No statement contained in this chapter shall be construed as prohibiting any special agreement or arrangement between the city and any person whereby an industrial waste of unusual strength or character may be admitted to the wastewater treatment works, either before or after pretreatment, provided that there is no impairment of the functioning of the wastewater treatment works by reason of the admission of such wastes, and no extra costs are incurred by the city without recompense by the person. (Ord. 586 §304, 1976)