The city or its engineer, will determine the average suspended solids (SS) and biochemical oxygen demand (BOD) daily loadings for the average residential customer. The city or its engineer, will assess a surcharge rate for all nonresidential customers discharging wastes with BOD and SS strengths greater than the average residential customer. Such customers will be assessed a surcharge sufficient to cover the cost of treating such customer's above normal strength wastes. Normal strength wastes are considered to be two hundred fifty (250) ppm BOD and three hundred (300) ppm SS. The surcharge rate structure for such above normal strength waste discharges is on file in the office of the city clerk. (Ord. 219, 8-15-2000)