California Code, Public Utilities Code - PUC § 100617

When the board has imposed a special benefit assessment, the secretary shall so certify to the assessor of the county in which the territory of any benefit district is located and deliver to the assessor copies of all maps and diagrams of the benefit district and zones, if any, therein, indicating the amount of the special benefit assessment to be levied within the benefit district and zones, if any, therein.

Special benefit assessments authorized by this chapter shall be levied and collected by the county at the same time and in the same manner as taxes are levied and collected.  The county may deduct its reasonable expenses of collection and shall transmit the balance of the assessments to the authority.