Cal. Pub. Util. Code § 13377
Whenever a resolution authorizes the issuance of bonds pursuant to Section 13371, the board shall cause the resolution 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 referendum 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 petition meeting the requirements of this section, the resolution which is the subject thereof shall be of no effect unless and until it has been approved by the voters.
Ca. Pub. Util. Code § 13377