Cal. Public Utilities Code - PUC § 90830. Section 90830.
Upon receipt by the district of a copy of the agreement of annexation properly executed by the district and the city proposed to be annexed, the board shall pass a resolution declaring the city annexed to the district, and shall cause a certified copy of the resolution to be filed with the Secretary of State. From and after the date of filing of the resolution with the Secretary of State, the annexation of the city to the district is complete.