If, before the conclusion of the hearing, a petition signed by not less than 15 percent of the owners or by not less than 15 percent of the registered voters in the specified area is filed with the governing body requesting that body to submit the proposition of acquiring or constructing the proposed works to an election of the registered voters in the area, the governing body shall forthwith call an election in the area for that purpose.
Ca. Health and Saf. Code § 4975