Section 302.100  Definitions

Unless otherwise specified, the definitions of the Environmental Protection Act (Act) [415 ILCS 5] and 35 Ill. Adm. Code 301 apply to this Part.  As used in this Part, each of the following definitions has the specified meaning.

"Acute Toxicity" means the capacity of any substance or combination of substances to cause mortality or other adverse effects in an organism resulting from a single or short-term exposure to the substance.

"Adverse Effect" means any gross or overt effect on an organism, including reversible histopathological damage, severe convulsions, irreversible functional impairment, and lethality, as well as any non-overt effect on an organism resulting in functional impairment or pathological lesions that may affect the performance of the whole organism, or that reduces an organism's ability to respond to an additional challenge.

"Chronic Toxicity" means the capacity of any substance or combination of substances to cause injurious or debilitating effects in an organism that result from exposure for a time period representing a substantial portion of the natural life cycle of that organism, including the growth phase, the reproductive phases, or such critical portions of the natural life cycle of that organism.

"Criterion" means the numerical concentration of one or more toxic substances derived in compliance with the procedures in Subpart F that, if not exceeded, would assure compliance with the narrative toxicity standard of Section 302.210.

"Early Life Stages" of fish means the pre-hatch embryonic period, the post-hatch free embryo or yolk-sac fry, and the larval period, during which the organism feeds.  Juvenile fish, which are anatomically similar to adults, are not considered to be an early life stage.

"Hardness" means a water quality parameter or characteristic consisting of the sum of calcium and magnesium concentrations expressed in terms of equivalent milligrams per liter as calcium carbonate.  Hardness is measured in compliance with methods specified in 40 CFR 136, incorporated by reference in 35 Ill. Adm. Code 301.106.

"Mixing Zone" means a portion of the waters of the State identified as a region within which mixing is allowed under Section 302.102(d).

"Thermocline" means the plane of maximum rate of decrease of temperature with respect to depth in a thermally stratified body of water.

"Total Residual Chlorine" or "TRC" means those substances that include combined and uncombined forms of both chlorine and bromine and that are expressed, by convention, as an equivalent concentration of molecular chlorine.  TRC is measured in compliance with methods specified in 40 CFR 136, incorporated by reference in 35 Ill. Adm. Code 301.106.

"Toxic Substance" means a chemical substance that causes adverse effects in humans, or in aquatic or terrestrial animal or plant life.  Toxic substances include those substances listed in 40 CFR 302.4, incorporated by reference in 35 Ill. Adm. Code 301.106, or any "chemical substance" as defined by the Illinois Chemical Safety Act [430 ILCS 45]

"ZID" or "Zone of Initial Dilution" means a portion of a mixing zone, identified pursuant to Section 302.102(e), within which acute toxicity standards need not be met.

(Source:  Amended at 47 Ill. Reg. 4437, effective March 23, 2023)