Cal. Health & Safety Code § 4714.5

If the board of supervisors finds that protests have been made, prior to its final determination for formation of the district, by the owners of real property within the proposed district the assessed value of which, as shown by the last equalized assessment roll, constitutes more than one-half of the total assessed value of the real property within the proposed district, the proceeding shall terminate. The board of supervisors shall order the proceeding terminated when such protests are received.