Pub. Util. Code, § 90612

If the proposition submitted at a special bond election fails to receive the requisite number of votes, the board shall not within six months after the election hold another special election for the submission of a proposition of incurring a bonded indebtedness substantially the same as the proposition voted upon at a prior election unless a petition signed by voters within the district equal in number to at least 15 percent of the total vote cast at the last general election is filed with the board, requesting that the proposition, or a proposition substantially the same, be submitted at an election to be called for that purpose.