util. Code § 13104