Cal. Pub. Util. Code § 26511

Upon the completion of the annexation of any territory in accordance with law to any city included or partially included in the district, the city clerk shall file with the secretary of the district a certified copy of the ordinance, resolution or other document completing said annexation, containing a description of the territory so annexed. Unless the district within 90 days after such filing shall file with the city clerk the district’s written objections to the annexation to the district of said territory or portion thereof, such territory, or portion thereof, not objected to by the district shall, upon the termination of such period be deemed incorporated into and annexed to the district, and thereafter is subject to taxation, along with the entire territory of the district in accordance with the assessable valuation of the property thereof, for general district purposes, and for the payment of any indebtedness theretofore or thereafter incurred by the district.