Section 309.143  Effluent Limitations

a)         Effluent limitations must control all pollutant or pollutant parameters (conventional, nonconventional, or toxic pollutants) that the Agency determines are, or may be, discharged at a level that will cause, have the reasonable potential to cause, or contribute to an excursion above any State water quality standard, including State narrative criteria for water quality. When determining whether a discharge causes, has the reasonable potential to cause, or contributes to an in-stream excursion above a narrative or numeric criteria within a State water quality standard, the Agency must use procedures that account for existing controls on point and nonpoint sources of pollution, the variability of the pollutant or pollutant parameter in the effluent, the sensitivity of the species to toxicity testing (when evaluating whole effluent toxicity), and, when appropriate, the dilution of the effluent in the receiving water.

b)         In the application of effluent standards and limitations, water quality standards, and other applicable requirements, the Agency must, for each permit, specify average and maximum daily quantitative limitations for the level of pollutants in the authorized discharge in terms of weight (except pH, temperature, radiation, and any other pollutants not appropriately expressed by weight, and except for discharges whose constituents cannot be appropriately expressed by weight).  The Agency may, in its discretion, in addition to specifying daily quantitative limitations by weight, specify other limitations, such as average or maximum concentration limits, for the level of pollutants in the authorized discharge.  Effluent limitations for multiproduct operations must provide for appropriate waste variations from such plants.  When a schedule of compliance is included as a condition in a permit, effluent limitations must be included for the interim period as well as for the period following the final compliance date.

(Source:  Amended at 47 Ill. Reg. 5017, effective March 23, 2023)