The public works director, or its city engineer, will assess a surcharge rate for all nonresidential customers discharging wastes with BOD and TSS strengths greater than the average residential customer. Such customers will be assessed a surcharge sufficient to cover the cost of treating their above-normal strength wastes. Normal strength wastes are considered to be two hundred fifty (250) ppm BOD and two hundred fifty (250) ppm TSS. The surcharge rate structure for such above-normal strength waste dischargers is attached in Section 13.20.050. (Ord. 603 (part), 2004)