The wastewater volume shall be determined based on actual flow measurement. In the event that actual flow measurement is not provided, the industrial wastewater charge shall be computed using the metered water flow to the premises as a basis for water flow. Metered water flow shall include all water delivered to or used on the premises and which is discharged to the sanitary sewer system. Cooling waters or water not discharged to a sanitary sewer shall be separately metered at the user’s expense using deduct meters or any other manner approved by the WRD Manager. WRD Manager approval shall be obtained prior to allowing deduction of such flow from the total water used on the premises in computing the industrial wastewater sewer service charge. All metered water flows shall be metered at the user’s expense. Allowances may be made in accordance with the requirements of this section.