California Code, Health and Safety Code - HSC § 13837

(a) The district board may be elected or appointed by the county board of supervisors and the city councils in which the district is located. If the district board is to be appointed, the board of supervisors and the city council or councils shall appoint directors according to the proportionate share of population that portion of the county and each city within the district, provided that the board of superviors  1 and each city council shall appoint at least one director. The board of supervisors or city council may appoint one or more of its own members to the district board. In no case shall the number of directors exceed 11 members.

(b) Notwithstanding subdivision (a), the county board of supervisors may appoint itself as the district board, if the city council of each of the cities consents by resolution.