A. The public works director, or its city engineer, shall determine for each customer or customer class the average daily volume of wastewater discharged to the wastewater system, which shall then be divided by the average daily volume of all wastewater discharged to the wastewater system to determine such customer's volume contribution percentage. The amount used as the total average daily volume of wastewater shall exclude infiltration and inflow. The public works director, or its city engineer, shall determine for each customer or customer class the average daily poundage of five-day twenty (20) degree centigrade biochemical oxygen demand (BOD) discharged to the wastewater system which shall then be divided by the average daily poundage of all five-day BOD discharged to the wastewater system to determine such customer's BOD contribution percentage.
B. The public works director, or its city engineer, shall determine for each customer or customer class the average daily total suspended solids (TSS) poundage discharged to the wastewater system which shall then be divided by the average daily poundage of all TSS discharged to the wastewater system, to determine such customer's TSS contribution percentage. The volume contribution percentage, BOD contribution percentage and TSS contribution percentage for each customer or customer class shall be multiplied by the annual operation and maintenance costs for wastewater treatment of the total volume flow, total five-day twenty (20) degree centigrade BOD and total TSS, respectively. (Ord. 603 (part), 2004)