Cal. Sts. & High. Code § 26080

The commission shall consist of the chairman of the board of supervisors and the county surveyor, or the county engineer, as the case may be, of the county in which the district is situated, who shall be ex officio members, and a third member elected pursuant to Chapter 4 of this part. The elected member shall have been a bona fide resident and freeholder within the boundaries of the district for at least one year prior to his election.