Surcharges shall be based upon the average volume and concentration of flow discharged to the sanitary sewer, multiplied by factors expressing the costs of treating the constituents covered by the formula. The amount of total surcharge will be determined from the following formula: V x 8.34 x Fa (BOD - 300 mg/1) + V x 8.34 x Fb (SS - 300 mg/1) + V x 8.34 x Fc (TP -12 mg/1) where: V = volume of waste in millions of gallons discharged to the public sewer tributary to the treatment plants. Fa = cost per pound (in dollars) of removing BOD constituents from the wastewater, expressed to the nearest tenth of a cent. Fb = cost per pound (in dollars) of removing suspended solids from the wastewater, expressed to the nearest tenth of a cent. Fc = cost per pound (in dollars) of removing total phosphorus from the wastewater, expressed to the nearest tenth of a cent. BOD = biochemical oxygen demand. SS = suspended solids. TP = total phosphates. 300 mg/1-maximum milligrams per liter by weight of BOD and SS allowable without payment of surcharge. 12 mg/l-maximum milligrams per liter by weight of TP allowable without payment of surcharge. Until a reliable cost can be established for treating each constituent at the City treatment plants, the cost factor may be based upon the average cost of treating those constituents at other plants having like or similar processes and effluent requirements. Should it become necessary to place a surcharge on other constituents, charges will be computed in the same manner. City Code, 1976/83, art. 25, §8(b) Ord. 75-914 Ord. 84-129 Ord. 91-775