Cal. Government Code § 57109

At any time prior to the completion of the protest hearing by the commission and the adoption of a resolution ordering a reorganization that includes an incorporation and the establishment of a subsidiary district or a merger, a petition may be filed with the executive officer referring, by date of adoption, to the commission’s resolution making determinations and requesting that a separate election be called, held, and conducted only within that district on the establishment of the subsidiary district or the merger. That election shall be conducted at the same time as the election on the incorporation. Any petition so filed shall be immediately examined and certified by the executive officer by the same method and in the same manner as provided in Sections 56707 to 56711, inclusive, for the examination of petitions by the executive officer. The commission shall forward the proposal to the principal county and the principal county shall call, hold, and conduct any election upon the question of a merger or the establishment of a subsidiary district only within the district to be merged or established as a subsidiary district, if the executive officer certifies that any petition so filed was signed by either of the following: (a) In the case of a registered voter district, by not less than 10 percent of the registered voters of the district. (b) In the case of a landowner-voter district, by not less than 10 percent of the number of landowner-voters within the district who also own not less than 10 percent of the assessed value of land within the district.