Cal. Streets and Highways Code § 5830

The board of supervisors shall thereafter, in each year, prior to the time of fixing the county tax rate, estimate the cost of maintaining and operating the improvements to be maintained and operated within the maintenance district during the ensuing year. The board of supervisors shall decide whether or not the cost of maintaining and operating the improvement shall be borne wholly or partially by the maintenance district and shall, in addition to all other taxes, fix a special tax rate for the real property within the maintenance district, or for lighting purposes levy an assessment on each parcel of real property within the maintenance district on the basis of the estimated benefit to the parcel, sufficient to raise an amount of money to cover the expense of maintaining the improvements during the ensuing year, or such portion of the amount as the board of supervisors shall determine shall be borne by the maintenance district, and the board of supervisors shall levy a special assessment tax or, for lighting purposes, an assessment each year upon the real property in the maintenance district sufficient to pay such expense, or the portion thereof, which shall be paid by the maintenance district.