California Code, Streets and Highways Code - SHC § 8671

The treasurer or designated paying agent shall keep a redemption fund designated by the name of the bonds, in which there shall be placed all sums received from the collection of the assessments made.  The fund shall be considered a trust fund for the benefit of the bondholders.  The redemption fund shall be used for paying principal and interest and redemption premium, if any, payments on the bonds directly, or money in the fund may be forwarded to the paying agent for these purposes.  Under no circumstances shall the bonds or the interest thereon be paid out of any other fund.