On or before the 15th day of June of each year, the regional district board shall inform the board of supervisors of each county of the 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 regional 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 regional district.