Ill. Admin. Code tit. 35 § 406.202
In addition to the other requirements of this Part, mine discharges and non-point source mine discharges, alone or in combination with other sources, must not cause a violation of any water quality standards under 35 Ill. Adm. Code 302 or 303. If the Agency finds that a discharge that would comply with Subtitle D effluent standards would cause or is causing a violation of water quality standards, the Agency will take appropriate action under Section 31 or 39 of the Environmental Protection Act [ 415 ILCS 5 ] and require the discharge to meet effluent limits necessary to comply with the water quality standards. When a violation is caused by the cumulative effect of more than one source, several sources may be joined in an enforcement or variance proceeding, and measures for necessary effluent reductions will be determined based on technical feasibility, economic reasonableness, and fairness to all dischargers.
Ill. Admin. Code tit. 35, § 406.202
Renumbered from Section 406.105 and amended at 8 Ill. Reg. 13239, effective July 16, 1984