California Code, Health and Safety Code - HSC § 40272

On or before the first day of September of each year, the bay district board shall certify to the auditor of each county the total amount apportioned to the county.

Each board of supervisors shall levy an ad valorem tax on the taxable property, but not including intangible personal property, within the county, or that portion thereof, included within the bay district sufficient to secure the amount so apportioned to it. Such taxes shall be levied and collected together with, and not separately from, the taxes for county purposes and shall be paid to the treasurer of each of the counties to the credit of the bay district.