1. a) No effluent shall cause an exceedance of 0.3 acute toxicity unit (TU[a]) outside a Zone of Initial Dilution (ZID) issued pursuant to 35 Ill. Adm. Code 302.102(e); except that no acute whole effluent toxicity permit limit shall be more restrictive than 1.0 TU[a] at the point of discharge.
2. b) No effluent shall cause an exceedance of 1.0 chronic toxicity unit (TU[c]) in any waters of the Lake Michigan Basin except as provided in mixing zone provisions of 35 Ill. Adm. Code 302.102 and 302.530.

35 Ill. Adm. Code 302.540 prohibits the presence of a substance or combination of substances that produces an acute or chronic aquatic life toxic condition at any applicable location within any water body of the Lake Michigan Basin. The "combination of substances" terminology includes effluent discharges. Except as provided through the mixing zone regulations of 35 Ill. Adm. Code 302.102 this toxicity standard applies at all points within the Lake Michigan Basin. The Agency shall apply the aquatic life toxicity standard to whole effluents as follows: