California Code, Streets and Highways Code - SHC § 27185

The board shall designate a bank or a savings and loan association of good standing, or both, as a depositary for district funds.  The board may also designate other banks or savings and loan associations as branch depositaries.  Any depositary and each branch depositary shall give security sufficient to secure the district against possible loss, and in the case of active deposits shall pay the warrants drawn by the auditor for demands against the district under such rules as the board may prescribe.

The board may also deposit all or part of the funds of the district in the State Treasury, and the State Treasurer shall receive any district funds sent to him for deposit and pay out said funds upon warrants of the district, under such rules as the board may prescribe.  Boards and district officials conforming to the provisions of this section are not required to conform to the provisions of Chapters 4 (commencing with Section 16500) or 4.5 (commencing with Section 16600) of Part 2, Division 4, Title 2, of the Government Code.